共查询到20条相似文献,搜索用时 78 毫秒
1.
Alan D. Sokal 《Journal of statistical physics》1981,25(1):25-50
A variety of rigorous inequalities for critical exponents is proved. Most notable is the low-temperature Josephson inequalitydv +2 2–. Others are 1 1 +v, 1 1
, 1,d 1 + 1/ (for d),dv, 3 + (for d), 4 , and 2m 2m+2 (form 2). The hypotheses vary; all inequalities are true for the spin-1/2 Ising model with nearest-neighbor ferromagnetic pair interactions.NSF Predoctoral Fellow (1976–1979). Research supported in part by NSF Grant PHY 78-23952. 相似文献
2.
N. F. J. Matthews 《General Relativity and Gravitation》1992,24(1):17-33
The strength of Einstein's empty-space field equations is computed anew and shown to be equal to the amount of initial data required for a local solution of the equations. This same amount of initial data is shown to be precisely that required for a set of 16 unknown first-order differential equations containing 10 field variables and having six identities of second order. The 10 field variables must be functions of second order in the metric coefficients. The 16 field equationsC
, = 0 whereC
is Weyl's conformal tensor, are shown to have the same properties as those of the unknown equations, suggesting thatC
= 0 is a satisfactory local first-order formulation of Einstein's second-order empty-space field equations. 相似文献
3.
We present a regular class of exact black hole solutions of the Einstein equations coupled with a nonlinear electrodynamics source. For weak fields the nonlinear electrodynamics becomes the Maxwell theory, and asymptotically the solutions behave as the Reissner–Nordström one. The class is endowed with four parameters, which can be thought of as the mass m, charge q, and a sort of dipole and quadrupole moments and , respectively. For 3, 4, and |q|2s
c
m the corresponding solutions are regular charged black holes. For = 3, they also satisfy the weak energy condition. For = = 0 we recover the Reissner–Nordström singular solution and for = 3, = 4 the family includes a previous regular black hole reported by the authors. 相似文献
4.
Einstein's equations are rewritten in terms of a certain torsionless linear connection
which differs, in general, from the Levi-Civita metric connection
. The torsionless connection
appears in a natural way as the canonical momentum of the gravitational field g
. Einstein's equations have a simple interpretation in terms of the connection
. The equivalence of the so-calledpurely metric, purely affine, andmetricaffine theories of gravitation is proved.This work has been written under the financial support of Gruppo Nazionale per la Fisica Matematica of the Italian National Research Council. 相似文献
5.
Hans-Werner Wiesbrock 《Letters in Mathematical Physics》1993,28(2):107-114
LetN, be a von Neumann algebras on a Hilbert space , a common cyclic and separating vector. Assume to be cyclic and also separating forN . Denote by ,
N
,
N the modular operators to (, ), (N, ), resp (N , ). Assume now
-it
N
it
N for allt 0. (Such type of inclusions ((N U, ) , ) are called half-sided modular.) Then the modular groups
it
,
N
ir
,
N
is
,t, r, s generate a unitary representation of the group S1(2, )/Z
2 of positive energy.Another result is related to two half-sided modular inclusions (1 , ) and (2 , ). Under proper conditions the three modular groups
it
,
1
ir
,
2
is
,t, r, s generate the three-dimensional subgroup of O(2, 1) of two commuting translations and the Lorentz transformation.Partly supported by the DFG, SFB 288 Differentialgeometrie und Quantenphysik. 相似文献
6.
Asher Peres 《Foundations of Physics》1985,15(2):201-205
Linear combinations of elements of reality, as defined by Einstein, Podolsky, and Rosen, may not be themselves elements of reality. There are questions which can be formulated (and unambiguously answered) in the ordinary language of experimental physics, but cannot be represented in the mathematical framework of quantum theory in a nontrivial way. 相似文献
7.
Charles Radin 《Communications in Mathematical Physics》1971,23(3):189-198
By introducing a specific type of perturbation,A, in the Hamiltonian, we define a class of gently perturbed states, ,A, of a canonical ensemble, . The perturbations are chosen so as to preserve a relationship of the form ,A constant ×. Applications in ergodic theory and phase transitions are described. 相似文献
8.
Dénes Petz 《Letters in Mathematical Physics》1992,24(3):211-220
The central limit theorem of Cushen and Hudson is reformulated on the algebra of the CCR. Namely, for a gauge invariant state , the weighted convolutions
n
of the central limit tend to the quasi-free reduction
Q
of pointwise. It is proved that if the initial relative entropy S(,
Q
) is finite, then S(
n
,
Q
) goes to 0 and so
n
–
Q
0. No restriction on the dimension of the test function space is made. 相似文献
9.
The Einstein universe is a simple model describing a static cosmological spacetime, having a constant radius and a constant curvature, and, as is well known, it does not describe our universe. We propose a model which is an extension of Einstein's. Our metric, havingR × S
3 topology, describes a nonisotropic homogeneous closed (finite) universe of Bianchi type IX. This metric is similar to that of Taub, but is simpler. Unlike the Taub solution (which is a cosmological extension of the NUT solution), however, the universe described by our metric contains matter. Like the Taub metric, our metric has two positive constants (, T). The gravitational red shift calculated from our metric is given. Similarly to the Schwarzschild metric, which has a singularity atr = 2m, this metric has the same kind of singularity att = 2. The maximal extension of the coordinates in our metric is fairly analogous to that of the Schwarzschild metric. 相似文献
10.
For a -dimensional system of particles with the two-body potentialq(r)+
v
K(r) and density , it is proved under fairly weak conditions onq andK that the canonical pressure (, ) and chemical potential (, ) tend to definite limits when 0. The limiting functions are absolutely continuous and are given in terms of the derivative of the limiting free energy density
which was found in Part I. 相似文献
11.
John Stachel 《General Relativity and Gravitation》1977,8(8):705-712
A first-order Lagrangian is given, from which follow the definitions of the fully covariant form of the Riemann tensorR
k in terms of the affine connection and metric; the definition of the affine connection in terms of the metric; the Einstein field equations; and the definition of a set of gravitational superpotentials closely connected with the Komar conservation laws [7]. Substitution of the definition of the affine connection into this Lagrangian results in a second-order Lagrangian, from which follow the definition of the fully covariant Riemann tensor in terms of the metric, the Einstein equations, and the definition of the gravitational superpotentials.Dedicated to Achille Papapetrou on the occasion of his retirement. 相似文献
12.
In algebraically special Einstein spaces (Rv=0) with a hypersurfaceorthogonal spacelike Killing vector field v, the trajectories of the multiple eigen null directions k lie — except one case — in the subspacesV
3 orthogonal to v (k=0) and are hypersurface-orthogonal. The solutions with vanishing expansion (k,;=0, Kundt's class) can be determined explicitly. 相似文献
13.
Li Yuanjie 《International Journal of Theoretical Physics》1993,32(9):1619-1625
In this paper we propose a new theory of a fiber bundle provided with a local metric of internal space. The fibers differ from usual fibers, having an enlarged factor. The enlargement may be procured by a differential mapping(x) from structure groupG to the fiberF
x atx M, and(x)R. The torsion presented stems from the local metric of internal space and the local metric stems from a induced mapping
*(x) of(x). From the theory we can get the Brans-Dicke theory with torsion. If we assume the spin density of the gauge field determines the enlarged factor of the fiberF
x, our theory is an extended Cartan theory. 相似文献
14.
The structural and dynamic parameters of urea at 112°K and 295°K were determined by the least squares method. The characteristic temperature of the torsional optical vibrations of a molecule about a C-O bond was determined and is in good agreement with the value determined by Raman scattering. The fractional X-coordinate of the nitrogen atom corrected for torsional vibrations was determined and it was found that the magnitude of the projection of the C-N bond in the given temperature range changes only within the limits of observational errors. A new method, called temperature difference synthesis, is described and it is shown that it is suitable for rapid qualitative determination of the thermal anisotropy of the vibrations of atoms in a crystal lattice.
112°K 295°K. C-O , , . X- , C-N . , , , .相似文献
15.
S. Sarkar 《International Journal of Theoretical Physics》1973,8(3):171-178
In this paper we have evaluated
iui, ijuij, Tr(
i,u)Tr(
iu), Tr(
ijv) and Tr(u) whereu andv involve Pauli matrices
i and the 2×2 unit matrix in the form of products of elements of the typea
r=a
r
ii+ia
r
4 with the help of the results of the trace calculation involving Dirac matrices. We have evaluated v
U,
S
, v
U
v, Tr(
5 U)Tr(
5 V), Tr(
5 U) and Tr(U). HereU,V are products of an even number of elements andS, Sare products of an odd number of elements of the typeA
r(=A
r
. We have also dealt with the cases in which the dummy suffixesi and occurring in some of the above expressions are replaced by a which assume any specific value instead of implying a summation. We have considered also the evaluation of the above-mentioned traces when the term, 1 ±
5, occurs within the trace brackets; this is required in the calculation of the traces involving
i and the unit 2×2 matrix. It has been shown that the problem of the trace calculation involving Dirac matrices can be reduced to one involving three Pauli matrices
i and the unit 2×2 matrix. 相似文献
16.
17.
K. H. Fischer 《Zeitschrift für Physik B Condensed Matter》1981,43(4):291-297
The change of the sound velocity v(,T) and the damping of sound waves (,T) in spin glasses are calculated in the frame-work of an Ising model with a random distribution of exchange interactions. The calculation is based on linearized equations of motion for the spins and on an improved mean field approximation which includes the Onsager reaction field. Near to the freezing temperatureT
f
and at high temperatures v(,T) and (,T) turn out to be approximately proportional to the real and the imaginary parts of the dynamical susceptibility. For the special case of infinite range interactions atT=T
f
one has v(, Tf) ( )1/2 and (, Tf) (/)1/2 where is the relaxation time of independent spins. However, already slightly aboveT
f
the frequency dependence of both quantities becomes rather small for RKKY spin glasses. At high temperatures both, v(,T) and (,T) vary asT
–1.SFB 125 Aachen-Jülich-Köln 相似文献
18.
Domingos H. U. Marchetti Abel Klein J. Fernando Perez 《Journal of statistical physics》1990,60(1-2):137-166
We give a rigorous proof of power-law falloff in the Kosterlitz-Thouless phase of a two-dimensional Coulomb gas in the sense that there exists a critical inverse temperaturegb and a constant >0 such that for all> and all external charges R we have
, whereG
(x) is the two-point external charges correlation function,=dist(, Z), and
for
0$$
" align="middle" border="0">
. In the case of a hard-core or standard Coulomb gas with activityz, we may choose=(z) such that(z)24 asz0. 相似文献
19.
Paolo Buttà 《Journal of statistical physics》1993,72(5-6):1401-1406
We consider models of interface dynamics derived from Ising systems with Kac interactions and we prove the validity of the Einstein relation=, where is the proportionality coefficient in the motion by curvature, is the interface mobility, and is the surface tension. 相似文献
20.
A model for the distribution of cations in the spinel lattice of manganese ferrites MnFe2O4+
was elaborated on the basis of the experimental studies of the basic magnetic quantities, electrical conductivity and magnetic relaxation of the given ferrites, taking into consideration their crystallographic properties. The conclusions following from this model are in good agreement with the experimental results obtained by us and by other authors both for stoichiometric manganese ferrite and for a ferrite where 0.
I. MnFe2O4+
, MnFe2O4+ . , , , , , 0.相似文献