arXiv subjects

Balbeer Singh

Publications and source records attributed to Balbeer Singh.

At least 19 recordsLinked to original sources

arXiv2026

Probing jet medium interaction with generalized projected energy correlators

We study medium modifications to generalized projected energy correlators, referred to as $\nu$-correlators, measured on jets in heavy-ion collisions. While the vacuum distributions of these correlators exhibit a characteristic $1/\nu$ enhancement, we show that in a dense medium this behavior is regulated within both the BDMPS-Z and semi-classical approximations as $\nu \to 0$. As a result, contributions from medium-induced emissions become parametrically suppressed relative to the vacuum baseline. We observe a similar trend in the simulated events generated with JEWEL. We find that while the large angle enhancement is qualitatively similar across different values of $\nu$, the small angle distribution changes drastically between $\nu<1$ and $\nu>1$. This indicates that small angle modifications, primarily driven by jet energy loss, are imprinted differently across $\nu$-correlators. In particular, for $\nu<1$ the small angle enhancement is less prominent which suggests that these correlators may provide improved sensitivity to medium modifications in the large angle region.

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arXiv2026

Quantum Simulation of Markovian and Non-Markovian Open Quantum Dynamics in Heavy-Ion Collisions

We present a quantum computing framework for simulating open-quantum-system approaches based on Markovian and non-Markovian dynamics, which is relevant to heavy-ion collisions. To simulate the non-Markovian evolution on quantum computers, we introduce an auxiliary two-level pseudomode that carries the memory forward and couples to both the subsystem and the residual Markovian bath. We explicitly show that tracing out the pseudomode reproduces the non-Markovian evolution with the exact memory kernel. Moreover, in the relevant time scale hierarchy, the quantum circuit construction of the pseudomode smoothly converges to the Markovian limit. For a given bath memory kernel, our results demonstrate the feasibility of quantum simulations of both Markovian and non-Markovian dynamics, establishing a framework for future studies of hard probes such as jets, heavy quarks, and quarkonia in heavy-ion collisions.

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arXiv2025

Study of chaos and scrambling in hairy AdS Soliton

In this work, we perform a comprehensive study of the classical and quantum chaos in a candidate five-dimensional hairy AdS soliton. It is a horizonless geometry holographically dual to a confining field theory with finite scalar potential. We probe classical chaos by using particle geodesics and closed classical string. While the former shows no signature of chaos, the latter provides chaotic dynamics of the string using the Lyapunov exponent and the evolution of the Poincaré section. We perform an independent spectral analysis using the tools of the random matrix theory (RMT), namely the level space distributions and the Dyson-Mehta(DM) $Δ_{3}$-statistics. We observe a clear transition from the low energy Wigner-Gaussian Orthogonal Ensemble (GOE) distribution to the high energy Poisson distribution. This signifies a flow from quantum chaos in the infrared to integrability in the ultraviolet. We quantitatively characterize the inherent quantum scrambling in the dual theory by computing the butterfly velocity, the rate of spatial spread of the information scrambling, inside the bulk. We undergo two independent holographic methods -- entanglement wedge reconstruction and derivation of out-of-time-ordered correlators via shockwave analysis. In these methods, we heuristically consider the region near the soliton tip to provide the infrared physics of scrambling in analogy with the near-horizon region of a black hole. We find that the hair parameter controls various scrambling properties. Finally, we make comments on the interplay between insulator/superconductor phase transition in hairy soliton geometry and dynamical transition from integrability to chaos as both of these are affected by the presence of the hair parameter.

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arXiv2025

Holographic Extended Thermodynamics of deformed AdS-Schwarzschild black hole

We investigate the thermodynamics and phase structure of the deformed AdS-Schwarzschild black hole, generated via the gravitational decoupling (GD) method. In the bulk canonical ensemble, our results exhibit a van der Waals-type first-order phase transition in addition to the Hawking-Page transition, in the suitable parameter regime. Further, we compute the critical exponents characterising the bulk transition, confirming their consistency with mean-field theory predictions. Exploiting the exact holographic dictionary between extended black hole thermodynamics and the dual conformal field theory (CFT), we extend this analysis to the boundary and uncover a rich array of phase transitions and critical phenomena across three distinct thermodynamic ensembles. In particular, in the fixed $(\mathcal{V},C)$ ensemble, the dual CFT exhibits a Hawking-Page-type transition. However, in the fixed $(p,C)$ ensemble, the deformation parameter leads to a distinct thermodynamic behaviour in which multiple branches become unstable, leaving a single thermodynamically stable phase, thus marking a clear departure from the standard van der Waals scenario. Throughout, we emphasise the pivotal influence of the GD deformation parameter on the thermodynamic behaviour, and we elucidate its role in the confinement-deconfinement transitions characteristic of the deformed AdS-Schwarzschild geometry.

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arXiv2025

Medium modifications to jet angularities using SCET with Glauber gluons

We perform a comprehensive analysis of medium modifications on ungroomed jet angularities, $τ_a$, within the framework of Soft-Collinear Effective Theory with Glauber gluons (SCET$_{\rm G}$). Angularities are a one-parameter family of jet substructure observables with angularity exponent $a < 2$ for infrared safety. Variation of the angularity exponent allows one to modify the relative weighting of the collinear-to-soft radiations in the jet, thereby giving access to different moments of the jet transverse momentum spectrum. In this article, we focus on $a<1$ and provide detailed results for $a=-1, 0$, and $0.5$. Within SCET$_{\rm G}$, the interactions between jet and medium constituents are mediated by off-shell Glauber gluons generated from the color sources in the medium. While medium modifications are incorporated into the jet function via the use of medium-induced splitting functions, the soft function remains unmodified for $a<1$. For all values of $a$, we find that compared to jets in vacuum, the medium-modified distributions are shifted towards smaller values of jet angularity and have a steeper fall. This redistribution of the ungroomed angularity spectrum is more apparent for a jet with a larger cone size and for higher values of $a$. We also present results for the medium sensitivity towards $p_T$ of the jet and for a jet initiated in a less central event ($10-30\%$ centrality). Finally, we provide the ratios of nucleus-nucleus and proton-proton differential angularity distributions for different angularity exponents, and for two values of the jet radius parameter.

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arXiv2025

Lattice study of correlators for quarkonium decay

While there has been a lot of progress in developing a formalism for the study of quarkonia in QGP, a nonperturbative study is still difficult. For bottomonia, where the system size is much less than the inverse temperature, the interaction of the system with the medium can be approximated by a dipole interaction with the color electric field. The decay of the quarkonia can be connected to a correlation function of the color electric field. We present preliminary results from a lattice study of the relevant color electric field correlator. The structure of the correlator, and its difference from the corresponding correlator studied for heavy quark diffusion, is discussed.

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arXiv2025

Investigating (Non)-Integrability and Pulsating String in D3-Brane Background

This work explores the (non)-integrability and chaotic dynamics of classical strings in the background of a D3-brane with a non-commutative parameter, within the framework of the AdS/CFT correspondence. Using the Polyakov action, we derive the equations of motion and constraints for pulsating strings and analyze their stability through perturbation theory. In the high-energy limit, the first-order perturbed equation simplifies to the Pöschl-Teller equation, solvable via associated Legendre or hypergeometric functions, while numerical methods are employed for generic energy values. We demonstrate that the non-commutative parameter enhances chaotic behavior, as evidenced by the Largest Lyapunov Exponent (LLE). Furthermore, we investigate the integrability of geodesic motion and identify two distinct string modes: captured at and escape to infinity. Finally, we study pulsating strings in the deformed $(AdS_{3} \times S^{2})_{\varkappa}$ background, deriving dispersion relations for both short and long strings.

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arXiv2025

Towards factorization of jet observables in dense media : An EFT approach

Jets are extended multipartonic systems and serve as a powerful tool for investigating the dynamics of emergent phenomena driven by many body QCD interactions. In heavy ion collisions, starting from their production during the perturbative hard scattering event in the initial stages of the collision to non-perturbative hadronization they interact with the various stages of quark-gluon plasma and retain imprints of fundamental properties of the medium. In these collisions, the jet production cross-section can be factorized using open quantum system framework along with effective field theory into various functions, each capturing a specific dynamics and depending on a single characteristic scale. In this review article, we discuss recent theoretical developments on factorization for jets in heavy-ion collisions with a specific example of jet substructure observable as energy-energy correlator and its generalization to projected $ν$-point energy correlators.

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arXiv2025

Circular orbits and chaos bound in slow-rotating curved acoustic black holes

Acoustic black holes, analogs of gravitational black holes created in fluid systems, have recently been embedded within Schwarzschild spacetime using the Gross-Pitaevskii theory, leading to configurations with both event and acoustic horizons. This study examines the motion of vortices, modeled as unit-mass relativistic test particles, around a slow-rotating curved acoustic black hole. We analyse the stability of circular orbits, identifying the innermost stable circular orbit (ISCO), and investigate the chaotic dynamics of vortices perturbed from unstable circular orbits near the acoustic horizon. Using the Lyapunov exponent to quantify this chaos, we assess whether it satisfies the Maldacena-Shenker-Stanford bound $(λ\le 2 πT_H)$, a limit established for gravitational black holes in general relativity. Our results show that, in non-extremal cases $(ξ> 4)$, the Lyapunov exponent respects the bound near the horizon, while in extremal cases $(ξ= 4)$, it is violated due to vanishing surface gravity. These findings highlight similarities between acoustic and gravitational black holes, advancing the analogy in the context of chaos and orbital dynamics.

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arXiv2025

Open quantum system approach to inclusive jet production in heavy-ion collisions

We derive a factorization formula for inclusive jet production in heavy-ion collisions using the tools of Effective Field Theory (EFT). We show how physics at widely separated scales in this process can be systematically separated by matching to EFTs at successively lower virtualities. Owing to a strong scale separation, we recover a vacuum-like DGLAP evolution above the jet scale, while the additional low-energy scales induced by the medium effectively probe the internal structure of the jet. As a result, the cross section can be written as a series with an increasing number of subjets characterized by perturbative matching coefficients each of which is convolved with a {\it distinct} function. These functions encode broadening, medium-induced radiations as well as quantum interference such as the Landau-Pomeranchuk-Migdal effect and color coherence dynamics to all orders in perturbation theory. As a first application of this EFT framework, we investigate the case of an unresolved jet and show how the cross section can be factorized and fully separate the jet dynamics from the universal physics of the medium. To compare to the existing literature, we explicitly compute the medium jet function at next-to-leading order in the coupling and leading order in medium opacity.

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arXiv2025

Exploiting $\nu$-dependence of projected energy correlators in HICs

We extend the recently derived factorization formula for energy-energy correlators to study the analytic structure of general $\nu$-point projected energy correlators in heavy ion collisions. The $\nu$-point projected energy correlators (or, $\nu$-correlators) are an analytically continued family of the integer $N$-point projected energy correlators, which probe correlations between $N$ final-state particles. By tracking the largest separation ($\chi$) between the $N$ particles, in vacuum, their structure is closely related to the DGLAP splitting functions and exhibits a classical scaling behavior $\sim 1/\chi$ which is modified by resummation through the anomalous dimensions. We show that, in a thermal medium, the $\nu$-correlators display non-trivial angular scaling already at the leading order in perturbation theory. We find that for non-integer values, particularly $\nu<1$, medium-induced jet function is enhanced compared to $\nu>1$. This is particularly manifested in the ratios of $\nu$-correlators with respect to the two-point energy correlator which encode an intrinsic angular information for $\nu<1$ when compared to large $\nu$ values. Moreover, for small-$\nu$ values, the $\nu$-correlators appear to saturate at $\nu=0.01$. We further confirm our leading-order numerical computations against simulated events from JEWEL for the parton level production cross-section. Finally, we qualitatively discuss the effect of BFKL resummation for various values of $\nu$.

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arXiv2025

Chaos Bound and its violation in Black p-brane

In this work, we have extensively investigated the dynamics of circular geodesic (chargeless massive particle) followed by the investigation of the pulsating classical string in the p-brane background. This study is a continuation of our previous work JHEP10(2023)189, in which we numerically identified the presence of chaos for a classical string hovering near generic p-branes ($p < 7$). Here, for a particle probe, we have found evidence of chaos in the vicinity of the horizon. Furthermore, we observed a violation of the well-known MSS bound in specific extremal p-branes; however, no such violation is seen in the non-extremal cases. Similar observations were made for the classical string, where the violation of the bound is significant near the horizon. Thus, our semi-analytical arguments demonstrate that chaotic dynamics in black p-branes exhibit the (generalized) universal bound with notable violations, regardless of whether a particle or classical string is used as a probe.

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arXiv2024

Towards factorization with emergent scales for jets in dense media

Employing the recently developed open quantum system Effective Field Theory framework, we investigate jet production and evolution in a dense nuclear medium in electron-ion/heavy-ion collisions. We confirm that the frequent monitoring of the jet by the medium leads to the emergence of a perturbative transverse momentum scale, often referred to as the saturation scale that necessitates further factorization to completely isolate the non-perturbative physics of the medium. A part of this goal is achieved in this paper by providing an operator definition for the broadening probability of a gluon in the medium within the Markovian approximations. We show that this distribution is (semi)universal; it depends on the angular measurement on the jet and probes both the large and small $x$ dynamics of the medium. We further elucidate all other contributions to non-perturbative physics suggesting that the parameterization of non-perturbative physics is more complex than previously assumed and outline steps required for a complete factorization of the jet production cross section.

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arXiv2024

Factorization for jet production in heavy-ion collisions

We develop an Effective Field Theory approach for jet observables in heavy-ion collisions, where the jet is treated as an open quantum system interacting with a hot and dense QCD medium. Within this framework, we derive a novel factorization formula for inclusive jet production, expressed as a series expansion with an increasing number of radiating subjet functions that encode forward scattering with the Quark-Gluon Plasma, convolved with perturbative matching coefficients. This work provides a systematic framework for computing jet observables at higher order and understanding their non-perturbative aspects, paving the way for future applications in heavy-ion phenomenology.

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arXiv2024

Factorization for energy-energy correlator in heavy ion collision

We present a factorization formula for the energy-energy correlator in the collinear limit for the case of heavy ion collisions. Employing Soft Collinear Effective Theory, we provide a complete framework for jet production and evolution by separating the jet dynamics from the universal medium physics to all orders in perturbation theory in terms of gauge invariant operators. The EFT allows us to precisely define the domain of validity of different approximations and to systematically go beyond leading order results in the literature through radiative corrections. For this observable, we show where the leading order GLV and BDMPS-Z results are valid and infer that higher order radiative corrections lead to both DGLAP and BFKL evolutions. We further show the impact of BFKL resummation on the medium induced jet function for two point energy correlator. Crucially, the EFT approach enables us to evaluate the universality of the non-perturbative physics which is the key to predictive power in a strongly coupled medium.

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arXiv2023

$Z$ polarization at an $e^+e^-$ collider and properties of decay-lepton angular asymmetries

$Z$ production at an $e^+e^-$ collider, associated with production of other particles, can be an accurate source of information of details of electroweak interactions, including possible interactions beyond the standard model. We discuss from a general physical point of view the properties of the density matrix as well as lepton angular asymmetries. While most considerations will be applicable to processes of $Z$ production associated with any other particle or particles, for some discussions, we specialize to a $HZ$ final state. While many of the results can be found in earlier literature, especially for the process $e^+e^- \to HZ$, we give details of the reasoning, which are not always found. We discuss the properties of the spin density matrix under C, P and T transformations, and combinations thereof, as also the predictions of these for the corresponding leptonic asymmetries. The specific transformations P, CP, T and CPT are of special importance and we discuss the consequences of these symmetries or their absence for the leptonic asymmetries. A specific issue which has been given attention to is the role of beam polarization, and how one can infer on general grounds which asymmetries get enhanced by the use of beam polarization. Similarly, we also discuss which asymmetries would be sensitive to the measurement of tau polarization in $Z$ decay in to $τ^+τ^-$.

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arXiv2023

Circular string in a Black p-brane leading to chaos

We consider a pulsating string near a non-extremal black p-brane (p=5 and p=6) and investigate the chaos in the corresponding string dynamics by examining the Fast Lyapunov indicator(FLI) and Poincare section. In our system, the energy and the charge play the role of control parameters. For generic values of these parameters, the numerical results show that the dynamics primarily fall into three modes: capture, escape to infinity, and quasiperiodic depending on the initial location (near to or far away from the black brane horizon) of the string. Finally, probing for different values of the winding number (n) the dynamics turns out to be sensitive to n. In particular, we observe the point particle (n=0) scenario to be integrable whereas at higher n the dynamics seems to be chaotic.

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arXiv2023

Polarized $Z$ cross sections in Higgsstrahlung for the determination of anomalous $ZZH$ couplings

The production of a Higgs boson in association with a $Z$ at an electron-positron collider is one of the cleanest methods for the measurement of the couplings of the Higgs boson. In view of the large production cross section at energies a little above the threshold, it seems feasible to make a more detailed study of the process by measuring the cross sections for polarized $Z$ in order to measure possible anomalous $ZZH$ couplings. We show that certain combinations of cross sections in $e^+e^- \to ZH$ with different $Z$ polarizations help to enhance or isolate the effect of one of the two kinds of anomalous $ZZH$ couplings possible on general grounds of CP and Lorentz invariance. These combinations can be useful to get information on the $ZZH$ coupling in the specific contexts of an effective field theory, two-Higgs-doublet models, and composite Higgs models, in a relatively model-independent fashion. We find in particular that the longitudinal helicity fraction of the $Z$ is expected to be insensitive to anomalous couplings, and would be close to its value in the standard model in the scenarios we consider. We also discuss the sensitivity of the proposed measurements to the anomalous couplings, including longitudinal beam polarizations, which suppress backgrounds, and can improve the sensitivity if appropriately chosen.

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