2,481 research outputs found
Dynamics of matter-wave and optical fields in superradiant scattering from Bose-Einstein condensates
We study superradiant scattering off Bose-Einstein condensates by solving the
semiclassical Maxwell-Schroedinger equations describing the coupled dynamics of
matter-wave and optical fields. Taking the spatial dependence of these fields
along the condensate axis into account, we are able to reproduce and explain
many of the characteristic features observed in the experiments of Inouye et
al. [Science 285, 571 (1999)] and Schneble et al. [Science 300, 475 (2003)],
such as the shape of the atomic side-mode distributions for forward and
backward scattering, the spatial asymmetry between forward and backward side
modes, and the depletion of the condensate center observed for forward
scattering.Comment: 4 pages, 2 figure
Cocliques of maximal size in the prime graph of a finite simple group
In this paper we continue our investgation of the prime graph of a finite
simple group started in http://arxiv.org/abs/math/0506294 (the printed version
appeared in [1]). We describe all cocliques of maximal size for all finite
simple groups and also we correct mistakes and misprints from our previous
paper. The list of correction is given in Appendix of the present paper.Comment: published version with correction
A possibility for precise Weinberg angle measurement in centrosymmetric crystals with axis
We demonstrate that parity nonconserving interaction due to the nuclear weak
charge Q_W leads to nonlinear magnetoelectric effect in centrosymmetric
paramagnetic crystals. It is shown that the effect exists only in crystals with
special symmetry axis k. Kinematically, the correlation (correction to energy)
has the form H_PNC ~ Q_W (E,[B,k])(B,k), where B and E are the external
magnetic and electric fields. This gives rise to magnetic induction M_PNC ~ Q_W
{k(B,[k,E]) + [k,E](B,k)}. To be specific we consider rare-earth trifluorides
and, in particular, dysprosium trifluoride which looks the most suitable for
experiment. We estimate the optimal temperature for the experiment to be of a
few kelvin. For the magnetic field B = 1 T and the electric field E = 10 kV/cm,
the expected magnetic induction is 4 \pi M_PNC = 0.5 * 10^-11 G, six orders of
magnitude larger than the best sensitivity currently under discussion.
Dysprosium has several stable isotopes, and so, comparison of the effects for
different isotopes provides possibility for precise measurement of the Weinberg
angle.Comment: 7 pages, 1 figure, 2 tables; version 2 - added discussion of neutron
distribution uncertaint
Chiral exponents in O(N) x O(m) spin models at O(1/N^2)
The critical exponents corresponding to chirality are computed at O(1/N^2) in
d-dimensions at the stable chiral fixed point of a scalar field theory with an
O(N) x O(m) symmetry. Pade-Borel estimates for the exponents are given in three
dimensions for the Landau-Ginzburg-Wilson model at m = 2.Comment: 8 latex page
Time-reversal violating generation of static magnetic and electric fields and a problem of electric dipole moment measurement
It is shown that in the experiments for search of the EDM of an electron
(atom, molecule) the T-odd magnetic moment induced by an electric field and the
T-odd electric dipole moment induced by a magnetic field will be also measured.
It is discussed how to distinguish these contributions.Comment: Latex, 5 pages with 1 Postscript figur
Enhanced longitudinal mode spacing in blue-violet InGaN semiconductor laser
A novel explanation of observed enhanced longitudinal mode spacing in InGaN
semiconductor lasers has been proposed. It has been demonstrated that e-h
plasma oscillations, which can exist in the laser active layer at certain
driving conditions, are responsible for mode clustering effect. The resonant
excitation of the plasma oscillations occurs due to longitudinal mode beating.
The separation of mode clusters is typically by an order of magnitude larger
that the individual mode spacing.Comment: 3 pages, 2 figure
Dimensional reduction of the chiral-continous Gross-Neveu model
We study the finite-temperature phase transition of the generalized
Gross-Neveu model with continous chiral symmetry in euclidean
dimensions. The critical exponents are computed to the leading order in the
expansion at both zero and finite temperatures. A dimensionally reduced
theory is obtained after the introduction of thermal counterterms necessary to
cancel thermal divergences that arise in the limit of high temperature.
Although at zero temperature we have an infinitely and continously degenerate
vacuum state, we show that at finite temperature this degeneracy is discrete
and, depending on the values of the bare parameters, we may have either total
or partial restoration of symmetry. Finally we determine the universality class
of the reduced theory by a simple analysis of the infrared structure of
thermodynamic quantities computed using the reduced action as starting point.Comment: Latex, 25 pages, 4 eps fig., uses epsf.sty and epsf.te
Spatial effects in superradiant Rayleigh scattering from Bose-Einstein condensates
We present a detailed theoretical analysis of superradiant Rayleigh
scattering from atomic Bose-Einstein condensates. A thorough investigation of
the spatially resolved time-evolution of optical and matter-wave fields is
performed in the framework of the semiclassical Maxwell-Schroedinger equations.
Our theory is not only able to explain many of the known experimental
observations, e.g., the behavior of the atomic side-mode distributions, but
also provides further detailed insights into the coupled dynamics of optical
and matter-wave fields. To work out the significance of propagation effects, we
compare our results to other theoretical models in which these effects are
neglected.Comment: 14 pages, 13 figure
Leading infrared logarithms for sigma-model with fields on arbitrary Riemann manifold
We derive non-linear recursion equation for the leading infrared logarithms
(LL) in four dimensional sigma-model with fields on an arbitrary Riemann
manifold. The derived equation allows one to compute leading infrared
logarithms to essentially unlimited loop order in terms of geometric
characteristics of the Riemann manifold.
We reduce the solution of the SU(oo) principal chiral field in arbitrary
number of dimensions in the LL approximation to the solution of very simple
recursive equation. This result paves a way to the solution of the model in
arbitrary number of dimensions at N-->ooComment: Talk given by MVP at the conference devoted to memory of A.N.
Vasilie
New four-dimensional integrals by Mellin-Barnes transform
This paper is devoted to the calculation by Mellin-Barnes transform of a
especial class of integrals. It contains double integrals in the position space
in d = 4-2e dimensions, where e is parameter of dimensional regularization.
These integrals contribute to the effective action of the N = 4 supersymmetric
Yang-Mills theory. The integrand is a fraction in which the numerator is a
logarithm of ratio of spacetime intervals, and the denominator is the product
of powers of spacetime intervals. According to the method developed in the
previous papers, in order to make use of the uniqueness technique for one of
two integrations, we shift exponents in powers in the denominator of integrands
by some multiples of e. As the next step, the second integration in the
position space is done by Mellin-Barnes transform. For normalizing procedure,
we reproduce first the known result obtained earlier by Gegenbauer polynomial
technique. Then, we make another shift of exponents in powers in the
denominator to create the logarithm in the numerator as the derivative with
respect to the shift parameter delta. We show that the technique of work with
the contour of the integral modified in this way by using Mellin-Barnes
transform repeats the technique of work with the contour of the integral
without such a modification. In particular, all the operations with a shift of
contour of integration over complex variables of two-fold Mellin-Barnes
transform are the same as before the delta modification of indices, and even
the poles of residues coincide. This confirms the observation made in the
previous papers that in the position space all the Green function of N = 4
supersymmetric Yang-Mills theory can be expressed in terms of UD functions.Comment: Talk at El Congreso de Matematica Capricornio, COMCA 2009,
Antofagasta, Chile and at DMFA seminar, UCSC, Concepcion, Chile, 24 pages;
revised version, Introduction is modified, Conclusion is added, five
Appendices are added, Appendix E is ne
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