17 research outputs found

### Heavy Quark Potential in a static and strong homogeneous magnetic field

We have investigated the properties of quarkonia in a thermal QCD medium in
the background of strong magnetic field. For that purpose, we employ the
Schwinger proper-time quark propagator in the lowest Landau level to calculate
the one-loop gluon self-energy, which in the sequel gives the the effective
gluon propagator. As an artifact of strong magnetic field approximation
($eB>>T^2$ and $eB>>m^2$), the Debye mass for massless flavors is found to
depend only on the magnetic field which is the dominant scale in comparison to
the scales prevalent in the thermal medium. However, for physical quark masses,
it depends on both magnetic field and temperature in a low temperature and high
magnetic field but the temperature dependence is very meagre and becomes
independent of temperature beyond a certain temperature and magnetic field.
With the above mentioned ingredients, the potential between heavy quark ($Q$)
and anti-quark ($\bar Q$) is obtained in a hot QCD medium in the presence of
strong magnetic field by correcting both short and long range components of the
potential in real-time formalism. It is found that the long range part of the
quarkonium potential is affected much more by magnetic field as compared to the
short range part. This observation facilitates us to estimate the magnetic
field beyond which the potential will be too weak to bind $Q\bar Q$ together.
For example, the $J/\psi$ is dissociated at $eB \sim$ 10 $m_\pi^2$ and
$\Upsilon$ is dissociated at $eB \sim$ 100 $m_\pi^2$ whereas its excited
states, $\psi^\prime$ and $\Upsilon^\prime$ are dissociated at smaller magnetic
field $eB= m_\pi^2$, $13 m_\pi^2$, respectively.Comment: 20 pages, 5 figure

### Strong CP violation and chiral symmetry breaking in hot and dense quark matter

We investigate chiral symmetry breaking and strong CP violation effects in
the phase diagram of strongly interacting matter. We demonstrate the effect of
strong CP violating terms on the phase structure at finite temperature and
densities in a 3-flavor Nambu-Jona-Lasinio (NJL) model including the
Kobayashi-Maskawa-t'Hooft (KMT) determinant term. This is investigated using an
explicit structure for the ground state in terms of quark-antiquark condensates
for both in the scalar and the pseudoscalar channels. CP restoring transition
with temperature at zero baryon density is found to be a second order
transition at $\theta = \pi$ while the same at finite chemical potential and
small temperature turns out to be a first order transition. Within the model,
the tri-critical point turns out to be $(T_c,\mu_c)\simeq(273,94)$ MeV at
$\theta = \pi$ for such a transition.Comment: 10 pages, 12 figure

### Chiral symmety breaking in 3-flavor Nambu-Jona Lasinio model in magnetic background

Effect of magnetic field on chiral symmetry breaking in a 3-flavor Nambu Jona
Lasinio (NJL) model at finite temperature and densities is considered here
using an explicit structure of ground state in terms of quark and antiquark
condensates. While at zero chemical potential and finite temperature, magnetic
field enhances the condensates, at zero temperature, the critical chemical
potential decreases with increasing magnetic field.Comment: Talk given at ICPAQGP-2010, Dec 6-10, 2010, Goa, India, 4 pages, 4
figure

### Violation of Wiedemann-Franz Law for Hot Hadronic Matter created at NICA, FAIR and RHIC Energies using Non-extensive Statistics

We present here the computation of electrical and thermal conductivity by
solving the Boltzmann transport equation in relaxation time approximation. We
use the $q$-generalized Boltzmann distribution function to incorporate the
effects of non-extensivity. The behaviour of these quantities with changing
temperature and baryochemical potential has been studied as the system slowly
moves towards thermodynamic equilibrium. We have estimated the Lorenz number at
NICA, FAIR and the top RHIC energies and studied as a function of temperature,
baryochemical potential and the non-extensive parameter, $q$. We have observed
that Wiedemann-Franz law is violated for a non-extensive hadronic phase as well
as for an equilibrated hadron gas at high temperatures.Comment: Same as the published versio

### Centrality dependence of Electrical and Hall conductivity at RHIC and LHC energies for a Conformal System

In this work, we study electrical conductivity and Hall conductivity in the
presence of electromagnetic field using Relativistic Boltzmann Transport
Equation with Relaxation Time Approximation. We evaluate these transport
coefficients for a strongly interacting system consisting of nearly massless
particles which is similar to Quark-Gluon Plasma and is likely to be formed in
heavy-ion collision experiments. We explicitly include the effects of magnetic
field in the calculation of relaxation time. The values of magnetic field are
obtained for all the centrality classes of Au+Au collisions at $\sqrt {s_{\rm
NN}} =$ 200 GeV and Pb+Pb collisions at $\sqrt {s_{\rm NN}} =$ 2.76 TeV. We
consider the three lightest quark flavors and their corresponding antiparticles
in this study. We estimate the temperature dependence of the electrical
conductivity and Hall conductivity for different strengths of magnetic field.
We observe a significant dependence of temperature on electrical and Hall
conductivity in the presence of magnetic field.Comment: Same as the published version in EPJ

### BCS BEC crossover and phase structure of relativistic system: a variational approach

We investigate here the BCS BEC crossover in relativistic systems using a
variational construct for the ground state and the minimization of the
thermodynamic potential. This is first studied in a four fermion point
interaction model and with a BCS type ansatz for the ground state with fermion
pairs. It is shown that the antiparticle degrees of freedom play an important
role in the BCS BEC crossover physics, even when the ratio of fermi momentum to
the mass of the fermion is small. We also consider the phase structure for the
case of fermion pairing with imbalanced populations. Within the ansatz,
thermodynamically stable gapless modes for both fermions and anti fermions are
seen for strong coupling in the BEC regime. We further investigate the effect
of fluctuations of the condensate field by treating it as a dynamical field and
generalize the BCS ansatz to include quanta of the condensate field also in a
boson fermion model with quartic self interaction of the condensate field. It
is seen that the critical temperature decreases with inclusion of fluctuations.Comment: 18 pages, 13 figures, one more section added, title modified, version
to appear in Phys Rev