Topological representation of cloth state for robot manipulation
Abstract
Research on robot manipulation has focused, in recent years, on grasping everyday objects, with target objects almost exclusively rigid items. Non–rigid objects, as textile ones, pose many additional challenges with respect to rigid object manipulation. In this seminar we will present how we can employ topology to study the ``state'' of a rectangular textile using the configuration space of $n$ points on the plane. Using a CW-decomposition of such space, we can define for any mesh associated with a rectangular textile a vector in an euclidean space with as many dimensions as the number of regions we have defined. This allows us to study the distribution of such points on the cloth and define meaningful states for detection and manipulation planning of textiles. We will explain how such regions can be defined and computationally how we can assign to any mesh the corresponding region. If time permits, we will also explain how the CW-structure allows us to define more than just euclidean distance between such mesh-distributions.
12:45
Twisted QFT and Operator Algebra
Abstract
I will discuss various operator algebras in supersymmetric quantum field theories in various dimensions. The operator algebras are induced and classified by generalised topological twists. Omega deformation plays an important role in connecting different sectors. This talk is based on previous works and a work in progress with Junya Yagi.
12:45
An optical theorem for CFT and high-energy string scattering in AdS at one loop
Abstract
In this talk I will present an optical theorem for perturbative CFTs, which directly computes the double discontinuity of CFT correlators in terms of the discontinuities of correlators at lower loops or lower points, in analogy to the optical theoreom for scattering amplitudes. I will then discuss the application of this theorem to high-energy scattering of type IIb strings in AdS at one loop and finite 't Hooft coupling. Tidal excitations are taken into account and shown to be efficiently described by an AdS vertex function. The result is related to the 1987 flat space result of Amati, Ciafaloni and Veneziano via the flat space limit in impact parameter space.
12:45
Geometry, Strings and QFTs in d > 4
Abstract
We will discuss recent progress in understanding (ordinary and generalized) symmetries, dualities and classification of superconformal field theories in 5d and 6d, which involves the study of M-theory and F-theory compactified on Calabi-Yau threefolds.
12:45
Classical scattering of spinning black holes from quantum amplitudes
Abstract
In view of the recent observations of gravitational-wave signals from black-hole mergers, classical black-hole scattering has received considerable interest due to its relation to the classical bound-state problem of two black holes inspiraling onto each other. In this talk I will discuss the link between classical scattering of spinning black holes and quantum scattering amplitudes for massive spin-s particles. Considering the first post-Minkowskian (PM) order, I will explain how the spin-exponentiated structure of the relevant tree-level amplitude follows from minimal coupling to Einstein's gravity and in the s → ∞ limit generates the black holes' complete series of spin-induced multipoles. The resulting scattering function will be shown to encode in a simple way the classical net changes in the black-hole momenta and spins at 1PM order and to all orders in spins. I will then comment on the results and challenges at 2PM order and beyond.
12:45
Discrete and higher-form symmetries from wrapped M5-branes
Abstract
A vast class of 4d SCFTs can be engineered by wrapping a stack of M5-branes on a Riemann surface. These SCFTs can exhibit a variety of global symmetries, continuous or discrete, including both ordinary (0-form) symmetries, as well as generalized (higher-form) symmetries. In this talk, I will focus on discrete and higher-form symmetries in setups with M5-branes on a smooth Riemann surface. Adopting a holographic point of view, a crucial role is played by topological mass terms in 5d supergravity (similar to BF terms in four dimensions). I will discuss how the global symmetries of the boundary 4d theory are inferred from the 5d topological terms, and how one can compute 4d ‘t Hooft anomalies involving discrete and/or higher-form symmetries.
12:45
Instantons, symmetries and anomalies in five dimensions
Abstract
All five-dimensional non-abelian gauge theories have a U(1)U(1)IU(1) global symmetry associated with instantonic particles. I will describe a mixed ’t Hooft anomaly between this and other global symmetries of the theory, namely the one-form center symmetry or ordinary flavor symmetry for theories with fundamental matter. I will explore some general dynamical properties of the candidate phases implied by the anomaly, and apply our results to supersymmetric gauge theories in five dimensions, analysing the symmetry enhancement patterns occurring at their conjectured RG fixed points.
Maxima of a random model of the Riemann zeta function on longer intervals (and branching random walks)
Abstract
We study the maximum of a random model for the Riemann zeta function (on the critical line at height T) on the interval $[-(\log T)^\theta,(\log T)^\theta)$, where $ \theta = (\log \log T)^{-a}$, with $0<a<1$. We obtain the leading order as well as the logarithmic correction of the maximum.
As it turns out a good toy model is a collection of independent BRW’s, where the number of independent copies depends on $\theta$. In this talk I will try to motivate our results by mainly focusing on this toy model. The talk is based on joint work in progress with L.-P. Arguin and G. Dubach.
Zeros, moments and derivatives
This seminar will be held via zoom. Meeting link will be sent to members of our mailing list (https://lists.maths.ox.ac.uk/mailman/listinfo/random-matrix-theory-anno…) in our weekly announcement on Monday.
Abstract
For 20 years we have known that average values of characteristic polynomials of random unitary matrices provide a good model for moments of the Riemann zeta function. Now we consider moments of the logarithmic derivative of characteristic polynomials, calculations which are motivated by questions on the distribution of zeros of the derivative of the Riemann zeta function. Joint work with Emilia Alvarez.