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Dmitri V. Gal'tsov

Publications and source records attributed to Dmitri V. Gal'tsov.

At least 37 records · Page 2Linked to original sources
arXiv2008

Generating technique for $U(1)^3 5D$ supergravity

We develop generating technique for solutions of $U(1)^3 5D$ supergravity via dimensional reduction to three dimensions. This theory, which recently attracted attention in connection with black rings, can be viewed as consistent truncation of the $T^6$ compactification of the eleven-dimensional supergravity. Its further reduction to three dimensions accompanied by dualisation of the vector fields leads to 3D gravity coupled sigma model on the homogeneous space $SO(4,4)/SO(4)\times SO(4)$ or $SO(4,4)/SO(2,2)\times SO(2,2)$ depending on the signature of the three-space. We construct a $8\times 8$ matrix representation of these cosets in terms of lower-dimensional blocks. Using it we express solution generating transformations in terms of the potentials and identify those preserving asymptotic conditions relevant to black holes and black rings. As an application, we derive the doubly rotating black hole solution with three independent charges. A suitable contraction of the above cosets is used to construct a new representation of the coset $G_{2(2)}/(SL(2,R)\times SL(2,R))$ relevant for minimal five-dimensional supergravity.

hep-th↗
arXiv2008

$G_2$ generating technique for minimal D=5 supergravity and black rings

A solution generating technique is developed for D=5 minimal supergravity with two commuting Killing vectors based on the $G_2$ U-duality arising in the reduction of the theory to three dimensions. The target space of the corresponding 3-dimensional sigma-model is the coset $G_{2(2)}/(SL(2,R)\times SL(2,R))$. Its isometries constitute the set of solution generating symmetries. These include two electric and two magnetic Harrison transformations with the corresponding two pairs of gauge transformations, three $SL(2,R) S$-duality transformations, and the three gravitational scale, gauge and Ehlers transformations (altogether 14). We construct a representation of the coset in terms of $7\times 7$ matrices realizing the automorphisms of split octonions. Generating a new solution amounts to transforming the coset matrices by one-parametric subgroups of $G_{2(2)}$ and subsequently solving the dualization equations. Using this formalism we derive a new charged black ring solution with two independent parameters of rotation.

hep-th↗
arXiv2007

Extremal black holes in D=4 Gauss-Bonnet gravity

We show that four-dimensional Einstein-Maxwell-Dilaton-Gauss-Bonnet gravity admits asymptotically flat black hole solutions with a degenerate event horizon of the Reissner-Nordström type $AdS_2\times S^2$. Such black holes exist for the dilaton coupling constant within the interval $0\leq a^2<a^2_{\rm cr}$. Black holes must be endowed with an electric charge and (possibly) with magnetic charge (dyons) but they can not be purely magnetic. Purely electric solutions are constructed numerically and the critical dilaton coupling is determined $a_{\rm cr}\simeq 0.488219703$. For each value of the dilaton coupling $a$ within this interval and for a fixed value of the Gauss--Bonnet coupling $α$ we have a family of black holes parameterized by their electric charge. Relation between the mass, the electric charge and the dilaton charge at both ends of the allowed interval of $a$ is reminiscent of the BPS condition for dilaton black holes in the Einstein-Maxwell-Dilaton theory. The entropy of the DGB extremal black holes is twice the Bekenstein-Hawking entropy.

hep-th↗
arXiv2006

Cylindrically symmetric solitons in Einstein-Yang-Mills theory

Recently new Einstein-Yang-Mills (EYM) soliton solutions were presented which describe superconducting strings with Kasner asymptotic (hep-th/0610183). Here we study the static cylindrically symmetric SU(2) EYM system in more detail. The ansatz for the gauge field corresponds to superposition of the azimuthal $B_ϕ$ and the longitudinal $B_z$ components of the color magnetic field. We derive sum rules relating data on the symmetry axis to asymptotic data and show that generic asymptotic structure of regular solutions is Kasner. Solutions starting with vacuum data on the axis generically are divergent. Regular solutions correspond to some bifurcation manifold in the space of parameters which has the low-energy limiting point corresponding to string solutions in flat space (with the divergent total energy) and the high-curvature point where gravity is crucial. Some analytical results are presented for the low energy limit, and numerical bifurcation curves are constructed in the gravitating case. Depending on the parameters, the solution looks like a straight string or a pair of straight and circular strings. The existence of such non-linear superposition of two strings becomes possible due to self-interaction terms in the Yang-Mills action which suppress contribution of the circular string near the polar axis.

hep-th↗
arXiv2006

Einstein--Yang--Mills strings

We present globally regular vortex-type solutions for a pure SU(2) Yang-Mills field coupled to gravity in 3+1 dimensions. These gravitating vortices are static, cylindrically symmetric and purely magnetic, and they support a non-zero chromo-magnetic flux through their cross section. In addition, they carry a constant non-Abelian current, and so in some sense they are analogs of the superconducting cosmic strings. They have a compact central core dominated by a longitudinal magnetic field and endowed with an approximately Melvin geometry. This magnetic field component gets color screened in the exterior part of the core, outside of which the fields approach exponentially fast those of the electrovacuum Bonnor solutions with a circular magnetic field. In the far field zone the solutions are not asymptotically flat but tend to vacuum Kasner metrics.

hep-th↗
arXiv2005

Intersecting Non-extreme p-Branes and Linear Dilaton Background

We construct the general static solution to the supergravity action containing gravity, the dilaton and a set of antisymmetric forms describing the intersecting branes delocalized in the relative transverse dimensions. The solution is obtained by reducing the system to a set of separate Liouville equations (the intersection rules implying the separability); it contains the maximal number of free parameters corresponding to the rank of the differential equations. Imposing the requirement of the absence of naked singularities, we show that the general configurations are restricted to two and only two classes: the usual asymptotically flat intersecting branes, and the intersecting branes some of which are asymptotically flat and some approach the linear dilaton background at infinity. In both cases the configurations are black. These are supposed to be relevant for the description of the thermal phase of the QFT's in the corresponding Domain-Wall/QFT duality.

hep-th↗
arXiv2005

Chaos-order transition in Bianchi I non-Abelian Born-Infeld cosmology

We investigate the Bianchi I cosmology with the homogeneous SU(2) Yang-Mills field governed by the non-Abelian Born-Infeld action. Similar system with the standard Einstein-Yang-Mills (EYM) action is known to exhibit chaotic behavior induced by the Yang-Mills field. When the action is replaced by the Born-Infeld-type non-Abelian action (NBI), the chaos-order transition is observed in the high energy region. This is interpreted as a smothering effect due to (non-perturbative in $alpha'$) string corrections to the classical EYM action. We give a numerical evidence for the chaos-order transition, and present an analytical proof of regularity of color oscillations in the limit of strong Born-Infeld non-linearity. We also perform some general analysis of the Bianchi I NBI cosmology and derive an exact solution in the case when only the U(1) component of the Yang-Mills field is excited. Our new exact solution generalizes the Rosen solution to the Bianchi I Einstein-Maxwell cosmology to the U(1) Einstein-Born-Infeld theory.

hep-th↗
arXiv2004

Radiation reaction reexamined: bound momentum and Schott term

We review and compare two different approaches to radiation reaction in classical electrodynamics of point charges: a local calculation of the self-force using the charge equation of motion and a global calculation consisting in integration of the electromagnetic energy-momentum flux through a hypersurface encircling the world-line. Both approaches are complementary and, being combined together, give rise to an identity relating the locally and globally computed forces. From this identity it follows that the Schott terms in the Abraham force should arise from the bound field momentum and can not be introduced by hand as an additional term in the mechanical momentum of an accelerated charge. This is in perfect agreement with the results of Dirac and Teitelboim, but disagrees with the recent calculation of the bound momentum in the retarded coordinates. We perform an independent calculation of the bound electromagnetic momentum and verify explicitly that the Schott term is the derivative of the finite part of the bound momentum indeed. The failure to obtain the same result using the method of retarded coordinates tentatively lies in an inappropriate choice of the integration surface. We also discuss the definition of the delta-function on the semi-axis involved in the local calculation of the radiation reaction force and demonstrate inconsistency of one recent proposal.

hep-th↗
arXiv2004

Supergravity p-branes revisited: extra parameters, uniqueness, and topological censorship

We perform a complete integration of the Einstein-dilaton-antisymmetric form action describing black p-branes in arbitrary dimensions assuming the transverse space to be homogeneous and possessing spherical, toroidal or hyperbolic topology. The generic solution contains eight parameters satisfying one constraint. Asymptotically flat solutions form a five-parametric subspace, while conditions of regularity of the non-degenerate event horizon further restrict this number to three, which can be related to the mass and the charge densities and the asymptotic value of the dilaton. In the case of a degenerate horizon, this number is reduced by one. Our derivation constitutes a constructive proof of the uniqueness theorem for $p$-branes with the homogeneous transverse space. No asymptotically flat solutions with toroidal or hyperbolic transverse space within the considered class are shown to exist, which result can be viewed as a demonstration of the topological censorship for p-branes. From our considerations it follows, in particular, that some previously discussed p-brane-like solutions with extra parameters do not satisfy the standard conditions of asymptotic flatness and absence of naked singularities. We also explore the same system in presence of a cosmological constant, and derive a complete analytic solution for higher-dimensional charged topological black holes, thus proving their uniqueness.

hep-th↗
arXiv2002

Impact of CP phases on the search for sleptons tau and nu_tau

We study the decays of the tau-sleptons (stau_{1,2}) and tau-sneutrino (snu_tau) in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters A_tau, mu and M_1 (U(1) gaugino mass). We show that the effect of the CP phases of these parameters on the branching ratios of stau_{1,2} and snu_tau decays can be quite strong in a large region of the MSSM parameter space. This could have an important impact on the search for stau_{1,2} and snu_tau and the determination of the MSSM parameters at future colliders.

hep-ph↗
arXiv2001

Supergravity Fluxbranes in Various Dimensions

We investigate fluxbrane solutions to the Einstein-antisymmetric form-dilaton theory in arbitrary space-time dimensions for a transverse space of cylindrical topology $S^k\times R^n$, corresponding to smeared and unsmeared solutions. A master equation for a single metric function is derived. This is a non-linear second-order ordinary differential equation admitting an analytic solution, singular at the origin, which serves as an attractor for globally regular solutions, whose existence is demonstrated numerically. For all fluxbranes of different levels of smearing the metric function diverges at infinity as the same power of the radial coordinate except for the maximally smeared case, where a global solution is known in closed form and can be obtained algebraically using U-duality. The particular cases of F6 and F3 fluxbranes in D=11 supergravity and fluxbranes in IIA, IIB supergravities are discussed.

hep-th↗
arXiv2001

Inverse dualisation and non-local dualities between Einstein gravity and supergravities

We investigate non-local dualities between suitably compactified higher-dimensional Einstein gravity and supergravities which can be revealed if one reinterprets the dualised Kaluza-Klein two-forms in $D>4$ as antisymmetric forms belonging to supergravities. We find several examples of such a correspondence including one between the six-dimensional Einstein gravity and the four-dimensional Einstein-Maxwell-dilaton-axion theory (truncated N=4 supergravity), and others between the compactified eleven and ten-dimensional supergravities and the eight or ten-dimensional pure gravity. The Killing spinor equation of the D=11 supergravity is shown to be equivalent to the geometric Killing spinor equation in the dual gravity. We give several examples of using new dualities for solution generation and demonstrate how $p$-branes can be interpreted as non-local duals of pure gravity solutions. New supersymmetric solutions are presented including $M2\subset 5$-brane with two rotation parameters.

hep-th↗
arXiv2001

No-go theorem for false vacuum black holes

We study the possibility of non-singular black hole solutions in the theory of general relativity coupled to a non-linear scalar field with a positive potential possessing two minima: a `false vacuum' with positive energy and a `true vacuum' with zero energy. Assuming that the scalar field starts at the false vacuum at the origin and comes to the true vacuum at spatial infinity, we prove a no-go theorem by extending a no-hair theorem to the black hole interior: no smooth solutions exist which interpolate between the local de Sitter solution near the origin and the asymptotic Schwarzschild solution through a regular event horizon or several horizons.

gr-qc↗
arXiv2000

Gravitational and dilaton radiation from a relativistic membrane

Recent scenarios of the TeV-scale brane cosmology suggest a possibility of existence in the early universe of two-dimensional topological defects: relativistic membranes. Like cosmic strings, oscillating membranes could emit gravitational radiation contributing to a stochastic background of gravitational waves. We calculate dilaton and gravitational radiation from a closed toroidal membrane excited along one homology cycle. The spectral-angular distributions of dilaton and gravitational radiation are obtained in a closed form in terms of Bessel's functions. The angular distributions are affected by oscillating factors due to an interference of radiation from different segments of the membrane. The dilaton radiation power is dominated by a few lower harmonics of the basic frequency, while the spectrum of the gravitational radiation contains also a substantial contribution from higher harmonics. The radiative lifetime of the membrane is determined by its tension and depends weakly on the ratio of two radii of the torus. Qualitatively it is equal to the ratio of the membrane area at the maximal extension to the gravitational radius of the membrane as a whole.

gr-qc↗
arXiv1999

Einstein Gravity - Supergravity Correspondence

A correspondence between the three-block truncated 11D supergravity and the 8D pure Einstein gravity with two commuting Killing symmetries is discussed. The Kaluza-Klein two-forms of the 6D theory obtained after dimensional reduction along the Killing orbits generate the four-form field of supergravity via an inverse dualization. Thus any solution to the vacuum Einstein equations in eight dimensions depending on six coordinates have 11D-supergravity counterparts with the non-trivial four-form field. Using this proposed duality we derive a new dyon solution of 11D supergravity describing the M2 and M5-branes intersecting at a point.

hep-th↗
arXiv1999

Gravitating Non-Abelian Solitons and Black Holes with Yang-Mills Fields

We present a review of gravitating particle-like and black hole solutions with non-Abelian gauge fields. The emphasis is given to the description of the structure of the solutions and to the connection with the results of flat space soliton physics. We describe the Bartnik-McKinnon solitons and the non-Abelian black holes arising in the Einstein-Yang-Mills theory, and their various generalizations. These include axially symmetric and slowly rotating configurations, solutions with higher gauge groups, $Λ$-term, dilaton, and higher curvature corrections. The stability issue is discussed as well. We also describe the gravitating generalizations for flat space monopoles, sphalerons, and Skyrmions.

hep-th↗
arXiv1999

Intersecting M-Fluxbranes

New solution to the six-dimensional vacuum Einstein's equations is constructed as a non-linear superposition of two five-dimensional solutions representing the Melvin-Gibbons-Maeda Universe and its S-dual. Then using duality between D=8 vacuum and a certain class of D=11 supergravity configurations we generate M2 and M5 fluxbranes as well as some of their intersections also including waves and KK-monopoles.

hep-th↗