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Nathan F. Lepora

Publications and source records attributed to Nathan F. Lepora.

83 records · Page 5Linked to original sources
arXiv2001

Dualising the Dual Standard Model

We discuss how the dual standard model and the dualised standard model are complementary theories. That is, how their implications have no overlap, whilst together they explain most features of the standard model. To illustrate how these two theories might be combined we consider the dual standard model in a theta vacuum. Whilst there are issues to be considered, the dual standard model does then appear to become naturally dualised. This supports an origin of a dual formulation of the standard model through the properties of SU(5) solitons in a theta vacuum.

hep-ph↗
arXiv2001

Monopoles and Dyons in SU(5) Gauge Unification (with relation to a Dual Standard Model)

This article presents a fairly complete description of the monopoles and dyons arising from an SU(5) gauge unification of the standard model. Topics discussed include: the spectrum of SU(5) monopoles; their gauge equivalence structure; their spherical symmetry; the construction of dyons; global charge; the intrinsic angular momenta of scalar boson-monopole composites and monopole gauge excitations; and the effects of a theta vacuum. The relevance of each of these topics to constructing a dual description of the standard model with SU(5) solitons is discussed in detail.

hep-ph↗
arXiv2000

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 ${\sin^2 θ_w} (M_Z) \sim 0.22$.

hep-ph↗
arXiv2000

Gauge Interactions in the Dual Standard Model

We present a geometric argument for the transformation properties of SU(5) --> S(U(3) x U(2)) 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.

hep-ph↗
arXiv1999

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.

hep-th↗
arXiv1998

Cosmological Birefringence and the Microwave Background

We show that significant anisotropy in electromagnetic propagation generates a distinctive signature in the microwave background. The anisotropy may be determined by looking at the cross correlator of the $E$-mode and $B$-mode polarisation spectrum.

gr-qc↗
arXiv1998

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.

hep-ph↗
arXiv1998

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.

hep-ph↗
arXiv1996

Topological Inflation, without the Topology

We extend the `topological inflation' of Linde and Vilenkin to {\em unstable} monopoles. This allows the monopole to decay; not inflating eternally, as topological inflation demands. Such a situation happens naturally in some Grand Unified Theories --- such as supersymmetric flipped-$SU(5)$. We analyse analytically the dynamics of inflating monopoles to determine the equations governing the expansion, additionally recovering the bound on the scale of symmetry breaking found numerically by Sakai {\em et. al.} The latter half of this paper is devoted to the Cosmology of inflating unstable monopoles --- which is an example of an inhomogeneous cosmology. We describe how such a monopole may be formed and how long it inflates for --- finding it to be a random process. We then derive how cosmological parameters, such as density and temperature, are distributed at the end of inflation, and how the Universe reheats as the monopole decays. The general conclusion of this work is that such inflation creates a local region of relatively flat, homogenous and isotropic Universe surrounded by pre-GUT matter.

hep-ph↗
arXiv1995

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 theory flipped $SU(5)$. We find that the spectrum consists of twelve gauge-equivalent unstable Lepto-quark strings, which are analogous to W-strings in electroweak theory, and another string that is gauge inequivalent to the Lepto-quark 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 non-supersymmetric case V-strings can be stable for part of the physically-viable parameter space. Cosmological consequences are briefly discussed.

hep-ph↗