arXiv subjects

Sergey Prokushkin

Publications and source records attributed to Sergey Prokushkin.

13 recordsLinked to original sources

arXiv2004

Squashed Giants: Bound States of Giant Gravitons

We consider giant gravitons in the maximally supersymmetric type IIB plane-wave, in the presence of a constant NSNS B-field background. We show that in response to the background B-field the giant graviton would take the shape of a deformed three-sphere, the size and shape of which depend on the B-field, and that the giant becomes classically unstable once the B-field is larger than a critical value B_{cr}. In particular, for the B-field which is (anti-)self-dual under the SO(4) isometry of the original giant S^3, the closed string metric is that of a round S^3, while the open string metric is a squashed three-sphere. The squashed giant can be interpreted as a bound state of a spherical three-brane and circular D-strings. We work out the spectrum of geometric fluctuations of the squashed giant and study its stability. We also comment on the gauge theory which lives on the brane (which is generically a noncommutative theory) and a possible dual gauge theory description of the deformed giant.

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arXiv2004

Geometric Model for Complex Non-Kaehler Manifolds with SU(3) Structure

For a given complex n-fold M we present an explicit construction of all complex (n+1)-folds which are principal holomorphic T2-fibrations over M. For physical applications we consider the case of M being a Calabi-Yau 2-fold. We show that for such M, there is a subclass of the 3-folds that we construct, which has natural families of non-Kaehler SU(3)-structures satisfying the conditions for N = 1 supersymmetry in the heterotic string theory compactified on the 3-folds. We present examples in the aforementioned subclass with M being a K3-surface and a 4-torus.

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arXiv2004

SuperCosmology

We present a Mathematica package for performing algebraic and numerical computations in cosmological models based on supersymmetric theories. The programs allow for (I) evaluation and study of the properties of a scalar potential in a large class of supergravity models with any number of moduli and arbitrary superpotential, Kahler potential, and D-term; (II) numerical solution of a system of scalar and Friedmann equations for the flat FRW universe, with any number of scalar moduli and arbitrary moduli space metric. We are using here a simple set of first order differential equations which we derived in a Hamiltonian framework. Using our programs we present some new results: (I) a shift-symmetric potential of the inflationary model with a mobile D3 brane in an internal space with stabilized volume; (II) a KKLT-based dark energy model with the acceleration of the universe due to the evolution of the axion partner of the volume modulus. The gzipped package can be downloaded from http://www.stanford.edu/~prok/SuperCosmology/ or from http://www.stanford.edu/~rkallosh/SuperCosmology/

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arXiv2003

On Brane Inflation With Volume Stabilization

The distance between BPS branes in string theory corresponds to a flat direction in the effective potential. Small deviations from supersymmetry may lead to a small uplifting of this flat direction and to brane inflation. However, this scenario can work only if the BPS properties of the branes and the corresponding flatness of the inflaton potential are preserved in the theories with the stable volume compactification. We present an ``inflaton trench'' mechanism that keeps the inflaton potential flat due to shift symmetry, which is related to near BPS symmetry in our model.

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arXiv2003

Properties Of Heterotic Vacua From Superpotentials

We study the superpotential for the heterotic string compactified on non-Kahler complex manifolds. We show that many of the geometrical properties of these manifolds can be understood from the proposed superpotential. In particular we give an estimate of the radial modulus of these manifolds. We also show, how the torsional constraints can be obtained from this superpotential.

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arXiv2002

Supergravity, Dark Energy and the Fate of the Universe

We propose a description of dark energy and acceleration of the universe in extended supergravities with de Sitter (dS) solutions. Some of them are related to M-theory with non-compact internal spaces. Masses of ultra-light scalars in these models are quantized in units of the Hubble constant: m^2 = n H^2. If dS solution corresponds to a minimum of the effective potential, the universe eventually becomes dS space. If dS solution corresponds to a maximum or a saddle point, which is the case in all known models based on N=8 supergravity, the flat universe eventually stops accelerating and collapses to a singularity. We show that in these models, as well as in the simplest models of dark energy based on N=1 supergravity, the typical time remaining before the global collapse is comparable to the present age of the universe, t = O(10^{10}) years. We discuss the possibility of distinguishing between various models and finding our destiny using cosmological observations.

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arXiv2001

Gauged Supergravities, de Sitter Space and Cosmology

We have studied scalar potentials V of gauged N=8,4,2 supergravities in d=4. Extrema of these potentials may correspond to de Sitter, anti de Sitter and Minkowski vacua. All de Sitter extrema that we have studied correspond to unstable maximum/saddle points with negative curvature |V''|=2V for the fields canonically normalized at the extremum. This is equivalent to the relation |m^2| =|R|/2 = 6H^2 for the tachyonic mass m, the curvature scalar R, and the Hubble constant H. This prevents the use of de Sitter extrema for slow-roll inflation in the early universe, which would require |V''| \ll V . Moreover, in all models that we were able to analyse the potential is unbounded from below. On the other hand, barring the question how realistic such models could be, one can use them for the description of the accelerated expansion of the universe at the present epoch. This is related to a novel possibility of the fast-roll inflation with |V''| > V . We also display some potentials that have flat directions with vanishing cosmological constant, and discuss their possible cosmological implications.

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arXiv2001

Domain Walls with Strings Attached

We have constructed a bulk & brane action of IIA theory which describes a pair of BPS domain walls on S_1/Z_2, with strings attached. The walls are given by two orientifold O8-planes with coincident D8-branes and `F1-D0'-strings are stretched between the walls. This static configuration satisfies all matching conditions for the string and domain wall sources and has 1/4 of unbroken supersymmetry.

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arXiv2000

Coordinate-Free Action for AdS3 Higher-Spin-Matter Systems

A coordinate-free action principle for the N=2 supersymmetric model of spin 0 and spin 1/2 matter fields interacting via Chern-Simons higher spin gauge fields in AdS3 is formulated in terms of star-product algebra of two oscillators. Although describing proper relativistic dynamics the action does not contain space-time coordinates. It is given by a supertrace of a forth-order polynomial in the 3d higher spin superalgebra. The theory admits a free parameter characterizing the inequivalent vacua associated with the parameter of mass m of the matter fields. For the case of the massless matter, the model has a form of the noncommutative 2d Yang-Mills theory with some infinite-dimensional gauge group. The limit m\to\infty corresponds to the SU(\infty) 2d Yang-Mills theory.

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arXiv1999

Currents of Arbitrary Spin in $AdS_3$

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arXiv1999

Cohomology of Arbitrary Spin Currents in $AdS_3$

We study conserved currents of any integer or half integer spin built from massless scalar and spinor fields in $AdS_3$. 2-forms dual to the conserved currents in $AdS_3$ are shown to be exact in the class of infinite expansions in higher derivatives of the matter fields with the coefficients containing inverse powers of the cosmological constant. This property has no analog in the flat space and may be related to the holography of the AdS spaces. `Improvements' to the physical currents are described as the trivial local current cohomology class. A complex of spin $s$ currents $(T^s, {\cal D})$ is defined and the cohomology group $H^1(T^s, {\cal D}) = {\bf C}^{2s+1}$ is found. This paper is an extended version of hep-th/9906149.

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arXiv1999

3D Higher-Spin Gauge Theories with Matter

This paper is a letter-type version of hep-th/9806236. We discuss properties of non-linear equations of motion which describe higher-spin gauge interactions for massive spin-0 and spin-1/2 matter fields in 2+1 dimensional anti-de Sitter space. The model is shown to have N=2 supersymmetry and to describe higher-spin interactions of d3 N=2 massive hypermultiplets. An integrating flow is found which reduces the full non-linear system to the free field equations via a non-local Bäcklund-Nicolai-type mapping.

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arXiv1999

Higher-Spin Gauge Interactions for Massive Matter Fields in 3D AdS Space-Time

A remarkable feature of the models with interactions exhibiting higher-spin (HS) gauge symmetries in $d>2$ is that their most symmetric vacua require (anti)-de Sitter (AdS) geometry rather than the flat one. In striking parallelism to what might be expected of M theory HS gauge theories describe infinite towers of fields of all spins and possess naturally space-time SUSY and Chan-Paton type inner symmetries. In this paper, we analyze at the level of the equations of motion the simplest non-trivial HS model which describes HS gauge interactions (on the top of the usual supergravitational and (Chern-Simons) Yang-Mills interactions) of massive spin-0 and spin-1/2 matter fields in d=2+1 AdS space-time. The parameter of mass of the matter fields is identified with the vev of a certain auxiliary field in the model. The matter fields are shown to be arranged into d3 N=2 massive hypermultiplets in certain representations of $U(n)\times U(m)$ Yang-Mills gauge groups. Discrete symmetries of the full system are studied, and the related N=1 supersymmetric truncations with O(n) and Sp(n) Yang-Mills symmetries are constructed. The simplicity of the model allows us to elucidate some general properties of the HS models. In particular, a new result, which can have interesting implications to the higher-dimensional models, is that our model is shown to admit an "integrating" flow that proves existence of a non-local Bäcklund-Nicolai-type mapping to the free system.

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