Found at least 20 result(s)
Regular Seminar Adel AbulMagd (Sinai University)
at: 11:00 room M128  abstract: In analogy to Beck and Cohen's superstatistics (1), we connect the canonical Gaussian ensembles of the randommatrix theory (RMT) to their superstatistical generalizations through the fluctuation of an intensive parameter, the local density of states (2). On one hand, the superstatistical RMT, seen from the present perspective, may bear interest per se because of the additional nontrivial fluctuations introduced in a simple model. On the other hand, it may constitute a useful statistical paradigm for the analysis of the spectral fluctuations of systems with mixed regularchaotic dynamics. In contrast to other proposals for applying RMT to mixed dynamics, the superstatistical approach yields ensemble of matrices, which are invariant with respect to base transformation. The formalism has been checked by the analysis of experimental resonance spectra of mixed microwave billiards (3). The spectra for each billiard are represented as time series in which the level order plays the role of time. Each series is shown to have two relaxation times as required by superstatistics, which involves the folding of two distribution functions. Analysis of the time series suggests that the superstatistical parameter has an inversechisquare distribution. The experimental distribution nearestneighbor level spacings and strength functions agree with the corresponding predicted distributions. (1) C. Beck and E.G.D. Cohen, Physica A 322, 267 (2003). (2) A.Y. AbulMagd, Phys.Rev. E 71, 066207 (2005). (3) A.Y. AbulMagd, B. Dietz, T. Friedrich, and A. Richter, Phys. R 
Regular Seminar YangHui He (Oxford University)
at: 14:00 room Huxley 503  abstract: We point out a special corner in the space of CalabiYau compactifications where standardlike models tend to emerge. We show how these scenarios are interrelated via a mathematical process of transgression of bundles, a generalisation of the conifold transition. Perhaps our world is special and we live in this oasis within the multitude of vacua. 
Triangular Seminar Jose FigueroaO'Farrill (University of Edinburgh)
at: 16:00 room LG1  abstract: I will discuss several constructions of superalgebras associated to the Killing spinors of a supergravity background, with special emphasis on the ten and elevendimensional supergravities. 
Regular Seminar ChongSun Chu (Durham University)
at: 13:30 room Huxley 503  abstract: The understanding of the nature of spacetime singularity and whether and how it is resolved is one of the most important problem in quantum gravity. Important examples are black hole singularity and cosmological singularity in the big bang. In this talk we will be interested in the later type and an approach to the problem using AdS/CFT correspondence for timedependent background will be discussed. Our gauge theory results suggest that spacetime singularity is indeed resolved and the mechanism will be discussed. 
Regular Seminar Emily HackettJones (Edinburgh)
at: 12:00 room 112  abstract:

Regular Seminar AmirKian KashaniPoor (University of Amsterdam)
at: 13:30 room Huxley 503  abstract: Suppose we could calculate the string partition function to all genera using worldsheet methods. What could we learn from this expression about a potentially underlying (nonperturbative) target space description of the theory? We address this question in the context of the open topological Amodel. 
Regular Seminar HengYu Chen (DAMTP, Cambridge)
at: 13:30 room Huxley 503  abstract: I will begin with basic review on the integrabilities in AdS/CFT correspondence, and move on discussing the role of scattering matrices in gauge and string thoeries. I will then explain the formation of magnon boundststates in gauge theory and their corresponding classical string solution. The scattering of magnon boundstates and their classifications will also be discussed in this seminar. I will also mention some work in progress. 
Regular Seminar Mohab AbouZeid (Vrije U., Brussels and Intl. Solvay Inst., Brussels)
at: 14:00 room 503 Huxley  abstract: I will present a modification of the Berkovits twistor string model which gives Einstein supergravity coupled to YangMills, and has a limit in which the gravity modes can be decoupled to give pure gauge theory amplitudes. I will start by reviewing a number of relevant aspects of twistor theory, including special features associated with different spacetime signatures, supertwistor space, the Penrose transform, the infinity twistor and Penrose's nonlinear graviton construction. I will then review the Witten and Berkovits twistor strings, with emphasis on the latter. The worldsheet formulation of the Berkovits model involves socalled betagamma systems, I will describe the symmetries of such systems and their gauging, and explain how the analysis can be applied to the construction of a family of new gauged Berkovits twistor strings which are free from worldsheet anomalies. I will also describe the corresponding spectra in spacetime, and show that they give Einstein supergravities instead of the higher derivative conformal supergravities arising in the original twistor string models. The new theories include one with the spectrum of N = 8 supergravity, two theories with the spectrum of N = 4 supergravity coupled to N = 4 YangMills, a family of N greater than 0 models with the spectra of selfdual supergravity coupled to selfdual superYangMills, and a nonsupersymmetric string with the spectrum of selfdual gravity coupled to selfdual YangMills and a scalar. Time permitting, I will discuss what is known about the interactions. 
Regular Seminar ChongSun Chu (Durham)
at: 14:00 room 112  abstract:

Regular Seminar YangHui He (Oxford)
at: 13:30 room Ballroom, 58 Princes Gate  abstract: We show the existence of an N=1 supersymmetric vacuum in string theory whose observable sector has exactly the matter content of the MSSM without exotic particles and vectorlike pairs of any type. This is done so by compactifying the E_8 x E_8 heterotic string on a CalabiYau threefold endowed with an SU(4) vector bundle which has been constructed after extensive search. In addition, we discuss the Yukawa couplings and Higgs muterms in this model. 
Regular Seminar Emily HackettJones (Edinburgh)
at: 14:00 room 112  abstract:

Regular Seminar Kurusch EbrahimiFard (IHES)
at: 14:00 room 112  abstract: Kreimer discovered a Hopf algebra structure underlying the combinatorics of renormalization in perturbative quantum field theory. Later, Connes and Kreimer explored the link to noncommutative geometry via a Hopf algebra of rooted trees and described a Hopf algebra of Feynman graphs. After reviewing these developments in some detail we show in this talk how to organize the combinatorics of renormalization in terms of unipotent triangular matrix representations. A simple decomposition of such matrices is used to characterize the process of renormalization. We thereby recover a matrix (anti)representation of the Birkhoff decomposition of Connes and Kreimer. 
Regular Seminar Emil BjerrumBohr (Swansea)
at: 14:00 room 112  abstract:

Triangular Seminar Jose FigueroaO'Farrill (Edinburgh)
at: 15:00 room 410  abstract:

Triangular Seminar Sakura SchaferNameki (Hamburg)
at: 16:30 room 410  abstract:

Regular Seminar JeongHyuck Park (IHESParis)
at: 16:00 room H503  abstract: Four dimensional N=4 super YangMills theory contains a bigger superalgebra than AdS or superconformal algebra, su(2,2/4). It corresponds to a noncentral extension of the latter. The talk is for both physicsts and mathematicans interested in a novel way of obtaining noncentral extensions of Lie algebras. 
Regular Seminar ChongSun Chu (Durham)
at: 14:00 room 112  abstract:

Regular Seminar YangHui He (University of Pennsylvania)
at: 13:15 room 423  abstract:

Triangular Seminar Olalla CastroAlvaredo (Ecole Normale Superieure de Lyon)
at: 15:00 room Geary Room CM524  abstract: In this talk I will present a short review on the algebraic Bethe ansatz technique and on the recently found solution of the socalled inverse problem. I will show how this solution provides a means for the explicit and exact computation of correlation functions in spin chains and summarize some of the many results obtained in this direction by members of the theory group at the ENSLyon in the last years. Finally I will present some work still in progress which intends the generalization of these techniques to the case of spin chains in the presence of impurities. 
Regular Seminar Jose' FigueroaO' Farrill (Edinburgh)
at: 14:00 room 112  abstract:
