Triangle Seminars
Monday, 25 Jan 2010
New results on 4D N=2 superconformal sigma-models
Sergei Kuzenko
(University of Western Australia)
Abstract:
Based on the results of 0906.4393 and 0910.5771, this talk will discuss
the formulation of general 4D N=2 superconformal sigma-model in N=2 and N=1 superspace settings.
Based on the results of 0906.4393 and 0910.5771, this talk will discuss
the formulation of general 4D N=2 superconformal sigma-model in N=2 and N=1 superspace settings.
Posted by: IC
Tuesday, 26 Jan 2010
Matrix Product States and Conformal Field Theory
German Sierra Rodero
(Instituto de Fisica Teorica CSIC-UAM, Madrid)
Abstract:
One dimensional spin chains systems represent an ideal place to study a wide range of non perturbative phenomena such as exotic phases, fractional excitations and statistics. A method to study these systems is the so called Matrix Product States, which provides an ansatz for the ground state and excitations. The MPS method exploits the entanglement properties of spin chains but it is limited to describe systems with short range entanglement. For this reason it cannot properly describe critical
systems where the entanglement entropy grows with the size. In this talk we shall present an extension of the MPS which overcomes this difficulty using Conformal Field Theory. The ansatzs so obtained have strong resemblences with the Laughlin wave function of the Fractional Hall effect.
One dimensional spin chains systems represent an ideal place to study a wide range of non perturbative phenomena such as exotic phases, fractional excitations and statistics. A method to study these systems is the so called Matrix Product States, which provides an ansatz for the ground state and excitations. The MPS method exploits the entanglement properties of spin chains but it is limited to describe systems with short range entanglement. For this reason it cannot properly describe critical
systems where the entanglement entropy grows with the size. In this talk we shall present an extension of the MPS which overcomes this difficulty using Conformal Field Theory. The ansatzs so obtained have strong resemblences with the Laughlin wave function of the Fractional Hall effect.
Posted by: KCL
Y-system for AdS/CFT and quasi-classical strings in AdS5xS5
Nikolay Gromov
(Hamburg)
Abstract:
Recently Kazakov, Vieira and the author conjectured the Y system set
of equations describing the planar spectrum of AdS/CFT. In this paper
we solve the Y system equations in the strong coupling scaling limit.
We show that the quasiclassical spectrum of string moving inside AdS3
x S1 matches precisely with the prediction of the Y system. Thus the
Y system, unlike the asymptotic Bethe ansatz, describes correctly the
spectrum of one-loop string energies including all exponential finite
size corrections. This gives a very non-trivial further support in
favor of the conjecture. We also discuss how the generalization to the
full AdS5 x S5 can be easily constructed using the PSU(2,2 4) symmetry of the problem.
Recently Kazakov, Vieira and the author conjectured the Y system set
of equations describing the planar spectrum of AdS/CFT. In this paper
we solve the Y system equations in the strong coupling scaling limit.
We show that the quasiclassical spectrum of string moving inside AdS3
x S1 matches precisely with the prediction of the Y system. Thus the
Y system, unlike the asymptotic Bethe ansatz, describes correctly the
spectrum of one-loop string energies including all exponential finite
size corrections. This gives a very non-trivial further support in
favor of the conjecture. We also discuss how the generalization to the
full AdS5 x S5 can be easily constructed using the PSU(2,2 4) symmetry of the problem.
Posted by: IC
Wednesday, 27 Jan 2010
Hidden Structures of the S-Matrix
📍 London
Andi Brandhuber
(Queen Mary)
Thursday, 28 Jan 2010
Leading singularities, twistor-strings and grassmannians
Lionel Mason
(Oxford)
Abstract:
Leading singularities are invariants of multi-loop scattering amplitudes (the full amplitude at tree level) obtained by generalized unitarity. In this talk we show how to construct multi-loop leading singularities on twistor space for maximally super-symmetric Yang-Mills (and gravity). Building on the tree-level twistor-string representation of scattering amplitudes, they can be represented as integrals over a moduli space of nodal curves in twistor space. We discuss how this might arise from a conjectural twistor-string path integral representation for the full loop amplitude. We also show how the construction relates to the Grassmannian representation of leading singularities conjectured by Arkani-Hamed et. al.. This shows firstly that all leading singularities can be represented in the Grassmannian, and secondly that the complexity is limited, in particular we conjecture that there are no new leading singularities at beyond 3p loops for NpMHV amplitudes.
Leading singularities are invariants of multi-loop scattering amplitudes (the full amplitude at tree level) obtained by generalized unitarity. In this talk we show how to construct multi-loop leading singularities on twistor space for maximally super-symmetric Yang-Mills (and gravity). Building on the tree-level twistor-string representation of scattering amplitudes, they can be represented as integrals over a moduli space of nodal curves in twistor space. We discuss how this might arise from a conjectural twistor-string path integral representation for the full loop amplitude. We also show how the construction relates to the Grassmannian representation of leading singularities conjectured by Arkani-Hamed et. al.. This shows firstly that all leading singularities can be represented in the Grassmannian, and secondly that the complexity is limited, in particular we conjecture that there are no new leading singularities at beyond 3p loops for NpMHV amplitudes.
Posted by: QMW
Friday, 29 Jan 2010
Two topics in Chern-Simons/M2-brane duality
Nakwoo Kim
(University of Seoul)
Abstract:
We discuss a couple of topics motivated by the Chern-Simons type gauge theory description of M2-branes in nontrivial backgrounds. In the first part we start by briefly reviewing the 3-algebra construction of Bagger, Lambert and Gustavsson. Then we propose an orbifold truncation prescription of 3-algebra, and show how one can 'derive' the ABJM model through matrix regularization. In the second part, we report on some explicit classical solutions of rotating membranes in Sasaki-Einstein 7-manifold M(111). We discuss the dual operators on the CS side, for several different class of spinning membranes.
We discuss a couple of topics motivated by the Chern-Simons type gauge theory description of M2-branes in nontrivial backgrounds. In the first part we start by briefly reviewing the 3-algebra construction of Bagger, Lambert and Gustavsson. Then we propose an orbifold truncation prescription of 3-algebra, and show how one can 'derive' the ABJM model through matrix regularization. In the second part, we report on some explicit classical solutions of rotating membranes in Sasaki-Einstein 7-manifold M(111). We discuss the dual operators on the CS side, for several different class of spinning membranes.
Posted by: IC