# 28th Texas Symposium on Relativistic Astrophysics

13-18 December 2015
International Conference Centre Geneva
Europe/Zurich timezone

## Anisotropic Spherically Symmetric Collapsing Star From Higher Order Derivative Gravity Theory

15 Dec 2015, 18:25
3m
Level 2, Room 14 (International Conference Centre Geneva)

### Speaker

Dr Hossein Ghaffarnejad (Semnan University of IRAN)

### Description

Combinations of Lovelock polynomials $R^2,R_{\mu\nu}R^{\mu\nu}$ and $R_{\mu\nu\eta\delta}R^{\mu\nu\eta\delta}$ is added with Einstein-Hilbert action to obtain interior metric of an anisotropic spherically symmetric collapsing (ASSC) stellar cloud. We assume that time dependent interior metric of the ASSC cloud is flat Minkowski at beginning of the collapse. We solved linearized metric equation and obtained convergent series solutions for the interior metric components, mass density, radial, transverse and isotropic pressures, time dependent barotropic index and dimensionless anisotropic parameter. Ricci and Kretschmann scalars for our solutions are not singular at the beginning and duration of the collapse. Mathematical calculations predict that the collapsing cloud reach to its final state (compact object) and the collapse will be stopped at a finite time $t_C$. Also we obtain particular times $t_E$ and $t_A$ where the singularity and apparent horizon are formed. Singularity can not be observed by an external observer because of $t_E>t_A>t_C$.

### Primary author

Dr Hossein Ghaffarnejad (Semnan University of IRAN)