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| {{short description|Degenerate matter made from strange quarks}} | {{short description|Degenerate matter made from strange quarks}} | ||
| {{pp-move-indef}} | |||
| {{Refimprove|date=October 2017}} | {{Refimprove|date=October 2017}} | ||
| '''Strange matter''' |
'''Strange matter''' (or '''strange quark matter''') is ] containing ]s. In extreme environments, strange matter is hypothesized to occur in the core of ]s, or, more speculatively, as isolated droplets that may vary in size from ]s (]s) to kilometers, as in the hypothetical ]. At high enough density, strange matter is expected to be ].{{citation needed|date=February 2019}} | ||
| {{citation needed|date=February 2019}} | |||
| Ordinary ], also referred to as atomic matter, is composed of atoms, with nearly all matter concentrated in the atomic nuclei. ] is a liquid composed of ]s and ]s, and they are themselves composed of ] and ]. Quark matter is a ] composed entirely of ]s. |
Ordinary ], also referred to as atomic matter, is composed of atoms, with nearly all matter concentrated in the atomic nuclei. ] is a liquid composed of ]s and ]s, and they are themselves composed of ] and ]. Quark matter is a ] composed entirely of ]s. When quark matter does not contain strange quarks, it is sometimes referred to as non-strange quark matter. | ||
| == |
==Context== | ||
| In ] and ], the term 'strange matter' is used in two different contexts, one broader and the other more specific and hypothetical:<ref name= |
In ] and ], the term 'strange matter' is used in two different contexts, one broader and the other more specific and hypothetical:<ref name="Madsen:1998">{{Cite book |last1=Madsen |first1=Jes |title=Hadrons in Dense Matter and Hadrosynthesis |year=1999 |isbn=978-3-540-65209-0 |series=Lecture Notes in Physics |volume=516 |pages=162–203 |chapter=Physics and astrophysics of strange quark matter |doi=10.1007/BFb0107314 |arxiv=astro-ph/9809032 |s2cid=16566509 }}</ref><ref name="Weber">{{Cite journal |last1=Weber |first1=F. |year=2005 |title=Strange quark matter and compact stars |journal=Progress in Particle and Nuclear Physics |volume=54 |issue=1 |pages=193–288 |arxiv=astro-ph/0407155 |bibcode=2005PrPNP..54..193W |doi=10.1016/j.ppnp.2004.07.001 |s2cid=15002134 }}.</ref> | ||
| # In the broader context, our current understanding of the ] predicts that strange matter could be created when nuclear matter (made of ] and ]) is compressed beyond a critical density. At this critical pressure and density, the protons and neutrons dissociate into quarks, yielding quark matter and potentially strange matter. | # In the broader context, our current understanding of the ] predicts that strange matter could be created when nuclear matter (made of ] and ]) is compressed beyond a critical density. At this critical pressure and density, the protons and neutrons dissociate into quarks, yielding quark matter and potentially strange matter. | ||
| # |
# A more specific hypothesis is that quark matter is the true ground state of all matter, and thus more stable than ordinary nuclear matter. This idea is known as the "strange matter hypothesis", or the ]–] assumption.<ref name="Bodmer">{{Cite journal |last1=Bodmer |first1=A. R. |date=September 1971 |title=Collapsed Nuclei |url=https://ui.adsabs.harvard.edu/abs/1971PhRvD...4.1601B/abstract |journal=Physical Review D |volume=4 |issue=6 |pages=1601–1606 |bibcode=1971PhRvD...4.1601B |doi=10.1103/PhysRevD.4.1601 |access-date=2022-03-22 |archive-date=2022-01-20 |archive-url=https://web.archive.org/web/20220120042524/https://ui.adsabs.harvard.edu/abs/1971PhRvD...4.1601B/abstract |url-status=live }}</ref><ref name="Witten">{{Cite journal |last=Witten |first=Edward |author-link=Edward Witten |date=July 1984 |title=Cosmic separation of phases |url=https://ui.adsabs.harvard.edu/abs/1984PhRvD..30..272W |journal=Physical Review D |volume=30 |issue=2 |pages=272–285 |bibcode=1984PhRvD..30..272W |doi=10.1103/PhysRevD.30.272 |access-date=2022-03-22 |archive-date=2022-01-25 |archive-url=https://web.archive.org/web/20220125070503/https://ui.adsabs.harvard.edu/abs/1984PhRvD..30..272W |url-status=live }}</ref> Under this hypothesis, the nuclei of the atoms we see around us are only ], even when the external critical pressure is zero, and given enough time (or the right stimulus) the nuclei would decay into stable droplets of strange matter. Droplets of strange matter are also referred to as strangelets. | ||
| == |
== Stability of strange matter only at high pressure == | ||
| In the general context, strange matter might occur inside neutron stars, if the pressure at their core is high enough (i.e. above the critical pressure). At the sort of densities and high pressures we expect in the center of a neutron star, the quark matter would probably be strange matter. It could conceivably be non-strange quark matter, if the effective mass of the strange quark were too high. ] quarks and heavier quarks would only occur at much higher densities. | In the general context, strange matter might occur inside neutron stars, if the pressure at their core is high enough to provide a sufficient gravitational force (i.e. above the critical pressure). At the sort of densities and high pressures we expect in the center of a neutron star, the quark matter would probably be strange matter. It could conceivably be non-strange quark matter, if the effective mass of the strange quark were too high. ] quarks and heavier quarks would only occur at much higher densities. | ||
| Strange matter comes about as a way to relieve ]. The ] forbids fermions such as quarks from occupying the same position and energy level. When the particle density is high enough that all energy levels below the available thermal energy are already occupied, increasing the density further requires raising some to higher, unoccupied energy levels. This need for energy to cause compression manifests as a pressure. |
Strange matter comes about as a way to relieve ]. The ] forbids fermions such as quarks from occupying the same position and energy level. When the particle density is high enough that all energy levels below the available thermal energy are already occupied, increasing the density further requires raising some to higher, unoccupied energy levels. This need for energy to cause compression manifests as a pressure. Neutrons consist of twice as many ]s (charge −{{sfrac|1|3}} ]) as ]s (charge +{{sfrac|2|3}} ''e''), so the degeneracy pressure of down quarks usually dominates electrically neutral quark matter. However, when the required energy level is high enough, an alternative becomes available: half of the down quarks can be transmuted to strange quarks (charge −{{sfrac|1|3}} ''e''). The higher rest mass of the strange quark costs some energy, but by opening up an additional set of energy levels, the average energy per particle can be lower,{{r|Madsen:1998|p=5}} making strange matter more stable than non-strange quark matter. | ||
| A neutron star with a quark matter core is often{{r|Madsen:1998|Weber}} called a hybrid star. However, it is |
A neutron star with a quark matter core is often{{r|Madsen:1998|Weber}} called a hybrid star. However, it is difficult to know whether hybrid stars really exist in nature because physicists currently have little idea of the likely value of the critical pressure or density. It seems plausible that the transition to quark matter will already have occurred when the separation between the ]s becomes much smaller than their size, so the critical density must be less than about 100 times nuclear saturation density. But a more precise estimate is not yet available, because the ] that governs the behavior of quarks is mathematically intractable, and numerical calculations using ] are currently blocked by the fermion ]. | ||
| One major area of activity in neutron star physics is the attempt to find observable signatures by which we could tell whether neutron stars have quark matter (probably strange matter) in their core. <!-- See ] --> | One major area of activity in neutron star physics is the attempt to find observable signatures by which we could tell whether neutron stars have quark matter (probably strange matter) in their core. <!-- See ] --> | ||
| During the merger of two neutron stars, strange matter may be ejected out into the space around the stars, which may allow for the studying of strange matter. However, the rate at which strange matter decays is unknown, and there are very few binary pairs of neutron stars nearby to the Solar System, which could make the official discovery of strange matter very difficult. | |||
| ⚫ | == |
||
| ⚫ | ==Stability of strange matter at zero pressure== | ||
| ⚫ | If the "strange matter hypothesis" is true then nuclear matter is metastable against decaying into strange matter. The lifetime for spontaneous decay is very long, so we do not see this decay process happening around us.<ref name='Witten' /> However, under this hypothesis there should be strange matter in the universe: | ||
| ⚫ | If the "]" is true, then nuclear matter is metastable against decaying into strange matter. The lifetime for spontaneous decay is very long, so we do not see this decay process happening around us.<ref name='Witten' /> However, under this hypothesis there should be strange matter in the universe: | ||
| # Quark stars (often called "strange stars") consist of quark matter from their core to their surface. They would be several kilometers across, and may have a very thin crust of nuclear matter.<ref name='Weber' /> | # Quark stars (often called "strange stars") consist of quark matter from their core to their surface. They would be several kilometers across, and may have a very thin crust of nuclear matter.<ref name='Weber' /> | ||
| # ] are small pieces of strange matter, perhaps as small as nuclei. They would be produced when strange stars are formed or collide, or when a nucleus decays.<ref name='Madsen:1998' /> | # ] are small pieces of strange matter, perhaps as small as nuclei. They would be produced when strange stars are formed or collide, or when a nucleus decays.<ref name='Madsen:1998' /> | ||
| == |
==See also== | ||
| * {{annotated link|Exotic matter}} | * {{annotated link|Exotic matter}} | ||
| * {{annotated link|Negative matter}} | |||
| * {{annotated link|Quark matter}} | |||
| * {{annotated link|Quark star}} | * {{annotated link|Quark star}} | ||
| * |
* ] – subatomic signature | ||
| * {{annotated link|Strangelet}} | * {{annotated link|Strangelet}} | ||
| * {{annotated link|Quark}} | * {{annotated link|Quark}} | ||
| * {{annotated link|QCD matter}} | * {{annotated link|QCD matter}} | ||
| == |
==References== | ||
| {{reflist}} | {{reflist}} | ||
| {{Phase of matter}} | {{Phase of matter}} | ||
| {{Stellar core collapse}} | |||
| ] | ] | ||
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| ] | ] | ||
| ] | |||
Latest revision as of 13:28, 26 December 2023
Degenerate matter made from strange quarks | This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Strange matter" – news · newspapers · books · scholar · JSTOR (October 2017) (Learn how and when to remove this message) |
Strange matter (or strange quark matter) is quark matter containing strange quarks. In extreme environments, strange matter is hypothesized to occur in the core of neutron stars, or, more speculatively, as isolated droplets that may vary in size from femtometers (strangelets) to kilometers, as in the hypothetical strange stars. At high enough density, strange matter is expected to be color superconducting.
Ordinary matter, also referred to as atomic matter, is composed of atoms, with nearly all matter concentrated in the atomic nuclei. Nuclear matter is a liquid composed of neutrons and protons, and they are themselves composed of up and down quarks. Quark matter is a condensed form of matter composed entirely of quarks. When quark matter does not contain strange quarks, it is sometimes referred to as non-strange quark matter.
Context
In particle physics and astrophysics, the term 'strange matter' is used in two different contexts, one broader and the other more specific and hypothetical:
- In the broader context, our current understanding of the laws of nature predicts that strange matter could be created when nuclear matter (made of protons and neutrons) is compressed beyond a critical density. At this critical pressure and density, the protons and neutrons dissociate into quarks, yielding quark matter and potentially strange matter.
- A more specific hypothesis is that quark matter is the true ground state of all matter, and thus more stable than ordinary nuclear matter. This idea is known as the "strange matter hypothesis", or the Bodmer–Witten assumption. Under this hypothesis, the nuclei of the atoms we see around us are only metastable, even when the external critical pressure is zero, and given enough time (or the right stimulus) the nuclei would decay into stable droplets of strange matter. Droplets of strange matter are also referred to as strangelets.
Stability of strange matter only at high pressure
In the general context, strange matter might occur inside neutron stars, if the pressure at their core is high enough to provide a sufficient gravitational force (i.e. above the critical pressure). At the sort of densities and high pressures we expect in the center of a neutron star, the quark matter would probably be strange matter. It could conceivably be non-strange quark matter, if the effective mass of the strange quark were too high. Charm quarks and heavier quarks would only occur at much higher densities.
Strange matter comes about as a way to relieve degeneracy pressure. The Pauli exclusion principle forbids fermions such as quarks from occupying the same position and energy level. When the particle density is high enough that all energy levels below the available thermal energy are already occupied, increasing the density further requires raising some to higher, unoccupied energy levels. This need for energy to cause compression manifests as a pressure. Neutrons consist of twice as many down quarks (charge −1/3 e) as up quarks (charge +2/3 e), so the degeneracy pressure of down quarks usually dominates electrically neutral quark matter. However, when the required energy level is high enough, an alternative becomes available: half of the down quarks can be transmuted to strange quarks (charge −1/3 e). The higher rest mass of the strange quark costs some energy, but by opening up an additional set of energy levels, the average energy per particle can be lower, making strange matter more stable than non-strange quark matter.
A neutron star with a quark matter core is often called a hybrid star. However, it is difficult to know whether hybrid stars really exist in nature because physicists currently have little idea of the likely value of the critical pressure or density. It seems plausible that the transition to quark matter will already have occurred when the separation between the nucleons becomes much smaller than their size, so the critical density must be less than about 100 times nuclear saturation density. But a more precise estimate is not yet available, because the strong interaction that governs the behavior of quarks is mathematically intractable, and numerical calculations using lattice QCD are currently blocked by the fermion sign problem.
One major area of activity in neutron star physics is the attempt to find observable signatures by which we could tell whether neutron stars have quark matter (probably strange matter) in their core.
During the merger of two neutron stars, strange matter may be ejected out into the space around the stars, which may allow for the studying of strange matter. However, the rate at which strange matter decays is unknown, and there are very few binary pairs of neutron stars nearby to the Solar System, which could make the official discovery of strange matter very difficult.
Stability of strange matter at zero pressure
If the "strange matter hypothesis" is true, then nuclear matter is metastable against decaying into strange matter. The lifetime for spontaneous decay is very long, so we do not see this decay process happening around us. However, under this hypothesis there should be strange matter in the universe:
- Quark stars (often called "strange stars") consist of quark matter from their core to their surface. They would be several kilometers across, and may have a very thin crust of nuclear matter.
- Strangelets are small pieces of strange matter, perhaps as small as nuclei. They would be produced when strange stars are formed or collide, or when a nucleus decays.
See also
- Exotic matter – Physics term for multiple concepts
- Quark star – Compact exotic star which forms matter consisting mostly of quarks
- Strangeness and quark–gluon plasma – subatomic signature
- Strangelet – Type of hypothetical particle
- Quark – Elementary particle, main constituent of matter
- QCD matter – Hypothetical phases of matter
References
- ^ Madsen, Jes (1999). "Physics and astrophysics of strange quark matter". Hadrons in Dense Matter and Hadrosynthesis. Lecture Notes in Physics. Vol. 516. pp. 162–203. arXiv:astro-ph/9809032. doi:10.1007/BFb0107314. ISBN 978-3-540-65209-0. S2CID 16566509.
- ^ Weber, F. (2005). "Strange quark matter and compact stars". Progress in Particle and Nuclear Physics. 54 (1): 193–288. arXiv:astro-ph/0407155. Bibcode:2005PrPNP..54..193W. doi:10.1016/j.ppnp.2004.07.001. S2CID 15002134..
- Bodmer, A. R. (September 1971). "Collapsed Nuclei". Physical Review D. 4 (6): 1601–1606. Bibcode:1971PhRvD...4.1601B. doi:10.1103/PhysRevD.4.1601. Archived from the original on 2022-01-20. Retrieved 2022-03-22.
- ^ Witten, Edward (July 1984). "Cosmic separation of phases". Physical Review D. 30 (2): 272–285. Bibcode:1984PhRvD..30..272W. doi:10.1103/PhysRevD.30.272. Archived from the original on 2022-01-25. Retrieved 2022-03-22.
| States of matter (list) | ||
|---|---|---|
| State |  | |
| Low energy | ||
| High energy | ||
| Other states | ||
| Phase transitions |
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| Quantities | ||
| Concepts | ||
| Stellar core collapse | ||
|---|---|---|
| Stars |  | |
| Stellar processes | ||
| Collapse | ||
| Supernovae | ||
| Compact and exotic objects | ||
| Particles, forces, and interactions | ||
| Quantum theory | ||
| Degenerate matter | ||
| Related topics | ||
