We study the superfluid properties of two-dimensional spin-population-imbalanced Fermi gases to explore the interplay between the Berezinskii-Kosterlitz-Thouless (BKT) phase transition and the possible instability towards the Fulde-Ferrell (FF) state
. By the mean-field approximation together with quantum fluctuations, we obtain phase diagrams as functions of temperature, chemical potential imbalance and binding energy. We find that the fluctuations change the mean-field phase diagram significantly. We also address possible effects of the phase separation and/or the anisotropic FF phase to the BKT mechanism. The superfluid density tensor of the FF state is obtained, and its transverse component is found always vanishing. This causes divergent fluctuations and possibly precludes the existence of the FF state at any non-zero temperature.
The temperature dependence of the thermodynamic potential of quantum chromodynamics (QCD), the specific heat, and the quark effective mass are calculated for imbalanced quark matter in the limit of a large number of quark flavors (large-$N_F$), which
corresponds to the random phase approximation. Also a generalization of the relativistic Landau effective-mass relation in the imbalanced case is given, which is then applied to this thermodynamic potential.
The thermal evolution of isothermal neutron stars is studied with matter both in the hadronic phase as well as in the mixed phase of hadronic matter and strange quark matter. In our models, the dominant early-stage cooling process is neutrino emissio
n via the direct Urca process. As a consequence, the cooling curves fall too fast compared to observations. However, when superfluidity is included, the cooling of the neutron stars is significantly slowed down. Furthermore, we find that the cooling curves are not very sensitive to the precise details of the mixing between the hadronic phase and the quark phase and also of the pairing that leads to superfluidity.
The thermodynamic consistency of quasiparticle boson system with effective mass $m^*$ and zero chemical potential is studied. We take the quasiparticle gluon plasma model as a toy model. The failure of previous treatments based on traditional partial
derivative is addressed. We show that a consistent thermodynamic treatment can be applied to such boson system provided that a new degree of freedom $m^*$ is introduced in the partial derivative calculation. A pressure modification term different from the vacuum contribution is derived based on the new independent variable $m^*$. A complete and self-consistent thermodynamic treatment for quasiparticle system, which can be widely applied to effective mass models, has been constructed.
The equations of state for neutron matter, strange and non-strange hadronic matter in a chiral SU(3) quark mean field model are applied in the study of slowly rotating neutron stars and hadronic stars. The radius, mass, moment of inertia, and other p
hysical quantities are carefully examined. The effect of nucleon crust for the strange hadronic star is exhibited. Our results show the rotation can increase the maximum mass of compact stars significantly. For big enough mass of pulsar which can not be explained as strange hadronic star, the theoretical approaches to increase the maximum mass are addressed.
We examine the effect of the thermal vacuum on the power spectrum of inflation by using the thermal field dynamics. We find that the thermal effect influences the CMB anisotropy at large length scale. After removing the divergence by using the hologr
aphic cutoff, we observe that the thermal vacuum explains well the observational CMB result at low multipoles. This shows that the temperature dependent factor should be considered in the study of power spectrum in inflation, especially at large length scale.
We study the Hawking radiation of (4+n)-dimensional Schwarzschild black hole imbedded in the space-time with positive cosmological constant. The greybody and energy emission rates of scalars, fermions, bosons, and gravitons are calculated in the full
range of energy. The valuable information on the dimensions and curvature of space-time is revealed. Furthermore, we investigate the entropy radiated and lost by black hole. We find their ratio near unit in favor of the Bekensteins conjecture.
The ambiguities and inconsistencies in previous thermodynamic treatments for the quark mass density-dependent model are addressed. A new treatment is suggested to obtain the self-consistent results. A new independent variable of effective mass is int
roduced to make the traditional thermodynamic calculation with partial derivative still practicable. The contribution from physical vacuum has been discussed. We find that the properties of strange quark matter given by quark mass density-dependent model are nearly the same as those obtained by MIT bag model after considering the contribution of the physical vacuum.
We investigate the effect of the bulk contents in the DGP braneworld on the evolution of the universe. We find that although the pure DGP model cannot accommodate the transition of the effective equation of state of dark energy, once the bulk matter
T^5_5 is considered, the modified model can realize the w_{eff} crossing -1. However this transition of the equation of state cannot be realized by just considering bulk-brane energy exchange or the GB effect while the bulk matter contribution is not included. T^5_5 plays the major role in the modified DGP model to have the w crossing -1 behavior. We show that our model can describe the super-acceleration of our universe with the equation of state of the effective dark energy and the Hubble parameter in agreement with observations.
The thermodynamics with medium effects expressed by the temperature- and density-dependent effective mass of quasiparticle is studied. Series difficulties and many wrangles in references due to the extraordinary parameter dependence are addressed. A
new independent intrinsic degree of freedom of quasiparticle $m^*$ in the equation of reversible process is introduced to clear the ambiguity. We prove all results are self-consistent.
