153 research outputs found
Birefringent Electroweak Textures
The behaviour of electromagnetic waves propagating through an electroweak
homilia string network is examined. This string network is topologically stable
as a cosmic texture, and is characterized by the spatial variation of the
isospin rotation of the Higgs field. As a consequence the photon field couples
to the intermediate vector bosons, producing a finite range electromagnetic
field. It is found that the propagation speed of the photon depends on its
polarization vector, whence an homilia string network acts as a birefringent
medium. We estimate the birefringent scale for this texture and show that it
depends on the frequency of the electromagnetic wave and the length scale of
the homilia string network.Comment: 10 page
O(4) texture with a cosmological constant
We investigate O(4) textures in a background with a positive cosmological
constant. We find static solutions which co-move with the expanding background.
There exists a solution in which the scalar field is regular at the horizon.
This solution has a noninteger winding number smaller than one. There also
exist solutions in which scalar-field derivatives are singular at the horizon.
Such solutions can complete one winding within the horizon. If the winding
number is larger than some critical value, static solutions including the
regular one are unstable under perturbations.Comment: 25 pages, revtex, 6 eps figure
Reply to "Comment on 'Gravitating Magnetic Monopole in the Global Monopole Spacetime' "
In this Reply I present some arguments in favor of the stability of the
topological defect composed by global and magnetic monopoles.Comment: 1 page, no figures. Revised version improves the theoretical analysis
about electrostatic self-interaction in the global monopole spacetim
Is baryon number violated when electroweak strings intercommute?
We reexamine the self-helicity and the intercommutation of electroweak
strings. A plausible argument for baryon number conservation when electroweak
strings intercommute is presented. The connection between a segment of
electroweak strings and a sphaleron is also discussed.Comment: CALT-68-1948, 11 pages, 5 figures available upon request. Replaced
with revised version. (Request should be sent to [email protected]
Z-Vortex Percolation in the Electroweak Crossover Region
We study the statistical properties of Z-vortices and Nambu monopoles in the
3D SU(2) Higgs model for a Higgs mass M_H \approx 100 GeV near and above the
crossover temperature, where these defects are thermally excited. Although
there is no phase transition at that strong selfcoupling, we observe that the
Z-vortices exhibit the percolation transition that has been found recently to
accompany the first order thermal transition that exists at smaller Higgs mass.
Above the crossover temperature percolating networks of Z-vortex lines are
ubiquitous, whereas vortices form a dilute gas of closed vortex loops and
(Nambu) monopolium states on the low-temperature side of the crossover. The
percolation temperature turns out to be roughly independent of the lattice
spacing. We find that the Higgs modulus is smaller (the gauge action is larger)
inside the vortices, compared to the bulk average. This correlation becomes
very strong on the low-temperature side. The percolation transition is a
prerequisite of some string mediated baryon number generation scenarios.Comment: 16 pages, LaTeX, 12 figures, epsf.sty needed; final version to appear
in Phys. Lett.
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
Embedded Topological Defects in Hot Electroweak Theory: a Lattice Study
We study the properties of Nambu monopoles and Z-vortices in the 3D lattice
SU(2) Higgs theory which represents the Standard Model at high temperature. We
show that the densities of the Nambu monopoles and the Z-vortices are O(1) in
the symmetric phase and generically small in the Higgs phase. Near to the
critical Higgs mass and in the vicinity of the phase transition the densities
are no more negligible in the broken phase. The percolation probability of the
Z-vortex lines is found as a new disorder parameter for this phase transition.
We conclude that the transition to the symmetric phase is accompanied by
Z-vortex condensation. Simulations comparing elementary and extended vortices
and monopoles at different \beta_G values, aiming to show that the density of
vortices and monopoles of fixed physical size might have a well-defined
continuum limit, gives encouraging but so far inconclusive results.Comment: 13 pages, LaTeX, 8 figures, epsf.sty needed; revision: minor changes
and reference adde
Collapse of topological texture
We study analytically the process of a topological texture collapse in the
approximation of a scaling ansatz in the nonlinear sigma-model. In this
approximation we show that in flat space-time topological texture eventually
collapses while in the case of spatially flat expanding universe its fate
depends on the rate of expansion. If the universe is inflationary, then there
is a possibility that texture will expand eternally; in the case of exponential
inflation the texture may also shrink or expand eternally to a finite limiting
size, although this behavior is degenerate. In the case of power law
noninflationary expansion topological texture eventually collapses. In a cold
matter dominated universe we find that texture which is formed comoving with
the universe expansion starts collapsing when its spatial size becomes
comparable to the Hubble size, which result is in agreement with the previous
considerations. In the nonlinear sigma-model approximation we consider also the
final stage of the collapsing ellipsoidal topological texture. We show that
during collapse of such a texture at least two of its principal dimensions
shrink to zero in a similar way, so that their ratio remains finite. The third
dimension may remain finite (collapse of cigar type), or it may also shrink to
zero similar to the other two dimensions (collapse of scaling type), or shrink
to zero similar to the product of the remaining two dimensions (collapse of
pancake type).Comment: 23 pages, LaTeX, to be published in Phys. Rev.
Textures and Newtonian Gravity
Newtonian theory is used to study the gravitational effects of a texture, in
particular the formation of massive structures.Comment: 4 pages, 4 ps figures, REVTEX, accepted for publication in PR
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