Searcharxiv⌕ Search

arXiv subjects

Sergei V. Ketov

Publications and source records attributed to Sergei V. Ketov.

At least 109 records · Page 6Linked to original sources
arXiv2003

Nonperturbative low-energy effective action of the universal hypermultiplet

The non-perturbative (D-instanton corrected) low-energy effective action of the universal hypermultiplet in the type-IIA string theory compactified on a Calabi-Yau threefold is calculated in 4d, N=2 supergravity. The action is given by the quaternionic non-linear sigma-model whose metric is governed by the Eisenstein series E_{3/2}. The U(1)xU(1) isometry and SL(2,Z) modular invariance play the key role in our construction.

hep-th↗
arXiv2002

Summing up D-instantons in N=2 supergravity

The non-perturbative quantum geometry of the Universal Hypermultiplet (UH) is investigated in N=2 supergravity. The UH low-energy effective action is given by the four-dimensional quaternionic non-linear sigma-model having an U(1)xU(1) isometry. The UH metric is governed by the single real pre-potential that is an eigenfunction of the Laplacian in the hyperbolic plane. We calculate the classical pre-potential corresponding to the standard (Ferrara-Sabharwal) metric of the UH arising in the Calabi-Yau compactification of type-II superstrings. The non-perturbative quaternionic metric, describing the D-instanton contributions to the UH geometry, is found by requiring the SL(2,Z) modular invariance of the UH pre-potential. The pre-potential found is unique, while it coincides with the D-instanton function of Green and Gutperle, given by the order-3/2 Eisenstein series. As a by-product, we prove cluster decomposition of D-instantons in curved spacetime. The non-perturbative UH pre-potential interpolates between the perturbative (large CY volume) region and the superconformal (Landau-Ginzburg) region in the UH moduli space. We also calculate a non-perturbative scalar potential in the hyper-K"ahler limit, when an abelian isometry of the UH metric is gauged in the presence of D-instantons.

hep-th↗
arXiv2002

IIA string instanton corrections to the four-fermion correlator in the intersection of Del Pezzo surfaces

The Becker-Becker-Strominger formula, describing the string world-sheet instanton corrections to the four-fermion correlator in the Calabi-Yau compactified type-IIA superstrings, is calculated in the special case of the Calabi-Yau threefold realized in the intersection of two Del Pezzo surfaces. We also derive the selection rules in the supersymmetric GUT of the Pati-Salam type associated with our construction.

hep-th↗
arXiv2002

Engineering a bosonic AdS/CFT correspondence

We search for a possible bosonic (i.e. non-supersymmetric) string/gauge theory correspondence by using IIB and 0B strings as a guide. Our construction is based on the low-energy bosonic string effective action modified by an extra form flux. The closed string tachyon can be stabilyzed if the AdS scale L does not exceed certain critical value, L<L_c. We argue that the extra form may be generated as a soliton from 3-string junctions, similarly to the known non-perturbative (Jackiw-Rebbi-'t Hooft-Hasenfratz) mechanism in gauge theories. The stable AdS_{13} x S^{13} solution is found, which apparently implies the existence of a 12-dimensional AdS-boundary conformal field theory with the SO(14) global symmetry in the large N 't Hooft limit. We also generalize the conjectured AdS/CFT duality to finite temperature, and calculate the `glueball' masses from the dilaton wave equation in the AdS black hole background, in various spacetime dimensions.

hep-th↗
arXiv2001

D-instantons and universal hypermultiplet

Quantum non-perturbative geometry of the universal hypermultiplet is investigated. We consider the simple case when the D-instantons, originating from the Calabi-Yau wrapped D2-branes, preserve a U(1)xU(1) symmetry of the universal hypermultiplet moduli space. The cluster decomposition of D-instantons is proved to be valid in a curved spacetime. We find an SL(2,Z) duality-invariant quaternionic solution to the effective NLSM metric of the universal hypermultiplet, which is governed by a modular-invariant function. This function appears to be the same function found by Green and Gutperle, and describing the modular invariant completion of the R^4 term by the D-instanton effects in the type-II superstring/M-theory. We argue that our solution interpolates between the perturbative (large CY volume) region and the superconformal (Landau-Ginzburg) region in the universal hypermultiplet moduli space. We also calculate a non-perturbative scalar potential in the hyper-Kähler limit, when an abelian isometry of the universal hypermultiplet moduli space is gauged in the presence of D-instantons.

hep-th↗
arXiv2001

Quantum geometry of the universal hypermultiplet

The universal hypermultiplet moduli space metric in the type-IIA superstring theory compactified on a Calabi-Yau threefold is related to integrable systems. The instanton corrections in four dimensions arise due to multiple wrapping of BPS membranes and fivebranes around certain (supersymmetric) cycles of Calabi-Yau. The exact (non-perturbative) metrics can be calculated in the special cases of (i) the D-instantons (or the wrapped D2-branes) in the absence of fivebranes, and (ii) the fivebrane instantons with vanishing charges, in the absence of D-instantons. The solutions of the first type are governed by the three-dimensional Toda equation, whereas the solutions of the second type are governed by the particular Painleve VI equation.

hep-th↗
arXiv2001

Many faces of Born-Infeld theory

Born-Infeld theory is the non-linear generalization of Maxwell electrodynamics. It naturally arises as the low-energy effective action of open strings, and it is also part of the world-volume effective action of D-branes. The N=1 and N=2 supersymmetric generalizations of the Born-Infeld action are closely related to partial spontaneous breaking of rigid extended supersymmetry. We review some remarkable features of the Born-Infeld action and outline its supersymmetric generalizations in four dimensions. The non-abelian N=1 supersymmetric extension of the Born-Infeld theory and its N=1 supergravitational avatars are given in superspace.

hep-th↗
arXiv2001

4D, N=1 Born-Infeld supergravity

We propose the 4D, N=1 supergravitational analogues (avatars) of the 4D, N=1 supersymmetric Born-Infeld action in four dimensions for the first time, by using superspace. In particular, a new Born-Infeld type generalization of the Weyl supergravity action is given. A natural new Born-Infeld type generalization of the Einstein supergravity is found as well. We also brielfy discuss a construction of the four-dimensional Born-Infeld-Einstein supergravity from the AdS supergravity in five dimensions, which seems to be very natural in our approach.

hep-th↗
arXiv2001

Universal hypermultiplet metrics

Some instanton corrections to the universal hypermultiplet moduli space metric of the type-IIA string theory compactified on a Calabi-Yau threefold arise due to multiple wrapping of BPS membranes and fivebranes around certain cycles of Calabi-Yau. The classical universal hypermultipet metric is locally equivalent to the Bergmann metric of the symmetric quaternionic space SU(2,1)/U(2), whereas its generic quaternionic deformations are governed by the integrable SU(infinity) Toda equation. We calculate the exact (non-perturbative) UH metrics in the special cases of (i) the D-instantons (the wrapped D2-branes) in the absence of fivebranes, and (ii) the fivebrane instantons with vanishing charges, in the absence of D-instantons. The solutions of the first type preserve the U(1)xU(1) classical symmetry, while they can be interpreted as the gravitational dressing of the hyper-K"ahler D-instanton solutions. The second type solution preserves the non-abelian SU(2) classical symmetry, while it can be interpreted as a gradient flow in the universal hypermultiplet moduli space.

hep-th↗
arXiv2001

Gravitational dressing of D-instantons

The non-perturbative corrections to the universal hypermultiplet moduli space metric in the type-IIA superstring compactification on a Calabi-Yau threefold are investigated in the presence of 4d, N=2 supergravity. These corrections come from multiple wrapping of the BPS (Euclidean) D2-branes around certain (BPS) Calabi-Yau 3-cycles, and they are known as the D-instantons. The exact universal hypermultiplet metric is governed by a quaternionic potential that satisfies the SU(\infty) Toda equation. The mechanism is proposed, which elevates any four-dimensional hyper-K"ahler metric with a rotational isometry to the quaternionic metric of the same dimension. A generic separable solution to the Toda equation appears to be related to the Eguchi-Hanson metric, whereas another solution originating from the Atiyah-Hitchin metric describes the gravitationally dressed (mixed) D-instantons.

hep-th↗
arXiv2000

Exact renormalization flow and domain walls from holography

The holographic correspondence between 2d, N=2 quantum field theories and classical 4d, N=2 supergravity coupled to hypermultiplet matter is proposed. The geometrical constraints on the target space of the 4d, N=2 non-linear sigma-models in N=2 supergravity background are interpreted as the exact renormalization group flow equations in two dimensions. Our geometrical description of the renormalization flow is manifestly covariant under general reparametrization of the 2d coupling constants. An explicit exact solution to the 2d renormalization flow, based on its dual holographic description in terms of the Zamolodchikov metric, is considered in the particular case of the four-dimensional NLSM target space described by the SU(2)-invariant (Weyl) anti-self-dual Einstein metrics. The exact regular (Tod-Hitchin) solutions to these metrics are governed by the Painlev'e VI equation, and describe domain walls.

hep-th↗
arXiv2000

Holographic duality, supersymmetry, and Painleve equation

An example of the holographic correspondence between 2d, N=2 quantum field theories and classical 4d, N=2 supergravity theories is found. The constraints on the target space geometry of the 4d, N=2 non-linear sigma-models in N=2 supergravity background are interpreted as the renormalization flow equations in two dimensions. Our geometrical description of the renormalization flow is manifestly covariant under reparametrization of the 2d coupling constants. The proposed holography is described in terms of the (Weyl) anti-self-dual Einstein metrics, whose exact regular (Tod-Hitchin) solutions are governed by the Painleve VI equation.

hep-th↗
arXiv2000

N=1 and N=2 supersymmetric non-abelian Born-Infeld actions from superspace

New non-abelian supersymmetric generalizations of the four-dimensional Born-Infeld action are constructed in N=1 and N=2 superspace, to all orders in the gauge superfield strength. The proposed actions are dictated by simple (manifestly supersymmetric and gauge-covariant) non-linear constraints.

hep-th↗
arXiv2000

N=2 super-Born-Infeld theory revisited

I discuss the symmetry structure of the N=2 supersymmetric extension of the Born-Infeld action in four dimensions, and confirm its interpretation as the Goldstone-Maxwell action associated with partial breaking of N=4 extended supersymmetry down to N=2, by revealing a hidden invariance of the action with respect to two non-linearly realized supersymmetries and two spontaneously broken translations. I also argue about the uniqueness of supersymmetric extension of the Born-Infeld action, and its possible relation to noncommutative geometry.

hep-th↗
arXiv2000

Anomalous N=2 superconformal Ward identities

The N=2 superconformal Ward identities and their anomalies are discussed in N=2 superspace (including N=2 harmonic superspace), at the level of the low-energy effective action (LEEA) in four-dimensional N=2 supersymmetric field theories. The (first) chiral N=2 supergravity compensator is related to the known N=2 anomalous Ward identity in the N=2 (abelian) vector mulitplet sector. As regards the hypermultiplet LEEA given by the N=2 non-linear sigma-model (NLSM), a new anomalous N=2 superconformal Ward identity is found, whose existence is related to the (second) analytic compensator in N=2 supergravity. The celebrated solution of Seiberg and Witten is known to obey the (first) anomalous Ward identity in the Coulomb branch. We find a few solutions to the new anomalous Ward identity, after making certain assumptions about unbroken internal symmetries. Amongst the N=2 NLSM target space metrics governing the hypermultiplet LEEA are the SU(2)-Yang-Mills-Higgs monopole moduli-space metrics that can be encoded in terms of the spectral curves (Riemann surfaces), similarly to the Seiberg-Witten-type solutions. After a dimensional reduction to three spacetime dimensions (3d), our results support the mirror symmetry between the Coulomb and Higgs branches in 3d, N=4 gauge theories.

hep-th↗
arXiv2000

Superconformal hypermultiplets in superspace

We use the manifestly N=2 supersymmetric, off-shell, harmonic (or twistor) superspace approach to solve the constraints implied by four-dimensional N=2 superconformal symmetry on the N=2 non-linear sigma-model target space, known as the special hyper-K"ahler geometry. Our general solution is formulated in terms of a homogeneous (of degree two) function of unconstrained (analytic) Fayet-Sohnius hypermultiplet superfields. We also derive the improved (N=2 superconformal) actions for the off-shell (constrained) N=2 projective hypermultiplets, and relate them (via non-conformal deformations) to the asymptotically locally-flat (ALF) A_k and D_k series of the gravitational instantons. The same metrics describe Kaluza-Klein monopoles in M-theory, while they also arise in the quantum moduli spaces of N=4 supersymmetric gauge field theories with SU(2) gauge group and matter hypermultiplets in three spacetime dimensions. We comment on rotational isometries versus translational isometries in the context of N=2 NLSM in terms of projective hypermultiplets.

hep-th↗