We revoke the problem of drawing graphs in the plane so that only certain specified pairs of edges are allowed to cross. We overview some previous results and open problems, namely the connection to intersection graphs of curves in the plane. We complement these by stating a new conjecture and showing that its proof would solve the problem of algorithmic decidability of recognition of string gr...

In this paper, we construct a new topological quantum field theory of cohomological type and show that its partition function is a crossing number.

Hurewicz found connections between some topological notions and the combinatorial cardinals b and d. Rec law gave topological meaning to the definition of the cardinal p. We extend the picture with a topological interpretation of the cardinal t. We compare our notion to the one related to p, and to some other classical notions. This sheds new light on the famous open problem whether p = t.

T opological fluid dynamics is a young mathematical discipline that studies topological features of flows with complicated trajectories and their applications to fluid motions, and develops group-theoretic and geometric points of view on various problems of hydrodynamical origin. It is situated at a crossroads of several disciplines, including Lie groups, knot theory, partial differential equat...

This paper investigates the maximum genus and upper embeddability of connected 4-regular graphs. We obtain lower bounds on the maximum genus of connected 4-regular simple graphs and connected 4-regular graphs without loops in terms of the Betti number. The definition of the Betti number is referred to [Gross and Tucker, Topological Graph Theory, New York, 1987]. Furthermore, we give examples th...

We present recent results in unquenched lattice QCD with two degenerate light sea quarks using the truncated determinant approximation (TDA). In the TDA the infrared modes contributing to the quark determinant are computed exactly up to some cutoff in quark off-shellness (typically 2ΛQCD). This approach allows simulations to be performed at much lighter quark masses than possible with conventio...