Physics Reports最新文献

This report reviews recent progress in computing Kubo formulas for general interacting Hamiltonians. The aim is to calculate electric and thermal magneto-conductivities in strong scattering regimes where Boltzmann equation and Hall conductivity proxies exceed their validity. Three primary approaches are explained.

1. Degeneracy-projected polarization formulas for Hall-type conductivities, which substantially reduce the number of calculated current matrix elements. These expressions generalize the Berry curvature integral formulas to imperfect lattices.

2. Continued fraction representation of dynamical longitudinal conductivities. The calculations produce a set of thermodynamic averages, which can be controllably extrapolated using their mathematical relations to low and high frequency conductivity asymptotics.

3. Hall-type coefficients summation formulas, which are constructed from thermodynamic averages.

The thermodynamic formulas are derived in the operator Hilbert space formalism, which avoids the opacity and high computational cost of the Hamiltonian eigenspectrum. The coefficients can be obtained by well established imaginary-time Monte Carlo sampling, high temperature expansion, traces of operator products, and variational wavefunctions at low temperatures.

We demonstrate the power of approaches 1–3 by their application to well known models of lattice electrons and bosons. The calculations clarify the far-reaching influence of strong local interactions on the metallic transport near Mott insulators. Future directions for these approaches are discussed.

Since the emergent advent of miniaturized technologies in the last century, the past ninety years have witnessed the extensive use of micro- and nano-manipulation methods, which were promoted by the tremendous advances in fundamental physics as well as in techniques for sensing and actuating and in award-winning precision instrumentation. Micro- and nano-manipulation techniques imply the application of distinct physical laws at distinct spatial scales, and in turn enabled unprecedented progress in a significant number of scientific disciplines, particularly in the life sciences and its biomedical applications. Today, scientists have to cope with a series of issues that are inherently related to theory implementations at micro- and nanoscales, in the attempt to reveal the underlying principles that can enhance the capability of manipulating micrometer and nanometer-sized objects. Our report has the aim of giving an extensive review of the major results achieved in the study of micro- and nano-manipulation, by focusing on how fundamental physics (from robotic manipulation to magnetic, acoustic and optical fields, to electric and fluidic methods) is elaborated and leveraged to gather control over small objects, and how novel techniques are conceptually designed and practically implemented for important tool sets. We also summarize the representative applications in many disciplines over the past decades and discuss potential trends and open problems for future studies.

Electron–ion coupling is a fundamental process in nonequilibrium Warm Dense Matter. It also plays a central role in governing the states resulting from the interaction of high-intensity ultrafast lasers and free-electron-lasers with matter, an area that is of growing interest. Our inadequate understanding of the process was revealed in 1992 by the discovery of much weaker than expected electron–ion coupling in the nonequilibrium state at a shock front in Si where energy was transferred from hot ions to cold electrons. This necessarily raised questions about the behavior of electron–ion coupling in states with hot electrons and cold ions. It became a new focus of the field with the discovery of apparently constant electron–ion coupling in $fs$-laser heated Au, prompting a wide range of experimental and theoretical investigations of non-equilibrium warm dense Au as well as Cu for almost two decades. Fueling the pursuit were the findings of both constant and temperature-dependent coupling from subsequent experiments while the results of theoretical models were revealing reduced electron temperature dependence of electron–ion coupling. The goal of this review is to provide a concise historical account of the reported investigations, focussing on the salient characteristics of the experiments and models and how the diverse findings may be reconciled. Surprisingly, with alternative interpretations of some of the experimental results, a consistent behavior of weak electron–ion coupling has now emerged for $fs$-laser heated Au and Cu for electron temperature up to 20,000 K, corroborated by the evolution of theoretical predictions towards weak coupling. This is a significant progress. It will incentivize new research to gain further understanding of electron–ion coupling in nonequilibrium Warm Dense Matter.

The stability of ecological systems is a fundamental concept in ecology, which offers profound insights into species coexistence, biodiversity, and community persistence. In this article, we provide a systematic and comprehensive review on the theoretical frameworks for analyzing the stability of ecological systems. Notably, we survey various stability notions, including linear stability, sign stability, diagonal stability, D-stability, total stability, sector stability, and structural stability. For each of these stability notions, we examine necessary or sufficient conditions for achieving such stability and demonstrate the intricate interplay of these conditions on the network structures of ecological systems. We further discuss the stability of ecological systems with higher-order interactions.

Engines are systems and devices that convert one form of energy into another, typically into a more useful form that can perform work. In the classical setup, physical, chemical, and biological engines largely involve the conversion of heat into work. This energy conversion is at the core of thermodynamic laws and principles and is codified in textbook material. In the quantum regime, however, the principles of energy conversion become ambiguous, since quantum phenomena come into play. As with classical thermodynamics, fundamental principles can be explored through engines and refrigerators, but, in the quantum case, these devices are miniaturized and their operations involve uniquely quantum effects. Our work provides a broad overview of this active field of quantum engines and refrigerators, reviewing the latest theoretical proposals and experimental realizations. We cover myriad aspects of these devices, starting with the basic concepts of quantum analogs to the classical thermodynamic cycle and continuing with different quantum features of energy conversion that span many branches of quantum mechanics. These features include quantum fluctuations that become dominant in the microscale, non-thermal resources that fuel the engines, and the possibility of scaling up the working medium’s size, to account for collective phenomena in many-body heat engines. Furthermore, we review studies of quantum engines operating in the strong system–bath coupling regime and those that include non-Markovian phenomena. Recent advances in thermoelectric devices and quantum information perspectives, including quantum measurement and feedback in quantum engines, are also presented.

We survey on-shell and off-shell higher derivative supergravities in dimensions $1\le D\le 11$. Various approaches to their construction, including the Noether procedure, (harmonic) superspace, superform method, superconformal tensor calculus, $S$-matrix and dimensional reduction, are summarized. Primarily the bosonic parts of the invariants and the supertransformations of the fermionic fields are provided. The process of going on-shell, solutions to the Killing spinor equations, typical supersymmetric solutions, and the role of duality symmetries in the context of $R^4,D^4{R}^4$ and $D^6{R}^4$ invariants are reviewed.

As one of the representative patterns in nature and laboratory experiments, dendritic structures control the properties of a broad range of advanced materials. Dendrites arise during different phase and structural transformation processes. Generally, the formation of dendritic structures are stipulated by transport processes in bulk phases, together with thermodynamic properties and kinetic phenomena at the phase interfaces. The formation of a dendritic microstructure under the influence of external fields (electromagnetic and gravitational) is considered in this review. These fields involve the liquid and gaseous phases in a forced convective flow, causing the transfer of energy and matter in addition to the usual conductive (diffusion) transport. The formulated model takes into account rapid solidification from an undercooled liquid phase as well as intermediate and low growth velocities of dendritic crystals in pure one-component systems extended to binary mixtures and alloys. The areas of undercooling are identified, in which the influence of convection caused by the electromagnetic and/or gravitational field is most noticeable. The solidification regimes (from the diffusion-limited mode to the thermally and kinetically controlled mode) are reviewed in connection with the different liquid flow velocities that dictate various boundary conditions (conductive and convective) on the surface of growing crystals. A comparison of model predictions with experimental data and computational results provides the grounds for a discussion about the applicability of the formulated model to interpreting known and unexpected phenomena in the formation of a crystalline structure. By changing the power of the considered fields or reducing them almost to zero (for instance, in microgravity), it is possible to control the dispersion of a dendritic microstructure, as well as separate accompanying phases (eutectic, peritectic, monotectic, intermetallic phases, etc.) during the solidification of materials and, in the general case, during phase transformations.