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Graphs and combinatorics, 2022-10, Vol.38 (5), Article 134
Ort / Verlag
Tokyo: Springer Japan
Erscheinungsjahr
2022
Quelle
SpringerLINK Journals
Beschreibungen/Notizen
We consider
twisted graphs
, that is, topological graphs that are weakly isomorphic to subgraphs of the complete twisted graph
T
n
.
We determine the exact minimum number of crossings of edges among the set of twisted graphs with
n
vertices and
m
edges; state a version of the crossing lemma for twisted graphs and conclude that the mid-range crossing constant for twisted graphs is 1/6. Let
e
k
(
n
)
be the maximum number of edges over all twisted graphs with
n
vertices and local crossing number at most
k
. We give lower and upper bounds for
e
k
(
n
)
and settle its exact value for
k
∈
{
0
,
1
,
2
,
3
,
6
,
10
}
.
We conjecture that for every
t
≥
1
,
e
(
t
2
)
(
n
)
=
(
t
+
1
)
n
-
t
+
2
2
,
n
≥
t
+
1
.