共查询到10条相似文献,搜索用时 140 毫秒
1.
Let G be a graph. For u,vV(G) with distG(u,v)=2, denote JG(u,v)={wNG(u)∩NG(v)|NG(w)NG(u)NG(v){u,v}}. A graph G is called quasi claw-free if JG(u,v)≠ for any u,vV(G) with distG(u,v)=2. In 1986, Thomassen conjectured that every 4-connected line graph is hamiltonian. In this paper we show that every 4-connected line graph of a quasi claw-free graph is hamiltonian connected. 相似文献
2.
A poset P=(X,) is m-partite if X has a partition X=X1Xm such that (1) each Xi forms an antichain in P, and (2) xy implies xXi and yXj where i<j. In this article we derive a tight asymptotic upper bound on the order dimension of m-partite posets in terms of m and their bipartite sub-posets in a constructive and elementary way. 相似文献
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4.
Let d≥3. Let H be a d+1-dimensional vector space over GF(2) and {e0,…,ed} be a specified basis of H. We define Supp(t){et1,…,etl}, a subset of a specified base for a non-zero vector t=et1++etl of H, and Supp(0)0/. We also define J(t)Supp(t) if |Supp(t)| is odd, and J(t)Supp(t){0} if |Supp(t)| is even.For s,tH, let {a(s,t)} be elements of H(HH) which satisfy the following conditions: (1) a(s,s)=(0,0), (2) a(s,t)=a(t,s), (3) a(s,t)≠(0,0) if s≠t, (4) a(s,t)=a(s′,t′) if and only if {s,t}={s′,t′}, (5) {a(s,t)|tH} is a vector space over GF(2), (6) {a(s,t)|s,tH} generate H(HH). Then, it is known that S{X(s)|sH}, where X(s){a(s,t)|tH{s}}, is a dual hyperoval in PG(d(d+3)/2,2)=(H(HH)){(0,0)}.In this note, we assume that, for s,tH, there exists some xs,t in GF(2) such that a(s,t) satisfies the following equation: Then, we prove that the dual hyperoval constructed by {a(s,t)} is isomorphic to either the Huybrechts’ dual hyperoval, or the Buratti and Del Fra’s dual hyperoval. 相似文献
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The transformation graph G-+- of a graph G is the graph with vertex set V(G)E(G), in which two vertices u and v are joined by an edge if one of the following conditions holds: (i) u,vV(G) and they are not adjacent in G, (ii) u,vE(G) and they are adjacent in G, (iii) one of u and v is in V(G) while the other is in E(G), and they are not incident in G. In this paper, for any graph G, we determine the connectivity and the independence number of G-+-. Furthermore, for a graph G of order n4, we show that G-+- is hamiltonian if and only if G is not isomorphic to any graph in {2K1+K2,K1+K3}{K1,n-1,K1,n-1+e,K1,n-2+K1}. 相似文献
6.
Let D be a two-dimensional Noetherian domain, let R be an overring of D, and let Σ and Γ be collections of valuation overrings of D. We consider circumstances under which (VΣV)∩R=(WΓW)∩R implies that Σ=Γ. We show that if R is integrally closed, these representations are “strongly” irredundant, and every member of ΣΓ has Krull dimension 2, then Σ=Γ. If in addition Σ and Γ are Noetherian subspaces of the Zariski–Riemann space of the quotient field of D (e.g. if Σ and Γ have finite character), then the restriction that the members of ΣΓ have Krull dimension 2 can be omitted. An example shows that these results do not extend to overrings of three-dimensional Noetherian domains. 相似文献
7.
Let Lq (1q<∞) be the space of functions f measurable on I=[−1,1] and integrable to the power q, with normL∞ is the space of functions measurable on I with normWe denote by AC the set of all functions absolutely continuous on I. For nN, q[1,∞] we setWn,q={f:f(n−1)AC, f(n)Lq}.In this paper, we consider the problem of accuracy of constants A, B in the inequalities (1) || f(m)||qA|| f||p+B|| f(m+k+1)||r, mN, kW; p,q,r[1,∞], fWm+k+1,r. 相似文献
8.
We apply the techniques of monotone and relative rearrangements to the nonrearrangement invariant spaces Lp()(Ω) with variable exponent. In particular, we show that the maps uLp()(Ω)→k(t)u*Lp*()(0,measΩ) and uLp()(Ω)→u*Lp*()(0,measΩ) are locally -Hölderian (u* (resp. p*) is the decreasing (resp. increasing) rearrangement of u (resp. p)). The pointwise relations for the relative rearrangement are applied to derive the Sobolev embedding with eventually discontinuous exponents. 相似文献
9.
Andrs Kro 《Journal of Approximation Theory》2001,111(2):303
Let K be a convex body in
d (d2), and denote by Bn(K) the set of all polynomials pn in
d of total degree n such that |pn|1 on K. In this paper we consider the following question: does there exist a p*nBn(K) which majorates every element of Bn(K) outside of K? In other words can we find a minimal γ1 and p*nBn(K) so that |pn(x)|γ |p*n(x)| for every pnBn(K) and x
d\K? We discuss the magnitude of γ and construct the universal majorants p*n for evenn. It is shown that γ can be 1 only on ellipsoids. Moreover, γ=O(1) on polytopes and has at most polynomial growth with respect to n, in general, for every convex body K. 相似文献
10.
Andrs Bir 《Journal of Number Theory》2006,121(2):324-354
In [A. Biró, V.T. Sós, Strong characterizing sequences in simultaneous Diophantine approximation, J. Number Theory 99 (2003) 405–414] we proved that if Γ is a subgroup of the torus R/Z generated by finitely many independent irrationals, then there is an infinite subset AZ which characterizes Γ in the sense that for γR/Z we have ∑aAaγ<∞ if and only if γΓ. Here we consider a general compact metrizable Abelian group G instead of R/Z, and we characterize its finitely generated free subgroups Γ by subsets AG*, where G* is the Pontriagin dual of G. For this case we prove stronger forms of the analogue of the theorem of the above mentioned work, and we find necessary and sufficient conditions for a kind of strengthening of this statement to be true. 相似文献