DSpace Community: This is a special issue of the journal devoted to the jubilee of the outstanding Ukrainian and Russian mathematician, one of the founder of our journal Professor Rostislav Grigorchuk.This is a special issue of the journal devoted to the jubilee of the outstanding Ukrainian and Russian mathematician, one of the founder of our journal Professor Rostislav Grigorchuk.http://hdl.handle.net/123456789/412024-03-28T03:30:34Z2024-03-28T03:30:34ZOn faithful actions of groups and semigroups by orientation-preserving plane isometriesVorobets, Yaroslavhttp://hdl.handle.net/123456789/822020-01-24T21:24:52Z2003-01-01T00:00:00ZTitle: On faithful actions of groups and semigroups by orientation-preserving plane isometries
Authors: Vorobets, Yaroslav
Description: Feitful representations of two generated free
groups and free semigroups by orientation-preserving plane isometries
constructed.2003-01-01T00:00:00ZStructural properties of extremal asymmetric coloringsVerbitsky, Oleghttp://hdl.handle.net/123456789/812020-01-24T21:27:09Z2003-01-01T00:00:00ZTitle: Structural properties of extremal asymmetric colorings
Authors: Verbitsky, Oleg
Description: Let be a space with probability measure μ
for which the notion of symmetry is defined. Given A µ , let
ms(A) denote the supremum of μ(B) over symmetric B µ A. An
r-coloring of is a measurable map  : ! {1, . . . , r} possi-
bly undefined on a set of measure 0. Given an r-coloring Â, let
ms(; Â) = max1·i·r ms(Â−1(i)). With each space we associate
a Ramsey type number ms(, r) = infÂms(; Â). We call a col-
oring  congruent if the monochromatic classes Â−1(1), . . . , Â−1(r)
are pairwise congruent, i.e., can be mapped onto each other by a
symmetry of . We define ms?(, r) to be the infimum of ms(; Â)
over congruent Â.
We prove that ms(S1, r) = ms?(S1, r) for the unitary circle S1
endowed with standard symmetries of a plane, estimate ms?([0, 1), r)
for the unitary interval of reals considered with central symmetry,
and explore some other regularity properties of extremal colorings
for various spaces.2003-01-01T00:00:00ZDynamics of finite groups acting on the boundary of homogenous rooted treeSzaszkowski, Zbigniewhttp://hdl.handle.net/123456789/802020-01-24T21:25:28Z2003-01-01T00:00:00ZTitle: Dynamics of finite groups acting on the boundary of homogenous rooted tree
Authors: Szaszkowski, Zbigniew
Description: Criterion of embedding of finite groups into the
automorphism groups of a homogenous rooted tree of a spherical
index n is formulated. The sets of natural numbers which are the
lengths of all orbits of finite groups acting on the boundary of tree
are described.2003-01-01T00:00:00ZOn 2-state Mealy automata of polynomial growthReznykov, I. I.http://hdl.handle.net/123456789/792020-01-24T21:25:11Z2003-01-01T00:00:00ZTitle: On 2-state Mealy automata of polynomial growth
Authors: Reznykov, I. I.
Description: We consider the sequence of 2-state Mealy au-
tomata over the finite alphabets, that have polynomial growth or-
ders and define the infinitely presented automatic transformation
semigroups.2003-01-01T00:00:00Z