共查询到20条相似文献,搜索用时 15 毫秒
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Josef-Maria Jauch 《Foundations of Physics》1975,5(1):111-132
A new axiomatic treatment of equilibrium thermodynamics—thermostatics—is presented. The equilibrium states of a thermal system are assumed to be represented by a differentiable manifold of dimensionn + 1 (n finite). The empirical temperature is defined by the notion of thermal equilibrium. Empirical entropy is shown to exist for all systems with the property that the total work delivered along closed adiabats is zero. Absolute entropy and temperature follow from the additivity of heat and energy for two separate systems in thermal equilibrium considered as a whole. The absolute temperature is defined up to a multiplicative constant. The exterior differentiable calculus of Cartan is introduced and in a subsequent paper its use for the derivation of standard results in thermostatics will be explained. 相似文献
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We introduce an integrable isochronous system and perturb its frequency by an external-deterministic or purely random-noise. Under the perturbation the action variable evolves in time: the corresponding diffusion coefficient is exactly computed and its dependence on the magnitude of the perturbation is carefully investigated. Different behaviors are found and justified: the quasilinear approximation, the superlinear regime, and the ballistic motion. 相似文献
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We analyze the motion of individual beads of a polymer chain using a discrete version of De Gennes' reptation model that describes the motion of a polymer through an ordered lattice of obstacles. The motion within the tube can be evaluated rigorously; tube renewal is taken into account in an approximation motivated by random walk theory. We find microstructure effects to be present for remarkably large times and long chains, affecting essentially all present-day computer experiments. The various asymptotic power laws commonly considered as typical for reptation hold only for extremely long chains. Furthermore, for an arbitrary segment even in a very long chain, we find a rich variety of fairly broad crossovers, which for practicably accessible chain lengths overlap and smear out the asymptotic power laws. Our analysis suggests observables specifically adapted to distinguish reptation from motions dominated by disorder of the environment. 相似文献
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Albert Reiner 《Journal of statistical physics》2005,118(5-6):1107-1127
In its customary formulation for one-component fluids, the Hierarchical Reference Theory yields a quasilinear partial differential equation (PDE) for an auxiliary quantity f that can be solved even arbitrarily close to the critical point, reproduces non-trivial scaling laws at the critical singularity, and directly locates the binodal without the need for a Maxwell construction. In the present contribution we present a systematic exploration of the possible types of behavior of the PDE\ for thermodynamic states of diverging isothermal compressibility T as the renormalization group theoretical momentum cutoff approaches zero. By purely analytical means we identify three classes of asymptotic solutions compatible with infinite T, characterized by uniform or slowly varying bounds on the curvature of f, by monotonicity of the build-up of diverging T, and by stiffness of the PDE in part of its domain, respectively. These scenarios are analzyed and discussed with respect to their numerical properties. A seeming contradiction between two of these alternatives and an asymptotic solution derived earlier [Parola et al., Phys. Rev. E 48:3321 (1993)] is easily resolved. 相似文献
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《Journal of Geometry and Physics》2005,55(1):50-74
The bosonic string theory evolved as an attempt to find a physical/quantum mechanical model capable of reproducing Euler’s beta function (Veneziano amplitude) and its multidimensional analogue. The multidimensional analogue of beta function was studied mathematically for some time from different angles by mathematicians such as Selberg, Weil and Deligne, among many others. The results of their studies apparently were not taken into account in physics literature on string theory. In a recent publication [IJMPA 19 (2004) 1655] an attempt was made to restore the missing links. The results of this publication are incomplete, however, since no attempts were made at reproduction of known spectra of both open an closed bosonic strings or at restoration of the underlying model(s) reproducing such spectra. Nevertheless, as discussed in this publication the existing mathematical interpretation of the multidimensional analogue of Euler’s beta function as one of the periods associated with the corresponding differential form “living” on the Fermat-type (hyper)surfaces, happens to be crucial for restoration of the quantum/statistical mechanical model reproducing such generalized beta function. Unlike the traditional formulations, this model is supersymmetric. Details leading to restoration of this model will be presented in the forthcoming Parts 2–4 of our work. They are devoted, respectively, to the group-theoretic, symplectic and combinatorial treatments of this model. In this paper the discussion is restricted mainly to the study of analytical properties of the multiparticle Veneziano and Veneziano-like (tachyon-free) amplitudes. In the last case, we demonstrate that the Veneziano-like amplitudes alone (with parameters adjusted accordingly) are capable of reproducing known spectra of both open and closed bosonic strings. The choice of parameters is subject to some constraints dictated by the mathematical interpretation of these amplitudes as periods of Fermat-type (hyper)surfaces considered as complex manifolds of Hodge-type. 相似文献
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Sedimentation equilibria of ferrofluids: I. Analytical centrifugation in ultrathin glass capillaries
Analytical centrifugation is used for the first time to measure sedimentation equilibrium concentration profiles of a ferrofluid, a concentrated colloidal dispersion of strongly absorbing magnetic nanoparticles. To keep the optical absorbance from becoming too strong, the optical path length is restricted to 50 μm by placing the dispersion in a flat glass capillary. The concentration profile is kept from becoming too steep, despite the relatively high buoyant mass of the nanoparticles, by making novel use of a low-velocity analytical centrifuge that was not designed to measure equilibrium profiles. The experimental approach is validated by comparison with profiles obtained using an analytical ultracentrifuge. At concentrations of a few hundred grams per liter, the osmotic pressures calculated from the equilibrium profiles are lower than expected for hard spheres or non-interacting particles, due to magnetic dipolar interactions. By following the presented experimental approach, it will now also be possible to characterize the interparticle interactions of other strongly absorbing colloidal particles not studied before by analytical centrifugation. 相似文献
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Klaus Krebs Markus P. Pfannmüller Birgit Wehefritz Haye Hinrichsen 《Journal of statistical physics》1995,78(5-6):1429-1470
We consider two single-species reaction-diffusion models on one-dimensional lattices of lengthL: the coagulation-decoagulation model and the annihilation model. For the coagulation model the system of differential equations describing the time evolution of the empty interval probabilities is derived for periodic as well as for open boundary conditions. This system of differential equations grows quadratically withL in the latter case. The equations are solved analytically and exact expressions for the concentration are derived. We investigate the finite-size behavior of the concentration and calculate the corresponding scaling functions and the leading corrections for both types of boundary conditions. We show that the scaling functions are independent of the initial conditions but do depend on the boundary conditions. A similarity transformation between the two models is derived and used to connect the corresponding scaling functions. 相似文献
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Optics and Spectroscopy - The problem of second-harmonic generation by a plane elliptically polarized electromagnetic wave from a thin optically nonlinear layer on the surface of a cylindrical... 相似文献
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The purpose of this paper is to study the solution of the celebrated
Whittaker equations by using analytical mechanics methods, including
the Lagrange--Noether method, Hamilton--Poisson method and potential
integral method. 相似文献
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M. Grelier F. Linot A. C. Lepage X. Begaud J. M. LeMener M. Soiron 《Applied Physics A: Materials Science & Processing》2011,103(3):805-808
AMC and EBG behaviors are respectively characterized by reflection phase method and dispersion diagram. A fast and simple
analytical model based on transmission line theory is proposed for each analysis. The validity of these analytical methods
is verified by a comparison between circuit representations, measurements and numerical results. 相似文献
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This literature review covers the applications of analytical techniques to solid phase organic chemistry and combinatorial chemistry published between June 96 and September 1997. Highlighted are mass spectrometry, NMR, IR and chromatographic analyses of solid phase synthesis reactions and combinatorial libraries. 相似文献
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The master equations system for rotational, vibrational and chemical kinetics in nonuniform gas flows with the sources is studied. Two approximate analytical methods of its solution for the arbitrary rate constants are developed for the case of the smooth distributions. The first method is based on the introduction of slow variables to the discrete equations. The second one uses WKB solution for diffusion approximation in Fokker-Planck form. The particular cases of harmonic and weakly anharmonic oscillators relaxation are examined. 相似文献
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In both quantum optics and cold atom physics, the behaviour of bosonic photons and atoms is often treated using phase space methods, where mode annihilation and creation operators are represented by c-number phase space variables, with the density operator equivalent to a distribution function of these variables. The anti-commutation rules for fermion annihilation, creation operators suggest the possibility of using anti-commuting Grassmann variables to represent these operators. However, in spite of the seminal work by Cahill and Glauber and a few applications, the use of Grassmann phase space methods in quantum–atom optics to treat fermionic systems is rather rare, though fermion coherent states using Grassmann variables are widely used in particle physics. 相似文献
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Summary This paper deals with the evaluation of a two-parameter, two-index, imaginary integral function
. The motivation for this analysis arose from the application of stochastic process theory to random ocean wave properties.
Physically
represents the normalized cross spectrum between any two components of a random state vector whose components are defined
by wave amplitude, vector particle velocity, vector particle acceleration and linearized vector hydrodynamic force on a submerged
object. The function
, however, is developed in a general fashion so as to be applicable to any two-dimensional random wave process. Numerical
and analytical methods are employed to develop techniques for the evaluation of
and sample graphs are presented.
Riassunto Si valuta la funzione integrale immaginaria a 2 parametri e 2 indici necessaria per l’applicazione della teoria dei processi stocastici alle proprietà delle onde oceaniche casuali. Fisicamente rappresenta lo spettro normalizzato incrociato preso fra due componenti qualsiasi di un vettore di stato casuale definito dall’ampiezza dell’onda, dal vettore velocità delle particelle, dal vettore accelerazione delle particelle e dal vettore linearizzato forza idrodinamica agente su un oggetto sommerso. La funzione è peraltro sviluppata in modo del tutto generale in modo da risultare applicabile a qualsiasi processo casuale ondoso in 2 dimensioni. Sono presentati metodi sia numerici che analitici, e grafici di esempio.
Резюме Эта работа посвящена вычислению двух-параметрической, двух-индексной, мнимой целой функции . Указанный анализ связан с применением теории стохастических процессов к изучению свойств случайных океанических волн. Физически представляет нормированный перекрестный спектр между двумя произвольными компонентами случайного вектора состояния, компоненты которого определяются амплитудой волны, вектором скорости частицы, вектором ускорения частицы и линеаризованной векторной гидродинамической силой, действующей на погруженный объект. Однако, функция вычисляется обычным образом для применения к произвольному двумерному случайному волновому процессу. Используются численные и аналитические методы для вычисления и предлагаются графики в качестве примера.相似文献
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In this work we give an algorithm to express as a convergent series the stationary averages for a class of gradient perturbations of a nonsymmetric (nongradient) Ornstein—Uhlenbeck process. The method relies on a cluster expansion in time of the Girsanov-Cameron-Martin formula for the density of the perturbed measure with respect to the Ornstein-Uhlenbeck measure. In the second paper of this series, the approach is extended to more general perturbations. 相似文献
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