arXiv subjects

Sergei V. Ketov

Publications and source records attributed to Sergei V. Ketov.

At least 91 records · Page 5Linked to original sources

arXiv2011

Cosmological properties of a generic (\cal R)^2-supergravity

We investigate in detail the structure of the simplest non-trivial F(\cal R)-supergravity model, whose F-function is given by a generic quadratic polynomial in terms of the scalar supercurvature (\cal R). This toy-model admits a fully explicit derivation of the corresponding f(R)-gravity functions. We apply the stability conditions for selecting the physical f(R)-gravity functions, and discuss the phenomenological prospects of F(\cal R)-supergravity in its application to cosmology.

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arXiv2011

Higher-derivative gauge interactions of Bagger-Lambert-Gustavsson theory in N=1 superspace

We study the structure of the gauge sector of the Bagger-Lambert-Gustavsson (BLG) theory in the form proposed by van Raamsdonk, adapted to 3D, N=1 superspace. By using the novel Higgs mechanism proposed by Mukhi and Papageorgakis, we derive the manifestly N=1 supersymmetric higher-order terms (beyond the supersymmetric Yang-Mills action) that follow from the BLG theory in its expansion with respect to the inverse gauge coupling constant squared. We find that all those terms have at least one anti-commutator of the super-YM field strength superfields as a factor, and thus are reducible to the SYM terms with the higher (spacetime) derivatives.

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arXiv2010

Chaotic inflation in F(R) supergravity

The bosonic f(R) gravity function is derived from a chiral F(R) supergravity model for the first time. We find an existence of the upper limit (or AdS bound) on the scalar curvature, as well as a solution with a vanishing cosmological constant. We compare our simple model of F(R) supergravity to the well known Starobinsky model of chaotic inflation.

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arXiv2009

Seeking the Loop Quantum Gravity Barbero-Immirzi Parameter and Field in 4D, $\cal N$ = 1 Supergravity

We embed the Loop Quantum Gravity Barbero-Immirzi parameter and field within an action describing 4D, $\cal N$ = 1 supergravity and thus within a Low Energy Effective Action of Superstring/M-Theory. We use the fully gauge-covariant description of supergravity in (curved) superspace. The gravitational constant is replaced with the vacuum expectation value of a scalar field, which in local supersymmetry is promoted to a complex, covariantly chiral scalar superfield. The imaginary part of this superfield couples to a supersymmetric Holst term. The Holst term also serves as a starting point in the Loop Quantum Gravity action. This suggest the possibility of a relation between Loop Quantum Gravity and supersymmetric string theory, where the Barbero-Immirzi parameter and field of the former play the role of the supersymmetric axion in the latter. Adding matter fermions in Loop Quantum Gravity may require the extension of the Holst action through the Nieh-Yan topological invariant, while in pure, matter-free supergravity their supersymmetric extensions are the same. We show that, when the Barbero-Immirzi parameter is promoted to a field in the context of 4D supergravity, it is equivalent to adding a dynamical complex chiral (dilaton-axion) superfield with a non-trivial kinetic term (or Kähler potential), coupled to supergravity.

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arXiv2009

Scalar potential in F(R) supergravity

We derive a scalar potential in the recently proposed N=1 supersymmetric generalization of f(R) gravity in four space-time dimensions. Any such higher-derivative supergravity is classically equivalent to the standard N=1 supergravity coupled to a chiral (matter) superfield, via a Legendre-Weyl transform in superspace. The Kaehler potential, the superpotential and the scalar potential of that theory are all governed by a single holomorphic function. We also find the conditions for the vanishing cosmological constant and spontaneous supersymmetry breaking, without fine-tuning, which define a no-scale F(R) supergravity. The F(R) supergravities are suitable for physical applications in the inflationary cosmology based on supergravity and superstrings.

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arXiv2009

Superstring-inspired supergravity as the universal source of inflation and quintessence

We prove (in superspace) the equivalence between the higher-derivative N=1 supergravity, defined by a holomorphic function F of the chiral scalar curvature superfield, and the standard theory of a chiral scalar superfield with a chiral superpotential W, coupled to the (minimal) Poincare supergravity in four spacetime dimensions. The relation between the holomorphic functions F and W is found. It can be used as the technical framework for the possible scenario unifying the early Universe inflation and the present Universe acceleration. We speculate on the possible origin of our model as the effective supergravity generated by quantum superstrings, with a dilaton-axion field as the leading field component of the chiral superfield.

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arXiv2008

On the superstrings-induced four-dimensional gravity, and its applications to cosmology

We review the status of the fourth-order (quartic in the spacetime curvature) terms induced by superstrings/M-theory (compactified on a warped torus) in the leading order with respect to the Regge slope parameter, and study their (non-perturbative) impact on the evolution of the Hubble scale in the context of the four-dimensional FRW cosmology. After taking into account the quantum ambiguities in the definition of the off-shell superstring effective action, we propose the generalized Friedmann equations, find the existence of their (de Sitter) exact inflationary solutions without a spacetime singularity, and constrain the ambiguities by demanding stability and the scale factor duality invariance of our solutions. The most naive (Bel-Robinson tensor squared) quartic terms are ruled out, thus giving the evidence for the necessity of extra quartic (Ricci tensor-dependent) terms in the off-shell gravitational effective action for superstrings. Our methods are generalizable to the higher orders in the spacetime curvature.

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arXiv2008

Non-anticommutative solitons

Certain supersymmetric sigma models in 2+1 dimensions feature multi-soliton solutions, with and without scattering. We subject these systems to a non-anticommutative deformation by replacing the Grassmann algebra of the odd superspace coordinates with a Clifford algebra. Static CP^1 and scattering U(2) solitons are constructed and carry an additional spin-1/2 degree of freedom due to the deformation. Abelian BPS solutions exist as well but have infinite action, in contrast to the Moyal case.

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arXiv2007

N=1/2 supergravity with matter in four Euclidean dimensions

An N=1/2 supergravity in four Euclidean spacetime dimensions, coupled to both vector- and scalar-multiplet matter, is constructed for the first time. We begin with the standard (1,1) conformally extended supergravity in four Euclidean dimensions, and freeze out the graviphoton field strength to an arbitrary (fixed) self-dual field (the so-called C-deformation). Though a consistency of such procedure with local supersymmetry is not guaranteed, we find a simple consistent set of algebraic constraints that reduce the local supersymmetry by 3/4 and eliminate the corresponding gravitini. The final field theory (after the superconformal gauge-fixing) has the residual local N=(0,1/2) or just N=1/2 supersymmetry with only one chiral gravitino as the corresponding gauge field. Our theory is not `Lorentz'-invariant because of the non-vanishing self-dual graviphoton vacuum expectation value, which is common to the C-deformed N=1/2 rigidly supersymmetric field theories constructed in a non-anticommutative superspace.

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arXiv2007

Conformally flat FRW metrics

We find a new family of non-separable coordinate transformations bringing the FRW metrics into the manifestly conformally flat form. Our results are simple and complete, while our derivation is quite explicit. We also calculate all the FRW curvatures, including the Weyl tensor.

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arXiv2004

SU(2)xU(1) non-anticommutative N=2 supersymmetric gauge theory

We derive the master function governing the component action of the four-dimensional non-anticommutative (NAC) and fully N=2 supersymmetric gauge field theory with a non-simple gauge group U(2)=SU(2)xU(1). We use a Lorentz singlet NAC-deformation parameter and an N=2 supersymmetric star (Moyal) product which do not break any of the fundamental symmetries of the undeformed N=2 gauge theory. The scalar potential in the NAC-deformed theory is calculated. We also propose the non-abelian BPS-type equations in the case of the NAC-deformed N=2 gauge theory with the SU(2) gauge group, and comment on the SU(3) case too. The NAC-deformed field theories can be thought of as the effective (non-perturbative) N=2 gauge field theories in a certain (scalar only) N=2 supergravity background.

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arXiv2004

D-instanton sums for matter hypermultiplets

We calculate some non-perturbative (D-instanton) quantum corrections to the moduli space metric of several (n>1) identical matter hypermultiplets for the type-IIA superstrings compactified on a Calabi-Yau threefold, near conifold singularities. We find a non-trivial deformation of the (real) 4n-dimensional hypermultiplet moduli space metric due to the infinite number of D-instantons, under the assumption of n tri-holomorphic commuting isometries of the metric, in the hyper-K"ahler limit (i.e. in the absence of gravitational corrections).

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arXiv2004

Non-anticommutative N=2 supersymmetric SU(2) gauge theory

We calculate the component Lagrangian of a four-dimensional non-anticommutative (with a singlet deformation parameter) and fully N=2 supersymmetric gauge field theory with the simple gauge group SU(2). We find that the deformed (classical) scalar potential is unbounded from below, in contrast to the undeformed case.

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arXiv2004

BPS-type equations in the non-anticommutative N=2 supersymmetric U(1) gauge theory

We investigate the equations of motion in the four-dimensional non-anticommutative N=2 supersymmetric U(1) gauge field theory, in the search for BPS configurations. The BPS-like equations, generalizing the abelian (anti)self-duality conditions, are proposed. We prove full solvability of our BPS-like equations, as well their consistency with the equations of motion. Certain restrictions on the allowed scalar field values are also found. Surviving supersymmetry is briefly discussed too.

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arXiv2003

On the universality of goldstino action

We find the Goldstino action descending from the N=1 Goldstone-Maxwell superfield action associated with the spontaneous partial supersymmetry breaking, N=2 to N=1, in superspace. The new Goldstino action has higher (second-order) spacetime derivatives, while it can be most compactly described as a solution to the simple recursive relation. Our action seems to be related to the standard (having only the first-order derivatives) Akulov-Volkov action for Goldstino via a field redefinition.

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arXiv2003

More on the gauge-fixed D3-brane action with dilaton-axion coupling from N=1 superspace

The gauge-fixed action of a `spacetime-filling' D3-brane with dilaton-axion coupling is formulated in N=1 superspace. We investigate its symmetries by paying special attention to a possible non-linearly realized extra (hidden) supersymmetry, and emphasize the need of a linear superfield coupled to an abelian Chern-Simons superfield to represent a dilaton-axion supermultiplet in the off-shell manifestly supersymmetric approach.

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arXiv2003

D-instantons and matter hypermultiplet

We calculate the D-instanton corrections (with all D-instanton numbers) to the quantum moduli space metric of a single matter hypermultiplet with toric isometry, in the effective N=2 supergravity arising in type-IIA superstrings compactified on a Calabi-Yau (CY) threefold of Hodge number h_{2,1}=1. The non-perturbative quaternionic hypermultiplet metric is derived by resolution of a complex orbifold singularity, thus generalizing the known (Ooguri-Vafa) solution in flat spacetime to N=2 supergravity.

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arXiv2003

Instanton-induced scalar potential for the universal hypermultiplet

We calculate the scalar potential in the gauged N=2 supergravity with a single hypermultiplet, whose generic quaternionic moduli space metric has an abelian isometry. This isometry is gauged by the use of a graviphoton gauge field. The hypermultiplet metric and the scalar potential are both governed by the single real potential that is a solution to the 3d (integrable) continuous Toda equation. An explicit solution, controlled by the Eisenstein series E_{3/2}, is found in the case of the D-instanton-corrected universal hypermultilet moduli space metric having an U(1)xU(1) isometry, with one of the isometries being gauged.

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