Alex S. Arvanitakis

Matter coupling in 3D 'minimal massive gravity

The “Minimal Massive Gravity” (MMG) model of massive gravity in three spacetime dimensions (which has the same anti-de Sitter (AdS) bulk properties as “Topologically Massive Gravity” but improved boundary properties) is coupled to matter. Consistency requires a particular matter source tensor, which is quadratic in the stress tensor. The consequences are explored for an ideal fluid in the context of asymptotically de-Sitter (dS) cosmological solutions, which bounce smoothly from contraction to expansion. Various vacuum solutions are also found, including warped (A)dS, and (for special values of parameters) static black holes and an (A)dS2 × S 1 vacuum.

Minimal Massive 3D Gravity Unitarity Redux

A geometrical analysis of the bulk and anti-de Sitter boundary unitarity conditions of 3D ‘minimal massive gravity’ (MMG) (which evades the ‘bulk/boundary clash’ of topologically massive gravity) is used to extend and simplify previous results, showing that unitarity selects, up to equivalence, a connected region in parameter space. We also initiate the study of flat-space holography for MMG. Its relevant flat space limit is a deformation of 3D conformal gravity; the deformation is both nonlinear and non-conformal, implying a linearization instability.

Black hole thermodynamics, stringy dualities and double field theory

We discuss black hole thermodynamics in the manifestly duality invariant formalism of double field theory (DFT). We reformulate and prove the first law of black hole thermodynamics in DFT, using the covariant phase space approach. After splitting the full O(D, D) invariant DFT into a Kaluza-Klein-inspired form where only n coordinates are doubled, our results provide explicit duality invariant mass and entropy formulas. We illustrate how this works by discussing the black fundamental string solution and its T-duals.

Type II strings are Exceptional

We construct the exceptional sigma model: a two-dimensional sigma model coupled to a supergravity background in a manifestly (formally) ED(D)-covariant manner. This formulation of the background is provided by Exceptional Field Theory (EFT), which unites the metric and form fields of supergravity in ED(D) multiplets before compactification. The realisation of the symmetries of EFT on the worldsheet uniquely fixes the Weyl-invariant Lagrangian and allows us to relate our action to the usual type IIA fundamental string action and a form of the type IIB (m,n) action. This uniqueness “predicts” the correct form of the couplings to gauge fields in both Neveu-Schwarz and Ramond sectors, without invoking supersymmetry.

Twistor description of spinning particles in AdS

A bstractThe two-twistor formulation of particle mechanics in D-dimensional anti-de Sitter space for D = 4, 5, 7, which linearises invariance under the AdS isometry group Sp(4; K

Twistor variables for Anti-de Sitter (super)particles

\mathbb{K}

Brane Wess-Zumino terms from AKSZ and exceptional generalised geometry as an

) for K=ℝ,ℂ,ℍ