S. L. Cacciatori

Hawking radiation from ultrashort laser pulse filaments

Event horizons of astrophysical black holes and gravitational analogues have been predicted to excite the quantum vacuum and give rise to the emission of quanta, known as Hawking radiation. We experimentally create such a gravitational analogue using ultrashort laser pulse filaments and our measurements demonstrate a spontaneous emission of photons that confirms theoretical predictions.

The asymptotic dynamics of de Sitter gravity in three dimensions

We show that the asymptotic dynamics of three-dimensional gravity with a positive cosmological constant is described by Euclidean Liouville theory. This provides an explicit example of a correspondence between de Sitter (dS) gravity and conformal field theories. In the case at hand, this correspondence is established by formulating Einstein gravity with positive cosmological constant in three dimensions as an SL(2, ) Chern–Simons (CS) theory. The de Sitter boundary conditions on the connection are divided into two parts. The first part reduces the CS action to a nonchiral SL(2, ) WZNW model, whereas the second provides the constraints for a further reduction to Liouville theory, which resides on the past boundary of dS3.

Noncommutative gravity in two dimensions

We deform a two-dimensional topological gravity making use of its gauge theory formulation. The obtained noncommutative gravity model is shown to be invariant under a class of transformations that reduce to standard diffeomorphisms once the noncommutativity parameter is set to zero. Some solutions of the deformed model, such as fuzzy AdS2, are obtained. Furthermore, the transformation properties of the model under the Seiberg–Witten map are studied.

W(infinity) algebras, conformal mechanics, and black holes

We discuss BPS solitons in gauged = 2, D = 4 supergravity. The solitons represent extremal black holes interpolating between different vacua of anti-de Sitter spaces. The isometry superalgebras are determined and the motion of a superparticle in the extremal black hole background is studied and confronted with superconformal mechanics. We show that the Virasoro symmetry of conformal mechanics, which describes the dynamics of the superparticle near the horizon of the extremal black hole under consideration, extends to a symmetry under the w algebra of area-preserving diffeomorphisms. We find that a Virasoro subalgebra of w can be associated with the Virasoro algebra of the asymptotic symmetries of AdS 2 . In this way spacetime diffeomorphisms of AdS 2 translate into diffeomorphisms in phase space: our system offers an explicit realization of the AdS 2 /CFT 1 correspondence. Using the dimensionally reduced action, the central charge is computed. Finally, we also present generalizations of superconformal mechanics which are invariant under = 1 and = 2 superextensions of w .

The 0-brane Action in a General D = 4 Supergravity Background

We begin by presenting the superparticle action in the background of = 2, D = 4 supergravity coupled to n vector multiplets interacting via an arbitrary special Kahler geometry. Our construction is based on implementing -supersymmetry. In particular, our result can be interpreted as the source term for = 2 BPS black holes with a finite horizon area. When the vector multiplets can be associated with the complex structure moduli of a Calabi-Yau manifold, our 0-brane action can then be derived by wrapping 3-branes around 3-cycles of the 3-fold. Our result can be extended to the case of higher supersymmetry; we explicitly construct the supersymmetric action for a superparticle moving in an arbitrary = 8 supergravity background with ½, (1/4) or (1/8) residual supersymmetry

Euler angles for G2

We provide a simple parameterization for the group G2, which is analogous to the Euler parameterization for SU(2). We show how to obtain the general element of the group in a form emphasizing the structure of the fibration of G2 with fiber SO(4) and base H, the variety of quaternionic subalgebras of octonions. In particular this allows us to obtain a simple expression for the Haar measure on G2. Moreover, as a by-product it yields a concrete realization and an Einstein metric for H.

Dielectric black holes induced by a refractive index perturbation and the Hawking effect

We consider a 4D model for photon production induced by a refractive index perturbation in a dielectric medium. We show that, in this model, we can infer the presence of a Hawking type effect. This prediction shows up both in the analogue Hawking framework, which is implemented in the pulse frame and relies on the peculiar properties of the effective geometry in which quantum fields propagate, as well as in the laboratory frame, through standard quantum field theory calculations. Effects of optical dispersion are also taken into account, and are shown to provide a limited energy bandwidth for the emission of Hawking radiation.

Noncommutative Einstein-AdS gravity in three dimensions

Abstract We present a Lorentzian version of three-dimensional noncommutative Einstein-AdS gravity by making use of the Chern–Simons formulation of pure gravity in 2+1 dimensions. The deformed action contains a real, symmetric metric and a real, antisymmetric tensor that vanishes in the commutative limit. These fields are coupled to two Abelian gauge fields. We find that this theory of gravity is invariant under a class of transformations that reduce to standard diffeomorphisms once the noncommutativity parameter is set to zero.

Experimental evidence of analogue Hawking radiation from ultrashort laser pulse filaments

Curved space–times and, in particular, event horizons of astrophysical black holes are expected to excite the quantum vacuum and give rise to an emission of quanta known as Hawking radiation. Remarkably, many physical systems may be considered analogous to black holes and as such hold promise for the detection of Hawking radiation. In particular, recent progress in the field of transformation optics, i.e. the description of optical systems in terms of curved space–time geometries, has led to a detailed description of methods for generating, via superluminal dielectrics, a blocking horizon for photons. Our measurements highlight the emission of photons from a moving refractive index perturbation induced by a laser pulse that is in quantitative agreement with the Hawking model. This opens an intriguing and readily accessible observation window into quantum field theory in curved space–time geometries.

Soliton-induced relativistic-scattering and amplification.

Solitons are of fundamental importance in photonics due to applications in optical data transmission and also as a tool for investigating novel phenomena ranging from light generation at new frequencies and wave-trapping to rogue waves. Solitons are also moving scatterers: they generate refractive index perturbations moving at the speed of light. Here we found that such perturbations scatter light in an unusual way: they amplify light by the mixing of positive and negative frequencies, as we describe using a first Born approximation and numerical simulations. The simplest scenario in which these effects may be observed is within the initial stages of optical soliton propagation: a steep shock front develops that may efficiently scatter a second, weaker probe pulse into relatively intense positive and negative frequency modes with amplification at the expense of the soliton. Our results show a novel all-optical amplification scheme that relies on soliton induced scattering.