1,151 research outputs found
Half-Twisted Correlators from the Coulomb Branch
We compute correlators of chiral operators in half-twisted (0,2)
supersymmetric gauged linear sigma models. Our results give simple algebraic
formulas for a (0,2) generalization of genus zero Gromov-Witten invariants of
compact toric varieties. We derive compact expressions for deformed quantum
cohomology relations and apply our general method to several examples.Comment: 21 pages, LaTex; typos corrected; some discussion adde
Ordering of small particles in one-dimensional coherent structures by time-periodic flows
Small particles transported by a fluid medium do not necessarily have to
follow the flow. We show that for a wide class of time-periodic incompressible
flows inertial particles have a tendency to spontaneously align in
one-dimensional dynamic coherent structures. This effect may take place for
particles so small that often they would be expected to behave as passive
tracers and be used in PIV measurement technique. We link the particle tendency
to form one-dimensional structures to the nonlinear phenomenon of phase
locking. We propose that this general mechanism is, in particular, responsible
for the enigmatic formation of the `particle accumulation structures'
discovered experimentally in thermocapillary flows more than a decade ago and
unexplained until now
Models of G time variations in diverse dimensions
A review of different cosmological models in diverse dimensions leading to a
relatively small time variation of the effective gravitational constant G is
presented. Among them: 4-dimensional general scalar-tensor model,
multidimensional vacuum model with two curved Einstein spaces, multidimensional
model with multicomponent anisotropic "perfect fluid", S-brane model with
scalar fields and two form field etc. It is shown that there exist different
possible ways of explanation of relatively small time variation of the
effective gravitational constant G compatible with present cosmological data
(e.g. acceleration): 4-dimensional scalar-tensor theories or multidimensional
cosmological models with different matter sources. The experimental bounds on
G-dot may be satisfied ether in some restricted interval or for all allowed
values of the synchronous time variable.Comment: 27 pages, Late
Combinatorics of -orbits and Bruhat--Chevalley order on involutions
Let be the group of invertible upper-triangular complex
matrices, the space of upper-triangular complex matrices with
zeroes on the diagonal and its dual space. The group acts
on by , , ,
.
To each involution in , the symmetric group on letters, one
can assign the -orbit . We present a
combinatorial description of the partial order on the set of involutions
induced by the orbit closures. The answer is given in terms of rook placements
and is dual to A. Melnikov's results on -orbits on .
Using results of F. Incitti, we also prove that this partial order coincides
with the restriction of the Bruhat--Chevalley order to the set of involutions.Comment: 27 page
Multidimensional integrable vacuum cosmology with two curvatures
The vacuum cosmological model on the manifold describing the evolution of Einstein spaces of non-zero
curvatures is considered. For the Einstein equations are reduced to the
Abel (ordinary differential) equation and solved, when dim dim. The Kasner-like behaviour of the
solutions near the singularity is considered ( is synchronous
time). The exceptional ("Milne-type") solutions are obtained for arbitrary .
For these solutions are attractors for other ones, when . For dim and certain two-parametric
families of solutions are obtained from ones using "curvature-splitting"
trick. In the case , a family of non-singular
solutions with the topology is found.Comment: 21 pages, LaTex. 5 figures are available upon request (hard copy).
Submitted to Classical and Quantum Gravit
Resonance Zones and Lobe Volumes for Volume-Preserving Maps
We study exact, volume-preserving diffeomorphisms that have heteroclinic
connections between a pair of normally hyperbolic invariant manifolds. We
develop a general theory of lobes, showing that the lobe volume is given by an
integral of a generating form over the primary intersection, a subset of the
heteroclinic orbits. Our definition reproduces the classical action formula in
the planar, twist map case. For perturbations from a heteroclinic connection,
the lobe volume is shown to reduce, to lowest order, to a suitable integral of
a Melnikov function.Comment: ams laTeX, 8 figure
Scaling of the low temperature dephasing rate in Kondo systems
We present phase coherence time measurements in quasi-one-dimensional Ag
wires doped with Fe Kondo impurities of different concentrations . Due to
the relatively high Kondo temperature of this system, we
are able to explore a temperature range from above down to below . We show that the magnetic contribution to the dephasing rate
per impurity is described by a single, universal curve when plotted as a
function of . For , the dephasing rate is remarkably well
described by recent numerical results for spin impurities. At lower
temperature, we observe deviations from this theory. Based on a comparison with
theoretical calculations for , we discuss possible explanations for the
observed deviations.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Electromagnetic and corpuscular emission from the solar flare of 1991 June 15: Continuous acceleraton of relativistic particles
Data on X-,γ-ray, optical and radio emission from the 1991 June 15 solar flare are considered. We have calculated the spectrum of protons that producesγ-rays during the gradual phase of the flare. The primary proton spectrum can be described as a Bessel-function-type up to 0.8 GeV and a power law with the spectral index ≈3 from 0.8 up to 10 GeV or above. We have also analyzed data on energetic particles near the Earth. Their spectrum differed from that of primary protons producingγ-ray line emission. In the gradual phase of the flare additional pulses of energy release occurred and the time profiles of cm-radio emission andγ-rays in the 0.8–10 MeV energy band and above 50 MeV coincided. A continuous and simultaneous stochastic acceleration of the protons and relativistic electrons at the gradual phase of the flare is considered as a natural explanation of the data
Study of self-actualization needs of Russian students as a factor of competitiveness in the labor market
The article discusses the results of the empirical study of self-actualization needs of Russian students on the example of three Russian universities: Moscow Region State University, Belgorod State National Research University and Bratsk State University. The concept of a self-actualizing personality by A. Maslow was taken as a theoretical foundation of the research. For the empirical study, N.F. Kalina’s adaptation of A.V. Lazukin’s diagnostic methods was use
- …