arXiv subjects

Sujan Kumar Roy

Publications and source records attributed to Sujan Kumar Roy.

6 recordsLinked to original sources

arXiv2026

Radial Oscillations and Stability of Neutron Stars with Antikaon Condensates

Radial oscillations provide a direct probe of the stability and compressibility of neutron stars and are highly sensitive to the equation of state of dense matter. In this work, we investigate the impact of antikaon condensates on the radial oscillation properties of neutron stars. We model neutron star matter using equations of state with a wide range of stiffness. For this purpose, both non-linear and density-dependent relativistic mean-field frameworks are employed to develop equations of state that are consistent with current astrophysical constraints. We further consider the emergence of antikaon condensates ($K^-$ and $\bar{K}^0$) in the stellar core, which modifies the pressure--energy density relation of dense matter. We find that the nature of the transition from nuclear matter to the condensed phase is sensitive to the antikaon optical potential depth and underlying equation of state. We compute the fundamental and higher-order radial oscillation modes for neutron stars containing antikaon condensates over a range of antikaon optical potential depths. Our results demonstrate that the antikaon optical potential depth plays a decisive role in governing the systematic shifts observed in the radial oscillation frequencies, while also significantly reducing the stability limits and maximum masses of neutron stars. These imprints of antikaon condensation on radial oscillation spectra provide a promising avenue for future multi-messenger observations and high-frequency gravitational-wave searches to directly probe and constrain the internal composition and equation of state of neutron stars.

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arXiv2026

BengaliSent140: A Large-Scale Bengali Binary Sentiment Dataset for Hate and Non-Hate Speech Classification

Sentiment analysis for the Bengali language has attracted increasing research interest in recent years. However, progress remains constrained by the scarcity of large-scale and diverse annotated datasets. Although several Bengali sentiment and hate speech datasets are publicly available, most are limited in size or confined to a single domain, such as social media comments. Consequently, these resources are often insufficient for training modern deep learning based models, which require large volumes of heterogeneous data to learn robust and generalizable representations. In this work, we introduce BengaliSent140, a large-scale Bengali binary sentiment dataset constructed by consolidating seven existing Bengali text datasets into a unified corpus. To ensure consistency across sources, heterogeneous annotation schemes are systematically harmonized into a binary sentiment formulation with two classes: Not Hate (0) and Hate (1). The resulting dataset comprises 139,792 unique text samples, including 68,548 hate and 71,244 not-hate instances, yielding a relatively balanced class distribution. By integrating data from multiple sources and domains, BengaliSent140 offers broader linguistic and contextual coverage than existing Bengali sentiment datasets and provides a strong foundation for training and benchmarking deep learning models. Baseline experimental results are also reported to demonstrate the practical usability of the dataset. The dataset is publicly available at https://www.kaggle.com/datasets/akifislam/bengalisent140/

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arXiv2025

Equation-of-State Independent Relations in Rapidly Rotating Hybrid Stars

We study 22 hadronic and 100 hybrid equations of state (EoSs) that allow for heavy baryons and deconfined quark matter at high densities, aiming to establish quasi-universal relations for both slowly and rapidly rotating neutron stars. All EoSs are consistent with current observational constraints, including NICER and GW170817. Our results confirm that the I-Love-Q and I-C-Q relations remain approximately EoS-insensitive across this broad EoS set, with deviations typically within 10\% for hadronic stars and up to 20\% for those with complex core compositions. These relations are extended to include low-mass neutron stars such as HESS J1731-347, and to stars with general core compositions--nucleonic, hyperonic (full baryon octet), and quark matter. The analysis underscores both the robustness and the limitations of universal relations when applied to compact stars with exotic degrees of freedom and rapid rotation.

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arXiv2025

I-C-Q relations for rapidly rotating stable hybrid stars

A number of hadronic equations of state for neutron stars have been investigated for the purpose of the present paper, considering the fact that at sufficiently high density, heavy baryons and quark phases may appear. The observational limits from NICER, GW170817, etc., are obeyed by our choice of equations of state. The universal relations are investigated for both slowly and rapidly rotating neutron stars with heavy baryons present inside the core. For slowly rotating stars, the universality of the I-Love-Q relations is verified, and the I-C-Q relations are inferred to be universal for rapidly rotating stars. Further, we extend the investigation to obtain the universal relations for compact stars containing the quark core, where the connected stable branch of such hybrid stars is considered. The parameters of the I-Love-Q and I-C-Q universal relations are obtained for slowly rotating and rapidly rotating hybrid stars, respectively. These relations would enable extracting information, within the context of general relativity, from astrophysical systems involving rapidly rotating neutron stars.

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arXiv2020

Compact star deformation and universal relationship for magnetized white dwarfs

Recently super-Chandrasekhar mass limit has been derived theoretically in presence of strong magnetic field to complement experimental observations. In the framework of Newtonian physics, we have studied the equilibrium configurations of such magnetized white dwarfs by using the relativistic Thomas-Fermi equation of state for magnetized white-dwarfs. Hartle formalism, for slowly rotating stars, has been employed to obtain the equations of equilibrium. Various physical quantities of uniformly rotating and non-rotating white dwarfs have been calculated within this formalism. Consequently, the universality relationship between the moment of inertia(I), rotational love number($λ$) and spin induced quadrupole moment(Q), namely the I-Love-Q relationship, has been investigated for such magnetized white dwarfs. The relationship between I, eccentricity and Q i.e. I-eccentricity-Q relationship has also been derived. Further, we have found that, the I-eccentricity-Q relationship is more universal in comparison to I-Love-Q relationship.

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arXiv2019

Relativistic Feynman-Metropolis-Teller Equation of State for White Dwarfs in presence of Magnetic Field

The relativistic Feynman-Metropolis-Teller treatment of compressed atoms is extended to treat magnetized matter. Each atomic configuration is confined by a Wigner-Seitz cell and is characterized by a positive electron Fermi energy which varies insignificantly with the magnetic field. In the relativistic treatment the limiting configuration is reached when the Wigner-Seitz cell radius equals the radius of the nucleus with a maximum value of the electron Fermi energy which can not be attained in presence of magnetic field due to the effect of Landau quantization of electrons within the Wigner-Seitz cell. This treatment is implemented to develop the Equation of State for magnetized White Dwarf stars in presence of Coulomb screening. The mass-radius relations for magnetized White Dwarfs are obtained by solving the general relativistic hydrostatic equilibrium equations using Schwarzschild metric description suitable for non rotating and slowly rotating stars. The explicit effects of the magnetic energy density and pressure contributed by a density-dependent magnetic field are included to find the stable configurations of magnetized Super-Chandrasekhar White Dwarfs.

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