3,193 research outputs found
Embedded Vortices
We present a discussion of embedded vortices in general Yang-Mills theories.
The origin of a family structure of solutions is shown to be group theoretic in
nature and a procedure for its determination is developed. Vortex stability can
be quantified into three types: Abelian topological stability, non-Abelian
topological stability, and dynamical stability; we relate these to the family
structure of vortices, in particular discussing how Abelian topological and
dynamical stability are related. The formalism generally encompasses embedded
domain walls and embedded monopoles also.Comment: final corrections. latex fil
wormholes and topological charge
I investigate solutions to the Euclidean Einstein-matter field equations with
topology in a theory with a massless periodic scalar
field and electromagnetism. These solutions carry winding number of the
periodic scalar as well as magnetic flux. They induce violations of a
quasi-topological conservation law which conserves the product of magnetic flux
and winding number on the background spacetime. I extend these solutions to a
model with stable loops of superconducting cosmic string, and interpret them as
contributing to the decay of such loops.Comment: 18 pages (includes 6 figs.), harvmac and epsf, CU-TP-62
The Dual Formulation of Cosmic Strings and Vortices
We study four dimensional systems of global, axionic and local strings. By
using the path integral formalism, we derive the dual formulation of these
systems, where Goldstone bosons, axions and missive vector bosons are described
by antisymmetric tensor fields, and strings appear as a source for these tensor
fields. We show also how magnetic monopoles attached to local strings are
described in the dual formulation. We conclude with some remarks.Comment: 18 pages, CU-TP-588 and CERN-TH.6780/9
Constraints on Supersymmetric Grand Unified Theories from Cosmology
Within the context of SUSY GUTs, cosmic strings are generically formed at the
end of hybrid inflation. However, the WMAP CMB measurements strongly constrain
the possible cosmic strings contribution to the angular power spectrum of
anisotropies. We investigate the parameter space of SUSY hybrid (F- and D-
term) inflation, to get the conditions under which theoretical predictions are
in agreement with data. The predictions of F-term inflation are in agreement
with data, only if the superpotential coupling is small. In
particular, for SUSY SO(10), the upper bound is \kappa\lsim 7\times 10^{-7}.
This fine tuning problem can be lifted if we employ the curvaton mechanism, in
which case \kappa\lsim 8\times 10^{-3}; higher values are not allowed by the
gravitino constraint. The constraint on is equivalent to a constraint
on the SSB mass scale , namely M \lsim 2\times 10^{15} GeV. The study of
D-term inflation shows that the inflaton field is of the order of the Planck
scale; one should therefore consider SUGRA. We find that the cosmic strings
contribution to the CMB anisotropies is not constant, but it is strongly
dependent on the gauge coupling and on the superpotential coupling
. We obtain g\lsim 2\times 10^{-2} and \lambda \lsim 3\times
10^{-5}. SUGRA corrections induce also a lower limit for .
Equivalently, the Fayet-Iliopoulos term must satisfy \sqrt\xi \lsim
2\times 10^{15} GeV. This constraint holds for all allowed values of .Comment: 32 pages, 7 figures. To match published versio
Vortons in the SO(5) model of high temperature superconductivity
It has been shown that superconducting vortices with antiferromagnetic cores
arise within Zhang's SO(5) model of high temperature supercondictivity. Similar
phenomena where the symmetry is not restored in the core of the vortex was
discussed by Witten in the case of cosmic strings. It was also suggested that
such strings can form stable vortons, which are closed loops of such vortices.
Motivated by this analogy, in following we will show that loops of such
vortices in the SO(5) model of high T_c superconductivity can exist as
classically stable objects, stabilized by the presence of conserved charges
trapped on the vortex core. These objects carry angular momentum which
counteracts the effect of the string tension that causes the loops to shrink.
The existence of such quasiparticles, which are called vortons, could be
interesting for the physics of high temperature superconductors. We also
speculate that the phase transition between superconducting and
antiferromagnetic phases at zero external magnetic field when the doping
parameter changes is associated with vortons.Comment: 11 page
Drum vortons in high density QCD
Recently it was shown that high density QCD supports of number of topological
defects. In particular, there are U(1)_Y strings that arise due to K^0
condensation that occurs when the strange quark mass is relatively large. The
unique feature of these strings is that they possess a nonzero K^+ condensate
that is trapped on the core. In the following we will show that these strings
(with nontrivial core structure) can form closed loops with conserved charge
and currents trapped on the string worldsheet. The presence of conserved
charges allows these topological defects, called vortons, to carry angular
momentum, which makes them classically stable objects. We also give arguments
demonstrating that vortons carry angular momentum very efficiently (in terms of
energy per unit angular momentum) such that they might be the important degrees
of freedom in the cores of neutron stars.Comment: 11 pages, accepted for publication in Physical Review
Cosmological Consequences of Slow-Moving Bubbles in First-Order Phase Transitions
In cosmological first-order phase transitions, the progress of true-vacuum
bubbles is expected to be significantly retarded by the interaction between the
bubble wall and the hot plasma. We examine the evolution and collision of
slow-moving true-vacuum bubbles. Our lattice simulations indicate that phase
oscillations, predicted and observed in systems with a local symmetry and with
a global symmetry where the bubbles move at speeds less than the speed of
light, do not occur inside collisions of slow-moving local-symmetry bubbles. We
observe almost instantaneous phase equilibration which would lead to a decrease
in the expected initial defect density, or possibly prevent defects from
forming at all. We illustrate our findings with an example of defect formation
suppressed in slow-moving bubbles. Slow-moving bubble walls also prevent the
formation of `extra defects', and in the presence of plasma conductivity may
lead to an increase in the magnitude of any primordial magnetic field formed.Comment: 10 pages, 7 figures, replaced with typos corrected and reference
added. To appear in Phys. Rev.
Phase Equilibration and Magnetic Field Generation in U(1) Bubble Collisions
We present the results of lattice computations of collisions of two expanding
bubbles of true vacuum in the Abelian Higgs model with a first-order phase
transition. New time-dependent analytical solutions for the Abelian field
strength and the phase of the complex field are derived from initial conditions
inferred from linear superposition and are shown to be in excellent agreement
with the numerical solutions especially for the case where the initial phase
difference between the bubbles is small. With a step-function approximation for
the initial phase of the complex field, solutions for the Abelian field
strength and other gauge-invariant quantities are obtained in closed form.
Possible extensions of the solution to the case of the electroweak phase
transition and the generation of primordial magnetic fields are briefly
discussed.Comment: LaTeX, 41 pages, 6 figures, submitted to Physical Review
Situationally edited empathy: an effect of socio-economic structure on individual choice
Criminological theory still operates with deficient models of the offender as agent, and of social influences on the agentâs decision-making process. This paper takes one âemotionâ, empathy, which is theoretically of considerable importance in influencing the choices made by agents; particularly those involving criminal or otherwise harmful action. Using a framework not of rational action, but of ârationalised actionâ, the paper considers some of the effects on individual psychology of social, economic, political and cultural structure. It is suggested that the climate-setting effects of these structures promote normative definitions of social situations which allow unempathic, harmful action to be rationalised through the situational editing of empathy. The âcrime is normalâ argument can therefore be extended to include the recognition that the uncompassionate state of mind of the criminal actor is a reflection of the self-interested values which govern non-criminal action in wider society
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