Ornella Pantano

Dynamics of silent universes

We investigate the local non--linear dynamics of irrotational dust with vanishing magnetic part of the Weyl tensor,

General relativistic dynamics of irrotational dust: Cosmological implications.

H_{ab}

A local view of the observable universe.

. Once coded in the initial conditions, this dynamical restriction is respected by the relativistic evolution equations. Thus, the outcome of the latter are {\it exact solutions} for special initial conditions with

Second-order matter perturbations in a ΛCDM cosmology and non-Gaussianity

H_{ab}=0

A relativistic approach to gravitational instability in the expanding Universe: second-order Lagrangian solutions

, but with no symmetries: they describe inhomogeneous triaxial dynamics generalizing that of a fluid element in a Tolman--Bondi, Kantowski--Sachs or Szekeres geometry. A subset of these solutions may be seen as (special) perturbations of Friedmann models, in the sense that there are trajectories in phase--space that pass arbitrarily close to the isotropic ones. We find that the final fate of ever--expanding configurations is a spherical void, locally corresponding to a Milne universe. For collapsing configurations we find a whole family of triaxial attractors, with vanishing local density parameter

Zero‐metallicity stellar sources and the reionization epoch

\Omega

A cosmological hydrodynamic code based on the piecewise parabolic method

. These attractors locally correspond to Kasner vacuum solutions: there is a single physical configuration collapsing to a degenerate {\it pancake}, while the generic configuration collapses to a triaxial {\it spindle} singularity. These {\it silent universe} models may provide a fair representation of the universe on super horizon scales. Moreover, one might conjecture that the non--local information carried by

Evaporation of quark drops during the cosmological quark - hadron transition

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Physics thematic paths: laboratorial activities and historical scientific instruments

becomes negligible during the late highly non--linear stages of collapse, so that the attractors we find may give all of the relevant expansion or collapse configurations of irrotational dust.

Understanding first-year students’ curiosity and interest about physics—lessons learned from the HOPE project

The non-linear dynamics of cosmological perturbations of an irro- tational collisionless fluid is analyzed within General Relativity. Relativistic and Newtonian solutions are compared, stressing the different role of boundary conditions in the two theories. Cosmological implications of relativistic effects, already present at second order in perturbation theory, are studied and the dynamical role of the magnetic part of the Weyl tensor is elucidated.