Transport Processes in Matter at High Temperatures and Densities

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In late stages of stellar evolution, the matter inside stars is at high-temperatures and densities. Under such conditions, various phenomena that cannot be observed in the laboratory on Earth could be easily realized. In the present research, the following elementary processes inside neutron-star matter are studied.First, even weakly-interacting particles, which are hard to produce in the laboratory on Earth (i.e., such particles constitute the dark matter in the universe), could be copiously produced under high-temperature and high-density conditions. The rate of thermal production of axions in neutron-star matter is calculated. Acomparison with surface temperature observations of neutron stars with X-ray satellites will constrain the properties of the axion, which remains one of the strongest candidates for dark matter.While neutrinos are also weakly-interacting particles, they may be trapped inside stars due to scattering by stellar matter when temperature and density are high. The … More neutrino "opacity" is calculated, which expresses the degree to which scattering occurs during the formation of a neutron star in a supernova explosion. The result may be used to determine whether a kaon-condensed phase appears and whether the neutron star remains gravitationally stable. A possible existence of kaon-condensed phase inside neutron stars could be detected by observing the surface temperature of neutron stars.At present, artificial satellites, the space shuttle, the space station, etc., are used to conduct scientific experiments and to synthesize new materials under ultra-high vacuum and microgravity environments. On the other hand, matter exists under various conditions in such environments as the early universe, supernova explosion and interstellar space. Various physical quantities, such as gravitational acceleration, temperature, pressure, mass density, electric and magnetic field strengths, energy, Fermi temperature, superfluidity/superconductivity transition temperature, are reviewed under space environments and they are compared with those under the conditions in the laboratory on Earth in connection with the syntheses of new materials. Less