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Vol 72, No 6 (2017)

Article

The length of minimal filling for a five-point metric space

Bednov B.B.

Abstract

The length of the minimal filling of an arbitrary five-point metric space is represented as a function of lengths between points from this metric space.

Moscow University Mathematics Bulletin. 2017;72(6):221-225
pages 221-225 views

The proof of simultaneous conditional stabilization and destabilization of linear Hamiltonian systems

Salova T.V.

Abstract

It is proved that each linear Hamiltonian system is simultaneously conditionally (with respect to a subspace of half dimension) stabilizable and destabilizable by infinitesimal Hamiltonian perturbation.

Moscow University Mathematics Bulletin. 2017;72(6):226-232
pages 226-232 views

Growth of codimensions of metabelian algebras

Zaicev M.V.

Abstract

Numerical invariants of identities of nonassociative algebras are considered. It is proved that the codimension sequence of any finitely generated metabelian algebra has an exponentially bounded codimension growth. It is shown that the upper PI-exponent increases at most by 1 after adjoining an external unit. It is proved that for two-step left-nilpotent algebras the lower PI-exponent increases at least by 1.

Moscow University Mathematics Bulletin. 2017;72(6):233-237
pages 233-237 views

Fast algorithm for geometrical coding of digital images

Nosovskii G.V., Chekunov A.Y., Podlipaev S.A.

Abstract

A fast algorithm for geometrical coding is presented in the paper. It allows one to perform the image analysis by methods of differential geometry rather than widespread methods based on gradient and Hessian calculations. Nowadays, one of the most important aspects in image analysis is the speed of computations. The algorithm for geometrical coding is comparable or faster than traditional algorithms of image analysis and in many cases it gives better results. Several examples of algorithm working results for contour detection are presented.

Moscow University Mathematics Bulletin. 2017;72(6):238-244
pages 238-244 views

Comparison of the system “Chaplygin ball with a rotor” and the Zhukovskii system from the rough Liouville equivalence point of view

Zhila A.I.

Abstract

A problem of symplectic geometry is considered, namely, topological analysis of a rolling dynamically balanced non-symmetric ball with a rotor on a rough horizontal plane is considered. The Liouville equivalence between this system and the Zhukovskii system is studied.

Moscow University Mathematics Bulletin. 2017;72(6):245-250
pages 245-250 views

Sturmian words and uncountable set of almost nilpotent varieties of quadratic growth

Mishchenko S.P., Panov N.P.

Abstract

An almost nilpotent variety of quadratic growth is constructed and studied in the paper for any infinite Sturmian word.

Moscow University Mathematics Bulletin. 2017;72(6):251-254
pages 251-254 views

A cubature formula for periodic functions

Chubarikov V.N., Sharapova M.L.

Abstract

New many-dimensional cubature formulas are obtained for periodic functions with the use of the Chinese remainder theorem. This allows us to take into account the “equality” of all variables and the “uniformness” of distribution of nodes in numerical integration formulas.

Moscow University Mathematics Bulletin. 2017;72(6):255-257
pages 255-257 views