Searcharxiv⌕ Search

arXiv subjects

V. N. Melnikov

Publications and source records attributed to V. N. Melnikov.

At least 19 recordsLinked to original sources
arXiv2014

On new definitions of SI base units. Why is the "atomic" kilogram preferable

We discuss the role of fundamental constants and measurement data for the Planck, Avogadro and Boltzmann constants and the elementary electric charge in connection with the planned transition to new definitions of four base SI units (the kilogram, mole, ampere and kelvin) in terms of fixed values of these constants. It is proposed to choose a new definition of any base SI unit in terms of a particular fundamental physical constant using a number of criteria, or principles, such as succession relative to the current SI, a sufficient stability of the new unit standards, and concordance between physical dimensions of the unit and the corresponding fundamental constant. It is argued that a redefinition of the kilogram and mole by fixing the values of the atomic mass unit and the Avogadro constant satisfies all these criteria and bears some more advantages against the version with fixed Planck constant: a well founded approach to definition of the ampere and the opportunity to preserve the current relationship between definitions of the mole and the kilogram. It is also argued that the kelvin can be redefined independently of the other three units.

physics.ins-det↗
arXiv2014

Quantum billiards in multidimensional models with fields of forms

Bianchi type I cosmological model in (n+1)-dimensional gravity with several forms is considered. When the electric non-composite brane ansatz is adopted, the Wheeler-DeWitt (WDW) equation for the model, written in a conformally covariant form, is analyzed. Under certain restrictions, asymptotic solutions to the WDW equation near the singularity are found, which reduce the problem to the so-called quantum billiard on the (n-1)-dimensional Lobachevsky space H^{n-1}. Two examples of quantum billiards are considered: a 2-dimensional quantum billiard for a 4D model with three 2-forms and a 9D quantum billiard for an 11D model with 120 4-forms which mimics SM2-brane sector of D=11 supergravity. For certain solutions, vanishing of the wave function at the singularity is proved.

gr-qc↗
arXiv2014

Quantum billiards in multidimensional models with branes

Gravitational D-dimensional model with l scalar fields and several forms is considered. When cosmological type diagonal metric is chosen, an electromagnetic composite brane ansatz is adopted and certain restrictions on the branes are imposed the conformally covariant Wheeler-DeWitt (WDW) equation for the model is studied. Under certain restrictions asymptotic solutions to WDW equation are found in the limit of the formation of the billiard walls which reduce the problem to the so-called quantum billiard on the (D+ l -2)-dimensional Lobachevsky space. Two examples of quantum billiards are considered. The first one deals with 9-dimensional quantum billiard for D = 11 model with 330 four-forms which mimic space-like M2- and M5-branes of D=11 supergravity. The second one deals with the 9-dimensional quantum billiard for D =10 gravitational model with one scalar field, 210 four-forms and 120 three-forms which mimic space-like D2-, D4-, FS1- and NS5-branes in D = 10 II A supergravity. It is shown that in both examples wave functions vanish in the limit of the formation of the billiard walls (i.e. we get a quantum resolution of the singularity for 11D model) but magnetic branes could not be neglected in calculations of quantum asymptotic solutions while they are irrelevant for classical oscillating behaviour when all 120 electric branes are present.

hep-th↗
arXiv2013

Nonlinear multidimensional gravity and the Australian dipole

The existing observational data on possible variations of fundamental physical constants (FPC) confirm more or less confidently only a variability of the fine structure constant $α$ in space and time. A model construction method is described, where variations of $α$ and other FPCs (including the gravitational constant $G$) follow from the dynamics of extra space-time dimensions in the framework of curvature-nonlinear multidimensional theories of gravity. An advantage of this method is a unified approach to variations of different FPCs. A particular model explaining the observable variations of $α$ in space and time has been constructed. It comprises a FRW cosmology with accelerated expansion, perturbed due to slightly inhomogeneous initial data.

gr-qc↗
arXiv2011

Black brane solutions related to non-singular Kac-Moody algebras

A multidimensional gravitational model containing scalar fields and antisymmetric forms is considered. The manifold is chosen in the form M = M_0 x M_1 x ... x M_n, where M_i are Einstein spaces (i > 0). The sigma-model approach and exact solutions with intersecting composite branes (e.g., solutions with harmonic functions and black brane ones) with intersection rules related to non-singular Kac-Moody (KM) algebras (e.g. hyperbolic ones) are considered. Some examples of black brane solutions are presented, e.g., those corresponding to hyperbolic KM algebras: H_2(q,q) (q > 2), HA_2^(1) = A_2^{++} and to the Lorentzian KM algebra P_{10}.

hep-th↗
arXiv2010

On black holes in multidimensional theory with Ricci-flat internal spaces

A generalization of the Tangherlini solution for the case of n internal Ricci-flat spaces is obtained. It is shown that in the (2+d)-dimensional section a horizon exists only in the trivial case when the internal-space factors are constant. The p-adic analog of the solution is also considered.

gr-qc↗
arXiv2009

On the "scattering law" for Kasner parameters in the model with one-component anisotropic fluid

A multidimensional cosmological type model with 1-component anisotropic fluid is considered. An exact solution is obtained. This solution is defined on a product manifold containing n Ricci-flat factor spaces. We singled out a special solution governed by the function cosh. It is shown that this special solution has Kasner-like asymptotics in the limits τ\to + 0 and τ\to + \infty, where τis a synchronous time variable. A relation between two sets of Kasner parameters α_{\infty} and α_{0} is found. This formula (of "scattering law") is coinciding with that obtained earlier for the S-brane solution (when scalar fields are absent).

gr-qc↗
arXiv2009

Models of G time variations in diverse dimensions

A review of different cosmological models in diverse dimensions leading to a relatively small time variation of the effective gravitational constant G is presented. Among them: 4-dimensional general scalar-tensor model, multidimensional vacuum model with two curved Einstein spaces, multidimensional model with multicomponent anisotropic "perfect fluid", S-brane model with scalar fields and two form field etc. It is shown that there exist different possible ways of explanation of relatively small time variation of the effective gravitational constant G compatible with present cosmological data (e.g. acceleration): 4-dimensional scalar-tensor theories or multidimensional cosmological models with different matter sources. The experimental bounds on G-dot may be satisfied ether in some restricted interval or for all allowed values of the synchronous time variable.

gr-qc↗
arXiv2009

Variations of constants as a test of gravity, cosmology and unified models

Gravitation as a fundamental interaction that governs all phenomena at large and very small scales, but still not well understood at a quantum level, is a cardinal missing link in unification of all physical interactions. Discovery of the present acceleration of the Universe, the dark matter and dark energy problems are also a great challenge to modern physics, which may lead to a new revolution in it. Integrable multidimensional models of gravitation and cosmology make up one of the proper approaches to studying basic issues and strong field objects, the early and present Universe and black hole (BH) physics in particular. Our main results within this approach are described for both cosmology and BH physics. Problems of the absolute G measurements and its possible time and range variations are reflections of the unification problem. The choice, nature, classification and precision of determination of the fundamental physical constants as well as their role in a transition, expected in 2011, to new definitions of the main SI units, supposed to be based on fundamental physical constants and stable quantum phenomena, are described. The problem of temporal variations of constants is also discussed, temporal and spatial variations of G in particular. A need for further absolute measurements of G, its possible range and time variations is pointed out. The multipurpose space project SEE is briefly described, aimed at measuring G and its stability in space and time, with precision 3-4 orders better than at present. It may answer many important questions posed by gravitation, cosmology and unified theories. A project of a laboratory experiment for testing possible deviations from the Newton law is also presented.

gr-qc↗
arXiv2009

P-brane black holes for general intersections

Black hole generalized p-brane solutions for a wide class of intersection rules are presented. The solutions are defined on a manifold that contains a product of n - 1 Ricci-flat internal spaces. They are defined up to moduli functions H_s = H_s(R) obeying a non-linear differential equations (equivalent to Toda-type equations) with certain boundary conditions imposed. Using conjecture on polynomial structure of H_s for intersections related to Lie algebras, new A_2-dyon solutions are obtained. Two examples of these A_2-dyon solutions, i.e. dyon in D = 11 supergravity with M2 and M5 branes intersecting at a point and dyon in Kaluza-Klein theory, are considered.

gr-qc↗
arXiv2009

Toda p-brane black holes and polynomials related to Lie algebras

Black hole generalized p-brane solutions for a wide class of intersection rules are obtained. The solutions are defined on a manifold that contains a product of n - 1 Ricci-flat internal spaces. They are defined up to a set of functions H_s obeying non-linear differential equations equivalent to Toda-type equations with certain boundary conditions imposed. A conjecture on polynomial structure of governing functions H_s for intersections related to semisimple Lie algebras is suggested. This conjecture is proved for Lie algebras: A_m, C_{m+1}, m > 0. For simple Lie algebras the powers of polynomials coincide with the components of twice the dual Weyl vector in the basis of simple coroots. The coefficients of polynomials depend upon the extremality parameter μ>0. In the extremal case μ= 0 such polynomials were considered previously by H. Lü, J. Maharana, S. Mukherji and C.N. Pope. Explicit formulas for A_2-solution are obtained. Two examples of A_2-dyon solutions, i.e. dyon in D = 11 supergravity with M2 and M5 branes intersecting at a point and Kaluza-Klein dyon, are considered.

math-ph↗
arXiv2008

Electric S-brane solutions corresponding to rank-2 Lie algebras: acceleration and small variation of G

Electric S-brane solutions with two non-composite electric branes and a set of l scalar fields are considered. The intersection rules for branes correspond to Lie algebras A_2, C_2 and G_2. The solutions contain five factor spaces. One of them, M_0, is interpreted as our 3-dimensional space. It is shown that there exists a time interval where accelerated expansion of our 3-dimensional space is compatible with a small enough variation of the effective gravitational constant G(τ). This interval contains τ_0, a point of minimum of the function G(τ). A special solution with two phantom scalar fields is analyzed and it is shown that in the vicinity of the point τ_0 the time variation of G(τ) (calculated in the linear approximation) decreases in the sequence of Lie algebras A_2, C_2 and G_2.

hep-th↗
arXiv2008

On billiard approach in multidimensional cosmological models

A short overview of the billiard approach for cosmological-type models with n Einstein factor-spaces is presented. We start with the billiard representation for pseudo-Euclidean Toda-like systems of cosmological origin. Then we consider cosmological model with multicomponent "perfect-fluid" and cosmological-type model with composite branes. The second one describes cosmological and spherically-symmetric configurations in a theory with scalar fields and fields of forms. The conditions for appearance of asymptotical Kasner-like and oscillating behaviors in the limit τ\to +0 and τ\to + \infty (where τis a "synchronous-type" variable) are formulated (e.g. in terms of inequalities on Kasner parameters). Examples of billiards related to the hyperbolic Kac-Moody algebras E_{10}, AE_3 and A_{1,II} are given.

hep-th↗
arXiv2008

Billiard representation for pseudo-Euclidean Toda-like systems of cosmological origin

The pseudo-Euclidean Toda-like system of cosmological origin 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 examples are considered.

math-ph↗
arXiv2008

Constants of extended Standard Model and search for their temporal variations

Some methods for the determination and the most precise values of constants of an extended Standard Model, which include the gravitation interaction and massive neutrinos, are presented. Accuracies of constants at different energy scales are compared and the possible manifestations of temporal variations of constants are considered. Theoretical estimations and obtained experimental bounds of variations are listed, that is important as for search of SM generalizations as to account for possible influence on metrological characteristics of measurement standards.

hep-ph↗
arXiv2008

On the "scattering law" for Kasner parameters appearing in asymptotics of an exact S-brane solution

A multidimensional cosmological model with scalar and form fields [1-4] is studied. An exact S-brane solution (either electric or magnetic) in a model with l scalar fields and one antisymmetric form of rank m > 1 is considered. This solution is defined on a product manifold containing n Ricci-flat factor spaces M_1, ..., M_n. In the case when the kinetic term for scalar fields is positive definite we singled out a special solution governed by the function cosh. It is shown that this special solution has Kasner-like asymptotics in the limits τ\to + 0 and τ\to + \infty, where τis a synchronous time variable. A relation between two sets of Kasner parameters α_{\infty} and α_0 is found. This relation, named as ``scattering law'' (SL) formula, is coinciding with the ``collision law'' (CL) formula obtained previously in [5] in a context of a billiard description of S-brane solutions near the singularity. A geometric sense of SL formula is clarified: it is shown that SL transformation is a map of a ``shadow'' part of the Kasner sphere S^{N-2} (N = n+l) onto ``illuminated'' part. This map is just a (generalized) inversion with respect to a point v located outside the Kasner sphere S^{N-2}. The shadow and illuminated parts of the Kasner sphere are defined with respect to a point-like source of light located at v. Explicit formulae for SL transformations corresponding to SM2- and SM5-brane solutions in 11-dimensional supergravity are presented.

hep-th↗
arXiv2008

Cosmologies from nonlinear multidimensional gravity with acceleration and slowly varying G

We consider multidimensional gravity with a Lagrangian containing the Ricci tensor squared and the Kretschmann invariant. In a Kaluza-Klein approach with a single compact extra space of arbitrary dimension, with the aid of a slow-change approximation (as compared with the Planck scale), we build a class of spatially flat cosmological models in which both the observed scale factor $a(τ)$ and the extra-dimensional one, $b(τ)$, grow exponentially at large times, but $b(τ)$ grows slowly enough to admit variations of the effective gravitational constant $G$ within observational limits. Such models predict a drastic change in the physical laws of our Universe in the remote future due to further growth of the extra dimensions.

gr-qc↗