5 research outputs found
Graviweak Unification
The coupling of chiral fermions to gravity makes use only of the selfdual
SU(2) subalgebra of the (complexified) SO(3,1) algebra. It is possible to
identify the antiselfdual subalgebra with the SU(2)_L isospin group that
appears in the Standard Model, or with its right-handed counterpart SU(2)_R
that appears in some extensions. Based on this observation, we describe a form
of unification of the gravitational and weak interactions. We also discuss
models with fermions of both chiralities, the inclusion strong interactions,
and the way in which these unified models of gravitational and gauge
interactions avoid conflict with the Coleman-Mandula theorem.Comment: 18 pages, typos corrected and improved wordin
Chirality in unified theories of gravity
We show how to obtain a single chiral family of an SO(10) GUT, starting from
a Majorana-Weyl representation of a unifying ("GraviGUT") group SO(3,11), which
contains the gravitational Lorentz group SO(3,1). An action is proposed, which
reduces to the correct fermionic GUT action in the broken phase.Comment: 7 pages. Discussion clarified. Version matching the published on
Gravity-Yang-Mills-Higgs unification by enlarging the gauge group
We revisit an old idea that gravity can be unified with Yang-Mills theory by
enlarging the gauge group of gravity formulated as gauge theory. Our starting
point is an action that describes a generally covariant gauge theory for a
group G. The Minkowski background breaks the gauge group by selecting in it a
preferred gravitational SU(2) subgroup. We expand the action around this
background and find the spectrum of linearized theory to consist of the usual
gravitons plus Yang-Mills fields charged under the centralizer of the SU(2) in
G. In addition, there is a set of Higgs fields that are charged both under the
gravitational and Yang-Mills subgroups. These fields are generically massive
and interact with both gravity and Yang-Mills sector in the standard way. The
arising interaction of the Yang-Mills sector with gravity is also standard.
Parameters such as the Yang-Mills coupling constant and Higgs mass arise from
the potential function defining the theory. Both are realistic in the sense
explained in the paper.Comment: 61 pages, no figures (v2) some typos correcte
Unification of gravity, gauge fields, and Higgs bosons
We consider a diffeomorphism invariant theory of a gauge field valued in a
Lie algebra that breaks spontaneously to the direct sum of the spacetime
Lorentz algebra, a Yang-Mills algebra, and their complement. Beginning with a
fully gauge invariant action -- an extension of the Plebanski action for
general relativity -- we recover the action for gravity, Yang-Mills, and Higgs
fields. The low-energy coupling constants, obtained after symmetry breaking,
are all functions of the single parameter present in the initial action and the
vacuum expectation value of the Higgs.Comment: 12 pages, no figures. v2 minor correction
Gravity and unification: A review
We review various classical unified theories of gravity and other interactions that have appeared in the literature, paying special attention to scenarios in which spacetime remains four-dimensional, while an 'internal' space is enlarged. The starting point for each such unification scenario is a particular formalism for general relativity. We thus start by reviewing, besides the usual Einstein-Hilbert and Palatini formulations, the Einstein-Cartan, MacDowell-Mansouri and BF (both non-chiral and chiral) formulations. Each of these introduces some version of 'internal' bundle and a dynamical variable that ties the internal and tangent bundles. In each of these formulations there is also an independent connection in the 'internal' bundle. One can then study the effects of 'enlarging the internal space', which typically leads to a theory of gravity and Yang-Mills fields. We review what has been done in the literature on each of these unification schemes, and compare and contrast their achievements to those of the better developed Kaluza-Klein scenario