Search

Quantum thermodynamics strives to extend classical thermodynamics and nonequilibrium statistical physics to ensembles of sizes below the thermodynamic limit with the full inclusion of quantum effects. This paper uses the nonrelativistic quantum mechanics of a lone system in a thermal bath to relate its wave function's local phase to Lorentz-Faraday forces acting thereon. In the intake of heat from its surroundings, such a system's entropy increases with the gain connected to the gradient field of its local phase whose subharmonicity within the boundary of its volume is a necessary and sufficient condition for it to comply with the second law of thermodynamics (SLT). The thermodynamic arrow of time necessitates irreversible over reversible processes as determined by the gradient field of the phase. Conservative Lorentz-Faraday forces identified herein impress on the system to engender irreversible (reversible) change and entropy gain (stasis) in its exchange of heat with its environment under the discernment of the thermodynamic arrow of time and regardless of the time-reversal symmetry of such venerable frameworks as electrodynamics and quantum mechanics. Entropy production is greatest when the local phase is subharmonic within the system's nominal volume. A means of time-averaging entropy and free energy changes under nonstandard-state conditions with the accommodation of phenomenological relaxation is provided. Both the SLT and Faraday's law of induction are of similar vintage and status. Surprisingly, they share a hitherto unrecognized connection at the microscopic level. Faraday's law of induction is shown to hold for a lone system provided the gradient of its local phase is finite, a necessary and sufficient condition for it not to present with its alleged paradoxes and contradictions despite its technological successes rivalling those of the SLT. There is no evidence to deny the successes of both the SLT and Faraday's law for science and technology. In compliance with Earnshaw's theorem, the potential of the Lorentz-Faraday force is shown to stabilize a lone system just like the Coulomb (or Newtonian) potential while continuing to fulfill the virial theorem. A consequence of the time asymmetry of entropy is the impossibility of travel to the past as to cause entropy changes to decrease contrary to the SLT. Further consequences of entropy's time asymmetry include at least the nonexistence of magnetic monopoles, the observed matter-antimatter asymmetry in leptonic and baryonic matter, and the role of axion-like particles in accounting for the absence of charge-parity violations in strong interactions without necessarily answering for dark matter. Within the range of validity of gravito(electro)magnetism, dark energy is identified as the work done by the Heaviside analog of the Lorentz-Faraday force in causing the accelerated expansion of the Universe without reference to either a finite cosmological constant or an unstable vacuum state transition. In the practice of reductionism, macroscopic physics supervenes upon the microscopic, the SLT being the most conspicuous exception to that superfluous tenet. The supersedence of classical thermodynamics over quantum mechanics and electrodynamics across spatio-temporal scales ranging from an individual quantized system to its known Universe has been shown herein. Additionally, in showing that reversible (irreversible) processes are affiliated with the particle (wave) behavior of matter, attention has been drawn to a heretofore overlooked connection between the different roles of classical thermodynamics and quantum mechanics and electrodynamics in respect to arrow-of-time asymmetry and wave-particle duality., 1 Introduction 1.1 Background and purpose Charge conjugation (C), parity (P), and time (T) are the three most important discrete symmetries and hold for all physical phenomena in Nature: C [...]

Quantum-computing devices can be more powerful than their classical counterparts, but controlling large quantum systems is difficult. Two studies report work that overcomes this challenge. Quantum-computing devices can be more powerful than their classical counterparts, but controlling large quantum systems is difficult. Two studies report work that overcomes this challenge., Author(s): Christine Muschik Author Affiliations: Large quantum systems tamed Predicting the behaviour of more than a few quantum particles is tricky. The problem is so difficult that, in general, it [...]

MACHINE LEARNING IMPROVES CATALYSTS In a new study, researchers at the University of Michigan used machine learning to predict how the compositions of metal alloys and metal oxides affect their [...]

In relativistic quantum field theory, information propagation is bounded by the speed of light. No such limit exists in the nonrelativistic case, although in real physical systems, short-range interactions may be expected to restrict the propagation of information to finite velocities. The question of how fast correlations can spread in quantum many-body systems has been long studied1. The existence of a maximal velocity, known as the Lieb-Robinson bound, has been shown theoretically to exist in several interacting many-body systems (for example, spins on a lattice (2-5))--such systems can be regarded as exhibiting an effective light cone that bounds the propagation speed of correlations. The existence of such a 'speed of light' has profound implications for condensed matter physics and quantum information, but has not been observed experimentally. Here we report the time-resolved detection of propagating correlations in an interacting quantum many-body system. By quenching a one-dimensional quantum gas in an optical lattice, we reveal how quasiparticle pairs transport correlations with a finite velocity across the system, resulting in an effective light cone for the quantum dynamics. Our results open perspectives for understanding the relaxation of closed quantum systems far from equilibrium (6), and for engineering the efficient quantum channels necessary for fast quantum computations (7)., Lieb-Robinson bounds have already found a number of fundamental applications (8,9). For example, they enable a rigorous proof of a longstanding conjecture that linked the presence of a spectral gap [...]

Using quantum simulation techniques based on either density functional theory or quantum Monte Carlo, we find clear evidence of a first-order transition in liquid hydrogen, between a low conductivity molecular state and a high conductivity atomic state. Using the temperature dependence of the discontinuity in the electronic conductivity, we estimate the critical point of the transition at temperatures near 2,000 K and pressures near 120 GPa. Furthermore, we have determined the melting curve of molecular hydrogen up to pressures of 200 GPa, finding a reentrant melting line. The melting line crosses the metalization line at 700 K and 220 GPa using density functional energetics and at 550 K and 290 GPa using quantum Monte Carlo energetics. phase transition | quantum Monte Carlo | density functional theory | plasma phase transition | melting doi/ 10.1073/pnas.1007309107

A quasi-linear two-layer quasigeostrophic [beta]-plane model of the interaction between a baroclinic jet and a single zonal wavenumber perturbation is used to study the mechanics leading to a wave amplitude bifurcation--in particular, the role of the critical surfaces in the upper-tropospheric jet flanks. The jet is forced by Newtonian heating toward a radiative equilibrium state, and Ekman damping is applied at the surface. When the typical horizontal scale is approximately the Rossby radius of deformation, the waves equilibrate at a finite amplitude that is comparable to the mean flow. This state is obtained as a result of a wave-induced temporary destabilization of the mean flow, during which the waves grow to their finite-equilibrium amplitude. When the typical horizontal scale is wider, the model also supports a state in which the waves equilibrate at negligible amplitudes. The transition from small to finite-amplitude waves, which occurs at weak instabilities, is abrupt as the parameters of the system are gradually varied, and in a certain range of parameter values both equilibrated states are supported. The simple two-layer quasi-linear setting of the model allows a detailed examination of the temporary destabilization process inherent in the large-amplitude equilibration. As the waves grow they reduce the baroclinic growth by reducing the vertical shear of the mean flow, and reduce the barotropic decay by reducing the mean potential vorticity gradient at the inner sides of the upper-layer critical levels. Temporary destabilization occurs when the reduction in barotropic decay is larger than the reduction in baroclinic growth, leading to a larger total growth rate. Ekman friction and radiative damping are found to play a major role in sustaining the vertical shear of the mean flow and enabling the baroclinic growth to continue. By controlling the mean flow potential vorticity gradient near the critical level, the model evolution can be changed from one type of equilibration to the other. DOI: 10.1175/2009JAS3157.1

Diffraction methods indicate clearly that there are two crystallographic Al sites in kaolinite with different site symmetry. Many unsuccessful attempts have been made to resolve the two different Al sites in kaolinite by magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy since the early 1980s. This study attempts to resolve these sites, derive accurate quadrupolar coupling parameters at the two sites, and explain the reasons for the lack of separation by combining NMR spectroscopy at various fields with ab initio quantum modeling. At a high field such as 21.06 T, large chemical shift anisotropy and dipolar effects can overwhelm the quadrupolar interaction effects for sites with relatively small [C.sub.q] values such as the two Al sites in kaolinite. The spectra will then display featureless lineshapes lacking the typical quadrupolar interaction characteristics. At lower fields, such as 4.68 T, the quadrupolar interaction effects become dominant, but due to the similarity of the two Al environments in kaolinite, as well as broadening by residual dipole-dipole and chemical shift anisotropy, the [sup.27]Al MAS NMR peaks still could not be separated. To resolve the two different AI sites spectroscopically, [sup.27]Al MAS NMR experiments at multiple magnetic fields, satellite transition NMR, and multiple-quantum MAS techniques have been utilized. Although these NMR experiments failed to resolve the two Al sites, the spectra have been interpreted with the aid of theoretical ab initio quantum mechanical modeling using full potential linearized augmented plane wave (FP-LAPW) model and the CASTEP software program. Average values of [C.sub.q], [eta], and [[delta].sub.iSO] for the two Al sites were constrained to be 2.6 MHz, 0.75 and 6.25 ppm with high confidence. Keywords: Kaolinite, [sup.27]Al MAS NMR, multiple-quantum MAS, satellite transition NMR, multiple magnetic fields, FP-LAPW modeling, CASTEP, quadrupolar interaction parameters

This perspective discusses progress in the theory of bimolecular reaction dynamics in the gas phase. The examples selected show that definitive quantum dynamical compuetations are providing insights into the detailed mechanisms of chemical reactions. chemical reactions | quantum chemistry | quantum dynamics

A theoretical framework for understanding urban environments and the implementation of urban transformation programs based on quantum physics is described. This framework is presented as an alternative to the fragmentary perspective in the discussion of urban social policies.

Byline: Wen Chen (Institute of Soft Matter Mechanics, Department of Engineering Mechanics, Hohai University, No. 1 Xikang Road, Nanjing City, Jiangsu Province 210098, China, chenwen@hhu.edu.cn) Keywords: fractional calculus; soft matter; [...]

Several 3-D simulations are conducted to study the effects of a fringing electric field on the performance and structural optimization of the FinFET devices. The spacer width, fin width and several other device features are shown to be highly affected by the strength of the fringing field.

The mechanism of the hydrolysis reaction is examined using a quantum mechanical computational model within the phosphodiesterase superfamily of enzymes (PDE) catalytic site. The results provide new insight that the PDE4 hydrolysis of adenosine 3',5'-cyclic monophosphate (cAMP) is a five step process.

We explore Yang's Noncommutative space-time algebra (involving two length scales) within the context of QM defined in Noncommutative spacetimes and the holographic area-coordinates algebra in Clifford spaces. Casimir invariant wave [...]

Abstract: We present calculations for a nonplanar double box with four massless, massive external, and internal legs propagators. The results are expressed for arbitrary exponents of propagators and dimension in [...]

This article shows, Synge-Weber's classical problem statement about two particles interacting by a signal can be reduced to the case where the same particle is located in two different points [...]

The modeling of the electronic characteristics of semiconductor devices based on Schottky contacts in low-dimensional systems is discussed. A quasi-two-dimensional quantum mechanical model is developed and validated.

Byline: Ramon Carbo-Dorca (1) Keywords: quantum QSPR; molecular similarity; non-linear QQSPR; stochastic similarity matrices; Jacobi rotations; variational QQSPR Abstract: The theoretical results presented in this work point out that quantitative structure--properties relationslips (QSPR) can be appropriately founded within the theoretical background of quantum mechanics. In this way, the deducible quantum QSPR (QQSPR) framework and the associated fundamental equation, furnish with a causal backup the structure--properties relationships old problem. Moreover, they also provide algorithms to obtain in a general manner, up to any approximation level and even from a variational point of view, unbiased and universal causal QSPR models for any chosen quantum object set. Author Affiliation: (1) Institut de Quimica Computacional, Universitat de Girona, Girona, 17071, Catalonia, Spain Article History: Registration Date: 27/10/2004

It has proven difficult to describe the kinematics in irregular waves satisfactorily, in particular for the surface zone in broad-banded waves. A Lagrangian approach offers distinct advantages in this respect, eliminating the need for extrapolation of solutions or 'stretching' of coordinates. This paper presents a model of irregular waves based on superposition of linear Lagrangian wave components, using an iterative method to obtain the Eulerian solution. This approach yields theoretically consistent results everywhere in the waves, and comparisons with wave flume measurements show good agreement. Also, the linear Lagrangian model includes wave interactions that would be nonlinear in an Eulerian formulation. [DOI: 10.1115/1.1554702]

The wave solutions discovered by Rossby are of fundamental importance for atmospheric dynamics. The nonlinear interactions between these waves determine the primary characteristics of the energy spectrum. These interactions take place between triplets of waves known as 'resonant triads' and, for a small amplitude, they are described by the three-wave equations. These same equations also govern the dynamics of a simple mechanical system, the elastic pendulum or swinging spring. This equivalence allows us to deduce properties, not otherwise evident, of resonant triads from the behavior of the mechanical system. In particular, the characteristic stepwise precession of the swing plane, so obvious from observation of the physical spring pendulum, is also found for the Rossby triads. This phenomenon has not been previously noted and is an example of the insight coming from the mathematical equivalence of the two systems. The implications of the precession for predictability of atmospheric motions are considered. The pattern of breakdown of unstable Rossby waves is very sensitive to unobservable details of the perturbations, making accurate prediction very difficult.

Josephson effects are macroscopic quantum phenomena that can be understood at the undergraduate level with the help of mechanical analogs. Although Josephson junctions in zero magnetic field can be modeled by pendulum analogs, a simple mechanical model of Josephson junctions in nonzero fields has been elusive. We demonstrate how the magnetic field dependence of the maximum Josephson current can be visualized by the analogs of a set of interconnected pendula attached to pulleys. [DOI: 10.1119/1.1533052]

The use of a total time derivative of operators, that depends on the time evolution of the wave function as well as on any intrinsic time dependence in the operators, simplifies the formal development of quantum mechanics and allows its development to more closely follow the corresponding development of classical mechanics. We illustrate the use of the total time derivative for a free particle, the linear potential, the harmonic oscillator, and the repulsive inverse square potential. In these cases, operators whose total time derivative is zero can be found and yield general properties of wave packets and several useful time-dependent solutions of Schrodinger's equation, including the propagator. [DOI: 10.1119/1.1531579]

We present an efficient and accurate continuum-mechanics approach to predict the elastic fields in multilayered semiconductors due to buried quantum dots (QDs). Our approach is based on a novel Green's function solution in anisotropic and linearly elastic multilayers, derived within the framework of generalized Stroh formalism and Fourier transforms, in conjunction with the Betti's reciprocal theorem. By using this approach, the induced elastic fields due to QDs with general misfit strains are expressed as a volume integral over the QDs domains. For QDs with uniform misfit strains, the volume integral involved is reduced to a surface integral over the QDs boundaries. Further, for QDs that can be modeled as point sources, the induced elastic fields are then derived as a sum of the point-force Green's functions. In the last case, the solution of the QD-induced elastic field is analytical, involving no numerical integration, except for the evaluation of the Green's functions. As numerical examples, we have studied a multilayered semiconductor system of QDs made of alternating GaAs-spacer and InAs-wetting layers on a GaAs substrate, plus a freshly deposited InAs-wetting layer on the top. The effects of vertical and horizontal arrays of QDs and of thickness of the top wetting layer on the QD-induced elastic fields are examined and some new features are observed that may be of interest to the designers of semiconductor QD superlattices. DOI: 10.1115/1.1544540]

This paper derives a mathematical model for the hysteresis characteristics of spin-ferromagnetic materials on a quantum-mechanical basis. For a given material, the model provides a link between the micromagnetic behavior at the atomic/domain levels and the details of the scalar hysteresis loop at the macroscopic level. Physical input parameters of the model consist of the Curie temperature, the sample temperature, the saturation magnetization, and the intrinsic coercivity. The parameters of the mathematical model are the reduced temperature t, the Weiss coefficient [alpha] a new quantity called the domain coefficient [beta], and a single pinning coefficient [gamma] that defines the anhysteretic magnetization. Quantitative agreement with the measured hysteresis data of a wide range of materials, including temperature dependence, is good. The model is valid for materials with intrinsic coercivities ranging over 6 orders of magnitude. Index Terms--Anhysteresis, coercivity, Curie temperature, domain size, ferromagnetic, hysteresis, Langevin function, magnetization, magneton, paramagnetic, susceptibility.

A linear theory is developed to obtain the motions of a two-dimensional, freely floating body (from which steady intake/discharge flows originate) that encounters incoming waves. The boundary-value problem is formulated within the assumptions of linear potential theory by decomposing the total potential into its oscillatory and steady components. The steady potential is further decomposed into the double-model and perturbation potentials. The time-harmonic potential is coupled with the steady potential through the free-surface condition. The potentials are obtained by use of the quadratic boundary-element method based on the Rankine source. The effect of the steady intake/discharge flows on the diffraction loads, hydrodynamic force coefficients, as well as the motions of a two-dimensional prismatic body floating on the free surface are presented. It is shown that the exciting wave forces and the hydrodynamic coefficients other than the damping coefficients are not appreciably affected in the case of low intake/discharge Froude numbers that are estimated, for example, for a 100 MW floating OTEC plant. [DOI: 10.1115/1.1537724]

In many offshore locations, storm generated steep waves are common and the survival of offshore structures in their presence is an important design condition. The design environment in depth-limited waters often includes waves of breaking and near-breaking conditions, in which currents may be present. Experiments were carried out in a wave tank with simulated steep waves with and without steady in-line current in which the wave profiles and the corresponding kinematics were simultaneously measured. The waves included both regular and random waves and often approached the breaking wave height for the water depth. These waves were analyzed by higher-order wave theory. In particular, the regular waves were simulated by the regular and irregular stream function theory. Especially steep wave profiles within the random waves were computed using the irregular stream function theory. The theory allows inclusion of steady current in its formulation for computation of wave kinematics. The correlation of the measured wave kinematics with the higher-order stream function wave theory showed that the wave theory could predict the kinematics of these steep waves (with and without the presence of current) well. However, in breaking waves, the vertical water particle velocity was not predicted well, especially near the trough. The effect of breaking and near-breaking steep waves on a fixed vertical caisson was also studied. The forces measured on the vertical caisson from the wave tank testing were analyzed to determine the effect of these waves and currents on the forces. It was found that the measured forces (and overturning moments) on the caisson model matched fairly well by the proper choice of force coefficients from the design guideline and the nonlinear stream function theory of appropriate order. [DOI: 10.1115/1.1556403]

The authors propose that the body force that accompanies wave breaking is potentially an important linear mechanism for generating secondary waves that propagate into the mesosphere and lower thermosphere. While the focus of this paper is on 3D forcings, it is shown that this generating mechanism can explain some of the mean wind and secondary wave features generated from wave breaking in a 2D nonlinear model study. Deep 3D body forces, which generate secondary waves very efficiently, create high-frequency waves with large vertical wavelengths that possess large momentum fluxes. The efficiency of this forcing is independent of latitude. However, the spatial and temporal variability/intermittency of a body force is important in determining the properties and associated momentum fluxes of the secondary waves. High spatial and temporal variability accompanying a wave breaking process leads to large secondary wave momentum fluxes. If a body force varies slowly with time, negligible secondary wave fluxes result. Spatial variability is important because distributing 'averaged' body forces over larger regions horizontally (as is often necessary in GCM models) results in waves with smaller frequencies, larger horizontal wavelengths, and smaller associated momentum fluxes than would otherwise result. Because some of the secondary waves emitted from localized body force regions have large vertical wavelengths and large intrinsic phase speeds, the authors anticipate that secondary wave radiation from wave breaking in the mesosphere may play a significant role in the momentum budget well into the thermosphere.

A 3D numerical solution was derived to determine the wave field in a physical wave tank equipped with a porous wave absorber of variable width and draft. The solution was achieved by applying the boundary element method. The model was applied to analyze the effect of the geometry and material of wave absorbers on wave reflection to eventually equip a wave tank with a proper wave absorber. The results show that absorber geometry has a complex, often surprising and nonintuitive effect on wave reflection. A more pronounced effect on wave reflection possesses physical and hydraulic properties of the material used to build a wave absorber. A reduction of wave reflection can usually be achieved by increasing absorber length and simultaneously decreasing its slope, and often a reduction of wave reflection can be achieved by increasing absorber draft or width. Moreover, a reduction of wave reflection, often substantial, can be achieved by increasing porosity and the damping coefficient. The results and additional analysis show that a reasonable wave reflection level can already be achieved for fairly short absorbers, and the model can be applied to select an optimal wave absorber for any prespecified conditions. Theoretical results are in reasonable agreement with experimental data. CE Database keywords: Numerical models; Wave generation; Absorbers; Wave tanks.

Quantum trajectory theory, developed largely in the quantum optics community to describe open quantum systems subjected to continuous monitoring, has applications in many areas of quantum physics. I present a simple model, using two-level quantum systems (q-bits), to illustrate the essential physics of quantum trajectories and how different monitoring schemes correspond to different 'unravelings' of a mixed state master equation. I also comment briefly on the relationship of the theory to the consistent histories formalism and to spontaneous collapse models. [DOI: 10.1119/1.1475328]

For the first time, a physics based computational model has been used to provide a direct description of the effects of the traveling wave tube (TWT) on modulated digital signals. The TWT model comprehensively takes into account the effects of frequency dependent AM/AM and AM/PM conversion, gain and phase ripple, drive-induced oscillations, harmonic generation, intermodulation products, and backward waves. Thus, signal integrity can be investigated in the presence of these sources of potential distortion as a function of the physical geometry of the high-power amplifier and the operational digital signal. This method promises superior predictive fidelity compared to methods using TWT models based on swept-amplitude and/or swept-frequency data. The fully three-dimensional (3-D) time-dependent, TWT interaction model using the electromagnetic code MAFIA is presented. This model is used to investigate assumptions made in conventional TWT black-box models used in communication system level simulations. To quantitatively demonstrate the effects these approximations have on digital signal performance predictions, including intersymbol interference, direct digital data input into the MAFIA model is compared to the system level analysis tool, SPW, which incorporates these approximations. Index Terms--Helix, high-power amplifier, intersymbol interference, MAFIA, nonlinear model, PIC code, SPW, traveling wave tube amplifier.

We discuss counterintuitive aspects of probabilities for systems of identical particles obeying quantum statistics. Quantum coins and children (two level systems) and quantum dice (many level systems) are used as examples. It is emphasized that, even in the absence of interactions, (anti)symmetrizations of multiparticle wave functions destroy statistical independences and often lead to dramatic departures from our intuitive expectations.

Undergraduate students of chemistry can learn about quantum mechanics and the variational principle from the particle-in-a-box (PIB)-problem solution. The approximate wave functions for ground and excited states are expanded in terms of a basis of monomials. The secular determinant and related equations can be solved easily by use of Mathematica or Maple programs to compare the calculated energies and wave functions for basis set expansions of increasing size. The analysis can also be useful as a model for the procedural basis for understanding solution of more advanced electronic structure calculations. A different model of the PIB system is introduced. It makes possible construction of excited state wave functions from suitably signed/scaled segmented functions built from a model ground state wave function, a piecewise wave function.

Abstract: In a previous paper, the author proposed a quantum mechanical interaction that would insure that the evolution of subjective states would parallel the evolution of biological states, as required by von Neumann's theory of measurement. The particular model for this interaction suggested an experiment that the author has now performed with negative results. A modified model is outlined in this paper that preserves the desirable features of the original model, and is consistent with the experimental results. This model will be more difficult to verify. However, some strategies are suggested. Article History: Registration Date: 08/10/2004