Papers by Sarmistha Banik
Role of hyperon equation of state in core collapse supernova
Physical Review C, 2014
We investigate the role of hyperons in the dynamical collapse of a non-rotating massive star to a... more We investigate the role of hyperons in the dynamical collapse of a non-rotating massive star to a black hole(BH) using one dimensional general relativistic GR1D code. We follow the dynamical formation and evolution of a protoneutron star (PNS) to a black hole using various progenitor models, adopting a hyperonic equation of state (EoS) generated by Shen et. al. We compare the results with those of nuclear EoS by Shen et. al. and understand the role of strange hyperons in the core collapse supernova. We discuss the neutrino signals that may be used as a probe to core collapse. Further, an exotic EoS can support a much lower maximum mass cold neutron star compared to PNS. In this regard, we also study the metastability of PNS in the presence of hyperon in the long-time evolution of the progenitors, relevant to supernova SN1987A. PACS numbers: 26.60.Kp, 26.50.+x, 26.60.-c, 14.20.Jn 1 I. INTRODUCTION
Role of hyperons in black hole formation
Journal of Physics: Conference Series, 2013
ABSTRACT A phase transition from hadronic to exotic phases might occur in the early post-bounce p... more ABSTRACT A phase transition from hadronic to exotic phases might occur in the early post-bounce phase of a core collapse supernova. We investigate the role of strange hyperons in the dynamical collapse of a non-rotating massive star to a black hole using 1D General relativistic simulation GR1D. We follow the dynamical formation and collapse of a protoneutron star (PNS) from the gravitational collapse of a 40Msolar progenitor of Wooseley, adopting Shen hyperonic EoS. We also study the neutrino signals that may be used as a probe to core collapse supernova. We compare the results with those of Shen nuclear EoS and understand the role of strange hyperons in the core collapse.
A first order phase transition from nuclear matter to antikaon condensed matter may proceed throu... more A first order phase transition from nuclear matter to antikaon condensed matter may proceed through thermal nucleation of a critical droplet of antikaon condensed matter during the early evolution of protoneutron stars (PNS). Droplets of new phase having radii larger than a critical radius would survive and grow, if the latent heat is transported from the droplet surface to the metastable phase. We investigate the effect of shear viscosity on the thermal nucleation time of the droplets of antikaon condensed matter. In this connection we particularly study the contribution of neutrinos in the shear viscosity and nucleation in PNS.
A COMPARATIVE STUDY OF HYPERON EQUATIONS OF STATE IN SUPERNOVA SIMULATIONS
The Astrophysical Journal, 2015
Physical Review C, 2012
We study the melting of a K − condensate in hot and neutrino-trapped protoneutron stars. In this ... more We study the melting of a K − condensate in hot and neutrino-trapped protoneutron stars. In this connection, we adopt relativistic field theoretical models to describe the hadronic and condensed phases. It is observed that the critical temperature of antikaon condensation is enhanced as baryon density increases. For a fixed baryon density, the critical temperature of antikaon condensation in a protoneutron star is smaller than that of a neutron star. We also exhibit the phase diagram of a protoneutron star with a K − condensate. PACS numbers: 26.60.+c, 21.65.+f, 97.60.Jd, 95.30.Cq
Massive neutron stars with antikaon condensates in a density-dependent hadron field theory
Physical Review C, 2014
Physical Review D, 2010
We investigate a first-order phase transition from hadronic matter to antikaon condensed matter d... more We investigate a first-order phase transition from hadronic matter to antikaon condensed matter during the cooling stage of protoneutron stars. The phase transition proceeds through the thermal nucleation of antikaon condensed matter. In this connection we study the effect of shear viscosity on the thermal nucleation rate of droplets of antikaon condensed matter. Here we adopt the same equation of state for the calculation of shear viscosity and thermal nucleation time. We compute the shear viscosity of neutron star matter composed of neutrons, protons, electrons and muons using the relativistic mean field model. The prefactor in the nucleation rate which includes the shear viscosity, is enhanced by several orders of magnitude compared with the T 4 approximation of earlier calculations. Consequently the thermal nucleation time in the T 4 approximation overestimates our result. Further the thermal nucleation of an antikaon droplet might be possible in our case for surface tension smaller than 20 MeV fm −2 .
A first order phase transition from nuclear matter to antikaon condensed matter may proceed throu... more A first order phase transition from nuclear matter to antikaon condensed matter may proceed through thermal nucleation of a critical droplet of antikaon condensed matter during the early evolution of proto neutron stars (PNS). Droplets of new phase having radii larger than a critical radius would survive and grow, if the latent heat is transported from the droplet surface to the metastable phase. We investigate the effect of shear viscosity on the thermal nucleation time of the droplets of antikaon condensed matter. In this connection we particularly study the contribution of neutrinos in the shear viscosity and nucleation in PNS.
Pramana, 2003
We investigate the role of Bose-Einstein condensation (BEC) of anti-kaons on the equation of stat... more We investigate the role of Bose-Einstein condensation (BEC) of anti-kaons on the equation of state (EoS) and other properties of compact stars. In the framework of relativistic mean field model we determine the EoS for β -stable hyperon matter and compare it to the situation when anti-kaons condense in the system. We observe that anti-kaon condensates soften the EoS, thereby lowering the maximum mass of the stars. We also demonstrate that the presence of antikaon condensates in the high density core of compact stars may lead to a new mass sequence beyond white dwarf and neutron stars. The limiting mass of the new sequence stars is nearly equal to that of neutron star branch though they have distinctly different radii and compositions. They are called neutron star twins.
Physical Review D, 2004
We have constructed models of uniformly rotating compact stars including hyperons, Bose-Einstein ... more We have constructed models of uniformly rotating compact stars including hyperons, Bose-Einstein condensates of antikaons and quarks. First order phase transitions from hadronic to antikaon condensed matter and then to quark matter are considered here. For the equation of state undergoing phase transitions to antikaon condensates, the third family of compact stars are found to exist in the fixed angular velocity sequences. However, the third family solution disappears when the compact stars rotate very fast. For this equation of state, the fixed baryon number supramassive sequence shows a second stable part after the unstable region but no back bending phenomenon. On the other hand, we observe that the rotation gives rise to a second maximum beyond the neutron star maximum for the equation of state involving phase transitions to both antikaon condensed and quark matter. In this case, the back bending phenomenon has been observed in the supramassive sequence as a consequence of the first order phase transition from K − condensed to quark matter. And the back bending segment contains stable configurations of neutron stars. PACS: 26.60.+c, 21.65.+f, 97.60.Jd, 95.30.Cq
Physical Review D, 2009
We investigate the shear viscosity of neutron star matter in the presence of an antikaon condensa... more We investigate the shear viscosity of neutron star matter in the presence of an antikaon condensate. The electron and muon number densities are reduced due to the appearance of a K − condensate in neutron star matter, whereas the proton number density increases. Consequently the shear viscosity due to scatterings of electrons and muons with themselves and protons is lowered compared to the case without the condensate. On the other hand, the contribution of proton-proton collisions to the proton shear viscosity through electromagnetic and strong interactions, becomes important and comparable to the neutron shear viscosity.
Physical Review D, 2003
We investigate first order phase transitions from β-equilibrated hadronic matter to color flavor ... more We investigate first order phase transitions from β-equilibrated hadronic matter to color flavor locked quark matter in compact star interior. The hadronic phase including hyperons and Bose-Einstein condensate of K − mesons is described by the relativistic field theoretical model with density dependent meson-baryon couplings. The early appearance of hyperons and/or Bose-Einstein condensate of K − mesons delays the onset of phase transition to higher density. In the presence of hyperons and/or K − condensate, the overall equations of state become softer resulting in smaller maximum masses than the cases without hyperons and K − condensate. We find that the maximum mass neutron stars may contain a mixed phase core of hyperons, K − condensate and color superconducting quark matter. Depending on the parameter space, we also observe that there is a stable branch of superdense stars called the third family branch beyond the neutron star branch. Compact stars in the third family branch may contain pure color superconducting core and have radii smaller than those of the neutron star branch. Our results are compared with the recent observations on RX J185635-3754 and the recently measured mass-radius relationship by X-ray Multi Mirror-Newton Observatory.
Physical Review C, 2008
We investigate the critical temperature of Bose-Einstein condensation of K − mesons in neutron st... more We investigate the critical temperature of Bose-Einstein condensation of K − mesons in neutron star matter. This is studied within the framework of relativistic field theoretical models at finite temperature where nucleon-nucleon and (anti)kaon-nucleon interactions are mediated by the exchange of mesons. The melting of the antikaon condensate is studied for different values of antikaon optical potential depths. We find that the critical temperature of antikaon condensation increases with baryon number density. Further it is noted that the critical temperature is lowered as antikaon optical potential becomes less attractive. We also construct the phase diagram of neutron star matter with K − condensate. PACS numbers: 26.60.+c, 21.65.+f, 97.60.Jd, 95.30.Cq
Physical Review C, 2010
A microscopic approach has been employed to study the kaon productions in heavy ion collisions. T... more A microscopic approach has been employed to study the kaon productions in heavy ion collisions. The momentum integrated Boltzmann equation has been used to study the evolution of strangeness in the system formed in heavy ion collision at relativistic energies. The kaon productions have been calculated for different centre of mass energies ( √ sNN) ranging from AGS to RHIC. The results have been compared with available experimental data. We obtain a non-monotonic horn like structure for K + /π + when plotted with √ sNN with the assumption of an initial partonic phase beyond a threshold in √ sNN . However, a monotonic rise of K + /π + is observed when a hadronic initial state is assumed for all √ sNN. Experimental values of K − /π − are also reproduced within the ambit of the same formalism. PACS numbers: 25.75.-q,25.75.Dw,24.85.+p
Physical Review C, 2001
We investigate the condensation ofK 0 meson along with K − condensation in the neutrino trapped m... more We investigate the condensation ofK 0 meson along with K − condensation in the neutrino trapped matter with and without hyperons. Calculations are performed in the relativistic mean field models in which both the baryonbaryon and (anti)kaon-baryon interactions are mediated by meson exchange. In the neutrino trapped matter relevant to protoneutron stars, the critical density of K − condensation is shifted considerably to higher density whereas that ofK 0 condensation is shifted slightly to higher density with respect to that of the neutrino free case. The onset of K − condensation always occurs earlier than that ofK 0 condensation. A significant region of maximum mass protoneutron stars is found to containK 0 condensate for larger values of the antikaon potential. With the appearance ofK 0 condensation, there is a region of symmetric nuclear matter in the inner core of a protoneutron star. It is found that the maximum mass of a protoneutron star containing K − and K 0 condensate is greater than that of the corresponding neutron star. We revisit the implication of this scenario in the context of the metastability of protoneutron stars and their evolution to low mass black holes. PACS: 26.60.+c, 21.65.+f, 97.60.Jd, 95.30.Cq
Physical Review C, 2001
The formation of K − andK 0 condensation in β-equilibrated hyperonic matter is investigated withi... more The formation of K − andK 0 condensation in β-equilibrated hyperonic matter is investigated within a relativistic mean field model. In this model, baryon-baryon and (anti)kaon-baryon interactions are mediated by the exchange of mesons. It is found that antikaon condensation is not only sensitive to the equation of state but also to antikaon optical potential depth. For large values of antikaon optical potential depth, K − condensation sets in before the appearance of negatively charged hyperons. We treat K − condensation as a first order phase transition. The Gibbs criteria and global charge conservation laws are used to describe the mixed phase. Nucleons and Λ hyperons behave dynamically in the mixed phase. A second order phase transition tō K 0 condensation occurs in the pure K − condensed phase. Along with K − condensation,K 0 condensation makes the equation of state softer thus resulting in smaller maximum mass stars compared with the case without any condensate. This equation of state also leads to a stable sequence of compact stars called the third family branch, beyond the neutron star branch. The compact stars in the third family branch have different compositions and smaller radii than that of the neutron star branch. PACS: 26.60.+c, 21.65.+f, 97.60.Jd, 95.30.Cq
Physical Review C, 2011
We study shear viscosities of different species in hot and neutrino-trapped dense matter relevant... more We study shear viscosities of different species in hot and neutrino-trapped dense matter relevant to protoneutron stars. It is found that the shear viscosities of neutrons, protons and electrons in neutrino-trapped matter are of the same orders of magnitude as the corresponding shear viscosities in neutrino-free matter. Above all, the shear viscosity due to neutrinos is higher by several orders of magnitude than that of other species in neutrino-trapped matter.
Physical Review C, 2002
We investigate K − andK 0 condensation in β-equilibrated hyperonic matter within a density depend... more We investigate K − andK 0 condensation in β-equilibrated hyperonic matter within a density dependent hadron field theoretical model. In this model, baryon-baryon and (anti)kaon-baryon interactions are mediated by the exchange of mesons. Density dependent meson-baryon coupling constants are obtained from microscopic Dirac Brueckner calculations using Groningen and Bonn A nucleon-nucleon potential. It is found that the threshold of antikaon condensation is not only sensitive to the equation of state but also to antikaon optical potential depth. Only for large values of antikaon optical potential depth, K − condensation sets in even in the presence of negatively charged hyperons. The threshold ofK 0 condensation is always reached after K − condensation. Antikaon condensation makes the equation of state softer thus resulting in smaller maximum mass stars compared with the case without any condensate. PACS: 26.60.+c, 21.65.+f, 97.60.Jd, 95.30.Cq
Nuclear Physics A, 2011
A microscopic approach has been employed to study the kaon and Λ productions in heavy ion collisi... more A microscopic approach has been employed to study the kaon and Λ productions in heavy ion collisions. The productions of K + and Λ have been studied within the framework of Boltzmann transport equation for various beam energies. We find a non-monotonic horn like structure for K + /π + and Λ/π when plotted against centre of mass energies ( √ s NN ) with the assumption of initial partonic phase for √ s NN beyond a certain threshold. However, the ratio K + /π + shows a monotonic nature when a hadronic initial state is considered for all √ s NN . Experimental values of K − /π − for different √ s NN are also reproduced within the ambit of the same formalism.
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Papers by Sarmistha Banik