Ritam Mallick

Scopus Publications

Imprints of non-symmetric dark matter haloes on magnetars: a two-fluid perspective
Asit Karan, Anil Kumar, Monika Sinha, Ritam Mallick
Monthly Notices of the Royal Astronomical Society, 2025
In this study, we investigate the impact of dark matter on the structure and deformation of magnetars. We assume a perturbative approach for the magnetic field deformation and that the dark matter only interacts gravitationally with hadronic matter. Assuming that dark matter is significantly softer than hadronic matter, we find that the magnetic field can affect dark matter through the deformation of space–time. The number of stars having a dark matter halo outside the visible surface of the star increases with an increase in dark matter fraction and the stiffness of the dark matter equation of state. As the magnetic field deforms the stars from sphericity, we can have a situation where we have a non-symmetric dark matter halo outside the star. The deformation of the dark matter halo gives rise to the discrepancies in the observed period P (and period derivative $\\dot{P}$) and gravitational wave signatures. The observed visible surfaces predict a lower period and gravitational wave strain than that with a dark matter halo. This can have interesting observational gravitational signatures unique to magnetars having a dark matter halo.
The prospect of confining the equation of state of neutron stars with future mass and radius measurements
Asim Kumar Saha, Ritam Mallick
European Physical Journal C, 2025
Simultaneous measurement of mass and radius with high precision is essential to unravelling the equation of state of matter at the core of neutron stars. Measurement of massive pulsars indicates that they have to be stiff at low densities. In this work, an ensemble of agnostically constructed equations of state was studied for the mass-radius measurement. The radius of neutron stars obtained from the ensemble was confined within a 10.5–14.5 km bound. Among the NICER measurements, PSR J0437–4715 provides the most stringent constraint on the equation of state. It was found that the detection of stars with smaller radii would prefer a softer equation of state, and the detection of stars with larger radii would prefer a stiffer equation of state. However, irrespective of the detection of stars with a smaller or larger radius, the sound speed peak indicates that stars are likely to have a smooth phase transition at a few times saturation densities, and the matter at the core may not be pure conformal quark matter. A better precision of the radius measurement drastically increases the chances of constraining the equation of state. The equation of state would be more effectively constrained if the measurement of large-radius stars with high precision were to happen. Precise radius measurements of neutron stars with smaller radii provide limited constraints on the equation of state over the density range relevant to neutron stars, largely independent of the stellar mass. Also, measurements for different masses are necessary to constrain the equation of state at all density ranges relevant to neutron stars.
Probing the Internal Structure of Neutron Stars: A Comparative Analysis of Three Different Classes of Equations of State
Anshuman Verma, Asim Kumar Saha, Tuhin Malik, Ritam Mallick
Astrophysical Journal, 2025
Sound speed can be an important tool in unravelling the nature of matter at the cores of neutron stars. In this study, we investigate three major classes of equations of state: monotonic, nonmonotonic, and discontinuous, depending on the nature of the sound speed in neutron stars. The monotonic equation of state refers to hadronic models, the nonmonotonic refers to the quarkyonic or smooth crossover models, and discontinuous refers to the first-order phase transition models. We generate a large ensemble of equations of state for three classes with the model-agnostic speed of sound interpolation approach. Further, we find the Bayesian posterior distribution employing the recent astrophysical and gravitational wave constraints. Our main aim is to identify which class of equation of state is most favored by present astrophysical and gravitational wave bounds. The analysis with posterior distribution fails to provide a satisfactory result with the usual neutron star observations like mass–radius and f-mode oscillations. Universal relations are seen as not being really universal, as they show considerable spread and significant overlaps among the different classes. The Bayesian evidence also fails to provide definitive discrimination between the models, though the astrophysical data slightly favors the nonmonotonic equation of state, while the particular gravitational-wave constraints favor the monotonic one.
Comparison of Equations of State for Neutron Stars with First-order Phase Transitions: A Qualitative Study
Anshuman Verma, Asim Kumar Saha, Ritam Mallick
Astrophysical Journal, 2025
The equation of state is fundamental in describing matter under the extreme conditions characteristic of neutron stars and is central to advancing our understanding of dense matter physics. A critical challenge, however, lies in accurately modeling first-order phase transitions while ensuring thermodynamic consistency and aligning with astrophysical observations. This study explores two frameworks for constructing equations of states with first-order phase transitions: the polytropic interpolation method and the randomized speed-of-sound interpolation approach. It is found that the mass–radius relation and pressure versus energy density relation are blind toward the thermodynamic consistency check. The polytropic interpolation method can exhibit discontinuities in the chemical potential for first-order phase transition, raising concerns regarding potential causality violations and thermodynamic inconsistencies. In contrast, the speed of sound interpolation approach ensures continuity in the chemical potential, offering a more thermodynamically consistent and reliable framework. Moreover, the sound speed method effectively captures the softer segment of the mass–radius spectrum, having an early phase transition, a capability not achieved by the consistent piecewise-polytropic approach due to its monotonic stiffness constraints. The speed of sound definition involving number density and chemical potential reveals the thermodynamic inconsistency, making it a more consistent and robust definition. The sound speed interpolation method also generated a sufficient number of twins, which the piecewise method failed. These findings underscore the importance of thermodynamic consistency in the equation of state construction and highlight the advantages of the randomized speed-of-sound method for modeling phase transitions in dense matter.
Analyzing the dense matter equation of states in the light of the compact object HESS J1731-347
Skund Tewari, Sagnik Chatterjee, Deepak Kumar, Ritam Mallick
Physical Review D, 2025
Modification of the universal relation between mass, radius, and nonradial f -mode oscillation in proto-neutron stars
Deepak Kumar, Asit Karan, Anshuman Verma, Hiranmaya Mishra, Ritam Mallick
Physical Review C, 2025
Analyzing the speed of sound in neutron star with machine learning
Sagnik Chatterjee, Harsha Sudhakaran, Ritam Mallick
European Physical Journal C, 2024
Matter properties at the intermediate densities are still unknown to us. In this work, we use a neural network approach to study matter at intermediate densities to analyze the variation of the speed of sound and the measure of trace anomaly considering astrophysical constraints of mass–radius measurement of 18 neutron stars. Our numerical results show that there is a sharp rise in the speed of sound just beyond the saturation energy density. It attains a peak around 3–4 times the saturation energy density and, after that, decreases. This hints towards the appearance of new degrees of freedom and smooth transition from hadronic matter in massive stars. The trace anomaly is maximum at low density (surface of the stars) and decreases as we reach high density. It approaches zero and can even be slightly negative at the centre of massive stars. It has a negative trough beyond the maximal central densities of neutron stars. The change in sign of the trace anomaly hints towards a near-conformal matter at the centre of neutron stars, which may not necessarily be conformal quark matter.
Prospect of unraveling the first-order phase transition in neutron stars with f and p1 modes
Pratik Thakur, Sagnik Chatterjee, Kamal Krishna Nath, Ritam Mallick
Physical Review D, 2024
Deciphering accretion-dri v en starquak es in recycled millisecond pulsars using gravitational waves
Sagnik Chatterjee, Kamal Krishna Nath, Ritam Mallick
Monthly Notices of the Royal Astronomical Society, 2024
Recycled millisecond pulsars are susceptible to starquakes as they are continuously accreting matter from their binary companion. A starquake happens when the rotational frequency of the star crosses its breaking frequency. In this study, we perform a model analysis of an accreting neutron star suffering a starquake. We analyse two models: a spherical star with accreting mountains and a deformed star with accreting mountains. We find that as the star crosses the breaking frequency and suffers a starquake, there is a sudden change in the continuous gravitational wave signal arriving from it. The amplitude of the gravitational wave signal increases suddenly both for the spherical and deformed star. For the spherical star, the accreting matter entirely dictates the amplitude of the gravitational wave. For the deformed star, both the accreting matter and the deformation from spherical symmetry play a significant role in determining the amplitude of the gravitational wave signal. This sudden change in the continuous gravitational wave signal in recycled millisecond pulsars can be a unique signature for such pulsars undergoing a starquake.
Effects of onset of phase transition on binary neutron star mergers
Shamim Haque, Ritam Mallick, Shashikesh K Thakur
Monthly Notices of the Royal Astronomical Society, 2024
Quantum Chromodynamics predicts phase transition from hadronic matter to quark matter at high density, which is highly probable in astrophysical systems like binary neutron star mergers. To explore the critical density where such phase transition can occur, we performed numerical relativity simulations of binary neutron star mergers with various masses (equal and unequal binaries). We aim to understand the effect of the onset of phase transition on the merger dynamics and gravitational wave spectra. We generated a set of equations of states by agnostically changing the onset of phase transition, having the hadronic matter part and quark matter part fixed. This particular arrangement of the equation of states explores the scenario of mergers where mixed phases of matter are achieved before or during the merger. Under these circumstances, if the matter properties with hadronic and quark degrees differ significantly, it is reflected in the stability of the final merger product for the intermediate mass binary. We performed a case study on mixed species merger, where one of the binary companions is hybrid star. If quark matter appears at low densities, we observe significant change in post-merger gravitational wave analysis in terms of higher peak frequencies and post-merger frequencies in power spectral density. We report indications expressed as spikes in phase difference plots at merger time for mixed mergers. We found that the expression of phase transition in post-merger gravitational wave signals is more significant for unequal mass binary than for equal mass binary having the same total baryonic mass.
I-Love-Q relations for a generic family of neutron star equations of state
Kamal Krishna Nath, Ritam Mallick, Sagnik Chatterjee
Monthly Notices of the Royal Astronomical Society, 2023
Shock waves in (1 + 1-dimensional) curved space-time
Anshuman Verma, Ritam Mallick
Monthly Notices of the Royal Astronomical Society, 2023
Study of general relativistic shocks and their propagation in neutron stars
Ritam Mallick, Anshuman Verma
Journal of High Energy Astrophysics, 2022
Spin-down induced quark-hadron phase transition in cold isolated neutron stars
R Prasad, Ritam Mallick
Monthly Notices of the Royal Astronomical Society, 2022
General relativistic calculation of magnetic field and power loss for a misaligned pulsar
Sagnik Chatterjee, Ritam Mallick, Debojoti Kuzur
Journal of High Energy Astrophysics, 2022
Semi-empirical relation to understand matter properties at neutron star interiors
Ritam Mallick, Debojoti Kuzur, Rana Nandi
European Physical Journal C, 2022
Examination of the multitude of signals from the phase transition of a neutron star to a quark star
Debojoti Kuzur, Ritam Mallick, R. Prasad, Shailendra Singh
Physical Review C, 2022
Tidal effect on the gyroscopic precession around a compact star
Kamal Krishna Nath, Debojoti Kuzur, Ritam Mallick
International Journal of Modern Physics D, 2022
Gravitational wave signatures of phase transition from hadronic to quark matter in isolated neutron stars and binaries
Ritam Mallick
15th Conference on Quark Confinement and the Hadron Spectrum Confinement 2022, 2022
Frame-dragging effects in obliquely rotating magnetars
Debojoti Kuzur, Ritam Mallick
Journal of Astrophysics and Astronomy, 2021
Gravitational wave signature from phase transition of a combusting neutron star to quark star
Ritam Mallick, Shailendra Singh, Prasad R
Monthly Notices of the Royal Astronomical Society, 2021
Maximum mass of hybrid star formed via shock-induced phase transition in cold neutron stars
Ritam Mallick, Shailendra Singh, Rana Nandi
Monthly Notices of the Royal Astronomical Society, 2021
Acceleration of charged particles in rotating magnetized star
Debojoti Kuzur, Rupamoy Bhattacharyya, Ritam Mallick
Journal of Physics G Nuclear and Particle Physics, 2020
Effect of rotation and magnetic field in the gyroscopic precession around a neutron star
Kamal Krishna Nath, Ritam Mallick
European Physical Journal C, 2020
Gravitational waves from the phase transition of ns to qs
R Prasad, Ritam Mallick
Astrophysical Journal, 2020
Magnetized Taub adiabat and the PT characteristics of magnetic neutron stars
Ritam Mallick, Shailendra Singh
Physical Review C, 2019
Combustion adiabat and the maximum mass of a quark star
Ritam Mallick, Mohammad Irfan
Monthly Notices of the Royal Astronomical Society, 2019
Time-like detonation in presence of magnetic field
Shailendra Singh, Ritam Mallick
Laser and Particle Beams, 2019
Effect of magnetic field on the burning of a neutron star
Ritam Mallick, Amit Singh
International Journal of Modern Physics E, 2018
Dynamical Phase Transition in Neutron Stars
R. Prasad, Ritam Mallick
Astrophysical Journal, 2018
Models of hyperstars and hybrid stars
S. Schramm, V. Dexheimer, R. Mallick, R. Negreiros
14th Marcel Grossman Meeting on Recent Developments in Theoretical and Experimental General Relativity Astrophysics and Relativistic Field Theories Proceedings, 2018
Nonequilibrium phase transition in compact stars through a violent shock
Igor Mishustin, Ritam Mallick, Rana Nandi, Leonid Satarov
Physical Review C Nuclear Physics, 2015
On the possibility of rho-meson condensation in neutron stars
Ritam Mallick, Stefan Schramm, Veronica Dexheimer, Abhijit Bhattacharyya
Monthly Notices of the Royal Astronomical Society, 2015
Exotic matter in compact stars
Proceedings of Science, 2015
Magnetic field & neutron stars: A comprehensive study
Proceedings of Science, 2015
Deformation of a magnetized neutron star
Ritam Mallick, Stefan Schramm
Physical Review C Nuclear Physics, 2014
Oblique magnetohydrodynamic shocks: Space-like and time-like characteristics
Ritam Mallick, Stefan Schramm
Physical Review C Nuclear Physics, 2014
Phase transitions in neutron star and magnetars and their connection with high energetic bursts in astrophysics
Ritam Mallick, P.K. Sahu
Nuclear Physics A, 2014
Neutron star in the presence of strong magnetic field
K K MOHANTA, R MALLICK, N R PANDA, L P SINGH, P K SAHU
Pramana Journal of Physics, 2014
Maximum mass of a hybrid star having a mixed-phase region based on constraints set by the pulsar PSR J1614-2230
Ritam Mallick
Physical Review C Nuclear Physics, 2013
General relativistic effect on the energy deposition rate for neutrino pair annihilation above the equatorial plane along the symmetry axis near a rotating neutron star
RITAM MALLICK, ABHIJIT BHATTACHARYYA, SANJAY K. GHOSH, SIBAJI RAHA
International Journal of Modern Physics E, 2013
Solving a relativistic hydrodynamic equation in the presence of a magnetic field for a phase transition in a neutron star
Ritam Mallick, Rajesh Gopal, Sanjay K Ghosh, Sibaji Raha, Suparna Roychowdhury
Journal of Physics G Nuclear and Particle Physics, 2012
Solving the relativistic Rankine-Hugoniot condition in the presence of a magnetic field in the astrophysical scenario of a neutron star
Ritam Mallick
Physical Review C Nuclear Physics, 2011
Conversion of nuclear to 2-flavour quark matter in rotating compact stars: A general relativistic perspective
R. Mallick, A. Bhattacharyya, S. K. Ghosh, S. Raha
Indian Journal of Physics, 2011
Erratum: Possible conversion of a neutron star to a quark star in the presence of high magnetic field
Ritam Mallick, Monika Sinha
Monthly Notices of the Royal Astronomical Society, 2011
Possible conversion of a neutron star to a quark star in the presence of high magnetic field
Ritam Mallick, Monika Sinha
Monthly Notices of the Royal Astronomical Society, 2011
Explaining GRB in the light of energy deposition rate for ν + ν̄ → e+ + e- in a compact star
Abhijit Bhattacharyya, Sanjay K. Ghosh, Ritam Mallick, Sibaji Raha
Indian Journal of Physics, 2010
General relativistic study of the neutrino path and calculation of the minimum photosphere for different stars
Ritam Mallick, Sarbani Majumder
Physical Review D Particles Fields Gravitation and Cosmology, 2009
General relativistic effects on the conversion of nuclear to two-flavor quark matter in compact stars
Abhijit Bhattacharyya, Sanjay K. Ghosh, Ritam Mallick, Sibaji Raha
Physical Review C Nuclear Physics, 2007
Conversion of a neutron star to a strange star: A two-step process
Abhijit Bhattacharyya, Sanjay K. Ghosh, Partha S. Joarder, Ritam Mallick, Sibaji Raha
Physical Review C Nuclear Physics, 2006

MOST CITED SCHOLAR PUBLICATIONS

Conversion of a neutron star to a strange star: A two-step process
A Bhattacharyya, SK Ghosh, PS Joarder, R Mallick, S Raha
Physical Review C—Nuclear Physics 74 (6), 065804 , 2006
2006
Citations: 96
Deformation of a magnetized neutron star
R Mallick, S Schramm
Physical Review C 89 (4), 045805 , 2014
2014
Citations: 84
Maximum mass of a hybrid star having a mixed-phase region based on constraints set by the pulsar PSR J1614-2230
R Mallick
Physical Review C—Nuclear Physics 87 (2), 025804 , 2013
2013
Citations: 32
Dynamical phase transition in neutron stars
R Prasad, R Mallick
The Astrophysical Journal 859 (1), 57 , 2018
2018
Citations: 28
Analyzing the speed of sound in neutron star with machine learning
S Chatterjee, H Sudhakaran, R Mallick
The European Physical Journal C 84 (12), 1291 , 2024
2024
Citations: 25
Phase transitions in neutron star and magnetars and their connection with high energetic bursts in astrophysics
R Mallick, PK Sahu
Nuclear Physics A 921, 96-113 , 2014
2014
Citations: 23
General relativistic effects on the conversion of nuclear to two-flavor quark matter in compact stars
A Bhattacharyya, SK Ghosh, R Mallick, S Raha
Physical Review C—Nuclear Physics 76 (5), 052801 , 2007
2007
Citations: 22
Effects of onset of phase transition on binary neutron star mergers
S Haque, R Mallick, SK Thakur
Monthly Notices of the Royal Astronomical Society 527 (4), 11575-11586 , 2024
2024
Citations: 21
Possible conversion of a neutron star to a quark star in the presence of high magnetic field
R Mallick, M Sinha
Monthly Notices of the Royal Astronomical Society 414 (3), 2702-2708 , 2011
2011
Citations: 21
Nonequilibrium phase transition in compact stars through a violent shock
I Mishustin, R Mallick, R Nandi, L Satarov
Physical Review C 91 (5), 055806 , 2015
2015
Citations: 20
Gravitational wave signature from phase transition of a combusting neutron star to quark star
R Mallick, S Singh, P R
Monthly Notices of the Royal Astronomical Society 507 (1), 1318-1328 , 2021
2021
Citations: 19
Gravitational Waves from the Phase Transition of NS to QS
R Prasad, R Mallick
The Astrophysical Journal 893 (2), 151 , 2020
2020
Citations: 17
Prospect of unraveling the first-order phase transition in neutron stars with and modes
P Thakur, S Chatterjee, KK Nath, R Mallick
Physical Review D 110 (10), 103045 , 2024
2024
Citations: 15
Combustion adiabat and the maximum mass of a quark star
R Mallick, M Irfan
Monthly Notices of the Royal Astronomical Society 485 (1), 577-585 , 2019
2019
Citations: 15
Analyzing the dense matter equation of states in the light of the compact object HESS J1731-347
S Tewari, S Chatterjee, D Kumar, R Mallick
Physical Review D 111 (10), 103009 , 2025
2025
Citations: 12
I-Love-Q relations for a generic family of neutron star equations of state
KK Nath, R Mallick, S Chatterjee
Monthly Notices of the Royal Astronomical Society 524 (1), 1438-1447 , 2023
2023
Citations: 12
On the possibility of rho-meson condensation in neutron stars
R Mallick, S Schramm, V Dexheimer, A Bhattacharyya
Monthly Notices of the Royal Astronomical Society 449 (2), 1347-1351 , 2015
2015
Citations: 11
Spin-down induced quark-hadron phase transition in cold isolated neutron stars
R Prasad, R Mallick
Monthly Notices of the Royal Astronomical Society 516 (1), 1127-1136 , 2022
2022
Citations: 10
General Relativistic effect on the energy deposition rate for neutrino pair annihilation above the equatorial plane along the symmetry axis near a rotating neutron star
R Mallick, A Bhattacharyya, SK Ghosh, S Raha
International Journal of Modern Physics E 22 (02), 1350008 , 2013
2013
Citations: 10
Maximum mass of hybrid star formed via shock-induced phase transition in cold neutron stars
R Mallick, S Singh, R Nandi
Monthly Notices of the Royal Astronomical Society 503 (4), 4829-4837 , 2021
2021
Citations: 9

Ritam Mallick

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Scopus Publications

RECENT SCHOLAR PUBLICATIONS

MOST CITED SCHOLAR PUBLICATIONS