Ashadul Halder
@bose.res.in
Post Doctoral Research Associate - I (PDRA-I). Department of Astrophysics and High Energy Physics
Post Doctoral Research Associate - I (PDRA-I)
RESEARCH, TEACHING, or OTHER INTERESTS
Astronomy and Astrophysics, Nuclear and High Energy Physics, Physics and Astronomy, General Physics and Astronomy
Scopus Publications
Scopus Publications
Ashadul Halder, Shashank Shekhar Pandey, and A.S. Majumdar
IOP Publishing
Abstract We formulate a model of spacetime with inhomogeneous matter distribution in multiple domains. In the context of the backreaction framework using Buchert's averaging procedure, we evaluate the effect of backreaction due to the inhomogeneities on the late time global evolution of the Universe. Examining the future evolution of this universe, we find that it can transit from the presently accelerating phase to undergo future deceleration. The future deceleration is governed by our model parameters. We constrain the model parameters using observational analysis of the Union 2.1 supernova Ia data employing the Markov Chain Monte Carlo method.
A. Chanda, A. Halder, A. S. Majumdar, and B. C. Paul
Springer Science and Business Media LLC
Aman Gupta, Debasish Majumdar, and Ashadul Halder
World Scientific Pub Co Pte Ltd
The Weakly Interacting Massive Particles (WIMPs) so far remain one of the most popular candidates for dark matter. If captured gravitationally inside the core of the Sun, these WIMPs may produce high-energy neutrinos as the end product in case they undergo self-annihilations at the solar core. In this work, we address the detectability of such neutrinos at the proposed KM3NeT detector. Upper bounds of the detection rate for such neutrinos at KM3NeT are computed for the case of a generic dark matter scenario and also when specific models for particle dark matter are chosen. In this work, upper bounds of muon event rates for different annihilating dark matter masses are computed for each of the cases of dark matter annihilation channels (e.g. [Formula: see text], [Formula: see text], [Formula: see text], etc.). These upper bounds are also computed by considering the dark matter scattering cross-section using upper bounds obtained from PandaX-4T direct dark matter search experiment.
Upala Mukhopadhyay, Debasish Majumdar, and Ashadul Halder
IOP Publishing
Abstract The evaporation of primordial black hole (PBH) via Hawking radiation influences the evolution of Inter Galactic Medium by heating up the latter and consequently affects the 21cm signal originated from the neutral Hydrogen atoms. In this work, we have considered EDGES observational data of 21cm line corresponding to cosmic dawn era to constrain the mass and the abundance of PBHs. In this context, two different PBH mass distributions namely, power law and lognormal mass distributions are considered to estimate the effects of PBH evaporation on the 21cm brightness temperature T 21. In addition to these two mass distributions, different monochromatic masses are also considered. The impacts of dark matter-baryon interactions on T 21 are also considered in this work along with the influences of PBH evaporation. Furthermore, adopting different monochromatic masses for PBHs, an attempt has been made to formulate a distribution for PBH masses by associating a probability weightage of the T 21 values (at z ∼ 17.2), within the range given by EDGES experiment, with the calculated T 21 values for each of the PBH mass values. The distribution best suited for the present purpose is found to be a combination of an error function and Owen function. Allowed contours in the parameter space of (initial PBH mass-dark matter mass) are obtained.
Ashadul Halder, Shashank Shekhar Pandey, and A.S. Majumdar
IOP Publishing
AbstractWe investigate the global 21-cm brightness temperature in the context of viscous dark energy (VDE) models. The bulk viscosity of dark energy perturbs the Hubble evolution of the Universe which could cool baryons faster, and hence, alter the 21-cm brightness temperature. An additional amount of entropy is also produced as an outcome of the viscous flow. We study the combined contribution of Hawking radiation from primordial black holes, decay and annihilation of particle dark matter and baryon-dark matter scattering in the backdrop of VDE models towards modification of the 21-cm temperature. We obtain bounds on the VDE model parameters which can account for the observational excess of the EDGES experiment (-500+200-500mK at redshift 14 <z< 20) due to the interplay of the above effects. Moreover, our analysis yields modified constraints on the dark matter mass and scattering cross-section compared to the case of the ΛCDM model.
Ashadul Halder and Madhurima Pandey
Oxford University Press (OUP)
ABSTRACT 21-cm radio signal has emerged as an important probe in investigating the dark age of the Universe (recombination to reionization). In the current analysis, we explore the combined effects of primordial black holes (PBHs), cooling-off of the baryonic matter due to dark matter (DM)–baryon collisions and interaction of DM and dark energy fluid on the 21-cm brightness temperature. The variation of brightness temperature shows remarkable dependence on DM mass (mχ) and the DM–baryon scattering cross-section (σ0). Bounds in mχ–σ0 parameter space are obtained for different possible PBH masses and for different interacting dark energy (IDE) models. These bounds are estimated based on the observed excess ($-500^{+200}_{-500}$ mK) of 21-cm brightness temperature by Experiment to Detect the Global Epoch of Reionization Signature experiment. Eventually, bounds on PBH mass is also obtained for different values of DM mass and for different IDE model coupling parameters. The compatibility of the constraints of the IDE models, in the estimated bounds is also addressed.
Madhurima Pandey, Debasish Majumdar, Amit Dutta Banik, and Ashadul Halder
World Scientific Pub Co Pte Ltd
Violation of equivalence principle predicts that neutrinos of different flavor couple differently with gravity. Such a scenario can give rise to gravity induced flavor oscillations in addition to the usual mass flavor neutrino oscillations during the neutrino propagation. Even if the equivalence principle is indeed violated, their measure will be extremely small. We explore the possibility to probe the violation of equivalence principle (VEP) for the case of long baseline (LBL) neutrinos in a 4-flavor neutrino framework (3 active + 1 sterile) where both mass and gravity induced oscillations are considered. To this end, we have explicitly calculated the oscillation probability in 4-flavor framework that includes in addition to the mass-flavor mixing in matter, the gravity-flavor mixing also. The energy eigenvalues are then obtained by diagonalizing such a 4-flavor mixing matrix. The formalism is then employed to estimate the wrong and right sign muon yields at a far detector for neutrinos produced in a neutrino factory and travel through the Earth matter. These results are compared with the similar estimations when the usual three active neutrinos are considered.
Ashadul Halder, Madhurima Pandey, Debasish Majumdar, and Rupa Basu
IOP Publishing
The primordial heavy or superheavy dark matter that could be created during the reheating or preheating stage of the Universe can undergo QCD cascade decay process to produce leptons or γ as end products. Although these could be rare decays, the energy involved in such decay process can influence 21-cm signal of hyperfine transition of neutral hydrogen during the reionization era. We explore in this work, possible multimessenger signals of such heavy dark matter decays. One of which could be the source of ultra high energy neutrino (of ∼ PeV energy regime) signals at IceCube detector whereas the other signal attributes to the cooling/heating of the baryons by the exchange of energy involved in this decay process and its consequent influence on 21-cm signal. The effect of evaporation of primordial black holes and baryon scattering with light cold dark matter are also included in relation to the evolution of the 21-cm signal temperature and their influence are also discussed.
Tista Mukherjee, Madhurima Pandey, Debasish Majumdar, and Ashadul Halder
World Scientific Pub Co Pte Lt
The recent results of IceCube Neutrino Observatory include an excess of PeV neutrino events which appear to follow a broken power-law different from the other lower energy neutrinos detected by IceCube. The possible astrophysical source of these neutrinos is still unknown. One possible source of such neutrinos could be the decay of nonthermal, long-lived heavy mass dark matter, whose mass should be [Formula: see text] GeV and could have produced at the very early Universe. They can undergo cascading decay via both hadronic and leptonic channels to finally produce such high energy neutrinos. This possibility has been explored in this work by studying the decay flux of these dark matter candidates. The mass and lifetime of such dark matter particles have been obtained by performing a [Formula: see text] fit with the PeV neutrino data of IceCube. We finally estimate the baryon asymmetry produced in the Universe due to such dark matter decay.
Ashadul Halder and Shibaji Banerjee
American Physical Society (APS)
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 Dark Matter - baryon interaction and primordial black holes (PBH) in the 21cm brightness temperature signal. The variation of brightness temperature shows remarkable dependence on dark matter mass ($m_{\\chi}$) and the dark matter - baryon cross-section ($\\overline{\\sigma}_0$) besides the PBH parameters (mass $\\mathcal{M_{\\rm BH}}$ and initial mass fraction $\\beta_{\\rm BH}$). We describe both upper and lower bounds on $\\beta_{\\rm BH}$ for a wide range of PBH mass for different chosen parameters of Dark Matter - baryon interaction using the observational excess $\\left(-500^{+200}_{-500}\\: {\\rm mK}\\right)$ of EDGES's experimental results. Finally, we address similar limits in the $m_{\\chi}$ - $\\overline{\\sigma}_0$ parameter plane for different values of black hole masses.
Ashadul Halder, Shibaji Banerjee, Sanjay K. Ghosh, and Sibaji Raha
American Physical Society (APS)
The limiting mass is a significant characteristic for compact exotic stars including quark stars and can be expressed in terms of fundamental constants and the Bag constant. In the present work, using bag model description, maximum mass of a rotating quark star is found to depend on the rotational frequency apart from other fundamental parameters. The analytical results obtained agrees with the result of several relevant numerical estimates as well as observational evidences.
Ashadul Halder, Shibaji Banerjee, Madhurima Pandey, and Debasish Majumdar
Oxford University Press (OUP)
ABSTRACT 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 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.
Madhurima Pandey, Debasish Majumdar, Ashadul Halder, and Shibaji Banerjee
Springer Singapore
Madhurima Pandey, Debasish Majumdar, Ashadul Halder, and Shibaji Banerjee
Elsevier BV