411 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
Inflation and Transition to a Slowly Accelerating Phase from S.S.B. of Scale Invariance
We consider the effects of adding a scale invariant term to the
action of the scale invariant model (SIM) studied previously by one of us
(E.I.G., Mod. Phys. Lett. A14, 1043 (1999)). The SIM belongs to the general
class of theories, where an integration measure independent of the metric is
introduced. To implement scale invariance (S.I.), a dilaton field is
introduced. The integration of the equations of motion associated with the new
measure gives rise to the spontaneous symmetry breaking (S.S.B) of S.I.. After
S.S.B. of S.I. in the model with the term, it is found that a non
trivial potential for the dilaton is generated. This potential contains two
flat regions: one associated with the Planck scale and with an inflationary
phase, while the other flat region is associated to a very small vacuum energy
(V.E.) and is associated to the present slowly accelerated phase of the
universe (S.A.PH). The smallness of the V.E. in the S.A.PH. is understood
through the see saw mechanism introduced in S.I.M.Comment: 22 pages, latex, three figures now in separate file
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