14 research outputs found
Motion in gauge theories of gravity
A description of motion is proposed, adapted to the composite bundle
interpretation of Poincar\'e Gauge Theory. Reference frames, relative positions
and time evolution are characterized in gauge-theoretical terms. The approach
is illustrated by an appropriate formulation of the familiar example of orbital
motion induced by Schwarzschild spacetime.Comment: 24 pages, 6 figures, revised version with minor change
Dynamically broken Anti-de Sitter action for gravity
Due to a suitable Higgs mechanism, a standard Anti-de Sitter gauge theory
becomes spontaneously broken. The resulting Lorentz invariant gravitational
action includes the Hilbert-Einstein term of ordinary Einstein-Cartan gravity
with cosmological constant, plus contributions quadratic in curvature and
torsion, and a scalar Higgs sector.Comment: 7 Revtex pages, no figure
A cosmological model in Weyl-Cartan spacetime
We present a cosmological model for early stages of the universe on the basis
of a Weyl-Cartan spacetime. In this model, torsion and
nonmetricity are proportional to the vacuum polarization.
Extending earlier work of one of us (RT), we discuss the behavior of the cosmic
scale factor and the Weyl 1-form in detail. We show how our model fits into the
more general framework of metric-affine gravity (MAG).Comment: 19 pages, 5 figures, typos corrected, uses IOP style fil
Translations and dynamics
We analyze the role played by local translational symmetry in the context of
gauge theories of fundamental interactions. Translational connections and
fields are introduced, with special attention being paid to their universal
coupling to other variables, as well as to their contributions to field
equations and to conserved quantities.Comment: 22 Revtex pages, no figures. Published version with minor correction
Nonlinear gauge realization of spacetime symmetries including translations
We present a general scheme for the nonlinear gauge realizations of space-time groups on coset spaces of the groups considered. In order to show the relevance of the method for the rigorous treatment of the translations in gravitational gauge theories, we apply it in particular to the affine group. This is an illustration of the family of spacetime symmetries having the form of a semidirect product H ⊗ T, where H is the stability subgroup and T are the translations. The translational component of the connection behaves like a true tensor under H when coset realizations are involved. c Plenum Publishing CorporationPeer Reviewe
The Husain-Kuchar Model: Time Variables and Non-degenerate Metrics
We study the Husain-Kuchar model by introducing a new action principle
similar to the self-dual action used in the Ashtekar variables approach to
Quantum Gravity. This new action has several interesting features; among them,
the presence of a scalar time variable that allows the definition of geometric
observables without adding new degrees of freedom, the appearance of a natural
non-degenerate four-metric and the possibility of coupling ordinary matter.Comment: LaTeX, 22 pages, accepted for publication in Phys. Rev.
Hyperfluid - a model of classical matter with hypermomentum
A variational theory of a continuous medium is developed the elements of
which carry momentum and hypermomentum (hyperfluid). It is shown that the
structure of the sources in metric-affine gravity is predetermined by the
conservation identities and, when using the Weyssenhoff ansatz, these
explicitly yield the hyperfluid currents.Comment: plain Tex, 11 pages, no figure