Fabio Riccioni

IIB supergravity revisited

We show in the SU(1,1)-covariant formulation that IIB supergravity allows the introduction of a doublet and a quadruplet of ten-form potentials. The Ramond-Ramond ten-form potential which is associated with the SO(32) type-I superstring is in the quadruplet. Our results are consistent with a recently proposed E11 symmetry underlying string theory. For the readers convenience we present the full supersymmetry and gauge transformations of all fields both in the manifestly SU(1,1) covariant Einstein frame and in the real U(1) gauge fixed string frame.

Tensor and vector multiplets in six-dimensional supergravity

Abstract We construct the complete coupling of (1,0) supergravity in six dimensions to n tensor multiplets, extending previous results to all orders in the fermi fields. We then add couplings to vector multiplets, as dictated by the generalized Green-Schwarz mechanism. The resulting theory embodies factorized gauge and supersymmetry anomalies, to be disposed of by fermion loops, and is determined by corresponding Wess-Zumino consistency conditions, aside from a quartic coupling for the gauginos. The supersymmetry algebra contains a corresponding extension that plays a crucial role for the consistency of the construction. We leave aside gravitational and mixed anomalies, that would only contribute to higher-derivative couplings.

IIA Ten-forms and the Gauge Algebras of Maximal Supergravity Theories

We show that IIA supergravity can be extended with two independent 10-form potentials. These give rise to a single BPS IIA 9-brane. We investigate the bosonic gauge algebra of both IIA and IIB supergravity in the presence of 10-form potentials and point out an intriguing relation with the symmetry algebra E11, which has been conjectured to be the underlying symmetry of string theory/M-theory.

Geometric couplings and brane supersymmetry breaking

Orientifold vacua allow the simultaneous presence of supersymmetric bulks, with one or more gravitinos, and nonsupersymmetric combinations of BPS branes. This “brane supersymmetry breaking” raises the issue of consistency for the resulting gravitino couplings, and Dudas and Mourad recently provided convincing arguments to this effect for the ten-dimensional USp(32) model. These rely on a nonlinear realization of local supersymmetry a la Volkov–Akulov, although no gravitino mass term is present, and the couplings have a nice geometrical interpretation in terms of “dressed” bulk fields, aside from a Wess–Zumino-like term, resulting from the supersymmetrization of the Chern–Simons couplings. Here we show that all couplings can be given a geometrical interpretation, albeit in the dual 6-form model, whose bulk includes a Wess–Zumino term, so that the nongeometric ones are in fact demanded by the geometrization of their duals. We also determine the low-energy couplings for six-dimensional (1,0) models with brane supersymmetry breaking. Since these include both Chern–Simons and Wess–Zumino terms, only the resulting field equations are geometrical, aside from contributions due to vectors of supersymmetric sectors.

More on ``La Grande Bouffe'': towards higher spin symmetry breaking in AdS

We discuss higher spin gauge symmetry breaking in AdS space from a holographic perspective. Indeed, the AdS/CFT correspondence implies that = 4 SYM theory at vanishing coupling constant is dual to a theory in AdS which exhibits higher spin gauge symmetry enhancement. When the SYM coupling is non-zero, the current conservation condition becomes anomalous, and correspondingly the local higher spin symmetry in the bulk gets spontaneously broken. In agreement with previous results and holographic expectations, we find that the Goldstone mode responsible for the symmetry breaking in AdS has a non-vanishing mass even in the limit in which the gauge symmetry is restored. Moreover, we show that the mass of the Goldstone mode is exactly the one predicted by the correspondence. Finally, we obtain the precise form of the higher spin supercurrents in the SYM side.

IIB nine-branes

We calculate the tensions of all half-supersymmetric nine-branes in IIB string theory. In particular, we point out the existence of a solitonic IIB nine-brane. We find that the D9-brane and its duality transformations parametrize a two-dimensional surface in a four-dimensional space.

Duality symmetries and G+++ theories

We show that the nonlinear realizations of all the very extended algebras G+++, except the B and C series which we do not consider, contain fields corresponding to all possible duality symmetries of the on-shell degrees of freedom of these theories. This result also holds for G+++2 and we argue that the nonlinear realization of this algebra accounts precisely for the form fields present in the corresponding supersymmetric theory. We also find a simple necessary condition for the roots to belong to a G+++ algebra.

On the fermionic Grande Bouffe: more on higher spin symmetry breaking in AdS/CFT

We discuss fermionic higher spin gauge symmetry breaking in AdS space from a holographic perspective. Analogously to the recently discussed bosonic case, the higher spin Goldstino mode responsible for the symmetry breaking has a non-vanishing mass in the limit in which the gauge symmetry is restored. This result is precisely in agreement with the AdS/CFT correspondence, which implies that = 4 SYM at vanishing coupling constant is dual to a theory in AdS which exhibits higher spin gauge symmetry enhancement. When the SYM coupling is non-zero, the current conservation condition becomes anomalous, and correspondingly the local higher spin symmetry in the bulk gets spontaneously broken. We also show that the mass of the Goldstino mode is exactly the one predicted by the correspondence. Finally, we obtain the form of a class of fermionic higher spin currents in the SYM side.

Spacetime-filling branes in ten and nine dimensions

Abstract Type-IIB supergravity in ten dimensions admits two consistent Z 2 truncations. After the insertion of D9-branes, one of them leads to the low-energy action of type-I string theory, and it can be performed in two different ways, in correspondence with the fact that there are two different consistent ten-dimensional type-I string theories, namely, the SO ( 32 ) superstring and the USp ( 32 ) model, in which supersymmetry is broken on the D9-branes. We derive here the same results for type-IIA theory compactified on a circle in the presence of D8-branes. We also analyze the κ -symmetric action for a brane charged with respect to the S-dual of the RR 10-form of type-IIB, and we find that the tension of such an object has to scale like g S −2 in the string frame. We give an argument to explain why this result is in disagreement with the one obtained using Weyl rescaling of the brane action, and we argue that this brane can only be consistently introduced if the other Z 2 truncation of type-IIB is performed. Moreover, we find that one can include a 10-form in type-IIA supersymmetry algebra, and also in this case the corresponding κ -symmetric brane has a tension scaling like g S −2 in the string frame.

Massive higher spins and holography

We review recent progress towards the understanding of higher spin gauge symmetry breaking in AdS space from a holographic vantage point. According to the AdS/CFT correspondence, = 4 SYM theory at vanishing coupling constant should be dual to a theory in AdS which exhibits higher spin gauge symmetry enhancement. When the SYM coupling is non-zero, all but a handful of HS currents are violated by anomalies, and correspondingly local higher spin symmetry in the bulk gets spontaneously broken. In agreement with previous results and holographic expectations, we find that, barring one notable exception (spin 1 eating spin 0), the Goldstone modes responsible for HS symmetry breaking in AdS have non-vanishing mass even in the limit in which the gauge symmetry is restored. We show that spontaneous breaking a la Stuckelberg implies that the mass of the relevant spin s = s − 1 Goldstonefield is exactly the one predicted by the correspondence.