We calculate the free energy, entropy and pressure of the Quark Gluon Plasma (QGP) at finite temperature and density with a given fraction of spin-up and spin-down quarks using a MIT bag model with corrections up to ${cal O} (g^4 ln g^2)$. The expres
sions for the specific heat and the spin susceptibility are derived in terms of Fermi momentum and temperature. The effects of interaction between the quarks on the properties of the QGP phase are also investigated. Within our phenomenological model, we estimate the transition temperature $T_c$ by constructing the phase boundary between the hadronic phase and the QGP phase. Finally, we compute the equation of state of the QGP and its dependence on the temperature and the density.
We calculate the neutrino mean free path with non-Fermi liquid (NFL) corrections in quark matter from scattering and absorption processes for both degenerate and nondegenerate neutrinos. We show that the mean free path decreases due to the non-Fermi
liquid corrections leading to $l_{mean}^{-1}sim[......+ .... C_F^2alpha_s^2ln(m_D/T)^2]$. These reduction results in higher rate of scattering.
We calculate pionic contribution to the relativistic Fermi Liquid parameters (RFLPs) using Chiral Effective Lagrangian. The RFLPs so determined are then used to calculate chemical potential, exchange and nuclear symmetry energies due to $pi$$N$ inter
action. We also evaluate two loop ring diagrams involving $sigma$, $omega$ and $pi$ meson exchanges and compare results with what one obtains from the relativistic Fermi Liquid theory (RFLT).
We calculate the dimensionless Fermi liquid parameters (FLPs), $F_{0,1}^{sym}$ and $F_{0,1}^{asym}$, for spin asymmetric dense quark matter. In general, the FLPs are infrared divergent due to the exchange of massless gluons. To remove such divergence
s, the Hard Density Loop (HDL) corrected gluon propagator is used. The FLPs so determined are then invoked to calculate magnetic properties such as magnetization $langle Mrangle$ and magnetic susceptibility $chi_M$ of spin polarized quark matter. Finally, we investigate the possibility of magnetic instability by studying the density dependence of $langle Mrangle$ and $chi_M$.
The expression for the spin susceptibility $chi$ of degenerate quark matter is derived with corrections upto $ {cal O}(g^4ln g^2)$. It is shown that at low density, $chi^{-1}$ changes sign and turns negative indicating a ferromagnetic phase transitio
n. To this order, we also calculate sound velocity $c_1$ and incompressibility $K$ with arbitrary spin polarization. The estimated values of $c_1$ and $K$ show that the equation of state of the polarized matter is stiffer than the unpolarized one. Finally we determine the finite temperature corrections to the exchange energy and derive corresponding results for the spin susceptibility.
We calculate the ground state energy of cold and dense spin polarized quark matter with corrections due to correlation energy $(E_{corr})$. Expressions for $E_{corr}$ both in the non-relativistic and ultra-relativistic regimes have been derived and c
ompared with the exchange and kinetic term present in the perturbation series. It is observed that the inclusion of correlation energy does not rule out the possibility of the ferromagnetic phase transition at low density within the model proposed by Tatsumicite{tatsumi00}. We also derive the spin stiffness constant in the high density limit of such a spin polarized matter.
We calculate the spin dependent Fermi liquid parameters (FLPs), single particle energies and energy densities of various spin states of polarized quark matter. The expressions for the incompressibility($K$) and sound velocity ($c_1$) in terms of the
spin dependent FLPs and polarization parameter $(xi)$ are derived. Estimated values of $K$ and $c_1$ reveal that the equation of state (EOS) of the polarized matter is stiffer than the unpolarized one. Finally we investigate the possibility of the spin polarization (ferromagnetism) phase transition.
We calculate relativistic Fermi liquid parameters (RFLPs) for the description of the properties of dense nuclear matter (DNM) using Effective Chiral Model. Analytical expressions of Fermi liquid parameters (FLPs) are presented both for the direct and
exchange contributions. We present a comparative study of perturbative calculation with mean field (MF) results. Moreover we go beyond the MF so as to estimate the pionic contribution to the FLPs. Finally, we use these parameters to estimate some of the bulk quantities like incompressibility, sound velocity, symmetry energy etc. for DNM interacting via exchange of $sigma$, $omega$ and $pi$ meson. In addition, we also calculate the energy densities and the binding energy curve for the nuclear matter. Results for the latter have been found to be consistent with two loop calculations reported recently within the same model.
