20 research outputs found
On 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 , where are Einstein spaces (). The sigma-model approach and exact solutions with intersecting composite
branes (e.g. solutions with harmonic functions, -brane and black brane ones)
with intersection rules related to non-singular Kac-Moody (KM) algebras (e.g.
hyperbolic ones) are reviewed. Some examples of solutions, e.g. corresponding
to hyperbolic KM algebras: , , , and
Lorentzian KM algebra are presented
Multitemporal generalization of Schwarzschild solution
The -time generalization of Schwarzschild solution is considered. The
equations of geodesics for the metric are integrated. The multitemporal
analogues of Newton laws for the extended objects described by the solution are
suggested. The scalar-vacuum generalization of the solution is also presented.Comment: 7 page
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.Comment: 27 pages, Late
Multitemporal generalization of the Tangherlini solution
The n-time generalization of the Tangherlini solution [1] is considered. The
equations of geodesics for the metric are integrated. For it is shown
that the naked singularity is absent only for two sets of parameters,
corresponding to the trivial extensions of the Tangherlini solution. The motion
of a relativistic particle in the multitemporal background is considered. This
motion is governed by the gravitational mass tensor. Some generalizations of
the solution, including the multitemporal analogue of the Myers-Perry charged
black hole solution, are obtained.Comment: 14 pages. RGA-CSVR-005/9
Cosmological solutions in multidimensional model with multiple exponential potential
A family of cosmological solutions with Ricci-flat spaces in the
theory with several scalar fields and multiple exponential potential is
obtained when coupling vectors in exponents obey certain relations. Two
subclasses of solutions with power-law and exponential behaviour of scale
factors are singled out. It is proved that power-law solutions may take place
only when coupling vectors are linearly independent and exponential dependence
occurs for linearly dependent set of coupling vectors. A subfamily of solutions
with accelerated expansion is singled out. A generalized isotropization
behaviours of certain classes of general solutions are found. In quantum case
exact solutions to Wheeler-DeWitt equation are obtained and special "ground
state" wave functions are considered.Comment: 22 pages, 1 figur
Reusable interorbital tugs of megawatt class: problems and prospects
The possibilities of creating solar reusable megawatt-class interorbital tugs are analyzing. A comparison of solar and nuclear power plants is given, and the advantages of using solar systems are justified. On the basis of a comparative analysis of analogues, such as solar sails, solar reflectors for illumination from Earth's orbit, solar panels of space power plants, the advantages of using frameless centrifugal solar panels in comparison with frame analogues are justified. It is indicated that the design and development, as well as the production and technological reserve and test base are sufficient for the creation of a solar power plant in the Russian Federation. The authors point out the prospect of using oxygen-hydrogen fuels obtained by electrolysis of water in space, which greatly increase the speed of transport operations, and the need to create electro-magnetic accelerators for launching from Earth with large cargo flows. The design evaluation of the parameters of centrifugal solar panels with a capacity of 1 and 5 MW is given. The necessary funding for the work was estimated
Space Project SEE for Measuring G and its Possible Spatial and Time Variations
La misión llamada SEE (Satellite Energy Exchange) fue designada para realizar mediciones extremadamente precisas sobre gravitación fundamental mediante la observación de la perturbación orbital a las órbitas contraidas de cuerpos orbitantes de pruebas en un medio gravitacional de femto-g hasta atto-g. La misión SEE usará la dinámica novedosa y original de cuerpos en prueba. La gravitación no está presente en las teorÃas de unificación. El objeto amplio de la misión SEE consiste en fortalecer el desarrollo de la teorÃa gravitatoria y la teorÃa de unificación llevando a cabo pruebas gravitacionales sensitivas capaces de discernir sobre la viabilidad de las diferentes teorÃas alternativas. La misión SEE introducirá y realizará nueva tegnologÃa para la creación de un medio cercano-zero, de control criogénico pasivo de temperatura, de capacidad pasiva de resguardo de estación, de medición de distancias sin contacto y de resolución sub-micrónica, todo lo cual promete tener aplicaciones en amplia variedad de naves espaciales