Triangle Seminars

Abstract:
We present a model to study decoherence on non–interacting qubits. Single qubit decoherence (as measured by purity) is obtained in linear response. Two qubit decoherence is solved using the spectator configuration. Entanglement evolution is considered. The n-qubit case is studied using weaker
assumptions. Various results are exemplified using a kicked spin chain as a toy model.

Abstract:
I describe work aimed at combining the advances in moduli stabilisation and supersymmetry breaking with that in building D-brane models with realistic chiral matter spectra. The framework is models of D3/D7 branes at del Pezzo singularities embedded in the LARGE volume scenario of moduli stabilisation. I describe the general phenomenological properties that emerge and discuss the difficulties in computing visible sector soft terms.

Abstract:
We will discuss the missing pieces in the understanding of the
effective field theory description of string creation, the S-dual of the
Hanany-Witten effect, both in the open and closed string picture. We
explain the origin of a crucial bare Chern-Simons term, that used to be
added in by hand for consistency. Finally we summarize the remaining
unsettled issues, concerning the need to modify the DBI action and the
interpretation of the bare term in M-theory.

Abstract:
In this talk I shall discuss special polynomials associated with rational solutions for the Painleve equations.

The Painleve equations (PI-PVI) are six nonlinear ordinary
differential equations that have been the subject of much interest in the past thirty years, which have arisen in a variety of physical applications. Further they may be thought of as nonlinear special functions and arise as symmetry reductions of soliton equations which are solvable by the inverse scattering method, such as the Korteweg-de Vries, Boussinesq and nonlinear Schroedinger equations. Rational solutions of the Painleve equations are expressible in terms of the logarithmic derivative of certain special polynomials. For PII these polynomials are known as the Yablonskii-Vorobev polynomials, first derived in the 1960's by Yablonskii and Vorob'ev. The locations of the roots of these polynomials is shown to have a highly regular triangular structure in the complex plane. The analogous special polynomials associated with rational solutions of PIII, PIV and PV are described and it is shown that their roots also have a highly regular structure.

Abstract:
In this talk I will describe the computation of the four-point function of two weight-2 and two weight-n 1/2-BPS operators at large N and at strong 't Hooft coupling, using the supergravity approximation. I will then discuss the results in the light of the AdS/CFT correspondence.