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6 votes
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What is the smallest number of vertices in a graph whose every orientation contains a directed straight path of length 3

For a graph $\Gamma$ and a digraph $\vec H$ we write $\Gamma\Rightarrow \vec H$ if any orientation of $\Gamma$ contains an isometric and isomorphic copy of the digraph $\vec H$. Since each graph ...
Taras Banakh's user avatar
4 votes
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113 views

What properties do graphs avoiding large regular subgraphs have?

Fix a positive integer $r$ and real $\delta \in (0,1)$. Let $G$ be an undirected graph on $n$ vertices. Suppose that $G$ does not contain an $r$-regular subgraph on at least $\delta n$ vertices (i.e., ...
Naysh's user avatar
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2 votes
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134 views

Even cycle constrained edge coloring

Is minimum colors needed to assign colors to edges of complete graph $K_n$ so that every $2t$ simple cycle where $t\in\Big\{1,\dots,2\Big\lfloor\frac{n}2\Big\rfloor\Big\}$ contains atleast $t+1$ ...
Turbo's user avatar
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A Non-trivial intersecting set system problem

Liven large enough $k\in\Bbb N$ fix $m\in\{2,3,\dots,k\}$ and fix $4k$ cardinality set $K_{4k}$. What is the maximum $n\in\Bbb N$ such that at some $t\geq2n-1$ there are $$\mbox{ subsets }L_1,L_2,\...
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