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This work explores the manner in which classical phase space distribution functions converge to the microcanonical distribution. We first prove a theorem about the lack of convergence, then define a generalization of the coarse-graining procedure that leads to convergence. We prove that the time evolution of phase space distributions is an isometry for a broad class of statistical distance metrics, implying that ensembles do not get any closer to (or farther from) equilibrium, according to these metrics. This extends the known result that strong convergence of phase space distributions to the microcanonical distribution does not occur. However, it has long been known that weak convergence can occur, such that coarse-grained distributions—defined by partitioning phase space into a finite number of cells—converge pointwise to the microcanonical distribution. We define a generalization of coarse-graining that removes the need for partitioning phase space into cells. We prove that our generalized coarse-grained distribution converges pointwise to the microcanonical distribution if the dynamics are strong mixing. As an example, we study an ensemble of triangular billiard systems. [ABSTRACT FROM AUTHOR]

We consider how the absence of thermalization affects the classical Coulomb blockade regime in quantum dots. By solving the quantum kinetic equation in the experimentally accessible regime when the dot has two relevant occupation states, we calculate the current–voltage characteristics for arbitrary coupling to the leads. If the couplings are strongly asymmetric, the Coulomb staircase is practically reduced to the first step, which is independent of the charging energy, when the Fermi energy is comparatively small, while the standard thermalized results are recovered in the opposite case. When the couplings are of the same order, the absence of thermalization has a new, striking signature—a robust additional peak in the differential conductance. [ABSTRACT FROM AUTHOR]

The projected ensemble is based on the study of the quantum state of a subsystem A conditioned on projective measurements in its complement. Recent studies have observed that a more refined measure of the thermalization of a chaotic quantum system can be defined on the basis of convergence of the projected ensemble to a quantum state design, i.e. a system thermalizes when it becomes indistinguishable, up to the k th moment, from a Haar ensemble of uniformly distributed pure states. Here we consider a random unitary circuit with the brick-wall geometry and analyze its convergence to the Haar ensemble through the frame potential and its mapping to a statistical mechanical problem. This approach allows us to highlight a geometric interpretation of the frame potential based on the existence of a fluctuating membrane, similar to those appearing in the study of entanglement entropies. At large local Hilbert space dimension q, we find that all moments converge simultaneously with a time scaling linearly in the size of region A, a feature previously observed in dual unitary models. However, based on the geometric interpretation, we argue that the scaling at finite q on the basis of rare membrane fluctuations, finding the logarithmic scaling of design times t k = O (log ⁡ k) . Our results are supported with numerical simulations performed at q = 2. [ABSTRACT FROM AUTHOR]

For any local, translation-covariant quantum field theory on Minkowski spacetime, we prove that two distinct states that are invariant under the inertial time evolutions in different inertial reference frames are disjoint, i.e. neither state is a perturbation of the other, if the states are primary, have separating Gelfand–Naimark–Segal (GNS) vectors, and satisfy a timelike cluster property called the mixing property. These conditions are fulfilled by the inertial Kubo–Martin–Schwinger (KMS) states of the free scalar field, thus showing that a state satisfying the KMS condition relative to one inertial frame is far from thermal equilibrium relative to other inertial frames. We review the property of return to equilibrium (RTE) in open quantum systems theory and discuss the implications of disjointness on the asymptotic behavior of detector systems coupled to states of a free massless scalar field. We argue that the coupled system of an Unruh–DeWitt detector moving with constant velocity relative to the field in a KMS state, or an excitation thereof, cannot thermalize under generic conditions. This leads to an illustration of the physical differences between heat baths in inertial systems and the alleged “heat bath” of the Unruh effect. This paper also sketches the construction and RTE property of the quantum dynamical system of an Unruh–DeWitt detector coupled to a massless scalar field in a KMS state relative to the inertial rest frame of the detector. [ABSTRACT FROM AUTHOR]

Majorization is a fundamental model of uncertainty with several applications in areas ranging from thermodynamics to entanglement theory, and constitutes one of the pillars of the resource-theoretic approach to physics. Here, we improve on its relation to measurement apparatuses. In particular, after discussing what the proper notion of second law in this scenario is, we show that, for a sufficiently large state space, any family of entropy-like functions constituting a second law must be countably infinite. Moreover, we provide an analogous result for a variation of majorization known as thermo-majorization which, in fact, does not require any constraint on the state space provided the equilibrium distribution is not uniform. Finally, we discuss the applicability of our results to molecular diffusion and catalytic majorization. In this regard, we consider a variation of majorization used in plasma physics as a model of molecular diffusion and show that no finite family of entropy-like functions constituting a second law of molecular diffusion exists. Moreover, we show how our results are useful when dealing with a conjecture regarding catalytic majorization (i.e. trumping). In particular, we show that the sort of characterizations of trumping that have been considered before require an infinite family of real-valued functions. [ABSTRACT FROM AUTHOR]

Quantum thermodynamics aims to extend standard thermodynamics and nonequilibrium statistical physics to systems with sizes well below the thermodynamic limit. It is a rapidly evolving research field that promises to change our understanding of the foundations of physics, while enabling the discovery of novel thermodynamic techniques and applications at the nanoscale. Thermal management has turned into a major obstacle in pushing the limits of conventional digital computers and could also represent a crucial issue for quantum computers. The practical realization of quantum computers with superconducting loops requires working at cryogenic temperatures to eliminate thermal noise, and ion-trap qubits also need low temperatures to minimize collisional noise. In both cases, the sub-nanometric sizes also bring about the thermal broadening of the quantum states; and even roomtemperature photonic computers eventually require cryogenic detectors. A number of thermal and thermodynamic questions, therefore, take center stage, such as quantum re-definitions of work and heat, thermalization and randomization of quantum states, the overlap of quantum and thermal fluctuations, and many others, even including a proper definition of temperature for the small open systems constantly out of equilibrium that are the qubits. This overview provides an introductory perspective on a selection of current trends in quantum thermodynamics and their impact on quantum computers and quantum computing, with language that is accessible to postgraduate students and researchers from different fields. [ABSTRACT FROM AUTHOR]

We show, without relying on any unproven assumptions, that a low-density free fermion chain exhibits thermalization in the following (restricted) sense. We choose the initial state as a pure state drawn randomly from the Hilbert space in which all particles are in half of the chain. This represents a nonequilibrium state such that the half chain containing all particles is in equilibrium at infinite temperature, and the other half chain is a vacuum. We let the system evolve according to the unitary time evolution determined by the Hamiltonian and, at a sufficiently large typical time, measure the particle number in an arbitrary macroscopic region in the chain. In this setup, it is proved that the measured number is close to the equilibrium value with probability very close to one. Our result establishes the presence of thermalization in a concrete model in a mathematically rigorous manner. The key for the proof is a new strategy to show that a randomly generated nonequilibrium initial state typically has a large enough effective dimension by using only mild verifiable assumptions. In the present work, we first give general proof of thermalization based on two assumptions, namely, the absence of degeneracy in energy eigenvalues and a property about the particle distribution in energy eigenstates. We then justify these assumptions in a concrete free-fermion model, where the absence of degeneracy is established by using number-theoretic results. This means that our general result also applies to any lattice gas models in which the above two assumptions are justified. To confirm the potential wide applicability of our theory, we discuss some other models for which the essential assumption about the particle distribution is easily verified, and some non-random initial states whose effective dimensions are sufficiently large. [ABSTRACT FROM AUTHOR]

The problem of quantum measurement can be partially resolved by incorporating a process of spontaneous disentanglement into quantum dynamics. A modified master equation is proposed, which contains a nonlinear term giving rise to both spontaneous disentanglement and thermalization. It is found that the added nonlinear term enables limit cycle steady states, which are prohibited in standard quantum mechanics. This finding suggests that an experimental observation of such a limit cycle steady state can provide an important evidence supporting the spontaneous disentanglement hypothesis. [ABSTRACT FROM AUTHOR]

Quantum thermodynamics aims to extend standard thermodynamics and non-equilibrium statistical physics to systems with sizes well below the thermodynamic limit. It is a rapidly evolving research field that promises to change our understanding of the foundations of physics, while enabling the discovery of novel thermodynamic techniques and applications at the nanoscale. Thermal management has turned into a major obstacle in pushing the limits of conventional digital computers and could also represent a crucial issue for quantum computers. The practical realization of quantum computers with superconducting loops requires working at cryogenic temperatures to eliminate thermal noise, and ion-trap qubits also need low temperatures to minimize collisional noise. In both cases, the sub-nanometric sizes also bring about the thermal broadening of the quantum states; and even room-temperature photonic computers eventually require cryogenic detectors. A number of thermal and thermodynamic questions, therefore, take center stage, such as quantum re-definitions of work and heat, thermalization and randomization of quantum states, the overlap of quantum and thermal fluctuations, and many others, even including a proper definition of temperature for the small open systems constantly out of equilibrium that are the qubits. This overview provides an introductory perspective on a selection of current trends in quantum thermodynamics and their impact on quantum computers and quantum computing, with language that is accessible to postgraduate students and researchers from different fields.

The X-ray Integral Field Unit (X-IFU) is one of the two focal plane detectors of Athena, a large-class high energy astrophysics space mission approved by ESA in the Cosmic Vision 2015–2025 Science Program. The X-IFU consists of a large array of transition edge sensor micro-calorimeters that operate at ~100 mK inside a sophisticated cryostat. To prevent molecular contamination and to minimize photon shot noise on the sensitive X-IFU cryogenic detector array, a set of thermal filters (THFs) operating at different temperatures are needed. Since contamination already occurs below 300 K, the outer and more exposed THF must be kept at a higher temperature. To meet the low energy effective area requirements, the THFs are to be made of a thin polyimide film (45 nm) coated in aluminum (30 nm) and supported by a metallic mesh. Due to the small thickness and the low thermal conductance of the material, the membranes are prone to developing a radial temperature gradient due to radiative coupling with the environment. Considering the fragility of the membrane and the high reflectivity in IR energy domain, temperature measurements are difficult. In this work, a parametric numerical study is performed to retrieve the radial temperature profile of the larger and outer THF of the Athena X-IFU using a Finite Element Model approach. The effects on the radial temperature profile of different design parameters and boundary conditions are considered: (i) the mesh design and material, (ii) the plating material, (iii) the addition of a thick Y-cross applied over the mesh, (iv) an active heating heat flux injected on the center and (v) a Joule heating of the mesh. The outcomes of this study have guided the choice of the baseline strategy for the heating of the Athena X-IFU THFs, fulfilling the stringent thermal specifications of the instrument. [ABSTRACT FROM AUTHOR]

One-dimensional chains are used as a fundamental model of condensed matter, and have constituted the starting point for key developments in nonlinear physics and complex systems. The pioneering work in this field was proposed by Fermi, Pasta, Ulam and Tsingou in the 50s in Los Alamos. An intense and fruitful mathematical and physical research followed during these last 70 years. Recently, a fresh look at the mechanisms at the route of thermalization of such systems has been provided through the lens of the Wave Turbulence approach. In this review, we give a critical summary of the results obtained in this framework. We also present a series of open problems and challenges that future work needs to address. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the influence of temperature and momentum-dependent coherence-chaos radiations on particle excretion from a fluid with quantum supremacy. The dynamics interpretation of a system can become exceedingly complex and femtoscopy is an efficient quantum tool that captures and explores the complicated dynamical properties. This research presents a comprehensive and brief analysis of fluid in the context of quantum interference for partially chaotic systems, as well as novel findings for chaos synchronization of identical bosons in the extending source are evaluated. The eminence of coherence on chaotic production has been demonstrated using correlation plots in the existence of the quantum influence. The temperature profile is described with the mitigation of graphs created for various flow peculiarities, and the density equations are derived through feasible interferences transformation approaches. Results exhibit the quantitative data of chaotic and droplets exhibiting coherence features and illustrate a premise that depicts motivated conversions between cold and hot bosonic particles crossover during the expanding of emitted sources. The emergent phase can contain a partially thermalized distribution of particles which is elucidated by the swiftness of the hadronic transition and this phase reveals marvelous entirely quantum correlations according to our findings. In particular, we formulate the normalized interception for the hybrid system using particular methods to probe the source configurations. [ABSTRACT FROM AUTHOR]

A benchmark has been developed using a pulsed slowing-down-time experiment to isolate the thermalization process in graphite. The experiment was conducted at the Oak Ridge Electron Linear Accelerator facility at Oak Ridge National Laboratory, and it measured the time spectrum of neutrons leaking from a graphite pile during slowing down and thermalization within graphite. Simulations of the benchmark experiment were performed using the MCNP6.1 Monte Carlo code and the ENDF/B-VII.1 and ENDF/B-VIII.0 cross-section databases. The benchmark provides a time spectrum (i.e., time-dependent counts in a detector) that allows for validation of the graphite thermal scattering libraries (TSLs). The impact on the simulations using a suite of graphite TSLs was compared with the experimental results. Given the density of nuclear graphite, the TSL corresponding to graphite with 30% porosity, as implemented in ENDF/B-VIII.0, was found to most accurately represent the measured time spectrum corresponding to the thermal energy range with an average deviation of ±1.7%. [ABSTRACT FROM AUTHOR]

The temperature dependency of photovoltaic power conversion efficiency (PCE) has been a key challenge to solar applications due to intrinsic processes. Herein, an alternative strategy is developed by modulating the solar light spectrum with a series of photonic hybrids. Transparent thin films are synthesized with the solutions of porphyrin compounds and iron oxides which exhibit strong absorptions in the UV and IR regions. These spectral modulating thin films are photonically tuned via compositional optimization to absorb photons near 400 nm and above 1127 nm from solar spectrum to reduce thermalization and sub‐bandgap absorption. These spectral modulators are applied in a particular configuration above a commercial silicon panel to partially filter the simulated solar light. The PCE of the silicon panel suffers a significant decrease due to temperature increase from 22.9 to 92.9 °C after 60 min solar irradiation, resulting in a PCE decrease from 25.1% to 16.3%. With the transparent spectral modulators, upon solar irradiation for 60 min, the maximum PCE has maintained at 20.5%. The mechanisms of PCE enhancement are identified based on reduced thermalization and sub‐bandgap absorption. [ABSTRACT FROM AUTHOR]

In this paper, we construct the metric tensor and volume for the manifold of purifications associated with an arbitrary reduced density operator ρ S . We also define a quantum coarse-graining (CG) to study the volume where macrostates are the manifolds of purifications, which we call surfaces of ignorance (SOI), and microstates are the purifications of ρ S . In this context, the volume functions as a multiplicity of the macrostates that quantifies the amount of information missing from ρ S . Using examples where the SOI are generated using representations of S U (2) , S O (3) , and S O (N) , we show two features of the CG: (1) A system beginning in an atypical macrostate of smaller volume evolves to macrostates of greater volume until it reaches the equilibrium macrostate in a process in which the system and environment become strictly more entangled, and (2) the equilibrium macrostate takes up the vast majority of the coarse-grained space especially as the dimension of the total system becomes large. Here, the equilibrium macrostate corresponds to a maximum entanglement between the system and the environment. To demonstrate feature (1) for the examples considered, we show that the volume behaves like the von Neumann entropy in that it is zero for pure states, maximal for maximally mixed states, and is a concave function with respect to the purity of ρ S . These two features are essential to typicality arguments regarding thermalization and Boltzmann's original CG. [ABSTRACT FROM AUTHOR]

In this work, we study the evolution of Boltzmann’s entropy in the context of free expansion of a one-dimensional interacting gas inside a box. Our interacting particle model is a gas of hard point particles with alternating masses, a system known to have good ergodicity properties. Boltzmann’s entropy is defined for single microstates and is given by the phase-space volume occupied by microstates with the same value of macrovariables which are coarse-grained physical observables. We demonstrate the idea of typicality in the growth of the Boltzmann’s entropy for two choices of macro-variables—the single particle phase space distribution and the hydrodynamic fields. Due to the presence of interactions, the growth curves for both these entropies are observed to converge to a monotonically increasing limiting curve, on taking the appropriate order of limits, of large system size and small coarse-graining scale. Moreover, we observe that the limiting growth curves for the two choices of entropies are identical as implied by local thermal equilibrium. We also discuss issues related to finite size and finite coarse gaining scale which lead to interesting features such as oscillations in the entropy growth curve. We also discuss shocks observed in the hydrodynamic fields. [ABSTRACT FROM AUTHOR]

This study aims at understanding the effect of the thermalization of secondary electrons produced by incident heavy-ion impact ionization on plasma formation. The motions of the secondary electrons were simulated using pseudo-initial secondary electron energy distribution functions. These simulations allowed us to estimate the times when thermalization occurred and the probabilities of secondary electrons escaping the electric field created near the incident ion path according to the initial secondary electron energy distribution functions. The probabilities and thermalization processes were found to be almost independent of these functions which indicated that the secondary electrons were thermalized before the plasma was formed. [ABSTRACT FROM AUTHOR]

We celebrate the legacies of our friend and mentor Professor Lianshou Liu who was one of the pioneers for the phenomenology of multi-particle interactions and initiated the physics of relativistic heavy-ion collisions in China. In this article, we discuss some of the recent exciting experimental observations on the collective phenomena including collectivity, chirality, criticality, strangeness production, and thermal equilibrium in high-energy nuclear collisions. Future directions, especially the physics at high baryon density, will be discussed with a focus on the first-order phase boundary and hyperon–nucleon interactions. [ABSTRACT FROM AUTHOR]

We overview our recent experimental studies on the nonlinear spatial reshaping of multimode beams at the output of multimode optical fibers. We use a holographic mode decomposition technique, which permits to reveal the variation of the spatial mode composition at the fiber output, as determined by either conservative (the Kerr effect) or dissipative (Raman scattering) nonlinear processes. For the first case, we consider the effect of spatial beam self-cleaning, and we compare experimental mode decompositions with predictions based on the thermodynamic theory, including the case of beams carrying nozero orbital angular momentum. For the second case, we analyze the beam mode content at the output of a Raman laser based on a graded index multimode fiber. [ABSTRACT FROM AUTHOR]

We develop meanfield approximation and numerical quadrature schemes for the evaluation of Angular-Dependent interatomic Potentials (ADPs) for magnesium and magnesium hydrides at finite temperature (thermalization) and arbitrary atomic molar fractions (mixing) within a non-equilibrium statistical mechanical framework and derive local equilibrium relations. We numerically verify and experimentally validate the accuracy and fidelity of the resulting thermalized/mixed ADPs (TADPs) by means of selected numerical tests including free entropy, heat capacity, thermal expansion, molar volumes, equation of state and elastic constants. We show that the local equilibrium properties predicted by TADPs agree closely with those computed directly from ADP by means of Molecular Dynamics (MD). • We develop meanfield approximation for the evaluation of ADPs at finite temperature. • We verify and validate the accuracy and fidelity of the thermalized/mixed ADPs. • Local equilibrium properties predicted by TADPs agree with those computed using MD. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate energy transfers and thermalization in an isolated ensemble of realistic gas particles. We perform a grid-free classical molecular dynamics simulation of two-dimensional Lenard-Jones gas. We start our simulation with a large-scale vortex akin to a hydrodynamic flow and study its non-equilibrium behavior till it attains thermal equilibrium. In the intermediate phases, small wavenumbers (k) exhibit E (k) ∝ k − 3 kinetic energy spectrum, whereas large wavenumbers exhibit E (k) ∝ k spectrum. Asymptotically, E (k) ∝ k for the whole range of k , thus indicating thermalization. These results are akin to those of Euler turbulence despite complex collisions and interactions among the particles. • Demonstration of energy transfers in real gas particles. • Simulation of turbulent flows using grid-free classical molecular dynamics simulation and Direct Numerical Simulation. • The emergence of hydrodynamic energy flux in many particle systems. • Thermalization in a real gas system. [ABSTRACT FROM AUTHOR]

We show that the long-time limit of the two-point correlation function obtained via the standard quantum regression theorem (QRT), a standard tool to compute correlation functions in open quantum systems, does not respect the Kubo–Martin–Schwinger equilibrium condition to the non-zero order of the system-bath coupling. We then follow the recently developed Heisenberg operator method for open quantum systems and by applying a ‘ weak ’ Markov approximation, derive a new modified version of the QRT that not only respects the KMS condition but further predicts exact answers for certain paradigmatic models in specific limits. We also show that in cases where the modified QRT does not match with exact answers, it always performs better than the standard QRT.

We replace a Hamiltonian with a modular Hamiltonian in the spectral form factor and the level spacing distribution function. This study establishes a connection between quantities within Quantum Entanglement and Quantum Chaos. To have a universal study for Quantum Entanglement, we consider the Gaussian random 2-qubit model. The maximum violation of Bell’s inequality demonstrates a positive correlation with the entanglement entropy. Thus, the violation plays an equivalent role as Quantum Entanglement. We first provide an analytical estimation of the relation between quantum entanglement quantities and the dip when a subregion only has one qubit. The time of the first dip is monotone for entanglement entropy. The dynamics in a subregion is independent of the initial state at a late time. It is one of the signaling conditions for classical chaos. We also extend our analysis to the Gaussian random 3-qubit state, and it indicates a similar result. The simulation shows that the level spacing distribution function approaches GUE at a late time. In the end, we develop a technique within QFT to the spectral form factor for its relation to an n-sheet manifold. We apply the technology to a single interval in CFT2 and the spherical entangling surface in N = 4 super Yang-Mills theory. The result is one for both cases, but the Rényi entropy can depend on the Rényi index. For the case of CFT2, it indicates the difference between the continuum and discrete spectrum. [ABSTRACT FROM AUTHOR]

Here we analyze a numerical model of a cubic lattice with linear elasticity and random heat sources on its upper and lower boundaries, consider methods which can be used for visualizing the kinetics of energy transfer and recording the history of events in such a system, and present some general results for its 2D and 3D cases. Also considered are the formation and propagation of localized energy states ("energy bundles") and the rise of thermal resistance. It is shown that the thermal resistance at the interfaces of media with different parameters can be used for efficient heat removal and elimination of side effects in friction in a modified Prandtl–Tomlinson model with energy losses via substrate strain generation. [ABSTRACT FROM AUTHOR]

Two-dimensional semiconductors exhibit pronounced many-body effects and intense optical responses due to strong Coulombic interactions. Consequently, subtle differences in photoexcitation conditions can strongly influence how the material dissipates energy during thermalization. Here, using multiple excitation spectroscopies, we show that a distinct thermalization pathway emerges at elevated excitation energies, enhancing the formation of trions and charged biexcitons in single-layer WSe 2 by up to 2× and 5× , respectively. Power- and temperature-dependent measurements lend insights into the origin of the enhancement. These observations underscore the complexity of excited state relaxation in monolayer semiconductors, provide insights for the continued development of carrier thermalization models, and highlight the potential to precisely control excitonic yields and probe nonequilibrium dynamics in 2D semiconductors.

To illustrate Boltzmann’s construction of an entropy function that is defined for a microstate of a macroscopic system, we present here the simple example of the free expansion of a one dimensional gas of non-interacting point particles. The construction requires one to define macrostates, corresponding to macroscopic variables. We define a macrostate M by specifying the fraction of particles in rectangular boxes Î" x Î" v of the single particle position-velocity space { x, v }. We verify that when the number of particles is large the Boltzmann entropy, S B(t), of a typical microstate of a nonequilibrium ensemble coincides with the Gibbs entropy of the coarse-grained time-evolved one-particle distribution associated with this ensemble. S B(t) approaches its maximum possible value for the dynamical evolution of the given initial state. The rate of approach depends on the size of Î" v in the definition of the macrostate, going to zero at any fixed time t when Î" v â†' 0. Surprisingly the different curves S B(t) collapse when time is scaled with Î" v as: t ∼ Ď„ /Î" v. We find an explicit expression for S B(Ď„) in the limit Î" v â†' 0. We also consider a different, more hydrodynamical, definition of macrostates for which S B(t) is monotone increasing, unlike the previous one which has small decaying oscillations near its maximum value. Our system is non-ergodic, non-chaotic and non-interacting; our results thus illustrate that these concepts are not as relevant as sometimes claimed, for observing macroscopic irreversibility and entropy increase. Rather, the notions of initial conditions, typicality, large numbers and coarse-graining are the important factors. We demonstrate these ideas through extensive simulations as well as analytic results. [ABSTRACT FROM AUTHOR]

We put forward an attempt towards building a possible theoretical model to understand the observer dependent thermalization of black hole horizon. The near horizon Hamiltonian for a massless, chargeless particle is xp type. This is unstable in nature and so the horizon can induce instability in a system. The particle in turn finds the horizon thermal when it interacts with it. We explicitly show this in the Schrodinger as well as in Heisenberg pictures by taking into account the time evolution of the system under this Hamiltonian. Hence we postulate that existing instability near the horizon can be one of the potential candidates for explaining the black hole thermalization. [ABSTRACT FROM AUTHOR]

We consider the H-theorem in an isolated quantum harmonic oscillator through the time-dependent Schrödinger equation. The effect of potential in producing entropy is investigated in detail, and we found that including a barrier potential into a harmonic trap would lead to the thermalization of the system, while a harmonic trap alone would not thermalize the system. During thermalization, Shannon entropy increases, which shows that a microscopic quantum system still obeys the macroscopic thermodynamics law. Meanwhile, initial coherent mechanical energy transforms to incoherent thermal energy during thermalization, which exhibiting the decoherence of an oscillating wave packet featured by a large decreasing of autocorrelation length. When reaching thermal equilibrium, the wave packet comes to a halt, with the density distributions both in position and momentum spaces well-fitted by a microcanonical ensemble of statistical mechanics. [ABSTRACT FROM AUTHOR]

We studied the thermal features of magnetized plasmas in the Martian subsolar magnetosheath using MAVEN's observations from 2014 to 2019. Statistical analyses show that the average ion and electron temperature in the Martian subsolar magnetosheath are 210 and 31 eV, respectively, which are significantly lower than their counterparts in the subsolar magnetosheaths of Earth and Saturn which both have an inherent magnetosphere. However, the ratio T ¯ i / T ¯ e in the Martian subsolar magnetosheath is about 6.8, which is very close to that of Earth and Saturn. We further investigated the relationship between T i / T e and the bulk ion flow velocity V i , as well as the relationship between the total plasma beta β and V i . Results show that the average value of T i / T e when V i < 300 km / s is considerably higher than when V i > 300 km / s . A value of V i closer to 250–300 km/s leads to a higher average value of the total plasma beta β. These results confirm the prediction of previous researchers, that there is not enough room for solar wind thermalization as the distance between the Martian bow shock and the so-called obstacle is of the order of a solar wind proton gyroradius. [ABSTRACT FROM AUTHOR]

Results of calculation of the absorption spectrum of phosphorus oxide (PO) corresponding to the A2Σ+ (v′ = 0) − X 2Π (v′′ = 0) transition are presented. The calculation is performed taking into account the perturbation of the v′ = 0 level of the A2Σ+ state by the v′ = 4 level of the b4Σ− state. The efficiency of laser excitation of PO molecules is estimated as a function of the spectral parameters of the radiation. The time dependence of the efficiency of the excitation of PO fragments is calculated for a real atmosphere under two-pulse laser fragmentation of organophosphates for specified spectral linewidths Δλ and center positions λ0. [ABSTRACT FROM AUTHOR]

Novel cluster spin model with interactions and disorder is introduced and studied. In specific type of interactions, we find an extensive number of local integrals of motions (LIOMs), which are a modified version of the stabilizers in quantum information, i.e., mutually commuting operators specifying all quantum states in the system. These LIOMs can be defined for any strength of the interactions and disorder, and are of compact-support instead of exponentially-decaying tail. Hence, even under the presence of interactions, integrability is held, and all energy eigenstates are labeled by these LIOMs and can be explicitly obtained. Integrable dynamics is, then, expected to occur. The compact-support nature of the LIOMs crucially prevents the thermalization and entanglement spreading. We numerically investigate dynamics of the system governed by the existence of the compact-support LIOMs, and clarify the effects of additional interactions, which break the compact-support nature of the LIOMs. There, we find that the ordinary many-body localization behaviors emerge, such as the logarithmic growth of the entanglement entropy in the time evolution. Besides the ergodicity breaking dynamic, we find that symmetry protected topological order preserves for specific states even in the presence of the interactions. [ABSTRACT FROM AUTHOR]

In this letter we discuss the energy dissipation of short-lived para -positronium (p -Ps) in polymers and silica glass. The S parameter characterizing the Doppler broadening of p -Ps annihilation is determined from the previously reported systematic data of positron annihilation age momentum correlation for various polymers and silica glass. A comparison of the S parameter with that expected for thermalized p -Ps trapped in a free volume reveals that p -Ps is not thermalized and possesses excess energy in fluorinated polymers and silica glass, indicating that it is difficult for Ps to lose energy in substances containing heavy elements such as fluorine and silicon. [ABSTRACT FROM AUTHOR]

The conception of almost complete revivals has been introduced recently. In a quantum many-body system local observable may exhibit an almost complete revival to its maximal value at the predetermined moment of time. In this paper we extend the original procedure such that the revival may be from an arbitrary point on the Bloch sphere to the arbitrary point. Furthermore in the proposed procedure the reviving and collapsing sites are not necessarily the same. We also demonstrate that for spins higher than almost complete revivals are suppressed as . [ABSTRACT FROM AUTHOR]

The goal of collider programs of high energy heavy-ion collisions is to produce a form of matter that can test non-perturbative aspects of Quantum Chromodynamics (QCD), the theory of strong interactions. One of the primary predictions from a computational approach to this quantum field theory is the existence of distinct thermodynamic states of QCD, particularly a state of deconfined quarks and gluons. An important step in establishing changes of state of QCD matter is to demonstrate that femto-scale system created in the laboratory can attain thermodynamic equilibrium. We present such a demonstration by checking that event-to-event fluctuations of several different conserved quantities have a consistent treatment in a grand canonical ensemble through a common temperature and chemical potentials. A key component of this work is that we used cumulants of up to third order in the net proton number, charge, and strangeness. We found a clear indication that the femto-scale fireball is thermalized when the collision energy in the centre of mass, sNN, is high enough. Also, the use of higher order cumulants, within the framework of grand canonical ensemble, reveals for the first time that the fireballs created at lower sNN are not in thermodynamic equilibrium. This opens the door to further studies of the approach to equilibrium, and the effects that a critical point in the phase diagram of QCD could have on such phenomena.

ReS2, a layered transition metal dichalcogenide (TMD) with reduced crystal symmetry exhibiting unique anisotropic and layer-independent properties, holds great potential for optoelectronic and photonic applications. Despite a flurry of research activities in the third-order nonlinear optical response of TMDs, tuning those properties in a completely reversible manner in real time is a challenge and remains largely unexplored. Here, we experimentally demonstrate band edge carrier-induced sign reversal of the ultrafast third-order nonlinear optical response in few-layer (4–8) ReS2 nanoflakes. In particular, saturable absorption observed before hot carrier thermalization (<0.3 ps) is tuned to reverse saturable absorption (RSA) after the carrier thermalized (>0.6 ps) at the band edge and defects using a single-color pump–probe intensity scan (I-scan) technique. RSA in our experiment is due to the two-step two single-photon absorption of the long-lived (∼1000s of ps from our ultrafast transient absorption) carriers at the band edges and defects. Motivated by the results, a liquid cell-based high-performance few-layer ReS2 optical limiter is fabricated with a remarkable 0.1 GW/cm2 onset threshold and 0.64 limiting differential transmittance better than the other optical-limiting materials. These results offer a direction to manipulate the nonlinear optical response of materials which otherwise requires a large electric field, high intensity, or efficient charge transfer between donor and acceptor pairs. [ABSTRACT FROM AUTHOR]

I explore the processes of equilibration exhibited by the Adapted Caldeira–Leggett (ACL) model, a small unitary "toy model" developed for numerical studies of quantum decoherence between an SHO and an environment. I demonstrate how dephasing allows equilibration to occur in a wide variety of situations. While the finite model size and other "unphysical" aspects prevent the notions of temperature and thermalization from being generally applicable, certain primitive aspects of thermalization can be realized for particular parameter values. I link the observed behaviors to intrinsic properties of the global energy eigenstates, and argue that the phenomena I observe contain elements which might be key ingredients that lead to ergodic behavior in larger more realistic systems. The motivations for this work range from curiosity about phenomena observed in earlier calculations with the ACL model to much larger questions related to the nature of equilibrium, thermalization, and the emergence of physical laws. [ABSTRACT FROM AUTHOR]

The thermal neutron porosity is routinely acquired in almost every well. When combined with the density, gamma ray and resistivity logs, the basic petrophysical parameters of a reservoir are evaluated. The design of the thermal neutron tool is simple, but its interpretation is complex and affected by the formation constituents. The most challenging situation occurs when the formation contains elements with high absorption probability of the thermal neutrons. The existence of such elements changes the neutron transport parameters and results in a false increase in the measured porosity. The problem is reported by many users throughout the years. In 1993, higher thermal neutron porosity is reported due to the existence of an iron-rich mineral, Siderite, in the Nazzazat and Baharia formations in Egypt. Siderite and all iron-rich minerals have high thermal neutrons absorption probability. Recently, in 2018, high thermal neutron porosity in Unayzah field in Saudi Arabia is also reported due to the existence of few parts per million of gadolinium. Gadolinium is a rare element that has high probability of thermal neutron absorption. Currently, none of the existing commercial petrophysics software(s) have modules to correct the thermal neutron porosity for such effects. This represents a challenge to the petrophysicists to properly calculate the actual reservoir porosity. In this paper, the effects of the rare elements and other minerals with high thermal neutron absorption probability on the thermal neutron porosity are discussed, and a correction methodology is developed and tested. The methodology is based on integrating the tool design and the physics of the neutron transport to perform the correction. The details of the correction steps and the correction algorithm are included, tested and applied in two fields. [ABSTRACT FROM AUTHOR]

Boson intensity correlations were examined to explore the fluid characterization produced in the collisions at the largest colliders and were perceived to have an astonishing curtailment during the computation of three-pion quantum interferences. Such analogous suppression can be probed to investigate the characteristics of particle production sources created during the collisions of heavy nuclei at unprecedented energies. We have demonstrated and analyzed the particle emissions from radiated sources with Bose–Einstein coherence that induces three-particle interferences to investigate the peculiarity of the particle emitted fluids. We are perspicacious that the bosons resemble the pertinent aspirant of coherence, and the normalized three-particle correlations evaluate the occurrence of such conglomerate fluid phases of chaotic and coherence significantly. Moreover, we also explored and analyzed the cumulant and the normalized correlations to examine the specific features of particle emission sources during the smashing of heavy nuclei. With such particular and pioneering approach, we have observed a consequential difference in the three-particle correlations and the normalized correlator at small temperature regimes. [ABSTRACT FROM AUTHOR]