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V. D. Ivashchuk

Publications and source records attributed to V. D. Ivashchuk.

At least 127 records · Page 7Linked to original sources
arXiv1998

On Symmetries of Target Space for Sigma-model of p-brane Origin

The target space M for the sigma-model appearing in theories with p-branes is considered. It is proved that M is a homogeneous space G/H. It is symmetric if and only if the U-vectors governing the sigma-model metric are either coinciding or mutually orthogonal. For nonzero noncoinciding U-vectors the Killing equations are solved. Using a block-orthogonal decomposition of the set of the U-vectors it is shown that under rather general assumptions the algebra of Killing vectors is a direct sum of several copies of sl(2,R) algebras (corresponding to 1-vector blocks), several solvable Lie algebras (corresponding to multivector blocks) and the Killing algebra of a flat space. The target space manifold is decomposed in a product of a flat space, several 2-dimensional spaces of constant curvature (e.g. Lobachevsky space, part of anti-de Sitter space) and several solvable Lie group manifolds.

hep-th↗
arXiv1998

Multidimensional Cosmology for Intersecting p-Branes with Static Internal Spaces

Multidimensional cosmological model with static internal spaces describing the evolution of an Einstein space of non-zero curvature and n internal spaces is considered. The action contains several dilatonic scalar fields and antisymmetric forms and lambda-term. When forms are chosen to be proportional to volume forms of p-brane submanifolds of internal space manifold, the Toda-like Lagrange representation arises. Exact solutions for the model are obtained, when scale factors of internal spaces are constant. It is shown that they are de Sitter or anti-de Sitter. Behaviour of cosmological constant and its generation by p-branes is demonstrated.

gr-qc↗
arXiv1998

Composite p-branes on Product of Einstein Spaces

A multidimensional gravitational model with several scalar fields, fields of forms and cosmological constant is considered. When scalar fields are constant and composite p-brane monopole-like ansatz for the fields of forms is adopted, a wide class of solutions on product of n+1 Einstein spaces is obtained. These solutions are the composite p-brane generalizations of the Freund-Rubin solution. Some examples including the AdS_m x S^k x... solutions are considered.

hep-th↗
arXiv1997

Multidimensional sigma-models with composite electric p-branes

We consider a gravitational model on a manifold M = M_0 x M_1 x...x M_n with oriented connected Einstein internal spaces M_1,...,M_n. The matter part of the action contains several scalar fields and antisymmetric forms. With Ricci-flat internal spaces, the model has a midisuperspace representation in form of a sigma-model on M_0. The latter can be used to determine exact composite electric p-brane solutions, which depend on a set of harmonic functions on M_0.

gr-qc↗
arXiv1997

The Reissner-Nordstrom Problem for Intersecting Electric and Magnetic p-Branes

A multidimensional model with (at most) one curved factor space and n Ricci-flat internal spaces is considered, with arbitrary numbers of dilatonic scalar fields and antisymmetric forms of both electric and magnetic types, associated with p-branes in theories like M-theory. The problem setting covers, in particular, homogeneous cosmologies, static, spherically symmetric and Euclidean models. Exact solutions are obtained when the p-brane dimensions and the dilatonic couplings obey orthogonality conditions in minisuperspace. Conditions for black hole and wormhole existence among static models are formulated. For black holes, a kind of no-hair theorem, leading to F-form selection, is obtained; it is shown that even in spaces with multiple times a black hole may only exist with its unique, one-dimensional time; infinite Hawking temperature is explicitly shown to imply a curvature singularity at an assumed horizon, and such cases among extreme black-hole solutions are indicated.

gr-qc↗
arXiv1997

Integrable Multidimensional Cosmology for Intersecting $p$-Branes

A multidimensional field model describing the behaviour of (at most) one Einstein space of non-zero curvature and n Ricci-flat internal spaces is considered. The action contains several dilatonic scalar fields and antisymmetric forms. The problem setting covers various problems with field dependence on a single space-time coordinate, in particular, isotropic and anisotropic homogeneous cosmologies. When the forms are chosen to be proportional to volume forms of p-brane factor spaces, a Toda-like Lagrange representation arises. Exact solutions are obtained when the p-brane dimensions and the dilatonic couplings obey some orthogonality conditions. General features and some special cases of cosmological solutions are discussed. It is shown, in particular, that all hyperbolic models with a 3-dimensional external space possess an asymptotic with the external scale factor a(t) is proportional to |t| (the cosmic time), while all internal scale factors and all scalar fields tend to finite limits. For D=11 a family of models with one 5-brane and three 2-branes is described.

gr-qc↗
arXiv1997

Multidimensional Classical and Quantum Cosmology with Intersecting p-branes

Multidimensional cosmological model describing the evolution of n+1 Einstein spaces in the theory with several scalar fields and forms is considered. When a (electro-magnetic composite) p-brane Ansatz is adopted the field equations are reduced to the equations for Toda-like system. The Wheeler-De Witt equation is obtained. In the case when n "internal" spaces are Ricci-flat, one space M_0 has a non-zero curvature, and all p-branes do not "live" in M_0, the classical and quantum solutions are obtained if certain orthogonality relations on parameters are imposed. Spherically-symmetric solutions with intersecting non-extremal p-branes are singled out. A non-orthogonal generalization of intersection rules corresponding to (open, closed) Toda lattices is obtained. A chain of bosonic D > 11 models (that may be related to hypothetical higher dimensional supergravities and F-theories) is suggested.

hep-th↗
arXiv1997

Integrable Multidimensional Classical and Quantum Cosmology for Intersecting p-branes

Multidimensional cosmological model describing the evolution of one Einstein space of non-zero curvature and n Ricci-flat internal spaces is considered. The action contains several dilatonic scalar fields and antisymmetric forms. When forms are chosen to be proportional of volume forms of p-brane submanifolds of internal space manifold, the Toda-like Lagrange representation is obtained. Wheeler-De Witt equation for the model is presented. The exact solutions in classical and quantum cases are obtained when dimensions of p-branes and dilatonic couplings obey some orthogonality conditions.

gr-qc↗
arXiv1996

Intersecting p-brane Solutions in Multidimensional Gravity and M-theory

Multidimensional gravitational model on the manifold $M = M_0 \times \prod_{i=1}^{n} M_i$, where $M_i$ are Einstein spaces ($i \geq 1$), is considered. The action contains $m = 2^n -1$ dilatonic scalar fields $ϕ^I$ and $m$ (antisymmetric) forms $A^I$. When all fields and scale factors of the metric depend (essentially) on the point of $M_0$ and any $A^I$ is "proportional" to the volume form of submanifold $M_{i_1} \times ... \times M_{i_k}$, $1 \leq i_1 < ... < i_k \leq n$, the sigma-model representation is obtained. A family of "Majumdar-Papapetrou type" solutions are obtained, when all $M_ν$ are Ricci-flat. A special class of solutions (related to the solution of some Diophantus equation on dimensions of $M_ν$) is singled out. Some examples of intersecting p-branes (e.g. solution with seven Euclidean 2-branes for D = 11 supergravity) are considered.}

hep-th↗
arXiv1996

Multidimensional Gravity with Einstein Internal Spaces

A multidimensional gravitational model on the manifold $M = M_0 \times \prod_{i=1}^{n} M_i$, where M_i are Einstein spaces ($i \geq 1$), is studied. For $N_0 = dim M_0 > 2$ the $σ$ model representation is considered and it is shown that the corresponding Euclidean Toda-like system does not satisfy the Adler-van-Moerbeke criterion. For $M_0 = R^{N_0}$, $N_0 = 3, 4, 6$ (and the total dimension $D = dim M = 11, 10, 11$, respectively) nonsingular spherically symmetric solutions to vacuum Einstein equations are obtained and their generalizations to arbitrary signatures are considered. It is proved that for a non-Euclidean signature the Riemann tensor squared of the solutions diverges on certain hypersurfaces in $R^{N_0}$.

hep-th↗
arXiv1996

Multidimensional Extremal Dilatonic Black Holes in String-like Model with Cosmological Term

A string-like model with the "cosmological constant" $Λ$ is considered. The Maki-Shiraishi multi-black-hole solution \cite{MS1} is generalized to space-times with a Ricci-flat internal space. For $Λ= 0$ the obtained solution in the one-black-hole case is shown to coincide with the extreme limit of the charged dilatonic black hole solution \cite{BI,BM}. The Hawking temperature $T_H$ for the solution \cite{BI,BM} is presented and its extreme limit is considered. For the string value of dilatonic coupling the temperature $T_H$ does not depend upon the internal space dimension.

hep-th↗
arXiv1996

Multidimensional integrable vacuum cosmology with two curvatures

The vacuum cosmological model on the manifold $R \times M_1 \times \ldots \times M_n$ describing the evolution of $n$ Einstein spaces of non-zero curvatures is considered. For $n = 2$ the Einstein equations are reduced to the Abel (ordinary differential) equation and solved, when $(N_1 = $dim $ M_1, N_2 = $ dim$ M_2) = (6,3), (5,5), (8,2)$. The Kasner-like behaviour of the solutions near the singularity $t_s \to +0$ is considered ($t_s$ is synchronous time). The exceptional ("Milne-type") solutions are obtained for arbitrary $n$. For $n=2$ these solutions are attractors for other ones, when $t_s \to + \infty$. For dim $ M = 10, 11$ and $3 \leq n \leq 5$ certain two-parametric families of solutions are obtained from $n=2$ ones using "curvature-splitting" trick. In the case $n=2$, $(N_1, N_2)= (6,3)$ a family of non-singular solutions with the topology $R^7 \times M_2$ is found.

gr-qc↗
arXiv1995

On singular solutions in multidimensional gravity

It is proved that the Riemann tensor squared is divergent as $τ\ra 0$ for a wide class of cosmological metrics with non-exceptional Kasner-like behaviour of scale factors as $τ\ra 0$, where $τ$ is synchronous time. Using this result it is shown that any non-trivial generalization of the spherically-symmetric Tangherlini solution to the case of $n$ Ricci-flat internal spaces \cite{FIM} has a divergent Riemann tensor squared as $R \ra R_0$, where $R_0$ is parameter of length of the solution. Multitemporal naked singularities are also considered.

gr-qc↗
arXiv1994

Billiard Representation for Multidimensional Quantum Cosmology near the Singularity

The degenerate Lagrangian system describing a lot of cosmological models is considered. When certain restrictions on the parameters of the model are imposed, the dynamics of the model near the "singularity" is reduced to a billiard on the Lobachevsky space. The Wheeler-DeWitt equation in the asymptotical regime is solved and a third-quantized model is suggested.

gr-qc↗
arXiv1994

Billiard Representation for Multidimensional Cosmology with Multicomponent Perfect Fluid near the Singularity

The multidimensional cosmological model describing the evolution of $n$ Einstein spaces in the presence of multicomponent perfect fluid is considered. When certain restrictions on the parameters of the model are imposed, the dynamics of the model near the singularity is reduced to a billiard on the $(n-1)$-dimensional Lobachevsky space $H^{n-1}$. The geometrical criterion for the finiteness of the billiard volume and its compactness is suggested. This criterion reduces the problem to the problem of illumination of $(n-2)$-dimensional sphere $S^{n-2}$ by point-like sources. Some generalization of the considered scheme (including scalar field and quantum generalizations) are considered.

gr-qc↗
arXiv1994

Multidimensional Cosmology with Multicomponent Perfect Fluid and Toda Lattices

The integration procedure for multidimensional cosmological models with multicomponent perfect fluid in spaces of constant curvature is developed. Reduction of pseudo-Euclidean Toda-like systems to the Euclidean ones is done. Some known solutions are singled out from those obtained. The existence of the wormholes is proved.

gr-qc↗
arXiv1994

Multidimensional Classical and Quantum Wormholes in Models with Cosmological Constant

A multidimensional cosmological model with space-time consisting of $n (n \ge 2)$ Einstein spaces $M_{i}$ is investigated in the presence of a cosmological constant $Λ$ and a homogeneous minimally coupled scalar field $φ(t)$ as a matter source. Classical and quantum wormhole solutions are obtained for $Λ< 0$ and all $M_{i}$ being Ricci-flat. Classical wormhole solutions are also found for $Λ< 0$ and only one of the $M_{i}$ being Ricci-flat for the case of spontaneous compactification of the internal dimensions with fine tuning of parameters.

gr-qc↗