37 research outputs found
Enclosings of Decompositions of Complete Multigraphs in -Edge-Connected -Factorizations
A decomposition of a multigraph is a partition of its edges into
subgraphs . It is called an -factorization if every
is -regular and spanning. If is a subgraph of , a
decomposition of is said to be enclosed in a decomposition of if, for
every , is a subgraph of .
Feghali and Johnson gave necessary and sufficient conditions for a given
decomposition of to be enclosed in some -edge-connected
-factorization of for some range of values for the parameters
, , , , : , and either ,
or and and , or and . We generalize
their result to every and . We also give some
sufficient conditions for enclosing a given decomposition of in
some -edge-connected -factorization of for every
and , where is a constant that depends only on ,
and~.Comment: 17 pages; fixed the proof of Theorem 1.4 and other minor change
Gauge theory and Rasmussen's invariant
A previous paper of the authors' contained an error in the proof of a key
claim, that Rasmussen's knot-invariant s(K) is equal to its gauge-theory
counterpart. The original paper is included here together with a corrigendum,
indicating which parts still stand and which do not. In particular, the
gauge-theory counterpart of s(K) is not additive for connected sums.Comment: This version bundles the original submission with a 1-page
corrigendum, indicating the error. The new version of the corrigendum points
out that the invariant is not additive for connected sums. 23 pages, 3
figure
A survey on constructive methods for the Oberwolfach problem and its variants
The generalized Oberwolfach problem asks for a decomposition of a graph
into specified 2-regular spanning subgraphs , called factors.
The classic Oberwolfach problem corresponds to the case when all of the factors
are pairwise isomorphic, and is the complete graph of odd order or the
complete graph of even order with the edges of a -factor removed. When there
are two possible factor types, it is called the Hamilton-Waterloo problem.
In this paper we present a survey of constructive methods which have allowed
recent progress in this area. Specifically, we consider blow-up type
constructions, particularly as applied to the case when each factor consists of
cycles of the same length. We consider the case when the factors are all
bipartite (and hence consist of even cycles) and a method for using circulant
graphs to find solutions. We also consider constructions which yield solutions
with well-behaved automorphisms.Comment: To be published in the Fields Institute Communications book series.
23 pages, 2 figure