103 research outputs found
Gravity as a Gauge Theory of Translations
The Poincar\'e group can be interpreted as the group of isometries of a
minkowskian space. This point of view suggests to consider the group of
isometries of a given space as the suitable group to construct a gauge theory
of gravity. We extend these ideas to the case of maximally symmetric spaces to
reach a realistic theory including the presence of a cosmological constant.
Introducing the concept of "minimal tetrads" we deduce Einstein gravity in the
vacuum as a gauge theory of translations.Comment: 14 pages. LaTeX 2
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
The dynamical nature of time
It is usually assumed that the "" parameter in the equations of dynamics
can be identified with the indication of the pointer of a clock. Things are not
so easy, however. In fact, since the equations of motion can be written in
terms of but also of , being any well behaved function, each
one of those infinite parametric times is as good as the Newtonian one to
study classical dynamics. Here we show that the relation between the
mathematical parametric time in the equations of dynamics and the physical
dynamical time that is measured with clocks is more complex and subtle
than usually assumed. These two times, therefore, must be carefully
distinguished since their difference may have significant consequences.
Furthermore, we show that not all the dynamical clock-times are necessarily
equivalent and that the observational fingerprint of this non-equivalence has
the same form as that of the Pioneer anomaly.Comment: 13 pages, no figure
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
Gravitational contribution to fermion masses
In the context of a nonlinear gauge theory of the Poincar\'e group, we show
that covariant derivatives of Dirac fields include a coupling to the
translational connections, manifesting itself in the matter action as a
universal background mass contribution to fermions.Comment: revtex4, 9 pages, no figures, to be published in Eur.Phys.J.C, 200
The role of translational invariance in non linear gauge theories of gravity
The internal structure of the tetrads in a Poincar\'e non linear gauge theory
of gravity is considered. Minkowskian coordinates becomes dynamical degrees of
freedom playing the role of Goldstone bosons of the translations. A critical
length allowing a covariant expansion similar to the weak field approach is
deduced, the zeroth order metric being maximally symmetric (Minkowskian in some
cases).Comment: 17 pages, LaTe
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