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Interplay between String Theory, Particle Physics and Cosmology
No full textAs part of the event: "The case of the (still) mysterious Universe", presentation of Irene Valenzula and Cumrun Vafa about Interplay between String Theory, Particle Physics and Cosmolog
Geometric Origin of Montonen-Olive Duality
No full textIntroduction The aim of this note is to show how the celebrated Montonen-Olive duality [1] for all N = 4 gauge theories in D = 4 can be derived by geometric engineering in the context of type II strings, where it reduces to T-duality. Even though by now there is a lot of evidence for the Montonen-Olive duality (see e.g. [2]) there is no derivation of this duality. Even with the recent advances in our understanding of dynamics of string theory the derivation of this duality is not yet complete. The aim of this note is to fill this gap. The approach we will follow is in the context of type II compactifications and is quite general and provides a unified approach to all gauge groups. Moreover we gain an understanding of how the field theory duality works by relating it to well understood perturbative symmetries (Tdualities) of strings. 1 2. Montonen-Olive Duality Let us recall what the Montonen-Olive duality is: We consi
Admissible representations and characters of the affine superalgebras osp(l,2) and ŝl(2|l)
Full text linkIn this thesis we compute characters and supercharacters of irreducible admissible representations for the two affine superalgebras osp(l,2;C) and l(2|l;C).The work on osp(l, 2; C) includes a derivation of the embedding diagram. We compute the modular transformations of the Neveu-Schwarz characters of osp(l, 2; C) and show that they transform in a manner consistent with the different possible free fermion spin structures on a torus. In chapter 3 we turn our attention to ŝl(2|l;C). Characters and supercharacters are computed for three classes of admissible representation. We have to derive the embedding diagram for one of these classes. We show that the integrable characters in the classes we study are identical to characters of the N = 4 superconformal algebra and that some of the sl(2|l;C) characters have a pole in a certain limit. The residue at this pole is computed and it is found to be proportional to an N = 2 minimal character. Specialising to fractional levels k of the form k + 1 = l/u,u ϵ N, we consider the SL(2|1)/SL{2) coset theory and make a conjecture that it is a product of a parafermion theory and a rational torus model. The appearance of parafermion characters and rational torus model characters in the branching functions of some examples that we have worked out leads to a conjecture for the general form of the branching functions whenever the level k has the form k + 1 = 1/u.The modular T transformation can be worked out easily for any character or super- character we have computed. We work out the 5 transformation of the Neveu-Schwarz characters in two examples and find that we get a unitary S-matrix in each case. The thesis finishes with some interesting identities between ŝu(2) string functions which are a corollary of the work on branching functions
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