arXiv subjects

Abhijit Bandyopadhyay

Publications and source records attributed to Abhijit Bandyopadhyay.

At least 19 recordsLinked to original sources

arXiv2026

Cross-Spectral Reservoir Correlations as a Resource for Finite-Time Quantum Otto Engines

We investigate the thermodynamic consequences of longitudinal-transverse cross-spectral reservoir correlations in a finite-time quantum Otto engine with a two-level working medium. Each reservoir couples through excitation-relaxation and dephasing channels whose fluctuations are characterized by a Hermitian positive-semidefinite spectral-density matrix, with the off-diagonal elements encoding their cross correlations. The finite-time isochoric dynamics is derived within the second-order time-convolutionless framework, without imposing the Markov limit at the outset, so that finite reservoir-memory effects can enter through time-dependent dissipative and reservoir-induced coherent contributions. The resulting dynamics is then recast in Bloch-vector form to construct the stroke-resolved cycle dynamics. At fixed auto-spectral densities, cross-spectral correlations modify the populations and coherences of the working medium and thereby its thermodynamic performance. Increasing the correlation strength can enhance the output power, with the enhancement controlled by the cross-spectral phase and characteristic frequency scale. The correlations also reshape the transient cycle-to-cycle evolution and the approach to periodic operation, while the limit-cycle efficiency remains fixed at the Otto value for the population-preserving unitary strokes considered here. These results establish off-diagonal reservoir spectra as an additional resource for controlling finite-time quantum thermal machines.

quant-ph↗

arXiv2026

Effect of Cross-Spectral Correlations on Qubit Dynamics: Coherence Revival and Relaxation Modulation

We investigate the reduced dynamics of a qubit subject to correlated longitudinal and transverse noise arising from its coupling to a shared bosonic bath. The environmental fluctuations are characterized by a positive-semidefinite matrix-valued spectral density, whose complex off-diagonal elements encode correlations between dephasing and relaxation channels in the frequency domain. Within the second-order time-convolutionless framework, we derive closed time-local equations for the Bloch-vector components of the reduced density matrix. The numerical implementation is validated against the exact pure-dephasing solution and the established behavior of the transverse-coupling spin-boson model. When both noise channels are present, the cross-spectral terms couple the otherwise distinct dephasing and relaxation sectors, producing dynamics that cannot be reproduced by adding independent noise contributions. In particular, the correlations generate non-monotonic population relaxation and a transient revival of coherence following its initial decay. The strength, bandwidth, delay, and phase of the cross spectrum provide control parameters for the magnitude and temporal structure of these effects. Our results demonstrate that correlated multi-axis noise can redistribute coherence loss and energy relaxation in time, thereby providing finite temporal windows of enhanced coherence or suppressed relaxation within the weak-coupling regime.

quant-ph↗

arXiv2026

Tensor-Network-Based Unraveling of Non-Markovian Dynamics in Large Spin Chains via the Influence Martingale Approach

Classical simulation of open quantum system dynamics remains challenging due to the exponential growth of the Hilbert space, the need to accurately capture dissipation and decoherence, and the added complexity of memory effects in the non-Markovian regime. We develop an efficient algorithm for simulating both Markovian and non-Markovian dynamics in large one-dimensional quantum systems. Extending the Tensor Jump Method, which combines TDVP-based tensor-network evolution with a Suzuki--Trotter decomposition of stochastic trajectories, our approach incorporates time-dependent decay rates--treating positive rates as time-inhomogeneous Markovian processes and negative rates via the Influence Martingale formalism to unravel time-local non-Markovian dynamics. We further introduce the concept of the `influence radius' to achieve a resource-efficient framework enabling scalable simulations of open-system dynamics in the non-Markovian regime, as demonstrated for a one-dimensional transverse-field Ising chain comprising up to 100 spin qubits.

quant-ph↗

arXiv2025

IceCube PeV neutrinos from heavy dark matter decay with 12 years HESE data

The decay of superheavy dark matter from the early universe may undergo decay via QCD cascades and electroweak cascade to produce neutrinos as one of the decay products. We consider the neutrino events in and around PeV region reported by IceCube collaboration are due to the decay of such heavy dark matter. The neutrino spectrum could be from the decay processes via hadronic decay modes and/or leptonic decay modes. Using the numerical evolution of QCD cascades as well as electroweak corrections where use has been made of DGLAP equations, the neutrino fluxes from the heavy dark matter decay have been computed. The mass of the decaying superheavy dark matter and its decay lifetime have then been estimated from a $χ^2$ analysis of the IceCube 12-year data. The fractional contribution ($f_{\rm lep}$) of the leptonic decay channel in such a decay process is also estimated from the same $χ^2$ analyses. It is seen that to explain the IceCube 12-year ultrahigh energy (UHE) events the mass of a decaying superheavy dark matter would be $\sim9.4\times 10^6$ GeV and decay time $τ\simeq 4.2 \times 10^{28}$ second. It is also found that the lepton channel contribution is very small, $f_{\rm lep} \sim 0.001$.

hep-ph↗

arXiv2025

Exploring the evolution of structure growth in the universe with field-fluid interactions through dynamical stability analysis

We investigate an interacting quintessence dark energy - dark matter scenario and its impact on structure formation by analyzing the evolution of scalar perturbations. The interaction is introduced by incorporating a non-zero source term into the continuity equations of the two sectors (with opposite signs), modeled as $\bar{Q}_0 \equiv α\barρ_{\rm m}(H + κ\dotϕ)$. The coupling parameter $α$ and the parameter $λ$ involved in quintessence potential $V(ϕ) = V_0e^{-λκϕ}$, play crucial roles in governing the dynamics of evolution examined within the present framework. The cosmic evolution, within this context, is depicted as a first-order autonomous system of equations involving appropriately chosen dynamical variables. We analyzed the associated stability characteristics and growth rate of perturbations and obtained domains in the ($α-λ$) parameter space for which fixed points can exhibit stable and non-phantom accelerating solutions. Depending on its magnitude, the coupling parameter $α$ has the potential to change the characteristics of certain critical points, altering them from attractors to repellers. This model effectively captures the evolutionary features of the universe across its various phases at both the background and perturbation levels. The issue of cosmic coincidence can also be addressed within the framework of this model. We also observed that for a moderate strength of coupling, the growth rate of matter perturbation extends into the distant future.

gr-qc↗

arXiv2024

Observational constraints on generic models of non-minimal curvature-matter coupling

We investigate two classes of non-minimally coupled curvature-matter models in the FLRW universe with a perfect fluid and analyze their cosmological implications using Supernova Ia, Observed Hubble Data, and Baryon Acoustic Oscillation measurements. Non-minimal coupling is introduced via an additional term $\int d^4x \sqrt{-g} \mathcal{G}({\cal L}_{m}) f_2(R)$ in the Einstein-Hilbert action. To obtain observational constraints, we use an exponential-type fluid-pressure profile $p = p_0e^{ak}$ characterized by the dimensionless parameter $k$ and parameterize $f_2(R)$ as $R^n$ with another dimensionless parameter $n$. Two additional parameters, $α$ and $β$ in the functional form of $\mathcal{G}({\cal L}_{m})$ determine the coupling strength. We identify significant regions in the $(n, k)$-parameter space for fixed coupling strength values where non-minimally coupled models align with observed late-time cosmic evolution. Additionally, we explore and discuss features of energy transfer between the curvature and matter sectors using observational data.

gr-qc↗

arXiv2024

Dynamics of viable $f(R)$ dark energy models in the presence of Curvature-Matter interactions

In this study, we analyze the dynamics of the interaction between dark matter and curvature-driven dark energy in viable $f(R)$ gravity models using the framework of dynamical system analysis. We incorporate this interaction by introducing a source term in their respective continuity equations, given by $Q = \frac{κ^2 α}{3H}\tildeρ_{\rm m}ρ_{\rm curv}$, and examine two $f(R)$ gravity models that comply with local gravity constraints and cosmological viability criteria. Our findings reveal subtle modifications to fixed points and their stability criteria when compared to the conventional dynamical analysis of $f(R)$ gravity models without matter-curvature interactions as proposed and examined in prior literature. We determine the parameter limits associated with the stability criteria of critical points of the dynamical system for both the models. Additionally, the introduction of interaction reveals variations in the dynamical aspects of cosmic evolution, contingent on the range of values for the relevant model parameters. These results are consistent with the observed features of cosmic evolution within specific limits of the $f(R)$ models parameters and the coupling parameter $α$. We also examine the evolutionary dynamics of the universe in the interacting scenario through cosmological and cosmographic parameters. Our analysis demonstrates that the interacting scenario comprehensively accounts for all the observed phases of the universe's evolution and also results in a stable late-time cosmic acceleration. Additionally, we've studied how the coupling parameter affects evolutionary dynamics, particularly its impact on the matter-to-curvature energy density ratio. Our findings suggest that the chosen form of interaction can also address the cosmic coincidence problem.

gr-qc↗

arXiv2023

Observational constraints on non-minimally coupled curvature-matter models of gravity from the analysis of Pantheon data

We considered non-minimally coupled curvature-matter models of gravity in a FRW universe filled with perfect fluid and investigated its cosmological implications in the light of Pantheon compilation of 1048 Supernovae Ia data points along with 54 data points from Observed Hubble Data. The non-minimal curvature-matter coupling has been introduced by adding a term $\int \left[λR^n \mathcal{L}_m\right] \sqrt{-g}d^4x$ to the usual action for Einstein gravity involving the Einstein Hilbert action and minimally coupled matter action. We investigate the observational constraints on the non-minimal models by choosing two different kinds of parametrization of fluid-pressure profiles using a dimensionless parameter $k$. The interplay of the three parameters $λ,n,k$ plays a pivotal role in testing the consistency of non-minimally coupled fluid-curvature scenarios with the observed data. We found there exist large domains in the ($λ,n,k$)-parameter space for which models with non-minimal curvature-matter mixing stand as viable cosmological models reproducing the observed features of late-time cosmic evolution. We also commented on the possibility of `gravitationally induced particle creation' in the context of SNe Ia data.

gr-qc↗

arXiv2023

Investigating the accelerated expansion of the Universe through updated constraints on viable $f(R)$ models within the metric formalism

Modified theories of gravity encompass a class of $f(R)$-models that seek to elucidate the observed late time accelerated expansion of the universe. In this study, we examine a set of viable $f(R)$ models (Hu-Sawicki: two cases, Satrobinsky, Tsujikawa, exponential and arcTanh models) in metric formalism, using recent cosmological data sets: type Ia supernovae data, cosmic chronometer observations, baryonic acoustic oscillations data, data from H\textsc{ii} starburst galaxies, and local measurements of the Hubble parameter $H_0$. The model parameters are constrained using a Bayesian analysis with the Monte Carlo Markov Chain method. We employ statistical tools such as the Akaike Information Criterion, Bayesian Information Criterion, and reduced chi-square statistics to conduct a comparative investigation of these models. We determine the transition redshift, the evolution of total equation-of-state (EoS) parameter, and the EoS for the component responsible for current accelerated expansion to characterize the expansion's evolution. Taking into account the ``Hubble tension," we perform the study with and without a Gaussian prior for $H_0$ from local measurements. Our findings are as follows: (i) in many cases the $f(R)$ models are strongly favored over the standard $Λ$CDM model, (ii) the deviation parameter ($b$) significantly deviates from zero in several cases, (iii) the inclusion of local $H_0$ not only increases the fitted value of $H_0$ (as expected) but also affects the gap between predictions of $f(R)$ models and the $Λ$CDM model, and (iv) the relevant quantities characterizing the (accelerated) expansion of the universe obtained in our models are consistent with those obtained in a model-independent way by others. Our investigation and results present a compelling case for pursuing further research on $f(R)$ models with future observations to come.

astro-ph.CO↗

arXiv2022

Modified scaling in $k$-essence model in interacting dark energy - dark matter scenario

It has been shown by \textit{Scherrer and Putter et.al} that, when dynamics of dark energy is driven by a homogeneous $k-$essence scalar field $ϕ$, with a Lagrangian of the form $L = V_0F(X)$ with a constant potential $V_0$ and $X = \frac{1}{2}\nabla^μϕ\nabla_μϕ= \frac{1}{2}\dotϕ^2$, one obtains a scaling relation $X(dF/dX)^2 = Ca^{-6}$ , where $C$ is a constant and $a$ is the FRW scale factor of the universe. The separate energy conservation in the dark energy sector and the constancy of $k-$essence potential are instrumental in obtaining such a scaling. In this paper, we have shown that even when considering time-dependent interactions between dark energy and dark matter, the constancy of $k-$essence potential may lead to a modified form of scaling. We have obtained such a scaling relation for a particular class of parametrisation of the source term occurring in the continuity equation of dark energy and dark matter in the interacting scenario. We used inputs from the JLA analysis of luminosity distance and redshift data from Supernova Ia observations, to obtain the modified form of the scaling.

gr-qc↗

arXiv2022

Inelastic charged current interaction of supernova neutrinos in two-phase liquid xenon dark matter detectors

It has been known that neutrinos from supernova (SN) bursts can give rise to nuclear recoil (NR) signals arising from coherent elastic neutrino-nucleus scattering (CE$ν$NS) interaction, a neutral current (NC) process, of the neutrinos with xenon nuclei in future large (multi-ton scale) liquid xenon (LXe) detectors employed for dark matter search, depending on the SN progenitor mass and distance to the SN. In this paper, we show that the same detectors will also be sensitive to inelastic charged current (CC) interactions of the SN electron neutrinos ($ν_e$CC) with the xenon nuclei. Such interactions, while creating an electron in the final state, also leave the post-interaction target nucleus in an excited state, the subsequent deexcitation of which produces, among other particles, gamma rays and neutrons. The electron and deexcitation gamma rays will give ``electron recoil" (ER) type signals, while the deexcitation neutrons produce, through their multiple scattering on the xenon nuclei, further xenon nuclear recoils that will also give NR signals (in addition to those produced through the CE$ν$NS interactions). We discuss the observable scintillation and ionization signals associated with SN neutrino induced CE$ν$NS and $ν_e$CC events in a generic LXe detector and argue that upcoming sufficiently large LXe detectors should be able to detect both these types of events due to neutrinos from reasonably close by SN bursts. We also note that since the total CC induced ER and NR signals receive contributions predominantly from $ν_e$CC interactions while the CE$ν$NS contribution comes from NC interactions of {\emph all the six species of neutrinos}, identification of the $ν_e$CC and CE$ν$NS origin events may offer the possibility of extracting useful information about the distribution of the total SN explosion energy going into different neutrino flavors.

hep-ph↗

arXiv2022

Dynamical analysis of $k$-essence cosmology in the light of Supernova Ia observations

In this paper, we analyse the JLA data on Supernova observations in the context of $k-$essence dark energy model with Lagrangian $L=VF(X)$, with a constant potential $V$ and the dynamical term $X = (1/2)\nabla_μϕ\nabla_νϕ= \dotϕ^2/2$ for a homogeneous scalar field $ϕ(t)$, in a flat FRW spacetime background. Scaling relations are used to extract temporal behaviour of different cosmological quantities and the form of the function $F(X)$ from the data. We explore how the parameters of the model, viz. value of the constant potential $V$ and a constant $C$ appearing in the emergent scaling relation, control the dynamics of the model in the context of JLA data, by setting up and analysing an equivalent dynamical system described by a set of autonomous equations.

gr-qc↗

arXiv2022

Simulation of Nuclear Recoils due to Supernova Neutrino-induced Neutrons in Liquid Xenon Detectors

Neutrinos from supernova (SN) bursts can give rise to detectable number of nuclear recoil (NR) events through the coherent elastic neutrino-nucleus scattering (CE$ν$NS) process in large scale liquid xenon detectors designed for direct dark matter search, depending on the SN progenitor mass and distance. Here we show that in addition to the direct NR events due to CE$ν$NS process, the SN neutrinos can give rise to additional nuclear recoils due to the elastic scattering of neutrons produced through inelastic interaction of the neutrinos with the xenon nuclei. We find that the contribution of the supernova neutrino-induced neutrons ($ν$I$n$) can significantly modify the total xenon NR spectrum at large recoil energies compared to that expected from the CE$ν$NS process alone. Moreover, for recoil energies $\gtrsim20$ keV, dominant contribution is obtained from the ($ν$I$n$) events. We numerically calculate the observable S1 and S2 signals due to both CE$ν$NS and $ν$I$n$ processes for a typical liquid xenon based detector, accounting for the multiple scattering effects of the neutrons in the case of $ν$I$n$, and find that sufficiently large signal events, those with S1$\gtrsim$50 photo-electrons (PE) and S2$\gtrsim$2300 PE, come mainly from the $ν$I$n$ scatterings.

astro-ph.HE↗

arXiv2020

Time-dependent diffusive interactions between dark matter and dark energy in the context of $k-$essence cosmology

We investigated the scenario of time-dependent diffusive interaction between dark matter and dark energy and showed that such a model can be accommodated within the observations of luminosity distance - redshift data in Supernova Ia (SNe Ia) observations. We obtain constrains on different relevant parameters of this model from the observational data. We consider a homogeneous scalar field $ϕ(t)$ driven by a $k-$essence Lagrangian of the from $L = V(ϕ)F(X)$ with constant potential $V(ϕ) = V$, to describe the dynamics of dark energy in this model. Using the temporal behaviour of the FRW scale factor, the equation of state and total energy density of the dark fluid, extracted from the analysis of SNe Ia (JLA) data, we have obtained the time-dependence of the $k-$essence scalar field and also reconstructed form of the function $F(X)$ in the $k-$essence Lagrangian.

gr-qc↗

arXiv2019

Implications of JLA data for $k-$essence model of dark energy with given equation of state

We investigated implications of recently released `Joint Light-curve Analysis' (JLA) supernova Ia (SNe Ia) data for dark energy models with time varying equation of state of dark energy, usually expressed as $w(z)$ in terms of variation with corresponding redshift $z$. From a comprehensive analysis of the JLA data, we obtain the observational constraints on the different functional forms of $w(z)$, corresponding to different varying dark energy models often considered in literature, \textit{viz.} CPL, JBP, BA and Logarithmic models. The constraints are expressed in terms of parameters ($w_a, w_b$) appearing in the chosen functional form for $w(z)$, corresponding to each of the above mentioned models. Realising dark energy with varying equation of state in terms of a homogeneous scalar field $ϕ$, with its dynamics driven by a $k-$essence Lagrangian $L=VF(X)$ with a constant potential $V$ and a dynamical term $F(X)$ with $X=(1/2)\nabla^μϕ\nabla_μϕ$ we reconstructed form of the function $F(X)$. This reconstruction has been performed for different varying dark energy models at best-fit values of parameters ($w_a, w_b$) obtained from analysis of JLA data. In the context of $k-$essence model, we also investigate the variation of adiabatic sound speed squared, $c_s^2(z)$, and obtained the domains in ($w_a, w_b$) parameter space corresponding to the physical bound $ c_s^2>0$ implying stability of density perturbations.

gr-qc↗

arXiv2019

Realising Interactions Between Dark Matter and Dark Energy Using $k$-essence Cosmology

In this paper we exploit dynamics of a $k-$essence scalar field to realise interactions between dark components of universe resulting in a evolution consistent with observed features of late time phase of cosmic evolution. Stress energy tensor corresponding to a $k-$essence Lagrangian $L=V( ϕ)F(X)$ (where $X=\frac{1}{2}g^{μν}\nabla_μϕ\nabla_νϕ$) is shown to be equivalent to an ideal fluid with two components having same equation of state. Stress energy tensor of one of the components may be generated from a constant potential $k-$essence Lagrangian of form $L_1=V_0F(X)$ ($V_0$ constant) and that of other from another Lagrangian of form $L_2=V_1(ϕ)F(X)$ with $V=V_0 + V_1(ϕ)$. We have shown that, the unified dynamics of dark matter and dark energy described by a single scalar field $ϕ$ driven by a $k-$essence Lagrangian $L= V(ϕ)F(X)$ may be viewed in terms of diffusive interactions between the two hypothetical fluid components `1' and `2' with stress energy tensors equivalent to that of Lagrangians $L_1$ and $L_2$ respectively. The energy transfer between the fluid components is determined by functions $V(ϕ)$, $F(X)$ and their derivatives. Such a realisation is shown to be consistent with the Supernova Ia data with certain constraints on the temporal behaviour of $k-$essence potential $V(ϕ)$. We have described a methodology to obtain such constraints.

gr-qc↗

arXiv2018

Diffusive dark matter and dark energy scenario and $k-$essence in the context of Supernova Ia observations

We consider a unified model of interacting dark matter and dark energy to account for coincidence of present day dark energy and dark matter densities. We assume dark energy to be represented by a homogeneous scalar field $ϕ$ whose dynamics is driven by a (non-canonical) $k$-essence Lagrangian with constant potential and the particles of dark matter fluid undergoing velocity diffusion in background medium of the $k-$essence scalar field $ϕ$. This results in a transfer of energy from the fluid of dark matter to that of dark energy. This effect shows up as a source term in the continuity equation for dark matter and dark energy fluids. The source term involves a diffusion coefficient which is a measure of average energy transferred per unit time due to diffusion. We use time evolutions of the scale factor of background FRW spacetime, energy density and pressure of the dark fluid obtained from analysis of Supernova Ia data to obtain bounds on the diffusion parameter. For a constant potential in the $k$-essence Lagrangian, the temporal behaviour of a homogeneous $k$-essence field $ϕ$ is obtained for different values of the diffusion parameter. The obtained temporal behaviour may be expressed as $ϕ(t/t_0) = ϕ_0 + \varepsilon_1 (t/t_0 - 1) + \varepsilon_2 (t/t_0 -1)^2$, where $t_0$ is the time corresponding to present epoch. The coefficients $\varepsilon_1$ and $\varepsilon_2$ have been found and obtained as linear functions of diffusion parameter.

gr-qc↗

arXiv2017

Detecting supernova neutrinos with iron and lead detectors

Supernova (SN) neutrinos can excite the nuclei of various detector materials beyond their neutron emission thresholds through charged current (CC) and neutral current (NC) interactions. The emitted neutrons, if detected, can be a signal for the supernova event. Here we present the results of our study of SN neutrino detection through the neutron channel in lead ($^{208} {\rm Pb}$) and iron ($^{56} {\rm Fe}$) detectors for realistic neutrino fluxes and energies given by the recent Basel/Darmstadt simulations for a 18 solar mass progenitor SN at a distance of 10 kpc. We find that, in general, the number of neutrons emitted per kTon of detector material for the neutrino luminosities and average energies of the different neutrino species as given by the Basel/Darmstadt simulations are significantly lower than those estimated in previous studies based on the results of earlier SN simulations. At the same time, we highlight the fact that, although the total number of neutrons produced per kTon in a iron detector is more than an order of magnitude lower than that for lead, the dominance of the flavor blind NC events in the case of iron, as opposed to dominance of $ν_e$ induced CC events in the case of lead, offers a complementarity between the two detector materials so that simultaneous detection of SN neutrinos in a lead and a sufficiently large iron detector suitably instrumented for neutron detection may allow estimating the fraction of the total $μ$ and $τ$ flavored neutrinos in the SN neutrino flux and thereby probing the emission mechanism as well as flavor oscillation scenarios of the SN neutrinos.

astro-ph.HE↗