Strings: Monday, 09/06/2025, 14:00, Room-226
Debashis Ghoshal (Jawaharlal Nehru University, New Delhi)
Higher Dimensional and other Extensions of the Stuart-Landau Oscillator
The two-dimensional Stuart-Landau system is a paradigmatic model of nonlinear oscillation that exhibits Hopf bifurcation. We use a feature of Clifford algebras to propose a generalisation to arbitrary dimensions, retaining its essential features, including exact solvability and symmetries. We shall discuss the asymptotic behaviour of possible trajectories, limit cycles and basins of attraction. We shall briefly comment on the modulation of its parameters, the dynamics of coupled oscillators and an extension to an ultrametric analogue.
Cosmo: Wednesday, 11/06/2025, 11:30, Lecture Hall
Subodh P. Patil (Instituut-Lorentz for Theoretical Physics)
Black hole echoes and boundary effective field theory
The idea that black holes may not have purely infalling boundary conditions at the horizon has a range of theoretical and phenomenological motivations. The inevitable result is that any post-merger ringdown will exhibit echoes. Given the fact that boundary conditions in any field theory can be implemented via a boundary effective action, we review the reformulation of the problem in terms of a stretched horizon effective field theory. Doing so allows us to specify what is strictly observable, and relate so-called reflection coefficients directly to the scales associated with various boundary operators. This allows us to quantify the deformation of GR required near the horizon to produce such echoes (and whether one finds this plausible). We also find an unavoidable feature: an induced mode dependence for the reflection coefficients that traces to the non-locality of the boundary action generated under RG flow. In order to demystify the physics of non-local boundary effective actions, we show that the same thing happens in electrostatics, which also allows us to distill features specific to horizons. We conclude with a discussion of how our findings can inform future searches, and how a putative no-go theorem for the black hole echoes is evaded.
Strings: Friday, 13/06/2025, 11:00, Room-226
Mritunjay Kumar Verma (Indian Institute of Technology, Indore)
Momentum space CFTs and their applications
Conformal field theories in the momentum space have applications in diverse areas including cosmology, condensed matter physics and holography. In spite of their application, the techniques for analysing CFTs in momentum space have been developed only recently. In this talk, I shall describe these techniques for arbitrary spinning operators. I shall also describe how to connect the momentum space representation of the S matrices in Minkowski space via a suitable limit of the momentum space CFT correlators. I shall also discuss the application of momentum space CFTs to flat holography.
Cosmo: Wednesday, 18/06/2025, 11:30, Lecture Hall
Leila Graef (Niteroi, Fluminense University)
The Back-Reaction Effect of Super-Hubble Cosmological Fluctuations in light of DESI.
Previous studies suggested that the back-reaction of super-Hubble cosmological fluctuations could lead to a dynamical relaxation of the cosmological constant. Moreover, this mechanism appears to be self-regulatory, potentially leading to an oscillatory behavior in the effective dark energy. In this seminar, after reviewing the main advances in the topic, I will present our recent work (arxiv:2502.17395v2) where we perform a preliminary comparison of the background dynamics of this model with the recent radial BAO data from DESI DR2.
Strings: Monday, 23/06/2025, 14:00, Room 226
Mustafa Mullahasanoglu (Bogazici University, Istanbul)
From Dual Gauge Theories to Dual Spin Models
This talk explores the deep interplay between supersymmetric dual gauge theories and integrable lattice spin models via the gauge/YBE correspondence discovered about a decade ago. We examine the equalities of partition functions of dual gauge theories (new hypergeometric integral identities) and interpret them as integrability conditions to construct novel spin models. We discuss decoration transformation to acquire various decorated lattice models from these integrable models. Additionally, we reveal multi-spin interactions through duality transformations. Finally, we highlight how gauge theory dualities inspire and enrich lattice spin models in statistical mechanics.
Cosmo: Wednesday, 25/06/2025, 11:30, Lecture Hall
Mainak Mukhopadhyay (Pennsylvania State University)
Multi-messenger signatures from magnetar remnants of binary neutron star mergers
Binary neutron-star (BNS) mergers can be accompanied by multi-messenger emissions, including gravitational wave (GW), neutrino, and electromagnetic (EM) signals. Some fraction of BNS mergers may result in a rapidly spinning magnetar as a remnant, which can enhance both the EM and neutrino emissions. I will discuss the possible neutrino and EM signatures from such systems. I will also briefly discuss the possibility and prospects of performing GW-triggered stacking searches for high-energy and ultra-high energy neutrinos from BNS mergers in general, at IceCube-Gen2, GRAND, and RNO-G, using the next generation of GW detectors: Einstein Telescope and Cosmic Explorer.
Strings: Monday & Tuesday, 30/06/2025 & 01/07/2025, 14:00, Room 226
Tomoyuki Arakawa (Kyoto University, Kyoto)
An Introduction to W-Algebras and Their Representations
W-algebras were introduced by Zamolodchikov and Fateev–Lukyanov in the 1980s as generalizations of the Virasoro algebra in their study of two-dimensional conformal field theory.Later, Feigin and Frenkel developed a method called quantum Drinfeld–Sokolov reduction, which defines W-algebras and their representations in a functorial way. W-algebras are extremely rich algebraic objects, with deep connections to the geometric Langlands correspondence and to higher-dimensional quantum field theories. In this mini-course, I will discuss the representation theory of W-algebras and its interactions with these broader structures.
Strings: Wednesday, 02/07/2025, 10:00, Solid Seminar Room 1.32
Tomoyuki Arakawa (Kyoto University, Kyoto)
An Introduction to W-Algebras and Their Representations- Part III
W-algebras were introduced by Zamolodchikov and Fateev–Lukyanov in the 1980s as generalizations of the Virasoro algebra in their study of two-dimensional conformal field theory.Later, Feigin and Frenkel developed a method called quantum Drinfeld–Sokolov reduction, which defines W-algebras and their representations in a functorial way. W-algebras are extremely rich algebraic objects, with deep connections to the geometric Langlands correspondence and to higher-dimensional quantum field theories. In this mini-course, I will discuss the representation theory of W-algebras and its interactions with these broader structures.
Cosmo: Wednesday, 09/07/2025, 11:30, Lecture Hall
Benjamin L'Huillier (Sejong University, South Korea)
TBA
Strings: Monday, 14/07/2025, 14:00, Room 226
Thomas Basile (University of Mons, Belgium)
Massless chiral fields in six dimensions
Massless chiral fields of arbitrary spin in 6d, which are higher spin generalisation of self-dual 2-forms, admit a simple formulation in terms of a pair of 0- and 2- forms valued in SL(2,H) symmetric tensors. We will discuss how to construct simple interacting theories using this description, and how to generalise them to arbitrary even dimensions.
Strings: Monday, 18/08/2025, 14:00, Room 226
Jakub Vosmera (IPHT, Paris)
TBA