# Gravity and High Energy Theory

**Gravity is clearly of critical importance to cosmology. It can also be used as a tool for the study of field theories for high energy and condensed matter physics. Furthermore, the puzzles related to its quantum properties have challenged fundamental theory for decades, and continues to stimulate new extensions and generalisations of both gravity and field theory.**

# Fawad Hassan

Fawad Hassan works on extensions of General Relativity as a theory of gravity, in particular on theories with extra spin-2 fields besides the gravitational field. These are usually referred to as massive gravity, bimetric gravity and multimetric gravity. Such theories have novel features that could be relevant for new physics and are strongly constrained by consistency requirements, namely, the absence of ghost instabilities and causality. Unlike theories of spin 0, spin 1/2 and spin 1 fields in terms of which the standard model is formulated, theories with interacting spin 2 fields are less explored and their implications for new physics have not been fully charted out.

# Edvard Mörtsell

Edvard Mörtsell develops phenomenological aspects, and subsequent observational tests, of cosmological theories, specifically phenomena attributed to the gravitational effects of dark matter (additional attractive gravitational forces) and dark energy (a repulsive gravitational force). This work includes cosmological distance probes, gravitational lensing and generalized gravity theories.

# Bo Sundborg

Bo Sundborg aims to understand spacetime and gravity in simple theories without the strong coupling problems typically plaguing gravity. One example is higher spin theory, a simplified relative of string theory. Using the framework of holography, more and more properties similar to ordinary gravity are uncovered. Black holes and cosmology are of particular interest. In simple theories, we can close in on the spacetime inside black hole horizons and the smallness of the cosmological constant.

# Lárus Thorlacius

Guest Professor Lárus Thorlacius works in the area of theoretical high-energy physics, with emphasis on string theory and quantum gravity. He has worked extensively on theoretical problems involving black holes, including the black hole information paradox. His past work also includes boundary conformal field theory, string thermodynamics, non-commutative geometry, and quantum cosmology. In recent years his main focus has been on black hole physics in the context of gauge/gravity duality, or AdS/CFT correspondence, and its application to quantum critical systems in condensed matter physics.

## CoPS division

**Head of division**

Edvard Mörtsell

Room A5:1047

Tel: +46 (0)8 5537 8769

E-mail: edvard@fysik.su.se