4 papers · 1 filter
Homotopy classification of closed polygonal lines
E. Alkin, O. Nikitenko, A. Skopenkov
In this text we expose basic cases of some fundamental ideas and methods of topology. Namely, of homotopy, degree, fundamental group, covering, Whitehead invariant, etc. This is do…
The winding number of a closed curve around a point
E. Alkin, A. Miroshnikov, A. Skopenkov
In this expository note we present an elementary direct rigorous definition and the simplest properties of the winding number. This definition is simpler than the one given in some…
Cycles in graphs and in hypergraphs: towards homology theory
A. Miroshnikov, O. Nikitenko, A. Skopenkov
In this expository paper we present some ideas of algebraic topology (more precisely, of homology theory) in a language accessible to non-specialists in the area. A -cycle in a…
Low rank matrix completion and realization of graphs: results and problems
S. Dzhenzher, T. Garaev, O. Nikitenko +3
The Netflix problem (from machine learning) asks the following. Given a ratings matrix in which each entry represents the rating of movie by customer , if customer $…