Résumé:

I'll review the progress achieved in constructing the non-perturbative hypermultiplet moduli space using twistorial methods. The metric on this space determines the low-energy effective action of Type II string theory compactified on a Calabi-Yau threefold. It receives instanton corrections due to D-branes and NS5-branes and I'll show how all of them can be nicely incorporated at the level of the twistor space. I'll argue that the inclusion of NS5-brane instantons might be closely related to quantization of a certain integrable structure. If the time permits, I'll present also a conjecture for the Witten index of 4d N=2 gauge theories inspired by the twistorial description of the hypermultiplet moduli space.

Résumé:

I'll review the progress achieved in constructing the non-perturbative hypermultiplet moduli space using twistorial methods. The metric on this space determines the low-energy effective action of Type II string theory compactified on a Calabi-Yau threefold. It receives instanton corrections due to D-branes and NS5-branes and I'll show how all of them can be nicely incorporated at the level of the twistor space. I'll argue that the inclusion of NS5-brane instantons might be closely related to quantization of a certain integrable structure. If the time permits, I'll present also a conjecture for the Witten index of 4d N=2 gauge theories inspired by the twistorial description of the hypermultiplet moduli space.

Résumé:

After a brief review of unusual features of the light front canonical formulations of field theories, I'll present the analysis of the canonical structure of the first order formulation of general relativity on a lightlike foliation. It appears to be quite different from the usual spacelike case leading, for instance, to the presence of tertiary constraints. Besides, I'll discuss the issue of the zero modes and argue that there might be some hidden correspondence with two-dimensional theories.

Ref HAL: hal-01101042_v1
Exporter : BibTex | endNote
Résumé:

I'll review the current understanding of the low energy effective theory resulting from compactifications of Type II superstrings on Calabi-Yau manifolds. The effective action can be encoded into the metric on a moduli space which is known to receive quantum stringy corrections, both perturbative and non-perturbative. The description of instanton effects crucially relies on twistorial methods and points toward a deep relation to integrable structures.

Ref HAL: hal-01160240_v1
Ref Arxiv: 1410.2897
DOI: 10.1088/1475-7516/2015/03/043
WoS: 000355633800043
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
17 Citations
Résumé:

We analyze the first-order formulation of the ghost-free bigravity model in three-dimensions known as zwei-dreibein gravity. For a special choice of parameters, it was argued to have an additional gauge symmetry and give rise to a partially massless theory. We provide a thorough canonical analysis and identify that whether the theory becomes partially massless depends on the form of the stability condition of the secondary constraint responsible for the absence of the ghost. Generically, it is found to be an equation for a Lagrange multiplier implying that partially massless zwei-dreibein gravity does not exist. However, for special backgrounds this condition is identically satisfied leading to the presence of additional symmetries, which however disappear at quadratic order in perturbations.

Commentaires: 21 pages

Ref HAL: hal-01071271_v1
Exporter : BibTex | endNote
Résumé:

I propose to consider a new function on the moduli space of N=2 supersymmetruic gauge theories in 4 dimensions. It encodes the BPS spectrum of the theory and possesses many intersting properties which make it unique and one of the most natural objects to be studied.

Ref HAL: hal-01099930_v1
Ref Arxiv: 1412.8182
DOI: 10.1007/JHEP02(2015)176
WoS: 000350695900001
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
13 Citations
Résumé:

We use the twistorial construction of D-instantons in Calabi-Yau compactifications of type II string theory to compute an explicit expression for the metric on the hypermultiplet moduli space affected by these non-perturbative corrections. In this way we obtain an exact quaternion-Kahler metric which is a non-trivial deformation of the local c-map. In the four-dimensional case corresponding to the universal hypermultiplet, our metric fits the Tod ansatz and provides an exact solution of the continuous Toda equation. We also analyze the fate of the curvature singularity of the perturbative metric by deriving an S-duality invariant equation which determines the singularity hypersurface after inclusion of the D(-1)-instanton effects.

Commentaires: 20+12+4 pages