130,798 research outputs found
Efficient structural symmetry breaking for constraint satisfaction problems
Symmetry breaking for constraint satisfaction
problems (CSPs) has attracted considerable attention
in recent years. Various general schemes have been proposed to eliminate symmetries. In general, these schemes may take exponential space or time to eliminate all the symmetries. We identify several classes of CSPs that encompass many practical problems and for which symmetry breaking for various forms of value and variable interchangeability is tractable using dedicated search procedures or symmetry-breaking constraints that allow nogoods and their symmetrically equivalent solutions to be stored and checked efficiently
Chiral Vortons and Cosmological Constraints on Particle Physics
We investigate the cosmological consequences of particle physics theories
that admit stable loops of current-carrying string - vortons. In particular, we
consider chiral theories where a single fermion zero mode is excited in the
string core, such as those arising in supersymmetric theories with a D-term.
The resulting vortons formed in such theories are expected to be more stable
than their non-chiral cousins. General symmetry breaking schemes are considered
in which strings formed at one symmetry breaking scale become current-carrying
at a subsequent phase transition. The vorton abundance is estimated and
constraints placed on the underlying particle physics theories from
cosmological observations. Our constraints on the chiral theory are
considerably more stringent than the previous estimates for more general
theories.Comment: minor corrections made. This version will appear in PR
Cosmological constraints on pseudo-Nambu-Goldstone bosons
Particle physics models with pseudo-Nambu-Goldstone bosons (PNGBs) are characterized by two mass scales: a global spontaneous symmetry breaking scale, f, and a soft (explicit) symmetry breaking scale, Lambda. General model insensitive constraints were studied on this 2-D parameter space arising from the cosmological and astrophysical effects of PNGBs. In particular, constraints were studied arising from vacuum misalignment and thermal production of PNGBs, topological defects, and the cosmological effects of PNGB decay products, as well as astrophysical constraints from stellar PNGB emission. Bounds on the Peccei-Quinn axion scale, 10(exp 10) GeV approx. = or less than f sub pq approx. = or less than 10(exp 10) to 10(exp 12) GeV, emerge as a special case, where the soft breaking scale is fixed at Lambda sub QCD approx. = 100 MeV
Inflation From Symmetry Breaking Below the Planck Scale
We investigate general scalar field potentials \hbox{}
for inflationary cosmology arising from spontaneous symmetry breaking. We find
that potentials which are dominated by terms of order with \hbox{} can satisfy observational constraints at an arbitrary symmetry breaking
scale. Of particular interest, the spectral index of density fluctuations is
shown to be independent of the specific form of the potential, depending only
on the order of the lowest non-vanishing derivative of near its
maximum. The results of a model with a broken symmetry illustrate
these features.Comment: Submitted to Phys. Rev. Letters. 7 Pages, REVTeX. No figure
Progress on symmetry breaking and generational mixing in topcolor-assisted technicolor
Topcolor-assisted technicolor provides a dynamical explanation for electroweak and flavor symmetry breaking and for the large mass of the top quark without unnatural fine tuning. I briefly review the basics of topcolor-assisted technicolor, including major constraints and a general approach to satisfying them. The main challenge to topcolor-assisted technicolor is to generate the observed mixing between heavy and light generations while breaking the strong topcolor interactions near 1 TeV. I argue that these phenomena, as well as electroweak symmetry breaking, are intimately connected and I present a scenario for them based on nontrivial patterns of technifermion condensation. I also exhibit a class of models realizing this scenario.First author draf
Minimal Flavor Constraints for Technicolor
We analyze the constraints on the the vacuum polarization of the standard
model gauge bosons from a minimal set of flavor observables valid for a general
class of models of dynamical electroweak symmetry breaking. We will show that
the constraints have a strong impact on the self-coupling and masses of the
lightest spin-one resonances. Our analysis is applicable to any four and higher
dimensional extension of the standard model reducing to models of dynamical
electroweak symmetry breaking.Comment: 26 pages, we have added appendix C and some references and corrected
some typo
The oblique S parameter in higgsless electroweak models
We present a one-loop calculation of the oblique S parameter within Higgsless
models of electroweak symmetry breaking. We have used a general effective
Lagrangian with at most two derivatives, implementing the chiral symmetry
breaking SU(2)_L x SU(2)_R -> SU(2)_{L+R} with Goldstones, gauge bosons and one
multiplet of vector and axial-vector resonances. The estimation is based on the
short-distance constraints and the dispersive approach proposed by Peskin and
Takeuchi.Comment: 5 pages, 2 figures. Talk given at QCD@work 2012, International
Workshop on Quantum Chromodynamics: Theory and Experiment, 18-21th June
(2012), Lecce (Italy
Nonabelian Confinement near Nontrivial Conformal Vacua
We discuss some aspects of confinement and dynamical symmetry breaking in the
so-called nonabelian Argyres-Douglas vacua, which occur very generally in
supersymmetric theories. These systems are characterized by strongly-coupled
nonabelian monopoles and dyons; confinement and dynamical symmetry breaking are
caused by the condensation of monopole composites, rather than by condensation
of single weakly-coupled monopoles. In general, there are strong constraints on
which kind of monopoles can appear as the infrared degrees of freedom, related
to the proper realization of the global symmetry of the theory. Drawing
analogies to some of the phenomena found here, we make a speculation on the
ground state of the standard QCD.Comment: 28 pages, Late
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