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f -biminimal maps between Riemannian manifolds

Yan ZhaoXimin Liu — 2019

Czechoslovak Mathematical Journal

We give the definition of f -biminimal submanifolds and derive the equation for f -biminimal submanifolds. As an application, we give some examples of f -biminimal manifolds. Finally, we consider f -minimal hypersurfaces in the product space n × 𝕊 1 ( a ) and derive two rigidity theorems.

Proper connection number of bipartite graphs

Jun YueMeiqin WeiYan Zhao — 2018

Czechoslovak Mathematical Journal

An edge-colored graph G is proper connected if every pair of vertices is connected by a proper path. The proper connection number of a connected graph G , denoted by pc ( G ) , is the smallest number of colors that are needed to color the edges of G in order to make it proper connected. In this paper, we obtain the sharp upper bound for pc ( G ) of a general bipartite graph G and a series of extremal graphs. Additionally, we give a proper 2 -coloring for a connected bipartite graph G having δ ( G ) 2 and a dominating cycle...

Graphs with 3-Rainbow Index n − 1 and n − 2

Xueliang LiIngo SchiermeyerKang YangYan Zhao — 2015

Discussiones Mathematicae Graph Theory

Let G = (V (G),E(G)) be a nontrivial connected graph of order n with an edge-coloring c : E(G) → {1, 2, . . . , q}, q ∈ N, where adjacent edges may be colored the same. A tree T in G is a rainbow tree if no two edges of T receive the same color. For a vertex set S ⊆ V (G), a tree connecting S in G is called an S-tree. The minimum number of colors that are needed in an edge-coloring of G such that there is a rainbow S-tree for each k-subset S of V (G) is called the k-rainbow index of G, denoted by...

Graphs with 4-Rainbow Index 3 and n − 1

Xueliang LiIngo SchiermeyerKang YangYan Zhao — 2015

Discussiones Mathematicae Graph Theory

Let G be a nontrivial connected graph with an edge-coloring c : E(G) → {1, 2, . . . , q}, q ∈ ℕ, where adjacent edges may be colored the same. A tree T in G is called a rainbow tree if no two edges of T receive the same color. For a vertex set S ⊆ V (G), a tree that connects S in G is called an S-tree. The minimum number of colors that are needed in an edge-coloring of G such that there is a rainbow S-tree for every set S of k vertices of V (G) is called the k-rainbow index of G, denoted by rxk(G)....

The 3-Rainbow Index of a Graph

Lily ChenXueliang LiKang YangYan Zhao — 2015

Discussiones Mathematicae Graph Theory

Let G be a nontrivial connected graph with an edge-coloring c : E(G) → {1, 2, . . . , q}, q ∈ ℕ, where adjacent edges may be colored the same. A tree T in G is a rainbow tree if no two edges of T receive the same color. For a vertex subset S ⊆ V (G), a tree that connects S in G is called an S-tree. The minimum number of colors that are needed in an edge-coloring of G such that there is a rainbow S-tree for each k-subset S of V (G) is called the k-rainbow index of G, denoted by rxk(G). In this paper,...

Some congruences for 3-component multipartitions

Tao Yan ZhaoLily J. JinC. Gu — 2016

Open Mathematics

Let p3(n) denote the number of 3-component multipartitions of n. Recently, using a 3-dissection formula for the generating function of p3(n), Baruah and Ojah proved that for n ≥ 0, p3(9n + 5) ≡ 0 (mod 33) and p3 (9n + 8) ≡ 0 (mod 34). In this paper, we prove several congruences modulo powers of 3 for p3(n) by using some theta function identities. For example, we prove that for n ≥ 0, p3 (243n + 233) ≡ p3 (729n + 638) ≡ 0 (mod 310).

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