394 research outputs found
Role of acid-base interactions in synthesis of cordierite from talc and sillimanite group minerals
It has been found that the mechanical activation of mixtures of sillimanite
group minerals with talc and silica additives in grinding-activating devices
with periodic and flow action provides significant acceleration of their
interaction with formation of cordierite at the subsequent high-temperature
treatment. It is shown that the output of cordierite depends on nature of
mineral: in mixture with a sillimanite it is considerably higher, than with
an andalusite and kyanite, while the rate of mullitization of these minerals
has opposite character. It means that the formation of mullite during heat
treatment is not a limiting step in synthesis of cordierite. It is shown that
the rate of reaction is determined by the difference in the acid-base
properties of these minerals, which depend on the coordination of aluminum
cations by oxygen ions, different for each of the modifications
Hamiltonian of Tensionless Strings with Tensor Central Charge Coordinates
A new class of twistor-like string models in four-dimensional space-time
extended by the addition of six tensorial central charge (TCC) coordinates
is studied. The Hamiltonian of tensionless string in the extended
space-time is derived and its symmetries are investigated. We establish that
the string constraints reduce the number of independent TCC coordinates
to one real effective coordinate which composes an effective
5-dimensional target space together with the coordinates. We construct
the P.B. algebra of the first class constraints and discover that it coincides
with the P.B. algebra of tensionless strings. The Lorentz covariant
antisymmetric Dirac -matrix of the P.B. of the second class
constraints is constructed and its algebraic structure is further presented.Comment: 18 pages, Latex, no figure
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In this section, we have published summaries of young scientists' works presented at a conference at Scientific Center for Children's Health in June 2007.В этом разделе опубликованы резюме работ молодых ученых, представленных на конференции в Научном центре здоровья детей РАМН в июне 2007 г
Polynomial Lie algebra methods in solving the second-harmonic generation model: some exact and approximate calculations
We compare exact and SU(2)-cluster approximate calculation schemes to
determine dynamics of the second-harmonic generation model using its
reformulation in terms of a polynomial Lie algebra and related
spectral representations of the model evolution operator realized in
algorithmic forms. It enabled us to implement computer experiments exhibiting a
satisfactory accuracy of the cluster approximations in a large range of
characteristic model parameters.Comment: LaTex file, 13 pages, 3 figure
Hamiltonian structure and noncommutativity in -brane models with exotic supersymmetry
The Hamiltonian of the simplest super -brane model preserving 3/4 of the
D=4 N=1 supersymmetry in the centrally extended symplectic superspace is
derived and its symmetries are described. The constraints of the model are
covariantly separated into the first- and the second-class sets and the Dirac
brackets (D.B.) are constructed. We show the D.B. noncommutativity of the super
-brane coordinates and find the D.B. realization of the
superalgebra. Established is the coincidence of the D.B. and Poisson bracket
realizations of the superalgebra on the constraint surface and the
absence there of anomaly terms in the commutation relations for the quantized
generators of the superalgebra.Comment: Latex, 27 pages, no figures. Latex packages amsfonts and euscript are
use
Extra Gauge Symmetry for Extra Supersymmetry
It is shown that the extra supersymmetry of tensionless superstring and super
-brane is accompanied by the presence of new bosonic gauge symmetries.
It permits to use composed coordinates encoding all physical degrees of
freedom of the model and invariant under these gauge symmetries and the
enhanced -symmetry.
It is proved that the composed gauge invariant coordinates coincide with the
componets of symplectic supertwistor realizing a linear representation of the
hidden OSp(1,2M) symmetry of the super -brane Lagrangian. A connection of
the presented gauge symmetries with massless higher spin gauge theories and a
symmetric phase of /string-theory is discussed.Comment: Latex, 10 pages; references and few comments added for section 1. To
appear in Phys. Lett.
Wess-Zumino actions and Dirichlet Boundary Conditions for Super p-branes with Exotic Fractions of Supersymmetry
The general solutions in the models of closed and open superstring and super
p-branes with exotic fractions of the N=1 supersymmetry are considered and the
spontaneously broken character of the symmetry of the models is
established. It is shown that extending these models by Wess-Zumino terms
generates the Dirichlet boundary conditions for superstring and super p-branes.
Using the generalized Wess-Zumino terms new invariant super p-brane
and Dp-brane-like actions preserving fraction of supersymmetry
are proposed. For M=32 these models suggest new superbrane vacua of M-theory
preserving 31 from 32 global supersymmetries.Comment: Latex, 13 page
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