Térence Delsate, Jan Steinhoff
We formulate the Eddington inspired Born-Infeld theory recently reintroduced
by Banados and Ferreira in a form of an Einstein equation for the auxiliary
metric. In the case of a perfect fluid, the source seen by the auxiliary metric
is exactly a perfect fluid with an (apparently) modified equation of state.
This drastically simplifies the theory by decoupling the auxiliary metric
equation, whose solutions are formally identical to general relativistic ones.
This further exhibits explicitly a degeneracy between modification of gravity
and modification of equations of state. We discuss observational consequences
of this degeneracy and argue that such a completion of General Relativity is
viable from both an experimental and theoretical point of view (in the sense
that it does not contain more instabilities than General Relativity). Finally
we reveal the mechanism of singularity avoidance in the cosmological context
and argue that similar regularization should occur for black hole formation. An
analogous treatment of sources other than perfect fluids seems possible.
View original:
http://arxiv.org/abs/1201.4989
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