arXiv subjects

Dhananjay Singh

Publications and source records attributed to Dhananjay Singh.

14 recordsLinked to original sources

arXiv2026

In-medium properties of $D$ and $D^*$ mesons in magnetized isospin asymmetric nuclear matter

We investigate the impact of an external magnetic field on the in-medium properties of pseudoscalar ($D^0,D^+,D_s$) and vector ($D^{0*},D^{+*},D_{s}^{*}$) mesons in isospin asymmetric nuclear matter at finite temperature using a hybrid theoretical framework combining the chiral SU(3) quark mean-field (CQMF) model and the light-front quark model (LFQM). The medium-modified constituent quark masses, obtained from the CQMF model by including the magnetized Dirac sea contribution and anomalous magnetic moments of nucleons, are used as input to the LFQM calculations of meson masses, weak decay constants, and leading-twist distribution amplitudes. We further incorporate the Landau quantization of the charged mesons restricted to the lowest Landau level, while magnetic field induced pseudoscalar-vector mixing is taken into account for each $D$-$D^{*}$ doublet. We find that the external magnetic field enhances the effective masses and decay constants of both pseudoscalar and vector $D$ mesons by magnetic catalysis, while increasing baryon density generally induces an attractive mass shift and suppresses the decay constant and distribution amplitudes. The Landau level contribution further enhances the effective masses of the charged mesons, whereas the pseudoscalar-vector mixing produces a level repulsion, shifting the vector meson masses upward and the pseudoscalar meson masses downward. The interplay between magnetic field and density effects gives rise to a nontrivial medium behavior of heavy-light meson properties, with isospin asymmetry further inducing a small but systematic mass splitting across all the meson states considered. These results provide useful insights into heavy-flavor dynamics in strongly interacting matter and are relevant to ongoing and future studies at FAIR, NICA, and J-PARC.

hep-ph↗

arXiv2026

Fluctuations and correlations of conserved charges in the Polyakov chiral SU(3) quark mean field model

We compute generalized susceptibilities of conserved charges in the Polyakov chiral SU(3) quark mean field (PCQMF) model with the fermion vacuum term. At $μ_B = 0$ MeV, the calculation covers the diagonal $χ_n^{B,Q,S}$ through eighth order and all twelve independent fourth-order off-diagonal correlators. Extending to finite $μ_B$ at $μ_Q = μ_S = 0$, we compute $χ_n^B$ through eighth order, $χ_n^{Q,S}$ through fourth order, the second-order off-diagonals, all twelve fourth-order off-diagonal correlators, and the odd-order baryon susceptibilities $χ_1^B$, $χ_3^B$, $χ_5^B$. The calculation includes the vacuum term (vac=1) and is repeated for an independently refitted no-sea variant (vac=0). At $μ_B = 0$ MeV, the chiral pseudocritical temperature is $T_{\mathrm{pc}} = 170.5$ MeV (vac=1) and $166.4$ MeV (vac=0), while the Polyakov-loop deconfinement temperature is $T_{\mathrm{dec}} = 144.4$ MeV (vac=1) and $146.6$ MeV (vac=0). In vac=1, the derivative $-dΔ_{l,s}/dT$ of the subtracted chiral condensate develops an inflection near $T_{\mathrm{dec}}$. Higher derivative orders resolve the chiral-deconfinement splitting as twin maxima in $χ_4^B$ and $χ_6^Q$, twin minima in $χ_8^B$ and $χ_8^Q$, and multiple zero crossings in $χ_6^B$. Among the fourth-order off-diagonal correlators, vac=1 amplitudes exceed vac=0 in the BQ channel across the chiral crossover. The BS, QS, and mixed BQS components peak near the strange-melting temperature, where vac=0 dominates. Along $T_{\mathrm{pc}}(μ_B)$, the kurtosis ratio $R_{42}^B \equiv χ_4^B/χ_2^B$ of vac=1 crosses zero at $μ_B/T_{\mathrm{pc}} \approx 2.15$, while vac=0 stays positive across the full range. The higher-order ratios $R_{51}^B \equiv χ_5^B/χ_1^B$ and $R_{62}^B \equiv χ_6^B/χ_2^B$ start negative in vac=1 and grow more negative as $μ_B$ increases.

hep-ph↗

arXiv2026

Scaling in Supersonic Turbulence: Energy Spectra and Fluxes using High-Fidelity Direct Numerical Simulations

Supersonic turbulence is vital to astrophysical and high-speed engineering flows, yet its energy transfer mechanisms remain poorly understood. We present high-resolution ($1024^3$) direct numerical simulations (DNS) of forced compressible turbulence across a range of turbulent Mach numbers ($M_t = 0.2$ to $3.0$). Using the GPU-accelerated solver \texttt{DHARA} with a seventh-order, low-dissipation Targeted Essentially Non-Oscillatory (TENO) scheme, we resolve both fine-scale eddies and sharp shock fronts. Our results reveal a fundamental shift in the energy cascade in the supersonic regime. As $M_t$ increases, the rotational kinetic energy spectrum steepens from a Kolmogorov-like $k^{-5/3}$ scaling toward a Burgers-like $k^{-2}$ scaling. Conversely, the compressive energy spectrum becomes shallower, deviating from Burgers scaling. We show that these spectral modifications are driven by a dominant cross-scale transfer of energy from solenoidal to compressive modes within the inertial range, alongside significant contributions from pressure dilatation. Scaling laws for the root-mean-square compressive velocity ($U_C$) and compressive energy flux ($Π_C$) are found to mirror classical Burgers turbulence. Finally, we show that while energy injection rates depend on forcing type rather than Mach number, increased $M_t$ leads to decreased rotational dissipation and increased compressive dissipation and pressure dilatation. These findings elucidate intermodal energy cascade mechanisms, advancing our understanding of energy transfers in supersonic turbulence.

physics.flu-dyn↗

arXiv2025

Impact of anisotropy on QCD phase structure and transport coefficients of quark matter

Employing the Polyakov chiral SU(3) mean field (PCQMF) model, we investigate how momentum-space anisotropy, characteristic of quark-gluon plasma (QGP) in ultrarelativistic heavy-ion collisions (uRHIC), impacts the thermodynamic behavior and transport coefficients of strongly interacting quark matter. The momentum anisotropy is introduced via a small deformation in the momentum distribution, quantified by a spheroidal parameter $ξ$, which deforms the distribution functions and captures anisotropic effects to linear order. The PCQMF model captures key non-perturbative aspects of QCD, like chiral symmetry breaking, deconfinement dynamics through Polyakov loop potential, and is extended here to accommodate momentum-space anisotropy. We compute the modifications induced by momentum-space anisotropy to key thermodynamic observables including pressure $p$, energy density $ε$, entropy density $s$, speed of sound squared $c_s^2$, and specific heat $c_v$, alongside key transport coefficients, such as shear viscosity $η$, bulk viscosity $ζ_b$, and electrical conductivity $σ_{el}$. These coefficients are derived using the relativistic Boltzmann equation (RBE) under the relaxation time approximation (RTA). We find that even a weak anisotropy can lead to significant modifications in the thermodynamic response and transport behavior of quark matter. This underscores the importance of including momentum anisotropy for realistic modeling of the QCD medium across all energy regimes, from current studies at RHIC and LHC to future explorations of the high-density frontier at FAIR, NICA, and J-PARC.

hep-ph↗

arXiv2025

Mathematical formulation of mode-to-mode energy transfers and energy fluxes in compressible turbulence

Understanding compressible turbulence is critical for modeling atmospheric, astrophysical, and engineering flows. However, compressible turbulence poses a more significant challenge than incompressible turbulence. We present a novel mathematical framework to compute \textit{mode-to-mode energy transfer rates} and energy fluxes for compressible flows. The formalism captures detailed energy conservation within triads and allows decomposition of transfers into rotational, compressive, and mixed components, providing a clear picture of energy exchange among velocity and internal energy modes. We also establish analogies with incompressible hydrodynamic and magnetohydrodynamic flows, highlighting the framework's universality in studying energy transfers.

physics.flu-dyn↗

arXiv2025

Kaon structure modifications in strange hadronic matter

We present the valence quark distributions of the kaons in an isospin asymmetric dense strange medium consisting of nucleons and hyperons. The comparative analysis of in-medium parton distribution functions, electromagnetic form factors, and charge densities with respect to the free space distributions is studied in the light-cone quark model. The medium effects are incorporated in these distribution functions by using the effective quark masses, computed from the chiral SU(3) quark mean field model for finite values of baryonic density, isospin asymmetry, and strangeness fraction parameters. We observe a suppression of the kaon electromagnetic form factors and a redistribution of charge density in high-density strange matter.

hep-ph↗

arXiv2025

$D$ and $D^*$ mesons in isospin asymmetric nuclear medium

We investigate the properties of pseudoscalar $D$ and vector $D^*$ mesons in an isospin asymmetric nuclear medium using a hybrid approach that integrates the light-front quark model with the chiral SU(3) quark mean field model. The influence of isospin asymmetric nuclear medium is examined by utilizing the in-medium quark masses derived from the chiral SU(3) quark mean field model as an input in the light-front quark model to study the medium modification of $D$ mesons. We examine the impact of isospin asymmetry and baryon density at zero and finite temperature on the effective masses, weak decay constants, and distribution amplitudes of the pseudoscalar mesons $D^0$, $D^+$, $D_s$, and the vector mesons $D^{0*}$, $D^{+*}$, and $D_s^*$. Our results indicate significant medium-induced changes for pseudoscalar $D$ and vector $D^*$ mesons having $u/d$ as one of their constituent quarks, while a comparatively reduced effect is observed for mesons containing a strange quark. In contrast to temperature and isospin asymmetry, changes in the baryon density of the nuclear medium have a larger effect on different properties of $D$ and $D^*$ mesons.

hep-ph↗

arXiv2025

Finite size effects on the transport coefficients of strongly interacting QCD matter

The role of finite volume effects on the various transport coefficients of strongly interacting quark matter is analyzed in the Polyakov chiral SU(3) quark mean field model (PCQMF) at finite temperatures and chemical potentials incorporating fermionic vacuum term. Using a non-zero lower momentum cutoff and two different forms of the Polyakov loop potentials with quark back reaction, we study the following viscous properties: specific shear viscosity ($η/s$), normalized bulk viscosity ($ζ_b/s$), and conductivity properties: electrical conductivity ($σ_{el}/T$), thermal conductivity ($κ/T^2$). Along with this, some essential thermodynamic quantities in the context of transport properties, such as the square of the speed of sound ($c_s^2$) and the specific heat ($c_v$) at a constant volume, are computed. Finite size effects are applied to the vacuum term and its influence on the effective quark masses, thermodynamic quantities, and transport coefficients is studied. The temperature dependence of the transport coefficients is obtained through the kinetic theory approach with the relaxation time approximation. The size of the system has been found to have significant effects on all transport coefficients. We find that all the transport coefficients increase as the size of the system is reduced. We have also studied the specific sound channel $(η+3ζ_b/4)/s$ and the bulk-to-shear viscosity ratio $ζ_b/η$. The effect of finite size is found to be more prominent in the transition region and vanishes at high $T$. The transition temperature $T_χ$ is found to decrease as the system size (characterized by $R$) decreases. At finite chemical potentials, $T_χ$ is shifted to lower values compared to the case of the vanishing chemical potential.

hep-ph↗

arXiv2024

Impact of nonextensivity on the transport coefficients of strongly interacting QCD matter

Tsallis nonextensive statistics is applied to study the transport coefficients of strongly interacting matter within the Polyakov chiral SU(3) quark mean field model (PCQMF). Nonextensivity is introduced within the PCQMF model through a dimensionless $q$ parameter to examine the viscous properties such as shear viscosity ($η$), bulk viscosity ($ζ_b$), and conductive properties, including electrical conductivity ($σ_{el}$) and thermal conductivity ($κ$). Additionally, some key thermodynamic quantities relevant to the transport coefficients, like the speed of sound ($c_{sq}^2$) and specific heat at constant volume ($c_{vq}$), are calculated. The temperature dependence of the transport coefficients is explored through a kinetic theory approach with the relaxation time approximation. The results are compared to the extensive case where $q$ approaches 1. The nonextensive $q$ parameter is found to have a significant effect on all transport coefficients. We find that the nonextensive behaviour of the medium enhances both specific shear viscosity $η/s_q$ as well as conductive coefficients $σ_{el}/T$ and $κ/T^2$. In contrast, the normalised bulk viscosity $ζ_b/s_q$ is found to decrease as the nonextensivity of the medium increases. We have also studied the transport coefficients for finite values of chemical potentials. The magnitude of $η$, $σ_{el}$, and $κ$ increases at lower temperatures while $ζ$ is found to decrease for systems with non-zero chemical potential.

hep-ph↗

arXiv2024

Effect of Asymmetric Nuclear Medium on the Valence Quark Structure of the Kaons

The role of asymmetric nuclear medium on the properties of kaon is investigated at zero and finite temperature employing a hybrid approach integrating the light cone quark model (LCQM) and the chiral SU(3) quark mean field (CQMF) model. The in-medium quark masses are calculated within the CQMF model and are used as inputs to study the medium modifications in the kaon properties. In particular, we have analysed the impact of baryonic density, isospin asymmetry and temperature on the weak decay constant, distribution amplitudes (DAs) and parton quark distributions (PDFs) of valence quark structure of kaons. The effects of isospin asymmetry on the kaon doublet $K =\left(\begin{array}{c} K^{+} \\ K^{0} \end{array} \right)$ and antikaon doublet $\bar{K}$= ($K^-, \bar{K}^0$) are also studied. In order to compare with future experiments, we have also evolved the in-medium DAs and PDFs of kaons to $Q^2=16$ GeV$^2$. As compared to the temperature and isospin asymmetry, change in baryonic density of the nuclear medium makes more significant changes to the DAs and PDFs of kaons.

hep-ph↗

arXiv2024

Thermodynamic properties and phase diagram of quark matter within non-extensive Polyakov chiral SU (3) quark mean field model

In the present work, we apply Tsallis non-extensive statistics to study the thermodynamic properties and phase diagram of quark matter in the Polyakov chiral SU(3) quark mean field model. Within this model, the properties of the quark matter are modified through the scalar fields $σ, ζ, δ, χ$, the vector fields $ω, ρ$, $ϕ$, and the Polyakov fields $Φ$ and $\barΦ$ at finite temperature and chemical potential. Non-extensive effects have been introduced through a dimensionless parameter $q$ and the results are compared to the extensive case ($q\rightarrow1$). In the non-extensive case, the exponential in the Fermi-Dirac (FD) function is modified to a $q$-exponential form. The influence of $q$ parameter on the thermodynamic properties: pressure, energy, and entropy density as well as trace anomaly is investigated. The speed of sound and specific heat with non-extensive effects is also studied. Furthermore, the effect of non-extensivity on the deconfinement phase transition as well as the chiral phase transition of $u, d,$ and $s$ quarks is explored. We found that the critical end point (CEP), which defines the point in the $(T - μ)$ phase diagram where the order of the phase transition changes, shifts to a lower value of temperature, $T_{CEP}$, and a higher value of chemical potential, $μ_{CEP}$, as the non-extensivity is increased, i.e., $q>$1.

hep-ph↗

arXiv2022

Deviation in stellar trajectory induced by asymmetry in partial tidal disruption

We study partial tidal disruption and present a quantitative analysis of the orbital dynamics of the remnant self-bound core. We perform smoothed particle hydrodynamical simulations to show that partial disruption of a star due to the tidal field of a black hole leads to a jump in the specific orbital energy and angular momentum of the core. It directly leads to deviation in the core's trajectory apart from getting a boost in its velocity. Our analysis shows that the variations in the specific orbital energy and angular momentum are higher when the pericentre distance is lower. We conclude that higher mass asymmetry of the two tidal tails increases the magnitude of the trajectory deviations. Our study reveals that observable deviations are only possible when mass ratio $q \lesssim 10^3 $, which indicates the range of intermediate-mass black holes.

astro-ph.HE↗

arXiv2022

Optimizing Camera Placements for Overlapped Coverage with 3D Camera Projections

This paper proposes a method to compute camera 6Dof poses to achieve a user defined coverage. The camera placement problem is modeled as a combinatorial optimization where given the maximum number of cameras, a camera set is selected from a larger pool of possible camera poses. We propose to minimize the squared error between the desired and the achieved coverage, and formulate the non-linear cost function as a mixed integer linear programming problem. A camera lens model is utilized to project the cameras view on a 3D voxel map to compute a coverage score which makes the optimization problem in real environments tractable. Experimental results in two real retail store environments demonstrate the better performance of the proposed formulation in terms of coverage and overlap for triangulation compared to existing methods.

cs.CV↗

arXiv2020

SOS: Socially Omitting Selfishness in IoT for Smart and Connected Communities

Smart and Connected Communities (SCC) is an emerging field of Internet of Things (IoT), and it is having potential applications to improve human life. The improvement may be in terms of preservation, revitalization, livability, and sustainability of a community. The resources of the nodes and devices in the SCC have certain constraints that may not allow the devices and nodes to cooperate to save their resources such as memory, energy, and buffer, or simply maximize their performance. Thus, to stimulate the nodes to avoid selfish behavior, SSC needs a novel and well-organized solution to motivate nodes for cooperation. This article aims to resolve the issue of selfish behaviors in SCC and to encourage the nodes for cooperation. A novel mechanism Socially Omitting Selfishness (SOS) has been proposed to manage/eradicate selfishness using a socially-oriented election process. The election process elects different heads based on weight and cooperation (using VCG model). The election of heads and incentive mechanism encourages the nodes to show participation and behave as highly cooperative members of the community. Furthermore, an extended version of the Dempster-Shafer model has been used to discourage the selfish behavior of the participating nodes in the SOS scheme. It uses different monitoring and gateway nodes to efficiently employ the proposed scheme. A mathematical model has been developed for the aforementioned aspects and simulated through the NS2 simulation environment to analyze the performance of SOS. The results of the proposed scheme outperform the contemporary schemes in terms of average delivery delay, packet delivery ratio, throughput, and average energy.

cs.DC↗