38 research outputs found
Instability of a Nielsen-Olesen vortex embedded in the electroweak theory; 2, electroweak vortices and gauge equivalence
Vortex configurations in the electroweak gauge theory are investigated. Two gauge-inequivalent solutions of the field equations, the Z and W vortices, have previously been found. They correspond to embeddings of the abelian Nielsen-Olesen vortex solution into a U(1) subgroup of SU(2)xU(1). It is shown here that any electroweak vortex solution can be mapped into a solution of the same energy with a vanishing upper component of the Higgs field. The correspondence is a gauge equivalence for all vortex solutions except those for which the winding numbers of the upper and lower Higgs components add to zero. This class of solutions, which includes the W vortex, instead corresponds to a singular solution in the one-component gauge. The results, combined with numerical investigations, provide an argument against the existence of other vortex solutions in the gauge-Higgs sector of the Standard Model
One Loop Vaccum Polarization in a Locally de Sitter Background
We compute the one loop vacuum polarization from massless, minimally coupled
scalar QED in a locally de Sitter background. Gauge invariance is maintained
through the use of dimensional regularization, whereas conformal invariance is
explicitly broken by the scalar kinetic term as well as through the conformal
anomaly. A fully renormalized result is obtained. The one loop corrections to
the linearized, effective field equations do not vanish when evaluated
on-shell. In fact the on-shell one loop correction depends quadratically on the
inflationary scale factor, similar to a photon mass. The contribution from the
conformal anomaly is insignificant by comparison.Comment: 31 pages, LaTeX 2 epsilon, 4 figure
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
Defect Statistics in the Two Dimensional Complex Ginsburg-Landau Model
The statistical correlations between defects in the two dimensional complex
Ginsburg-Landau model are studied in the defect-coarsening regime. In
particular the defect-velocity probability distribution is determined and has
the same high velocity tail found for the purely dissipative time-dependent
Ginsburg-Landau (TDGL) model. The spiral arms of the defects lead to a very
different behavior for the order parameter correlation function in the scaling
regime compared to the results for the TDGL model.Comment: 24 page
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.
Higgs Boson Mass in Models with Gauge-Mediated Supersymmetry Breaking
We present the predictions for the mass of the lightest Higgs boson in
models with gauge-mediated supersymmetry breaking as a function of the
SUSY-breaking scale. We include all radiative corrections up to two loops and
point out that if the CDF e+ e- two-photon event is interpreted in terms of
these models, then the lightest Higgs boson should be lighter than 110 GeV.Comment: revtex, 13 pages, 2 separate postscript figures, uses aps.sty,
prl.sty, preprint.sty. Submitted to Phys. Lett.
Microwave Background Signals from Tangled Magnetic Fields
An inhomogeneous cosmological magnetic field will create Alfven-wave modes
that induce a small rotational velocity perturbation on the last scattering
surface of the microwave background radiation. The Alfven-wave mode survives
Silk damping on much smaller scales than the compressional modes. This, in
combination with its rotational nature, ensures that there will be no sharp
cut-off in anisotropy on arc-minute scales. We estimate that a magnetic field
which redshifts to a present value of Gauss produces
temperature anisotropies at the 10 micro Kelvin level at and below 10 arc-min
scales. A tangled magnetic field, which is large enough to influence the
formation of large scale structure is therefore potentially detectable by
future observations.Comment: 5 pages, Revtex, no figure
Three-dimensional pattern formation, multiple homogeneous soft modes, and nonlinear dielectric electroconvection
Patterns forming spontaneously in extended, three-dimensional, dissipative
systems are likely to excite several homogeneous soft modes (
hydrodynamic modes) of the underlying physical system, much more than quasi
one- and two-dimensional patterns are. The reason is the lack of damping
boundaries. This paper compares two analytic techniques to derive the patten
dynamics from hydrodynamics, which are usually equivalent but lead to different
results when applied to multiple homogeneous soft modes. Dielectric
electroconvection in nematic liquid crystals is introduced as a model for
three-dimensional pattern formation. The 3D pattern dynamics including soft
modes are derived. For slabs of large but finite thickness the description is
reduced further to a two-dimensional one. It is argued that the range of
validity of 2D descriptions is limited to a very small region above threshold.
The transition from 2D to 3D pattern dynamics is discussed. Experimentally
testable predictions for the stable range of ideal patterns and the electric
Nusselt numbers are made. For most results analytic approximations in terms of
material parameters are given.Comment: 29 pages, 2 figure