Born-Infeld Gravity Theories

İbrahim Güllü
Ortadoğu Teknik Üniversitesi

Özet : The BI gravity, in some sense, is the most natural, minimal generalization
of Einstein’s gravity with a better UV behavior, and hence, is a potentially
viable proposal for low energy quantum gravity. We develop techniques of
analyzing the unitarity of general Born-Infeld gravity actions in D-dimensional
spacetimes. The determinantal form of the action allows us to find a compact
expression quadratic in the metric fluctuations around constant curvature
backgrounds. This is highly nontrivial since for the Born-Infeld actions,
in principle, infinitely many terms in the curvature expansion should contribute
to the quadratic action in the metric fluctuations around constant curvature
backgrounds, which would render the unitarity analysis intractable.

By using the developed techniques we construct Born-Infeld (BI) type gravity
theories which describe tree-level unitary (nonghost and nontachyonic)
massless spin-2 modes around their maximally symmetric vacua in four dimensions.
Building unitary BI actions around flat vacuum is straightforward, but this is
a complicated task around (anti)-de Sitter backgrounds. We solve the issue and
give details of constructing perturbatively viable determinantal BI theories.
It is interesting that the Gauss-Bonnet combination, which is a total derivative
in four dimensions, plays an important role in the construction of viable
BI theories.

We also construct an n-dimensional Born-Infeld type gravity theory that has
the same properties as Einstein’s gravity in terms of the vacuum and particle
content: Namely, the theory has a unique viable vacuum (maximally symmetric
solution) and a single massless unitary spin-2 graviton about this vacuum.
The Gauss-Bonnet combination again plays a non-trivial role in the construction
of the theory. As an extreme example, we consider the infinite dimensional
limit where an interesting exponential gravity arises.

Tarih : 29 Eylül 2016 Perşembe, Saat: 15:00
Yer : MSGSÜ Bomonti Yerleşkesi, Fizik Bölümü

Ayrıntılı bilgi : Cemsinan Deliduman (cemsinan@msgsu.edu.tr)