arXiv subjects

Pranjal Tambe

Publications and source records attributed to Pranjal Tambe.

3 recordsLinked to original sources

arXiv2026

Transport properties in binary neutron star mergers: Effect of magnetic field

In extreme environments such as binary neutron star mergers, temperatures as high as $50$ MeV and magnetic fields up to $10^{17}$ G, reach a regime where neutrino transport governs the macroscopic thermodynamic and chemical evolution. Existing merger simulations rely on zero magnetic field neutrino emissivity and opacity, potentially missing critical transport physics in highly magnetized neutron star cores. We present an exact framework for computing charged current Urca emissivity and neutrino opacity at finite temperature and magnetic field. We employ the Nucleon Width Approximation framework to account for the collisional broadening effects dominant in the high-density core. Our calculations demonstrate that extreme magnetic fields significantly enhance charged current neutrino opacity, effectively reducing the mean free path for thermal neutrinos.

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arXiv2026

Thermal and Magnetic effects on Bulk Viscosity in Binary Neutron Star Mergers

Astrophysical scenarios such as binary neutron star mergers, protoneutron stars, and core-collapse supernovae involve finite temperatures and strong magnetic fields. Previous studies on the effect of magnetic fields on flavor-equilibration processes relied on the Fermi surface approximation, which is not a reliable approximation in the neutrino-transparent regime of matter in supernovae or neutron star mergers. In a recent study, we went beyond the Fermi surface approximation, performing the full phase space integral to obtain direct Urca rates in a background magnetic field. In this work, we extend these calculations to incorporate the collisional broadening (modified Urca) contribution. We use the recently developed nucleon width approximation, which naturally includes the magnetic field dependence of all contributions. We demonstrate the impact of magnetic fields on the flavor-equilibrium condition for two finite-temperature equations of state with different direct Urca thresholds. We also study the impact of magnetic fields on the bulk viscous dissipation of density oscillations relevant in postmerger scenarios.

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arXiv2025

Effect of Magnetic Fields on Urca Rates in Neutron Star Mergers

Isospin-equilibrating weak processes, called ``Urca" processes, are of fundamental importance in astrophysical environments like (proto-)neutron stars, neutron star mergers, and supernovae. In these environments, matter can reach high temperatures of tens of MeVs and be subject to large magnetic fields. We thus investigate Urca rates at different temperatures and field strengths by performing the full temperature and magnetic-field dependent rate integrals for different equations of state. We find that the magnetic fields play an important role at temperatures of a few MeV, especially close to or below the direct Urca threshold, which is softened by the magnetic field. At higher temperatures, the effect of the magnetic fields can be overshadowed by the thermal effects. We observe that the magnetic field more strongly influences the neutron decay rates than the electron capture rates, leading to a shift in the flavor equilibrium.

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