Forthcoming events in this series
12:00
From the holomorphic Wilson Loop, to dlog forms for Amplitudes and their integration
12:00
Symmetry operators and conserved quantities for fields on Kerr
12:00
12:00
12:00
Hidden algebras in scattering amplitudes
Abstract
We will discuss the origin of the conjectured colour-kinematics
duality in perturbative gauge theory, according to which there is a
symmetry between the colour dependence and the kinematic dependence of the
S-matrix. Based on this duality, there is a prescription to obtain gravity
amplitudes as the "double copy" of gauge theory amplitudes. We will first
consider tree-level amplitudes, where a diffeomorphism algebra underlies
the structure of MHV amplitudes, mirroring the colour algebra. We will
then draw on the progress at tree-level to consider one-loop amplitudes.
14:30
12:00
15:00
One-Loop Renormalization and the S-matrix
Abstract
Abstract: In this talk, I will discuss the proportionality between tree amplitudes and the ultraviolet divergences in their one-loop corrections in Yang-Mills and (N < 4) Super Yang-Mills theories in four-dimensions. From the point of view of local perturbative quantum field theory, i.e. Feynman diagrams, this proportionality is straightforward: ultraviolet divergences at loop-level are absorbed into coefficients of local operators/interaction vertices in the original tree-amplitude. Ultraviolet divergences in loop amplitudes are also calculable through on-shell methods. These methods ensure manifest gauge-invariance, even at loop-level (no ghosts), at the expense of manifest locality. From an on-shell perspective, the proportionality between the ultraviolet divergences the tree amplitudes is thus not guaranteed. I describe systematic structures which ensure proportionality, and their possible connections to other recent developments in the field.
12:00
Solitons from geometry.
Abstract
Solitons are localised non-singular lumps of energy which describe particles non perturbatively. Finding the solitons usually involves solving nonlinear differential equations, but I shall show that in some cases the solitons emerge directly from the underlying space-time geometry: certain abelian vortices arise from surfaces of constant mean curvature in Minkowski space, and skyrmions can be constructed from the holonomy of gravitational instantons.
14:30
12:00
12:00
12:00
Peeling of the Weyl tensor and gravitational radiation in higher dimensions.
Abstract
Abstract: In this talk, I will discuss the peeling behaviour of the Weyl tensor near null infinity for asymptotically flat higher dimensional spacetimes. The result is qualitatively different from the peeling property in 4d. Also, I will discuss the rewriting of the Bondi energy flux in terms of "Newman-Penrose" Weyl components.
12:00
Correlation functions, Wilson loops, and local operators in twistor space
Abstract
Abstract:
Motivated by the correlation functions-Wilson loop correspondence in
maximally supersymmetric Yang-Mills theory, we will investigate a
conjecture of Alday, Buchbinder, and Tseytlin regarding correlators of
null polygonal Wilson loops with local operators in general position.
By translating the problem to twistor space, we can show that such
correlators arise by taking null limits of correlation functions in the
gauge theory, thereby providing a proof for the conjecture.
Additionally, twistor methods allow us to derive a recursive formula for
computing these correlators, akin to the BCFW recursion for scattering
amplitudes.
12:00
The Wess-Zumino-Witten model
Abstract
The WZW functional for a map from a surface to a Lie group has a role in the theory of harmonic maps, and it also arises as the determinant of a d-bar operator on the surface, as the action functional for a 2-dimensional quantum field theory, as the partition function of 3-dimensional Chern-Simons theory on a manifold with boundary, and as the norm-squared of a state-vector. It is intimately related to the quantization of the symplectic manifold of flat bundles on the surface, a fascinating test-case for different approaches to geometric quantization. It is also interesting as an example of interpolation between commutative and noncommutative geometry. I shall try to give an overview of the area, focussing on the aspects which are still not well understood.
12:00
Thermal Stability of Quantum Black Holes
Abstract
I shall start with an idea (somewhat heuristic) that I call `Thermal Holography' and use that to probe the thermal behaviour of quantum horizons, i.e., without using any classical geometry, but using ordinary statistical mechanics with Gaussian fluctuations. This approach leads to a criterion for thermal stability for thermally active horizons with an Isolated horizon as an equilibrium configuration, whose (microcanonical) entropy has been computed using Loop Quantum Gravity (I shall outline this computation). As fiducial checks, we briefly look at some very well-known classical black hole metrics for their thermal stability and recover known results. Finally, I shall speculate about a possible link between our stability criterion and the Chandrasekhar upper bound for the mass of stable neutron stars.
12:00