arXiv subjects

Sabyasachi Ghosh

Publications and source records attributed to Sabyasachi Ghosh.

At least 37 records · Page 2Linked to original sources

arXiv2025

Effect of Coriolis Force on Diffusion of D Meson

We have attempted to calculate and estimate the spatial diffusion coefficients of D meson through rotating hadron resonance gas, which can be produced in the late stage of peripheral heavy ion collisions. Employing the framework of kinetic theory in relaxation time approximation, and using Einstein's diffusion relation, one can express the spatial diffusion coefficients of D meson as a ratio of its conductivity to its susceptibility. Here, we have tuned D meson relaxation time from the knowledge of earlier works on its spatial diffusion estimations, and then we have extended the framework for the finite rotation picture of hadronic matter, where only the effect of Coriolis force is considered. Our study also revealed the anisotropic nature of diffusion in the presence of rotation with future possibilities of phenomenological signature.

hep-ph↗

arXiv2025

Numerically studying Pesticide diffusion in air using Langevin formalism

The use of pesticides for enhancing crop yield and preventing infestations is a widespread agricultural practice. However, in recent years, there has been a growing shift toward traditional chemical-free organic farming. Regulatory frameworks impose specific distance requirements between organic farms and neighboring lands where chemical pesticides are used to minimize cross-contamination. In this work, we numerically analyze the spread of pesticide droplets to adjacent fields under varying weather conditions, providing a systematic analysis that highlights conditions where existing guidelines might require reassessment. We employ the formalism of the Langevin equations to model the diffusion of pesticide particles and their transport due to wind and other environmental factors. Assuming a non-relativistic, classical diffusion framework, we track the dispersion of commonly used pesticides to assess their potential contamination range. We present our key findings, discuss their implications, and, toward the end, outline possible directions for future research.

physics.app-ph↗

arXiv2024

Dynamics of Hot QCD Matter 2024 -- Bulk Properties

The second Hot QCD Matter 2024 conference at IIT Mandi focused on various ongoing topics in high-energy heavy-ion collisions, encompassing theoretical and experimental perspectives. This proceedings volume includes 19 contributions that collectively explore diverse aspects of the bulk properties of hot QCD matter. The topics encompass the dynamics of electromagnetic fields, transport properties, hadronic matter, spin hydrodynamics, and the role of conserved charges in high-energy environments. These studies significantly enhance our understanding of the complex dynamics of hot QCD matter, the quark-gluon plasma (QGP) formed in high-energy nuclear collisions. Advances in theoretical frameworks, including hydrodynamics, spin dynamics, and fluctuation studies, aim to improve theoretical calculations and refine our knowledge of the thermodynamic properties of strongly interacting matter. Experimental efforts, such as those conducted by the ALICE and STAR collaborations, play a vital role in validating these theoretical predictions and deepening our insight into the QCD phase diagram, collectivity in small systems, and the early-stage behavior of strongly interacting matter. Combining theoretical models with experimental observations offers a comprehensive understanding of the extreme conditions encountered in relativistic heavy-ion and proton-proton collisions.

nucl-th↗

arXiv2024

Effect of Coriolis Force on Electrical Conductivity Tensor for Rotating Hadron Resonance Gas

We have investigated the influence of the Coriolis force on the electrical conductivity of hadronic matter formed in relativistic nuclear collisions, employing the Hadron Resonance Gas (HRG) model. A rotating matter in the peripheral heavy ion collisions can be expected from the initial stage of quark matter to late-stage hadronic matter. Present work is focused on rotating hadronic matter, whose medium constituents - hadron resonances can face a non-zero Coriolis force, which can influence the hadronic flow or conductivity. We estimate this conductivity tensor by using the relativistic Boltzmann transport equation. In the absence of Coriolis force, an isotropic conductivity tensor for hadronic matter is expected. However, our study finds that the presence of Coriolis force can generate an anisotropic conductivity tensor with three main conductivity components - parallel, perpendicular, and Hall, similar to the effect of Lorentz force at a finite magnetic field. Our study has indicated that a noticeable anisotropy of conductivity tensor can be found within the phenomenological range of angular velocity $Ω= 0.001-0.02$ GeV and hadronic scattering radius $a=0.2-2$ fm.

hep-ph↗

arXiv2024

Effect of the Coriolis force on the electrical conductivity of quark matter: A nonrelativistic description

Rotating quarks and hadronic systems, produced in peripheral heavy ion collisions, can experience Coriolis force and other forces due to rotational motion. Considering only the effect of Coriolis force, we have calculated the electrical conductivity for non-relativistic rotating matter using the Relaxation Time Approximation based Boltzmann transport equation. A similarity in mathematical calculations of electrical conductivity at finite rotation and finite magnetic fields is exposed, where an equivalence role between Coriolis force on massive particle's motion and Lorentz force on charged particle's motion is noticed. As the beginning level step, we consider only the Coriolis force in the non-relativistic formalism, which will be extended in the future towards the relativistic case, and to adopt other forces for a more realistic description of the rotating quark and hadronic system.

nucl-th↗

arXiv2024

Transport Coefficients of relativistic matter: A detailed formalism with a gross knowledge of their magnitude

The present review article has attempted a compact formalism description of transport coefficient calculations for relativistic fluid, which is expected in heavy ion collision experiments. Here, we first address the macroscopic description of relativistic fluid dynamics and then its microscopic description based on the kinetic theory framework. We also address different relaxation time approximation-based models in Boltzmann transport equations, which make a sandwich between Macro and Micro frameworks of relativistic fluid dynamics and finally provide different microscopic expressions of transport coefficients like the fluid's shear viscosity and bulk viscosity. In the numeric part of this review article, we put stress on the two gross components of transport coefficient expressions: relaxation time and thermodynamic phase-space part. Then, we try to tune the relaxation time component to cover earlier theoretical estimations and experimental data-driven estimations for RHIC and LHC matter. By this way of numerical understanding, we provide the final comments on the values of transport coefficients and relaxation time in the context of the (nearly) perfect fluid nature of the RHIC or LHC matter.

nucl-th↗

arXiv2024

Shear viscosity expression for a graphene system in relaxation time approximation

We have gone through the detailed microscopic calculation of the shear viscosity of a 2-dimensional graphene system in the relaxation time approximation-based kinetic theory framework. After getting its final expressions, we compared it with the shear viscosity expressions of other possible 2-dimensional as well as 3-dimensional nonrelativistic and ultra-relativistic fluid systems. The aim of the comparison is to reveal how their different one-body dispersion relations affect their many-body fluid properties like shear viscosity and the viscosity to entropy density ratio. It is also aimed to reveal the 3-dimension to the 2-dimension transformation of their mathematical structures. We have numerically explored the differences in their order of magnitude and dependence on thermodynamical parameters-temperature and chemical potential. Marking two thermodynamical domains-Dirac fluid and Fermi liquid-for a 2-dimensional graphene system, we have noticed that shear viscosity, entropy density as well as their ratios decrease toward saturated values when one goes from Fermi liquid to Dirac fluid domain. When one shifts from mili-electron volt scales of temperature and chemical potential in condensed matter physics location to their mega-electron volt scales in high energy physics location, then the same results may be expected for hot quark matter case, where the transition from the neutron star to early universe domains may be considered as Fermi liquid to Dirac fluid transition.

nucl-th↗

arXiv2024

Effect of Coriolis force on the shear viscosity of quark matter: A nonrelativistic description

Shear viscosity becomes anisotropic in a rotating medium. It is discovered here that for rotating thermalized quantum systems such as those created in relativistic heavy-ion collisions, the coeffficient of shear viscosity breaks up into five independent components. Similar phenomena were also discovered for quark-gluon plasma in the presence of the magnetic field. Like the Lorentz force at a finite magnetic field, the Coriolis force also creates anisotropic viscosity at nonzero rotation. As a first approach, for simplicity, the calculations are done in the nonrelativistic prescription, with a future proposal to extend it toward a relativistic description. Introducing the Coriolis force term in relaxation time approximated Boltzmann transport equation, we have found different effective relaxation times along the parallel, perpendicular, and Hall directions in terms of actual relaxation time and rotating time period. Comparing the present formalism with the finite magnetic field picture, we have shown the equivalence of roles between the rotating and cyclotron time periods, where the rotating time period is inverse of twice the angular velocity.

nucl-th↗

arXiv2024

Compressive Recovery of Signals Defined on Perturbed Graphs

Recovery of signals with elements defined on the nodes of a graph, from compressive measurements is an important problem, which can arise in various domains such as sensor networks, image reconstruction and group testing. In some scenarios, the graph may not be accurately known, and there may exist a few edge additions or deletions relative to a ground truth graph. Such perturbations, even if small in number, significantly affect the Graph Fourier Transform (GFT). This impedes recovery of signals which may have sparse representations in the GFT bases of the ground truth graph. We present an algorithm which simultaneously recovers the signal from the compressive measurements and also corrects the graph perturbations. We analyze some important theoretical properties of the algorithm. Our approach to correction for graph perturbations is based on model selection techniques such as cross-validation in compressed sensing. We validate our algorithm on signals which have a sparse representation in the GFT bases of many commonly used graphs in the network science literature. An application to compressive image reconstruction is also presented, where graph perturbations are modeled as undesirable graph edges linking pixels with significant intensity difference. In all experiments, our algorithm clearly outperforms baseline techniques which either ignore the perturbations or use first order approximations to the perturbations in the GFT bases.

eess.SP↗

arXiv2023

Effect of magnetic field on jet transport coefficient $\hat{q}$

We report the estimation of jet transport coefficient, $\hat{q}$ for quark- and gluon-initiated jets using a simple quasi-particle model in absence and presence of magnetic field. This model introduces a temperature and magnetic field-dependent degeneracy factor of partons, which is tuned by fitting the entropy density of lattice quantum chromodynamics data. At a finite magnetic field, $\hat{q}$ for quark jets splits into parallel and perpendicular components whose magnetic field dependence comes from two sources: the field-dependent degeneracy factor and the phase space part guided from the shear viscosity to entropy density ratio. Due to the electrically neutral nature of gluons, the estimation of $\hat{q}$ for gluon jets is affected only by the field-dependent degeneracy factor. In presence of a finite magnetic field, we find a significant enhancement in $\hat{q}$ for both quark- and gluon-initiated jets at low temperature, which gradually decreases towards high temperature. We compare the obtained results with the earlier calculations based on the anti-de Sitter/conformal field theory correspondence, and a qualitatively similar trend is observed. The change in $\hat{q}$ in presence of magnetic field is, however, quantitatively different for quark- and gluon-initiated jets. This is an interesting observation which can be explored experimentally to verify the effect of magnetic field on $\hat{q}$.

hep-ph↗

arXiv2023

Effect of time-varying electromagnetic field on Wiedemann-Franz law in a hot hadronic matter

We have estimated the electrical and thermal conductivity of a hadron resonance gas for a time-varying magnetic field, which is also compared with constant and zero magnetic field cases. Considering the exponential decay of electromagnetic fields with time, a kinetic theory framework can provide the microscopic expression of electrical and thermal conductivity in terms of relaxation and decay times. In the absence of the magnetic field, only a single time scale appears, and in the finite magnetic field case, their expressions carry two-time scales, relaxation time and cyclotron time period. Estimating the conductivities for HRG matter in three cases -- zero, constant, and time-varying magnetic fields, we have studied the validity of the Wiedemann-Franz law. We noticed that at a high-temperature domain, the ratio saturates at a particular value, which may be considered as Lorenz number of the hadron resonance gas. With respect to the saturation values, the deviation of the Wiedemann-Franz law has been quantified at the low-temperature domain. For the first time, the present work sketches this quantitative deviation of the Wiedemann-Franz law for hadron resonance gas at a constant and a time-varying magnetic field.

hep-ph↗

arXiv2023

Quantum version of transport coefficients in Nambu--Jona-Lasinio model at finite temperature and strong magnetic field

We have estimated parallel and perpendicular components of electrical conductivity and shear viscosity of quark matter at finite magnetic field and temperature by using their one-loop Kubo expressions in the framework of Nambu--Jona-Lasinio (NJL) model. At finite magnetic field, a non-trivial medium dependence of those quantities can be found. Previously these NJL-profiles have been addressed in relaxation time approximation, where cyclotron motion of quarks with medium dependent mass plays the key role. With respect to the earlier estimations, the present work provides further enriched profiles via Kubo framework, where field theoretical descriptions of quark transport with medium dependent mass and (Landau) quantized energy have been identified as the key ingredients. Hence the present study can be considered as the complete quantum field theoretical description of the transport coefficients in the framework of NJL model at finite temperature and magnetic field.

hep-ph↗

arXiv2023

Efficient Neural Network based Classification and Outlier Detection for Image Moderation using Compressed Sensing and Group Testing

Popular social media platforms employ neural network based image moderation engines to classify images uploaded on them as having potentially objectionable content. Such moderation engines must answer a large number of queries with heavy computational cost, even though the actual number of images with objectionable content is usually a tiny fraction. Inspired by recent work on Neural Group Testing, we propose an approach which exploits this fact to reduce the overall computational cost of such engines using the technique of Compressed Sensing (CS). We present the quantitative matrix-pooled neural network (QMPNN), which takes as input $n$ images, and a $m \times n$ binary pooling matrix with $m < n$, whose rows indicate $m$ pools of images i.e. selections of $r$ images out of $n$. The QMPNN efficiently outputs the product of this matrix with the unknown sparse binary vector indicating whether each image is objectionable or not, i.e. it outputs the number of objectionable images in each pool. For suitable matrices, this is decoded using CS decoding algorithms to predict which images were objectionable. The computational cost of running the QMPNN and the CS algorithms is significantly lower than the cost of using a neural network with the same number of parameters separately on each image to classify the images, which we demonstrate via extensive experiments. Our technique is inherently resilient to moderate levels of errors in the prediction from the QMPNN. Furthermore, we present pooled deep outlier detection, which brings CS and group testing techniques to deep outlier detection, to provide for the case when the objectionable images do not belong to a set of pre-defined classes. This technique enables efficient automated moderation of off-topic images shared on topical forums dedicated to sharing images of a certain single class, many of which are currently human-moderated.

cs.CV↗

arXiv2023

Spatial diffusion of heavy quarks in background magnetic field

The ratio of shear viscosity to entropy density shows a valley-shaped pattern well-known in the community of heavy-ion physics. Diffusion coefficients of heavy quark and meson shows the similar structure, and both sketches have become quite popular in the community. Present work has attempted a finite magnetic field extension of the diffusion coefficients of heavy quark and meson. Using Einstein's diffusion relation, we calculated heavy quark and heavy meson diffusion by the ratio of conductivity to susceptibility in the kinetic theory framework of relaxation time approximation. The relaxation time of heavy quark and meson are tuned from the knowledge of earlier works on spatial diffusion estimations, and then we have extended the framework for a finite magnetic field, where our outcomes have revealed two aspects - anisotropic and quantum aspects of diffusion with future possibilities of phenomenological signature.

hep-ph↗

arXiv2023

Estimation of transport coefficients of dense hadronic and quark matter

We calculate the transport coefficients like shear viscosity and electrical conductivity with respect to density of dense hadronic and quark matter. By considering the simple massless limit for the quark matter and two different effective models for the hadronic matter, we have estimated the transport coefficients of the two phases separately. We have sketched the density profile of the transport coefficients in two parts viz. the phase-space part and the relaxation time part. By calculating the shear viscosity to density ratio, we have also explored the nearly perfect fluid domain of the quark and hadronic matter.

nucl-th↗

arXiv2023

Quantum expression for the electrical conductivity of massless quark matter and of the hadron resonance gas in the presence of a magnetic field

We have studied the classical and quantum expressions of electrical conductivity and their numerical estimation in the presence of a magnetic field for hadron resonance gas (HRG) and massless quark matter. Classical results of transport coefficients of HRG matter in the presence of a magnetic field were studied previously by Dash et al. [Phys. Rev. D 102, 016016 (2020)] using the standard relaxation time approximation in the Boltzmann equation. In the same reference, the transition from isotropic transport coefficients to anisotropic coefficients in the presence of a magnetic field was also estimated for massless and HRG matter. This led to an upper limit or Stefan-Boltzmann (SB) type limit to the nonperturbative domain transition of transport coefficients. In a similar context, the present work has concentrated on the classical to quantum transition of HRG transport from the domain of high temperature and low magnetic field to that of low temperature and high magnetic field. We have also compared the quantum modification of HRG results with that of massless quark matter, where we observed an opposite trend. A similar kind of quantum effect is also noticed between mesons and baryons due to their different particle distribution functions. Despite the fact that HRG contains both mesons and baryons, Landau quantization of its net magnetothermodynamic phase space reveals meson- or boson-dominated quantum modification. That is why the quantum modification of HRG results reveals the opposite trend from that of massless quark matter, which faces fermionic quantum modification.

nucl-th↗

arXiv2022

Anisotropic tomography of heavy quark dissociation by using general propagator structure at finite magnetic field

In this work we have explored the imaginary part of the Heavy Quark (HQ) potential and subsequently the dissociation of heavy quarkonia at finite temperature and magnetic field. With respect to earlier investigations on this topic, present work contain three new ingredients. First one is considering all Landau level summation, for which present work can be applicable in entire magnetic field domain - from weak to strong. Second one is the general structure of the gauge boson propagator in a hot magnetized medium, which is used here in heavy quark potential problem first time. Third one is a rich anisotropic structure of the complex heavy quark potential, which explicitly depends on the longitudinal and transverse distance. By comparing with earlier references, we have attempted to display our new contributions by plotting heavy quark potential tomography and dissociation probability at finite temperature and magnetic field.

hep-ph↗

arXiv2022

Dynamics of Hot QCD Matter -- Current Status and Developments

The discovery and characterization of hot and dense QCD matter, known as Quark Gluon Plasma (QGP), remains the most international collaborative effort and synergy between theorists and experimentalists in modern nuclear physics to date. The experimentalists around the world not only collect an unprecedented amount of data in heavy-ion collisions, at Relativistic Heavy Ion Collider (RHIC), at Brookhaven National Laboratory (BNL) in New York, USA, and the Large Hadron Collider (LHC), at CERN in Geneva, Switzerland but also analyze these data to unravel the mystery of this new phase of matter that filled a few microseconds old universe, just after the Big Bang. In the meantime, advancements in theoretical works and computing capability extend our wisdom about the hot-dense QCD matter and its dynamics through mathematical equations. The exchange of ideas between experimentalists and theoreticians is crucial for the progress of our knowledge. The motivation of this first conference named "HOT QCD Matter 2022" is to bring the community together to have a discourse on this topic. In this article, there are 36 sections discussing various topics in the field of relativistic heavy-ion collisions and related phenomena that cover a snapshot of the current experimental observations and theoretical progress. This article begins with the theoretical overview of relativistic spin-hydrodynamics in the presence of the external magnetic field, followed by the Lattice QCD results on heavy quarks in QGP, and finally, it ends with an overview of experiment results.

nucl-th↗