We present a new family of exact four-dimensional Taub-NUT spacetimes in Einstein-Λ theory supplemented with a conformally coupled scalar field exhibiting a power-counting super-renormalizable potential. Our configurations are constructed in the following manner: A solution of a conformally coupled theory with a conformal potential, henceforth the seed (gμν,φ), is transformed by the action of a specific change of frame in addition with a simultaneous shift of the seed scalar field. The conformal factor of the transformation and the shift are both affine functions of the original scalar φ. The new configuration, (ḡμν , φ̄), solves the field equations of a conformally coupled theory with the extended aforementioned super-renormalizable potential, this under the presence of an effective cosmological constant. The new spectrum of solutions is notoriously enhanced with respect to the original seed containing regular black holes, wormholes, and bouncing cosmologies. We highlight the existence of two types of exact black bounces given by de Sitter and anti-de Sitter geometries that transit across three different configurations each. The de Sitter geometries transit from a regular black hole with event and cosmological horizons to a bouncing cosmology that connects two de Sitter Universes with different values of the asymptotic cosmological constant. An intermediate phase, which might be represented by two different configurations, takes place. These configurations are given by a de Sitter wormhole or by a bouncing cosmology that connects two de Sitter Universes, both under the presence of a cosmological horizon. On the other hand, the anti-de Sitter geometries transit from a regular black hole with inner and event horizons to a wormhole that connects two asymptotic boundaries with different constant curvatures. The intermediate phase is given in this case by an anti-de Sitter regular black hole with a single event horizon. This regular black hole might appear in two different configurations. As a regular anti-de Sitter black hole inside of an anti-de Sitter wormhole or as an anti-de Sitter regular black hole with a cosmological bounce in its interior. All these geometries are shown to be smoothly connected by the mass parameter only. Other standard stationary black holes, bouncing cosmologies and wormholes are also identified.

tba [please email a.held@imperial.ac.uk for zoom link or password]

We consider the four-point correlator of the stress tensor multiplet in N = 4 SYM in the limit of large c=N^2, but finite \lambda=g^2 N. For finite values of \lambda single-trace intermediate operators arise at order 1/c and this leads to specific poles in the Mellin representation of the correlator. The sign of the residue at these poles is fixed by unitarity. We consider solutions consistent with crossing symmetry and this pole structure. We show that in a certain regime all solutions result in a negative contribution to the anomalous dimension of twist four operators. This positivity condition can also be proven by assuming the correct Regge behaviour for the Mellin amplitude. The positivity constraints arising from CFT for the Mellin amplitude take a very similar form to the causality constraint for the forward limit of the S-matrix.

This talk will review perturbative and non-perturbative properties of string theory scattering amplitudes with particular emphasis on the constraints imposed by duality with M-theory on their low energy action.

http://personal.maths.surrey.ac.uk/st/M.Wolf/conferences/smuk2013/index.html

http://personal.maths.surrey.ac.uk/st/M.Wolf/conferences/smuk2013/index.html

We generalize Regge theory to correlation functions in conformal field theories. This is done by exploring the analogy between Mellin amplitudes in AdS/CFT and S-matrix elements. In the process, we develop the conformal partial wave expansion in Mellin space, elucidating the analytic structure of the partial amplitudes. We apply the new formalism to the case of four point correlation functions between protected scalar operators in N=4 Super Yang Mills, in cases where the Regge limit is controlled by the leading twist operators associated to the pomeron-graviton Regge trajectory. At weak coupling, we are able to predict to arbitrary high order in the 't Hooft coupling the behaviour near J=1 of the OPE coefficients C_{OOJ} between the external scalars and the spin J leading twist operators. At strong coupling, we use recent results for the anomalous dimension of the leading twist operators to improve current knowledge of the AdS graviton Regge trajectory - in particular, determining the next and next to next leading order corrections to the intercept. Finally, by taking the flat space limit and considering the Virasoro-Shapiro S-matrix element, we compute the strong coupling limit of the OPE coefficient C_{LLJ} between two Lagrangians and the leading twist operators of spin J.

The task of classifying logarithmic conformal field theories, traditionally considered beyond reach, has become feasible by identifying an algebraic object that largely captures this classification. In some sense, the relevant algebraic tool is a braided analogue of the Howe/Schur--Weyl duality.

Graeme Segal FRS (Oxford) 'Noncommutative geometry and quantum field theory' and Michael Green FRS (Cambridge) '2007 Naylor Lecture: Some dualities of string theory and quantum gravity'. Ends at 18:00. See www.mth.kcl.ac.uk/'tilde'anderl/LMSpremeeting/

Neil Lambert (KCL) 'From D-branes to M-branes', David Tong (DAMTP) 'Quantum vortex strings' plus several presentations by PhD students on their work. Ends at 14:15. See www.mth.kcl.ac.uk/'tilde'anderl/LMSpremeeting/

N=4 SYM is known to have a confinement-deconfinement type phase transition in finite volume as the temperature is raised. This phase transition has been conjectured to smoothly become the Hawking-Page transition between hot AdS space and an AdS black hole as the 't Hooft coupling becomes larger. I show that this phase transition at weak coupling is actually a topology changing transition for the VEVs of the scalar fields and Polyakov loop. This means that the high temperature phase cannot be, as previously thought, the black hole in the dual. I then argue for the existence of a new second order phase transition at a higher temperature to a new phase which has the right symmetries to be identified with the black hole. This is work based on the recent paper hep-th/0703100 with Umut Gursoy, Sean Hartnoll and Prem Kumar.

In this work we define a new limiting procedure that extends the usual thermodynamics treatment of Black Hole physics, to the supersymmetric regime. This procedure is inspired on equivalent statistical mechanics derivations in the dual CFT theory, where the BPS partition function at zero temperature is obtained by a double scaling limit of temperature and the relevant chemical potentials. In supergravity, the resulting partition function depends on emergent generalized chemical potentials conjugated to the different conserved charges of the BPS solitons. With this new approach, studies on stability and phase transitions of supersymmetric solutions are presented. We find stable and unstable regimes with first order phase transitions, as suggested by previous studies on free supersymmetric Yang Mills theory.

(check the triangle webpage under menu 'triangle' for directions to the seminar room)