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S-duality and fivebrane instantons
Auteur(s): Alexandrov S.
Conférence invité: International Symposium Arenshoop (Berlin, DE, 2014-08-25)
Ref HAL: hal-01059619_v1
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Résumé: The low-energy effective action of Type II string theory compactified on a Calabi-Yau threefold is determined by the metric on the vector and hypermultiplet moduli spaces. The latter is known to receive instanton corrections coming from D-branes and NS5-branes wrapping cycles on the Calabi-Yau. I'll show how all of them can be nicely incorporated using twistorial techniques. In particular, fivebrane instantons are derived using S-duality of the type IIB formulation. I'll present also a conjecture for the Witten index of 4d N=2 gauge theories inspired by the twistorial description of the hypermultiplet moduli space.
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Calabi-Yau compactifications: results, relations and problems
Auteur(s): Alexandrov S.
Conférence invité: Strings, Matrices, Integrability (Paris, FR, 2014-08-18)
Ref HAL: hal-01057398_v1
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Résumé: I present an overview of the recent results and open problems in finding the non-perturbative effective action for compactifications of type II string theory on Calabi-Yau manifolds.
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First order gravity on the light front
Auteur(s): Alexandrov S.
Conférence invité: Frontiers of Fundamental Physics 14 (Marseille, FR, 2014-07-15)
Ref HAL: hal-01052742_v1
Exporter : BibTex | endNote
Résumé: After a brief review of unusual features of the light front canonical formulations of field theories, I present the analysis of the canonical structure of the first order formulation of general relativity on a lightlike foliation. It appears to be quite different from the usual spacelike case leading, for instance, to the presence of tertiary constraints. Besides, I discuss the issue of the zero modes and argue that there might be some hidden correspondence with two-dimensional theories.
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N=2 Heterotic-Type II duality and bundle moduli
Auteur(s): Alexandrov S., Louis Jan, Pioline Boris, Valandro Roberto
(Article) Publié:
Journal Of High Energy Physics, vol. p.092 (2014)
Texte intégral en Openaccess :
Ref HAL: hal-01006533_v1
Ref Arxiv: 1405.4792
DOI: 10.1007/JHEP08(2014)092
WoS: 000340505800005
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
6 Citations
Résumé: Heterotic string compactifications on a $K3$ surface $\mathfrak{S}$ depend on a choice of hyperkähler metric, anti-self-dual gauge connection and Kalb-Ramond flux, parametrized by hypermultiplet scalars. The metric on hypermultiplet moduli space is in principle computable within the $(0,2)$ superconformal field theory on the heterotic string worldsheet, although little is known about it in practice. Using duality with type II strings compactified on a Calabi-Yau threefold, we predict the form of the quaternion-Kähler metric on hypermultiplet moduli space when $\mathfrak{S}$ is elliptically fibered, in the limit of a large fiber and even larger base. The result is in general agreement with expectations from Kaluza-Klein reduction, in particular the metric has a two-stage fibration structure, where the $B$-field moduli are fibered over bundle and metric moduli, while bundle moduli are themselves fibered over metric moduli. A more precise match must await a detailed analysis of $R^2$-corrected ten-dimensional supergravity.
Commentaires: 20 pages
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Dualities and fivebrane instantons
Auteur(s): Alexandrov S., Banerjee S.
(Article) Publié:
Journal Of High Energy Physics, vol. 2014 p.040 (2014)
Texte intégral en Openaccess :
Ref HAL: hal-00992829_v1
Ref Arxiv: 1405.0291
DOI: 10.1007/jhep11(2014)040
WoS: 000344749600003
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
7 Citations
Résumé: We derive the fivebrane instanton corrections to the hypermultiplet moduli space $M_H$ of Calabi-Yau string vacua using S-duality symmetry of the type IIB formulation. The result is given in terms of a set of holomorphic functions on the twistor space of $M_H$. It contains not only all orders of the instanton expansion, but also takes into account the presence of D1-D(-1)-brane instantons. Furthermore, we provide a thorough study of the group of discrete isometries of $M_H$ and show that its closure requires a modification of certain symmetry transformations. After this modification, the fivebrane instantons are proven to be consistent with the full duality group.
Commentaires: 40 pages, 3 figures
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Fivebrane instantons in Calabi-Yau compactifications
Auteur(s): Alexandrov S., Banerjee S.
(Article) Publié:
Physical Review D, vol. 90 p.041902(R) (2014)
Texte intégral en Openaccess :
Ref HAL: hal-00958486_v1
Ref Arxiv: 1403.1265
DOI: 10.1103/PhysRevD.90.041902
WoS: 000341287800002
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
11 Citations
Résumé: We provide the last missing piece of the complete non-perturbative description of the low energy effective action emerging from Calabi-Yau compactifications of type II string theory --- NS5-brane instanton corrections to the hypermultiplet moduli space $M_H$. We find them using S-duality symmetry of the type IIB formulation. The result is encoded in a set of holomorphic functions on the twistor space of $M_H$ and includes all orders of the instanton expansion.
Commentaires: 5 pages
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Canonical structure of tetrad bigravity
Auteur(s): Alexandrov S.
(Séminaires)
School of Mathematical Sciences (Nottingham, GB), 2013-11-28
Résumé: 'll discuss a recently proposed tetrad formulation of bimetric
gravity. Like generic massive gravity theories, bigravity models
suffer from the presence of a certain ghost scalar field.
Recently, it was argued however that there are 3 potentials which
are free from this pathology. Although the original formulation of
these potentials is quite nasty, they take a beautiful form in
terms of the tetrads. I'll present the canonical analysis of this
tetrad reformulation and confirm that it is ghost-free describing
the seven degrees of freedom of a massless and a massive
gravitons.
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