11:00 (London time), Thursday, 28 May 2026

Queen Mary University of London

Room MB-503; Mathematics Building

Ludovic Souêtre (Sorbonne University)

The homogeneous Robin boundary conditions for asymptotically Anti-de Sitter spaces

Modelled on Anti-de Sitter, asymptotically Anti-de Sitter spaces can be defined as Lorentzian manifolds that possess a timelike conformal boundary. Due to their lack of global hyperbolicity, finding asymptotically Anti-de Sitter solutions to the Einstein equations (necessarily with a negative cosmological constant) through the Cauchy problem requires tackling the latter as an initial boundary value problem. In this talk, I will present the two known types of geometric boundary conditions leading to the local existence and uniqueness of solutions in dimension \(4\): the Dirichlet boundary conditions, which were introduced by Friedrich in 1995, and the homogeneous Robin boundary conditions, which I introduced in a recent work.

10:00 (London time), Thursday, 04 June 2026

Queen Mary University of London

Room MB-503; Mathematics Building

Nicola De Nitti (Polytechnic University of Bari)

Singular limit for a class of nonlocal conservation laws via compensated compactness

We study a class of nonlocal conservation laws arising in traffic flow, where the flux depends on a spatial convolution with a rescaled kernel. As the kernel concentrates to a Dirac mass, we prove strong \( \mathrm{L}^1_{\mathrm{loc}} \) convergence of the averaged densities to the entropy solution of the corresponding local conservation law. In contrast to previous approaches, we obtain compactness of the averaged family without total variation bounds or Oleĭnik-type estimates. Instead, we derive \( \mathrm{L}^2 \)-type bounds on the entropy production and rely on compensated compactness techniques. We assume only \( \mathrm{L}^1 \cap \mathrm{L}^\infty \) initial data and treat either strictly monotone kernels or a piecewise constant kernel combined with the affine velocity from Greenshields' traffic model. These results address the open problem of nonlocal-to-local convergence in the presence of non-convex kernels. The talk is based on joint work with G. M. Coclite and K. Huang.

11:00 (London time), Thursday, 04 June 2026

Queen Mary University of London

Room MB-503; Mathematics Building

Istvan Kadar (ETH)

Smooth singularity formation for the energy critical wave equation without quantization

The energy-critical nonlinear wave equation (NW) in three dimensions admits a stationary solution. In their foundational work, Krieger-Schlag-Tataru constructed (non-smooth) solutions to (NW) that develop singularities with arbitrarily polynomial blow-up rates exceeding the self-similar rate by adiabatically shrinking to a single soliton in spherical symmetry. For comparison, their analogous results for the wave map equation stand in sharp contrast to the quantized blow-up rates for smooth solutions obtained by Raphaël-Rodnianski. In this talk, I discuss a new result establishing the existence of a family of smooth solutions to (NW) that develop singularities at a continuum of polynomial rates, achieved through the collapse of multiple solitons.