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Hadwiger conjectured in 1943 that for every integer $t ge 1$, every graph with no $K_t$ minor is $(t-1)$-colorable. Kostochka, and independently Thomason, proved every graph with no $K_t$ minor is $O(t(log t)^{1/2})$-colorable. Recently, Postle improved it to $O(t (log log t)^6)$-colorable. In this paper, we show that every graph with no $K_t$ minor is $O(t (log log t)^{5})$-colorable.
We prove that for any $varepsilon>0$, for any large enough $t$, there is a graph $G$ that admits no $K_t$-minor but admits a $(frac32-varepsilon)t$-colouring that is frozen with respect to Kempe changes, i.e. any two colour classes induce a connected
Hadwigers conjecture is one of the most important and long-standing conjectures in graph theory. Reed and Seymour showed in 2004 that Hadwigers conjecture is true for line graphs. We investigate this conjecture on the closely related class of total g
In 1967, Grunbaum conjectured that any $d$-dimensional polytope with $d+sleq 2d$ vertices has at least [phi_k(d+s,d) = {d+1 choose k+1 }+{d choose k+1 }-{d+1-s choose k+1 } ] $k$-faces. We prove this conjecture and also characterize the cases in which equality holds.
A central problem in discrete geometry, known as Hadwigers covering problem, asks what the smallest natural number $Nleft(nright)$ is such that every convex body in ${mathbb R}^{n}$ can be covered by a union of the interiors of at most $Nleft(nright)
We consider the problem of characterising the generic rigidity of bar-joint frameworks in $mathbb{R}^d$ in which each vertex is constrained to lie in a given affine subspace. The special case when $d=2$ was previously solved by I. Streinu and L. Ther