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991.
We discuss the dynamic properties of the square-lattice spin-1/2 XY model obtained using the two-dimensional Jordan-Wigner fermionization approach. We argue the relevance of the fermionic picture for interpreting the neutron scattering measurements in the two-dimensional frustrated quantum magnet Cs2CuCl4. 相似文献
992.
The free energy plays a fundamental role in statistical and condensed matter physics. A related notion of free energy plays
an important role in the study of hyperbolic dynamical systems. In this paper we introduce and study a natural notion of free
energy for surfaces with variable negative curvature. This geometric free energy encodes a new type of marked length spectrum
of closed geodesics, which lies between the well-known marked length spectrum (marked by the corresponding element of the
fundamental group) and the unmarked length spectrum. We prove that the free energy parametrizes the boundary of the domain
of convergence of a Poincaré series which also encodes this spectrum. We also show that this new length spectrum, or equivalently
the geometric free energy, is not an isometry invariant. In the final section we use tools from multifractal analysis to effect
a fine asymptotic comparison of word length and geodesic length of closed geodesics. We hope that our geometric understanding
of free energy will provide new insight into this fundamental physical and dynamical quantity.
The work of the second author was partially supported by a National Science Foundation grant DMS-0355180. This work was completed
during a visit by the first author to Penn State as a Shapiro Fellow. 相似文献
993.
G. F.J.?A?a?osEmail author F.?Baldovin C.?Tsallis 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,46(3):409-417
We perform a throughout numerical study of the average
sensitivity to initial conditions and entropy production for
two symplectically coupled standard maps focusing on the
control-parameter region close to regularity.
Although the system is ultimately strongly chaotic (positive
Lyapunov exponents), it first stays lengthily in
weak-chaotic regions (zero Lyapunov exponents).
We argue that the nonextensive
generalization of the classical formalism is an adequate
tool in order to get nontrivial information about the first stage of this crossover
phenomenon.
Within this context we analyze the relation
between the power-law sensitivity to initial conditions and the
entropy production. 相似文献
994.
In the context, some lanthanide (Eu3+, Tb3+ and Sm3+) complexes with conjugated carboxylic acids (pyridine-carboxylic acids derivatives) have been synthesized and characterized. The low temperature fluorescent spectra for these complexes have been measured at nitrogen atmosphere (77 K), indicating that the central Ln3+ ions locate in an equivalent coordination environment with low symmetry for most of these lanthanide complexes belonging to dimeric or polymeric structure. Therefore, the electronic dipole transition (supersensitive transition) (5D0 → 7F2 for Eu3+, 5D4 → 7F6 for Tb3+, 4G5/2 → 6H9/2 for Sm3+) and magnetic dipole transition (5D0 → 7F1 for Eu3+, 5D4 → 7F5 for Tb3+, 4G5/2 → 6H5/2 for Sm3+) show the regular change in the corresponding split number of fluorescent spectra, which can be realized to predict the fine structure of lanthanide complexes. 相似文献
995.
Ken D.?OlumEmail author Allen?EverettEmail author 《Foundations of Physics Letters》2005,18(4):379-385
In a recent paper, Mallett found a solution of the Einstein equations in which closed timelike curves (CTC’s) are present in the empty space outside an infinitely long cylinder of light moving in circular paths around an axis. Here we show that, for physically realistic energy densities, the CTC’s occur at distances from the axis greater than the radius of the visible universe by an immense factor. We then show that Mallett’s solution has a curvature singularity on the axis, even in the case where the intensity of the light vanishes. Thus it is not the solution one would get by starting with Minkowski space and establishing a cylinder of light. 相似文献
996.
997.
Salvatore?AntociEmail author Dierck-Ekkehard?Liebscher Luigi?Mihich 《General Relativity and Gravitation》2005,37(7):1191-1203
When sources are added at their right-hand sides, and g(ik) is a priori assumed to be the metric, the equations of Einstein’s Hermitian theory of relativity were shown to allow for an exact solution that describes the general electrostatic field of n point charges. Moreover, the injunction of spherical symmetry of g(ik) in the infinitesimal neighbourhood of each of the charges was proved to yield the equilibrium conditions of the n charges in keeping with ordinary electrostatics. The tensor g(ik), however, cannot be the metric of the theory, since it enters neither the eikonal equation nor the equation of motion of uncharged test particles. A physically correct metric that rules both the behaviour of wave fronts and of uncharged matter is the one indicated by Hély.In the present paper it is shown how the electrostatic solution predicts the structure of the n charged particles and their mutual positions of electrostatic equilibrium when Hély’s physically correct metric is adopted. 相似文献
998.
No Heading We show that the Dirac-von Neumann formalism for quantum mechanics can be obtained as an approximation of classical statistical
field theory. This approximation is based on the Taylor expansion (up to terms of the second order) of classical physical
variables – maps f : Ω → R, where Ω is the infinite-dimensional Hilbert space. The space of classical statistical states consists of Gaussian measures
ρ on Ω having zero mean value and dispersion σ2(ρ) ≈ h. This viewpoint to the conventional quantum formalism gives the possibility to create generalized quantum formalisms based
on expansions of classical physical variables in the Taylor series up to terms of nth order and considering statistical states ρ having dispersion σ2(ρ) = hn (for n = 2 we obtain the conventional quantum formalism). 相似文献
999.
I.?Weymann J.?Barna?Email author 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,46(2):289-299
Spin-dependent electronic transport through a quantum
dot has been analyzed theoretically in the cotunneling regime by
means of the second-order perturbation theory. The system is
described by the impurity Anderson Hamiltonian with arbitrary
Coulomb correlation parameter U. It is assumed that the dot
level is intrinsically spin-split due to an effective molecular
field exerted by a magnetic substrate. The dot is coupled to two
ferromagnetic leads whose magnetic moments are noncollinear. The
angular dependence of electric current, tunnel magnetoresistance,
and differential conductance are presented and discussed. The
evolution of a cotunneling gap with the angle between magnetic
moments and with the splitting of the dot level is also
demonstrated. 相似文献
1000.
We introduce a Selberg type zeta function of two variables which interpolates several higher Selberg zeta functions. The analytic continuation, the functional equation and the determinant expression of this function via the Laplacian on a Riemann surface are obtained.Mathematics Subject Classifications (2000). Primary 11M36, Secondary 33B15 相似文献