813 research outputs found
Gauged Lifshitz model with Chern-Simons term
We present a gauged Lifshitz Lagrangian including second and forth order
spatial derivatives of the scalar field and a Chern-Simons term, and study
non-trivial solutions of the classical equations of motion. While the
coefficient beta of the forth order term should be positive in order to
guarantee positivity of the energy, the coefficient alpha of the quadratic one
need not be. We investigate the parameter domains finding significant
differences in the field behaviors. Apart from the usual vortex field behavior
of the ordinary relativistic Chern-Simons-Higgs model, we find in certain
parameter domains oscillatory solutions reminiscent of the modulated phases of
Lifshitz systems.Comment: 13 pages, 6 figure
Fermion zero modes in the vortex background of a Chern-Simons-Higgs theory with a hidden sector
In this paper we study a dimensional system in which fermions are
coupled to the self-dual topological vortex in Chern-Simons
theory, where both gauge symmetries are spontaneously broken. We
consider two Abelian Higgs scalars with visible and hidden sectors coupled to a
fermionic field through three interaction Lagrangians, where one of them
violates the fermion number. Using a fine tuning procedure, we could obtain the
number of the fermionic zero modes which is equal to the absolute value of the
sum of the vortex numbers in the visible and hidden sectors.Comment: 10 page
Local and Effective Temperatures of Quantum Driven Systems
We introduce thermometers to define the local temperature of an electronic
system driven out-of-equilibrium by local AC fields. We also define the
effective temperature in terms of a local fluctuation-dissipation-relation. We
show that within the weak driving regime these two temperatures coincide. We
also discuss the behavior of the local temperature along the sample. We show
that it exhibits spatial fluctuations following an oscillatory pattern. For
weak driving, regions of the sample become heated, while others become cooled
as a consequence of the driving
Magnetic structures and Z_2 vortices in a non-Abelian gauge model
The magnetic order of the triangular lattice with antiferromagnetic
interactions is described by an SO(3) field and allows for the presence of Z2
magnetic vortices as defects. In this work we show how these Z2 vortices can be
fitted into a local SU(2) gauge theory. We propose simple Ansatzes for vortex
configurations and calculate their energies using well-known results of the
Abelian gauge model. We comment on how Dzyaloshinskii-Moriya interactions could
be derived from a non-Abelian gauge theory and speculate on their effect on non
trivial configurations
Numerical integration of the stochastic Landau-Lifshitz-Gilbert equation in generic time-discretisation schemes
We introduce a numerical method to integrate the stochastic
Landau-Lifshitz-Gilbert equation in spherical coordinates for generic
discretization schemes. This method conserves the magnetization modulus and
ensures the approach to equilibrium under the expected conditions. We test the
algorithm on a benchmark problem: the dynamics of a uniformly magnetized
ellipsoid. We investigate the influence of various parameters, and in
particular, we analyze the efficiency of the numerical integration, in terms of
the number of steps needed to reach a chosen long time with a given accuracy.Comment: 9 pages and 7 figure
Quenched dynamics of classical isolated systems: the spherical spin model with two-body random interactions or the Neumann integrable model
We study the Hamiltonian dynamics of the spherical spin model with
fully-connected two-body interactions drawn from a Gaussian probability
distribution. In the statistical physics framework, the potential energy is of
the so-called spherical disordered kind. Most importantly for our
setting, the energy conserving dynamics are equivalent to the ones of the
Neumann integrable system. We take initial conditions in thermal equilibrium
and we subsequently evolve the configurations with Newton dynamics dictated by
a different Hamiltonian. We identify three dynamical phases depending on the
parameters that characterise the initial state and the final Hamiltonian. We
obtain the {\it global} dynamical observables with numerical and analytic
methods and we show that, in most cases, they are out of thermal equilibrium.
We note, however, that for shallow quenches from the condensed phase the
dynamics are close to (though not at) thermal equilibrium. Surprisingly enough,
for a particular relation between parameters the global observables comply
Gibbs-Boltzmann equilibrium. We next set the analysis of the system with finite
number of degrees of freedom in terms of non-linearly coupled modes. We
evaluate the mode temperatures and we relate them to the frequency-dependent
effective temperature measured with the fluctuation-dissipation relation in the
frequency domain, similarly to what was recently proposed for quantum
integrable cases. Finally, we analyse the integrals of motion and we use
them to show that the system is out of equilibrium in all phases, even for
parameters that show an apparent Gibbs-Boltzmann behaviour of global
observables. We elaborate on the role played by these constants of motion in
the post-quench dynamics and we briefly discuss the possible description of the
asymptotic dynamics in terms of a Generalised Gibbs Ensemble
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