Evolution Of Entropy Research Articles

Time evolution of the symmetry resolved entanglement entropy after a mass quench

Abstract In this paper we investigate the properties of the symmetry resolved entanglement entropy after a mass quench in the Ising field theory. Since the theory is free and the post-quench state known explicitly, the one-point function of the relevant (composite) branch point twist field can be computed using form factor techniques, similar to previous work on the branch point twist field and the magnetisation, respectively. We find that the symmetry resolved entropy grows linearly in time at the same rate as the total entropy, and that there are sub-leading oscillatory corrections. This result provides the first explicit computation of the out-of-equilibrium dynamics of the symmetry resolved entropy employing twist fields in quantum field theory and is consistent with existing results based on the quasiparticle picture.

Application of Shannon Entropy to Reaction–Diffusion Problems Using the Stochastic Finite Difference Method

In this study, we introduce Shannon entropy as a key metric for assessing concentration variability in diffusion processes. Shannon entropy quantifies the uncertainty or disorder in the spatial distribution of diffusing particles, providing a novel perspective on diffusion dynamics. This proposed approach enables a more comprehensive characterization of mixing efficiency, equilibrium states, and transient diffusion behavior. Numerical simulations performed using the finite difference method in the MAPLE 2025 symbolic computing environment illustrate how entropy evolution correlates with diffusion kinetics. The computational model used in this study is based on a previously developed framework from our earlier research, ensuring consistency and validation of the results. The findings suggest that Shannon entropy can serve as a robust descriptor of diffusion-driven mixing, with potential applications in engineering, environmental science, and biophysics.

Symmetry resolved entanglement entropy after an inhomogeneous quench

We investigate the non-equilibrium time evolution of symmetry-resolved entanglement entropy (SREE) following an inhomogeneous quench in a critical one-dimensional free fermion system. Using conformal field theory, we derive an exact expression for the SREE and analyze its behavior. We find that, at leading order in the long-time limit, the SREE grows logarithmically as log t. While the equipartition of entanglement holds at leading order, we identify subleading corrections that break it. Our numerical simulations corroborate the analytical predictions with excellent agreement.

The entanglement membrane in 2d CFT: reflected entropy, RG flow, and information velocity

The time evolution of entanglement entropy in generic chaotic many-body systems has an effective description in terms of a minimal membrane, characterised by a tension function. For 2d CFTs, a degenerate tension function reproduces several results regarding the dynamics of the entropy; this stands in contrast to higher dimensions where the tension is non-degenerate. In this paper we use holography to show that, in order to correctly capture the reflected entropy in 2d CFT, one needs to add an additional degree of freedom to the membrane description. Furthermore, we show that the conventional non-degenerate membrane tension function emerges upon introducing a relevant deformation of the CFT, dual to a planar BTZ black hole with scalar hair and with an interior Kasner universe. Finally, we also study the membrane description for reflected entropy and information velocity [1] in higher dimensions.

Simulation of open quantum systems on universal quantum computers

The rapid development of quantum computers has enabled demonstrations of quantum advantages on various tasks. However, real quantum systems are always dissipative due to their inevitable interaction with the environment, and the resulting non-unitary dynamics make quantum simulation challenging with only unitary quantum gates. In this work, we present an innovative and scalable method to simulate open quantum systems using quantum computers. We define an adjoint density matrix as a counterpart of the true density matrix, which reduces to a mixed-unitary quantum channel and thus can be effectively sampled using quantum computers. This method has several benefits, including no need for auxiliary qubits and noteworthy scalability. Moreover, some long-time properties like steady states and the thermal equilibrium can also be investigated as the adjoint density matrix and the true dissipated one converge to the same state. Finally, we present deployments of this theory in the dissipative quantum XY model for the evolution of correlation and entropy with short-time dynamics and the disordered Heisenberg model for many-body localization with long-time dynamics. This work promotes the study of real-world many-body dynamics with quantum computers, highlighting the potential to demonstrate practical quantum advantages.

Inhomogeneous Quantum Quenches of Conformal Field Theory with Boundaries.

We develop a method to calculate generic time-dependent correlation functions for inhomogeneous quantum quenches in (1+1)-dimensional conformal field theory (CFT) induced by sudden Hamiltonian deformations that modulate the energy density inhomogeneously. Our Letter particularly focuses on the effects of spatial boundaries, which have remained unresolved by previous analytical methods. For generic postquench Hamiltonian, we develop a generic method to calculate the correlations by mirroring the system, which otherwise are Euclidean path integrals in complicated spacetime geometries difficult to calculate. On the other hand, for a special class of inhomogeneous postquench Hamiltonians, including the Möbius and sine-square-deformation Hamiltonians, we show that the quantum quenches exhibit simple boundary effects calculable from Euclidean path integrals in a straightforward strip spacetime geometry. Applying our method to the time evolution of entanglement entropy, we find that, for generic cases, the entanglement entropy shows discontinuities (shockwave fronts) propagating from the boundaries. In contrast, such discontinuities are absent in cases with simple boundary effects. We verify that our generic CFT formula matches well with numerical calculations from free-fermion tight-binding models for various quench scenarios.

The entropy of radiation for local quenches in higher dimensions

We investigate the real time dynamics of the radiation produced by a local quench in a d-dimensional conformal field theory (CFT) with d > 2. Using the interpretation of the higher-dimensional twist operator as a conformal defect, we study the time evolution of the entanglement entropy of the radiation across a spherical entangling surface. We provide an analytic estimate for the early- and late-time behavior of the entanglement entropy and derive an upper bound valid at all times. We extend our analysis to the case of a boundary CFT (BCFT) and derive similar results through a detailed discussion of the setup with two conformal defects (the boundary and the twist operator). We conclude with a holographic analysis of the process, computing the time evolution of the holographic entanglement entropy (HEE) as the area of the Ryu-Takayanagi surface in a backreacted geometry. This gives a Page-like curve in agreement with the early- and late-time results obtained with CFT methods. The extension to a holographic BCFT setup is generically hard and we consider the case of a tensionless end-of-the-world brane.

Multi-temperature cooling performance of GdFeCo thin films with high magnetic entropy change and evolution of perpendicular magnetic anisotropy with thickness

Abstract To investigate the effect of thin film thickness on magnetic, magnetocaloric, and perpendicular magnetic anisotropy, we prepared Ta (5nm)/GdFeCo/Ta(5nm) heterostructure with GdFeCo thickness varying from 50 nm to 180 nm. The compensation temperature (Tcomp) and Curie temperature (Tc) shift significantly as the thickness increases. The temperature-dependent magnetization reveals that the Tcomp (224.74 K) is lower than room temperature for the 50 nm thin film, suggesting a CoFe-rich phase. The isothermal magnetic entropy change (|Sm|) is measured at both Tcomp and Tc corresponds to second order magnetic phase transition. |Sm| is found to be 0.24 J/kgK for 90 nm rises to 0.6 J/kgK for 180 nm. Doubling of the thickness from 90 nm to 180 nm results to increase in |Sm| of about 150%. In addition, a significant magnetic entropy change (0.31 J/kgK for 50 nm thin film @ 15 kOe field) is noticed near the Curie temperature for all thin films. For all higher thicknesses, a discernible change in magnetic entropy is observed at Tc. The magnetic anisotropy estimated using Hall effect and MOKE measurements demonstrates perpendicular magnetic anisotropy begins to dominate around room temperature for films with thickness greater than 90 nm as their compensation temperature falls around room temperature. We demonstrate GdFeCo thin films could potentially be suitable for multi-temperature magnetic cooling applications. 


A revisit on linear wavepacket interferometry with phase-locked pulse pairs: spatiotemporal dynamics and evolution of information entropy

Abstract Population-detected coherent spectroscopy employing phase-locked pulse pairs, first realized in fluorescence-detected linear wavepacket interferometry (WPI), lies at the heart of coherent action spectroscopy. In this article, we revisit linear WPI, presenting a unified theoretical description and results of numerical simulation for temporal as well as spatiotemporal dynamics of excited-state population in linear WPI, and connecting it with experimental implementations. We further examine the time evolution of differential Shannon entropy for foreseeable practical applications in quantum computation.

Entropy evolution law of a general linear state for the diffusion noise

Abstract Based on the Kraus operator-sum representation of the analytical solution of the diffusion equation, we obtain the evolution of a general linear state in the diffusion channel. Also, we study the quantum statistical properties of the initial general linear state and its von-Neumann entropy evolution in the diffusion channel, especially find that the entropy evolution is influenced by the diffusion noise and the thermal parameter but without the displacement.

Dynamical analysis of bulk viscous cosmological model in F(T) gravity

Bulk viscous cosmological models are presented in the teleparallel ([Formula: see text], where [Formula: see text] denotes torsion) gravity. In the teleparallel gravity, the Lagrangian of the gravitational action contains a general function [Formula: see text], where [Formula: see text], [Formula: see text] and [Formula: see text] are dimensional constants. Cosmological solutions in Eckart theory and Truncated Israel Stewart theory are talked about in [Formula: see text] gravity form which is one of the most generalized gravity forms in the torsional gravity. The substantial and geometrical prospectives of the cosmological models in Eckart theory and Truncated Israel Stewart theory in [Formula: see text] gravity are deliberated for flat Friedmann–Robertson–Walker space-time. Dynamical analyses of the fixed points of exponential expansion in [Formula: see text] with bulk viscous cosmological models are studied here. The characteristics of the various cosmological parameters such as bulk viscous pressure, energy density, scale factor, Hubble parameter and entropy evolution are studied in Power law and Exponential models. Stability analysis of the exponential models is also argued with cosmic growth in the relevant theories by using directional plots. The cosmological models are supported by observations results.

Thermodynamic aspects of the nonlinear electrodynamics models

In this paper, we consider the nonlinear radiation defined by power law and rational nonlinear electrodynamics (NLE) Lagrangian in homogeneous and isotropic background. These forms of NLE Lagrangian have been studied by using the numerical solution technique to explore the cosmic dynamics in models with matter and dark energy. The universe composed of decelerating and accelerating phases in these models has been examined to understand the evolution of total entropy enclosed by the apparent horizon. The validity of generalized second law of thermodynamics (GSLT) in different cosmic eras of NLE models with and without dark energy has been studied with their corresponding differences.

Chronoentropy: A Model for the Emergence of Time from Entropy and Gravity

We propose a novel theoretical framework, Chronoentropy, which establishes a fundamentalrelationship between entropy (S), time (t), and gravity (G) through the equation:???? ∝ ????????This equation suggests that time emerges as a consequence of entropy evolution under theinfluence of gravity. By integrating concepts from black hole thermodynamics, entropicgravity, and the holographic principle, we derive this relationship and explore its implicationsfor the nature of spacetime. Our approach reinforces the perspective that spacetime is not afundamental entity but rather an emergent phenomenon rooted in information dynamics

Universal dynamics of the entropy of work distribution in spinor Bose–Einstein condensates

Abstract Driving a quantum many-body system across the quantum phase transition (QPT) in the finite time has been concerned in different branches of physics to explore various fundamental questions. Here, we analyze how the underlying QPT affects the work distribution P(W), when the control parameter of a ferromagnetic spinor Bose–Einstein condensates is tuned through the critical point in the finite time. We show that the work distribution undergoes a dramatic change with increasing the driving time τ. To capture the characteristics of the work distribution, we analyze the entropy of P(W) and find three different regions in the evolution of entropy as a function of τ. Specifically, the entropy is insensitive to the driving time in the region of very short τ, while it exhibits a universal power-law decay in the region with intermediate value of τ. In particular, the power-law scaling of the entropy is according with the well-known Kibble-Zurek mechanism. For the region with large τ, the validity of the adiabatic perturbation theory leads to the entropy decay as τ − 2 ln τ . Our results verify the usefulness of the entropy of the work distribution for understanding the critical dynamics and provide an alternative way to experimentally study the nonequilibrium properties in quantum many-body systems.

Information Entropy and Its Periodic Features in Hermite–Gaussian Correlated Schell-Model Beams in a Gradient-Index Fiber

This paper investigates the evolution of information entropy (IE) in Hermite–Gaussian correlated Schell-model (HGcSM) beams propagating through a gradient-index (GRIN) fiber using Shannon information theory. Our results reveal that the IE of such beams evolves periodically, with the beam order significantly influencing its initial distribution. Compared with traditional Gaussian Schell-model beams, HGcSM beams exhibit more complex IE dynamics, characterized by periodically emerging low-entropy regions whose IE decreases with increasing beam order. Furthermore, the fiber’s central refractive index and core radius strongly affect the evolution period and fluctuation amplitude of IE. These findings provide a theoretical basis for optimizing partially coherent beams in optical fiber applications.

Simulating the Evolution of von Neumann Entropy in Black Hole Hawking Radiation Using Biphoton Entanglement.

Addressing the black hole information paradox necessitates the exploration of various hypotheses and theoretical frameworks. Among these, the proposition to utilize quantum entanglement, as introduced by Don N. Page, shows great promise. This study builds upon Page's theoretical foundation and proposes a simplified model for elucidating the evolution of black hole von Neumann entropy. This model simulates the process of Hawking radiation using entangled photon pairs. Our experiment suggests that quantum entanglement may offer a plausible avenue for resolving the paradox, thereby lending support to Page's proposal. The results suggest that this model may contribution to the exploration of one of the most profound puzzles in theoretical physics.

Evolution of entanglement entropy at SU(N) deconfined quantum critical points.

Over past two decades, the enigma of the deconfined quantum critical point (DQCP) has attracted broad attention across physics communities, as it offers a new paradigm beyond the Landau-Ginzburg-Wilson framework. However, the nature of DQCP has been controversial based on conflicting numeric results. In our work, we demonstrate that an anomalous logarithmic behavior in the entanglement entropy (EE) persists in a class of models analogous to the DQCP. On the basis of quantum Monte Carlo computation of the EE on SU(N) DQCP spin models, we show that for a series of N smaller than a critical value, the anomalous logarithmic behavior always exists, which implies that previously determined DQCPs in these models do not belong to conformal fixed points. In contrast, when [Formula: see text] with an [Formula: see text] we evaluate to lie between 7 and 8, DQCPs are consistent with conformal fixed points that can be understood within the Abelian Higgs field theory.

Kinetics of quantum reaction-diffusion systems

We discuss many-body fermionic and bosonic systems subject to dissipative particle losses in arbitrary spatial dimensions dd, within the Keldysh path-integral formulation of the quantum master equation. This open quantum dynamics represents a generalisation of classical reaction-diffusion dynamics to the quantum realm. We first show how initial conditions can be introduced in the Keldysh path integral via boundary terms. We then study binary annihilation reactions A+A\to \emptysetA+A→∅, for which we derive a Boltzmann-like kinetic equation. The ensuing algebraic decay in time for the particle density depends on the particle statistics. In order to model possible experimental implementations with cold atoms, for fermions in d=1d=1 we further discuss inhomogeneous cases involving the presence of a trapping potential. In this context, we quantify the irreversibility of the dynamics studying the time evolution of the system entropy for different quenches of the trapping potential. We find that the system entropy features algebraic decay for confining quenches, while it saturates in deconfined scenarios.

Evolution of interior entropy of a loop quantum-corrected black hole pierced by a cosmic string

Evolution of interior entropy of a loop quantum-corrected black hole pierced by a cosmic string

Improved irradiation resistance of high entropy nanolaminates through interface engineering

Abstract Bi-phase interfacial engineering is an effective method for improving irradiation resistance, as interfaces play a critical role in defect generation and annihilation. In this work, molecular dynamics (MD) simulations are performed to investigate the evolution of the high entropy crystalline/amorphous laminates under ion irradiation. The effects of the crystalline/amorphous interface (ACI) on the distribution of point defects in the high entropy alloy (HEA) as well as on the microstructure evolution in metallic glass (MG) plates are investigated. During irradiation, fewer activated point defects were found in the HEA plate of the MG/HEA laminates compared to a free-standing HEA. In addition, the interface acts as a defect sink, accelerating the annihilation of interstitials at the interface. As a result, residual vacancies accumulate in the crystalline region following the first cascade, leading to a segregated distribution and an imbalance between the vacancies and interstitials in the HEA plate. Vacancy accumulation and clustering are responsible for the formation of stacking faults and complex dislocation networks in the HEA plate in the subsequent overlapping cascades. The interface also acts as a crystallization seed, accelerating the crystallization of the MG plate during irradiation process. However, the structural damage in the MG plate is mitigated by the redistribution of the free volume generated in the collision cascade zone, resulting in structural stability of the MG plate in the overlapping cascades.