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 $D$ indices in $D$ 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 $r^{-1}$ potentials in particle mechanics in a theory that contains only $r^{-2}$ 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

Stabilization of Neutral Thin Shells By Gravitational Effects From Electric Fields

We study the properties of a system consisting of an uncharged spherically symmetric two dimensional extended object which encloses a stationary point charge placed in the shell's center. We show that there can be a static and stable configuration for the neutral shell, using only the gravitational field of the charged source as a stabilizing mechanism. In particular, two types of shells are studied: a dust shell and a string gas shell. The dynamical possibilities are also analyzed, including the possibility of child universe creation.Comment: 5 pages, 1 figur

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 $S = \int L_{1} \Phi d^4x$ + $\int L_{2}\sqrt{-g}d^4x$ where $\Phi$ is a density built out of degrees of freedom independent of the metric. For global scale invariance, a "dilaton" $\phi$ has to be introduced, with non-trivial potentials $V(\phi)$ = $f_{1}e^{\alpha\phi}$ in $L_1$ and $U(\phi)$ = $f_{2}e^{2\alpha\phi}$ in $L_2$. This leads to non-trivial mass generation and a potential for $\phi$ 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