Editing State of matter (section)

==High-energy states==

===Degenerate matter===
{{Main|Degenerate matter}}

Under extremely high pressure, as in the cores of dead stars, ordinary matter undergoes a transition to a series of exotic states of matter collectively known as [[degenerate matter]], which are supported mainly by quantum mechanical effects. In physics, "degenerate" refers to two states that have the same energy and are thus interchangeable. Degenerate matter is supported by the [[Pauli exclusion principle]], which prevents two [[fermion]]ic particles from occupying the same quantum state. Unlike regular plasma, degenerate plasma expands little when heated, because there are simply no momentum states left. Consequently, degenerate stars collapse into very high densities. More massive degenerate stars are smaller, because the gravitational force increases, but pressure does not increase proportionally.

[[Degenerate matter#Electron degeneracy|Electron-degenerate matter]] is found inside [[white dwarf]] stars. Electrons remain bound to atoms but are able to transfer to adjacent atoms. [[Degenerate matter#Neutron degeneracy|Neutron-degenerate matter]] is found in [[neutron star]]s. Vast gravitational pressure compresses atoms so strongly that the electrons are forced to combine with protons via inverse beta-decay, resulting in a superdense conglomeration of neutrons. Normally free [[neutron]]s outside an atomic nucleus will [[Free neutron decay|decay]] with a half life of approximately 10 minutes, but in a neutron star, the decay is overtaken by inverse decay. Cold degenerate matter is also present in planets such as [[Jupiter]] and in the even more massive [[brown dwarf]]s, which are expected to have a core with [[metallic hydrogen]]. Because of the degeneracy, more massive brown dwarfs are not significantly larger. In metals, the electrons can be modeled as a degenerate gas moving in a lattice of non-degenerate positive ions.

===Quark matter===
{{Main|QCD matter}}

In regular cold matter, [[quark]]s, fundamental particles of nuclear matter, are confined by the [[strong force]] into [[hadron]]s that consist of 2–4 quarks, such as protons and neutrons. Quark matter or quantum chromodynamical (QCD) matter is a group of phases where the strong force is overcome and quarks are deconfined and free to move. Quark matter phases occur at extremely high densities or temperatures, and there are no known ways to produce them in equilibrium in the laboratory; in ordinary conditions, any quark matter formed immediately undergoes radioactive decay.

[[Strange matter]] is a type of [[quark matter]] that is suspected to exist inside some neutron stars close to the [[Tolman–Oppenheimer–Volkoff limit]] (approximately 2–3 [[solar mass]]es), although there is no direct evidence of its existence. In strange matter, part of the energy available manifests as [[strange quark]]s, a heavier analogue of the common [[down quark]]. It may be stable at lower energy states once formed, although this is not known.

[[Quark–gluon plasma]] is a very high-temperature phase in which [[quark]]s become free and able to move independently, rather than being perpetually bound into particles, in a sea of [[gluon]]s, subatomic particles that transmit the [[strong interaction|strong force]] that binds quarks together. This is analogous to the liberation of electrons from atoms in a plasma. This state is briefly attainable in extremely high-energy heavy ion collisions in [[particle accelerator]]s, and allows scientists to observe the properties of individual quarks. Theories predicting the existence of quark–gluon plasma were developed in the late 1970s and early 1980s,<ref>{{Cite book|last=Satz|first=H.|url=https://books.google.com/books?id=OY8uAAAAIAAJ|title=Statistical Mechanics of Quarks and Hadrons: Proceedings of an International Symposium Held at the University of Bielefeld, F.R.G., August 24–31, 1980|date=1981|publisher=North-Holland|isbn=978-0-444-86227-3|language=en}}</ref> and it was detected for the first time in the laboratory at CERN in the year 2000.<ref>{{cite arXiv|last1=Heinz|first1=Ulrich|last2=Jacob|first2=Maurice|date=2000-02-16|title=Evidence for a New State of Matter: An Assessment of the Results from the CERN Lead Beam Programme|eprint=nucl-th/0002042}}</ref><ref>{{Cite news|last=Glanz|first=James|date=2000-02-10|title=Particle Physicists Getting Closer To the Bang That Started It All|language=en-US|work=The New York Times|url=https://www.nytimes.com/2000/02/10/world/particle-physicists-getting-closer-to-the-bang-that-started-it-all.html|access-date=2020-05-10|issn=0362-4331}}</ref> Unlike plasma, which flows like a gas, interactions within QGP are strong and it flows like a liquid.

At high densities but relatively low temperatures, quarks are theorized to form a quark liquid whose nature is presently unknown. It forms a distinct [[Color–flavor locking|color-flavor locked]] (CFL) phase at even higher densities. This phase is [[superconductive]] for color charge. These phases may occur in [[neutron star]]s but they are presently theoretical.

===Color-glass condensate===
{{Main|Color-glass condensate}}

Color-glass condensate is a type of matter theorized to exist in atomic nuclei traveling near the speed of light. According to Einstein's theory of relativity, a high-energy nucleus appears length contracted, or compressed, along its direction of motion. As a result, the gluons inside the nucleus appear to a stationary observer as a "gluonic wall" traveling near the speed of light. At very high energies, the density of the gluons in this wall is seen to increase greatly. Unlike the quark–gluon plasma produced in the collision of such walls, the color-glass condensate describes the walls themselves, and is an intrinsic property of the particles that can only be observed under high-energy conditions such as those at [[Relativistic Heavy Ion Collider]] (RHIC) and possibly at the [[Large Hadron Collider]] (LHC) as well.

=== Very high energy states ===
Various theories predict new states of matter at very high energies. An unknown state has created the [[baryon asymmetry]] in the universe, but little is known about it. In [[string theory]], a [[Hagedorn temperature]] is predicted for superstrings at about 10<sup>30</sup> K, where superstrings are copiously produced. At [[Planck temperature]] (10<sup>32</sup> K), gravity becomes a significant force between individual particles. No current theory can describe these states and they cannot be produced with any foreseeable experiment. However, these states are important in [[cosmology]] because the universe may have passed through these states in the [[Big Bang]].