Triangle Seminars
Tuesday, 19 May 2026
On the Cosmological Constant and Dark Energy in String Theory
📍 London
Susha Parameswaran
(University of Liverpool)
Abstract:
Why doesn’t the vacuum energy, implied by QFT and the Standard Model of Particle Physics, curve spacetime catastrophically towards an exponentially rapid expansion or collapse? Supersymmetry is known to ameliorate this long-standing Cosmological Constant Problem, but only down to the scale set by the susy-breaking mass splittings; at least ~TeV for the visible sector. String theory offers new possibilities. I will describe how the symmetries and dynamics of string theory can lead to a suppression of the one-loop vacuum energy down to the observed scale of Dark Energy. I will illustrate these ideas with an explicit string construction, based on non-supersymmetric string theory, and discuss the remaining opportunities and challenges for theory and observation.
Why doesn’t the vacuum energy, implied by QFT and the Standard Model of Particle Physics, curve spacetime catastrophically towards an exponentially rapid expansion or collapse? Supersymmetry is known to ameliorate this long-standing Cosmological Constant Problem, but only down to the scale set by the susy-breaking mass splittings; at least ~TeV for the visible sector. String theory offers new possibilities. I will describe how the symmetries and dynamics of string theory can lead to a suppression of the one-loop vacuum energy down to the observed scale of Dark Energy. I will illustrate these ideas with an explicit string construction, based on non-supersymmetric string theory, and discuss the remaining opportunities and challenges for theory and observation.
Posted by: Sebastian Cespedes
Wednesday, 20 May 2026
TBA
📍 London
Gabi Zafrir
(University of Haifa)
Abstract:
TBA
TBA
Posted by: Kiarash Naderi
Holograms in the Sky from Euclidean AdS
📍 London
Charlotte Sleight
(Durham)
Abstract:
The AdS/CFT correspondence is our most successful working example of the holographic principle, identifying quantum gravity in anti-de Sitter space with a non-gravitational conformal field theory in one dimension lower. In this talk I will discuss how far lessons from AdS/CFT can be pushed towards settings closer to our universe, taking anti-de Sitter’s maximally symmetric cousins, de Sitter and Minkowski space, as a starting point. A key hurdle for holography in these settings is that the physics involves outgoing radiation. I will review results showing that perturbative correlation functions at de Sitter future infinity, and on the celestial sphere of Minkowskispace, can nevertheless be expressed as boundary correlators in Euclidean AdS. This Euclidean perspective provides a concrete bridge between radiative observables and familiar AdS technology, and it helps clarify which structural features of AdS/CFT persist, and which require modification, when one moves beyond the AdS setting.
The AdS/CFT correspondence is our most successful working example of the holographic principle, identifying quantum gravity in anti-de Sitter space with a non-gravitational conformal field theory in one dimension lower. In this talk I will discuss how far lessons from AdS/CFT can be pushed towards settings closer to our universe, taking anti-de Sitter’s maximally symmetric cousins, de Sitter and Minkowski space, as a starting point. A key hurdle for holography in these settings is that the physics involves outgoing radiation. I will review results showing that perturbative correlation functions at de Sitter future infinity, and on the celestial sphere of Minkowskispace, can nevertheless be expressed as boundary correlators in Euclidean AdS. This Euclidean perspective provides a concrete bridge between radiative observables and familiar AdS technology, and it helps clarify which structural features of AdS/CFT persist, and which require modification, when one moves beyond the AdS setting.
Posted by: Andrew Svesko
Thursday, 21 May 2026
Unexpected Symmetries of Kerr Black Hole Scattering
📍 London
Graham Brown
(Edinburgh)
Abstract:
Recent years have seen considerable progress in computing scattering observables for spinning black holes at high PM orders, using both amplitude based and worldline methods. In this talk we will use these results to investigate the integrability properties of scattering Kerr black holes, both in the probe limit and beyond. We will begin by reviewing the radial action and the recently introduced Dirac bracket formalism, before applying them to define a notion of asymptotic integrability. Using these tools, we will show that this integrability holds to higher orders in spin than previously known. Finally, we will give a new perspective on spin shift symmetry and show how this can be combined with integrability constraints to help bootstrap the radial action.
This talk is based on 2508.10761.
Recent years have seen considerable progress in computing scattering observables for spinning black holes at high PM orders, using both amplitude based and worldline methods. In this talk we will use these results to investigate the integrability properties of scattering Kerr black holes, both in the probe limit and beyond. We will begin by reviewing the radial action and the recently introduced Dirac bracket formalism, before applying them to define a notion of asymptotic integrability. Using these tools, we will show that this integrability holds to higher orders in spin than previously known. Finally, we will give a new perspective on spin shift symmetry and show how this can be combined with integrability constraints to help bootstrap the radial action.
This talk is based on 2508.10761.
Posted by: Kymani Armstrong-Williams