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Vikash Kumar Ojha

Publications and source records attributed to Vikash Kumar Ojha.

17 recordsLinked to original sources
arXiv2026

Electron-Ion Collision Environment: Distribution of Quark Spin and Orbital Angular Momentum

The future Electron-Ion Collider (EIC) will enable measurements of the same partonic distributions inside both the proton and the nucleus through electron-proton (eP) and electron-ion (eA) collisions. This capability motivates the present theoretical study of the distributions of quark spin and orbital angular momentum within the proton and the nucleus. To map the eP and eA collision environments, we employ the Nambu--Jona-Lasinio (NJL) model at finite nuclear density to determine the constituent quark masses at zero nuclear density and near the nuclear saturation density. Using these quark mass inputs, we calculate the generalized transverse momentum-dependent parton distributions (GTMDs) associated with quark orbital angular momentum (OAM), spin, and spin-orbit correlations within the light-front dressed quark model. Furthermore, inspired by the nuclear suppression factor widely used in heavy-ion collision experiments, we introduce a set of GTMD ratios between eP and eA collisions. Any deviation of these ratios from unity provides an indirect measure of many-body nuclear density effects arising from non-perturbative quantum chromodynamics (QCD).

hep-ph↗
arXiv2026

Probing information theoretic measures of nonlinear ultracold quantum gases using phase-space distributions

We use phase space distributions, specifically the Wigner and Husimi quasi probability distributions, to study harmonically trapped Bose--Einstein condensate described by the Gross Pitaevskii equation. From the mean field ground state wavefunction we construct both distributions and their position and momentum space marginals and we use these to compute a comprehensive set of information theoretic measures: Shannon, Wehrl, and Rényi entropies; Fisher information; cumulative and cross cumulative residual entropies; mutual information; and Kullback--Leibler, Jeffreys, Cauchy Schwarz, and Rényi divergences. Studying these quantities as a function of the $s$-wave scattering length for a representative Rb-85 condensate, we find that stronger repulsive interactions drive increased phase space delocalization, seen by a monotonic growth of Shannon and Wehrl entropies, while the Fisher information shows the complementary trend -- increasing in position space and decreasing in momentum space in a manner consistent with the global Fisher uncertainty bound. Rényi entropies and divergence measures further reveal a systematic suppression of non classical interference and a shift toward more classical phase space structure in moving from the Wigner to the Husimi representation, with Wigner and Husimi based mutual informations converging at larger interaction strength. We note that, because the Gross Pitaevskii framework treats the many body state as a mean field product, the mutual information computed here quantifies statistical dependence between the conjugate phase space variables of the effective one body distribution rather than genuine particle particle entanglement.

quant-ph↗
arXiv2026

Gluon Wigner distributions with transverse polarization at non-zero skewness

We investigate the gluon Wigner distributions at non-zero skewness using light-front wave functions (LFWFs) in the dressed quark model, where the target state is a quark dressed with a gluon in the leading-order Fock space expansion. Our analysis focuses on the configurations in which the gluon, the target, or both are transversely polarized. We derive analytical expressions for the Wigner distributions in the boost-invariant longitudinal space ($σ$) for transversely polarized configurations and observe a diffraction-like oscillatory pattern in $σ$-space, analogous to that reported earlier for unpolarized and longitudinally polarized gluons.

hep-ph↗
arXiv2026

Photon angular momentum near Planck scale

We study the angular momentum structure of the gauge field in Lorentz covariant relativistic generalized uncertainty principle (RGUP) framework incorporating Planck scale minimal length effects. Using Noether's theorem for higher derivative RGUP-modified gauge field Lagrangian, we obtain the canonical and symmetric (Belinfante) energy-momentum tensors and the corresponding gauge spin and orbital angular momentum currents. We show that the canonical and Belinfante-Rosenfeld angular-momentum tensors continue to satisfy the standard conservation law in the presence of Planck-scale corrections. %These results support the stability of fundamental conservation laws under high-energy modifications. The RGUP corrections introduce higher-order contributions to the angular momentum density and momentum flow, yielding a modified Poynting vector, with the Maxwell limit recovered for vanishing RGUP parameter.

hep-ph↗
arXiv2025

Unveiling Skewness Dependence of Quark Wigner Distributions

We present a detailed investigation of the skewness dependence of quark Wigner distributions within the light-front dressed quark model. While previous studies have largely focused on the forward limit, we explore the impact of nonzero longitudinal momentum transfer (\(ξ\neq 0\)) on the full set of leading-twist quark Wigner distributions across various polarization configurations. We observe characteristic distortions in the spatial and momentum correlations with increasing skewness, including the emergence of dipole and quadrupole patterns, asymmetries, and localization effects. These features reflect spin-orbit correlations and quantum interference between light-front wave function components with differing orbital angular momentum.

hep-ph↗
arXiv2025

Quark Wigner distribution in frame-independent 3-dimensional space

We investigate the quark Wigner distribution in a frame-independent, three-dimensional position space within the framework of the dressed quark model. It is observed that the distributions are concentrated near the center of the target and gradually diminish as one moves away in both the longitudinal and transverse directions. The distribution exhibits symmetry along both axes, indicating an equal probability of locating the quark in either direction around the center. Interestingly, the spatial profile of the distribution resembles that of atomic orbitals, where the probability of finding an electron is highest in certain regions compared to others.

hep-ph↗
arXiv2025

RGUP Corrections to Scalar and Fermionic Fields

We investigate the Relativistic Generalized Uncertainty Principle (RGUP) effects on scalar and fermionic fields using the Stetsko-Tkachuk approximation. Modified equations of motion, Hamiltonians, and stress-energy tensors are derived in Minkowski spacetime, incorporating quantum gravitational corrections that ensure a minimal observable length and revert to standard dynamics when corrections are absent. For fermionic fields in curved spacetime, spin connections maintain gravitational consistency. This framework, applicable to high-energy physics, black hole thermodynamics, and cosmology, integrates quantum gravity into relativistic field theories.

gr-qc↗
arXiv2025

Quantum Information Measures in Quartic and Symmetric Potentials using perturbative approach

We analyze the Shannon and Fisher information measures for systems subjected to quartic and symmetric potential wells. The wave functions are obtained by solving the time-independent Schrödinger equation, using aspects of perturbation theory. We examine how the information for various quantum states evolves with changes in the width of the potential well. For both potentials, the Shannon entropy decreases in position space and increases in momentum space as the width increases, maintaining a constant sum of entropies, consistent with Heisenberg's uncertainty principle. The Fisher information measure shows different behaviors for the two potentials: it remains nearly constant for the quartic potential. For the symmetric well potential, the Fisher information decreases in position space and increases in momentum space as localization in position space increases, also consistent with the analogue of Heisenberg's uncertainty principle. Additionally, the Bialynicki-Birula-Mycielski inequality is evaluated across various cases and is confirmed to hold in each instance.

quant-ph↗
arXiv2024

Phase space distributions in information theory

We use phase space distributions specifically, the Wigner distribution (WD) and Husimi distribution (HD) to investigate certain information-theoretic measures as descriptors for a given system. We extensively investigate and analyze Shannon, Wehrl and Renyi entropies, its divergences, mutual information and other correlation measures within the context of these phase space distributions. The analysis is illustrated with an anharmonic oscillator and is studied with respect to perturbation parameter ($λ$) and states ($n$). The entropies associated with the Wigner distribution are observed to be lower than those of the Husimi distribution, which aligns with the findings regarding the marginals. Moreover, the real components of the entropies associated with the Wigner distribution tend to approach the entropic uncertainty bound more closely compared to those of the corresponding Husimi distribution. Moreover, we quantify the precise amount of information lost when opting for the Husimi distribution over the Wigner distribution for characterizing the specified system. Since it is not always positive definite, the entropies cannot always be defined.

quant-ph↗
arXiv2024

Gluon Generalized TMDs and Wigner Distributions in boost invariant longitudinal space

We present the gluon generalized TMDs for non-zero skewness and Wigner distributions in the boost invariant longitudinal space. The boost-invariant longitudinal space is defined as $σ=\frac{1}{2}b^-Δ^+$ and is conjugate to the skewness variable $ξ$. We use the dressed quark model, where a high-energetic quark is dressed by a gluon. This two-particle system has the advantage of addressing both the gluon and the quark sectors. The different contributions in Wigner distributions coming from different polarization of gluon and the dressed quark system are investigated. The Wigner distributions are obtained by taking the Fourier transformation of generalized TMDs, which we derive for the first time for non-zero skewness in dressed quark model.

hep-ph↗
arXiv2023

Wigner distribution of Sine Gordon and Kink solitons

Wigner distributions play a significant role in formulating the phase space analogue of quantum mechanics. The Schrodinger wave-functional for solitons is needed to derive it for solitons. The Wigner distribution derived can further be used for calculating the charge distributions, current densities and wave function amplitude in position or momentum space. It can be also used to calculate the upper bound of the quantum speed limit time. We derive and analyze the Wigner distributions for Kink and Sine-Gordon solitons by evaluating the Schrodinger wave-functional for both solitons. The charge, current density, and quantum speed limit for solitons are also discussed which we obtain from the derived analytical expression of Wigner distributions.

quant-ph↗
arXiv2022

Quark generalized TMDs at skewness and Wigner Distribution in boost invariant longitudinal space

The boost-invariant longitudinal space, defined by the parameter $σ=\frac{1}{2}b^-P^+$ can be studied from the Fourier transformation of distributions over the conjugate variable skewness $ξ$. We investigate quark Wigner distributions in the $σ$ space in dressed quark model and found diffraction patterns that are analogous to the single slit experiment of light in optics. The width of the central maxima varies with energy transfer to the system and essentially $ξ$ behaves like a slit-width. Qualitatively similar diffraction pattern is reported recently in other models. In this model, we compute all the leading twist GTMDs with non-zero skewness for quarks which provides Wigner distributions under Fourier transformation.

hep-ph↗
arXiv2018

Exclusive double quarkonium production and generalized TMDs of gluons

Being the "mother distributions" of all types of two-parton correlation functions, generalized transverse momentum dependent parton distributions (GTMDs) have attracted a lot of attention over the last years. We argue that exclusive double production of pseudoscalar quarkonia ($η_c$ or $η_b$) in nucleon-nucleon collisions gives access to GTMDs of gluons.

hep-ph↗
arXiv2014

Wigner Functions and Quark Orbital Angular Momentum

Wigner distributions contain combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs). We report on a recent model calculation of the Wigner distributions for the quark and their relation to the orbital angular momentum.

hep-ph↗
arXiv2014

Quark Wigner Distributions and Orbital Angular Momentum in Light-front Dressed Quark Model

We calculate the Wigner functions for a quark target dressed with a gluon. These give a combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs). We calculate and compare the different definitions of quark orbital angular momentum in this model. We compare our results with other model calculations.

hep-ph↗
arXiv2013

Generalized Parton Distributions of the Photon with Helicity Flip

We present a calculation of the generalized parton distributions (GPDs) of the photon when the helicity of the initial photon is different from the final photon. We calculate the GPDs using overlaps of photon light-front wave functions (LFWFs) at leading order in electromagnetic coupling $α$ and zeroth order in the strong coupling $α_s$, when the momentum transfer is purely in the transverse direction. These involve a contribution of orbital angular momentum of two units in the LFWFs. We express these GPDs in the impact parameter space.

hep-ph↗