Accueil >
Production scientifique
|
|
D-instantons in Calabi-Yau compactifications
Auteur(s): Alexandrov S.
Conférence invité: String Field Theory 2022 (Prague, CZ, 2023-09-12)
Ref HAL: hal-03811120_v1
Exporter : BibTex | endNote
Résumé: Euclidean D-branes wrapped on non-trivial cycles of a Calabi-Yau threefold are known to affect the metric on the hypermultiplet moduli space determining the effective action of type II strings on such manifolds. After reviewing the existing results on the instanton corrected metric following from a combination of constraints imposed by supersymmetry and dualities, I'll show how the D-instanton effects can be computed by a direct worldsheet approach. This required solving several conceptual and technical problems, which also paved the way for extension of this approach to compactifications with lower supersymmetry. The talk is based on joint work with A. Sen and B. Stefanski.
|
|
|
Joyce structures, twistors and topological strings
Auteur(s): Alexandrov S.
Conférence invité: BPS states, mirror symmetry, and exact WKB II (Sheffield, GB, 2022-09-05)
Ref HAL: hal-03811147_v1
Exporter : BibTex | endNote
Résumé: As shown by T. Bridgeland, a Riemann-Hilbert problem determined by Donaldson-Thomas invariants naturally gives rise to the so-called Joyce structure. It can be characterized by a function known as Plebanski potential, or its close cousin Joyce potential. I'll show that a twistorial solution to the RH problem provides a simple integral expressions for both potentials. Then I'll explain the relation of this solution to the conformal limit of the twistor spacesappearing in gauge and string theories, and physical interpretation acquired bythe two potentials in these setups. For the case of the resolved conifold, I'll present a recipe to make the twistorial solution well-defined despite an infinite BPS spectrum, and trace out the emergence of a tau-function, its relation to topological strings and its behavior under S-duality to the twistorial implementation of instantons in string theory.
|
|
|
D-instantons and superpotential
Auteur(s): Alexandrov S.
Conférence invité: Strings and Geometry 2022 (Utrecht, NL, 2022-05-02)
Ref HAL: hal-03664125_v1
Exporter : BibTex | endNote
Résumé: I'll present the computation of a D-instanton induced superpotential in an orientifold Calabi-Yau compactification of type II string theory using a direct worldsheet approach.
|
|
|
D-instantons in string compactifications
Auteur(s): Alexandrov S.
Conference: Eurostrings 2022 (Lyon, FR, 2022-04-25)
Ref HAL: hal-03664123_v1
Exporter : BibTex | endNote
Résumé: Euclidean D-branes wrapped on non-trivial cycles of a Calabi-Yau threefold are known to affect the metric on the hypermultiplet moduli space determining the effective action of type II strings on such manifolds. After reviewing the existing results on the instanton corrected metric following from a combination of constraints imposed by supersymmetry and dualities, I'll show how the D-instanton effects can be computed by a direct worldsheet approach. It required solving several conceptual and technical problems and has recently been extended to compactifications with lower supersymmetry. The talk is based on joint work with A. Sen and B. Stefanski.
|
|
|
D-instanton Induced Superpotential
Auteur(s): Alexandrov S., Fırat Atakan Hilmi, Kim Manki, Sen Ashoke, Stefański Bogdan
(Article) Publié:
Journal Of High Energy Physics, vol. 2022 p.90 (2022)
Texte intégral en Openaccess :
Ref HAL: hal-03635867_v1
Ref Arxiv: 2204.02981
DOI: 10.1007/JHEP07(2022)090
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: We use string field theory to fix the normalization of the D-instanton corrections to the superpotential involving the moduli fields of type II string theory compactified on an orientifold of a Calabi-Yau threefold in the absence of fluxes. We focus on $O(1)$ instantons whose only zero modes are the four bosonic modes associated with translation of the instanton in non-compact directions and a pair of fermionic zero modes associated with the two supercharges broken by the instanton. We work with a generic superconformal field theory and express our answer in terms of the spectrum of open strings on the instanton. We analyse the contribution of multi-instantons of this kind to the superpotential and argue that it vanishes when background fluxes are absent.
|
|
|
Modular bootstrap for D4-D2-D0 indices on compact Calabi-Yau threefolds
Auteur(s): Alexandrov S., Gaddam Nava, Manschot Jan, Pioline Boris
(Document sans référence bibliographique) 2022-04-05Texte intégral en Openaccess :
Ref HAL: hal-03635855_v1
Ref Arxiv: 2204.02207
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: We investigate the modularity constraints on the generating series $h_r(\tau)$ of BPS indices counting D4-D2-D0 bound states with fixed D4-brane charge $r$ in type IIA string theory compactified on complete Intersection Calabi-Yau threefolds with $b_2 = 1$. For unit D4-brane, $h_1$ transforms as a (vector-valued) modular form under the action of $SL(2,Z)$ and thus is completely determined by its polar terms. We propose an Ansatz for these terms in terms of rank 1 Donaldson-Thomas invariants, which incorporates contributions from a single D6-anti-D6 pair. Using an explicit overcomplete basis of the relevant space of weakly holomorphic modular forms (valid for any $r$), we find that for 10 of the 13 allowed threefolds, the Ansatz leads to a solution for $h_1$ with integer Fourier coefficients, thereby predicting an infinite series of DT invariants.For $r > 1$, $h_r$ is mock modular and determined by its polar part together with its shadow. Restricting to $r = 2$, we use the generating series of Hurwitz class numbers to construct a series $h^{\rm an}_2$ with exactly the same modular anomaly as $h_2$, so that the difference $h_{2}-h^{\rm an}_2$ is an ordinary modular form fixed by its polar terms. For lack of a satisfactory Ansatz, we leave the determination of these polar terms as an open problem.
|
|
|
D-instantons in Type II string theory on Calabi-Yau threefolds
Auteur(s): Alexandrov S.
(Séminaires)
Trinity College (Dublin, IE), 2021-11-17
Résumé: Euclidean D-branes wrapped on non-trivial cycles of a Calabi-Yau threefold are known to affect the metric on the hypermultiplet moduli space determining the effective action of type II strings on such manifolds. After reviewing the existing results on the instanton corrected metric following from a combination of constraints imposed by supersymmetry and dualities, I'll show how the D-instanton effects can be computed by a direct worldsheet approach. It required solving several conceptual and technical problems and can now be extended to compactifications with lower supersymmetry. The talk is based on joint work with A. Sen and B. Stefanski.
|