arXiv subjects

Partha Nandi

Publications and source records attributed to Partha Nandi.

At least 19 recordsLinked to original sources

arXiv2026

From Analytic Structure to Quantum Complexity: Walsh-Pauli Representations of Continuum Operators

How does continuum operator structure appear in a finite qubit register? We address this question for analytic functions of diagonal operators represented in a binary basis, focusing on the Jordan--Lee--Preskill (JLP) momentum operator, by developing an operator-level generating-function framework for their Walsh-Pauli spectra. The construction determines the spectrum analytically and reveals exact support and parity selection rules, together with a nontrivial intra-shell hierarchy induced by the binary encoding. This provides a systematic characterization of Walsh compressibility and its relation to Pauli locality. As a controlled application, we consider generalized uncertainty-principle (GUP) kinematics as a tunable nonlinear odd deformation of momentum, showing how higher-order momentum terms redistribute spectral weight into progressively higher Pauli-weight sectors

quant-ph↗

arXiv2026

Revealing the Quantum Signature of Gravity via Gravitational Waves

Can propagating gravitational waves serve as operational probes of the quantum nature of gravity? We address this question by developing a unified theoretical framework that combines spacetime geometry, quantum information, and gravitational-wave physics. Starting from the geodesic deviation equation in linearized General Relativity, we derive the effective detector Hamiltonian directly from spacetime geometry and construct the complete quantum dynamics for detector subsystems interacting with both classical and quantized propagating gravitational-wave fields. This unified formulation enables a direct comparison between classical and quantum descriptions of gravitational radiation within the same physical framework. We demonstrate that classical gravitational-wave backgrounds can induce mixedness in the detector state but cannot generate genuine quantum correlations between the detector subsystems. In contrast, quantized gravitational waves coherently mediate gravity-induced entanglement, quantum coherence, quantum memory, and nonclassical correlations, providing clear operational signatures of the quantum nature of propagating gravitational radiation. We further discuss how mesoscopic quantum mechanical oscillators offer a promising route towards experimentally probing these effects. Our results establish a geometric and quantum-information-based framework for exploring quantum gravity through propagating gravitational waves.

gr-qc↗

arXiv2026

Exploring Quantum Corners: How Curved Momentum Space Shapes BTZ Black Holes

Planck-scale signatures of quantum gravity may emerge semiclassically not only through modifications of spacetime geometry but also through the geometry of momentum space. In this work, we develop a $(2+1)$-dimensional framework in which a noncommutative algebra of spacetime localization operators reconstructs a locally anti-de Sitter momentum-space geometry in the classical limit. The resulting momentum-space curvature deforms the phase-space structure, modifies particle kinematics, and leads to a finite renormalization of the particle mass. Using an effective configuration-space action, we derive the corresponding stress-energy tensor that consistently sources the classical Einstein equations without modifying the gravitational dynamics. The resulting spacetime is a deformed BTZ black hole whose conserved mass, horizon radius, Hawking temperature, and Bekenstein-Hawking entropy acquire finite Planck-scale corrections. We further investigate Hawking radiation using the Hamilton-Jacobi tunneling formalism and show that the return time of an emitted massless particle receives two distinct contributions: a geometric correction induced by curved momentum space and a dynamical correction arising from Hawking backreaction. Remarkably, the null geodesic equations remain unchanged, indicating that the observable effects originate entirely from the deformation of the effective spacetime geometry rather than from modifications of particle trajectories. These results provide a concrete semiclassical mechanism through which quantum kinematics encoded in curved momentum space can generate observable gravitational phenomena without requiring a quantization of spacetime itself, thereby offering a phenomenological bridge between quantum geometry and black-hole physics.

gr-qc↗

arXiv2026

Spin-Induced Fractal Time-Crystal-Like Dynamics and Non-Markovian Memory in the Bateman Dual Oscillator

Can a closed quantum system generate time-crystal-like nonequilibrium behavior, self-similar scaling structures, and non-Markovian memory without external driving or coupling to a macroscopic environment? We address this question within the quantum Bateman oscillator formulated in a nonrelativistic (2 + 1)-dimensional phase-space noncommutative framework generated by spin-induced spatial deformation. The resulting doubled quantum dynamics is governed by a time-independent Hermitian Hamiltonian and exhibits an underlying SU(1, 1) structure with amplified and damped collective modes. We show that these modes satisfy an exact discrete scaling covariance, leading to self-similar temporal evolution without external driving. Upon tracing over one oscillator sector, the reduced dynamics becomes intrinsically non-Markovian and is governed by a history-dependent memory kernel. The same scaling structure admits a geometric representation in terms of logarithmic-spiral trajectories associated with the amplified and damped branches of the Bateman system. Because the mechanism relies on nonequilibrium reduced dynamics rather than equilibrium expectation values of local observables, it lies outside the assumptions underlying conventional no-go theorems for equilibrium time crystals. Our results identify spin as the common physical origin of the amplified and damped Bateman dynamics, self-similar scaling periodicity, logarithmic-spiral structures, and non-Markovian memory, also suggesting a natural extension of the mechanism to relativistic anyonic systems.

hep-th↗

arXiv2026

Is Exact Markovianity Fundamental Once Time Is Relational?

Markovian open quantum theory assumes evolution with respect to an external classical time parameter, yet no preferred notion of time exists fundamentally in relativistic physics. We resolve this tension by formulating relativistic open quantum dynamics relationally through finite-resolution quantum clocks. Using the Schwinger-Tomonaga formalism, we derive a covariant master equation directly on spacetime hypersurfaces and show that the resulting reduced dynamics is generically non-Markovian even for local interactions. Environmental correlations and clock fluctuations jointly generate the memory kernel, while the Gorini-Kossakowski-Lindblad-Sudarshan (GKLS) structure emerges only after relational coarse-graining, implying that exact Markovian evolution is effective rather than fundamental. In the sharp-clock limit, the formalism reduces to the Anastopoulos-Hu gravitational decoherence equation.

quant-ph↗

arXiv2026

Spin-Induced Non-Markovian Time-Crystal-Like Dynamics and Fractal Scaling in the Bateman Dual Oscillator

Can a closed quantum system generate persistent time-crystal-like dynamics without external driving? Within the Bateman dual oscillator framework, we show that the answer is affirmative. We consider a nonrelativistic (2+1)-dimensional system in which spin-induced spatial deformation generates an effective Bateman oscillator structure. After quantization, the system is governed by a time-independent Hermitian Hamiltonian describing coherent coupling between damped and amplified oscillator sectors while preserving the total energy of the global doubled system. Tracing over the amplified sector, we derive an effective non-Markovian reduced dynamics for the observable subsystem. The resulting memory effects sustain persistent oscillations of subsystem observables and generate emergent time-crystal-like temporal ordering without external periodic driving or equilibrium spontaneous symmetry breaking. Since the oscillatory behavior originates from nonequilibrium reduced subsystem dynamics rather than equilibrium expectation values of the full Hamiltonian, the mechanism lies outside the assumptions of conventional no-go theorems for equilibrium time crystals. The same dynamics further exhibits logarithmic-spiral trajectories and self-similar fractal scaling, revealing a direct connection between coherent dissipative dynamics, non-Markovian memory effects, and emergent temporal ordering in a globally unitary quantum system. In this specific sense, "watching the growth" of these self-similar structures corresponds to observing the gradual formation of time-crystal-like ordering.

quant-ph↗

arXiv2026

State-Selective Signatures of Quantum and Classical Gravitational Environments

A unified framework is developed for determining whether a gravitational-wave (GW) background behaves as a classical field or as a genuinely quantum environment. Unified here means that both descriptions originate from the same tidal coupling derived from geodesic deviation, which yields an identical quadratic interaction Hamiltonian for the detector; the only distinction lies in whether the GW degrees of freedom are modeled as classical phase-randomized coherent states or as quantized graviton modes. Within this common framework, the reduced dynamics of a quantum harmonic oscillator exhibit a sharp structural contrast: a quantized graviton bath preserves coherence within the lowest phonon-number manifold, forming a protected sector at leading order, whereas a classical stochastic GW field inevitably induces decoherence even inside this subspace. This difference provides an operational criterion for diagnosing the classical or quantum nature of gravitational waves using mesoscopic optomechanical systems. Our results establish decoherence structure - not merely its magnitude - as a sensitive probe of gravitational quantumness and delineate the experimental regimes under which such tests may become feasible.

gr-qc↗

arXiv2025

A novel quantum memory effect and thermal modulation in graviton-mediated entanglement

A central challenge in probing the quantum nature of gravity is to distinguish effects that are genuinely quantum from those that can be explained classically. In this work, we study how quantized gravitational waves interact with thermal quantum systems, modeled as harmonic oscillators. We show that, unlike classical waves, quantized gravitons generate entanglement and leave behind a persistent ``graviton-induced quantum memory'' even after the wave has passed. This effect is further shaped by the presence of thermal noise, which does not simply wash out quantum correlations but can in fact amplify them in distinctive ways. Our analysis reveals clear signatures - such as nonlinear thermal corrections and a prethermal time-crystal-like phase-that cannot arise from any classical treatment. These results identify experimentally relevant markers of gravitons and provide a framework for exploring how finite-temperature environments may help uncover the quantum nature of gravity.

gr-qc↗

arXiv2025

Spinning into Quantum Geometry: Dirac and Wheeler-DeWitt Dynamics from Stochastic Helicity

Spin networks in loop quantum gravity provide a kinematical picture of quantum geometry but lack a natural mechanism for dynamical Dirac-type evolution, while the Wheeler--DeWitt equation typically enters only as an imposed constraint. We propose a stochastic framework in which each spin-network edge carries helicity-resolved amplitudes -- two-state internal labels that undergo Poisson-driven flips. The resulting coupled master equations, after analytic continuation and the introduction of a fundamental length scale, generate Dirac-type dynamics on discrete geometry. At long times, the same process relaxes to helicity-symmetric equilibrium states, which are shown to satisfy a Wheeler--DeWitt-type condition. In this way, both quantum evolution and the gravitational constraint emerge within a single probabilistic framework. Our approach thus provides a background-independent and stochastic route to quantum geometry, offering an alternative to canonical quantization and a fresh perspective on the problem of time.

gr-qc↗

arXiv2025

Quantum-Gravitational Backreaction in the BTZ Background from Curved Momentum Space

We explore how quantum properties of spacetime, specifically the curvature of momentum space, can backreact on classical gravity within a tractable semiclassical (2+1)-dimensional framework with a negative cosmological constant. Motivated by quantum-gravity scenarios, we investigate how Planck-scale modifications of particle kinematics influence both dynamics and gravitational solutions. Starting from a first-order action, we derive an effective configuration-space description and show that particle trajectories remain geodesic, preserving the weak equivalence principle despite the underlying deformation. Coupling this modified matter sector to Einstein gravity, we obtain a deformed BTZ black hole solution. Remarkably, the local geometric structure and thermodynamic relations retain their standard form, while all quantum-gravity effects are encoded in a nonlinear mapping between the microscopic mass parameter and the ADM mass. This induces a renormalization of the horizon radius and thermodynamic quantities without altering their functional dependence. As a concrete observable consequence, we compute corrections to the return time of massless probes traveling along null geodesics between the horizon and the AdS3 boundary. Our results demonstrate that Planck-scale kinematic effects can leave controlled and potentially measurable imprints on classical geometry, providing a clear and consistent bridge between quantum-gravity ideas and semiclassical observables.

gr-qc↗

arXiv2025

Stochastic Quantization of Electrodynamics and Linearized Gravity

We develop a unified stochastic framework in which a velocity- and helicity-reversing Poisson process gives rise to the Telegrapher's equation. Analytic continuation to the complex plane results in Dirac-like evolution equations for electromagnetic and linearized gravitational fields. A small but nonzero mass parameter is essential to enable helicity reversals. Yet, the correct massless wave equations are recovered as the physically relevant massless limit is approached smoothly, with the singular point excluded from the construction. Remarkably, probability does not enter as an external postulate as in the Born rule in standard quantum mechanics -- but is intrinsic to the stochastic process. This probabilistic structure becomes embedded in the wave fields through a natural rescaling by the Planck length.

gr-qc↗

arXiv2025

Quantum Geometric Phases as a New Window on Gravitational Waves

We investigate how low-frequency gravitational waves (LFGWs), originating from distant astrophysical or cosmological sources, can induce purely quantum geometric phases in mesoscopic optomechanical systems. These phases represent subtle imprints with no classical counterpart, going beyond standard dynamical or Berry-type contributions that admit Hannay-angle analogues. Such ultra-weak waves couple to the motion of a mechanical mirror and generate distinctive phase shifts in the system's quantum state that cannot arise in any classical description. To access this effect, we propose a Ramsey-type interferometric protocol in which the photon-number states of a quantized optical mode become entangled with the mirror's center-of-mass motion, enabling a direct readout of the LFGW-induced geometric phase. This framework establishes a distinctly quantum approach for probing low-frequency gravitational wave modes, offering an alternative to conventional detection strategies based on spacetime strain.

hep-th↗

arXiv2025

Can Non-Relativistic Strings Propagate Without Geometric Baggage?

We present a minimal and dynamically consistent formulation of non-relativistic bosonic string theory in a Newton-Cartan (NC) background. Starting from a reparametrization-invariant Nambu-Goto action, we develop the Hamiltonian framework and perform a complete Dirac constraint analysis. The resulting structure exhibits first-class constraints that generate worldsheet diffeomorphisms, confirming the internal gauge consistency of the model. Using an interpolating Lagrangian, we derive a Polyakov-type action that enables a direct comparison with symmetry-based constructions known as gauging the algebra (GTA) approaches, which promote non-relativistic symmetry algebras to local symmetries. In contrast to GTA formulations, which require additional background fields to achieve algebraic closure, our model derives all necessary geometric data dynamically from the string evolution itself. This establishes that standard Newton-Cartan geometry is sufficient to support consistent non-relativistic string dynamics. Our results provide a conceptually transparent and technically robust foundation for future studies of non-relativistic string theory in curved backgrounds.

hep-th↗

arXiv2025

Gravitationally induced entanglement at finite temperature: A memory-driven time-crystalline phase?

We study the impact of thermal effects on gravity-induced entanglement (GIE) in a system of quantum harmonic oscillators interacting with classical linearly polarized gravitational waves (GWs). Specifically, we model the endpoints of interferometer arms in LIGO-like detectors as two-dimensional oscillators. Following the thermofield dynamics (TFD) approach, our analysis reveals that while thermal effects alone do not generate entanglement between independent oscillator modes, they serve as a catalyst, modifying the dynamical imprint of GWs. Notably, we identify a mixing of Bose-Einstein and Maxwell-Boltzmann distributions driven by thermal influences, which affects the statistical behavior of the quantum subsystem. Furthermore, gravitational interactions induce a quantum memory effect, leading to emergent periodic behavior in the reduced subsystem. This suggests a novel gravitationally induced breaking of time-translation symmetry, reminiscent of a prethermal time crystal (PTC). Our findings indicate that such effects could provide new theoretical insights into classical gravitational wave interactions.

gr-qc↗

arXiv2025

Decoherence from quantum spacetime noise: An open-systems framework with application to neutrino oscillations

We present a general open-quantum-systems framework to model decoherence induced by stochastic Planck-scale fluctuations of spacetime, focusing on the kappa-Minkowski noncommutative geometry as a representative quantum-gravity scenario. Treating the deformation parameter as Gaussian white noise, we derive a Lindblad-type master equation applicable to arbitrary quantum systems and obtain a distinctive inverse-energy scaling of the decoherence rate, Gamma proportional to E^{-4}. As an illustrative example, we analyze a three-level system motivated by neutrino flavor oscillations and derive closed-form expressions for survival and transition probabilities with spacetime-induced damping. The E^{-4} scaling contrasts sharply with the positive power laws often invoked in quantum-gravity phenomenology and predicts negligible decoherence for high-energy neutrinos consistent with IceCube observations, while implying that the strongest effects arise in the extreme low-energy regime. In this context, the sub-eV-scale energies characteristic of the cosmic neutrino background provide a natural infrared benchmark for illustrating the enhanced sensitivity to quantum-spacetime fluctuations. Our results establish a unified formalism connecting quantum-information methods, open-system dynamics, and quantum-spacetime phenomenology, thereby offering a framework for exploring potential signatures of Planck-scale physics in future low-energy neutrino studies.

hep-th↗

arXiv2024

Phase Segregation Dynamics in Mixed-Halide Perovskites Revealed by Plunge-Freeze Cryogenic Electron Microscopy

Mixed-halide lead perovskites, with photoexcited charge-carrier properties suitable for high-efficiency photovoltaics, hold significant promise for high-efficiency tandem solar cells. However, phase segregation under illumination, where an iodide-rich phase forms carrier trap states, remains a barrier to applications. This study employs plunge-freeze cryogenic electron microscopy to visualize nanoscale phase segregation dynamics in CsPb(Br,I) films. By rapidly freezing the illuminated samples, we preserve transient photoexcited ion distributions for high-resolution structural and compositional analysis at the nanoscale. Cryogenic scanning transmission electron microscopy techniques (EELS, 4D-STEM) captured the dynamics of photo-induced iodine migration from grain boundaries to centers, identified the buildup of anisotropic strain, and captured the heterogeneous evolution of this process within a single grain. These findings provide new insights into microscopic phase segregation mechanisms and their dynamics, enhancing our understanding of mixed-halide perovskite photostability.

cond-mat.mtrl-sci↗

arXiv2024

Unearthing Neutrino Decoherence from Quantum Spacetime: An Open Quantum Systems Perspective

We investigated the influence of $\kappa$ Minkowski-type quantum spacetime on neutrino oscillations, revealing that spacetime fluctuations introduce a unique energy-dependent power law, $E^{-4}$, in the decoherence effect for relic neutrinos. This effect is particularly pronounced for low-energy neutrinos, such as those from the cosmic neutrino background ($C\nu B$). Our results indicate the potential for new models of low-energy quantum gravity-induced decoherence, which could pave the way for future experiments, such as IceCube-Gen2 and KM3NeT, to further constrain the deformation parameter.

hep-ph↗

arXiv2024

Unveiling gravity's quantum fingerprint through gravitational waves

We introduce an innovative method to explore gravity's quantum aspects using a novel theoretical framework. Our model delves into gravity-induced entanglement (GIE) while sidestepping classical communication limitations imposed by the LOCC principle. Specifically, we connect a non-relativistic two-dimensional quantum oscillator detector with linearly polarized gravitational waves (GWs), leveraging the quantum properties inherent in GWs to observe GIE within the oscillator's quantum states. Because our model adheres to both the ``event" and the ``system" localities, the detected GIE serves as a robust indicator of gravity's quantum nature. Detecting this entanglement via gravitational wave detectors could corroborate gravity's quantization and unveil crucial properties of its sources.

gr-qc↗