TY - JOUR

T1 - Packing without some pieces

AU - Yuster, R

N1 - Times Cited in Web of Science Core Collection: 0 Total Times Cited: 0 Cited Reference Count: 13

PY - 2019

Y1 - 2019

N2 - Erdos and Hanani proved that for every fixed integer k >= 2, the complete graph K-n can be almost completely packed with copies of K-k; that is, K-n contains pairwise edge-disjoint copies of K-k that cover all but an o(n) (1) fraction of its edges. Equivalently, elements of the set C(k) of all red-blue edge colorings of K-k can be used to almost completely pack every red-blue edge coloring of K-n. The following strengthening of the result of Erdos and Hanani is considered. Suppose C' subset of C(k). Is it true that we can use elements only from C' and almost completely pack every red-blue edge coloring of K-n ? An element C is an element of C(k) is avoidable if C' = C(k) \ C has this property and a subset F subset of C(k) is avoidable if C' = C(k) \ F has this property. It seems difficult to determine all avoidable graphs as well as all avoidable families. We prove some nontrivial sufficient conditions for avoidability. Our proofs imply, in particular, that (i) almost all elements of C(k) are avoidable (ii) all Eulerian elements of C(k) are avoidable and, in fact, the set of all Eulerian elements of C(k) is avoidable.

AB - Erdos and Hanani proved that for every fixed integer k >= 2, the complete graph K-n can be almost completely packed with copies of K-k; that is, K-n contains pairwise edge-disjoint copies of K-k that cover all but an o(n) (1) fraction of its edges. Equivalently, elements of the set C(k) of all red-blue edge colorings of K-k can be used to almost completely pack every red-blue edge coloring of K-n. The following strengthening of the result of Erdos and Hanani is considered. Suppose C' subset of C(k). Is it true that we can use elements only from C' and almost completely pack every red-blue edge coloring of K-n ? An element C is an element of C(k) is avoidable if C' = C(k) \ C has this property and a subset F subset of C(k) is avoidable if C' = C(k) \ F has this property. It seems difficult to determine all avoidable graphs as well as all avoidable families. We prove some nontrivial sufficient conditions for avoidability. Our proofs imply, in particular, that (i) almost all elements of C(k) are avoidable (ii) all Eulerian elements of C(k) are avoidable and, in fact, the set of all Eulerian elements of C(k) is avoidable.

KW - Packing

KW - avoidable graph

KW - edge-coloring

KW - INTEGER

U2 - https://doi.org/10.4310/JOC.2019.v10.n1.a1

DO - https://doi.org/10.4310/JOC.2019.v10.n1.a1

M3 - Article

SN - 2156-3527

VL - 10

SP - 1

EP - 25

JO - Journal of Combinatorics

JF - Journal of Combinatorics

IS - 1

ER -