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Christopher T. Hill
Born	(1951-06-19) June 19, 1951 (age 73) Neenah, Wisconsin
Nationality	American
Alma mater	Massachusetts Institute of Technology (BS, MS) California Institute of Technology (PhD)
Known for	Infrared fixed point of the top quark; Topcolor; Top quark condensate; Dimensional deconstruction; Chiral symmetry breaking in Heavy-Light Mesons; Theory of UHE Cosmic Rays; Soft Nambu-Goldstone Boson model of Dark Matter.
Scientific career
Institutions	Fermilab
Thesis	Higgs scalars and the nonleptonic weak interactions (1977)
Doctoral advisor	Murray Gell-Mann

Christopher T. Hill (born June 19, 1951) is an American theoretical physicist, formerly of the Fermi National Accelerator Laboratory, who did undergraduate work in physics at M.I.T. (B.S., M.S., 1972), and graduate work at Caltech (Ph.D., 1977, Murray Gell-Mann). Hill's Ph.D. thesis, "Higgs Scalars and the Nonleptonic Weak Interactions" (1977) contains one of the first detailed discussions of the two-Higgs-doublet model and its impact upon weak interactions. His work mainly focuses on new physics that can be probed in laboratory experiments or cosmology.

Hill is an originator, with William A. Bardeen and Manfred Lindner, of the idea that the Higgs boson is composed of top and anti-top quarks. This emerges from the concept of the top quark infrared fixed point, with which Hill predicted (1981) that the top quark would be very heavy, contrary to most popular ideas at the time. The fixed point prediction lies within 20% of the observed top quark mass (1995). This implies that the top quarks may be strongly coupled at very short distances and could form a composite Higgs boson, which led to top quark condensates, topcolor, and dimensional deconstruction, a renormalizable lattice description of extra dimensions of space. The original minimal top condensation model predicted the Higgs boson mass to be about twice the observed value of 125 GeV, but extensions of the theory achieve concordance with both the Higgs boson and top quark masses. Several new heavy Higgs bosons, such as a b-quark scalar bound state, may be accessible to the LHC.

Hill coauthored (with Elizabeth H. Simmons) a comprehensive review of strong dynamical theories and electroweak symmetry breaking that has shaped many of the experimental searches for new physics at the Tevatron and LHC.

Heavy-light mesons contain a heavy quark and a light anti-quark, and provide a window on the chiral symmetry dynamics of a single light quark. Hill and Bardeen showed that the (spin) ${\displaystyle (0^{-},1^{-})}$ ground states are split from the ${\displaystyle (0^{+},1^{+})}$ parity partners by a universal mass gap of about ${\displaystyle ~\Delta M\approx 350{\text{ MeV,}}~}$ due to the light quark chiral symmetry breaking. This correctly predicted an abnormally long-lived resonance, the ${\displaystyle D_{s0^{+}}^{*}(2317)}$ (and the now confirmed ${\displaystyle D_{s1^{+}}^{*}(2460)}$), ten years before its discovery, and numerous decay modes which have been confirmed by experiment. Similar phenomena should be seen in the ${\displaystyle B_{s}}$ mesons and ${\displaystyle ccs,bcs,bbs}$ (heavy-heavy-strange baryons).

Hill is a contributor to the theory of topological interactions and, with collaborators, was first to obtain the full Wess-Zumino-Witten term for the standard model which describes the physics of the chiral anomaly in Lagrangians, including pseudoscalars, spin-1 vector mesons, and the ${\displaystyle W^{\pm }}$ and ${\displaystyle Z^{0}}$. The WZW term requires a non-trivial counter-term to map the "consistent" anomaly into the "covariant" anomaly, as dictated by the conserved currents of the standard model. With the full WZW-term, new anomalous interactions were revealed such as the ${\displaystyle \gamma \omega Z^{0}}$ vertex. This leads to ${\displaystyle \nu +X\rightarrow \nu +\gamma +X}$ where ${\displaystyle X}$ is a heavy nucleus, and may contribute to excess photons seen in low energy neutrino experiments. The result reproduces B+L violation by the anomaly in the standard model, and predicts numerous other anomalous processes. Hill has given a derivation of the coefficients of consistent and covariant chiral anomalies (even D), and Chern-Simons terms (odd D), without resorting to fermion loops, from the Dirac monopole construction and its generalization ("Dirac Branes") to higher dimensions.

Hill is an originator of cosmological models of dark energy and dark matter based upon ultra-low mass pseudo-Nambu-Goldstone bosons associated with symmetries of neutrino masses. He proposed that the cosmological constant is connected to the neutrino mass, as ${\displaystyle \Lambda \sim m_{\nu }^{4}}$ and developed modern theories of the origin of ultra-high-energy nucleons and neutrinos from grand unification relics. He has shown that a cosmic axion field will induce an effective oscillating electric dipole moment for any magnet.

In an unpublished talk at the Vancouver Workshop on Quantum Cosmology (May, 1990), Hill discussed possible roles for Nambu-Goldstone bosons in cosmology and suggested that a pseudo-Nambu-Goldstone boson might provide a "natural inflaton," the particle responsible for cosmic inflation. He noted that this required a spontaneously broken global symmetry, such as U(1), near the Planck scale, and explicit symmetry breaking near the Grand Unification Scale. The idea seemed ad hoc, however subsequent work on Weyl invariant theories offered a better rationale for a natural inflation scenario connected to Planck scale physics. Hill collaborated with Graham Ross and Pedro G. Ferreira and focused on spontaneously broken scale symmetry (or Weyl symmetry), where the scale of gravity (Planck mass) and the inflationary phase of the ultra-early universe are generated together as part of a unified phenomenon dubbed "inertial symmetry breaking." The Weyl symmetry breaking occurs because the Noether current is the derivative of a scalar operator, called the "kernal." During a period of pre-Planckian expansion any conserved current must red-shift to zero, hence the kernal approaches a constant value which determines the Planck mass and the Einstein-Hilbert action of General Relativity is emergent. The theory is in good agreement with cosmological observation.

Hill has returned to the issue of composite scalars in relativistic field theory, developing a novel analytic approach to bound states of chiral fermions by generalizing the Nambu--Jona-Lasinio model to non-pointlike interactions. He feels the most important challenge to the CERN LHC program is to determine if the Brout-Englert-Higgs boson is a pointlike fundamental particle or a composite bound state near the TeV energy scale. The former case may evidence some yet-to-be developed version of Supersymmetry; the latter case would imply new dynamics.

Academic Positions and Honors

• Distinguished Scientist at Fermilab (1979 - 2024);
• Head of the Fermilab Theoretical Physics Department (2005 - 2012);
• Visiting Scientist, CERN-TH, Geneva, Switzerland (1987-1988);
• Fellow of the American Physical Society (elected, 1989);
• Arthur H. Compton Lecturer, University of Chicago, Spring (1979);
• Visiting Scholar, Oxford University (1980);
• Professor of Physics (adjunct), University of Chicago, (1996–2000);
• Gambrinus Fellow, University of Dortmund, (2005);
• van Winter Lecturer, University of Kentucky (2009);
• Visiting Professor, Institut de Fisica Corpuscular, Valencia, Spain (2019)
• Honorary Fellow, University of Wisconsin, Madison (2024 - present).

Books and Articles

Hill has authored three popular books with Nobel laureate Leon Lederman about physics and cosmology, and the commissioning of the Large Hadron Collider.

• Symmetry and the Beautiful Universe, Christopher T. Hill and Leon M. Lederman, Prometheus Books (2005)
• Quantum Physics for Poets, Christopher T. Hill and Leon M. Lederman, Prometheus Books (2010)
• Beyond the God Particle, Christopher T. Hill and Leon M. Lederman, Prometheus Books (2013)
• Google Scholar Profile of Christopher T. Hill

References

1. "Murray Gell-Mann," Physics Today, (2020); https://physicstoday.scitation.org/doi/10.1063/PT.3.4480 (2020)
2. "Higgs Scalars and the Nonleptonic Weak Interactions" (1977)
3. Hill, Christopher T. (1 August 1981). "Quark and lepton masses from renormalization-group fixed points". Physical Review D. 24 (3): 691–703. Bibcode:1981PhRvD..24..691H. doi:10.1103/PhysRevD.24.691.
4. Bardeen, William A.; Hill, Christopher T.; Lindner, Manfred (1990). "Minimal dynamical symmetry breaking of the standard model". Phys. Rev. D. 41 (5): 1647–1660. Bibcode:1990PhRvD..41.1647B. doi:10.1103/PhysRevD.41.1647. PMID 10012522.
5. Hill, Christopher T. (1995). "Topcolor Assisted Technicolor". Phys. Lett. B. 345 (4): 483–489. arXiv:hep-ph/9411426. Bibcode:1995PhLB..345..483H. doi:10.1016/0370-2693(94)01660-5. S2CID 15093335.
6. Hill, Christopher T. (1991). "Topcolor: top quark condensation in a gauge extension of the standard model". Physics Letters B. 266 (3–4): 419–424. Bibcode:1991PhLB..266..419H. doi:10.1016/0370-2693(91)91061-Y. S2CID 121635635.
7. Hill, Christopher T.; Pokorski, Stefan; Wang, Jing (2001). "Gauge invariant effective Lagrangian for Kaluza-Klein modes". Phys. Rev. D. 64 (10): 105005. arXiv:hep-th/0104035. Bibcode:2001PhRvD..64j5005H. doi:10.1103/physrevd.64.105005. S2CID 7377062.
8. Hill, Christopher T. (4 April 2014). "Is the Higgs boson associated with Coleman-Weinberg dynamical symmetry breaking?". Physical Review D. 89 (7): 073003. arXiv:1401.4185. Bibcode:2014PhRvD..89g3003H. doi:10.1103/PhysRevD.89.073003. S2CID 119192830.
9. Hill, Christopher T.; Machado, Pedro; Thomsen, Anders; Turner, Jessica (2019). "Where are the Next Higgs Bosons?". Physical Review. D100 (1): 015051. arXiv:1904.04257. Bibcode:2019PhRvD.100a5051H. doi:10.1103/PhysRevD.100.015051. S2CID 104291827.
10. Hill, Christopher T.; Machado, Pedro; Thomsen, Anders; Turner, Jessica (2019). "Scalar Democracy". Physical Review. D100 (1): 015015. arXiv:1902.07214. Bibcode:2019PhRvD.100a5015H. doi:10.1103/PhysRevD.100.015015. S2CID 119193325.
11. Hill, Christopher T.; Simmons, Elizabeth H. (2003). "Strong dynamics and electroweak symmetry breaking". Phys. Rep. 381 (4–6): 235. arXiv:hep-ph/0203079. Bibcode:2003PhR...381..235H. doi:10.1016/S0370-1573(03)00140-6. S2CID 118933166. Archived from the original on 2019-05-03. Retrieved 2019-05-03.
12. Bardeen, William A.; Hill, Christopher T. (1994). "Chiral dynamics and heavy quark symmetry in a solvable toy field theoretic model". Physical Review D. 49 (1): 409–425. arXiv:hep-ph/9304265. Bibcode:1994PhRvD..49..409B. doi:10.1103/PhysRevD.49.409. PMID 10016779. S2CID 1763576.
13. Bardeen, William A.; Eichten, Estia; Hill, Christopher T. (2003). "Chiral multiplets of heavy-light mesons". Physical Review D. 68 (5): 054024. arXiv:hep-ph/0305049. Bibcode:2003PhRvD..68e4024B. doi:10.1103/PhysRevD.68.054024. S2CID 10472717.
14. Harvey, Jeffrey A.; Hill, Christopher T.; Hill, Richard (2007). "Standard Model Gauging of the Wess-Zumino-Witten Term: Anomalies, Global Currents and pseudo-Chern-Simons Interactions". Phys. Rev. D. 30 (8): 085017. arXiv:0712.1230. doi:10.1103/PhysRevD.77.085017.
15. C. T. Hill, "Dirac Branes and Anomalies/Chern-Simons terms in any D," arXiv:0907.1101 . For fermion loops see: "Lecture notes for massless spinor and massive spinor triangle diagrams," arXiv:hep-th/0601155 .
16. Frieman, Joshua A.; Hill, Christopher T.; Stebbins, Albert; Waga, Ioav (1995). "Cosmology with ultralight pseudo Nambu-Goldstone bosons". Phys. Rev. Lett. 75 (11): 2077–2080. arXiv:astro-ph/9505060. Bibcode:1995PhRvL..75.2077F. doi:10.1103/PhysRevLett.75.2077. PMID 10059208. S2CID 11755173.
17. Hill, Christopher T.; Schramm, David N.; Fry, James N. (1989). "Cosmological Structure Formation from Soft Topological Defects" (PDF). Comments on Nucl. Part. Phys. Vol. 19. pp. 25–39.
18. Hill, Christopher T.; Schramm, David N. (1 February 1985). "Ultrahigh-energy cosmic-ray spectrum". Physical Review D. 31 (3): 564–580. Bibcode:1985PhRvD..31..564H. doi:10.1103/PhysRevD.31.564. PMID 9955721.
19. Hill, Christopher T.; Schramm, David N.; Walker, Terry P. (1987). "Ultrahigh-Energy Cosmic Rays from Superconducting Cosmic Strings". Phys. Rev. D. 36 (4): 1007–1016. Bibcode:1987PhRvD..36.1007H. doi:10.1103/physrevd.36.1007. PMID 9958264.
20. Bhattacharjee, Pijushpani; Hill, Christopher T.; Schramm, David N. (1992). ""Grand unified theories," topological defects and ultrahigh-energy cosmic rays". Phys. Rev. Lett. 69 (4): 567–570. Bibcode:1992PhRvL..69..567B. doi:10.1103/PhysRevLett.69.567. hdl:2060/19920009031. PMID 10046974. S2CID 20633612.
21. Hill, Christopher T. (1983). "Monopolonium". Nuclear Physics B. 224 (3): 469–490. Bibcode:1983NuPhB.224..469H. doi:10.1016/0550-3213(83)90386-3. OSTI 1155484.
22. Hill, Christopher T. (2015). "Axion Induced Oscillating Electric Dipole Moments". Physical Review D. 224 (3): 111702. arXiv:1504.01295. Bibcode:2015PhRvD..91k1702H. doi:10.1103/PhysRevD.91.111702. OSTI 1212736. S2CID 96444192.
23. Hill, Christopher T. (2016). "Axion Induced Oscillating Electric Dipole Moment of the Electron". Physical Review D. 224 (3): 025007. arXiv:1508.04083. Bibcode:2016PhRvD..93b5007H. doi:10.1103/PhysRevD.93.025007. OSTI 1223242. S2CID 119221466.
24. Ferreira, Pedro G.; Hill, Christopher T.; Ross, Graham G. (8 February 2017). "Weyl current, scale-invariant inflation, and Planck scale generation". Physical Review D. 95 (4): 043507. arXiv:1610.09243. Bibcode:2017PhRvD..95d3507F. doi:10.1103/PhysRevD.95.043507. S2CID 119269154.
25. Ferreira, Pedro G.; Hill, Christopher T.; Ross, Graham G. (2018). "Inertial Spontaneous Symmetry Breaking and Quantum Scale Invariance". Physical Review D. 98 (11): 116012. arXiv:1801.07676. Bibcode:2018PhRvD..98k6012F. doi:10.1103/PhysRevD.98.116012. S2CID 119267087.
26. Hill, Christopher T.; Ross, Graham G. (2020). "Gravitational Contact Terms and the Physical Equivalence of Weyl Transformations in Effective Field Theory". Physical Review D. 102: 125014. arXiv:2009.14782. doi:10.1103/PhysRevD.102.125014. S2CID 222067042.
27. Hill, Christopher T. (2024). "Bilocal Field Theory for Composite Scalar Bosons". Entropy. 26 (2): 146. arXiv:2310.14750. Bibcode:2024Entrp..26..146H. doi:10.3390/e26020146.
28. Hill, Christopher T. (2024), "Nambu and Compositeness", arXiv:2401.08716
29. "APS Fellow Archive". American Physical Society. (search on year=1989 and institution=Fermi National Accelerator Laboratory)

External links

• Fermilab Theoretical Physics Department

• Living people
• 21st-century American physicists
• American particle physicists
• Fellows of the American Physical Society
• California Institute of Technology alumni
• 1951 births
• Massachusetts Institute of Technology School of Science alumni
• People associated with Fermilab
• People associated with CERN