A Degree Condition Implying Ore-Type Condition for Even [2,b]-Factors in Graphs

• Autorzy: Shoichi Tsuchiya , Takamasa Yashima
• Języki publikacji: EN

Abstrakty

EN

For a graph G and even integers b ⩾ a ⩾ 2, a spanning subgraph F of G such that a ⩽ degF (x) ⩽ b and degF (x) is even for all x ∈ V (F) is called an even [a, b]-factor of G. In this paper, we show that a 2-edge-connected graph G of order n has an even [2, b]-factor if [...] max {degG (x),degG (y)}⩾max {2n2+b,3} $\max \{ \deg _G (x),\deg _G (y)\} \ge \max \left\{ {{{2n} \over {2 + b}},3} \right\}$ for any nonadjacent vertices x and y of G. Moreover, we show that for b ⩾ 3a and a > 2, there exists an infinite family of 2-edge-connected graphs G of order n with δ(G) ⩾ a such that G satisfies the condition [...] degG (x)+degG (y)>2ana+b $\deg _G (x) + \deg _G (y) > {{2an} \over {a + b}}$ for any nonadjacent vertices x and y of G, but has no even [a, b]-factors. In particular, the infinite family of graphs gives a counterexample to the conjecture of Matsuda on the existence of an even [a, b]-factor.

Słowa kluczowe

EN

[a,b]-factor; even factor; 2-edge-connected; minimum degree

Kategorie tematyczne

• 05C70: Factorization, matching, partitioning, covering and packing

• Wydawca: De Gruyter Open
• Czasopismo: Discussiones Mathematicae Graph Theory
• Rocznik: 2017
• Tom: 37
• Numer: 3
• Strony: 797-809

Daty

wydano

2017-08-01

otrzymano

2016-02-01

poprawiono

2016-06-17

zaakceptowano

2016-07-15

online

2017-07-06

Twórcy

autor

Shoichi Tsuchiya

• , , 2-1-1 Higashimita, Tama-ku, Kawasaki-shi, ,

autor

Takamasa Yashima

• , , 1-3 Kagurazaka, Shinjuku-ku, ,

Identyfikatory

DOI

10.7151/dmgt.1964