共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
Marzio Cassandro Immacolata Merola Maria Eulalia Vares 《Journal of statistical physics》2011,142(3):487-509
We consider a one dimensional ferromagnetic Ising spin system with interactions that correspond to a 1/r
2 long range perturbation of the usual Kac model. We apply a coarse graining procedure widely used for higher-dimensional finite
range Kac potentials to describe the basic properties of the system and the relation with the mean field theory. 相似文献
3.
Random billiards are billiard dynamical systems for which the reflection law giving the post-collision direction of a billiard particle as
a function of the pre-collision direction is specified by a Markov (scattering) operator P. Billiards with microstructure are random billiards whose Markov operator is derived from a “microscopic surface structure” on the boundary of the billiard
table. The microstructure in turn is defined in terms of what we call a billiard cellQ, the shape of which completely determines the operator P. This operator, defined on an appropriate Hilbert space, is bounded self-adjoint and, for the examples considered here, a
Hilbert-Schmidt operator. A central problem in the statistical theory of such random billiards is to relate the geometric
characteristics of Q and the spectrum of P. We show, for a particular family of billiard cell shapes parametrized by a scale invariant curvature K (Fig. 2), that the billiard Laplacian P−I is closely related to the ordinary spherical Laplacian, and indicate, by partly analytical and partly numerical means, how
this provides asymptotic information about the spectrum of P for small values of K. It is shown, in particular, that the second moment of scattering about the incidence angle closely approximates the spectral
gap of P. 相似文献
4.
A completely Lorentz-invariant Bohmian model has been proposed recently for the case of a system of non-interacting spinless
particles, obeying Klein-Gordon equations. It is based on a multi-temporal formalism and on the idea of treating the squared
norm of the wave function as a space-time probability density. The particle’s configurations evolve in space-time in terms
of a parameter σ with dimensions of time. In this work this model is further analyzed and extended to the case of an interaction with an external
electromagnetic field. The physical meaning of σ is explored. Two special situations are studied in depth: (1) the classical limit, where the Einsteinian Mechanics of Special
Relativity is recovered and the parameter σ is shown to tend to the particle’s proper time; and (2) the non-relativistic limit, where it is obtained a model very similar
to the usual non-relativistic Bohmian Mechanics but with the time of the frame of reference replaced by σ as the dynamical temporal parameter. 相似文献
5.
Mohsen Daeimohamad Fardin Kheirandish Khaled Saeedi 《International Journal of Theoretical Physics》2011,50(1):171-180
The dissipative quantum dynamics of a harmonic oscillator in the presence of a deformed bath is investigated. The deformed
bath is modelled by a collection of deformed quantum harmonic oscillators as a generalization of Hopfield model. The transition
probabilities between energy levels of the oscillator are obtained perturbatively and discussed. 相似文献
6.
A Kerr nonlinear blackbody (KNB) is a new kind of blackbody in which bare photons with opposite wave vectors and helicities
are bound into pairs and unpaired photons are transformed into nonpolaritons. In the present paper, the radiation of a KNB
is considered from the viewpoint of an observer in arbitrary uniform motion with respect to a rest frame of reference of the
radiation. It is found that the radiation laws, which include the distribution of nonpolaritons and so forth, are modified
due to the motion. Moreover, under a special condition, we notice that the only effect of the motion is to introduce an angle-dependent
directional temperature, which replaces the rest-frame temperature of the cavity. Besides, we try to extend the model of a
KNB to the whole Universe and apply the modified radiation laws to the question of 2.7 K cosmic microwave background radiation
(CMBR). 相似文献
7.
D. Nodop J. Rothhardt S. H?drich J. Limpert A. Tünnermann 《Applied physics. B, Lasers and optics》2009,94(3):399-401
We present a Q-switched microchip laser emitting 1064-nm pulses as short as 100 ps synchronized to a cavity dumped femtosecond
laser emitting 800-nm pulses as short as 80 fs. The synchronization is achieved by presaturating the saturable absorber of
the microchip laser with femtosecond pulses even though both lasers emit at widely separated wavelengths. The mean timing
jitter is 40 ps and thus considerably shorter than the pulse duration of the microchip laser. 相似文献
8.
José Ignacio Rosado 《Foundations of Physics》2011,41(7):1200-1213
The quantum state of a d-dimensional system can be represented by a probability distribution over the d
2 outcomes of a Symmetric Informationally Complete Positive Operator Valued Measure (SIC-POVM), and then this probability distribution
can be represented by a vector of
\mathbb Rd2-1\mathbb {R}^{d^{2}-1} in a (d
2−1)-dimensional simplex, we will call this set of vectors Q\mathcal{Q}. Other way of represent a d-dimensional system is by the corresponding Bloch vector also in
\mathbb Rd2-1\mathbb {R}^{d^{2}-1}, we will call this set of vectors B\mathcal{B}. In this paper it is proved that with the adequate scaling B=Q\mathcal{B}=\mathcal{Q}. Also we indicate some features of the shape of Q\mathcal{Q}. 相似文献
9.
Yudi Rosandi Herbert M. Urbassek 《Applied Physics A: Materials Science & Processing》2010,101(3):509-515
The optical properties of blue-violet InGaN light-emitting diodes under normal and reversed polarizations are numerically
studied. The best light-emitting performance under normal and reversed polarization is obtained in a single quantum-well structure
and double quantum-well structure, respectively. The key factors responsible for these phenomena are presumably the carrier
concentration distribution and the amount of carriers in quantum wells. The turn-on voltage of light-emitting diodes under
reversed polarization is lower than that of light-emitting diodes under normal polarization, due mainly to lower potential
heights for electrons and holes in the active region. 相似文献
10.
A branching random walk in presence of an absorbing wall moving at a constant velocity v undergoes a phase transition as the velocity v of the wall varies. Below the critical velocity v
c
, the population has a non-zero survival probability and when the population survives its size grows exponentially. We investigate
the histories of the population conditioned on having a single survivor at some final time T. We study the quasi-stationary regime for v<v
c
when T is large. To do so, one can construct a modified stochastic process which is equivalent to the original process conditioned
on having a single survivor at final time T. We then use this construction to show that the properties of the quasi-stationary regime are universal when v→v
c
. We also solve exactly a simple version of the problem, the exponential model, for which the study of the quasi-stationary
regime can be reduced to the analysis of a single one-dimensional map. 相似文献
11.
The propagation of a general-type of phase-locked beam array in a turbulent atmosphere is studied, in which four practical
issues, i.e., apertured, conformal, partially coherent, and flattened beam array is taken into consideration for accurate
modeling of beam array in power beaming applications. The average intensity distribution in the receiving plane is deduced
analytically based on extended Huygens–Fresnel principle. The influence of beam order, transverse coherence length, and truncation
ratio is briefly discussed. 相似文献
12.
R. S. Kolevatov 《The European Physical Journal C - Particles and Fields》2010,68(3-4):513-521
A fragmenting relativistic string is widely used for modeling particle production via quark–gluon strings formed in hadronic and nuclear inelastic interactions at high energies. In this note we focus on motion and fragmentation of a relativistic string with non-zero transverse separation of its ends and study this scenario as a possible mechanism for bringing anisotropy into the azimuthal angle distribution of produced particles in inelastic interactions of hadrons. 相似文献
13.
Amine Asselah 《Journal of statistical physics》2010,138(4-5):619-644
We consider a randomly charged polymer. Each monomer carries a random charge, and only charges on the same site interact pairwise. We study the lower tails of the energy, when averaged over both randomness, in dimension three or more. As a corollary, we obtain the correct temperature-scale for the Gibbs measure. 相似文献
14.
Peter Gregorčič Rok Petkovšek Janez Možina Griša Močnik 《Applied Physics A: Materials Science & Processing》2008,93(4):901-905
We present an optodynamic measurement of a laser-induced cavitation bubble and its oscillations based on a scanning technique
using a laser beam-deflection probe. The deflection of the beam was detected with a fast quadrant photodiode which was built
into the optical probe. The applied experimental setup enabled us to carry out one- or two-dimensional scanning of the cavitation
bubble, automatic control of the experiment, data acquisition and data processing. Shadow photography was used as a comparative
method during the experiments. 相似文献
15.
S. Aggoune F. Vidal E. H. Amara 《Applied Physics A: Materials Science & Processing》2010,101(1):167-171
The interaction between a laser-produced aluminum plasma and the ambient air, at a pressure of 173.3 Pa, is studied at the
plasma thermalization stage. A two-dimensional approach is developed to solve the Navier–Stokes equations, where a finite
volume discretization allows for obtaining a numerical solution. The simulation runs over a time representing 10 μs of plasma
expansion. It is shown that the shock and drag models are good approximations for the two successive regimes after the initial
strong expansion stage, and the calculation makes evident the plume sharpening on the axial direction before its confinement
by the ambient gas, which is in good agreement with the experimental observation. 相似文献
16.
We study the divergence of the solution to a Schrödinger-type amplifier driven by the square of a Gaussian noise in presence of a random potential. We follow the same approach as Mounaix, Collet, and Lebowitz (MCL) in terms of a distributional formulation of the amplified field and the use of the Paley-Wiener theorem (Mounaix et al. in Commun. Math. Phys. 264:741–758, 2006, Erratum: ibid. 280:281–283, 2008). Our results show that the divergence is not affected by the random potential, in the sense that it occurs at exactly the same coupling constant as what was found by MCL without a potential. It follows a fortiori that the breakdown of the amplifier is not affected by the possible existence of a localized regime in the amplification free limit. 相似文献
17.
Zaixing Huang 《International Journal of Theoretical Physics》2008,47(11):2850-2861
It is generally considered that global gauge symmetry of an action integral over a finite spatial-temporal domain as a whole
holds in any subdomain of this domain. However, in this paper we demonstrate that when the so-called localized assumption
is no longer valid, the global gauge symmetry will break in the subdomain of this spatial-temporal domain, due to occurrence
of a new source called the nonlocal residual. The nonlocal residual is correlated with a gauge field and satisfies the zero
mean condition with respect to whole spatial-temporal domain. An example is given to support this conclusion. 相似文献
18.
Ekaterina Turilova 《International Journal of Theoretical Physics》2009,48(11):3083-3091
Let ℳ be a von Neumann algebra acting on a Hilbert space H and let S be a dense lineal in H that is affiliated with a von Neumann algebra ℳ. The “topological” definition of measures on the classes of orthoclosed and
splitting subspaces of S affiliated with a von Neumann algebra ℳ is given and results on the relationships of these measures to measures on orthoprojections
of the algebra ℳ are presented. 相似文献
19.
Pulak Ranjan Giri 《International Journal of Theoretical Physics》2008,47(10):2583-2590
We argue that it is possible to bind neutral atom (NA) to the ferromagnetic wire (FW) by inequivalent quantization of the
Hamiltonian. We follow the well known von Neumann’s method of self-adjoint extensions (SAE) to get this inequivalent quantization,
which is characterized by a parameter Σ∈ℝ(mod2π). There exists a single bound state for the coupling constant η
2∈[0,1). Although this bound state should not occur due to the existence of classical scale symmetry in the problem. But since
quantization procedure breaks this classical symmetry, bound state comes out as a scale in the problem leading to scaling
anomaly. We also discuss the strong coupling region η
2<0, which supports bound state making the problem re-normalizable. 相似文献
20.
Kunji Nakayama 《International Journal of Theoretical Physics》2008,47(7):2065-2094
This paper deals with topos-theoretic truth-value valuations of quantum propositions. Concretely, a mathematical framework
of a specific type of modal approach is extended to the topos theory, and further, structures of the obtained truth-value
valuations are investigated. What is taken up is the modal approach based on a determinate lattice
, which is a sublattice of the lattice
of all quantum propositions and is determined by a quantum state e and a preferred determinate observable R. Topos-theoretic extension is made in the functor category
of which base category
is determined by R. Each true atom, which determines truth values, true or false, of all propositions in
, generates also a multi-valued valuation function of which domain and range are
and a Heyting algebra given by the subobject classifier in
, respectively. All true propositions in
are assigned the top element of the Heyting algebra by the valuation function. False propositions including the null proposition
are, however, assigned values larger than the bottom element. This defect can be removed by use of a subobject semi-classifier.
Furthermore, in order to treat all possible determinate observables in a unified framework, another valuations are constructed
in the functor category
. Here, the base category
includes all
’s as subcategories. Although
has a structure apparently different from
, a subobject semi-classifier of
gives valuations completely equivalent to those in
’s. 相似文献