571 research outputs found
Band structure in classical field theory
Stability and instability bands in classical mechanics are well-studied in
connection with systems such as described by the Mathieu equation. We examine
whether such band structure can arise in classical field theory in the context
of an embedded kink in 1+1 dimensions. The static embedded kink is unstable to
perturbations but we show that if the kink is dynamic it can exhibit stability
in certain parameter bands. Our results are relevant for estimating the
lifetimes of various embedded defects and, in particular, loops of electroweak
Z-string.Comment: 6 pages, 4 fig. Reference added, Fig. 3 updated with improved
numerical code, minor comments added. Version to be published in Phys. Rev.
Electroweak Strings, Zero Modes and Baryon Number
The Dirac equations for leptons and quarks in the background of an
electroweak string have zero mode solutions. If two loops of electroweak
string are linked, the zero modes on one of the loops interacts with the other
loop via an Aharanov-Bohm interaction. The effects of this interaction are
briefly discussed and it is shown that the fermions induce a baryon number on
linked loops of string. (Submitted to Proceedings of "Trends in
Astrophysics" Conference, Stockholm, 1994.)Comment: LaTeX using espcrc2.sty (version 2.5) (hit return on error messages),
3 page
Open/Closed String Topology and Moduli Space Actions via Open/Closed Hochschild Actions
In this paper we extend our correlation functions to the open/closed case.
This gives rise to actions of an open/closed version of the Sullivan PROP as
well as an action of the relevant moduli space. There are several unexpected
structures and conditions that arise in this extension which are forced upon us
by considering the open sector. For string topology type operations, one cannot
just consider graphs, but has to take punctures into account and one has to
restrict the underlying Frobenius algebras. In the moduli space, one first has
to pass to a smaller moduli space which is closed under open/closed duality and
then consider covers in order to account for the punctures
Electroweak String Configurations with Baryon Number
In the context of electroweak strings, the baryon number anomaly equation may
be reinterpreted as a conservation law for baryon number minus helicity. Since
the helicity is a sum of the link and twist numbers, linked or twisted loops of
electroweak string carry baryon number. We evaluate the change in the baryon
number obtained by delinking loops of electroweak string and show that
twisted electroweak string segments may be regarded as extended sphalerons. We
also suggest an alternative scenario for electroweak baryogenesis.Comment: 11 pages, figure available on request. Added discussion of
string-sphaleron connection for non-vanishing Weinberg angle and shortened
discussion on formation of linked configuration
Spectra of Magnetic Fields Injected during Baryogenesis
Helical magnetic fields are injected into the cosmic medium during
cosmological baryogenesis and can potentially provide a useful probe of the
early universe. We construct a model to study the injection process during a
first order phase transition and to determine the power spectra of the injected
magnetic field. By Monte Carlo simulations we evaluate the Fourier space
symmetric and helical power spectra of the magnetic field at the time the phase
transition completes. The spectra are peaked at the scale given by the inverse
size of bubbles at percolation and with a comparable width. These injected
magnetic fields set the initial conditions for further cosmological
magneto-hydrodynamical evolution.Comment: 8 pages, 9 figures; revised discussion and added new references;
version accepted for publication in PR
Helical Magnetic Fields from Sphaleron Decay and Baryogenesis
Many models of baryogenesis rely on anomalous particle physics processes to
give baryon number violation. By numerically evolving the electroweak equations
on a lattice, we show that baryogenesis in these models creates helical cosmic
magnetic fields. After a transitory period, electroweak dynamics is found to
conserve the Chern-Simons number and the total electromagnetic helicity. We
argue that baryogenesis could lead to magnetic fields of nano-Gauss strength
today on astrophysical length scales. In addition to being astrophysically
relevant, such helical magnetic fields can provide an independent probe of
baryogenesis and CP violation in particle physics.Comment: 4 pages, 1 figure. Added references, fixed typo
Electroweak Dyons
We consider dyon configurations in the standard electroweak model. In the
presence of a term and no fermions, the usual result is obtained for the electric charge spectrum. The effect of
including standard model fermions is discussed qualitatively.Comment: 14 pages, TUTP-94-1
Topological Incarnations of Electroweak Defects
We propose a criterion to classify hybrid defects occurring in field
theoretic models such as the standard electroweak model. This criterion leads
us to consider the minimal extension of the electroweak model in which
electroweak magnetic monopoles and -strings are topological. We briefly
discuss the cosmology of such defects.Comment: 12 pages + 1 figure; LaTe
Examples of Embedded Defects (in Particle Physics and Condensed Matter)
We present a series of examples designed to clarify the formalism of the
companion paper `Embedded Vortices'. After summarising this formalism in a
prescriptive sense, we run through several examples: firstly, deriving the
embedded defect spectrum for Weinberg-Salam theory, then discussing several
examples designed to illustrate facets of the formalism. We then calculate the
embedded defect spectrum for three physical Grand Unified Theories and conclude
with a discussion of vortices formed in the superfluid He-A phase
transition.Comment: final corrections. latex fil
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