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1.
We consider a variation of a classical Turán-type extremal problem as follows: Determine the smallest even integer σ(Kr,r,n) such that every n-term graphic sequence π = (d1,d2,...,dn) with term sum σ(π) = d1 + d2 + ... + dn ≥ σ(Kr,r,n) is potentially Kr,r-graphic, where Kr,r is an r × r complete bipartite graph, i.e. π has a realization G containing Kr,r as its subgraph. In this paper, the values σ(Kr,r,n) for even r and n ≥ 4r2 - r - 6 and for odd r and n ≥ 4r2 + 3r - 8 are determined. 相似文献
2.
Let Lct(G) denote the set of all lengths of closed trails that exist in an even graph G. A sequence (t
1,..., t
p
) of elements of Lct(G) adding up to |E(G)| is G-realisable provided there is a sequence (T
1,..., t
p
) of pairwise edge-disjoint closed trails in G such that T
i
is of length T
i
for i = 1,..., p. The graph G is arbitrarily decomposable into closed trails if all possible sequences are G-realisable. In the paper it is proved that if a ⩾ 1 is an odd integer and M
a,a
is a perfect matching in K
a,a
, then the graph K
a,a
-M
a,a
is arbitrarily decomposable into closed trails.
相似文献
3.
We prove that any complete bipartite graph K
a,b
, where a, b are even integers, can be decomposed into closed trails with prescribed even lengths. 相似文献
4.
For a complete bipartite graph to be decomposable into isomorphic cubes, certain conditions on the number of cube and bipartition vertices must hold. We prove these necessary conditions sufficient in some cases. For cubes of fixed dimension d (indeed for d-regular bipartite graphs in general) we show that proving sufficiency can be reduced to decomposing a finite number of complete bipartite graphs. When t = 2d−1 and r is the remainder on dividing t by d, we show Kt,t is decomposable into d-cubes and an r-factor, where if r > 0 this r-factor itself is decomposable into r-cubes. © 1996 John Wiley & Sons, Inc. 相似文献
5.
We say that two graphs G and H with the same vertex set commute if their adjacency matrices commute. In this article, we show that for any natural number r, the complete multigraph K is decomposable into commuting perfect matchings if and only if n is a 2‐power. Also, it is shown that the complete graph Kn is decomposable into commuting Hamilton cycles if and only if n is a prime number. © 2006 Wiley Periodicals, Inc. J Combin Designs 相似文献
6.
Harish Seshadri 《Proceedings Mathematical Sciences》2009,119(2):197-201
Using elementary comparison geometry, we prove: Let (M, g) be a simply-connected complete Riemannian manifold of dimension ≥ 3. Suppose that the sectional curvature K satisfies −1 − s(r) ≤ K ≤ −1, where r denotes distance to a fixed point in M. If lim
r → ∞ e2r
s(r) = 0, then (M, g) has to be isometric to ℍ
n
.
The same proof also yields that if K satisfies −s(r) ≤ K ≤ 0 where lim
r → ∞
r
2
s(r) = 0, then (M, g) is isometric to ℝ
n
, a result due to Greene and Wu.
Our second result is a local one: Let (M, g) be any Riemannian manifold. For a ∈ ℝ, if K ≤ a on a geodesic ball B
p
(R) in M and K = a on ∂B
p
(R), then K = a on B
p
(R). 相似文献
7.
Mathieu Florence 《Inventiones Mathematicae》2008,171(1):175-189
Let p be a prime number, let K be a field of characteristic not p, containing the p-th roots of unity, and let r≥1 be an integer. We compute the essential dimension of ℤ/p
r
ℤ over K (Theorem 4.1). In particular,
i) We have edℚ(ℤ/8ℤ)=4, a result which was conjectured by Buhler and Reichstein in 1995 (unpublished).
ii) We have edℚ(ℤ/p
r
ℤ)≥p
r-1. 相似文献
8.
Marat M. Arslanov Iskander Sh. Kalimullin Andrea Sorbi 《Archive for Mathematical Logic》2001,40(8):597-614
We show that the Δ0
2 enumeration degrees are dense. We also show that for every nonzero n-c. e. e-degree a, with n≥ 3, one can always find a nonzero 3-c. e. e-degree b such that b < a on the other hand there is a nonzero ωc. e. e-degree which bounds no nonzero n-c. e. e-degree.
Received: 13 June 2000 / Published online: 3 October 2001 相似文献
9.
David M. Bressoud 《Proceedings Mathematical Sciences》1987,97(1-3):61-66
Given a basic hypergeometric series with numerator parametersa
1,a
2, ...,a
r and denominator parametersb
2, ...,b
r, we say it isalmost poised ifb
i, =a
1
q
δ,i
a
i,δi = 0, 1 or 2, for 2 ≤i ≤r. Identities are given for almost poised series withr = 3 andr = 5 when a1, =q
−2n.
Partially supported by N.S.F. Grant No. DMS-8521580. 相似文献
10.
LetW be an algebraically closed filed of characteristic zero, letK be an algebraically closed field of characteristic zero, complete for an ultrametric absolute value, and letA(K) (resp. ℳ(K)) be the set of entire (resp. meromorphic) functions inK. For everyn≥7, we show that the setS
n(b) of zeros of the polynomialx
n−b (b≠0) is such that, iff, g ∈W[x] or iff, g ∈A(K), satisfyf
−1(S
n(b))=g
−1(S
n(b)), thenf
n=g
n. For everyn≥14, we show thatS
n(b) is such that iff, g ∈W({tx}) or iff, g ∈ ℳ(K) satisfyf
−1(S
n(b))=g
−1(S
n(b)), then eitherf
n=g
n, orfg is a constant. Analogous properties are true for complex entire and meromorphic functions withn≥8 andn≥15, respectively.
For everyn≥9, we show that the setY
n(c) of zeros of the polynomial
, (withc≠0 and 1) is an ursim ofn points forW[x], and forA(K). For everyn≥16, we show thatY
n(c) is an ursim ofn points forW(x), and for ℳ(K). We follow a method based on thep-adic Nevanlinna Theory and use certain improvement of a lemma obtained by Frank and Reinders. 相似文献
11.
José Felipe Voloch 《Bulletin of the Brazilian Mathematical Society》1985,16(2):29-39
LetK be a function field in one variable over ℂ anda
1,...,a
m
,b non-zero elements ofK, such thatb is linearly independent froma
1,...,a
m
over ℂ. We show that forn sufficiently large, the equation ∑
i=1
m
a
i
x
i
n
has no non-constant solutions inK. 相似文献
12.
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
13.
In this paper, we prove that if a, b and c are pairwise coprime positive integers such that a^2+b^2=c^r,a〉b,a≡3 (mod4),b≡2 (mod4) and c-1 is not a square, thena a^x+b^y=c^z has only the positive integer solution (x, y, z) = (2, 2, r).
Let m and r be positive integers with 2|m and 2 r, define the integers Ur, Vr by (m +√-1)^r=Vr+Ur√-1. If a = |Ur|,b=|Vr|,c = m^2+1 with m ≡ 2 (mod 4),a ≡ 3 (mod 4), and if r 〈 m/√1.5log3(m^2+1)-1, then a^x + b^y = c^z has only the positive integer solution (x,y, z) = (2, 2, r). The argument here is elementary. 相似文献
Let m and r be positive integers with 2|m and 2 r, define the integers Ur, Vr by (m +√-1)^r=Vr+Ur√-1. If a = |Ur|,b=|Vr|,c = m^2+1 with m ≡ 2 (mod 4),a ≡ 3 (mod 4), and if r 〈 m/√1.5log3(m^2+1)-1, then a^x + b^y = c^z has only the positive integer solution (x,y, z) = (2, 2, r). The argument here is elementary. 相似文献
14.
Peter Adams Elizabeth J. Billington Darryn E. Bryant Saad I. El-Zanati 《Graphs and Combinatorics》2002,18(1):31-51
The Hamilton-Waterloo problem asks for a 2-factorisation of K
v
in which r of the 2-factors consist of cycles of lengths a
1,a
2,…,a
t
and the remaining s 2-factors consist of cycles of lengths b
1,b
2,…,b
u
(where necessarily ∑
i=1
t
a
i
=∑
j=1
u
b
j
=v). In this paper we consider the Hamilton-Waterloo problem in the case a
i
=m, 1≤i≤t and b
j
=n, 1≤j≤u. We obtain some general constructions, and apply these to obtain results for (m,n)∈{(4,6),(4,8),(4,16),(8,16),(3,5),(3,15),(5,15)}.
Received: July 5, 2000 相似文献
15.
Meng-xiao Yin 《应用数学学报(英文版)》2006,22(3):451-456
Let a(Kr,+1 - K3,n) be the smallest even integer such that each n-term graphic sequence п= (d1,d2,…dn) with term sum σ(п) = d1 + d2 +…+ dn 〉 σ(Kr+1 -K3,n) has a realization containing Kr+1 - K3 as a subgraph, where Kr+1 -K3 is a graph obtained from a complete graph Kr+1 by deleting three edges which form a triangle. In this paper, we determine the value σ(Kr+1 - K3,n) for r ≥ 3 and n ≥ 3r+ 5. 相似文献
16.
Let R be a noetherian ring,
\mathfraka{\mathfrak{a}} an ideal of R, and M an R-module. We prove that for a finite module M, if
Hi\mathfraka(M){{\rm H}^{i}_{\mathfrak{a}}(M)} is minimax for all i ≥ r ≥ 1, then
Hi\mathfraka(M){{\rm H}^{i}_{\mathfrak{a}}(M)} is artinian for i ≥ r. A local–global principle for minimax local cohomology modules is shown. If
Hi\mathfraka(M){{\rm H}^{i}_{\mathfrak{a}}(M)} is coatomic for i ≤ r (M finite) then
Hi\mathfraka(M){{\rm H}^{i}_{\mathfrak{a}}(M)} is finite for i ≤ r. We give conditions for a module which is locally minimax to be a minimax module. A non-vanishing theorem and some vanishing
theorems are proved for local cohomology modules. 相似文献
17.
N. M. Timofeev 《Mathematical Notes》1999,66(4):474-488
Suppose thatg(n) is equal to the number of divisors ofn, counting multiplicity, or the number of divisors ofn, a≠0 is an integer, andN(x,b)=|{n∶n≤x, g(n+a)−g(n)=b orb+1}|. In the paper we prove that sup
b
N(x,b)≤C(a)x)(log log 10
x
)−1/2 and that there exists a constantC(a,μ)>0 such that, given an integerb |b|≤μ(log logx)1/2,x≥x
o, the inequalityN(x,b)≥C(a,μ)x(log logx(−1/2) is valid.
Translated fromMatematicheskie Zametki, Vol. 66, No. 4, pp. 579–595, October, 1999. 相似文献
18.
Andrei V. Prasolov 《Annali dell'Universita di Ferrara》2007,53(2):381-392
We propose a new cryptographic scheme of ElGamal type. The scheme is based on algebraic systems defined in the paper—semialgebras
(Sect. 2). The main examples are semialgebras of polynomial mappings over a finite field K, and their factor-semialgebras. Given such a semialgebra R, one chooses an invertible element a ∈ R
* of finite order r, and a random integer s. One chooses also a finite dimensional K-submodule V of R. The 4-tuple (R, V, a, b) where b = a
s
forms the public key for the cryptosystem, while r and s form the secret key. A plain text can be viewed as a sequence of elements of the field K. That sequence is divided into blocks of length dim(V) which, in turn, correspond to uniquely determined elements X
i
of V. We propose three different methods (A, B, and C, see Definition 1.1) of encoding/decoding the sequence of X
i
. The complexity of cracking the proposed cryptosystem is based on the Discrete Logarithm Problem for polynomial mappings
(see Sect. 1.1). No methods of cracking the problem, except for the “brute force” (see Sect. 1.1) with Ω(r) time, are known so far.
相似文献
19.
Huiling Le 《Probability Theory and Related Fields》1999,114(1):85-96
Suppose that M is a complete, simply connected Riemannian manifold of non-positive sectional curvature with dimension m≥ 3 and that, outside a fixed compact set, the sectional curvatures are bounded above by −c
1/{r
2 ln r} and below by −c
2
r
2, where c
1 and c
2 are two positive constants and r is the geodesic distance from a fixed point. We show that, when κ≥ 1 satisfies certain conditions, the angular part of a
κ-quasi-conformal Γ-martingale on M tends to a limit as time tends to infinity and the closure of the support of the distribution of this limit is the entire
sphere at infinity. This improves both a result of Le for Brownian motion and also results concerning the non-existence of
κ-quasi-conformal harmonic maps from certain types of Riemannian manifolds into M.
Received: 19 September 1997 相似文献
20.
Let n ≥ 2 be a fixed positive integer, q ≥ 3 and c be two integers with (n, q) = (c, q) = 1. We denote by rn(51, 52, C; q) (δ 〈 δ1,δ2≤ 1) the number of all pairs of integers a, b satisfying ab ≡ c(mod q), 1 〈 a ≤δ1q, 1 ≤ b≤δ2q, (a,q) = (b,q) = 1 and nt(a+b). The main purpose of this paper is to study the asymptotic properties of rn (δ1, δ2, c; q), and give a sharp asymptotic formula for it. 相似文献