We characterize obstruction sets in caterpillar dualities in terms of regular
languages, and give a construction of the dual of a regular family of
caterpillars. We show that these duals correspond to the constraint
satisfaction problems definable by a monadic linear Datalog program with at
most one EDB per rule.
This paper provides a short and transparent solution for the covering cost of
white-grey trees which play a crucial role in the algorithm of Bergeron {\it et
al.}\ to compute the rearrangement distance between two multichromosomal
genomes in linear time ({\it Theor. Comput. Sci.}, 410:5300-5316, 2009). In the
process it introduces a new {\em center} notion for trees, which seems to be
interesting on its own.
In this paper we consider a simple Markov chain for bipartite graphs with
given degree sequence on $n$ vertices. We show that the mixing time of this
Markov chain is bounded above by a polynomial in $n$ in case of {\em
semi-regular} degree sequence. The novelty of our approach lays in the
construction of the canonical paths in Sinclair's method.
Degree-based graph construction is an ubiquitous problem in network modeling,
ranging from social sciences to chemical compounds and biochemical reaction
networks in the cell. This problem includes existence, enumeration, exhaustive
construction and sampling questions with aspects that are still open today.
Here we give necessary and sufficient conditions for a sequence of nonnegative
integers to be realized as a simple graph's degree sequence, such that a given
(but otherwise arbitrary) set of connections from a arbitrarily given node are
avoided.