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1.
V. S. Popov B. M. Karnakov V. D. Mur 《Journal of Experimental and Theoretical Physics》1998,86(5):860-874
A semiclassical theory is developed for the ionization of atoms and negative ions in constant, uniform electric and magnetic
fields, including the Coulomb interaction between the electron and the atomic core during tunneling. The case of crossed fields
(Lorentz ionization) is examined specially, as well as the limit of a strong magnetic field. Analytic equations are derived
for arbitrary fields ℰ and ℋ that are weak compared to the characteristic intraatomic fields. The major results of this paper
are obtained using the “imaginary time” method (ITM), in which tunneling is described using the classical equations of motion
but with purely imaginary “time.” The possibility of generalizing the ITM to the relativistic case, as well as to states with
nonzero angular momentum, is pointed out.
Zh. éksp. Teor. Fiz. 113, 1579–1605 (May 1998) 相似文献
2.
Ziemowit Popowicz 《Czechoslovak Journal of Physics》2000,50(11):1341-1345
We study systematically the general properties of theB-extension of any integrable model and its properties as Hamiltonian structures etc. We clarify the origin of “exotic” changes
in such models. We show that in such models there exist at least two sets of non-local conserved charges and that the “exotic”
charges are part of this non-local charge hierarchy.
Presented at the 9th Colloquium “Quantum Groups and Integrable Systems”, Prague, 22–24 June 2000. 相似文献
3.
We consider a method for deriving relativistic two-body wave equations for fermions in the coordinate representation. The
Lagrangian of the theory is reformulated by eliminating the mediating fields by means of covariant Green's functions. Then,
the nonlocal interaction terms in the Lagrangian are reduced to local expressions which take into account retardation effects
approximately. We construct the Hamiltonian and two-fermion states of the quantized theory, employing an unconventional “empty”
vacuum state, and derive relativistic two-fermion wave equations. These equations are a generalization of the Breit equation
for systems with scalar, pseudoscalar, vector, pseudovector and tensor coupling. 相似文献
4.
We discuss the possibility of making the initial definitions of mutually different (possibly interacting, or even entangled) systems in the context of decoherence theory. We point out relativity of the concept of elementary physical system as well as point out complementarity of the different possible divisions of a composite system into “subsystems,” thus eventually sharpening the issue of “what is system.” 相似文献
5.
Federico Piazza 《Foundations of Physics》2010,40(3):239-266
Spacetime measurements and gravitational experiments are made by using objects, matter fields or particles and their mutual
relationships. As a consequence, any operationally meaningful assertion about spacetime is in fact an assertion about the
degrees of freedom of the matter (i.e. non gravitational) fields; those, say for definiteness, of the Standard Model of particle
physics. As for any quantum theory, the dynamics of the matter fields can be described in terms of a unitary evolution of
a state vector in a Hilbert space. By writing the Hilbert space as a generic tensor product of “subsystems” we analyse the
evolution of a state vector on an information theoretical basis and attempt to recover the usual spacetime relations from
the information exchanges between these subsystems. We consider generic interacting second quantized models with a finite
number of fermionic degrees of freedom and characterize on physical grounds the tensor product structure associated with the
class of “localized systems” and therefore with “position”. We find that in the case of free theories no spacetime relation
is operationally definable. On the contrary, by applying the same procedure to the simple interacting model of a one-dimensional
Heisenberg spin chain we recover the tensor product structure usually associated with “position”. Finally, we discuss the
possible role of gravity in this framework. 相似文献
6.
G. Omanović 《Foundations of Physics Letters》1997,10(5):427-440
We consider the theory of the massive real vector field with spin 1 (the real Proca field) and its solutions. First the field
equations with dual symmetry [1] are written and the 4-pseudo vector is chosen to be zero. The constants of motion for the
real Proca field, the constant “electric” real Proca field, the uniform motion of a point charge in the real Proca field,
uniform motions in the “Coulomb” field, dipole and multipole free-momentum, constant “magnetic” field, and the field of a
point charge in motion are presented. 相似文献
7.
8.
K. Rasem Qandalji 《International Journal of Theoretical Physics》2009,48(6):1629-1636
We propose a single-step non-generational conjecture for derivation of all first class constraints, (involving, only, variables
compatible with canonical Poisson brackets), of a realistic gauge (singular) field theory. We verify our conjecture for the
free electromagnetic field, the Yang-Mills fields in interaction with spinor and scalar fields, and we also verify our conjecture
in the case of gravitational field. We show that the first class constraints, which were reached at using the standard Dirac’s
multi-generational algorithm, will be reproduced using the proposed conjecture. We make no claim that this conjecture is valid
for all “mathematically” plausible Lagrangians; but, nevertheless, the examples we consider here show that this conjecture
is valid for a “wide” range or much of realistic fields of Physical interest that are known to exist and be manifested in
nature. 相似文献
9.
G. P. Berman A. R. Bishop D. A. R. Dalvit G. V. Shlyapnikov N. Tarkhanov E. M. Timmermans 《International Journal of Theoretical Physics》2008,47(9):2393-2408
We rigorously analyze the stability of the “quasi-classical” dynamics of a Bose-Einstein condensate with repulsive and attractive
interactions, trapped in an effective 1D toroidal geometry. The “classical” dynamics, which corresponds to the Gross-Pitaevskii
mean field theory, is stable in the case of repulsive interaction, and unstable (under some conditions) in the case of attractive
interaction. The corresponding quantum dynamics for observables is described by using a closed system of linear partial differential
equations. In both cases of stable and unstable quasi-classical dynamics the quantum effects represent a singular perturbation
to the quasi-classical solutions, and are described by the terms in these equations which consist of a small quasi-classical
parameter which multiplies high-order “spatial” derivatives. We demonstrate that as a result of the quantum singularity for
observables a convergence of quantum solutions to the corresponding classical solutions exists only for limited times, and
estimate the characteristic time-scales of the convergence. 相似文献
10.
N. V. Antonov 《Journal of Experimental and Theoretical Physics》1997,85(5):898-906
The problem of turbulent mixing of a passive scalar impurity is studied within the renormalization-group approach to the stochastic
theory of developed turbulence for the case where the diffusion coefficient is an arbitrary function of the impurity concentration.
Such a problem incorporates an infinite number of coupling constants (“charges”). A one-loop calculation shows that in the
infinite-dimensional space of the charges there is a two-dimensional surface of fixed points of the renormalization-group
equations. When the surface has an IR-stability region, the problem has scaling with universal critical dimensionalities,
corresponding to the phenomenological laws of Kolmogorov and Richardson, but with nonuniversal (i.e., depending on the Prandtl
number and the explicit form of the nonlinearity in the diffusion equation) scaling functions, amplitude factors in the power
laws, and value of the “effective Prandtl turbulence number.”
Zh. éksp. Teor. Fiz. 112, 1649–1663 (November 1997) 相似文献
11.
M. Combescot W. Pogosov 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(2):161-181
We present a many-body theory for Frenkel excitons which takes into account their composite nature exactly. Our approach is
based on four commutators similar to the ones we previously proposed for Wannier excitons. They allow us to calculate any
physical quantity dealing with N excitons in terms of “Pauli scatterings” for carrier exchange in the absence of carrier interaction
and “interaction scatterings” for carrier interactions in the absence of carrier exchange. We show that Frenkel excitons have
a novel “transfer assisted exchange scattering”, specific to these excitons. It comes from indirect Coulomb processes between
localized atomic states. These indirect processes, commonly called “electron-hole exchange” in the case of Wannier excitons
and most often neglected, are crucial for Frenkel excitons, as they are the only ones responsible for the excitation transfer.
We also show that in spite of the fact that Frenkel excitons are made of electrons and holes on the same atomic site, so that
we could naively see them as elementary particles, they definitely are composite objects, their composite nature appearing
through various properties, not always easy to guess. The present many-body theory for Frenkel excitons is thus going to appear
as highly valuable to securely tackle their many-body physics, as in the case of nonlinear optical effects in organic semiconductors. 相似文献
12.
Alexander L. Kholmetskii 《Foundations of Physics》2006,36(5):715-744
In this paper we pay attention to the inconsistency in the derivation of the symmetric electromagnetic energy–momentum tensor for a system of charged particles from its canonical form, when the homogeneous Maxwell’s equations are applied to the symmetrizing gauge transformation, while the non-homogeneous Maxwell’s equations are used to obtain the motional equation. Applying the appropriate non-homogeneous Maxwell’s equations to both operations, we obtained an additional symmetric term in the tensor, named as “compensating term”. Analyzing the structure of this “compensating term”, we suggested a method of “gauge renormalization”, which allows transforming the divergent terms of classical electrodynamics (infinite self-force, self-energy and self-momentum) to converging integrals. The motional equation obtained for a non-radiating charged particle does not contain its self-force, and the mass parameter includes the sum of mechanical and electromagnetic masses. The motional equation for a radiating particle also contains the sum of mechanical and electromagnetic masses, and does not yield any “runaway solutions”. It has been shown that the energy flux in a free electromagnetic field is guided by the Poynting vector, whereas the energy flux in a bound EM field is described by the generalized Umov’s vector, defined in the paper. The problem of electromagnetic momentum is also examined. 相似文献
13.
Decentralized partially observable Markov decision process (DEC-POMDP) models sequential decision making problems by a team of agents. Since the planning of DEC-POMDP can be interpreted as the maximum likelihood estimation for the latent variable model, DEC-POMDP can be solved by the EM algorithm. However, in EM for DEC-POMDP, the forward–backward algorithm needs to be calculated up to the infinite horizon, which impairs the computational efficiency. In this paper, we propose the Bellman EM algorithm (BEM) and the modified Bellman EM algorithm (MBEM) by introducing the forward and backward Bellman equations into EM. BEM can be more efficient than EM because BEM calculates the forward and backward Bellman equations instead of the forward–backward algorithm up to the infinite horizon. However, BEM cannot always be more efficient than EM when the size of problems is large because BEM calculates an inverse matrix. We circumvent this shortcoming in MBEM by calculating the forward and backward Bellman equations without the inverse matrix. Our numerical experiments demonstrate that the convergence of MBEM is faster than that of EM. 相似文献
14.
G. Prasad 《General Relativity and Gravitation》1979,11(3):177-188
This paper deals with the construction of “magnetic vorticity” vector using Greenberg's theory of spacelike congruences for
the trajectories of magnetic fields. A set of propagation equations is derived for the geometrical invariants associated with
the congruences of magnetic field lines and fluid flow lines. Some applications of these propagation equations are made. A
generalization of Ferraro's law of isorotation is obtained employing the propagation equation forω
2 along the magnetic field lines. 相似文献
15.
As in the ordinary bosonic Liouville field theory, in its N = 1 supersymmetric version, an infinite set of operator valued relations, the “higher equations of motions,” hold. The equations
are in one to one correspondence with the singular representations of the super Virasoro algebra and enumerated by a pair
of natural numbers (m, n). We explicitly demonstrate these equations in the classical case, where the equations of type (1, n) survive and can be interpreted directly as relations for classical fields. The general form of higher equations of motion
is established in the quantum case, both for the Neveu-Schwarz and Ramond series.
The text was submitted by the authors in English. 相似文献
16.
M. C. Land 《Foundations of Physics》1997,27(1):19-41
Despite the many successes of the relativistic quantum theory developed by Horwitz et al., certain difficulties persist in
the associated covariant classical mechanics. In this paper, we explore these difficulties through an examination of the classical.
Coulomb problem in the framework of off-shell electrodynamics. As the local gauge theory of a covariant quantum mechanics
with evolution paratmeter τ, off-shell electrodynamics constitutes a dynamical theory of ppacetime events, interacting through
five τ-dependent pre-Maxwell potentials. We present a straightforward solution of the classical equations of motion, for a
test event traversing the field induced by a “fixed” event (an event moving uniformly along the time axis at a fixed point
in space). This solution is seen to be unsatisfactory, and reveals the essential difficulties in the formalism at the classical
levels. We then offer a new model of the particle current—as a certain distribution of the event currents on the worldline—which
eliminates these difficulties and permits comparison of classisical off-shell electrodynamics with the standard Maxwell theory.
In this model, the “fixed” event induces a Yukawa-type potential, permitting a semiclassical identification of the pre-Maxwell
time scale λ with the inverse mass of the intervening photon. Numerical solutions to the equations of motion are compared
with the standard Maxwell solutions, and are seen to coincide when λ≳10−6 seconds, providing an initial estimate of this parameter. It is also demonstrated that the proposed model provides a natural
interpretation for the photon mass cut-off required for the renormalizability of the off-shell quantum electrodynamics. 相似文献
17.
S. A. Podosenov 《Russian Physics Journal》1997,40(10):985-994
Together with a “postulate of equivalent situations,” the exact solution for the field of a charge in a uniformly accelerated
noninertial frame of reference (NFR) makes it possible to find the space-time structure and fields of charged conductors of
arbitrary shape without using the Einstein equations. The energy of the electric field outside of a charged plane, which is
equal to the rest energy of the masses of the charges creating the field, is determined. The space-time metric outside of
the charged plane is established; it could also have been found from the exact solution of the Einstein-Maxwell equations.
This solution describes the equilibrium of charged dust in parallel electric and gravitational fields. The field and metric
are found outside of a charged conducting sphere. While it eliminates the self-energy divergence, the proposed method renders
the classical electrodynamics internally consistent on transition to any short distance.
All-Russian Scientific Research Institute of Opticophysical Measurements. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii,
Fizika, No. 10, pp. 63–74, October, 1997. 相似文献
18.
The D1–D5 system is believed to have an “orbifold point” in its moduli space where its low energy theory is a ?=4 supersymmetric
sigma model with target space M
N
/S
N
, where M is T
4 or K3. We study correlation functions of chiral operators in CFTs arising from such a theory. We construct a basic class of chiral
operators from twist fields of the symmetric group and the generators of the superconformal algebra. We find explicitly the
3-point functions for these chiral fields at large N; these expressions are “universal” in that they are independent of the choice of M. We observe that the result is a significantly simpler expression than the corresponding expression for the bosonic theory
based on the same orbifold target space.
Received: 29 March 2001 / Accepted: 20 January 2002 相似文献
19.
We discuss the one-dimensional Hubbard model, on finite sites spin chain, in context of the action of the direct product of two unitary groups SU(2)×SU(2). The symmetry revealed by this group is applicable in the procedure of exact diagonalization of the Hubbard Hamiltonian. This result combined with the translational symmetry, given as the basis of wavelets of the appropriate Fourier transforms, provides, besides the energy, additional conserved quantities, which are presented in the case of a half-filled, four sites spin chain. Since we are dealing with four elementary excitations, two quasiparticles called “spinons”, which carry spin, and two other called “holon” and “antyholon”, which carry charge, the usual spin-SU(2) algebra for spinons and the so called pseudospin-SU(2) algebra for holons and antiholons, provide four additional quantum numbers. 相似文献
20.
Cauchy—Riemann conditions and point singularities of solutions to linearized shallow-water equations
S. Yu. Dobrokhotov B. Tirozzi A. I. Shafarevich 《Russian Journal of Mathematical Physics》2007,14(2):217-223
Singular solutions with algebraic “square-root” type singularity of two-dimensional equations of shallow-water theory are
propagated along the trajectories of the external velocity field on which the field satisfies the Cauchy-Riemann conditions.
In other words, the differential of the phase flow is proportional to an orthogonal operator on such a trajectory.
It turns out that, in the linear approximation, this fact is closely related to the effect of “blurring” of solutions of hydrodynamical
equations; namely, a singular solution of the Cauchy problem for the linearized shallow-water equations preserves its shape
exactly (i.e., is not blurred) if and only if the Cauchy-Riemann conditions are satisfied on the trajectory (of the external
field) along which the perturbation is propagated. 相似文献