共查询到20条相似文献,搜索用时 156 毫秒
1.
Varsha Daftardar-Gejji 《General Relativity and Gravitation》1998,30(5):695-700
Brinkmann has shown that conformally related Einstein spaces are either Ricci flat pp-waves or conformally flat spaces with one as de Sitter space and the other being flat. We herewith show that if gikand
are distinct metrics for which
, then both represent (generalised) pp-waves; and w,iis a homothetic conformal Killing vector of gik. It is further observed that in the situation
we can have many (and also non-conformally flat) conformally related solutions, unlike in Einstein spaces. In particular for perfect fluid coupling, we show that the conformally related solutions have to be Friedman-Robertson-Walker metrics with equation of state as
, or pp-waves depending on whether w,iis timelike, spacelike or null. 相似文献
2.
According to the Einstein-Mayer theory of the Riemanniann space-time with Einstein-Cartan teleparallelism, the local Lorentz
invariance is broken by the gravitational field defining Machian reference systems. This breaking of symmetry implies the
occurrence of “hidden matter” in the Einstein equations of gravity. The hidden matter is described by the non-Lorentz-invariant
energy-momentum tensor
satisfying the relation
. The tensor
is formed from the Einstein-Cartan torsion field given by the anholonomy objects, FAik=2hA[i,k], and appears together with Hilbert’s energy-momentum tensor T*
ik and Poincaré’s pressure λgik on the right-hand side of Einstein’s equations so that one has
According to this theory, in the universe and in cosmic systems one must excep “invisible masses” described by the Poincaré
and Einstein-Cartan terms to exist. The torsion field FAik makes the space-time a Machian universe; it is of the same nature as the “weak interacting matter” discussed in astrophysics. 相似文献
3.
Letw = {w(x)xZd} be a positive random field with i.i.d. distribution. Given its realization, letX
t be the position at timet of a particle starting at the origin and performing a simple random walk with jump rate w–1(Xt). The processX={X
t:t0} combined withw on a common probability space is an example of random walk in random environment. We consider the quantities
t
=(d/dt) E
(X
t
2
–M
–1
t and
t(w) = (d/dt)Ew(X
t
2
– M– 1t). Here Ew. is expectation overX at fixedw and E = Ew (dw) is the expectation over bothX andw. We prove the following long-time tail results: (1) limt td/2t= V2Md/2–3(d/2)d/2 and (2) limt td/4
st(w)= Zs weakly in path space, with {Zs:s>0} the Gaussian process with EZs=0 and EZrZs= V2Md/2–4(d)d/2 (r + s)–d/2. HereM and V2 are the mean and variance of w(0) under . The main surprise is that fixingw changes the power of the long-time tail fromd/2 tod/4. Since
, with
0 the stationary measure for the environment process, our result (1) exhibits a long-time tail in an equilibrium autocorrelation function. 相似文献
4.
A. N. Temchin 《Russian Physics Journal》1982,25(2):114-117
Right zero-vectors of the characteristic matrix of the Einstein equations are constructed on isotropic cones. Relationships for the discontinuities of two derived functions of the field in the and surfaces
are indicated. Quantities describing the weak discontinuities of solutions of the gravitational field equations are constructed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 38–41, February, 1982. 相似文献
5.
Quantum-Logics-Valued Measure Convergence Theorem 总被引:1,自引:0,他引:1
In this paper, the following quantum-logic valued measure convergence theorem is proved: Let (L
1, 0, 1) be a Boolean algebra, (L
2, , , 0, 1) be a quantum logic and {
n
: n N} be a sequence of s-bounded (L
2, , , 0, 1)-valued measures which are defined on (L
1, 0, 1). If for each a (L
1, 0, 1), {
n
(a)}
n N
is an order topology
Cauchy sequence, when {v(a)} convergent to 0, {
n
(a)} is order topology
convergent to 0 for each n N, where v is a nonnegative finite additive measure which is defined on (L
1, 0, 1), then when {v(a)} convergent to 0, {
n
(a)} are order topology
convergent to 0 uniformly with respect to n N. 相似文献
6.
An Algebra of Deformation Quantization for Star-Exponentials on Complex Symplectic Manifolds 总被引:1,自引:0,他引:1
The cotangent bundle T
*
X to a complex manifold X is classically endowed with the sheaf of k-algebras of deformation quantization, where k := is a subfield of . Here, we construct a new sheaf of k-algebras which contains as a subalgebra and an extra central parameter t. We give the symbol calculus for this algebra and prove that quantized symplectic transformations operate on it. If P is any section of order zero of , we show that is well defined in . 相似文献
7.
We study the initial value problem for the two-dimensional nonlinear nonlocal Schrödinger equations i ut + u = N(v), (t, x, y) R3, u(0, x, y) = u0(x, y), (x, y) R2 (A), where the Laplacian = 2
x + 2
y, the solution u is a complex valued function, the nonlinear term N = N1 + N2 consists of the local nonlinear part N1(v) which is cubic with respect to the vector v=(u,ux,uy,\overline{u},\overline{u}_{x},\overline{u}_{y}) in the neighborhood of the origin, and the nonlocal nonlinear part N2(v) =(v, – 1
x Kx(v)) + (v, – 1
y Ky(v)), where (, ) denotes the inner product,
and the vectors Kx (C4(C6; C))6 and Ky (C4(C6; C))6 are quadratic with respect to the vector v in the neighborhood of the origin. We assume that the components K(2)
x = K(4)
x 0, K(3)
y = K(6)
y 0. In particular, Equation (A) includes two physical examples appearing in fluid dynamics. The elliptic–hyperbolic Davey–Stewartson system can be reduced to Equation (A) with
, and all the rest components of the vectors Kx and Ky are equal to zero. The elliptic–hyperbolic Ishimori system is involved in Equation (A), when
, and
. Our purpose in this paper is to prove the local existence in time of small solutions to the Cauchy problem (A) in the usual Sobolev space, and the global-in-time existence of small solutions to the Cauchy problem (A) in the weighted Sobolev space under some conditions on the complex conjugate structure of the nonlinear terms, namely if N(ei v) = ei N(v) for all R. 相似文献
8.
Zhi-Gang Wang Wei-Min Yang Shao-Long Wan 《The European Physical Journal C - Particles and Fields》2004,37(2):223-231
Making the assumption of explicit isospin violation arising from f
0(980)-a
0(980) mixing, we take the point of view that the scalar mesons f
0(980) and a
0(980) have both strange and non-strange quark-antiquark components and evaluate the strong coupling constants
within the framework of the light-cone QCD sum rules approach. The large strong scalar-KK couplings through both the
and
components
,
,
and
will support the hadronic dressing mechanism; furthermore, in spite of the constituent structure differences between the f
0(980) and a
0(980) mesons, the strange components have larger strong coupling constants with the K
+
K
- state than the corresponding non-strange ones,
and
. From the existing controversial values, we cannot reach a general consensus on the strong coupling constants
and the mixing angles.Received: 9 January 2004, Revised: 23 July 2004, Published online: 2 September 2004 相似文献
9.
Using the Godement mean of positive-type functions over a groupG, we study -abelian systems {
, } of aC*-algebra
and a homomorphic mapping of a groupG into the homomorphism group of
. Consideration of the Godement mean off(g)U
g
withf a positive-type function overG andU a unitary representation ofG first yields a generalized mean-ergodic theorem. We then define the Godement mean off(g) (
g
(A)) withA
and a covariant representation of the system {
, } for which theG-invariant Hilbert space vectors are cyclic and study its properties, notably in relation with ergodic and weakly mixing states over
. Finally we investigate the discrete spectrum of covariant representations of {
, } (i.e. the direct sum of the finite-dimensional subrepresentations of the associated representations ofG).On leave of absence from Istituto di Fisica G. Marconi Piazzale delle Scienze 5 — Roma. 相似文献
10.
The H Collaboration 《The European Physical Journal C - Particles and Fields》2003,29(4):497-513
Inclusive jet cross sections are measured in photoproduction at HERA using the H1 detector. The data sample of
events in the kinematic range of photon virtualities
and photon-proton centre-of-mass energies
represents an integrated luminosity of
. Jets are defined using the inclusive
algorithm. Single- and multi-differential cross sections are measured as functions of jet transverse energy ET jet and pseudorapidity
in the domain
and
. The cross sections are found to be in good agreement with next-to-leading order perturbative QCD calculations corrected for fragmentation and underlying event effects. The cross section differential in ET jet, which varies by six orders of magnitude over the measured range, is compared with similar distributions from
colliders at equal and higher energies.Received: 24 February 2003, Revised: 26 May 2003, Published online: 11 July 2003 相似文献
11.
V. R. Gavrilov V. N. Melnikov S. T. Abdyrakhmanov 《General Relativity and Gravitation》2004,36(7):1579-1592
We study a spatially flat Friedmann model containing a pressureless perfect fluid (dust) and a scalar field with an unbounded from below potential of the form
, where the parameters W
0 and V
0 are arbitrary and
. The model is integrable and all exact solutions describe the recollapsing universe. The behavior of the model near both initial and final points of evolution is analyzed. The model is consistent with the observational parameters. We single out the exact solution with the present-day values of acceleration parameter q
0=0.5 and dark matter density parameter 0=0.3 describing the evolution within the time approximately equal to 2H
0
–1. 相似文献
12.
Rainer Dick 《General Relativity and Gravitation》2004,36(1):217-224
I reconsider the problem of the Newtonian limit in nonlinear gravity models in the light of recently proposed models
with inverse powers of R. Expansion around a maximally symmetric local background with curvature scalar R
0 > 0 gives the correct Newtonian limit on length scales R
0
–1/2 if the gravitational Lagrangian
satisfies f(R
0)f(R0) 1, and I propose two models with f(R
0) = 0. 相似文献
13.
S. S. Agaev N. G. Stefanis 《The European Physical Journal C - Particles and Fields》2004,32(4):507-528
Employing the standard hard-scattering approach (HSA) in conjunction with the running coupling (RC) method, the latter joined with the infrared renormalon calculus, we compute power-suppressed corrections
to the massless
-meson-virtual-gluon transition form factor (FF)
. Contributions to the form factor from the quark and gluon components of the
meson are taken into account. Analytic expressions for the FFs
and
are also presented, as well as Borel transforms
and resummed expressions. It is shown that except for
, the Borel transform contains an infinite number of infrared renormalon poles. It is demonstrated that in the explored range of the total gluon virtuality
, power corrections found with the RC method considerably enhance the FF
relative to results obtained only in the context of the standard HSA with a frozen coupling.Received: 19 May 2003, Revised: 24 October 2003, Published online: 8 December 2003Permanent address: S.S. Agaev: High Energy Physics Lab., Baku State University, Z. Khalilov St. 23, 370148 Baku, Azerbaijan 相似文献
14.
We continue our study of the collision of two solitons for the subcritical generalized KdV equations
Solitons are solutions of the type where c
0 > 0. In [21], mainly devoted to the case f (u) = u
4, we have introduced a new framework to understand the collision of two solitons , for (0.1) in the case (or equivalently, ). In this paper, we consider the case of a general nonlinearity f (u) for which , are nonlinearly stable. In particular, since f is general and c
1 can be large, the results are not perturbations of the ones for the power case in [21].
First, we prove that the two solitons survive the collision up to a shift in their trajectory and up to a small perturbation
term whose size is explicitly controlled from above: after the collision, , where is close to c
j
(j = 1, 2). Then, we exhibit new exceptional solutions similar to multi-soliton solutions: for all , there exists a solution such that
where (j = 1, 2) and converges to 0 in a neighborhood of the solitons as .
The analysis is split in two distinct parts. For the interaction region, we extend the algebraic tools developed in [21] for
the power case, by expanding f (u) as a sum of powers plus a perturbation term. To study the solutions in large time, we rely on previous tools on asymptotic
stability in [17,22] and [18], refined in [19,20].
This research was supported in part by the Agence Nationale de la Recherche (ANR ONDENONLIN). 相似文献
15.
The theorem that each derivation of aC*-algebra
extends to an inner derivation of the weak-operator closure (
)– of
in each faithful representation of
is proved in sketch and used to study the automorphism group of
in its norm topology. It is proved that the connected component of the identity in this group contains the open ball of radius 2 with centerl and that each automorphism in extends to an inner automorphism of (
)–.Research conducted with the partial support of the NSF and ONR. 相似文献
16.
For a homogeneous quantum network of N subsystems with n levels each we consider separable generalized Werner states. A generalized Werner state is defined as a mixture of the totally mixed state and an arbitrary pure state
:
with a mixture coefficient
. For this density operator
to be separable,
will have an upper bound
. Below this bound one should alternatively be able to reproduce
by a mixture of entirely separable input-states. For this purpose we introduce a set of modules, each contributing elementary coherence properties with respect to a generalized coherence vector. Based on these there exists a general step-by-step mixing process for any
. For
being a cat-state it is possible to define an optimal process, which produces states right up to the separability boundary (
).Received: 3 December 2002, Published online: 29 July 2003PACS:
03.65.Ud Entanglement and quantum nonlocality (e.g. EPR paradox, Bells inequalities, GHZ states, etc.) - 03.67.-a Quantum information - 03.65.-w Quantum mechanics 相似文献
17.
S. Brian Edgar 《General Relativity and Gravitation》1995,27(2):223-231
When the Bianchi equation and the wave equation for the Weyl spinor are written in the form which they take for Einstein spaces, but with the symmetric 4-spinor
ABCD
considered arbitrary and with the background space unspecified,
EA
EBCD=0; (+12)
ABCD
–6(AB
EF
(
CD
)EF =0 it is shown that — in general — for this pair of equations to be consistent, the background space has to be an Einstein space, and the symmetric 4-spinor
ABCD
has to be the Weyl spinor of this space. 相似文献
18.
Yakov Sinai 《Journal of statistical physics》2005,121(5-6):779-803
In this paper we study the Fourier transform of the
-Navier-Stokes System without external forcing on the whole space R
3. The properties of solutions depend very much on the space in which the system is considered. In this paper we deal with
the space
of functions
where
and c (k) is bounded,
. We construct the power series which converges for small t and gives solutions of the system for bounded intervals of time. These solutions can be estimated at infinity (in k-space) by
. 相似文献
19.
O. A. Fonarev 《Russian Physics Journal》1990,33(9):759-764
We define a covariant and gauge-invariant generalization of the Wigner functions of particles with spins 1/2 and 0. The collisionless kinetic equations are obtained for these particles in external gravitational and electromagnetic fields in the quasiclassical approximation; also obtained are the momentum representations of the energy-momentum tensor, current, and spin tensor, taking into account the effects of the spin's interaction with the gravitational field an electromagnetic field. The following notation is used: e and m are the charge and mass of the particles; is Planck's constant; (x) are the covariant-fixed Dirac matrices; ,=(1/4)[, ]: a(b)=(1/2) (a
b
+ab
); [A, B]=A·B – B·A; A,B=A·B+B·A; g(x)=det(g
(x));R
=
–...; the speed of light c=1.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 47–53, September, 1990.The author wishes the thank Yu. G. Ignat'ev and members of the seminar in General Relativistic Statistics and Cosmology of the Kazan' Pedagogical Institute for useful discussions. 相似文献
20.
Let denote the class of all orthomodular lattices and denote the class of those that are commutator-finite. Also, let denote the class of orthomodular lattices that satisfy the block extension property, those that satisfy the weak block extension property, and those that are locally finite. We show that the following strict containments hold:
Dedicated to the memory of Günter Bruns. 相似文献