1,574 research outputs found
Spontaneous formation of domain wall lattices in two spatial dimensions
We show that the process of spontaneous symmetry breaking can trap a field
theoretic system in a highly non-trivial state containing a lattice of domain
walls. In one large compact space dimension, a lattice is inevitably formed. In
two dimensions, the probability of lattice formation depends on the ratio of
sizes L_x, L_y of the spatial dimensions. We find that a lattice can form even
if R=L_y/L_x is of order unity. We numerically determine the number of walls in
the lattice as a function of L_x and L_y.Comment: 6 pages, 6 figures. Background material added and minor corrections
included. Final version to be published in Phys. Rev.
The Thermodynamics of Cosmic String densities in U(1) Scalar Field Theory
We present a full characterization of the phase transition in U(1) scalar
field theory and of the associated vortex string thermodynamics in 3D. We show
that phase transitions in the string densities exist and measure their critical
exponents, both for the long string and the short loops. Evidence for a natural
separation between these two string populations is presented. In particular our
results strongly indicate that an infinite string population will only exist
above the critical temperature. Canonical initial conditions for cosmic string
evolution are show to correspond to the infinite temperature limit of the
theory.Comment: 4 pages, 4 figures, RevTe
Kinky Brane Worlds
We present a toy model for five-dimensional heterotic M-theory where bulk
three-branes, originating in 11 dimensions from M five-branes, are modelled as
kink solutions of a bulk scalar field theory. It is shown that the vacua of
this defect model correspond to a class of topologically distinct M-theory
compactifications. Topology change can then be analysed by studying the time
evolution of the defect model. In the context of a four-dimensional effective
theory, we study in detail the simplest such process, that is the time
evolution of a kink and its collision with a boundary. We find that the kink is
generically absorbed by the boundary thereby changing the boundary charge. This
opens up the possibility of exploring the relation between more complicated
defect configurations and the topology of brane-world models.Comment: 31 pages, Latex, 6 eps-figure
The Creation of Defects with Core Condensation
Defects in superfluid 3He, high-Tc superconductors, QCD colour superfluids
and cosmic vortons can possess (anti)ferromagnetic cores, and their
generalisations. In each case there is a second order parameter whose value is
zero in the bulk which does not vanish in the core. We examine the production
of defects in the simplest 1+1 dimensional scalar theory in which a second
order parameter can take non-zero values in a defect core. We study in detail
the effects of core condensation on the defect production mechanism.Comment: 9 pages, 7 figures, small corrections, 2 references added, final
version to be published in PR
Predicting the critical density of topological defects in O(N) scalar field theories
O(N) symmetric field theories describe many critical
phenomena in the laboratory and in the early Universe. Given N and ,
the dimension of space, these models exhibit topological defect classical
solutions that in some cases fully determine their critical behavior. For N=2,
D=3 it has been observed that the defect density is seemingly a universal
quantity at T_c. We prove this conjecture and show how to predict its value
based on the universal critical exponents of the field theory. Analogously, for
general N and D we predict the universal critical densities of domain walls and
monopoles, for which no detailed thermodynamic study exists. This procedure can
also be inverted, producing an algorithm for generating typical defect networks
at criticality, in contrast to the canonical procedure, which applies only in
the unphysical limit of infinite temperature.Comment: 4 pages, 3 figures, uses RevTex, typos in Eq.(11) and (14) correcte
Decoherence, tunneling and noise-activation in a double-potential well at high and zero temperature
We study the effects of the environment on tunneling in an open system
described by a static double-well potential. We describe the evolution of a
quantum state localized in one of the minima of the potential at , both in
the limits of high and zero environment temperature. We show that the evolution
of the system can be summarized in terms of three main physical phenomena,
namely decoherence, quantum tunneling and noise-induced activation, and we
obtain analytical estimates for the corresponding time-scales. These analytical
predictions are confirmed by large-scale numerical simulations, providing a
detailed picture of the main stages of the evolution and of the relevant
dynamical processes.Comment: Version to appear in Phys. Rev. E. 15 pages, 12 figures (low quality
due to upload size limitations). Good quality figures in a pdf file can be
downloaded from http://www.df.uba.ar/users/lombardo/tunne
On formation of domain wall lattices
We study the formation of domain walls in a phase transition in which an
S_5\times Z_2 symmetry is spontaneously broken to S_3\times S_2. In one compact
spatial dimension we observe the formation of a stable domain wall lattice. In
two spatial dimensions we find that the walls form a network with junctions,
there being six walls to every junction. The network of domain walls evolves so
that junctions annihilate anti-junctions. The final state of the evolution
depends on the relative dimensions of the simulation domain. In particular we
never observe the formation of a stable lattice of domain walls for the case of
a square domain but we do observe a lattice if one dimension is somewhat
smaller than the other. During the evolution, the total wall length in the
network decays with time as t^{-0.71}, as opposed to the usual t^{-1} scaling
typical of regular Z_2 networks.Comment: 7 pages, 4 figures. Minor changes, final version accepted for
publication in Phys. Rev.
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