264,538 research outputs found
Dual versions of N=2 supergravity and spontaneous supersymmetry breaking
In this paper, using a model of N=2 supergravity - vector multiplets
interaction with the scalar field geometry as an
example, we show that even when the geometry is fixed one can have a whole
family of the Lagrangians that differ by the vector field duality
transformations. As a byproduct, for this geometry we have constructed a model
of (m-1) vector multiplets interacting with the hidden sector admitting
spontaneous supersymmetry breaking with two arbitrary scales and without a
cosmological term.Comment: 10 pages, LaTeX, IHEP preprint 94-9
On Wilson Criterion
U(1) gauge theory with the Villain action on a cubic lattice approximation of
three- and four-dimensional torus is considered. The naturally chosen
correlation functions converge to the correlation functions of the R-gauge
electrodynamics on three- and four-dimensional torus as the lattice spacing
approaches zero only for the special scaling. This special scaling depends on a
choice of a correlation function system. Another scalings give the degenerate
continuum limits. The Wilson criterion for the confinement is ambiguous. The
asymptotics of the smeared Wilson loop integral for the large loop perimeters
is defined by the density of the loop smearing over a torus which is
transversal to the loop plane. When the initial torus radius tends to infinity
the correlation functions converge to the correlation functions of the R-gauge
Euclidean electrodynamics.Comment: latex, 6 page
Interaction of instantons in a gauge theory forcing their identical orientation
A gauge theory model in which there exists a specific interaction between
instantons is considered. An effective action describing this interaction
possesses a minimum when the instantons have identical orientation. The
considered interaction might provide a phase transition into the state where
instantons have a preferred orientation. This phase of the gauge-field theory
is important because it can give the description of gravity in the framework of
the gauge theory.Comment: 8 pages, Revte
On the problem of catastrophic relaxation in superfluid 3-He-B
In this Letter we discussed the parametric instability of texture of
homogeneous (in time) spin precession, explaining how spatial inhomogeneity of
the texture may change the threshold of the instability in comparison with
idealized spatial homogeneous case, considered in our JETP Letter \textbf{83},
530 (2006), cond-mat/0605386. This discussion is inspired by critical Comment
of I.A. Fomin (cond-mat/0606760) related to the above questions. In addition we
considered here results of direct numerical simulations of the full
Leggett-Takagi equation of motion for magnetization in superfluid 3He-B and
experimental data for magnetic field dependence of the catastrophic relaxation,
that provide solid support of the theory of this phenomenon, presented in our
2006 JETP Letter.Comment: 5 pages, 1 fig. included, JETP Lett. style, submitted to JETP Lett.
as response to Comment cond-mat/060676
Gate-controlled superconductivity in diffusive multiwalled carbon nanotube
We have investigated electrical transport in a diffusive multiwalled carbon
nanotube contacted using superconducting leads made of Al/Ti sandwich
structure. We find proximity-induced superconductivity with measured critical
currents up to I_cm = 1.3 nA, tunable by gate voltage down to 10 pA. The
supercurrent branch displays a finite zero bias resistance which varies as R_0
proportional to I_cm^-alpha with alpha=0.74. Using IV-characteristics of
junctions with phase diffusion, a good agreement is obtained with Josephson
coupling energy in the long, diffusive junction model of A.D Zaikin and G.F.
Zharkov (Sov. J. Low Temp. Phys. 7, 184 (1981)).Comment: 5 pages, 4 figure
Strongly anharmonic current-phase relation in ballistic graphene Josephson junctions
Motivated by a recent experiment directly measuring the current-phase
relation (CPR) in graphene under the influence of a superconducting proximity
effect, we here study the temperature dependence of the CPR in ballistic
graphene SNS Josephson junctions within the the self-consistent tight-binding
Bogoliubov-de Gennes (BdG) formalism. By comparing these results with the
standard Dirac-BdG method, where rigid boundary conditions are assumed at the
SN interfaces, we show on a crucial importance of both proximity effect and
depairing by current for the CPR. The proximity effect grows with temperature
and reduces the skewness of the CPR towards the harmonic result. In short
junctions () current depairing is also important and gives rise to a
critical phase over a wide range of temperatures and doping
levels.Comment: 7 pages, 4 figures. v2 contains very minor change
Direct photon spectrum and elliptic flow produced from Pb+Pb collisions at TeV at the CERN Large Hadron Collider within an integrated hydrokinetic model
The photon transverse momentum spectrum and its anisotropy from Pb+Pb
collisions at the CERN Large Hadron Collider energy TeV
are investigated within the integrated hydrokinetic model (iHKM). Photon
production is accumulated from the different processes at the various stages of
relativistic heavy ion collisions: from the primary hard photons of very early
stage of parton collisions to the thermal photons from equilibrated quark-gluon
and hadron gas stages. Along the way a hadronic medium evolution is treated in
two distinct, in a sense opposite, approaches: chemically equilibrated and
chemically frozen system expansion. Studying the centrality dependence of the
results obtained allows us to conclude that a relatively strong transverse
momentum anisotropy of thermal radiation is suppressed by prompt photon
emission which is an isotropic. We find out that this effect is getting
stronger as centrality increases because of the simultaneous increase in the
relative contribution of prompt photons in the soft part of the spectra. The
substantial results obtained in iHKM with nonzero viscosity () for
photon spectra and coefficients are mostly within the error bars of
experimental data, but there is some systematic underestimation of both
observables for the near central events. We claim that a situation could be
significantly improved if an additional photon radiation that accompanies the
presence of a deconfined environment is included. Since a matter of a
space-time layer where hadronization takes place is actively involved in
anisotropic transverse flow, both positive contributions to the spectra and
are considerable, albeit such an argument needs further research and
elaboration.Comment: 21 pages, 6 figure
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