Nathan F. Lepora

Embedded defects and symmetry breaking in flipped SU(5).

We explicitly show the analogy between the symmetry-breaking scheme for the GUT flipped SU(5) with that of the Weinberg-Salam theory of electroweak interactions. This allows us to construct the embedded defect spectrum of the flipped SU(5) theory. We find that the spectrum consists of twelve gauge-equivalent unstable leptoquark strings, which are analogous to W strings in electroweak theory, and another string that is gauge inequivalent to the leptoquark strings which we call the ``V string. The V string is analogous to the Z string of electroweak theory, correspondingly admitting a stable semilocal limit. Using data on the running coupling constants we indicate that in the nonsupersymmetric case V strings can be stable for part of the physically viable parameter space. Cosmological consequences are briefly discussed. textcopyright{} 1995 The American Physical Society.

Classifying Vortex Solutions to Gauge Theories

We classify the spectrum, family structure and stability of Nielsen-Olesen vortices embedded in a larger gauge group when the vacuum manifold is related to a symmetric space.

Electroweak Vacuum Geometry

We analyse symmetry breaking in the Weinberg-Salam model paying particular attention to the underlying geometry of the theory. In this context we find two natural metrics upon the vacuum manifold: an isotropic metric associated with the scalar sector, and a squashed metric associated with the gauge sector. Physically, the interplay between these metrics gives rise to many of the non-perturbative features of Weinberg-Salam theory.

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 3 He-A phase transition.

Gauge interactions in the dual standard model

We present a geometric argument for the transformation properties of SU(5) ? SU(3) > C ? SU(2)I ? U(1)Y/6) monopoles under the residual gauge symmetry. This strongly supports the proposal that monopoles of the dual standard model interact via a gauge theory of the standard model symmetry group, with the monopoles having the same spectrum as the standard model fermions.

Gauge unification within the dual standard model

We calculate the gauge couplings in the dual standard model. These values are consistent with an associated GeV mass scale, and predict the weak mixing angle to be sin 2θw(MZ) ~ 0.22.