We confront admixture of dark matter inside neutron star using gravitational wave constraints coming from binary neutron star merger. We consider a relativistic mean field model including σ − ω − ρ meson interaction with NL3 parameterization. We study fermionic dark matter interacting with nucleonic matter via Higgs portal mechanism. We show that admixture of dark matter inside the neutron star soften the equation state and lower the value of tidal deformability. Gravitational wave GW170817 observation puts an upper bound on tidal deformability of a binary neutron star with low spin prior at 90% confidence level, which disfavors stiff equation of state such as Walecka model with NL3 parameterization. However, we show that Walecka model with NL3 parameterization with a fermionic dark matter component satisfy the tidal deformability bound coming from the GW170817 observation. * arpan@prl.res.in †
Very strong magnetic fields can arise in non-central heavy-ion collisions at ultrarelativistic energies, which may not decay quickly in a conducting plasma. We carry out relativistic magnetohydrodynamics (RMHD) simulations to study the effects of this magnetic field on the evolution of the plasma and on resulting flow fluctuations in the ideal RMHD limit. Our results show that magnetic field leads to enhancement in elliptic flow for small impact parameters while it suppresses it for large impact parameters (which may provide a signal for initial stage magnetic field). Interestingly, we find that magnetic field in localized regions can temporarily increase in time as evolving plasma energy density fluctuations lead to reorganization of magnetic flux. This can have important effects on chiral magnetic effect. Magnetic field has non-trivial effects on the power spectrum of flow fluctuations. For very strong magnetic field case one sees a pattern of even-odd difference in the power spectrum of flow coefficients arising from reflection symmetry about the magnetic field direction if initial state fluctuations are not dominant. We discuss the situation of nontrivial magnetic field configurations arising from collision of deformed nuclei and show that it can lead to anomalous elliptic flow. Special (crossed body-body) configurations of deformed nuclei collision can lead to presence of quadrupolar magnetic field which can have very important effects on the rapidity dependence of transverse expansion (similar to beam focusing from quadrupole fields in accelerators).
We estimate various transport coefficients of hot and dense hadronic matter in the presence of magnetic field. The estimation is done through solutions of the relativistic Boltzmann transport equation in the relaxation time approximation.We have investigated the temperature and the baryon chemical potential dependence of these transport coefficients. Explicit calculations are done for the hadronic matter in the ambit of hadron resonance gas model. We estimate thermal conductivity, electrical conductivity and the shear viscosity of hadronic matter in the presence of a uniform magnetic field. Magnetic field, in general, makes the transport coefficients anisotropic. It is also observed that all the transport coefficients perpendicular to the magnetic field are smaller compared to their isotropic counterpart. 12.38.Mh I. INTRODUCTIONStrongly interacting matter produced in relativistic heavy-ion collision experiments at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) give us a unique opportunity to study strong interaction in the nonperturbative regime. For a comprehensive understanding of the hot and dense QCD (quantum chromodynamics) medium produced in these experiments, transport coefficients play a crucial role. Large number of experimental data indicate the formation of quark-gluon plasma in high multiplicity heavy-ion collision experiments. Quark gluon plasma produced in the initial stage of heavy ion collision shows collective motion, undergoes subsequent space-time evolution and eventually gets chemically and the thermally equilibrated and results in a hadronic medium. Hydrodynamical modeling of the strongly interacting matter has been routinely used to study the transverse particle spectra of hadrons emanating out of the interaction region. In the context of hydrodynamical modeling, the dissipative effects can be important and the related transport coefficients e.g. shear and bulk viscosity etc can play a significant role in this hydrodynamical evolution. In various literature it has been argued that a small value of shear viscosity to entropy density ratio (η/s) can explain the flow data[1-3]. One of the remarkable achievements of the viscous hydrodynamical model is the prediction of a small value of η/s and perfect fluid behavior of the strongly interacting matter. A small value of η/s of the strongly coupled plasma produced in the heavy-ion collision is in accordance with the lower bound (KSS bound) for the same, η/s = 1 4π obtained using gauge gravity duality (AdS/CFT correspondence). Prediction of the small value of shear viscosity to entropy density ratio motivated a large number of investigations in understanding the microscopic origin of transport coefficients [3]. It is important to mention that KSS bound has been derived for a strongly coupled quantum field theory having conformal symmetry. However, QCD is not conformal and the deviation of the conformality is encoded in the bulk viscosity ζ, of the medium. [4][5][6][7][8][9][10][11][12]. Bulk viscosity encodes the confor...
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