### Conveners

#### 02 - Exact solutions

- Mustapha Ishak (The University of Texas at Dallas)

#### 02 - Exact solutions

- Mustapha Ishak (The University of Texas at Dallas)

Dr
Eloisa Bentivegna
(Università degli Studi di Catania)

12/14/15, 2:00 PM

Talk

Building accurate, multi-scale models of the Universe is a complex but necessary task in the era of precision cosmology, when observational data demands a thorough understanding of all effects which are expected to contribute at the 1% level, among which the full role of General Relativity. This task has recently been tackled with a variety of approaches, which range from the study of toy...

Brett Bochner
(Hofstra University)

12/14/15, 2:21 PM

Talk

The pre-homogenized very early universe generically experiences Mixmaster-like behavior as it approaches the Big Bang, featuring a sequence of anisotropically expanding Kasner epochs. Beyond drawing general conclusions about the transport of mass-energy in such environments, it would be helpful to obtain as much information as possible about the detailed propagation of energy in rapidly and...

Marco Bruni
(University of Portsmouth)

12/14/15, 2:42 PM

Talk

I introduce new exact solutions of the Szekeres-Szafron type describing voids on a Friedmann-Roberson-Walker background with w=constant equation of state. At least in the linear regime the inhomogeneities can be thought of as large scale perturbations of the background. Using these exact solutions the averaged quantities of the Buchert scheme can be calculated exactly. I show that in general...

Dr
Chandrachur Chakraborty
(Tata Institute of Fundamental Research , Mumbai , INDIA)

12/14/15, 3:03 PM

Talk

The exact Lense-Thirring precession frequencies for Kerr, Kerr–Taub–NUT,Taub–NUT, Plebanski-Demianski spacetimes are explicitly derived. Remarkably, in the case of the zero angular momentum Taub–NUT spacetime, the frame-dragging effect is shown not to vanish, when considered for spinning test gyroscopes. In the case of the interior of the rotating neutron stars, the exact frame-dragging rate...

Mariusz Dabrowski
(University of Szczecin)

12/14/15, 3:24 PM

Talk

I will discuss the benefits of the conformally flat inhomogeneous pressure models of the universe. Then, I will present the results of checking these models against supernovae data for off-centers observers and against other data (BAO, CMB) for the centrally-placed observers. I will also comment on the possible advantage of these models in view of the recently given Green and Wald conditions...

Mikhail Katanaev
(Steklov Mathematical Institute, Moscow)

12/14/15, 4:35 PM

Talk

We give a simple example of space-time metric, illustrating that homogeneity and isotropy of space slices at all moments of time is not obligatory lifted to a full system of six Killing vector fields in space-time, thus it cannot be interpreted as a symmetry of a four dimensional metric. The metric depends on two arbitrary and independent functions of time. One of these functions is the usual...

Geraint Pratten
(University of Sussex)

12/14/15, 4:55 PM

Talk

In this talk I will review recent results regarding covariant, gauge-invariant perturbations to the scalar-tensor Schwarzschild black hole in the 1+1+2 formalism. I will discuss how we can introduce a set of master functions based on the Weyl tensor in order to cleanly decouple the evolution of tensor modes from the scalar modes. Relations to 2+2 and Newman-Penrose formalism will be briefly discussed.

Wessel Valkenburg
(Leiden University)

12/14/15, 5:15 PM

Talk

A repetition of the same high-resolution and large-volume observation, after ten or more years, gives access to the fourth dimension in observational cosmology, perpendicular to the light-cone. I discuss how various toy models can be distinguished by decomposing the long-time-difference maps into multipole vectors. A next-generation GAIA-like satellite with ten times GAIA's resolution, should...

Giuseppe Fanizza
(Università degli Studi di Bari "Aldo Moro")

12/14/15, 5:35 PM

Talk

The remarkable properties of the recently proposed geodesic light-cone (GLC) gauge allow to get some new interesting results to face the problem of inhomogeneities and their backreaction. Indeed, GLC simply consists of gauge fixing the metric tensor on the past light-cone of the observer. Thanks to this choice, several interesting physical observables, related to photons, can be evaluated...