共查询到20条相似文献,搜索用时 15 毫秒
1.
Francesca Vetro 《manuscripta mathematica》2008,125(3):353-368
Let Y be a smooth, connected, projective complex curve. In this paper, we study the Hurwitz spaces which parameterize branched
coverings of Y whose monodromy group is a Weyl group of type D
d
and whose local monodromies are all reflections except one. We prove the irreducibility of these spaces when and successively we extend the result to curves of genus g ≥ 1. 相似文献
2.
Francesca Vetro 《Mediterranean Journal of Mathematics》2013,10(3):1151-1170
In this paper we prove new results of irreducibility for Hurwitz spaces of coverings whose monodromy group is a Weyl group of type B d and whose local monodromies are all reflections except two. 相似文献
3.
We prove some particular cases of the following conjecture of Perrin and Schützenberger, known as “the triangle conjecture.” Let A = {a, b} be a two-letter alphabet, d a positive integer and let Bd = {aibaj| 0 ? i + j ? d}. If X ? Bd is a code, then |X| ? d + 1. 相似文献
4.
《Journal of multivariate analysis》1987,23(1):67-76
A recursive kernel estimate ∑i = 1n YiK⧸(x − Xi)hi)⧸∑j = 1n K((x − Xj)⧸hj) of a regression m(x) = E{Y|X = x} calculated from independent observations (X1, Y1),…, (Xn, Yn) of a pair (X, Y) of random variables is examined. ForE|Y|1 + δ < ∞, δ > 0, the estimate is weakly pointwise consistent for almost all (μ) x ∈ Rd, μ is the probability measure of X, if and only if∑i−1n hid I{hi > ɛ } ⧸ ∑j = 1n hjd → 0 as n → ∞, all ɛ > 0, and∑i = 1∞ hid = ∞, d is the dimension of X. For E|Y|1 + δ < ∞, δ > 0, the estimate is strongly pointwise consistent for almost all (μ) x ∈ Rd, if and only if the same conditions hold. ForE|Y|1 + δ < ∞, δ > 0, weak and strong consistency are equivalent. Similar results are given for complete convergence. 相似文献
5.
G. Horváth 《Acta Mathematica Hungarica》2007,115(1-2):169-175
Let 0 ≦ a 1 < a 2 < ? be an infinite sequence of integers and let r 1(A, n) = |(i;j): a i + a j = n, i ≦ j|. We show that if d > 0 is an integer, then there does not exist n 0 such that d ≦ r 1 (A, n) ≦ d + [√2d + ½] for n > n 0. 相似文献
6.
Torleiv Kl?ve 《Designs, Codes and Cryptography》2011,59(1-3):183-191
Lower bounds on the number of permutations p of {1, 2, . . . , n} satisfying |p i ? i| ?? d for all i are given. 相似文献
7.
Michel Laurent 《Indagationes Mathematicae》2003,14(1):45-53
Let n be an integer ≥ 1 and let θ be a real number which is not an algebraic number of degree ≤ [n/2]. We show that there exist ? > 0 and arbitrary large real numbers X such that the system of linear inequalities |x0| ≤ X and |x0θj − xj| ≤ ?X−1/[n/2] for 1 < j < n, has only the zero solution in rational integers x0,…, xn. This result refines a similar statement due to H. Davenport and W. M. Schmidt, where the upper integer part [n/2] is replaced everywhere by the integer part [n/2]. As a corollary, we improve slightly the exponent of approximation to 0 by algebraic integers of degree n + 1 over Q obtained by these authors. 相似文献
8.
Removable singularity of the polyharmonic equation 总被引:1,自引:0,他引:1
Shu-Yu Hsu 《Nonlinear Analysis: Theory, Methods & Applications》2010,72(2):624-627
Let x0∈Ω⊂Rn, n≥2, be a domain and let m≥2. We will prove that a solution u of the polyharmonic equation Δmu=0 in Ω?{x0} has a removable singularity at x0 if and only if as |x−x0|→0 for n≥3 and as |x−x0|→0 for n=2. For m≥2 we will also prove that u has a removable singularity at x0 if |u(x)|=o(|x−x0|2m−n) as |x−x0|→0 for n≥3 and |u(x)|=o(|x−x0|2m−2log(|x−x0|−1)) as |x−x0|→0 for n=2. 相似文献
9.
10.
I.M. Chakravarti 《Linear algebra and its applications》1975,10(2):103-109
Let A denote an n×n matrix with all its elements real and non-negative, and let ri be the sum of the elements in the ith row of A, i=1,…,n. Let B=A?D(r1,…,rn), where D(r1,…,rn) is the diagonal matrix with ri at the position (i,i). Then it is proved that A is irreducible if and only if rank B=n?1 and the null space of BT contains a vector d whose entries are all non-null. 相似文献
11.
Jarmila Chvátalová 《Discrete Mathematics》1975,11(3):249-253
If G is a graph with p vertices and at least one edge, we set φ (G) = m n max |f(u) ? f(v)|, where the maximum is taken over all edges uv and the minimum over all one-to-one mappings f : V(G) → {1, 2, …, p}: V(G) denotes the set of vertices of G.Pn will denote a path of length n whose vertices are integers 1, 2, …, n with i adjacent to j if and only if |i ? j| = 1. Pm × Pn will denote a graph whose vertices are elements of {1, 2, …, m} × {1, 2, …, n} and in which (i, j), (r, s) are adjacent whenever either i = r and |j ? s| = 1 or j = s and |i ? r| = 1.Theorem.If max(m, n) ? 2, thenφ(Pm × Pn) = min(m, n). 相似文献
12.
Noga Alon 《Journal of Combinatorial Theory, Series A》1985,40(1):82-89
Let X1, …, Xn be n disjoint sets. For 1 ? i ? n and 1 ? j ? h let Aij and Bij be subsets of Xi that satisfy |Aij| ? ri and |Bij| ? si for 1 ? i ? n, 1 ? j ? h, for 1 ? j ? h, for 1 ? j < l ? h. We prove that . This result is best possible and has some interesting consequences. Its proof uses multilinear techniques (exterior algebra). 相似文献
13.
David J. Grynkiewicz Andreas Philipp Vadim Ponomarenko 《Israel Journal of Mathematics》2013,193(1):359-398
Let G be an abelian group, let s be a sequence of terms s 1, s 2, …, s n ∈ G not all contained in a coset of a proper subgroup of G, and let W be a sequence of n consecutive integers. Let $$W \odot S = \left\{ {w_1 s_1 + \cdots + w_n s_n :w_i a term of W,w_i \ne w_j for i \ne j} \right\},$$ which is a particular kind of weighted restricted sumset. We show that |W ⊙ S| ≥ min{|G| ? 1, n}, that W ⊙ S = G if n ≥ |G| + 1, and also characterize all sequences S of length |G| with W ⊙ S ≠ G. This result then allows us to characterize when a linear equation $$a_1 x_1 + \cdots + a_r x_r \equiv \alpha mod n,$$ where α, a 1, …, a r ∈ ? are given, has a solution (x 1, …, x r ) ∈ ? r modulo n with all x i distinct modulo n. As a second simple corollary, we also show that there are maximal length minimal zero-sum sequences over a rank 2 finite abelian group $G \cong C_{n_1 } \oplus C_{n_2 }$ (where n 1 |n 2 and n 2 ≥ 3) having k distinct terms, for any k ε [3, min{n 1 + 1, exp(G)}]. Indeed, apart from a few simple restrictions, any pattern of multiplicities is realizable for such a maximal length minimal zero-sum sequence. 相似文献
14.
Fan [G. Fan, Distribution of cycle lengths in graphs, J. Combin. Theory Ser. B 84 (2002) 187-202] proved that if G is a graph with minimum degree δ(G)≥3k for any positive integer k, then G contains k+1 cycles C0,C1,…,Ck such that k+1<|E(C0)|<|E(C1)|<?<|E(Ck)|, |E(Ci)−E(Ci−1)|=2, 1≤i≤k−1, and 1≤|E(Ck)|−|E(Ck−1)|≤2, and furthermore, if δ(G)≥3k+1, then |E(Ck)|−|E(Ck−1)|=2. In this paper, we generalize Fan’s result, and show that if we let G be a graph with minimum degree δ(G)≥3, for any positive integer k (if k≥2, then δ(G)≥4), if dG(u)+dG(v)≥6k−1 for every pair of adjacent vertices u,v∈V(G), then G contains k+1 cycles C0,C1,…,Ck such that k+1<|E(C0)|<|E(C1)|<?<|E(Ck)|, |E(Ci)−E(Ci−1)|=2, 1≤i≤k−1, and 1≤|E(Ck)|−|E(Ck−1)|≤2, and furthermore, if dG(u)+dG(v)≥6k+1, then |E(Ck)|−|E(Ck−1)|=2. 相似文献
15.
Michel Belliart 《Israel Journal of Mathematics》2018,224(1):315-342
Let L be a Lie group and let M be a compact manifold with dimension dim(L) + 1. Let Φ be a locally free action of L on M having class C r with r ≥ 2. Let R be the radical of L and let χ1, . . ., χ n be the characters of the adjoint action of {itR}. Finally, let Δ be the modular function of R. Under the assumption that none of the identities Δ×|χ i | = |χ j |α hold for any α ∈ [0, 1], one shows that Φ is the restriction to L of a locally free and transitive C r action of a larger Lie group. A second result is the existence of a unique Φ-invariant probability measure on {itM}; that measure is induced by a C r?1 nonsingular volume form. What makes that theorem all the more interesting is that certain of the Lie groups under consideration are not amenable. 相似文献
16.
Daniel Lustig 《Journal of Number Theory》2010,130(11):2628-2633
Let σj(n)=∑d|ndj be the sum of divisors function, and let I be the identity function. When considering only one input variable n, we show that the set of functions is algebraically independent. With two input variables, we give a non-trivial identity involving the sum of divisors function, prove its uniqueness, and use it to prove that any perfect number n must have the form n=rσ(r)/(2r−σ(r)), with some restrictions on r. This generalizes the known forms for both even and odd perfect numbers. 相似文献
17.
Ko-Wei Lih 《Journal of Combinatorial Theory, Series A》1980,29(2):182-185
Let |X| = n > 0, |Y| = k > 0, and Y ? X. A family A of subsets of X is a Sperner family of X over Y if A1A2 for every pair of distinct members of A and every member of A has a nonempty intersection with Y. The maximum cardinality f(n, k) of such a family is determined in this paper. . 相似文献
18.
Harris Kwong 《Discrete Mathematics》2008,308(23):5522-5532
Let G be a graph with vertex set V and edge set E, and let A be an abelian group. A labeling f:V→A induces an edge labeling f∗:E→A defined by f∗(xy)=f(x)+f(y). For i∈A, let vf(i)=card{v∈V:f(v)=i} and ef(i)=card{e∈E:f∗(e)=i}. A labeling f is said to be A-friendly if |vf(i)−vf(j)|≤1 for all (i,j)∈A×A, and A-cordial if we also have |ef(i)−ef(j)|≤1 for all (i,j)∈A×A. When A=Z2, the friendly index set of the graph G is defined as {|ef(1)−ef(0)|:the vertex labelingf is Z2-friendly}. In this paper we completely determine the friendly index sets of 2-regular graphs. In particular, we show that a 2-regular graph of order n is cordial if and only if n?2 (mod 4). 相似文献
19.
József Beck 《Journal of Combinatorial Theory, Series A》1981,30(2):117-133
Let {Ai} be a family of sets and let S = ∩iAi. By a positional game we shall mean a game played by two players on {Ai}. The players alternately pick elements of S and that player wins who fist has all the elements of one of the Ai. This paper deals with almost disjoint hypergraphs only, i.e., |Ai∪Aj| ? 1 if i ≠ j. Let be the smallest integer for which there is an almost disjoint n-uniform hypergraph , so that the first player has a winning strategy. It is shown that , which was conjectured by Erdös. The same method is applied to prove a conjecture of Hales and Jewett on r-dimensional tick-tack-toe if r is large enough. Finally we prove that for an arbitrary almost disjoint n-uniform hypergraph the second player has such a strategy that the first player unable to win in his mth move if m < (2 ? ?)n. 相似文献
20.
V. A. Zapol’skii 《Journal of Mathematical Sciences》2009,161(3):375-383
A cover of a manifold X is called an r-cover if any r points of X belong to a set in the cover. Let X and Y be two smooth manifolds, let Emb(X, Y) be the family of smooth embeddings X → Y, let M be an Abelian group, and let F: Emb(X, Y) → M be a functional. One says that the degree of F does not exceed r if for each finite open r-cover {U
i
}
i∈I
; of X there exist functionals F
i
: Emb(U
i
, Y) → M, i ∈ I, such that for each a ∈ Emb(X, Y) one has
F(a) = ?i ? I Fi( a| Ui ) F(a) = \sum\limits_{i \in I} {{F_i}\left( {a\left| {_{U_i}} \right.} \right)} 相似文献
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