arXiv subjects

Dima Fontaine

Publications and source records attributed to Dima Fontaine.

3 recordsLinked to original sources

arXiv2025

Infinite-dimensional symmetries in plane wave spacetimes

We study the asymptotic symmetries of the Nappi-Witten spacetime in four dimensions, a plane wave arising as the Penrose limit of AdS$_2\times S^2$. Imposing suitable boundary conditions at large transverse distance, we uncover a new infinite-dimensional symmetry algebra allowing for non-trivial central extensions. The corresponding phase space encompasses the most general four-dimensional pp-wave metric, including in particular the Penrose limit of Kerr black holes.

hep-th↗

arXiv2025

Anisotropic conformal Carroll field theories and their gravity duals

We investigate anisotropic conformal Carroll field theories and their holographic duals. On the field theory side, we focus on the case with scaling exponent $z=0$ in two and three spacetime dimensions. These theories exhibit infinite-dimensional symmetry algebras, including supertranslations and superrotations, and are closely related to, but distinct from, Warped Conformal Field Theories. We construct the associated Carrollian stress tensor, derive its transformation properties, and analyse the structure of correlation functions under different choices of vacua. On the gravity side, we identify three and four-dimensional plane wave geometries whose isometry algebras realise the two- and three-dimensional Carroll algebra and anisotropic scale transformations. We propose, for each scaling exponent, a phase space of asymptotically-plane wave spacetimes and show that the residual diffeomorphisms reproduce the expected conformal Carroll field theory algebra, establishing a framework for anisotropic Carrollian holography.

hep-th↗

arXiv2025

Electromagnetic multipole expansions and the logarithmic soft photon theorem

We study the general structure of the electromagnetic field in the vicinity of spatial infinity. Starting from the general solution of the sourced Maxwell equations written in terms of multipole moments as obtained by Iyer and Damour, we derive the expansion of the electromagnetic field perturbatively in the electromagnetic coupling. At leading order, where the effect of long-range Coulombic interactions between charged particles is neglected, we discover infinite sets of antipodal matching relations satisfied by the electromagnetic field, which extend and sometimes correct previously known relations. At next-to-leading order, electromagnetic tails resulting from these Coulombic interactions appear, which affect the antipodal matching relations beyond those equivalent to the leading soft photon theorem. Moreover, new antipodal matching relations arise, which we use to re-derive the classical logarithmic soft photon theorem of Sahoo and Sen. Our analysis largely builds upon that of Campiglia and Laddha, although it invalidates the antipodal matching relation which they originally used in their derivation. The antipodal matching relations and the proof of the classical logarithmic soft photon theorem agree with an earlier analysis of Bhatkar, which we generalize using other methods.

hep-th↗