共查询到20条相似文献,搜索用时 62 毫秒
1.
David Ruelle 《Journal of statistical physics》1997,86(5-6):935-951
We study nonequilibrium statistical mechanics in the presence of a thermostat acting by random forces, and propose a formula for the rate of entropy productione() in a state . When is a natural nonequilibrium steady state we show thate()0, and sometimes we can provee()>0. 相似文献
2.
Shahen Hacyan 《General Relativity and Gravitation》1994,26(1):85-96
The Dirac spinors and matrices are used in combination with the Arnowitt-Deser-Misner formalism in order to obtain yet another formulation of Hamiltonian general relativity, together with a new form of the Gauss-Codazzi equations. The relation with Ashtekar's variables is analyzed; it is shown, for instance, that the matrices are equivalent to the electric field variable. The electric and magnetic decomposition of the gravitational field is also studie using Dirac matrices. 相似文献
3.
A. V. Akimov A. V. Sokolov N. N. Kolachevsky A. N. Matveev V. N. Sorokin S. I. Kanorsky 《Journal of Russian Laser Research》2003,24(2):129-142
Dark resonances in the 154Sm -system 4f
66s
2(7
F
0) 4f
66s6p(9
F
1
0) 4f
6
s
2(7
F
1) are observed alongside the velocity selective optical pumping. The shape of the resulting spectra strongly depended on the buffer gas (He, Ar) pressure due to velocity-changing collisions (VCC): the sign of the effect could be reversed from the dark to the bright resonance. The observed spectra are interpreted within the framework of the hard-sphere collision model. The role of VCC in the formation of the dark state in the -system is discussed. 相似文献
4.
The exact analytic result is obtained for the Fourier transform of the generating functionF(R,s)=
n=0
s
n
P(R,n), whereP(R,n) is the probability density for the end-to-end distanceR inn steps of a random walk with persistence. The moments R
2(n), R
4(n), and R
6(n) are calculated and approximate results forP(R,n) and R
–1(n) are given. 相似文献
5.
A natural model of a discrete random surface lying above a two-dimensional substrate is presented and analyzed. An identification of the level curves of the surface with the Peierls contours of Ising spin configurations leads to an exactly solvable free energy, with logarithmically divergent specific heat. The thermodynamic critical point is shown to be a wetting transition at which the surface height diverges. This is so even though the surface has no downward fingers and hence no entropic repulsion from the substrate.Dedicated to Roland DobrushinResearch supported in part by NSF Grant No. DMS-8514834 and AFOSR Contract No. F49620-86-C0130 under the U.R.I. program 相似文献
6.
R. Lang 《Communications in Mathematical Physics》1979,65(2):129-149
We consider gradient systems of infinitely many particles in one-dimensional space interacting via a positive invariant pair potential with a hard core. The main assumption is that is strictly convex within the rangeR of (whereR is a fixed number ). Under some technical conditions we prove the following theorems: Let the initial distribution be given by a translation invariant point process onR
1. Then there exists only one extreme equilibrium state with a given intensityI() satisfyingI()R
–1, and all ergodic initial distributions with an intensityI()R
–1 converge weakly ast to the extreme equilibrium state with the same intensity. 相似文献
7.
Eugene P. Gross 《Journal of statistical physics》1989,54(1-2):429-436
The phase transition for a spin in a magnetic fieldB coupled to acoustic phonons by a coupling constant is studied. The caseB1 with an upper cutoff of unity for the phonons is studied systematically by using an adiabatic canonical transformation. In leading order the transition line is at =2/B=1. In the normal phase (<1) the ground-state energy is –B/2 plus a function of that is given explicitly as the solution of a pair theory. In the broken symmetry phase (>1) the energy is the classical energy plus the same function of =1/2. It is found that the first derivatives of the energy with respect to and with respect toB have finite jumps across the transition line. Quantum fluctuations in both phases are treated. Higher-order terms are a series of powers of 1/B times functions of . The case of a small transverse fieldB is also studied. The sharp transition disappears and is replaced by rapid variation in a region of order (B1/B)2/3 about =1. 相似文献
8.
The density of Yang-Lee zeros in the thermodynamic limit is discussed for ferromagnetic spherical models of general dimensionalities and arbitrary range of interaction. In all cases the zeros lie on the imaginary axis in the complex magnetic field planeH=H+iH with a density (H) that exhibits a square root singularity(H)
(H-H
0), with=1/2, as the edge of the gap atH=H
0(T) is approached forT>T
c. WhenTT
c one hasH
0(T)(TT
c
) with critical exponent=+.Supported by the National Science Foundation in part through the Materials Science Center at Cornell University. 相似文献
9.
In this paper we concern ourselves with the small asymptotics of the inner products of the eigenfunctions of a Schrödinger-type operator with a coherent state. More precisely, let
j
and E
j
denote the eigenfunctions and eigenvalues of a Schrödinger-type operator H
with discrete spectrum. Let (x,) be a coherent state centered at the point (x, ) in phase space. We estimate as 0 the averages of the squares of the inner products (
a
(x,)
,
j
) over an energy interval of size around a fixed energy, E. This follows from asymptotic expansions of the form for certain test function and Schwartz amplitudes a of the coherent state. We compute the leading coefficient in the expansion, which depends on whether the classical trajectory through (x, ) is periodic or not. In the periodic case the iterates of the trajectory contribute to the leading coefficient. We also discuss the case of the Laplacian on a compact Riemannian manifold.Research supported in part by NSF grant DMS-9303778 相似文献
10.
R. Gerber 《Czechoslovak Journal of Physics》1969,19(4):494-502
The paper presents an estimate of the magnitude of additional torsion of magnetostatic origin, and sets forth the conditions determining its periodicity in a homogeneous and an inhomogeneous magnetic field.It further deals with the eifect of inaccurate specimen orientation on the determination of coefficientsF andG and finds the following: If is the error of orientation of the plane of measurement, the error ofF measurement is [2F+G] sin2
and the error of (1/2)G measurement is [F}+(1/2)G] sin2
at most. If is the error of the setting of the direction of measurement or annealing, the maximum error ofF measurement is [–F±(1/2)G] sin2 2, and that of (1/2)G measurement is [–(1/2)G±F] sin2 2].In conclusion, the author wishes to express his thanks to Dr. J. ternberk CSc. for his valuable discussion and comments on this paper. 相似文献
11.
The CPA d. c. electrical conductivity for a bcc based random binary substitutional alloy with long range ordering is determined for a single band model with diagonal disorder and arbitrary alloy parameters. The CPA vertex corrections to vanish, off-diagonal elements of the Green function are most important. The conductivity obeys general symmetries with respect to alloy parameters and can be brought to closed form resembling the standard expression = ne2/m. To interpret various terms in correctly, limits with available Boltzmann equation solutions are analyzed in detail. 相似文献
12.
Yaakov Rosenfeld 《Journal of statistical physics》1984,37(1-2):215-236
The thermodynamic properties of the mean spherical (MSA), Percus-Yevick (PY), and hypernetted-chain (HNC) approximations are derived by a simple and unified approach by considering the RPA free-energy functionalF and employing an Ewald-type identity. It is demonstrated that with decreasing relative contribution of the hard-core insertion to the thermodynamic functions, the MSA changes its nature from PY-like to HNC-like, withF changing its role from excess pressure to excess free energy, respectively. It is found that the condition of continuity of the MSA pair functions is equivalent to a stationarity condition forF and leads to thermodynamic consistency between the virial and energy equations of state for the (thus defined) soft-MSA (SMSA), withF playing the role of the excess free energy. It is shown that the PY-compressibility and virial equations of state forD-dimensional hard spheres may be simply obtained one from the other without knowing any details of the solution of the model. Using this relation we find an indication that the PY approximation for hard spheres becomes less accurate with increasing dimensionality. A general variational formulation is presented for the application of the MSA for soft potentials, and results for the one-component plasma are discussed and extended.On sabbatical leave from the Nuclear Research Center-Negev, P.O. Box 9001, Beer Sheva, Israel. 相似文献
13.
F. Šimkovic 《Czechoslovak Journal of Physics》2002,52(4):607-614
The neutrinoless double-beta decay (0 decay) to the first excited 0+ collective final state is examined for A = 76, 82, 100 and 136 nuclei by assuming light Majorana neutrino exchange mechanism. Realistic calculations of nuclear matrix elements are performed within the renormalized Quasiparticle Random Phase Approximation. Transitions to the first excited two-quadrupole phonon 0+ state are described within a boson expansion formalism. It is found that the 100Mo is a good candidate for experimental study of the 0 decay to excited 0+ state due to small suppression of this transition relative to the transition to the ground state. 相似文献
14.
David Ruelle 《Journal of statistical physics》1996,85(1-2):1-23
We analyze different mechanisms of entropy production in statistical mechanics, and propose formulas for the entropy production ratee() in a state . When is steady state describing the long term behavior of a system we show thate()0, and sometimes we can provee()>0. 相似文献
15.
In the framework of the Nilsson model the calculations of the so called shape factor for the first forbidden
– transitions 5/2+
241Pu 5/2–
241Am and 7/2+
177Lu 7/2–
177Hf are carried out. The dependence on the Nilsson potential parameters is studied. It turns out that for the transitions considered the calculated shape factor depends linearly on the electron energy and its slope is 10–3 per 20 keV. This can affect the analysis of electron spectra if the endpoint energy is sufficiently large. 相似文献
16.
For theq-deformed canonical commutation relationsa(f)a
(g)=(1-q)f,g 1+qa
(g)a(f) forf, g in some Hilbert space we consider representations generated from a vector satisfyinga(f)=<f, >, where . We show that such a representation exists if and only if 1. Moreover, for <1 these representations are unitarily equivalent to the Fock representation (obtained for =0). On the other hand representations obtained for different unit vectors are disjoint. We show that the universal C*-algebra for the relations has a largest proper, closed, two-sided ideal. The quotient by this ideal is a naturalq-analogue of the Cuntz algebra (obtained forq=0). We discuss the conjecture that, ford<, this analogue should, in fact, be equal to the Cuntz algebra itself. In the limiting casesq=±1 we determine all irreducible representations of the relations, and characterize those which can be obtained via coherent states.Supported in part by the NSF(USA), and NATO
Available by anonymous FTPfrom nostrom.physik.Uni-Osnabrueck.DE 相似文献
17.
Luo Liguo Nie Dezhen Chen Jishu 《International Journal of Infrared and Millimeter Waves》1993,14(1):35-45
The paper analyses steady states of optically pumped sub-millimeter laser on resonance. The steady state of (=0, ) gives three unstable regions. The steady state curve of ( 0,) varies much by choosing media with different damping rates of the corresponding variables, Gp/Kp and Ga/Ka. 相似文献
18.
Matsuta K. Minamisono T. Tanigaki M. Fukuda M. Nojiri Y. Mihara M. Onishi T. Yamaguchi T. Harada A. Sasaki M. Miyake T. Minamisono K. Fukao T. Sato K. Matsumoto Y. Ohtsubo T. Fukuda S. Momota S. Yoshida K. Ozawa A. Kobayashi T. Tanihata I. Alonso J. R. Krebs G. F. Symons T. J. M. 《Hyperfine Interactions》1996,97(1):519-526
The magnetic moments of the proton drip-line nuclei13O(I
= 3/2–,T
1/2 = 8.6 ms) and 9C(I
= 3/2–,T
1/2 = 126 ms) have been determined for the first time through the combined techniques of polarized radioactive nuclear beams and-NMR detection. The observed magnetic moments are ¦(13O)¦ = 1.3891 ±0.0003
N and ¦(9C)¦ = 1.3914 ±0.0005
N. Spin expectation values are deduced to be 0.76 and 1.44 for13O and9C, respectively. While the of13O is consistent with the systematics from isospinT= 1/2 mirror pairs, the of9C is unusually large, even far larger than the single particle value, = 1. 相似文献
19.
Simba A. Mutangadura 《Communications in Mathematical Physics》1990,132(3):581-592
Let be an infinite dimensional Hilbert space and () the set of all (orthogonal) projections on . A comparative probability on () is a linear preorder on () such thatOP1,1O and such that ifP┴R,Q┴R, thenPQP+RQ+R for allP, Q, R in (). We give a sufficient and necessary condition for to be implemented in a canonical way by a normal state onB(), the bounded linear operators on . 相似文献
20.
Rates of particle-emitting decay of the resonant state of the muonic molecular ion (dHe)
J=1 lying below the (d)1s-He threshold can decay to the d-He scattering state. The resonant state is estimated by scattering calculations with the non-adiabatic coupled-rearrangement-channel method. Strong isotope dependence of the decay rates of (d3He)
J=1 and (d4He)
J=1 is predicted, though the calculated radiative decay rates of the states are almost the same. In (d3He)
J=1, the particle decay width is three times larger than the radiative decay width, while the two types of decay widths are almost the same in (d4He)
J=1. This results in a strong hindrance of the branching ratio of the radiative decay of (d3He)
J=1 compared with the case of (d4He)
J=1. This is consistent with a recent observation of the radiative decay of the two molecular states. 相似文献