1,254 research outputs found
H-theorem in quantum physics
Remarkable progress of quantum information theory (QIT) allowed to formulate
mathematical theorems for conditions that data-transmitting or data-processing
occurs with a non-negative entropy gain. However, relation of these results
formulated in terms of entropy gain in quantum channels to temporal evolution
of real physical systems is not thoroughly understood. Here we build on the
mathematical formalism provided by QIT to formulate the quantum H-theorem in
terms of physical observables. We discuss the manifestation of the second law
of thermodynamics in quantum physics and uncover special situations where the
second law can be violated. We further demonstrate that the typical evolution
of energy-isolated quantum systems occurs with non-diminishing entropy.Comment: 8 pages, 4 figure
Spin Polarization Phenomena and Pseudospin Quantum Hall Ferromagnetism in the HgTe Quantum Well
The parallel field of a full spin polarization of the electron gas in a
\Gamma8 conduction band of the HgTe quantum well was obtained from the
magnetoresistance by three different ways in a zero and quasi-classical range
of perpendicular field component Bper. In the quantum Hall range of Bper the
spin polarization manifests in anticrossings of magnetic levels, which were
found to strongly nonmonotonously depend on Bper.Comment: to be published in AIP Conf. Proc.: 15-th International Conference on
Narrow Gap Systems (NGS-15
The Degenerate Parametric Oscillator and Ince's Equation
We construct Green's function for the quantum degenerate parametric
oscillator in terms of standard solutions of Ince's equation in a framework of
a general approach to harmonic oscillators. Exact time-dependent wave functions
and their connections with dynamical invariants and SU(1,1) group are also
discussed.Comment: 10 pages, no figure
Elastično raspršenje piona na polariziranom 3He u energijskom području ∆-rezonancije
The π3He interaction for the polarized target is studied in the fixed-centers approximation with all rescatterings included. Only the P33 wave is taken for the πN interaction. The nuclear wave function is taken either as a sum of Gaussians or as a Faddeev wave function in the s-wave approximation. The asymmetries for elastic π + 3He scattering at the lab energies Tπ =142, 180 and 256 MeV are calculated. The results are compared with experimental data.Razmatra se π3He interakcija s polariziranom metom u približenju nepomičnih središta, uključujući sva višestruka raspršenja. Za πN interakciju uzima se samo P33 val. Nuklearna se valna funkcija uzima bilo kao zbroj Gaussovih funkcija ili kao Faddeeva valna funkcija u aproksimaciji s-vala. Izračunali smo asimetrije za elastično π +3He raspršenje za laboratorijske energije Tπ =142, 180 i 256 MeV. Rezultati se uspoređuju s eksperimentalnim podacima
Elastično raspršenje piona na polariziranom 3He u energijskom području ∆-rezonancije
The π3He interaction for the polarized target is studied in the fixed-centers approximation with all rescatterings included. Only the P33 wave is taken for the πN interaction. The nuclear wave function is taken either as a sum of Gaussians or as a Faddeev wave function in the s-wave approximation. The asymmetries for elastic π + 3He scattering at the lab energies Tπ =142, 180 and 256 MeV are calculated. The results are compared with experimental data.Razmatra se π3He interakcija s polariziranom metom u približenju nepomičnih središta, uključujući sva višestruka raspršenja. Za πN interakciju uzima se samo P33 val. Nuklearna se valna funkcija uzima bilo kao zbroj Gaussovih funkcija ili kao Faddeeva valna funkcija u aproksimaciji s-vala. Izračunali smo asimetrije za elastično π +3He raspršenje za laboratorijske energije Tπ =142, 180 i 256 MeV. Rezultati se uspoređuju s eksperimentalnim podacima
The Minimum-Uncertainty Squeezed States for for Atoms and Photons in a Cavity
We describe a six-parameter family of the minimum-uncertainty squeezed states
for the harmonic oscillator in nonrelativistic quantum mechanics. They are
derived by the action of corresponding maximal kinematical invariance group on
the standard ground state solution. We show that the product of the variances
attains the required minimum value 1/4 only at the instances that one variance
is a minimum and the other is a maximum, when the squeezing of one of the
variances occurs. The generalized coherent states are explicitly constructed
and their Wigner function is studied. The overlap coefficients between the
squeezed, or generalized harmonic, and the Fock states are explicitly evaluated
in terms of hypergeometric functions. The corresponding photons statistics are
discussed and some applications to quantum optics, cavity quantum
electrodynamics, and superfocusing in channeling scattering are mentioned.
Explicit solutions of the Heisenberg equations for radiation field operators
with squeezing are found.Comment: 27 pages, no figures, 174 references J. Phys. B: At. Mol. Opt. Phys.,
Special Issue celebrating the 20th anniversary of quantum state engineering
(R. Blatt, A. Lvovsky, and G. Milburn, Guest Editors), May 201
Renormalization Group Functions for Two-Dimensional Phase Transitions: To the Problem of Singular Contributions
According to the available publications, the field theoretical
renormalization group (RG) approach in the two-dimensional case gives the
critical exponents that differ from the known exact values. This fact was
attempted to explain by the existence of nonanalytic contributions in the RG
functions. The situation is analysed in this work using a new algorithm for
summing divergent series that makes it possible to analyse dependence of the
results for the critical exponents on the expansion coefficients for RG
functions. It has been shown that the exact values of all the exponents can be
obtained with a reasonable form of the coefficient functions. These functions
have small nonmonotonities or inflections, which are poorly reproduced in
natural interpolations. It is not necessary to assume the existence of singular
contributions in RG functions.Comment: PDF, 11 page
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