Representations of split graphs, their complements, stars, and hypercubes.
Let be the complex vector space of homogeneous linear polynomials in the variables . Suppose is a subgroup of , and is an irreducible character of . Let be the symmetry class of polynomials of degree with respect to and . For any linear operator acting on , there is a (unique) induced operator acting on symmetrized decomposable polynomials by In this paper, we show that the representation of the general linear group is equivalent to the direct sum of copies of a representation...
Máme-li neomezené množství mincí o předepsaných hodnotách, může se stát, že pomocí nich nelze složit některé částky. Pro jednoduchost se omezíme na případ, kdy máme k dispozici mince pouze dvou různých hodnot. V takovém případě je totiž možné poměrně snadno odvodit vzorce pro největší nereprezentovatelnou částku a zjistit počet všech takových částek. Ukážeme, jak lze ke stejnému cíli dospět různými postupy: nejprve odvodíme vzorec pro zjištění počtu všech nereprezentovatelných částek za pomoci rovinné...
For each integer and each finite graph , we construct a Coxeter group and a non positively curved polygonal complex on which acts properly cocompactly, such that each polygon of has edges, and the link of each vertex of is isomorphic to . If is a “generalized -gon”, then is a Tits building modelled on a reflection group of the hyperbolic plane. We give a condition on for to be non enumerable (which is satisfied if is a thick classical generalized -gon). On the other hand,...
For an ordered set of vertices and a vertex in a connected graph , the (metric) representation of with respect to is the -vector , where represents the distance between the vertices and . The set is a resolving set for if distinct vertices of have distinct representations with respect to . A resolving set of minimum cardinality is called a minimum resolving set or a basis and the cardinality of a basis for is its dimension . A set of vertices in is a dominating set...
A directed Cayley graph is specified by a group and an identity-free generating set for this group. Vertices of are elements of and there is a directed edge from the vertex to the vertex in if and only if there is a generator such that . We study graphs for the direct product of two cyclic groups and , and the generating set . We present resolving sets which yield upper bounds on the metric dimension of these graphs for and .
We analyse the spectral phase diagram of Schrödinger operators on regular tree graphs, with the graph adjacency operator and a random potential given by random variables. The main result is a criterion for the emergence of absolutely continuous spectrum due to fluctuation-enabled resonances between distant sites. Using it we prove that for unbounded random potentials spectrum appears at arbitrarily weak disorder in an energy regime which extends beyond the spectrum of. Incorporating...