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In ], a '''supergravity theory''' is a ] combining ] and ]. {{Short description|Modern theory of gravitation that combines supersymmetry and general relativity}}
{{Multiple issues|
{{technical|date=April 2018}}
{{more footnotes needed|date=December 2009}}
}}


{{Beyond the Standard Model|expanded=]}}
Like any field theory of gravity, a supergravity theory contains a spin-2 field whose quantum is the ]. Supersymmetry requires the graviton field to have a ]. This field has spin 3/2 and its quantum is the ]. The number of gravitino fields is equal to the number of supersymmetries. Supergravity theories are often said to be the only consistent theories of interacting massless spin 3/2 fields.
{{string theory}}
In ], '''supergravity''' ('''supergravity theory'''; '''SUGRA''' for short) is a modern ] that combines the principles of ] and ]; this is in contrast to non-gravitational supersymmetric theories such as the ]. Supergravity is the ] of local supersymmetry. Since the supersymmetry (SUSY) generators form together with the ] a ], called the ], supersymmetry as a gauge theory makes gravity arise in a natural way.<ref name="Niewwenhuizen">{{Cite journal|doi=10.1016/0370-1573(81)90157-5|title=Supergravity|year=1981|last1=Van Nieuwenhuizen|first1=P.|journal=Physics Reports|volume=68|issue=4|pages=189–398|bibcode=1981PhR....68..189V}}</ref>

==Gravitons==

Like all covariant approaches to quantum gravity,<ref>{{Cite arXiv |last=Rovelli |first=Carlo |date=2000 |title=Notes for a brief history of quantum gravity |eprint=gr-qc/0006061 }}</ref> supergravity contains a spin-2 field whose quantum is the ]. Supersymmetry requires the graviton field to have a ]. This field has ] 3/2 and its quantum is the ]. The number of gravitino fields is equal to the number of supersymmetries.


==History== ==History==


===Four Dimensional SUGRA=== ===Gauge supersymmetry===
The first theory of local supersymmetry was proposed by ] and ] in 1975<ref name="NathArnowitt">{{cite journal | last1 = Nath | first1 = P. | last2 = Arnowitt | first2 = R. | year = 1975 | title = Generalized Super-Gauge Symmetry as a New Framework for Unified Gauge Theories | journal = Physics Letters B | volume = 56 | issue = 2| page = 177 | doi=10.1016/0370-2693(75)90297-x| bibcode = 1975PhLB...56..177N }}</ref> and was called '''gauge supersymmetry'''.


===Supergravity===
Supergravity, also called SUGRA, was initially proposed as a four-dimensional theory in ], but was quickly generalized to many different theories in various numbers of dimensions. Some supergravity theories were shown to be equivalent to certain higher-dimensional supergravity theories via ]. The resulting theories were sometimes referred to as ], as Kaluza and Klein constructed, nearly a century ago, a five-dimensional gravitational theory which reduces to four-dimensional electromagnetism when the fifth dimension is a circle.
The first model of 4-dimensional supergravity (without this denotation) was formulated by Dmitri Vasilievich Volkov and Vyacheslav A. Soroka in 1973,<ref name ="Volkov Soroka">{{cite journal | last1 = Volkov | first1 = D.V. | last2 = Soroka | first2 = V.A. | year = 1973 | title = Higgs effect for Goldstone particles with spin 1/2 | journal = JETP Letters | volume = 16 | issue = 11| pages = 438–440 | doi=10.1007/BFb0105271 | bibcode = 1973JETPL..18..312V }}</ref> emphasizing the importance of spontaneous supersymmetry breaking for the possibility of a realistic model. The ] (with unbroken local supersymmetry) was constructed in detail in 1976 by ], ] and ].<ref name="Summary">{{cite journal | last1 = Freedman | first1 = D.Z. | last2 = van Nieuwenhuizen | first2 = P. | last3 = Ferrara | first3 = S. | year = 1976 | title = Progress Toward A Theory Of Supergravity | journal = Physical Review D| volume = 13| issue = 12| pages = 3214–3218 | doi=10.1103/physrevd.13.3214| bibcode = 1976PhRvD..13.3214F }}</ref> In 2019 the three were awarded a special ] for the discovery.<ref>{{Cite news|url=https://www.cbc.ca/news/technology/supergravity-breakthrough-prize-1.5237900|title=Supergravity scientists share $3M US Breakthrough Prize|work=CBC News}}</ref> The key issue of whether or not the spin 3/2 field is consistently coupled was resolved in the nearly simultaneous paper, by ] and ],<ref name="DeserZumino">{{cite journal | last1 = Deser | first1 = S. | last2 = Zumino | first2 = B. | year = 1976 | title = Consistent Supergravity | url = https://cds.cern.ch/record/438874| journal = Physics Letters B| volume = 62| issue = 3| pages = 335–337 | doi=10.1016/0370-2693(76)90089-7| bibcode = 1976PhLB...62..335D}}</ref> which independently proposed the minimal 4-dimensional model. It was quickly generalized to many different theories in various numbers of ] and involving additional (N) supersymmetries. Supergravity theories with N>1 are usually referred to as extended supergravity (SUEGRA). Some supergravity theories were shown to be related to certain ] supergravity theories via ] (e.g. N=1, 11-dimensional supergravity is dimensionally reduced on T<sup>7</sup> to 4-dimensional, ungauged, ''N'' = 8 supergravity). The resulting theories were sometimes referred to as ] as Kaluza and Klein constructed in 1919 a 5-dimensional gravitational theory, that when dimensionally reduced on a circle, its 4-dimensional non-massive modes describe ] coupled to ].


===11d: The Maximal SUGRA=== ===mSUGRA===
mSUGRA means minimal SUper GRAvity. The construction of a realistic model of particle interactions within the ''N'' = 1 supergravity framework where supersymmetry (SUSY) breaks by a super ] carried out by ], ] and ] in 1982. Collectively now known as minimal supergravity Grand Unification Theories (mSUGRA GUT), gravity mediates the breaking of SUSY through the existence of a ]. mSUGRA naturally generates the Soft SUSY breaking terms which are a consequence of the Super Higgs effect. Radiative breaking of electroweak symmetry through ] Group Equations (RGEs) follows as an immediate consequence.
Due to its predictive power, requiring only four input parameters and a sign to determine the low energy phenomenology from the scale of Grand Unification, its interest is a widely investigated model of ]
{{See also|Minimal_Supersymmetric_Standard_Model#Gravity-mediated_supersymmetry_breaking|label 1=Gravity-Mediated Supersymmetry Breaking in the MSSM}}


===11D: the maximal SUGRA===
{{Main|Eleven-dimensional supergravity}}
One of these supergravities, the 11-dimensional theory, generated considerable excitement as the first potential candidate for the ]. This excitement was built on four pillars, two of which have now been largely discredited: One of these supergravities, the 11-dimensional theory, generated considerable excitement as the first potential candidate for the ]. This excitement was built on four pillars, two of which have now been largely discredited:


* ] showed that 11 dimensions was the largest number of dimensions consistent with a single graviton, and that a theory with more dimensions would also have particles with spins greater than 2. These problems are avoided in 12 dimensions if two of these dimensions are timelike, as has been often emphasized by ]. * ] showed<ref>{{cite journal | last1 = Nahm | first1 = Werner | year = 1978| title = Supersymmetries and their representations | url = https://cds.cern.ch/record/132743| journal = Nuclear Physics B | volume = 135 | issue = 1| pages = 149–166 | doi = 10.1016/0550-3213(78)90218-3 | bibcode = 1978NuPhB.135..149N}}</ref> 11 dimensions as the largest number of dimensions consistent with a single graviton, and more dimensions will show particles with spins greater than 2. However, if two of these dimensions are time-like, these problems are avoided in 12 dimensions. ]{{Citation needed|date=March 2007}} gives this emphasis.
* In 1981 ] showed<ref>{{cite journal | last1 = Witten | first1 = Ed | year = 1981| title = Search for a realistic Kaluza-Klein theory | journal = Nuclear Physics B | volume = 186 | issue = 3| pages = 412–428 | doi = 10.1016/0550-3213(81)90021-3 | bibcode = 1981NuPhB.186..412W}}</ref> 11 as the smallest number of dimensions big enough to contain the ]s of the ], namely ] for the ] and ] times ] for the ] interactions.{{citation needed|date=March 2013}} Many techniques exist to embed the standard model gauge group in supergravity in any number of dimensions like the obligatory gauge symmetry in ] and ], and obtained in ] by ] on certain ]s. The ]s engineer gauge symmetries too.
* In 1978 ], ] and ] (CJS) found<ref>E. Cremmer, B. Julia and J. Scherk, "Supergravity theory in eleven dimensions", ''Physics Letters'' '''B76''' (1978)
pp 409-412,</ref> the classical action for an 11-dimensional supergravity theory. This remains today the only known classical 11-dimensional theory with local supersymmetry and no fields of spin higher than two.{{Citation needed|date=March 2007}} Other 11-dimensional theories known and quantum-mechanically inequivalent reduce to the CJS theory when one imposes the classical equations of motion. However, in the mid-1980s ] and ] found an alternate theory in D=11 Supergravity with Local SU(8) Invariance. While not manifestly Lorentz-invariant, it is in many ways superior, because it dimensionally-reduces to the 4-dimensional theory without recourse to the classical equations of motion.


* In 1980 ] and ] showed that compactification from 11 dimensions preserving all the SUSY generators could occur in two ways, leaving only 4 or 7 macroscopic dimensions, the others compact.<ref>{{Cite journal
* Shortly afterwards, ] showed that 11 was the smallest number of dimensions that was big enough to contain the ]s of the ], namely ] for the ] and ] times ] for the ] interactions. Today many techniques exist to embed the standard model gauge group in supergravity in any number of dimensions. For example, in the mid and late 1980s one often used the obligatory gauge symmetry in ] and ]. In ] they could also be obtained by ] on certain ]'s. Today one may also use ]s to engineer gauge symmetries.
|author=Peter G.O. Freund
|author2=Mark A. Rubin
|date=1980
|title=Dynamics of dimensional reduction
|journal=Physics Letters B
|volume=97
|pages=233–235
|doi=10.1016/0370-2693(80)90590-0
|issue=2
|bibcode = 1980PhLB...97..233F }}</ref> The noncompact dimensions have to form an ]. There are many possible compactifications, but the ]'s invariance under all of the supersymmetry transformations preserves the action.


Finally, the first two results each appeared to establish 11 dimensions, the third result appeared to specify the theory, and the last result explained why the observed universe appears to be four-dimensional.
* In ], ], ] and ] (CJS) of the ] found the classical action for an 11-dimensional supergravity theory. This remains today the only known classical 11-dimensional theory with local ] and no fields of spin higher than two. Quantum-mechanically, inequivalent 11-dimensional theories are known which reduce to the CJS theory in the classical limit, that is when one imposes the classical equations of motion. For example, in the mid 1980s ] and ] found an alternate theory in . This theory, while not manifestly Lorentz-invariant, is in many ways superior to the CJS theory in that, for example, it dimensionally-reduces to the 4-dimensional theory without recourse to the classical equations of motion.

* In ], ] and ] showed that ] from 11 dimensions preserving all the SUSY generators could occur in two ways, leaving only 4 or 7 macroscopic dimensions (the other 7 or 4 being compact). Unfortunately, the noncompact dimensions have to form an ]. Today it is understood that there are many possible compactifications, but that the ]s are invariant under all of the ] transformations that preserve the action.

Thus, the first two results appeared to establish 11 dimensions uniquely, the third result appeared to specify the theory, and the last result explained why the observed universe appears to be four-dimensional.


Many of the details of the theory were fleshed out by ], ] and ]. Many of the details of the theory were fleshed out by ], ] and ].


===The End of the SUGRA Era=== ===The end of the SUGRA era===
The initial excitement over 11-dimensional supergravity soon waned, as various failings were discovered, and attempts to repair the model failed as well. Problems included:{{Citation needed|date=May 2016}}


* The compact manifolds which were known at the time and which contained the standard model were not compatible with supersymmetry, and could not hold ]s or ]s. One suggestion was to replace the compact dimensions with the 7-sphere, with the symmetry group ], or the squashed 7-sphere, with symmetry group ] times ].
The initial excitement over 11-dimensional supergravity soon waned, as various failings were discovered, and attempts to repair the model failed as well. Problems included:
* Until recently, the physical ]s seen in experiments were believed to be massless, and appeared to be left-handed, a phenomenon referred to as the ] of the Standard Model. It was very difficult to construct a chiral fermion from a compactification — the compactified manifold needed to have singularities, but physics near singularities did not begin to be understood until the advent of ] ] in the late 1980s.
* Supergravity models generically result in an unrealistically large ] in four dimensions, and that constant is difficult to remove, and so require ]. This is still a problem today.
* Quantization of the theory led to quantum field theory ] rendering the theory inconsistent. In the intervening years physicists have learned how to cancel these anomalies.


Some of these difficulties could be avoided by moving to a 10-dimensional theory involving ]s. However, by moving to 10 dimensions one loses the sense of uniqueness of the 11-dimensional theory.<ref>{{cite arXiv |eprint=hep-th/9805177|last1=Duff|first1=M. J.|title=A Layman's Guide to M-theory|year=1998}}</ref>
* The compact manifolds which were known at the time and which contained the standard model were not compatible with supersymmetry, and could not hold ]s or ]s. One suggestion was to replace the compact dimensions with the 7-sphere, with the symmetry group ], or the squashed 7-sphere, with symmetry group ] times ].


The core breakthrough for the 10-dimensional theory, known as the ], was a demonstration by ], ] and ] that there are only three supergravity models in 10 dimensions which have gauge symmetries and in which all of the gauge and ] cancel. These were theories built on the groups ] and <math>E_8 \times E_8</math>, the ] of two copies of ]. Today we know that, using ] for example, gauge symmetries can be introduced in other 10-dimensional theories as well.<ref name="Blumen">
* Until recently, the physical ]s seen in the real world were believed to be massless, and appeared to be left-handed, a phenomenon referred to as the ] of the Standard Model. It was very difficult to construct a chiral fermion from a ] &mdash; the compactified manifold needed to have singularities, but physics near singularities did not begin to be understood until the advent of ] ] in the late 1980s.
{{cite journal
|date=2005
|title=Toward Realistic Intersecting D-Brane Models
|arxiv=hep-th/0502005
|last1=Blumenhagen| first1=R.
|last2=Cvetic| first2=M.|author2-link= Mirjam Cvetič
|last3=Langacker | first3=P.
|last4=Shiu| first4=G. | doi=10.1146/annurev.nucl.55.090704.151541 | doi-access=free | volume=55 | issue=1 | journal=] | pages=71–139
|bibcode=2005ARNPS..55...71B|s2cid=15148429
}}</ref>


===The second superstring revolution===
* Supergravity models generically result in an unrealistically large ] in four dimensions, and that constant is difficult to remove, and so require ]. This is still a problem today.
Initial excitement about the 10-dimensional theories, and the string theories that provide their quantum completion, died by the end of the 1980s. There were too many ]s to compactify on, many more than ] had estimated, as he admitted in December 2005 at the ]. None quite gave the standard model, but it seemed as though one could get close with enough effort in many distinct ways. Plus no one understood the theory beyond the regime of applicability of string ].


There was a comparatively quiet period at the beginning of the 1990s; however, several important tools were developed. For example, it became apparent that the various superstring theories were related by "]", some of which relate weak string-coupling - perturbative - physics in one model with strong string-coupling - non-perturbative - in another.
* Quantization of the theory led to quantum field theory ] rendering the theory inconsistent. In the intervening years we have learned how to cancel these anomalies.


Then the ] occurred. ] realized that obscure string theory objects, called ], which he discovered six years earlier, equate to stringy versions of the ] known in supergravity theories. String theory perturbation didn't restrict these ]. Thanks to supersymmetry, p-branes in supergravity gained understanding well beyond the limits of string theory.
Some of these difficulties could be avoided by moving to a 10-dimensional theory involving ]s. However, by moving to 10 dimensions one loses the sense of uniqueness of the 11-dimensional theory.


Armed with this new ] tool, ] and many others could show all of the perturbative string theories as descriptions of different states in a single theory that Witten named ]. Furthermore, he argued that M-theory's ], i.e. when the quantum wavelength associated to objects in the theory appear much larger than the size of the 11th dimension, needs 11-dimensional supergravity descriptors that fell out of favor with the ] 10 years earlier, accompanied by the 2- and 5-branes.
The core breakthrough for the 10-dimensional theory, known as the ], was a demonstration by ], ] and ] that there are only three supergravity models in 10 dimensions which have gauge symmetries and in which all of the anomalies cancel. These were theories built on the groups ] and <math>E_8 \times E_8</math>, the ] of two copies of ]. Today we know that, using ] for example, gauge symmetries can be introduced in other 10-dimensional theories as well.


Therefore, supergravity comes full circle and uses a common framework in understanding features of string theories, M-theory, and their compactifications to lower spacetime dimensions.
===The Second Superstring Revolution===


==Relation to superstrings==
Initial excitement about the 10d theories, and the string theories that provide their quantum completion, died by the end of the 1980s. There were too many ]s to ] on, many more than ] had estimated, as he admitted in ] ] at the ]. None quite gave the standard model, but it seemed as though one could get close with enough effort in many distinct ways. Plus no one understood the theory beyond the regime of applicability of string ].
The term "low energy limits" labels some 10-dimensional supergravity theories. These arise as the massless, ]-level approximation of string theories. True ] of string theories, rather than truncations, are rarely available. Due to string dualities, the conjectured 11-dimensional M-theory is required to have 11-dimensional supergravity as a "low energy limit". However, this doesn't necessarily mean that string theory/M-theory is the only possible ] of supergravity;{{Citation needed|date=March 2007}} supergravity research is useful independent of those relations.


== 4D ''N'' = 1 SUGRA ==
There was a long, slow period at the beginning of the 1990s as the field faded into obscurity. During this time, several important tools were developed. For example, it was understood that a web of dualities connects the various perturbative string theories in various regimes.
{{Main|1=4D N = 1 supergravity}}
Before we move on to SUGRA proper, let's recapitulate some important details about general relativity. We have a 4D differentiable manifold M with a Spin(3,1) principal bundle over it. This principal bundle represents the local Lorentz symmetry. In addition, we have a vector bundle T over the manifold with the fiber having four real dimensions and transforming as a vector under Spin(3,1).
We have an invertible linear map from the tangent bundle TM{{which|date=February 2021}} to T. This map is the ]. The local Lorentz symmetry has a ] associated with it, the ].


The following discussion will be in superspace notation, as opposed to the component notation, which isn't manifestly covariant under SUSY. There are actually ''many'' different versions of SUGRA out there which are inequivalent in the sense that their actions and constraints upon the torsion tensor are different, but ultimately equivalent in that we can always perform a field redefinition of the supervierbeins and spin connection to get from one version to another.
Then it all changed, in what is known as the ]. ] realized that obscure string theory objects, called ], which he had discovered six years earlier, are in fact the ] in 10-dimensional supergravity theories. The treatment of these ] was not restricted by string perturbation theory; in fact, thanks to ], p-branes in supergravity were understood well beyond the limits in which string theory was understood.


In 4D N=1 SUGRA, we have a 4|4 real differentiable supermanifold M, i.e. we have 4 real bosonic dimensions and 4 real fermionic dimensions. As in the nonsupersymmetric case, we have a Spin(3,1) principal bundle over M. We have an '''R'''<sup>4|4</sup> vector bundle T over M. The fiber of T transforms under the local Lorentz group as follows; the four real bosonic dimensions transform as a vector and the four real fermionic dimensions transform as a ]. This Majorana spinor can be reexpressed as a complex left-handed Weyl spinor and its complex conjugate right-handed ] (they're not independent of each other). We also have a spin connection as before.
Armed with this new ] tool, ] and many others were able to show that all of the perturbative string theories were descriptions of different states in a single theory which he named ]. Furthermore he argued that the classical limit of most states in this theory are described by the 11-dimensional supergravity that had fallen out of favor with the ] 10 years earlier.


We will use the following conventions; the spatial (both bosonic and fermionic) indices will be indicated by M, N, ... . The bosonic spatial indices will be indicated by μ, ν, ..., the left-handed Weyl spatial indices by α, β,..., and the right-handed Weyl spatial indices by <math>\dot{\alpha}</math>, <math>\dot{\beta}</math>, ... . The indices for the fiber of T will follow a similar notation, except that they will be hatted like this: <math>\hat{M},\hat{\alpha}</math>. See ] for more details. <math>M = (\mu,\alpha,\dot{\alpha})</math>. The supervierbein is denoted by <math>e^{\hat{M}}_N</math>, and the spin connection by <math>\omega_{\hat{M}\hat{N}P}</math>. The ''inverse'' supervierbein is denoted by <math>E^N_{\hat{M}}</math>.
Nowadays, in the post ] era, once again many more people work with the 10d supergravities than with the 11d theory, as a practical formulation of M-theory in an arbitrary background space-time has never been found. The four-dimensional theory has remained consistently popular among a large sector of the world's ], who outnumber string theorists.


The supervierbein and spin connection are real in the sense that they satisfy the reality conditions
==Relation to ]s==
:<math>e^{\hat{M}}_N (x,\overline{\theta},\theta)^* = e^{\hat{M}^*}_{N^*}(x,\theta,\overline{\theta})</math> where <math>\mu^*=\mu</math>, <math>\alpha^*=\dot{\alpha}</math>, and <math>\dot{\alpha}^*=\alpha</math> and <math>\omega(x,\overline{\theta},\theta)^*=\omega(x,\theta,\overline{\theta})</math>.


The ] is defined as
Many, if not all supergravity theories are the classical limits of ] (i.e., the limit in which the string is approximated as having zero length, and treated as a dimensionless point-particle), with the exception of "maximal" 11-dimensional supergravity, which is, by definition, a classical limit of ]. M-theory has no strings, but has a membrane, so intuitively one may think of the supergravity limit as a limit in which the membrane size shrinks to zero. However, this doesn't necessarily mean that string theory/M-theory is the only possible ] of supergravity and supergravity is often studied even by people who are not string theorists.
:<math>D_\hat{M}f=E^N_{\hat{M}}\left( \partial_N f + \omega_N \right)</math>.


The ] as defined over supermanifolds needs to be super graded. This means that every time we interchange two fermionic indices, we pick up a +1 sign factor, instead of -1.
==Nomenclature==


The presence or absence of ] is optional, but if R-symmetry exists, the integrand over the full superspace has to have an R-charge of 0 and the integrand over chiral superspace has to have an R-charge of 2.
===Supermultiplets===
A representation of the super-Poincaré group is called a ], and the one which contains a graviton is called the ]. Supergravity theories by definition are supersymmetric, which means in particular that all fields must transform under some representation of the super-Poincaré group. Thus fields in supergravity theories come in supermultiplets, and the particle content of a particular supergravity theory is the collection of supermultiplets that is present. When a supergravity theory contains a supermultiplet which contains a field that transforms as a vector under the super-Poincaré group, the theory is said to be a ].


A chiral superfield ''X'' is a superfield which satisfies <math>\overline{D}_{\hat{\dot{\alpha}}}X=0</math>. In order for this constraint to be consistent, we require the integrability conditions that <math>\left\{ \overline{D}_{\hat{\dot{\alpha}}}, \overline{D}_{\hat{\dot{\beta}}} \right\} = c_{\hat{\dot{\alpha}}\hat{\dot{\beta}}}^{\hat{\dot{\gamma}}} \overline{D}_{\hat{\dot{\gamma}}}</math> for some coefficients ''c''.
The name of a supergravity theory generally includes the number of dimensions of ] that it inhabits, and also the number <math>\mathcal{N}</math> of ] that it has. Sometimes one also includes the choices of supermultiplets in the name of theory. For example, an <math>\mathcal {N}=2</math>, (9+1)-dimensional supergravity enjoys 9 spatial dimensions, one time and 2 gravitinos. While the field content of different supergravity theories varies considerably, all supergravity theories contain at least one gravitino and they all contain a single ]. Thus every supergravity theory contains a single supergravity supermultiplet. It is still not known whether one can construct theories with multiple gravitons that are not equivalent to multiple decoupled theories with a single graviton in each. ] theories, which will be defined below, may only contain the supergravity supermultiplet.


Unlike nonSUSY GR, the ] has to be nonzero, at least with respect to the fermionic directions. Already, even in flat superspace, <math>D_{\hat{\alpha}}e_{\hat{\dot{\alpha}}}+\overline{D}_{\hat{\dot{\alpha}}}e_{\hat{\alpha}} \neq 0</math>.
When all of the gravitinos are in the supergravity supermultiplet, the number <math>\mathcal{N}</math> of gravitinos is equal to the number of ], which will be defined below.
In one version of SUGRA (but certainly not the only one), we have the following constraints upon the torsion tensor:
Therefore sometimes <math>\mathcal{N}</math> is defined to be the number of supercharges.
:<math>T^{\hat{\underline{\gamma}}}_{\hat{\underline{\alpha}}\hat{\underline{\beta}}} = 0</math>
:<math>T^{\hat{\mu}}_{\hat{\alpha}\hat{\beta}} = 0</math>
:<math>T^{\hat{\mu}}_{\hat{\dot{\alpha}}\hat{\dot{\beta}}} = 0</math>
:<math>T^{\hat{\mu}}_{\hat{\alpha}\hat{\dot{\beta}}} = 2i\sigma^{\hat{\mu}}_{\hat{\alpha}\hat{\dot{\beta}}}</math>
:<math>T^{\hat{\nu}}_{\hat{\mu}\hat{\underline{\alpha}}} = 0</math>
:<math>T^{\hat{\rho}}_{\hat{\mu}\hat{\nu}} = 0</math>
Here, <math>\underline{\alpha}</math> is a shorthand notation to mean the index runs over either the left or right Weyl spinors.


The ] of the supervierbein, <math>\left| e \right|</math>, gives us the volume factor for M. Equivalently, we have the volume 4|4-superform<math>e^{\hat{\mu}=0}\wedge \cdots \wedge e^{\hat{\mu}=3} \wedge e^{\hat{\alpha}=1} \wedge e^{\hat{\alpha}=2} \wedge e^{\hat{\dot{\alpha}}=1} \wedge e^{\hat{\dot{\alpha}}=2}</math>.


If we complexify the superdiffeomorphisms, there is a gauge where <math>E^{\mu}_{\hat{\dot{\alpha}}}=0</math>, <math>E^{\beta}_{\hat{\dot{\alpha}}}=0</math> and <math>E^{\dot{\beta}}_{\hat{\dot{\alpha}}}=\delta^{\dot{\beta}}_{\dot{\alpha}}</math>. The resulting chiral superspace has the coordinates x and Θ.
===Counting Gravitinos===


''R'' is a scalar valued chiral superfield derivable from the supervielbeins and spin connection. If ''f'' is any superfield, <math>\left( \bar{D}^2 - 8R \right) f</math> is always a chiral superfield.
Gravitinos are fermions, which means that according to the ] they must have an odd number of spinorial indices. In fact the gravitino field has one ] and one ] index, which means that gravitinos transform as a ] of a spinorial ] and the vector representation of the ]. This is a ].


The action for a SUGRA theory with chiral superfields ''X'', is given by
While there is only one vector representation for each Lorentz group, in general there are several different spinorial representations. Technically these are really representations of the ] of the Lorentz group called a ].
:<math>S = \int d^4x d^2\Theta 2\mathcal{E}\left + c.c.</math>
where ''K'' is the ] and ''W'' is the ], and <math>\mathcal{E}</math> is the chiral volume factor.


Unlike the case for flat superspace, adding a constant to either the Kähler or superpotential is now physical. A constant shift to the Kähler potential changes the effective ], while a constant shift to the superpotential changes the effective ]. As the effective Planck constant now depends upon the value of the chiral superfield ''X'', we need to rescale the supervierbeins (a field redefinition) to get a constant Planck constant. This is called the '''Einstein frame'''.
The canonical example of a spinorial representation is the ], which exists in every number of space-time dimensions. However the Dirac spinor representation is not always irreducible. When calculating the number <math>\mathcal{N}</math>, one always counts the number of ''real'' irreducible representations. The spinors with spins less than 3/2 that exist in each number of dimensions will be classified in the following subsection.


== ''N'' = 8 supergravity in 4 dimensions ==
===A classification of spinors===
] is the most ] quantum field theory which involves gravity and a finite number of fields. It can be found from a dimensional reduction of 11D supergravity by making the size of 7 of the dimensions go to zero. It has 8 supersymmetries which is the most any gravitational theory can have since there are 8 half-steps between spin 2 and spin −2. (A graviton has the highest spin in this theory which is a spin 2 particle.) More supersymmetries would mean the particles would have superpartners with spins higher than 2. The only theories with spins higher than 2 which are consistent involve an infinite number of particles (such as string theory and higher-spin theories). ] in his ''A Brief History of Time'' speculated that this theory could be the ]. However, in later years this was abandoned in favour of string theory. There has been renewed interest in the 21st century with the possibility that this theory may be finite.


== Higher-dimensional SUGRA ==
The available spinor representations depends on ''k''; The ] of the ] of the ] that preserves the ] of a massless ] is Spin(d-1)× Spin(d-k-1), where k is equal to the number ''d'' of spatial dimensions minus the number ''d-k'' of time dimensions. (See ]) For example, in our world, this is 3-1=2. Due to the mod 8 ] of the ]s of the Lorentz group, really we only need to consider ''k'' modulo 8.
{{Main|Higher-dimensional supergravity}}
Higher-dimensional SUGRA is the higher-dimensional, supersymmetric generalization of general relativity. Supergravity can be formulated in any number of dimensions up to eleven. Higher-dimensional SUGRA focuses upon supergravity in greater than four dimensions.


The number of supercharges in a ] depends on the dimension and the signature of spacetime. The supercharges occur in spinors. Thus the limit on the number of supercharges cannot be satisfied in a spacetime of arbitrary dimension. Some theoretical examples in which this is satisfied are:
For any value of ''k'' there is a Dirac representation, which is always of real dimension
<math>2^{1+\lfloor{\frac{2d-k}{2}}\rfloor}</math> where <math>\lfloor x\rfloor</math> is the greatest integer less than or equal to x. When <math>-2\leq k\leq 2 \pmod 8</math> there is a real ] representation, whose dimension is half that of the Dirac representation. When ''k'' is even there is a ] representation, whose real dimension is again half that of the Dirac spinor. Finally when ''k'' is divisible by eight, that is, when ''k'' is zero modulo eight, there is a ], whose real dimension is one quarter that of the Dirac spinor.


* 12-dimensional two-time theory
Occasionally one also considers ] which exist when <math>3\leq k\leq 5</math>, which have half has many compenents as Dirac spinors. When ''k''=4 these may also be Weyl, yielding Weyl symplectic Majorana spinors which have one quarter as many components as Dirac spinors.
* ]
* 10-dimensional supergravity theories
** ]: N = (1, 1)
** ]: N = (2, 0)
** ]: N = (1, 0)
* 9d supergravity theories
** Maximal 9d supergravity from 10d
** T-duality
** N = 1 Gauged supergravity


The supergravity theories that have attracted the most interest contain no spins higher than two. This means, in particular, that they do not contain any fields that transform as symmetric tensors of rank higher than two under Lorentz transformations. The consistency of interacting higher spin field theories is, however, presently a field of very active interest.
===Choosing Chiralities===


==See also==
Spinors in ''n''-dimensions are ] (really ]) not only of the ''n''-dimensional ], but also of a Lie algebra called the ''n''-dimensional ]. The most commonly used basis of the compex <math>2^{\lfloor n\rfloor}</math>-dimensional representation of the Clifford algebra, the representation that acts on the Dirac spinors, consists of the ].
{{div col |colwidth=18em}}
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
* ]
{{div col end}}


== References ==
When ''n'' is even the product of all of the gamma matrices, which is often referred to as <math>\Gamma_5</math> as it was first considered in the case ''n''=4, is not itself a member of the Clifford algebra. However, being a product of elements of the Clifford algebra, it is in the algebra's universal cover and so has an action on the Dirac spinors.
{{reflist}}


==Bibliography==
In particular, the Dirac spinors may be decomposed into eigenspaces of <math>\Gamma_5</math> with eigenvalues equal to <math>\pm(-1)^{-k/2}</math>, where ''k'' is the number of spatial minus temporal dimensions in the spacetime. The spinors in these two eigenspaces each form projective representations of the Lorentz group, known as ]. The eigenvalue under <math>\Gamma_5</math> is known as the ] of the spinor, which can be left or right-handed.


===Historical===
A particle that transforms as a single Weyl spinor is said to be chiral. The ], which is required by Lorentz invariance in ], implies that when there is a single time direction such particles have antiparticles of the opposite chirality.
* {{cite book |last1=Volkov |first1=D.V. |last2=Soroka |first2=V.A |chapter=Higgs effect for goldstone particles with spin 1/2 |year=1973 |title=Supersymmetry and Quantum Field Theory |chapter-url=http://www.jetpletters.ac.ru/ps/1568/article_24038.shtml |journal=Pis'ma V ZhETF |series=Lecture Notes in Physics |volume=18 |pages=529–533 |doi=10.1007/BFb0105271 |bibcode=1973JETPL..18..312V |isbn=978-3-540-64623-5}}
* {{cite journal |last1=Nath |first1=P. |last2=Arnowitt |first2=R. |year=1975 |title=Generalized super-gauge symmetry as a new framework for unified gauge theories |journal=Physics Letters B |volume=56 |issue=2 |page=177 |doi=10.1016/0370-2693(75)90297-x |bibcode=1975PhLB...56..177N}}
* {{cite journal |last1=Freedman |first1=D.Z. |last2=van Nieuwenhuizen |first2=P. |last3=Ferrara |first3=S. |year=1976 |title=Progress toward a theory of supergravity |journal=Physical Review D |volume=13 |issue=12 |pages=3214–3218 |doi=10.1103/physrevd.13.3214 |bibcode=1976PhRvD..13.3214F}}
* {{cite journal |doi=10.1016/0370-2693(78)90894-8 |title=Supergravity in theory in 11 dimensions |year=1978 |last1=Cremmer |first1=E. |last2=Julia |first2=B. |last3=Scherk |first3=J. |journal=Physics Letters B |volume=76 |issue=4 |pages=409–412 |bibcode=1978PhLB...76..409C}}
* {{cite journal |last1=Freund |first1=P. |last2=Rubin |first2=M. |year=1980 |title=Dynamics of dimensional reduction |journal=Physics Letters B |volume=97 |issue=2 |pages=233–235 |doi=10.1016/0370-2693(80)90590-0 |bibcode=1980PhLB...97..233F}}
* {{cite journal |doi=10.1103/PhysRevLett.49.970 |title=Locally supersymmetric grand unification |year=1982 |last1=Chamseddine |first1=A. H. |last2=Arnowitt |first2=R. |last3=Nath |first3=Pran |journal=Physical Review Letters |volume=49 |issue=14 |pages=970–974 |bibcode=1982PhRvL..49..970C}}
* {{cite journal |last1=Green |first1=Michael B. |last2=Schwarz |first2=John H. |year=1984 |title=Anomaly cancellation in supersymmetric ''D'' = 10 gauge theory and superstring theory |journal=Physics Letters B |volume=149 |issue=1–3 |pages=117–122 |doi=10.1016/0370-2693(84)91565-x |bibcode=1984PhLB..149..117G}}
* {{cite journal |last1=Deser |first1=S. |year=2018 |title=A brief history (and geography) of supergravity: The first 3 weeks... and after |url=https://authors.library.caltech.edu/77015/1/1704.05886.pdf |journal=The European Physical Journal H |volume=43 |issue=3 |pages=281–291 |doi=10.1140/epjh/e2018-90005-3 |arxiv=1704.05886 |bibcode=2018EPJH...43..281D |s2cid=119428513}}
* {{cite journal |last1=Duplij |first1=S. |year=2019 |title=Supergravity was discovered by D.V. Volkov and V.A. Soroka in 1973, wasn't it? |journal=East European Journal of Physics |issue=3 |pages=81–82 |doi=10.26565/2312-4334-2019-3-10 |doi-access=free|arxiv=1910.03259 }}


===General===
Recall that the eigenvalues of <math>\Gamma_5</math>, whose eigenspaces are the two chiralities, are <math>\pm(-1)^{-k/2}</math>. In particular, when ''k'' is equal to two modulo four the two eigenvalues are complex conjugate and so the two chiralities of Weyl representations are complex conjugate representations.
* {{cite arXiv
|first=Bernard |last=de Wit
|year=2002
|title=Supergravity
|eprint=hep-th/0212245
}}
*{{cite book
|last1=Pran |first1=Nath
|date=2017
|title=Supersymmetry, Supergravity, and Unification
|publisher=]
|isbn=978-0-521-19702-1
|url=https://books.google.com/books?id=g7OSDQAAQBAJ
}}
* {{cite book
|last1=Martin |first1=Stephen P.
|year=1998
|chapter=A Supersymmetry Primer
|editor-last=Kane |editor-first=Gordon L.
|title=Perspectives on Supersymmetry
|series=Advanced Series on Directions in High Energy Physics
|publisher=]
|volume=18 |pages=1–98
|arxiv=hep-ph/9709356
|doi=10.1142/9789812839657_0001
|isbn=978-981-02-3553-6
|s2cid=118973381
}}
* {{cite book
|last1=Drees |first1=Manuel
|last2=Godbole |first2=Rohini M.
|last3=Roy |first3=Probir
|date=2004
|title=Theory and Phenomenology of Sparticles
|publisher=]
|isbn=9-810-23739-1
|url=https://books.google.com/books?id=U3jVCgAAQBAJ
}}
* {{cite arXiv
|last1=Bilal |first1=Adel
|year=2001
|title=Introduction to Supersymmetry
|eprint=hep-th/0101055
}}
* {{cite journal
|last1=Brandt |first1=Friedemann
|year=2002
|title=Lectures on Supergravity
|journal=]
|volume=50 |issue=10–11 |pages=1126–1172
|arxiv=hep-th/0204035
|bibcode=2002ForPh..50.1126B
|doi=10.1002/1521-3978(200210)50:10/11<1126::AID-PROP1126>3.0.CO;2-B
|s2cid=15471713
}}
* {{cite arXiv
|last1=Sezgin|first1=Ergin
|year=2023
|title=Survey of supergravities
|class=hep-th
|eprint=2312.06754}}


==Further reading==
Complex conjugation in quantum theories corresponds to time inversion. Therefore the CPT theorem implies that when the number of Minkowski dimensions is divisible by four (so that ''k'' is equal to 2 modulo 4) there be an equal number of left-handed and right-handed supercharges. On the other hand, if the dimension is equal to 2 modulo 4, there can be different numbers of left and right-handed supercharges, and so often one labels the theory by a doublet <math>\mathcal{N}=(\mathcal{N}_L,\mathcal{N}_R)</math> where <math>\mathcal{N}_L</math> and <math>\mathcal{N}_R</math> are the number of left-handed and right-handed supercharges respectively.


* Dall'Agata, G., Zagermann, M., ''Supergravity: From First Principles to Modern Applications'', Springer, (2021). {{ISBN|978-3662639788}}
===Counting Supersymmetries===
* Freedman, D. Z., Van Proeyen, A., ''Supergravity'', Cambridge University Press, Cambridge, (2012). {{ISBN|978-0521194013}}
* Lauria, E., Van Proeyen, A., ''N = 2 Supergravity in D = 4, 5, 6 Dimensions'', Springer, (2020). {{ISBN|978-3030337551}}
* Năstase, H., ''Introduction to Supergravity and Its Applications'', (2024). {{ISBN|978-1009445597}}
* Nath, P., ''Supersymmetry, Supergravity, and Unification'', Cambridge University Press, Cambridge, (2016) {{ISBN|978-0521197021}}
* Tanii, Y., ''Introduction to Supergravity'', Springer, (2014). {{ISBN|978-4431548270}}
* Rausch de Traubenberg, M., Valenzuela, M., ''A Supergravity Primer'', World Scientific Press, Singapore, (2019). {{ISBN|978-9811210518}}
* Wess, P., ''Introduction To Supersymmetry And Supergravity'', World Scientific Press, Singapore, (1990). {{ISBN|978-9810200985}}
* Wess, P., Bagger, J., ''Supersymmetry and Supergravity'', Princeton University Press, Princeton, (1992). {{ISBN|978-0691025308}}


==External links==
All supergravity theories are invariant under transformations in the ], although individual configurations are not in general invariant under every transformation in this group. The super-Poincaré group is generated by the ], which is a ]. A Lie superalgebra is a <math>\mathbf{Z}_2</math> graded algebra in which the elements of degree zero are called bosonic and those of degree one are called fermionic. A commutator, that is an antisymmetric bracket satisfying the ] is defined between each pair of generators of fixed degree except for pairs of fermionic generators, for which instead one defines a symmetric bracket called an anticommutator.
* {{wikiquote-inline}}


{{Supersymmetry topics |state=collapsed}}
The fermionic generators are also called ]. Any configuration which is invariant under any of the supercharges is said to be ], and often ] demonstrate that such states are particularly easily treated because they are uneffected by many quantum corrections.
{{String theory topics |state=collapsed}}
{{theories of gravitation}}
{{Quantum gravity}}
{{Standard model of physics}}
{{Authority control}}
{{portal bar |Physics |Science}}


]
The supercharges transform as spinors, and the number of irreducible spinors of these fermionic generators is equal to the number of gravitinos <math>\mathcal{N}</math> defined above. Often <math>\mathcal{N}</math> is defined to be the number of fermionic generators, instead of the number of gravitinos, because this definition extends to supersymmetric theories without gravity.

Sometimes it is convenient to characterize theories not be the number <math>\mathcal{N}</math> of irreducible representations of gravitinos or supercharges, but instead by the total ''Q'' of their dimensions. This is because some features of the theory have the same ''Q''-dependence in any number of dimensions. For example, one is often only interested in theories in which all particles have ] less than or equal to two. This requires that ''Q'' not exceed 32, except possibly in special cases in which the supersymmetry is realized in an unconventional, nonlinear fashion with products of bosonic generators in the anticommutators of the fermionic generators.

==Examples==

===Why less than 32 SUSYs?===
The supergravity theories that have attracted the most interest contain no spins higher than 2. This means, in particular, that they do not contain any fields that transform as symmetric tensors of rank higher than two under Lorentz transformations. The consistency of interacting ] is, however, presently a field of very active interest.

The supercharges in every super-Poincaré algebra are generated by a multiplicative basis of ''m'' fundamental supercharges, and an additive basis of the supercharges (this definition of supercharges is a bit more broad than that given above) is given by a product of any subset of these ''m'' fundamental supercharges. The number of subsets of ''m'' elements is <math>2^m</math>, thus the space of supercharges is <math>2^m</math>-dimensional.

The fields in a supersymmetric theory form representations of the super-Poincaré algebra. It can be shown that when ''m'' is greater than 5 there are no representations that contain only fields of spin less than or equal to two. Thus we are interested in the case in which ''m'' is less than or equal to 5, which means that the maximal number of supercharges is 32. A supergravity theory with precisely 32 supersymmetries is known as a ].

Above we saw that the number of supercharges in a spinor depends on the dimension and the signature of spacetime. The supercharges occur in spinors. Thus the above limit on the number of supercharges cannot be satisfied in a spacetime of arbitrary dimension. Below we will describe some of the cases in which it is satisfied.

===A 12-dimensional two-time theory===

The highest dimension in which spinors exist with only 32 supercharges is 12. If there are 11 spatial directions and 1 time direction then there will be Weyl and Majorana spinors which both are of dimension 64, and so are too large. Although some authors have considered nonlinear actions of the supersymmetry in which higher spin fields may not appear.

If instead one considers 10 spatial direction and a ] then there is a Majorana-Weyl spinor, which as desired has only 32 components. For an overview of two-time theories by one of their main proponents, ], see his paper and . He considered 12-dimensional supergravity in .

It is widely, but not universally, believed that two-time theories do not make sense. For example the ]-based approach to quantum mechanics would have to be modified in the presence of a second Hamiltonian for the other time. However some claim that such a theory describes low energy behavior in ]'s ]. Others claim that the 12-dimensions of F-theory are merely a bookkeeping device and should not be confused with spacetime coordinates, or that two of the dimensions are somehow dual to each other and so should not be treated independently.

===11-dimensional maximal SUGRA ===
This ] is the classical limit of ]. There is, classically, only one 11-dimensional supergravity theory. Like all maximal supergravities, it contains a single supermultiplet, the supergravity supermultiplet. This supermultiplet contains the graviton, a Majorana gravitino and a 3-form gauge connection often called the C-field.

It contains two ] solutions, a 2-brane and a 5-brane, which are electrically and magnetically charged respectively with respect to the C-field. This means that 2-brane and 5-brane charge are the violations of the Bianchi identities for the dual C-field and original C-field respectively. The supergravity 2-brane and 5-brane are the classical limits of the ] and ] in M-theory.

Although the p-branes are often referred to as ]s, technically they are sources and not solitons as the field configurations are singular. However, the singularity of the supersymmetric 5-brane solution is at the end of an infinitely long throat and when defining the quantum theory of the 5-brane one usually excises a region surrounding the singularity from the spacetime.

===10d SUGRA theories===
====Type IIA SUGRA: N=(1,1)====

This maximal supergravity is the classical limit of ]. The field content of the supergravity supermultiplet consists of a graviton, a Majorana gravitino, a ], odd-dimensional ] gauge potentials, a ] and a ].

The Bianchi identities of the Ramond-Ramond gauge potentials <math>C_{2k-1}</math> can be violated by adding sources <math>\rho</math>, which are called D(8-2''k'')-branes

::<math> ddC_{2k-1}=\rho. \,\,\,</math>

In the ] of type IIA supergravity there exist Ramond-Ramond gauge potentials for 0<''k''<6, which leads to D0-branes (also called D-particles), D2-branes, D4-branes, D6-branes and, if one includes the case ''k=-1'', D8-branes. In addition there are fundamental strings and their electromagnetic duals, which are called ]s.

Although obviously there are no -1-form gauge connections, the corresponding 0-form field strength, G<sub>0</sub> may exist. This field strength is called the '''Romans mass''' and when it is not equal to zero the supergravity theory is called ] or ]. From the above Bianchi identity we see that a D8-brane is a domain wall between zones of differing G<sub>0</sub>, thus in the presence of a D8-brane at least part of the spacetime will be described by the Romans theory.

====IIA SUGRA from 11d SUGRA====
IIA SUGRA is the ] of 11-dimensional supergravity on a circle. This means that 11d supergravity on the spacetime <math>M^{10}\times S^1\,</math> is equivalent to IIA supergravity on the 10-manifold <math>M^{10}\,</math> where one eliminates modes with masses proportional to the inverse radius of the circle ''S''<sup>1</sup>.

In particular the field and brane content of IIA supergravity can be derived via this dimensional reduction procedure. The field <math>G_0</math> however does not arise from the dimensional reduction, massive IIA is not known to be the dimensional reduction of any higher-dimensional theory. The 1-form Ramond-Ramond potential <math>C_1\,</math> is the usual 1-form connection that arises from the Kaluza-Klein procedure, it arises from the components of the 11-d metric that contain one index along the compactified circle. The IIA 3-form gauge potential <math>C_3\,</math> is the reduction of the 11d 3-form gauge potential components with indices that do not lie along the circle, while the IIA Kalb-Ramond 2-form B-field consists of those components of the 11-dimensional 3-form with one index along the circle. The higher forms in IIA are not independent degrees of freedom, but are obtained from the lower forms using Hodge duality.

Similarly the IIA branes descend from the 11-dimension branes and geometry. The IIA D0-brane is a Kaluza-Klein momentum mode along the compactified circle. The IIA fundamental string is an 11-dimensional membrane which wraps the compactified circle. The IIA D2-brane is an 11-dimensional membrane that does not wrap the compactified circle. The IIA D4-brane is an 11-dimensional 5-brane that wraps the compactified circle. The IIA NS5-brane is an 11-dimensional 5-brane that does not wrap the compactified circle. The IIA D6-brane is a Kaluza-Klein monopole, that is, a topological defect in the compact circle fibration. The lift of the IIA D8-brane to 11-dimensions is not known, as one side of the IIA geometry as a nontrivial Romans mass, and an 11-dimensional original of the Romans mass is unknown.

====Type IIB SUGRA: N=(2,0)====

This maximal supergravity is the classical limit of ]. The field content of the supergravity supermultiplet consists of a graviton, a Weyl gravitino, a ], even-dimensional ] gauge potentials, a ] and a ].

The Ramond-Ramond fields are sourced by odd-dimensional D(2''k''+1)-branes, which host supersymmetric U(1) gauge theories. As in IIA supergravity, the fundamental string is an electric source for the Kalb-Ramond B-field and the ] is a magnetic source. Unlike that of the IIA theory, the NS5-brane hosts a worldvolume U(1) supersymmetric gauge theory with <math>\mathcal N=(1,1)</math> supersymmetry, although some of this supersymmetry may be broken depending on the geometry of the spacetime and the other branes that are present.

This theory enjoys a SL(2,'''R''') symmetry known as ] that interchanges the Kalb-Ramond field and the RR 2-form and also mixes the dilaton and the RR 0-form ].

====Type I gauged SUGRA: N=(1,0)====

These are the classical limits of ] and the two ]. There is a single ] of supercharges, which in 10 dimensions contains 16 supercharges. As 16 is less than 32, the maximal number of supercharges, type I is not a maximal supergravity theory.

In particular this implies that there is more than one variety of supermultiplet. In fact, there are two. As usual, there is a supergravity supermultiplet. This is smaller than the supergravity supermultiplet in type II, it contains only the ], a Majorana-Weyl ], a 2-form gauge potential, the ] and a ]. Whether this 2-form is considered to be a ] or ] depends on whether one considers the supergravity theory to be a classical limit of a ] or ]. There is also a ], which contains a one-form gauge potential called a ] and also a Majorana-Weyl ].

Unlike type IIA and IIB supergravities, for which the classical theory is unique, as a classical theory <math>\mathcal{N}=1</math> supergravity is consistent with a single supergravity supermultiplet and any number of vector multiplets. It is also consistent without the supergravity supermultiplet, but then it would contain no graviton and so would not be a supergravity theory. While one may add multiple supergravity supermultiplets, it is not known if they may consistently interact. One is free not only to determine the number, if any, of vector supermultiplets, but also there is some freedom in determining their couplings. They must describe a classical ] ], but the choice of gauge group is arbitrary. In addition one is free to make some choices of gravitational couplings in the classical theory.

While there are many varieties of classical <math>\mathcal{N}=1</math> supergravities, not all of these varieties are the classical limits of quantum theories. Generically the quantum versions of these theories suffer from various anomalies, as can be seen already at 1-loop in the ] ]. In 1984 and 1985 ] and ] have shown that if one includes precisely 496 vector supermultiplets and chooses certain couplings of the 2-form and the metric then the ] cancel. This is called the ].

In addition, anomaly cancellation requires one to cancel the ]. This fixes the gauge symmetry algebra to be either <math>\mathfrak{so}(32)</math>, <math>\mathfrak{e}_8 \oplus \mathfrak{e}_8</math>, <math>\mathfrak{e}_8 \oplus 248\mathfrak{u}(1)</math> or <math>496\mathfrak{u}(1)</math>. However, only the first two Lie algebras can be gotten from superstring theory. Quantum theories with at least 8 supercharges tend to have continuous ]s of vacua. In ] of these theories, which have 16 supercharges, there exist degenerate vacua with different values of various Wilson loops. Such Wilson loops may be used to break the gauge symmetries to various subgroups. In particular the above gauge symmetries may be broken to obtain not only the standard model gauge symmetry but also symmetry groups such as SO(10) and SU(5) that are popular in ].

===9d SUGRA theories===
In 9-dimensional Minkowski space the only irreducible spinor representation is the ], which has 16 components. Thus supercharges inhabit Majorana spinors of which there are at most two.

====Maximal 9d SUGRA from 10d====

In particular, if there are two Majorana spinors then one obtains the 9-dimensional maximal supergravity theory. Recall that in 10 dimensions there were two inequivalent maximal supergravity theories, IIA and IIB. The ] of either IIA or IIB on a circle is the unique 9-dimensional supergravity. In other words, IIA or IIB on the product of a 9-dimensional space ''M''<sup>9</sup> and a circle is equivalent to the 9-dimension theory on ''M''<sup>9</sup>, with Kaluza-Klein modes if one does not take the limit in which the circle shrinks to zero.

====T-duality====

More generally one could consider the 10-dimensional theory on a nontrivial ] over ''M''<sup>9</sup>. Dimensional reduction still leads to a 9-dimensional theory on ''M''<sup>9</sup>, but with a 1-form ] equal to the ] of the circle bundle and a 2-form ] which is equal to the ] of the old circle bundle. One may then lift this theory to the other 10-dimensional theory, in which case one finds that the 1-form gauge potential lifts to the ]. Similarly, the connection of the fibration of the circle in the second 10-dimensional theory is the integral of the Kalb-Ramond field of the original theory over the compactified circle.

This transformation between the two 10-dimensional theories is known as ]. While T-duality in supergravity involves dimensional reduction and so loses information, in the full quantum ] the extra information is stored in string winding modes and so T-duality is a ] between the two 10-dimensional theories. The above construction can be used to obtain the relation between the circle bundle's connection and dual Kalb-Ramond field even in the full quantum theory.

====N=1 Gauged SUGRA====
As was the case in the parent 10-dimensional theory, 9-dimensional N=1 supergravity contains a single supergravity multiplet and an arbitrary number of vector multiplets. These vector multiplets may be coupled so as to admit arbitrary gauge theories, although not all possibilities have quantum completions. Unlike the 10-dimensional theory, as was described in the previous subsection, the supergravity multiplet itself contains a vector and so there will always be at least a U(1) gauge symmetry, even in the N=2 case.

===4d SUGRA theories===
====Maximal SUGRA from Freund-Rubin====
====4-dimensional N=1 SUGRA====

==See also==

*]
*]
*]
*]
*]

==References==
===Historical===
* E. Cremmer, B. Julia and J. Scherk, "Supergravity theory in eleven dimensions", ''Physics Letters'' '''B76''' (1978) pp 409-412.
* P. Freund and M. Rubin, "Dynamics of dimensional reduction", ''Physics Letters'' '''B97''' (1980) pp 233-235.
* Michael B. Green, John H. Schwarz, "Anomaly Cancellation in Supersymmetric D=10 Gauge Theory and Superstring Theory", ''Physics Letters'' '''B149''' (1984) pp117-122.

===General===
* Adel Bilal, "" (2001) ArXiv hep-th/0101055. ''(a comprehensive introduction to supersymmetry.)''

* Friedemann Brandt, "" (2002) ArXiv hep-th/0204035. ''(an introduction to 4-dimensional N=1 supergravity.)''

]
] ]
]

]
]
]
]
]

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Modern theory of gravitation that combines supersymmetry and general relativity
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In theoretical physics, supergravity (supergravity theory; SUGRA for short) is a modern field theory that combines the principles of supersymmetry and general relativity; this is in contrast to non-gravitational supersymmetric theories such as the Minimal Supersymmetric Standard Model. Supergravity is the gauge theory of local supersymmetry. Since the supersymmetry (SUSY) generators form together with the Poincaré algebra a superalgebra, called the super-Poincaré algebra, supersymmetry as a gauge theory makes gravity arise in a natural way.

Gravitons

Like all covariant approaches to quantum gravity, supergravity contains a spin-2 field whose quantum is the graviton. Supersymmetry requires the graviton field to have a superpartner. This field has spin 3/2 and its quantum is the gravitino. The number of gravitino fields is equal to the number of supersymmetries.

History

Gauge supersymmetry

The first theory of local supersymmetry was proposed by Dick Arnowitt and Pran Nath in 1975 and was called gauge supersymmetry.

Supergravity

The first model of 4-dimensional supergravity (without this denotation) was formulated by Dmitri Vasilievich Volkov and Vyacheslav A. Soroka in 1973, emphasizing the importance of spontaneous supersymmetry breaking for the possibility of a realistic model. The minimal version of 4-dimensional supergravity (with unbroken local supersymmetry) was constructed in detail in 1976 by Dan Freedman, Sergio Ferrara and Peter van Nieuwenhuizen. In 2019 the three were awarded a special Breakthrough Prize in Fundamental Physics for the discovery. The key issue of whether or not the spin 3/2 field is consistently coupled was resolved in the nearly simultaneous paper, by Deser and Zumino, which independently proposed the minimal 4-dimensional model. It was quickly generalized to many different theories in various numbers of dimensions and involving additional (N) supersymmetries. Supergravity theories with N>1 are usually referred to as extended supergravity (SUEGRA). Some supergravity theories were shown to be related to certain higher-dimensional supergravity theories via dimensional reduction (e.g. N=1, 11-dimensional supergravity is dimensionally reduced on T to 4-dimensional, ungauged, N = 8 supergravity). The resulting theories were sometimes referred to as Kaluza–Klein theories as Kaluza and Klein constructed in 1919 a 5-dimensional gravitational theory, that when dimensionally reduced on a circle, its 4-dimensional non-massive modes describe electromagnetism coupled to gravity.

mSUGRA

mSUGRA means minimal SUper GRAvity. The construction of a realistic model of particle interactions within the N = 1 supergravity framework where supersymmetry (SUSY) breaks by a super Higgs mechanism carried out by Ali Chamseddine, Richard Arnowitt and Pran Nath in 1982. Collectively now known as minimal supergravity Grand Unification Theories (mSUGRA GUT), gravity mediates the breaking of SUSY through the existence of a hidden sector. mSUGRA naturally generates the Soft SUSY breaking terms which are a consequence of the Super Higgs effect. Radiative breaking of electroweak symmetry through Renormalization Group Equations (RGEs) follows as an immediate consequence. Due to its predictive power, requiring only four input parameters and a sign to determine the low energy phenomenology from the scale of Grand Unification, its interest is a widely investigated model of particle physics

See also: Gravity-Mediated Supersymmetry Breaking in the MSSM

11D: the maximal SUGRA

Main article: Eleven-dimensional supergravity

One of these supergravities, the 11-dimensional theory, generated considerable excitement as the first potential candidate for the theory of everything. This excitement was built on four pillars, two of which have now been largely discredited:

  • Werner Nahm showed 11 dimensions as the largest number of dimensions consistent with a single graviton, and more dimensions will show particles with spins greater than 2. However, if two of these dimensions are time-like, these problems are avoided in 12 dimensions. Itzhak Bars gives this emphasis.
  • In 1981 Ed Witten showed 11 as the smallest number of dimensions big enough to contain the gauge groups of the Standard Model, namely SU(3) for the strong interactions and SU(2) times U(1) for the electroweak interactions. Many techniques exist to embed the standard model gauge group in supergravity in any number of dimensions like the obligatory gauge symmetry in type I and heterotic string theories, and obtained in type II string theory by compactification on certain Calabi–Yau manifolds. The D-branes engineer gauge symmetries too.
  • In 1978 Eugène Cremmer, Bernard Julia and Joël Scherk (CJS) found the classical action for an 11-dimensional supergravity theory. This remains today the only known classical 11-dimensional theory with local supersymmetry and no fields of spin higher than two. Other 11-dimensional theories known and quantum-mechanically inequivalent reduce to the CJS theory when one imposes the classical equations of motion. However, in the mid-1980s Bernard de Wit and Hermann Nicolai found an alternate theory in D=11 Supergravity with Local SU(8) Invariance. While not manifestly Lorentz-invariant, it is in many ways superior, because it dimensionally-reduces to the 4-dimensional theory without recourse to the classical equations of motion.
  • In 1980 Peter Freund and M. A. Rubin showed that compactification from 11 dimensions preserving all the SUSY generators could occur in two ways, leaving only 4 or 7 macroscopic dimensions, the others compact. The noncompact dimensions have to form an anti-de Sitter space. There are many possible compactifications, but the Freund-Rubin compactification's invariance under all of the supersymmetry transformations preserves the action.

Finally, the first two results each appeared to establish 11 dimensions, the third result appeared to specify the theory, and the last result explained why the observed universe appears to be four-dimensional.

Many of the details of the theory were fleshed out by Peter van Nieuwenhuizen, Sergio Ferrara and Daniel Z. Freedman.

The end of the SUGRA era

The initial excitement over 11-dimensional supergravity soon waned, as various failings were discovered, and attempts to repair the model failed as well. Problems included:

  • The compact manifolds which were known at the time and which contained the standard model were not compatible with supersymmetry, and could not hold quarks or leptons. One suggestion was to replace the compact dimensions with the 7-sphere, with the symmetry group SO(8), or the squashed 7-sphere, with symmetry group SO(5) times SU(2).
  • Until recently, the physical neutrinos seen in experiments were believed to be massless, and appeared to be left-handed, a phenomenon referred to as the chirality of the Standard Model. It was very difficult to construct a chiral fermion from a compactification — the compactified manifold needed to have singularities, but physics near singularities did not begin to be understood until the advent of orbifold conformal field theories in the late 1980s.
  • Supergravity models generically result in an unrealistically large cosmological constant in four dimensions, and that constant is difficult to remove, and so require fine-tuning. This is still a problem today.
  • Quantization of the theory led to quantum field theory gauge anomalies rendering the theory inconsistent. In the intervening years physicists have learned how to cancel these anomalies.

Some of these difficulties could be avoided by moving to a 10-dimensional theory involving superstrings. However, by moving to 10 dimensions one loses the sense of uniqueness of the 11-dimensional theory.

The core breakthrough for the 10-dimensional theory, known as the first superstring revolution, was a demonstration by Michael B. Green, John H. Schwarz and David Gross that there are only three supergravity models in 10 dimensions which have gauge symmetries and in which all of the gauge and gravitational anomalies cancel. These were theories built on the groups SO(32) and E 8 × E 8 {\displaystyle E_{8}\times E_{8}} , the direct product of two copies of E8. Today we know that, using D-branes for example, gauge symmetries can be introduced in other 10-dimensional theories as well.

The second superstring revolution

Initial excitement about the 10-dimensional theories, and the string theories that provide their quantum completion, died by the end of the 1980s. There were too many Calabi–Yaus to compactify on, many more than Yau had estimated, as he admitted in December 2005 at the 23rd International Solvay Conference in Physics. None quite gave the standard model, but it seemed as though one could get close with enough effort in many distinct ways. Plus no one understood the theory beyond the regime of applicability of string perturbation theory.

There was a comparatively quiet period at the beginning of the 1990s; however, several important tools were developed. For example, it became apparent that the various superstring theories were related by "string dualities", some of which relate weak string-coupling - perturbative - physics in one model with strong string-coupling - non-perturbative - in another.

Then the second superstring revolution occurred. Joseph Polchinski realized that obscure string theory objects, called D-branes, which he discovered six years earlier, equate to stringy versions of the p-branes known in supergravity theories. String theory perturbation didn't restrict these p-branes. Thanks to supersymmetry, p-branes in supergravity gained understanding well beyond the limits of string theory.

Armed with this new nonperturbative tool, Edward Witten and many others could show all of the perturbative string theories as descriptions of different states in a single theory that Witten named M-theory. Furthermore, he argued that M-theory's long wavelength limit, i.e. when the quantum wavelength associated to objects in the theory appear much larger than the size of the 11th dimension, needs 11-dimensional supergravity descriptors that fell out of favor with the first superstring revolution 10 years earlier, accompanied by the 2- and 5-branes.

Therefore, supergravity comes full circle and uses a common framework in understanding features of string theories, M-theory, and their compactifications to lower spacetime dimensions.

Relation to superstrings

The term "low energy limits" labels some 10-dimensional supergravity theories. These arise as the massless, tree-level approximation of string theories. True effective field theories of string theories, rather than truncations, are rarely available. Due to string dualities, the conjectured 11-dimensional M-theory is required to have 11-dimensional supergravity as a "low energy limit". However, this doesn't necessarily mean that string theory/M-theory is the only possible UV completion of supergravity; supergravity research is useful independent of those relations.

4D N = 1 SUGRA

Main article: 4D N = 1 supergravity

Before we move on to SUGRA proper, let's recapitulate some important details about general relativity. We have a 4D differentiable manifold M with a Spin(3,1) principal bundle over it. This principal bundle represents the local Lorentz symmetry. In addition, we have a vector bundle T over the manifold with the fiber having four real dimensions and transforming as a vector under Spin(3,1). We have an invertible linear map from the tangent bundle TM to T. This map is the vierbein. The local Lorentz symmetry has a gauge connection associated with it, the spin connection.

The following discussion will be in superspace notation, as opposed to the component notation, which isn't manifestly covariant under SUSY. There are actually many different versions of SUGRA out there which are inequivalent in the sense that their actions and constraints upon the torsion tensor are different, but ultimately equivalent in that we can always perform a field redefinition of the supervierbeins and spin connection to get from one version to another.

In 4D N=1 SUGRA, we have a 4|4 real differentiable supermanifold M, i.e. we have 4 real bosonic dimensions and 4 real fermionic dimensions. As in the nonsupersymmetric case, we have a Spin(3,1) principal bundle over M. We have an R vector bundle T over M. The fiber of T transforms under the local Lorentz group as follows; the four real bosonic dimensions transform as a vector and the four real fermionic dimensions transform as a Majorana spinor. This Majorana spinor can be reexpressed as a complex left-handed Weyl spinor and its complex conjugate right-handed Weyl spinor (they're not independent of each other). We also have a spin connection as before.

We will use the following conventions; the spatial (both bosonic and fermionic) indices will be indicated by M, N, ... . The bosonic spatial indices will be indicated by μ, ν, ..., the left-handed Weyl spatial indices by α, β,..., and the right-handed Weyl spatial indices by α ˙ {\displaystyle {\dot {\alpha }}} , β ˙ {\displaystyle {\dot {\beta }}} , ... . The indices for the fiber of T will follow a similar notation, except that they will be hatted like this: M ^ , α ^ {\displaystyle {\hat {M}},{\hat {\alpha }}} . See van der Waerden notation for more details. M = ( μ , α , α ˙ ) {\displaystyle M=(\mu ,\alpha ,{\dot {\alpha }})} . The supervierbein is denoted by e N M ^ {\displaystyle e_{N}^{\hat {M}}} , and the spin connection by ω M ^ N ^ P {\displaystyle \omega _{{\hat {M}}{\hat {N}}P}} . The inverse supervierbein is denoted by E M ^ N {\displaystyle E_{\hat {M}}^{N}} .

The supervierbein and spin connection are real in the sense that they satisfy the reality conditions

e N M ^ ( x , θ ¯ , θ ) = e N M ^ ( x , θ , θ ¯ ) {\displaystyle e_{N}^{\hat {M}}(x,{\overline {\theta }},\theta )^{*}=e_{N^{*}}^{{\hat {M}}^{*}}(x,\theta ,{\overline {\theta }})} where μ = μ {\displaystyle \mu ^{*}=\mu } , α = α ˙ {\displaystyle \alpha ^{*}={\dot {\alpha }}} , and α ˙ = α {\displaystyle {\dot {\alpha }}^{*}=\alpha } and ω ( x , θ ¯ , θ ) = ω ( x , θ , θ ¯ ) {\displaystyle \omega (x,{\overline {\theta }},\theta )^{*}=\omega (x,\theta ,{\overline {\theta }})} .

The covariant derivative is defined as

D M ^ f = E M ^ N ( N f + ω N [ f ] ) {\displaystyle D_{\hat {M}}f=E_{\hat {M}}^{N}\left(\partial _{N}f+\omega _{N}\right)} .

The covariant exterior derivative as defined over supermanifolds needs to be super graded. This means that every time we interchange two fermionic indices, we pick up a +1 sign factor, instead of -1.

The presence or absence of R symmetries is optional, but if R-symmetry exists, the integrand over the full superspace has to have an R-charge of 0 and the integrand over chiral superspace has to have an R-charge of 2.

A chiral superfield X is a superfield which satisfies D ¯ α ˙ ^ X = 0 {\displaystyle {\overline {D}}_{\hat {\dot {\alpha }}}X=0} . In order for this constraint to be consistent, we require the integrability conditions that { D ¯ α ˙ ^ , D ¯ β ˙ ^ } = c α ˙ ^ β ˙ ^ γ ˙ ^ D ¯ γ ˙ ^ {\displaystyle \left\{{\overline {D}}_{\hat {\dot {\alpha }}},{\overline {D}}_{\hat {\dot {\beta }}}\right\}=c_{{\hat {\dot {\alpha }}}{\hat {\dot {\beta }}}}^{\hat {\dot {\gamma }}}{\overline {D}}_{\hat {\dot {\gamma }}}} for some coefficients c.

Unlike nonSUSY GR, the torsion has to be nonzero, at least with respect to the fermionic directions. Already, even in flat superspace, D α ^ e α ˙ ^ + D ¯ α ˙ ^ e α ^ 0 {\displaystyle D_{\hat {\alpha }}e_{\hat {\dot {\alpha }}}+{\overline {D}}_{\hat {\dot {\alpha }}}e_{\hat {\alpha }}\neq 0} . In one version of SUGRA (but certainly not the only one), we have the following constraints upon the torsion tensor:

T α _ ^ β _ ^ γ _ ^ = 0 {\displaystyle T_{{\hat {\underline {\alpha }}}{\hat {\underline {\beta }}}}^{\hat {\underline {\gamma }}}=0}
T α ^ β ^ μ ^ = 0 {\displaystyle T_{{\hat {\alpha }}{\hat {\beta }}}^{\hat {\mu }}=0}
T α ˙ ^ β ˙ ^ μ ^ = 0 {\displaystyle T_{{\hat {\dot {\alpha }}}{\hat {\dot {\beta }}}}^{\hat {\mu }}=0}
T α ^ β ˙ ^ μ ^ = 2 i σ α ^ β ˙ ^ μ ^ {\displaystyle T_{{\hat {\alpha }}{\hat {\dot {\beta }}}}^{\hat {\mu }}=2i\sigma _{{\hat {\alpha }}{\hat {\dot {\beta }}}}^{\hat {\mu }}}
T μ ^ α _ ^ ν ^ = 0 {\displaystyle T_{{\hat {\mu }}{\hat {\underline {\alpha }}}}^{\hat {\nu }}=0}
T μ ^ ν ^ ρ ^ = 0 {\displaystyle T_{{\hat {\mu }}{\hat {\nu }}}^{\hat {\rho }}=0}

Here, α _ {\displaystyle {\underline {\alpha }}} is a shorthand notation to mean the index runs over either the left or right Weyl spinors.

The superdeterminant of the supervierbein, | e | {\displaystyle \left|e\right|} , gives us the volume factor for M. Equivalently, we have the volume 4|4-superform e μ ^ = 0 e μ ^ = 3 e α ^ = 1 e α ^ = 2 e α ˙ ^ = 1 e α ˙ ^ = 2 {\displaystyle e^{{\hat {\mu }}=0}\wedge \cdots \wedge e^{{\hat {\mu }}=3}\wedge e^{{\hat {\alpha }}=1}\wedge e^{{\hat {\alpha }}=2}\wedge e^{{\hat {\dot {\alpha }}}=1}\wedge e^{{\hat {\dot {\alpha }}}=2}} .

If we complexify the superdiffeomorphisms, there is a gauge where E α ˙ ^ μ = 0 {\displaystyle E_{\hat {\dot {\alpha }}}^{\mu }=0} , E α ˙ ^ β = 0 {\displaystyle E_{\hat {\dot {\alpha }}}^{\beta }=0} and E α ˙ ^ β ˙ = δ α ˙ β ˙ {\displaystyle E_{\hat {\dot {\alpha }}}^{\dot {\beta }}=\delta _{\dot {\alpha }}^{\dot {\beta }}} . The resulting chiral superspace has the coordinates x and Θ.

R is a scalar valued chiral superfield derivable from the supervielbeins and spin connection. If f is any superfield, ( D ¯ 2 8 R ) f {\displaystyle \left({\bar {D}}^{2}-8R\right)f} is always a chiral superfield.

The action for a SUGRA theory with chiral superfields X, is given by

S = d 4 x d 2 Θ 2 E [ 3 8 ( D ¯ 2 8 R ) e K ( X ¯ , X ) / 3 + W ( X ) ] + c . c . {\displaystyle S=\int d^{4}xd^{2}\Theta 2{\mathcal {E}}\left+c.c.}

where K is the Kähler potential and W is the superpotential, and E {\displaystyle {\mathcal {E}}} is the chiral volume factor.

Unlike the case for flat superspace, adding a constant to either the Kähler or superpotential is now physical. A constant shift to the Kähler potential changes the effective Planck constant, while a constant shift to the superpotential changes the effective cosmological constant. As the effective Planck constant now depends upon the value of the chiral superfield X, we need to rescale the supervierbeins (a field redefinition) to get a constant Planck constant. This is called the Einstein frame.

N = 8 supergravity in 4 dimensions

N = 8 supergravity is the most symmetric quantum field theory which involves gravity and a finite number of fields. It can be found from a dimensional reduction of 11D supergravity by making the size of 7 of the dimensions go to zero. It has 8 supersymmetries which is the most any gravitational theory can have since there are 8 half-steps between spin 2 and spin −2. (A graviton has the highest spin in this theory which is a spin 2 particle.) More supersymmetries would mean the particles would have superpartners with spins higher than 2. The only theories with spins higher than 2 which are consistent involve an infinite number of particles (such as string theory and higher-spin theories). Stephen Hawking in his A Brief History of Time speculated that this theory could be the Theory of Everything. However, in later years this was abandoned in favour of string theory. There has been renewed interest in the 21st century with the possibility that this theory may be finite.

Higher-dimensional SUGRA

Main article: Higher-dimensional supergravity

Higher-dimensional SUGRA is the higher-dimensional, supersymmetric generalization of general relativity. Supergravity can be formulated in any number of dimensions up to eleven. Higher-dimensional SUGRA focuses upon supergravity in greater than four dimensions.

The number of supercharges in a spinor depends on the dimension and the signature of spacetime. The supercharges occur in spinors. Thus the limit on the number of supercharges cannot be satisfied in a spacetime of arbitrary dimension. Some theoretical examples in which this is satisfied are:

The supergravity theories that have attracted the most interest contain no spins higher than two. This means, in particular, that they do not contain any fields that transform as symmetric tensors of rank higher than two under Lorentz transformations. The consistency of interacting higher spin field theories is, however, presently a field of very active interest.

See also

References

  1. Van Nieuwenhuizen, P. (1981). "Supergravity". Physics Reports. 68 (4): 189–398. Bibcode:1981PhR....68..189V. doi:10.1016/0370-1573(81)90157-5.
  2. Rovelli, Carlo (2000). "Notes for a brief history of quantum gravity". arXiv:gr-qc/0006061.
  3. Nath, P.; Arnowitt, R. (1975). "Generalized Super-Gauge Symmetry as a New Framework for Unified Gauge Theories". Physics Letters B. 56 (2): 177. Bibcode:1975PhLB...56..177N. doi:10.1016/0370-2693(75)90297-x.
  4. Volkov, D.V.; Soroka, V.A. (1973). "Higgs effect for Goldstone particles with spin 1/2". JETP Letters. 16 (11): 438–440. Bibcode:1973JETPL..18..312V. doi:10.1007/BFb0105271.
  5. Freedman, D.Z.; van Nieuwenhuizen, P.; Ferrara, S. (1976). "Progress Toward A Theory Of Supergravity". Physical Review D. 13 (12): 3214–3218. Bibcode:1976PhRvD..13.3214F. doi:10.1103/physrevd.13.3214.
  6. "Supergravity scientists share $3M US Breakthrough Prize". CBC News.
  7. Deser, S.; Zumino, B. (1976). "Consistent Supergravity". Physics Letters B. 62 (3): 335–337. Bibcode:1976PhLB...62..335D. doi:10.1016/0370-2693(76)90089-7.
  8. Nahm, Werner (1978). "Supersymmetries and their representations". Nuclear Physics B. 135 (1): 149–166. Bibcode:1978NuPhB.135..149N. doi:10.1016/0550-3213(78)90218-3.
  9. Witten, Ed (1981). "Search for a realistic Kaluza-Klein theory". Nuclear Physics B. 186 (3): 412–428. Bibcode:1981NuPhB.186..412W. doi:10.1016/0550-3213(81)90021-3.
  10. E. Cremmer, B. Julia and J. Scherk, "Supergravity theory in eleven dimensions", Physics Letters B76 (1978) pp 409-412,
  11. Peter G.O. Freund; Mark A. Rubin (1980). "Dynamics of dimensional reduction". Physics Letters B. 97 (2): 233–235. Bibcode:1980PhLB...97..233F. doi:10.1016/0370-2693(80)90590-0.
  12. Duff, M. J. (1998). "A Layman's Guide to M-theory". arXiv:hep-th/9805177.
  13. Blumenhagen, R.; Cvetic, M.; Langacker, P.; Shiu, G. (2005). "Toward Realistic Intersecting D-Brane Models". Annual Review of Nuclear and Particle Science. 55 (1): 71–139. arXiv:hep-th/0502005. Bibcode:2005ARNPS..55...71B. doi:10.1146/annurev.nucl.55.090704.151541. S2CID 15148429.

Bibliography

Historical

General

Further reading

  • Dall'Agata, G., Zagermann, M., Supergravity: From First Principles to Modern Applications, Springer, (2021). ISBN 978-3662639788
  • Freedman, D. Z., Van Proeyen, A., Supergravity, Cambridge University Press, Cambridge, (2012). ISBN 978-0521194013
  • Lauria, E., Van Proeyen, A., N = 2 Supergravity in D = 4, 5, 6 Dimensions, Springer, (2020). ISBN 978-3030337551
  • Năstase, H., Introduction to Supergravity and Its Applications, (2024). ISBN 978-1009445597
  • Nath, P., Supersymmetry, Supergravity, and Unification, Cambridge University Press, Cambridge, (2016) ISBN 978-0521197021
  • Tanii, Y., Introduction to Supergravity, Springer, (2014). ISBN 978-4431548270
  • Rausch de Traubenberg, M., Valenzuela, M., A Supergravity Primer, World Scientific Press, Singapore, (2019). ISBN 978-9811210518
  • Wess, P., Introduction To Supersymmetry And Supergravity, World Scientific Press, Singapore, (1990). ISBN 978-9810200985
  • Wess, P., Bagger, J., Supersymmetry and Supergravity, Princeton University Press, Princeton, (1992). ISBN 978-0691025308

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