6 research outputs found
Gallai's path decomposition conjecture for cartesian product of graphs (\uppercase\expandafter{\romannumeral 2})
Let be a graph of order . A path decomposition of is
a collection of edge-disjoint paths that covers all the edges of . Let
denote the minimum number of paths needed in a path decomposition of
. Gallai conjectured that if is connected, then . In this paper, we prove that Gallai's path
decomposition conjecture holds for the cartesian product , where
is any graph and is a unicyclic graph or a bicyclic graph.Comment: 26 pages, 2 figures. arXiv admin note: text overlap with
arXiv:2310.1118
Path and cycle decompositions of dense graphs
We make progress on three long standing conjectures from the 1960s about path
and cycle decompositions of graphs. Gallai conjectured that any connected graph
on vertices can be decomposed into at most paths, while a conjecture of Haj\'{o}s states that any
Eulerian graph on vertices can be decomposed into at most cycles. The Erd\H{o}s-Gallai conjecture states that
any graph on vertices can be decomposed into cycles and edges.
We show that if is a sufficiently large graph on vertices with linear
minimum degree, then the following hold.
(i) can be decomposed into at most paths.
(ii) If is Eulerian, then it can be decomposed into at most
cycles.
(iii) can be decomposed into at most cycles and
edges.
If in addition satisfies a weak expansion property, we asymptotically
determine the required number of paths/cycles for each such .
(iv) can be decomposed into paths, where
is the number of odd-degree vertices of .
(v) If is Eulerian, then it can be decomposed into
cycles.
All bounds in (i)-(v) are asymptotically best possible.Comment: 48 pages, 2 figures; final version, to appear in the Journal of the
London Mathematical Societ
On path-cycle decompositions of triangle-free graphs
In this work, we study conditions for the existence of length-constrainedpath-cycle decompositions, that is, partitions of the edge set of a graph intopaths and cycles of a given minimum length. Our main contribution is thecharacterization of the class of all triangle-free graphs with odd distance atleast that admit a path-cycle decomposition with elements of length atleast . As a consequence, it follows that Gallai's conjecture on pathdecomposition holds in a broad class of sparse graphs
On path-cycle decompositions of triangle-free graphs
In this work, we study conditions for the existence of length-constrained
path-cycle decompositions, that is, partitions of the edge set of a graph into
paths and cycles of a given minimum length. Our main contribution is the
characterization of the class of all triangle-free graphs with odd distance at
least that admit a path-cycle decomposition with elements of length at
least . As a consequence, it follows that Gallai's conjecture on path
decomposition holds in a broad class of sparse graphs