Talk detail

Participant	Kamenshchik, Alexander
Institution	University of Bologna - via Irnerio 46 - Bologna - Bologna - Italy

Session	CM2	Accepted		Order	Time
Talk	Oral abstract	Title	Dynamical Dark Energy and Spontaneously Generated Gravity
Co-authors
Abstract	We study the cosmological evolution of an induced gravity model with a scale symmetry breaking potential for the scalar field. The radiation to matter transition, following inflation and reheating, influences the dynamics of such a field through its non minimal coupling. We illustrate how, under certain conditions on the potential, such a dynamics can lead to a suitable amount of dark energy explaining the present accelerated expansion.

Session	CM4	Accepted		Order	Time
Talk	Oral abstract	Title	Classical and quantum Big Brake cosmology for scalar field and tachyonic models.
Co-authors
Abstract	We have studied a relation between the cosmological singularities in classical and quantum theory, comparing the classical and quantum dynamics in two models possessing the Big Brake singularity - the model based on a scalar field and one based on a tachyon field model. It was shown that in the tachyon model, the wave function of the universe is not obliged to vanish at the values of the variables, corresponding to the appearance of the classical Big Brake singularity.

Session	GT2	Accepted		Order	Time
Talk	Oral abstract	Title	The paradox of soft singularity crossing and its resolution by distributional cosmological quantities
Co-authors
Abstract	A cosmological model of a flat Friedmann universe filled with a mixture of anti-Chaplygin gas and dust-like matter exhibits a future soft singularity, where the pressure of the anti-Chaplygin gas diverges (while its energy density vanishes). Despite infinite tidal forces the geodesics pass through the singularity. Due to the dust component, the Hubble parameter has a non-zero value at the encounter with the singularity, therefore the dust implies further expansion. With continued expansion however, the energy density and the pressure of the anti-Chaplygin gas would become ill-defined, hence from the point of view of the anti-Chaplygin gas only a contraction is allowed. Paradoxically, the universe in this cosmological model would have to expand and contract simultaneously. We solve the paradox by redefining the anti-Chaplygin gas in a distributional sense. Then a contraction could follow the expansion phase at the singularity at the price of a jump in the Hubble parameter. Although such an abrupt change is not common in any cosmological evolution, we explicitly show that the set of Friedmann, Raychaudhuri and continuity equations are all obeyed both at the singularity and in its vicinity.