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Shibaji Banerjee

Publications and source records attributed to Shibaji Banerjee.

At least 19 recordsLinked to original sources
arXiv2025

Bridging the Gap Between Virtual and Physical Laboratories: A Web-Based Interactive Platform for Undergraduate Physics Practicals

The COVID-19 pandemic highlighted the challenges of maintaining hands-on laboratory instruction in undergraduate physics education. In response, we developed and deployed an interactive online physics laboratory platform designed to closely replicate the experimental setups available and curriculum of St. Xavier's College (Autonomous), Kolkata. The platform is designed to closely replicate real experimental arrangements and is aligned with the curriculum, allowing students to prepare effectively before performing physical experiments. Student feedback revealed that 100% of the respondents rated the platform as beneficial (rating 4 or 5 on a 5-point scale) to improve conceptual understanding and increase confidence in conducting physical experiments. Furthermore, all students agreed that having access to the online prelab simulations is advantageous and recommended its regular use. These findings highlight the effectiveness of web-based simulations as a complementary and sustainable resource for physics education.

physics.ed-ph↗
arXiv2024

Constraining the parameters of an isolated neutron star using the lensed HI signal at uGMRT

The strength of the HI signal originating from a distant galaxy at a cosmological distance is several orders of magnitude lower than the foreground and background noise and hence it is difficult to observe this signal at a given radio telescope. However, a few recent studies reported the detection of that signal at the radio band suggests the strength of this signal is somehow magnified. In this analysis, we study the prospects of detecting this signal at different frequency bands of the uGMRT where this signal is supposed to be amplified through the strong gravitational lensing by an isolated neutron star located in a cosmological distance. Our study shows the effects of the lensing parameters on the observables of that amplified signal and discusses its variation with the frequency bands considered here. We present a method to estimate the position and size of an isolated neutron star using the signal-to-noise ratio of that signal supposed to be detected at different frequency bands of the uGMRT. We discuss the scope of multi-messenger astronomy in the era of HI observation where the estimated lensing parameters can be cross-validated using the pulsar detection at the X-ray band from the same location in the sky. Our analysis is equally applicable to any radio telescope with given specifications.

astro-ph.CO↗
arXiv2023

Addressing the self-interaction for ELDER dark matter from the 21-cm signal

The self-interacting dark matter can affect various cosmological processes. Such interactions can be number conserving (\emph{e.g.} $2 \rightarrow 2$) or number violating (\emph{e.g.} $3 \rightarrow 2,\,4 \rightarrow 2$ etc.). The latter processes where three (or more) dark matter particles undergo self-annihilation/scattering to produce less number of dark matter is termed as ``Cannibalism'' process. In this work, the self-interaction of dark matter and the strength of such interactions are investigated in the light of experimental results of the global 21-cm spectrum of neural hydrogen from the era of cosmic dawn. From the present work, it appears that $2\rightarrow 2$ process is much more dominant over the $3\rightarrow 2$ process. It is also found that such interactions affect the dark matter-baryon elastic scattering cross-section. The study also indicates the presence of multi component dark matter of different mass range in the Universe.

astro-ph.CO↗
arXiv2022

Path integral approach to driven quantum harmonic oscillator using Markov chain Monte Carlo methods

We have simulated the ground states of quantum harmonic oscillators driven either by constant forces of different magnitudes or time-dependent driving forces. The expectation values of position for various combinations of mass, natural angular frequency, and the coupling constant $λ$ were calculated for both driving modes. For constant forcing, coherent states were obtained. The results for both forcing scenarios match the theoretically expected values almost exactly. For the simulations, the Metropolis algorithm was implemented on a discrete time lattice to evaluate the imaginary time path integral of the systems.

quant-ph↗
arXiv2021

Bounds on Dark Matter Annihilation Cross-sections from Inert Doublet Model in the context of 21 cm Cosmology of Dark Ages

We study the fluctuations in the brightness temperature of 21-cm signal $δT_{21}$ at the dark ages ($z\sim100$) with a dark matter candidate in Inter Doublet Model (IDM). We then explore the effects of different fractions of IDM dark matter on $δT_{21}$ signal. The IDM dark matter masses are chosen in few tens of GeV region as well as in the high mass region beyond 500 GeV. It has been observed that the $δT_{21}$ signal is more sensitive in the dark matter mass range of $70 - 80$ GeV. A lower bound on annihilation cross-section for this dark matter is also obtained analyzing the $δT_{21}$ signal. This is found to lie within the range $6.5 \times 10^{-29} \,\, \rm{cm^3 / sec} \leq \langleσv\rangle \leq 4.88\times 10^{-26}\,\, \rm{cm^ 3 / sec}$ for the IDM dark matter mass range $10 \, {\rm GeV} \leq m_χ\leq 990 \,{\rm GeV} $.

astro-ph.CO↗
arXiv2021

Bounds on abundance of primordial black hole and dark matter from EDGES 21-cm signal

The redshifted 21cm radio signal has emerged as an important probe for investigating the dynamics of the dark age Universe (recombination to reionization). In the current analysis, we explore the combined effect of primordial black hole (PBH) evaporation and the baryon-dark matter (DM) interaction in the 21cm scenario. The variation of brightness temperature shows remarkable dependence on the DM masses ($m_χ$) and the baryon-DM cross-sections ($\overlineσ_0$) besides the influences of the PBH parameters (mass $\mathcal{M_{\rm BH}}$ and initial mass fraction $β_{\rm BH}$). We address both upper and lower bounds on $β_{\rm BH}$ for a wide range of PBH mass in presence of different $m_χ$ and $\overlineσ_0$ by incorporating the observational excess $\left(-500^{+200}_{-500}\: {\rm mK}\right)$ of EDGES's experimental results. Finally, we address similar limits in the $m_χ$ - $\overlineσ_0$ parameter plane for different PBH masses.

astro-ph.CO↗
arXiv2021

Chandrasekhar limit for rotating quark stars

The limiting mass is a significant characteristic for compact exotic stars. In the case of quark stars, the limiting mass can be expressed in terms of fundamental constants and the Bag constant. In the present work, using bag model description, the maximum mass of a rotating quark star is found to depend on the rotational frequency apart from other fundamental parameters. The analytical results obtained agree with the results of several relevant numerical estimates as well as observational evidences.

astro-ph.HE↗
arXiv2021

Addressing $γ$-ray emissions from dark matter annihilations in 45 milky way satellite galaxies and in extragalactic sources with particle dark matter models

The mass to luminosity ratio of the dwarf satellite galaxies in the Milky Way suggests that these dwarf galaxies may contain substantial dark matter. The dark matter at the dense region such as within or at the vicinity of the centres of these dwarf galaxies may undergo the process of self annihilation and produce $γ$-rays as the end product. The satellite borne $γ$-ray telescope such as Fermi-LAT reported the detection of $γ$-rays from around 45 Dwarf Spheroidals (dSphs) of Milky Way. In this work, we consider particle dark matter models described in the literature and after studying their phenomenologies, we calculate the $γ$-ray fluxes from the self annihilation of the dark matter within the framework of these models in case of each of these 45 dSphs. we then compare the computed results with the observational upper bounds for $γ$-ray flux reported by Fermi-LAT and Dark Energy Survey (DES) for each of the 45 dSphs. The fluxes are calculated by adopting different dark matter density profiles. We then extend similar analysis for the observational upper bounds given by Fermi-LAT for the continuum $γ$-ray fluxes originating from extragalactic sources.

astro-ph.CO↗
arXiv2019

Mass and Life Time of Heavy Dark Matter Decaying into IceCube PeV Neutrinos

Considering that the ultrahigh energy (UHE) upgoing muon neutrino events around the PeV energy region observed by the IceCube are due to the decay of super heavy dark matter to neutrinos, we constrain the mass of the decaying dark matter and its decay lifetime using the IceCube analysis of these neutrinos in the PeV region. The theoretical fluxes are computed by adpoting the procedure given in the reference [1,2], where the DGLAP numerical evolutions of QCD cascades as well as electroweak corrections are included for evolving the decay process of the super heavy dark matter. Our results indicate that to explain the IceCube events around PeV region the decaying dark matter mass $m_χ$ would be $ \sim 5 \times 10^{7}$ GeV with the decay lifetime $τ\sim 7 \times 10^{28}$ sec.

hep-ph↗
arXiv2019

Intensification of Gravitational Wave Field Near Compact Star

The gravitational waves (GWs) has been a topic of interest for its versatile capabilities of probing several aspects of cosmology and early Universe. Gravitational lensing enhances further the extent of this sort of waves and upgrade our understanding to a next level. Besides several similarities with optical waves, GWs are capable of passing through optically opaque celestial objects like stars, exoplanets unlike light waves and manifest a different kind of lensing effect. In this work we have explored the lensing action of compact objects on gravitational waves using numerical means. After modeling the internal mass distribution of the compact objects by TOV equations and tracing wavefronts using geodesic equations, we have found that the GWs are indeed lensed in a manner analogous to the optical lensing of light in presence of a thick optical lens by producing spherical aberration in the focused waves. The distance to the best focused point shows significant dependence with the mass and radius of the lensing star and unlike gravitational lensing, the region inside and outside compact objects responds differently to the incoming waves.

gr-qc↗
arXiv2018

Speeding up of Binary Merger Due to "Apparent" Gravitational Wave Emissions

Gravitational waves from binary black hole pairs have emerged as an important observational tool in current times. The energy of the BH - BH binary pair is radiated in the form of gravitational waves and to compensate for that energy, kinetic energy of the system decreases gradually. Consequently the mutual separation of the objects decreases with time and tends to merge. The whole process may require a very long time comparable or longer than the age of the universe, specially in the case of low mass mergers. We have examined the case in which a massive object compared to the individual masses comprising the binary pair is present nearby such a system. We have found that in this case the merging process takes place much rapidly than that of the conventional BH-BH merging process. Scenarios with both an Intermediate Mass Black Hole (IBMH) ($10^{5}\:M_{\odot}$) as well as a Super Massive Black Hole (SMBH) have been studied and the latter has been found to provide a much higher overall rate for the BH-BH merger process.

gr-qc↗
arXiv2014

Some Aspects of Strange Matter in Astrophysics

The present work is connected with the investigation of the origin and properties of compact astrophysical objects endowed with strangeness, with the objective of finding out their relevance in the formation and evolution of the universe. In the first part of the thesis, Chap.~1-3, we discuss a model, proposed by us, to describe the propagation of small lumps of Strange Quark Matter (SQM) or strangelets, through the Terrestrial atmosphere. The theoretical results were found to be well correlated with exotic cosmic ray events characterized by very low charge to mass ratio. In the next part, we have investigated the other end of the mass spectrum of SQM. In Chap 5, we have developed an analytical expression for the Chandrasekhar Limit of Strange Quark Stars. The limit is found to depend on the fundamental constants (including the bag constant). In the last chapter we have endeavored to show that the quark nuggets, surviving the quark-hadron phase transition in the millisecond era of the early Universe can provide the required closure density and can merge to form compact quark matter objects, whose maximum mass would be governed by the formulation laid out in the preceding chapter. We have also found that these Cold Dark Matter objects can explain the recent astronomical observations of MACHOS by gravitational micro-lensing techniques in the Large Magellanic clouds in the Halo of our Galaxy.

astro-ph.HE↗
arXiv2006

Colour entangled orphan quarks and dark energy from cosmic QCD phase transition

The present day astrophysical observations indicate that the universe is composed of a large amount of dark energy (DE) responsible for an accelerated expansion of the universe, along with a sizeable amount of cold dark matter (CDM), responsible for structure formation. The explanations for the origin or the nature of both CDM and DE seem to require ideas beyond the standard model of elementary particle interactions. Here we show that CDM and DE both can arise from the standard principles of strong interaction physics and quantum entanglement.

hep-ph↗
arXiv2005

Cosmological dark energy from the cosmic QCD phase transition and colour entanglement

Recent astrophysical observations indicate that the universe is composed of a large amount of dark energy (DE) responsible for an accelerated expansion of the universe, along with a sizeable amount of cold dark matter (CDM), responsible for structure formation. At present, the explanations for the origin or the nature of both CDM and DE seem to require ideas beyond the standard model of elementary particle interactions. Here, for the first time, we show that CDM and DE can arise entirely from the standard principles of strong interaction physics and quantum entanglement. Quantitative agreement with the present data obtains without the need for any adjustable parameters.

hep-ph↗
arXiv2005

Strangeness, Cosmological Cold Dark Matter and Dark Energy

It is now believed that the universe is composed of a small amount of the normal luminous matter, a substantial amount of matter (Cold Dark Matter: CDM) which is non-luminous and a large amount of smooth energy (Dark Energy: DE). Both CDM and DE seem to require ideas beyond the standard model of particle interactions. In this work, we argue that CDM and DE can arise entirely from the standard principles of strong interaction physics out of the same mechanism.

astro-ph↗
arXiv2002

Massive Compact Halo Objects from the Relics of the Cosmic Quark-Hadron Transition

The existence of compact gravitational lenses, with masses around 0.5 (M_{\odot}), has been reported in the halo of the Milky Way. The nature of these dark lenses is as yet obscure, particularly because these objects have masses well above the threshold for nuclear fusion. In this work, we show that they find a natural explanation as being the evolutionary product of the metastable false vacuum domains (the so-called strange quark nuggets) formed in a first order cosmic quark-hadron transition.

astro-ph↗