Guillaume Bossard

Universal BPS structure of stationary supergravity solutions

We study asymptotically flat stationary solutions of four-dimensional supergravity theories via the associated G/H ∗ pseudo-Riemannian non-linear sigma models in three spatial dimensions. The Noether charge C associated to G is shown to satisfy a characteristic equation that determines it as a function of the four-dimensional conserved charges. The matrix C is nilpotent for non-rotating extremal solutions. The nilpotency degree of C is directly related to the BPS degree of the corresponding solution when they are BPS. Equivalently, the charges can be described in terms of a Weyl spinor |C i of Spin ∗ (2N), and then the characteristic equation becomes equivalent to a generalisation of the Cartan pure spinor constraint on |C i . The invariance of a given solution with respect to supersymmetry is determined by an algebraic ‘Dirac equation’ on the Weyl spinor |C i . We explicitly solve this equation for all pure supergravity theories and we characterise the stratified structure of the moduli space of asymptotically Taub–NUT black holes with respect to their BPS degree. The analysis is valid for any asymptotically flat stationary solutions for which the singularities are protected by horizons. The H ∗ -orbits of extremal solutions are identified as Lagrangian submanifolds of nilpotent orbits of G, and so the moduli space of extremal spherically symmetric black holes is identified as a Lagrangian subvariety of the variety of nilpotent elements of g. We also generalise the notion of active duality transformations to an ‘almost action’ of the three-dimensional duality group G on asymptotically flat stationary solutions.

Extremal black holes, nilpotent orbits and the true fake superpotential

Dimensional reduction along time offers a powerful way to study stationary solutions of 4D symmetric supergravity models via group-theoretical methods. We apply this approach systematically to extremal, BPS and non-BPS, spherically symmetric black holes, and obtain their “fake superpotential” W. The latter provides first order equations for the radial problem, governs the mass and entropy formula and gives the semi-classical approximation to the radial wave function. To achieve this goal, we note that the Noether charge for the radial evolution must lie in a certain Lagrangian submanifold of a nilpotent orbit of the 3D continuous duality group, and construct a suitable parametrization of this Lagrangian. For general non-BPS extremal black holes in

The ultra-violet question in maximally supersymmetric field theories

\mathcal{N}

On duality symmetries of supergravity invariants

= 8 supergravity, W is obtained by solving a non-standard diagonalization problem, which reduces to a sextic polynomial in W2 whose coefficients are SU(8) invariant functions of the central charges. By consistent truncation we obtain W for other supergravity models with a symmetric moduli space. In particular, for the one-modulus S3 model, W2 is given explicitely as the root of a cubic polynomial. The STU model is investigated in detail and the nilpotency of the Noether charge is checked on explicit solutions.

The vanishing volume of D = 4 superspace

We study the perturbative quantisation of

Counterterms vs. dualities

\mathcal{N} = 8

Octonionic black holes

supergravity in a formulation where its E7(7) symmetry is realised off-shell. Relying on the cancellation of SU(8) current anomalies we show that there are no anomalies for the non-linearly realised E7(7) either; this result extends to all orders in perturbation theory. As a consequence, the

Multi-black holes from nilpotent Lie algebra orbits

{\mathfrak{e}_{7(7)}}