6,026 research outputs found
Dynamical Symmetry Breaking in SYM Theories as a Non-Semiclassical Effect
We study supersymmetry breaking effects in N=1 SYM from the point of view of
quantum effective actions. Restrictions on the geometry of the effective
potential from superspace are known to be problematic in quantum effective
actions, where explicit supersymmetry breaking can and must be studied. On the
other hand the true ground state can be determined from this effective action,
only. We study whether some parts of superspace geometry are still relevant for
the effective potential and discuss whether the ground states found this way
justify a low energy approximation based on this geometry. The answer to both
questions is negative: Essentially non-semiclassical effects change the
behavior of the auxiliary fields completely and demand for a new interpretation
of superspace geometry. These non-semiclassical effects can break
supersymmetry.Comment: 37 pages, LaTex. Version 3: many important changes, extended
discussion of the topi
The role of domain walls on the vortex creep dynamics in unconventional superconducors
We investigate the influence of domain walls on the vortex dynamics in
superconductors with multi-component order parameters. We show that, due to
their complex structure domain walls can carry vortices with fractional flux
quanta. The decay of conventional vortices into fractional ones on domain walls
is examined. This decay presents an extraordinarily strong pinning mechanism
for vortices and turns domain walls occupied with pinned fractional vortices
into efficient barriers for the vortex motion. Therefore, domain walls can act
as fences for the flux flow, preventing the decay of the remnant magnetic flux
enclosed by them. Furthermore, the consequences of this property of domain
walls on the vortex dynamics are discussed in connection with observed noise in
the hysteresis cycle, using the Bean model of the critical vortex state. Based
on this picture experimental data in the unconventional superconductors
UPt, UThBe and SrRuO are interpreted.Comment: 18 pages, 9 figures, to appear in Progress of Theoretical Physic
Multifractal analysis of stress time series during ultrathin lubricant film melting
Melting of an ultrathin lubricant film confined between two atomically flat
surfaces is we studied using the rheological model for viscoelastic matter
approximation. Phase diagram with domains, corresponding to sliding, dry, and
two types of friction regimes has been built taking into account
additive noises of stress, strain, and temperature of the lubricant. The stress
time series have been obtained for all regimes of friction using the
Stratonovich interpretation. It has been shown that self-similar regime of
lubricant melting is observed when intensity of temperature noise is much
larger than intensities of strain and stress noises. This regime is defined by
homogenous distribution, at which characteristic stress scale is absent. We
study stress time series obtained for all friction regimes using multifractal
detrended fluctuation analysis. It has been shown that multifractality of these
series is caused by different correlations that are present in the system and
also by a power-law distribution. Since the power-law distribution is related
to small stresses, this case corresponds to self-similar solid-like lubricant.Comment: 22 pages, 10 figures, 41 reference
Resonantly driven wobbling kinks
The amplitude of oscillations of the freely wobbling kink in the
theory decays due to the emission of second-harmonic radiation. We study the
compensation of these radiation losses (as well as additional dissipative
losses) by the resonant driving of the kink. We consider both direct and
parametric driving at a range of resonance frequencies. In each case, we derive
the amplitude equations which describe the evolution of the amplitude of the
wobbling and the kink's velocity. These equations predict multistability and
hysteretic transitions in the wobbling amplitude for each driving frequency --
the conclusion verified by numerical simulations of the full partial
differential equation. We show that the strongest parametric resonance occurs
when the driving frequency equals the natural wobbling frequency and not double
that value. For direct driving, the strongest resonance is at half the natural
frequency, but there is also a weaker resonance when the driving frequency
equals the natural wobbling frequency itself. We show that this resonance is
accompanied by translational motion of the kink.Comment: 19 pages in a double-column format; 8 figure
A Generalization of the Hopf-Cole Transformation
A generalization of the Hopf-Cole transformation and its relation to the
Burgers equation of integer order and the diffusion equation with quadratic
nonlinearity are discussed. The explicit form of a particular analytical
solution is presented. The existence of the travelling wave solution and the
interaction of nonlocal perturbation are considered. The nonlocal
generalizations of the one-dimensional diffusion equation with quadratic
nonlinearity and of the Burgers equation are analyzed
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