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1.
LetA={a
1, …,a
k} and {b
1, …,b
k} be two subsets of an abelian groupG, k≤|G|. Snevily conjectured that, when |G| is odd, there is a numbering of the elements ofB such thata
i+b
i,1≤i≤k are pairwise distinct. By using a polynomial method, Alon affirmed this conjecture for |G| prime, even whenA is a sequence ofk<|G| elements. With a new application of the polynomial method, Dasgupta, Károlyi, Serra and Szegedy extended Alon’s result to
the groupsZ
p
r
andZ
p
rin the casek<p and verified Snevily’s conjecture for every cyclic group. In this paper, by employing group rings as a tool, we prove that
Alon’s result is true for any finite abelianp-group withk<√2p, and verify Snevily’s conjecture for every abelian group of odd order in the casek<√p, wherep is the smallest prime divisor of |G|.
This work has been supported partly by NSFC grant number 19971058 and 10271080. 相似文献
2.
Bodan Arsovski 《Israel Journal of Mathematics》2011,182(1):505-508
We prove Snevily’s conjecture, which states that for any positive integer k and any two k-element subsets {a
1, …, a
k
} and {b
1, …, b
k
} of a finite abelian group of odd order there exists a permutation π ∈ S
k
such that all sums a
i
+ b
π(i) (i ∈ [1, k]) are pairwise distinct. 相似文献
3.
Samit Dasgupta Gyula Károlyi Oriol Serra Balázs Szegedy 《Israel Journal of Mathematics》2001,126(1):17-28
LetA={a
1, …,a
k} andB={b
1, …,b
k} be two subsets of an Abelian groupG, k≤|G|. Snevily conjectured that, whenG is of odd order, there is a permutationπ ∈S
ksuch that the sums α
i
+b
i
, 1≤i≤k, are pairwise different. Alon showed that the conjecture is true for groups of prime order, even whenA is a sequence ofk<|G| elements, i.e., by allowing repeated elements inA. In this last sense the result does not hold for other Abelian groups. With a new kind of application of the polynomial method
in various finite and infinite fields we extend Alon’s result to the groups (ℤ
p
)
a
and
in the casek<p, and verify Snevily’s conjecture for every cyclic group of odd order.
Supported by Hungarian research grants OTKA F030822 and T029759.
Supported by the Catalan Research Council under grant 1998SGR00119.
Partially supported by the Hungarian Research Foundation (OTKA), grant no. T029132. 相似文献
4.
Haruhide Matsuda 《Graphs and Combinatorics》2002,18(4):763-768
Let a, b, m, and t be integers such that 1≤a<b and 1≤t≤⌉(b−m+1)/a⌉. Suppose that G is a graph of order |G| and H is any subgraph of G with the size |E(H)|=m. Then we prove that G has an [a,b]-factor containing all the edges of H if the minimum degree is at least a, |G|>((a+b)(t(a+b−1)−1)+2m)/b, and |N
G
(x
1)∪⋯ ∪N
G
(x
t
)|≥(a|G|+2m)/(a+b) for every independent set {x
1,…,x
t
}⊆V(G). This result is best possible in some sense and it is an extension of the result of H. Matsuda (A neighborhood condition
for graphs to have [a,b]-factors, Discrete Mathematics 224 (2000) 289–292).
Received: October, 2001 Final version received: September 17, 2002
RID="*"
ID="*" This research was partially supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Encouragement
of Young Scientists, 13740084, 2001 相似文献
5.
In this paper, we show that if G is a finite group with three supersolvable subgroups of pairwise relatively prime indices in G and G′ is nilpotent, then G is supersolvable. Let π(G) denote the set of prime divisors of |G| and max(π(G)) denote the largest prime divisor of |G|. We also establish that if G is a finite group such that G has three supersolvable subgroups H, K, and L whose indices in G are pairwise relatively prime,
q \nmid p-1{q \nmid p-1} where p = max(π(G)) and q = max(π(L)) with L a Hall p′-subgroup of G, then G is supersolvable. 相似文献
6.
OD-characterization of Almost Simple Groups Related to U3(5) 总被引:1,自引:0,他引:1
Let G be a finite group with order |G|=p1^α1p2^α2……pk^αk, where p1 〈 p2 〈……〈 Pk are prime numbers. One of the well-known simple graphs associated with G is the prime graph (or Gruenberg- Kegel graph) denoted .by г(G) (or GK(G)). This graph is constructed as follows: The vertex set of it is π(G) = {p1,p2,…,pk} and two vertices pi, pj with i≠j are adjacent by an edge (and we write pi - pj) if and only if G contains an element of order pipj. The degree deg(pi) of a vertex pj ∈π(G) is the number of edges incident on pi. We define D(G) := (deg(p1), deg(p2),..., deg(pk)), which is called the degree pattern of G. A group G is called k-fold OD-characterizable if there exist exactly k non- isomorphic groups H such that |H| = |G| and D(H) = D(G). Moreover, a 1-fold OD-characterizable group is simply called OD-characterizable. Let L := U3(5) be the projective special unitary group. In this paper, we classify groups with the same order and degree pattern as an almost simple group related to L. In fact, we obtain that L and L.2 are OD-characterizable; L.3 is 3-fold OD-characterizable; L.S3 is 6-fold OD-characterizable. 相似文献
7.
Noga Alon 《Israel Journal of Mathematics》2000,117(1):125-130
We prove that for every odd primep, everyk≤p
and every two subsets
A={a
1, …,a
k
} andB={b
1, …,b
k
} of cardinalityk each ofZ
p
, there is a permutationπ ∈S
k
such that the sumsa
i
+b
π(i) (inZ
p
) are pairwise distinct. This partially settles a question of Snevily. The proof is algebraic, and implies several related
results as well.
Research supported in part by a State of New Jersey grant and by the Hermann Minkowski Minerva Center for Geometry at Tel
Aviv University. 相似文献
8.
Let G be a finite group, and write cd(G) for the set of degrees of irreducible characters of G. We say G satisfies the one-prime hypothesis if whenever a and b are distinct degrees in cd(G), then the greatest common divisor of a and b is either 1 or a prime. We show that if G is a solvable group satisfying the one-prime hypothesis, then |cd(G)|≤9. We also construct a solvable group G satisfying the one-prime hypothesis with |cd(G)|=9 which shows that the bound found in this paper is the best possible bound.
Presented by D. Passman
Mathematics Subject Classification (2000) 20C15. 相似文献
9.
Hongdi Huang 《代数通讯》2013,41(2):568-590
A group G is said to be a B(n, k) group if for any n-element subset A of G, |A2| ≤k. In this paper, a characterization of B(5, 18) groups is given. It is shown that G is a B(5, 18) group if and only if one of the following statements holds: (1) G is abelian; (2) |G| ≤18; (3) G ? ? a, b | a5 = b4 = 1, ab = a?1 ?. 相似文献
10.
A variant of Davenport’s constant 总被引:1,自引:1,他引:0
R. Thangadurai 《Proceedings Mathematical Sciences》2007,117(2):147-158
Let p be a prime number. Let G be a finite abelian p-group of exponent n (written additively) and A be a non-empty subset of ]n[≔ {1, 2,…, n} such that elements of A are incongruent modulo p and non-zero modulo p. Let k ≥ D(G/|A| be any integer where D(G) denotes the well-known Davenport’s constant. In this article, we prove that for any sequence g
1, g
2,…, g
k
(not necessarily distinct) in G, one can always extract a subsequence with 1 ≤ ℓ ≤ k such that
where a
j
∈ A for all j. We provide examples where this bound cannot be improved. Furthermore, for the cyclic groups, we prove some sharp results
in this direction. In the last section, we explore the relation between this problem and a similar problem with prescribed
length. The proof of Theorem 1 uses group-algebra techniques, while for the other theorems, we use elementary number theory
techniques. 相似文献
11.
Bill Jackson 《Journal of Combinatorial Theory, Series B》1981,30(3):332-342
For k an integer, let G(a, b, k) denote a simple bipartite graph with bipartition (A, B) where |A| = a ≥ 2, |B| = b ≥ k ≥ 2, and each vertex of A has degree at least k. We prove two results concerning the existence of cycles in G(a, b, k). 相似文献
12.
LetA, B, S be finite subsets of an abelian groupG. Suppose that the restricted sumsetC={α+b: α ∈A, b ∈B, and α − b ∉S} is nonempty and somec∈C can be written asa+b witha∈A andb∈B in at mostm ways. We show that ifG is torsion-free or elementary abelian, then |C|≥|A|+|B|−|S|−m. We also prove that |C|≥|A|+|B|−2|S|−m if the torsion subgroup ofG is cyclic. In the caseS={0} this provides an advance on a conjecture of Lev.
This author is responsible for communications, and supported by the National Science Fund for Distinguished Young Scholars
(No. 10425103) and the Key Program of NSF (No. 10331020) in China. 相似文献
13.
Sheng Yang 《Archiv der Mathematik》2011,96(5):401-408
Let G be a finite group, and let B be a p-block of G with defect group D. Let k
0(B) denote the number of ordinary irreducible characters of height 0 in B. In 1984 Olsson proposed a conjecture:
k0(B)\leqq |D:D¢|{k_{0}(B)\leqq |D:D'|}. In this paper, we will verify Olsson’s conjecture in the case that D is metacyclic and p is odd. 相似文献
14.
Let G be a finite group and π(G) be the set of all prime divisors of its order. The prime graph GK(G) of G is a simple graph with vertex set π(G), and two distinct primes p, q ∈ π(G) are adjacent by an edge if and only if G has an element of order pq. For a vertex p ∈ π(G), the degree of p is denoted by deg(p) and as usual is the number of distinct vertices joined to p. If π(G) = {p
1, p
2,...,p
k
}, where p
1 < p
2 < ... < p
k
, then the degree pattern of G is defined by D(G) = (deg(p
1), deg(p
2),...,deg(p
k
)). The group G is called k-fold OD-characterizable if there exist exactly k non-isomorphic groups H satisfying conditions |H| = |G| and D(H) = D(G). In addition, a 1-fold OD-characterizable group is simply called OD-characterizable. In the present article, we show that
the alternating group A
22 is OD-characterizable. We also show that the automorphism groups of the alternating groups A
16 and A
22, i.e., the symmetric groups S
16 and S
22 are 3-fold OD-characterizable. It is worth mentioning that the prime graph associated to all these groups are connected. 相似文献
15.
A variation in the classical Turan extrernal problem is studied. A simple graphG of ordern is said to have propertyPk if it contains a clique of sizek+1 as its subgraph. Ann-term nonincreasing nonnegative integer sequence π=(d1, d2,⋯, d2) is said to be graphic if it is the degree sequence of a simple graphG of ordern and such a graphG is referred to as a realization of π. A graphic sequence π is said to be potentiallyP
k-graphic if it has a realizationG having propertyP
k
. The problem: determine the smallest positive even number σ(k, n) such that everyn-term graphic sequence π=(d1, d2,…, d2) without zero terms and with degree sum σ(π)=(d
1+d
2+ …+d
2) at least σ(k,n) is potentially Pk-graphic has been proved positive.
Project supported by the National Natural Science Foundation of China (Grant No. 19671077) and the Doctoral Program Foundation
of National Education Department of China. 相似文献
16.
Lingli Wang 《Frontiers of Mathematics in China》2010,5(1):179-190
Let G be a finite group, and let π
e
(G) be the spectrum of G, that is, the set of all element orders of G. In 1987, Shi Wujie put forward the following conjecture. If G is a finite group and M is a non-abelian simple group, then G ≅ M if and only if |G| = |M| and π
e
(G) = π
e
(M). In this short paper, we prove that if G is a finite group, then G ≅ M if and only if |G| = |M| and π
e
(G) = π
e
(M), where M = D
n
(2) and n is even. 相似文献
17.
Victor Guba 《代数通讯》2013,41(5):1988-1997
Let G be a group generated by a finite set A. An element g ∈ G is a strict dead end of depth k (with respect to A) if |g|>|ga 1|>|ga 1 a 2|>···>|ga 1 a 2… a k | for any a 1, a 2,…, a k ∈ A ±1 such that the word a 1 a 2… a k is freely irreducible. (Here |g| is the distance from g to the identity in the Cayley graph of G.) We show that in finitely generated free soluble groups of degree d ≥ 2 there exist strict dead elements of depth k = k(d), which grows exponentially with respect to d. 相似文献
18.
A tree is called a k-tree if the maximum degree is at most k. We prove the following theorem, by which a closure concept for spanning k-trees of n-connected graphs can be defined. Let k ≥ 2 and n ≥ 1 be integers, and let u and v be a pair of nonadjacent vertices of an n-connected graph G such that deg
G
(u) + deg
G
(v) ≥ |G| − 1 − (k − 2)n, where |G| denotes the order of G. Then G has a spanning k-tree if and only if G + uv has a spanning k-tree. 相似文献
19.
Bill Jackson 《Combinatorica》2010,30(1):69-81
Let G be a graph without loops or bridges and a, b be positive real numbers with b ≥ a(a+2). We show that the Tutte polynomial of G satisfies the inequality T
G
(b, 0)T
G
(0, b) ≥ T
G
(a, a)2. Our result was inspired by a conjecture of Merino and Welsh that T
G
(1, 1) ≤ max{T
G
(2, 0),T
G
(0, 2)}. 相似文献
20.
Wenguang Zhai 《数学学报(英文版)》2000,16(4):549-554
Let t(G) be the number of unitary factors of finite abelian group G. In this paper we prove T(x)=∑
|G|≤x
t(G) = main terms for any exponent pair (κ1/2 + 2κ), which improves on the exponent 9/25 obtained by Xiaodong Cao and the author.
Received December 8, 1998, Revised April 27, 1998, Accepted June 12, 1998 相似文献