共查询到20条相似文献,搜索用时 76 毫秒
1.
J. P. Kobus 《Foundations of Physics》1973,3(1):45-51
A geometric interpretation of gravitation is given using general relativity. The law of gravitation is taken in the formR
44=0, whereR
44is the component of the contracted Riemann-Christoffel (Ricci) tensor representing the curvature of time. The remaining curvature components of the contracted Riemann-Christoffel tensor may or may not vanish. All that is required in addition toR
44=0 is that the Gaussian curvatureR be nowhere infinite. The conditionR
44=0 yields a nonlinear wave equation. One of the static degenerate solutions represents the gravitational field surrounding a static gravitational point singularity. It is found that for this solution, the three famous predictions of general relativity are obtained in the weak-field approximation. In addition, it is found that there is a correction to the Kepler period of revolution for an orbit. 相似文献
2.
I. M. Dubrovskii 《Journal of Experimental and Theoretical Physics》1997,84(5):1022-1026
Because of attraction of the parallel currents forming an Abrikosov vortex, the vortex energy per unit length decreases, under
bending of the vortex, by a quantity proportional to the square of the curvature. Solving the London equation in an approximation
allowing for this effect makes it possible to calculate the energy of an Abrikosov vortex in the form of a helix whose length
and pitch are much larger than the correlation length, whose curvature is small compared to the reciprocal London length,
and whose slope in relation to an axis coinciding with the direction in which the vortex energy is the highest is also small.
When the anisotropy is large, which is characteristic of high-T
c superconductors, the energy of such an Abrikosov vortex is lower than that of a straight Abrikosov vortex. Certain consequences
of the fact that the Abrikosov vortices in a high-T
c superconductor are helical are discussed. Among these is a phase transition that breaks the symmetry between Abrikosov vortices
shaped like right-and left-hand helixes in relation to the magnetic field.
Zh. éksp. Teor. Fiz. 111, 1869–1878 (May 1997) 相似文献
3.
We study the curvature tensors and field equations in then-dimensional SE manifold SEXn. We obtain several basic properties of the vectorsS
andU
and then of the SE curvature tensor and its contractions, such as a generalized Ricci identity, a generalized Bianchi identity, and two variations of the Bianchi identity satisfied by the SE Einstein tensor. Finally, a system of field equations is discussed in SEXn and one of its particular solutions is constructed and displayed. 相似文献
4.
M. V. Karasev 《Russian Journal of Mathematical Physics》2012,19(3):299-306
For the Dirac 2D-operator in a constant magnetic field with perturbing electric potential, we derive Hamiltonians describing the quantum quasiparticles (Larmor vortices) at Landau levels. The discrete spectrum of this Hall-effect quantum Hamiltonian can be computed to all orders of the semiclassical approximation by a deformed Planck-type quantization condition on the 2D-plane; the standard magnetic (symplectic) form on the plane is corrected by an ??electric curvature?? determined via derivatives of the electric field. The electric curvature does not depend on the magnitude of the electric field and vanishes for homogeneous fields (i.e., for the canonical Hall effect). This curvature can be treated as an effective magnetic charge of the inhomogeneous Hall 2D-nanosystem. 相似文献
5.
Javier Alvarez-Jimenez Diego Gonzalez Daniel Gutiérrez-Ruiz Jose David Vergara 《Annalen der Physik》2020,532(2):1900215
The local geometry of the parameter space of a quantum system is described by the quantum metric tensor and the Berry curvature, which are two fundamental objects that play a crucial role in understanding geometrical aspects of condensed matter physics. Classical integrable systems are considered and a new approach is reported to obtain the classical analogs of the quantum metric tensor and the Berry curvature. An advantage of this approach is that it can be applied to a wide variety of classical systems corresponding to quantum systems with bosonic and fermionic degrees of freedom. The approach used arises from the semiclassical approximation of the Berry curvature and the quantum metric tensor in the Lagrangian formalism. This semiclassical approximation is exploited to establish, for the first time, the relation between the quantum metric tensor and its classical counterpart. The approach described is illustrated and validated by applying it to five systems: the generalized harmonic oscillator, the symmetric and linearly coupled harmonic oscillators, the singular Euclidean oscillator, and a spin-half particle in a magnetic field. Finally, some potential applications of this approach and possible generalizations that can be of interest in the field of condensed matter physics are mentioned. 相似文献
6.
The phase structure of a four-fermion (4F) model in curved spacetime with a magnetic field is investigated (in the framework
of a 1/N expansion and an approximation linear in the curvature). The effective potential for the combined fields
is calculated for the following situations: a) nonzero curvature and b) nonzero curvature and nonzero magnetic field. It
is shown that the gravitational field may offset the magnetic-field effect, with restoration of chiral symmetry as the result.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 43–47, July, 1997. 相似文献
7.
Using a gap equation for the pion mass a non-perturbative method is given for solving the chiral quark-meson model in the chiral limit at the lowest order in the fermion contributions encountered in a large-N fapproximation. The location of the tricritical point is analytically determined. A mean field potential is constructed from which critical exponents can be obtained. 相似文献
8.
9.
10.
A. G. Zhdanov A. K. Zvezdin A. P. Pyatakov T. B. Kosykh D. Viehland 《Physics of the Solid State》2006,48(1):88-95
The specific features of the “incommensurate-commensurate” phase transitions induced by a magnetic field in multiferroics
(materials with coexisting magnetic and electric ordering) are considered. These materials are ferroelectromagnets, for example,
bismuth ferrite BiFeO3 and BiFeO3-based compounds, which have spatially modulated spin structures. It is shown that the interaction between the electric and
magnetic subsystems of the multiferroic material can lead to an electric-field-induced shift of the critical magnetic field
corresponding to the transition from a spatially modulated state to a homogeneous antiferromagnetic state. According to the
theoretical estimates obtained for material parameters characteristic of the bismuth ferrite, this shift is of the order of
0.5 T in an electric field of 50 kV/cm. The phase diagrams are constructed in the “electric field-magnetic field” coordinates.
The results of calculations performed in the harmonic incommensurate structure approximation are compared with the exact soliton
solution. 相似文献
11.
12.
The Wiener-Hopf method is used to obtain a generalized Milne solution for scalar and electromagnetic fields with single-scattering anisotropy. For the scalar field, the solution found for the time correlation function and the interference component of backscattering is in good agreement with available experimental data. A solution of the Milne problem is constructed for the electromagnetic field. Given anisotropy, the generalized Milne equation is solved in the P1 approximation for the quantity that describes the degree of depolarization of the scattered light. It is shown that the depolarization of the scattered light can change sign at large anisotropies. 相似文献
13.
Dominic G. B. Edelen 《International Journal of Theoretical Physics》1988,27(5):641-648
A torsion-free solution of the free gauge field equations of direct Poincaré gauge theory on a ten-dimensional Minkowski space is constructed. This solution exhibits nontrivial curvature two-forms, but shaves the metric structure down to that of a four-dimensional Minkowski space. Universality of this solution with respect to the choice of the free field Lagrangian is established. 相似文献
14.
D. V. Kulakovskii S. I. Gubarev Yu. E. Lozovik 《Journal of Experimental and Theoretical Physics》2002,94(4):785-793
The changes in binding energy and oscillator strength of the exciton state due to the screening by a quasi-two-dimensional electron gas are calculated self-consistently in the approximation of noninteracting electrons and in the local field approximation. It is shown that the collapse of the bound state occurs at very low concentrations, N s≈5×109 cm?2, which is a consequence of the inclusion of the nonlinearity of the response of the system to a Coulomb perturbation. The temperature dependence of the exciton collapse is investigated. The phase diagram of the dissociation of the given bound state is constructed, and the region in which it is possible to observe experimentally the temperature dependence of the exciton collapse is indicated. 相似文献
15.
16.
Curvature and external electric field effects on the persistent current in chiral toroidal carbon nanotubes 总被引:1,自引:0,他引:1
N. Xu J. W. Ding H. B. Chen M. M. Ma 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(1):71-75
Taking into account the intrinsic curvature, we calculate the persistent currents (Ipcs) in chiral toroidal carbon nanotubes (TCNs) by developing the supercell approach. It is shown that in the presence of curvature,
the typical current (Ity) oscillates with the unit cell number (P) and tends to be zero, while it damps exponentially in the absence of curvature.
Due to the curvature effects, especially, a paramagnetism-diamagnetism transition is observed in chiral TCNs, depending on
the ring diameter and chirality. In addition, the effect of external electric field energy (Eef) on persistent current is also explored. It is shown that in the presence of electric field, Ity vary unmonotonously with Eef. A pronounced peak of Ity is obtained at high Eef region. By modulating the value of Eef, a paramagnetism-diamagnetism or diamagnetism- paramagnetism transition is observed. 相似文献
17.
Ahmet Baykal 《General Relativity and Gravitation》2012,44(8):1993-2017
The quadratic curvature lagrangians having metric field equations with second order trace are constructed relative to an orthonormal
coframe. In n > 4 dimensions, pure quadratic curvature lagrangian having second order trace constructed contains three free parameters
in the most general case. The fourth order field equations of some of these models, in arbitrary dimensions, are cast in a
particular form using the Schouten tensor. As a consequence, the field equations for the New massive gravity theory are related
to those of the Topologically massive gravity. In particular, the conditions under which the latter is “square root” of the
former are presented. 相似文献
18.
《Journal of Nonlinear Mathematical Physics》2013,20(3-4):503-515
Abstract Stationary kinetic equations for a quark plasma (QP) in the Abelian dominance approximation are reduced to the nonlinear system of A 2-periodic Toda chains (with elliptic operator). Using solutions of this system, which are found with the help of the first integrals and Hirota’s method, such characteristics of QPas the distribution function and the potential of the self-consistent field are constructed. 相似文献
19.
《Waves in Random and Complex Media》2013,23(4):L7-L11
Abstract Tilt invariance is a stringent but necessary condition that a second-order wave scattering model must satisfy in order to qualify for a broad range of applications. This invariance expresses the fact that the scattering model is unchanged whether the tilting of the scattering surface is implemented before or after its reduction to the limit of the small-perturbation method (SPM). Our scattering model is based on a second-order kernel which is quadratic in its lowest order with respect to successive derivatives of the rough surface. Hence, it is termed the local curvature approximation (LCA). We have previously demonstrated that the LCA is approximately tilt invariant in the quasi-specular and quasi-backscattering geometries. In this contribution, LCA is made formally tilt invariant up to first order in the tilting vector. It will be shown that this formal tilt invariance is achieved mainly through inclusion of polarization mixing due to out-of-plane tilt. Even though the LCA formally reduces to the SPM and Kirchhoff limits in addition to tilt invariance, its curvature kernel stays reasonably concise and practical to implement in both analytical and numerical evaluations. This curvature kernel may also be used in the other two formulations of our model, namely the non-local curvature approximation and the weighted curvature approximation. 相似文献
20.
We use an excited-de Sitter mode as the fundamental mode function for the far past time limit during inflation, to study the corrections of spectra of curvature perturbation. Excited-de Sitter mode is actually the approximate solution of the inflaton field equation that asymptotically approaches to the de Sitter mode function in the first approximation. We build coherent state over excited-de Sitter mode. Then, we compute spectrum of the curvature perturbation with this coherent state as the initial state. We show that in this case, the spectrum of curvature perturbation is scale dependent. As a important result of using this coherent state, we find a non-zero non-Gaussian one-point function as a possible tiny source for generation of anisotropy in CMB from the initial mode in the string or Planck scale. 相似文献