arXiv subjects

Anwesha Chakraborty

Publications and source records attributed to Anwesha Chakraborty.

12 recordsLinked to original sources

arXiv2026

Probing Spacetime Topology and Superposition with Accelerated Detectors

We study entanglement harvested by Unruh DeWitt detectors following Rindler trajectories in compactified and superposed Minkowski spacetime. We consider different directions of acceleration (both parallel and antiparallel), separation between detectors and direction of spatial compactification mutually perpendicular to each other. Using the standard entanglement harvesting protocol, we analyze how these features influence the extracted correlations. When detector separation is perpendicular to the direction of acceleration, the harvested entanglement is uniformly suppressed due to increased spacelike separation. Compactification enhances field correlations leading to an increased concurrence and an extended harvesting range at higher accelerations. Additionally, we show that spacetime superposition introduces interference effects that further enlarge the entanglement harvesting region in parameter space, particularly in the high acceleration regime. We also find that the effect of antiparallel acceleration yielding significantly higher entanglement than parallel acceleration prevails in compactified and superposed spacetime.

gr-qc↗

arXiv2025

Random matrix prediction of average entanglement entropy in non-Abelian symmetry sectors

We study the average bipartite entanglement entropy of Haar-random pure states in quantum many-body systems with global $\mathrm{SU}(2)$ symmetry, constrained to fixed total spin $J$ and magnetization $J_z = 0$. Focusing on spin-$\tfrac12$ lattices and subsystem fractions $f < \frac{1}{2}$, we derive a asymptotic expression for the average entanglement entropy up to constant order in the system volume $V$. In addition to the expected leading volume law term, we prove the existence of a $\frac{1}{2}\log V$ finite-size correction resulting from the scaling of the Clebsch-Gordon coefficients and compute explicitly the $O(1)$ contribution reflecting angular-momentum coupling within magnetization blocks. Our analysis uses features of random matrix ensembles and provides a fully analytical treatment for arbitrary spin densities, thereby extending Page type results to non-Abelian sectors and clarifying how $\mathrm{SU}(2)$ symmetry shapes average entanglement.

quant-ph↗

arXiv2025

Electrostatically Controlled Pyrophototronic Effect Enabled Accident Alert System using a Strain-Polarized WS2 Phototransistor

Event-based dynamic light detection, specifically in low illumination power environments, is a critical requirement in autonomous vehicles. This work reports low optical power photodetection through the dynamic pyrophototronic effect in an ultra-thin 2D WS2 phototransistor. A four-stage pyrophototronic photoresponse has been realized through biaxial strain-polarization of the non-centrosymmetric (5-layer) WS2 channel using a sub-wavelength, nanopatterned hBN gate dielectric. Presence of strain in WS2 has been verified through extensive spectroscopic characterization and that of strain-induced charge polarization through density functional theory calculations as well as piezo force microscopy. The pyrophototronic effect boosts dynamic photoresponsivity (0.7 A/W) and detectivity (1.2x10^(15) Jones cm^(-1)) by up to 8x and enhances the photodetection speed by 3x over the non-patterned (unstrained) phototransistor, demonstrating a path to ameliorating the responsivity-speed trade-off in 2D photodetectors. Analysis of gate voltage, wavelength, and optical power dependence of the pyrophototronic current through measurements and band physics highlights its prominence under low channel population of electrostatically- or optically-induced free carriers. Gate tunability of the pyrophototronic current has been leveraged to design an optical spike-triggered dynamic accident alert system with speed-specific control for self-driving applications under low light conditions.

physics.app-ph↗

arXiv2024

Entanglement harvesting in quantum superposed spacetime

We investigate the phenomenon of entanglement harvesting for a spacetime in quantum superposition, using two Unruh-DeWitt detectors interacting with a quantum scalar field where the spacetime background is modeled as a superposition of two quotient Minkowski spaces which are not related by diffeomorphisms. Our results demonstrate that the superposed nature of spacetime induces interference effects that can significantly enhance entanglement for both twisted and untwisted field. We compute the concurrence, which quantifies the harvested entanglement, as function of the energy gap of detectors and their separation. We find that it reaches its maximum when we condition the final spacetime superposition state to match the initial spacetime state. Notably, for the twisted field, the parameter region without entanglement exhibits a significant deviation from that observed in classical Minkowski space or a single quotient Minkowski space.

gr-qc↗

arXiv2024

Fate of $κ$-Minkowski space-time in non-relativistic (Galilean) and ultra-relativistic (Carrollian) regimes

Here, we present an algebraic and kinematical analysis of non-commutative $κ$-Minkowski spaces within Galilean (non-relativistic) and Carrollian (ultra-relativistic) regimes. Utilizing the theory of Wigner-Inönu contractions, we begin with a brief review of how one can apply these contractions to the well-known Poincaré algebra, yielding the corresponding Galilean (both massive and mass-less) and Carrollian algebras as $c \to \infty$ and $c\to 0$, respectively. Subsequently, we methodically apply these contractions to non-commutative $κ$-deformed spaces, revealing compelling insights into the interplay among the non-commutative parameters $a^μ$ (with $|a^ν|$ being of the order of Planck length scale) and the speed of light $c$ as it approaches both infinity and zero. Our exploration predicts a sort of "branching" of the non-commutative parameters $a^μ$, leading to the emergence of a novel length scale and time scale in either limit. Furthermore, our investigation extends to the examination of curved momentum spaces and their geodesic distances in appropriate subspaces of the $κ$-deformed Newtonian and Carrollian space-times. We finally delve into the study of their deformed dispersion relations, arising from these deformed geodesic distances, providing a comprehensive understanding of the nature of these space-times.

hep-th↗

arXiv2023

Shift symmetries and duality web in gauge theories

Using a generalised Noether prescription we are able to extract all the currents and their conservation laws in space dependent shift symmetric theories. Various identities among the currents in the matter sector are found that form the basis for revealing a dual picture when the full interacting theory is considered by coupling to gauge fields. The coupling is achieved in terms of vector fields by adhering to a modified minimal prescription which is also supported by an iterative Noether scheme. Further, this scheme shows that couplings can also be introduced using higher rank tensor gauge fields that have appeared in recent discussions on fractons. We reveal a connection among these descriptions (using vector or tensor fields) through certain duality maps that relate the various fields (gauge, electric and magnetic) in the two cases. A correspondence is established among the Gauss' law, Faraday's law and Ampere's law. Explicit calculations are provided for linear and quadratic shift symmetric lagrangians.

hep-th↗

arXiv2023

Symmetries of $κ$ Minkowski space-time: A possibility of exotic momentum space geometry?

The quest for a quantum gravity phenomenology has inspired a quantum notion of space-time, which motivates us to study the fate of the relativistic symmetries of a particular model of quantum space-time, as well as its intimate connection with the plausible emergent curved "physical momentum space". We here focus on the problem of Poincare symmetry of $κ$-Minkowski type non-commutative (quantum) space-time, where the Poincare algebra, on its own, remains undeformed, but in order to retain the structure of the space-time non-commutative (NC) algebra, action of the algebra generators on the operator-valued space-time manifold must be enveloping algebra valued that lives in entire phase space i.e. the cotangent bundle on the space-time manifold (at classical level). Further, we constructed a model for a spin-less relativistic massive particle enjoying the deformed Poincare symmetry, using the first order form of geometric Lagrangian, that satisfies a new deformed dispersion relation and explored a feasible regime of a future Quantum Gravity theory in which the momentum space becomes curved. In this scenario there is only a mass scale (Planck mass $m_{p}$), but no length scale. Finally, we relate the deformed mass shell to the geodesic distance in this curved momentum space, where the mass of the particle gets renormalized as a result of noncommutativity. We show, that under some circumstances, the Planck mass provides an upper bound for the observed renormalized mass.

hep-th↗

arXiv2023

Emergent geometric phase in time-dependent noncommutative quantum system

Any effort to localise an event in the vicinity of the Planck length scale, only where the quantum gravitational effects are predicted to be observed, will invariably result in gravitational collapse. One must postulate noncommutative (NC) algebra between space-time coordinates, which are now elevated to the status of operators, in order to prevent such a situation from occurring. On the other hand, a consistent formulation of Quantum mechanics itself, with time being an operator is a challenging and longstanding problem. Here we have given a systematic way to formulate non-relativistic quantum mechanics on 1+1 dimensional NC space-time (Moyal type noncommutativity) in a user-friendly way, which mandates the formulation of an equivalent commutative theory. Although the effect of noncommutativity of space-time should presumably become significant at a very high energy scale, it is intriguing to speculate that there should be some relics of the effects of quantum space-time even in a low-energy regime. With this motivation in mind, we undertake the study of a time-dependent system, namely a forced harmonic oscillator in NC space-time and have shown the emergence of a geometric phase, which vanishes if the NC parameter is put to zero, proving the fact that, the occurrence of geometric phase is totally dependent on the non-commutativity of space-time.

hep-th↗

arXiv2022

Our Trysts with `Bal' and Noncommutative Geometry

This contributory article begins with our fond and sincere reminiscences about our beloved Prof. A.P. Balachandran. In the main part, we discuss our recent formulation of quantum mechanics on (1+1)D noncommutative space-time using Hilbert-Schmidt operators. As an application, we demonstrate how geometrical phase in a system of time-dependent forced harmonic oscillator living in the Moyal space-time can emerge.

hep-th↗

arXiv2022

Spectral triple with real structure on fuzzy sphere

Here we have illustrated the construction of a real structure on fuzzy sphere $S^2_*$ in its spin-1/2 representation. Considering the SU(2) covariant Dirac and chirality operator on $S^2_*$ given by Watamura et. al. in [6], we have shown that the real structure is consistent with other spectral data for KO dimension-4 fulfilling the zero order condition, where we find it necessary to enlarge the symmetry group from SO(3) to the full orthogonal group O(3). However the first order condition is violated thus paving the way to construct a toy model for an SU(2) gauge theory to capture some features of physics beyond standard model following Connes et.al. [9].

hep-th↗

arXiv2022

Fingerprints of the quantum space-time in time-dependent quantum mechanics: An emergent geometric phase

We show the emergence of Berry phase in a forced harmonic oscillator system placed in the quantum space-time of Moyal type, where the time 't' is also an operator. An effective commutative description of the system gives a time dependent generalised harmonic oscillator system with perturbation linear in position and momentum. The system is then diagonalised to get a generalised harmonic oscillator and then its adiabatic evolution over time-period $\mathcal{T}$ is studied in Heisenberg picture to compute the expression of geometric phase-shift.

hep-th↗

arXiv2019

Spectral Distance on Lorentzian Moyal Plane

We present here a completely operatorial approach, using Hilbert-Schmidt operators, to compute spectral distances between time-like separated "events ", associated with the pure states of the algebra describing the Lorentzian Moyal plane, using the axiomatic framework given by [13, 14]. The result shows no deformations of non-commutative origin, as in the Euclidean case.

hep-th↗