Relativistic rigid systems and the cosmic expansion

Luciano Combi, Gustavo Romero.

Serie: Trabajos publicados del IAR ; no. 1568

Resumen: We analyze the necessary conditir a body to remain rigid in an expanding cding cosmological Universe. First, we establish the main theorems and definitions for having a rigid body in a general spacetime as well as the new concept of quasilocal rigidity. We apply the obtained results to a homogeneous universe exploring the differences with flat spacetime. We discuss how the concept of rigid body helps to understand the expansion of space in cosmology. Finally, using a rigid system as a reference frame, we calculate the gravitational energy, and we compare it with previous results in the literature.