263 research outputs found
Cosmological solutions from models with unified dark energy and dark matter and with inflaton field
Recently, few cosmological models with additional non-Riemannian volume
form(s) have been proposed. In this article we use Supernovae type Ia
experimental data to test one of these models which provides a unified
description of both dark energy via dynamically generated cosmological constant
and dark matter as a "dust" fluid due to a hidden nonlinear Noether symmetry.
It turns out that the model allows various scenarios of the future Universe
evolution and in the same time perfectly fits contemporary observational data.
Further, we investigate the influence of an additional inflaton field with a
step like potential. With its help we can reproduce the Universe inflation
epoch, matter dominated epoch and present accelerating expansion in a seamless
way. Interesting feature is that inflaton undergoes a finite change during its
evolution. It can be speculated that the inflaton asymptotic value is connected
to the vacuum expectation value of the Higgs field.Comment: 10 pages, 4 figures, prepared for the Proceedings of the XII.
International Workshop Lie Theory And Its Applications In Physics (2017
Scale Symmetry Breaking from the Dynamics of Maximal Rank Gauge Field Strengths
Scale invariant theories which contain maximal rank gauge field strengths (of
indices in dimensions) are studied. The integration of the equations of
motion of these gauge fields leads to the s.s.b. of scale invariance. The cases
in study are: i) the spontaneous generation of potentials in particle
mechanics in a theory that contains only potentials in the scale
invariant phase, ii) mass generation in scalar field theories iii) generation
of non trivial dilaton potentials in generally covariant theories, iv)
spontaneous generation of confining behavior in gauge theories. The possible
origin of these models is discussed.Comment: 14 pages, latex, no figures, references adde
Scale Invariance and Vacuum Energy
The possibility of mass in the context of scale-invariant, generally
covariant theories, is discussed. Scale invariance is considered in the context
of a gravitational theory where the action, in the first order formalism, is of
the form + where is
a density built out of degrees of freedom independent of the metric. For global
scale invariance, a "dilaton" has to be introduced, with non-trivial
potentials = in and =
in . This leads to non-trivial mass generation and
a potential for which is interesting for new inflation. Scale invariant
mass terms for fermions lead to a possible explanation of the present day
accelerated universe and of cosmic coincidences.Comment: Essay awarded an honorable mention in the 1999 Gravity Research
Foundation Competition, Published in Mod. Phys. Lett. A14: 1397 (1999
Strings and branes with a modified measure
In string theory, the consequences of replacing the measure of integration
in the Polyakov's action by where is
a density built out of degrees of freedom independent of the metric
defined in the string are studied. The string tension appears as
an integration constant of the equations of motion. The string tension can
change in different parts of the string due to the coupling of gauge fields and
point particles living in the string. The generalization to higher dimensional
extended objects is also studied. In this case there is no need of a fine tuned
cosmological term, in sharp contrast to the standard formulation of the
generalized Polyakov action for higher dimensional branes
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