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1.
Let H be any graph. We determine up to an additive constant the minimum degree of a graph G which ensures that G has a perfect H-packing (also called an H-factor). More precisely, let δ(H,n) denote the smallest integer k such that every graph G whose order n is divisible by |H| and with δ(G)≥k contains a perfect H-packing. We show that
.
The value of χ*(H) depends on the relative sizes of the colour classes in the optimal colourings of H and satisfies χ(H)−1<χ*(H)≤χ(H). 相似文献
2.
Let Δn−1 denote the (n − 1)-dimensional simplex. Let Y be a random 2-dimensional subcomplex of Δn−1 obtained by starting with the full 1-dimensional skeleton of Δn−1 and then adding each 2−simplex independently with probability p. Let
denote the first homology group of Y with mod 2 coefficients. It is shown that for any function ω(n) that tends to infinity
* Supported by an Israel Science Foundation grant. 相似文献
3.
Jiong Sheng LI Jian Hua YIN 《数学学报(英文版)》2006,22(4):1133-1138
Let σ(k, n) be the smallest even integer such that each n-term positive graphic sequence with term sum at least σ(k, n) can be realized by a graph containing a clique of k + 1 vertices. Erdos et al. (Graph Theory, 1991, 439-449) conjectured that σ(k, n) = (k - 1)(2n- k) + 2. Li et al. (Science in China, 1998, 510-520) proved that the conjecture is true for k 〉 5 and n ≥ (k2) + 3, and raised the problem of determining the smallest integer N(k) such that the conjecture holds for n ≥ N(k). They also determined the values of N(k) for 2 ≤ k ≤ 7, and proved that [5k-1/2] ≤ N(k) ≤ (k2) + 3 for k ≥ 8. In this paper, we determine the exact values of σ(k, n) for n ≥ 2k+3 and k ≥ 6. Therefore, the problem of determining σ(k, n) is completely solved. In addition, we prove as a corollary that N(k) -= [5k-1/2] for k ≥6. 相似文献
4.
Let G be a graph with n vertices, m edges and a vertex degree sequence (d
1, d
2,..., d
n
), where d
1 ≥ d
2 ≥ ... ≥ d
n
. The spectral radius and the largest Laplacian eigenvalue are denoted by ϱ(G) and μ(G), respectively. We determine the graphs with
and the graphs with d
n
≥ 1 and
We also present some sharp lower bounds for the Laplacian eigenvalues of a connected graph.
The work was supported by National Nature Science Foundation of China (10201009), Guangdong Provincial Natural Science Foundation
of China (021072) and Com2MaC-KOSEF 相似文献
5.
For a positive integer n and R>0, we set
. Given R>1 and n≥4 we construct a sequence of analytic perturbations (H
j
) of the completely integrable Hamiltonian
on
, with unstable orbits for which we can estimate the time of drift in the action space. These functions H
j
are analytic on a fixed complex neighborhood V of
, and setting
the time of drift of these orbits is smaller than (C(1/ɛ
j
)1/2(n-3)) for a fixed constant c>0. Our unstable orbits stay close to a doubly resonant surface, the result is therefore almost optimal since the stability
exponent for such orbits is 1/2(n−2). An analogous result for Hamiltonian diffeomorphisms is also proved. Two main ingredients are used in order to deal with
the analytic setting: a version of Sternberg's conjugacy theorem in a neighborhood of a normally hyperbolic manifold in a
symplectic system, for which we give a complete (and seemingly new) proof; and Easton windowing method that allow us to approximately
localize the wandering orbits and estimate their speed of drift. 相似文献
6.
S. Mecheri 《Czechoslovak Mathematical Journal》2007,57(2):697-703
Let ℋ be a separable infinite dimensional complex Hilbert space, and let ℒ(H) denote the algebra of all bounded linear operators on ℋ into itself. Let A = (A
1, A
2,..., A
n), B = (B
1, B
2,..., B
n) be n-tuples of operators in ℒ(H); we define the elementary operators Δ
A,B
: ℒ(H) ↦ ℒ(H) by
.
In this paper, we characterize the class of pairs of operators A, B ∈ ℒ(H) satisfying Putnam-Fuglede’s property, i.e, the class of pairs of operators A,B ∈ ℒ(H) such that
implies
for all T ∈ C
1 (H) (trace class operators). The main result is the equivalence between this property and the fact that the ultraweak closure
of the range of the elementary operator ΔA,B is closed under taking adjoints. This leads us to give a new characterization of the orthogonality (in the sense of Birkhoff)
of the range of an elementary operator and its kernel in C
1 classes.
This work was supported by the research center project No. 2005-04. 相似文献
7.
Kâzim Ilhan Ikeda 《Proceedings Mathematical Sciences》2003,113(2):99-137
This paper which is a continuation of [2], is essentially expository in nature, although some new results are presented. LetK be a local field with finite residue class fieldK
k. We first define (cf. Definition 2.4) the conductorf(E/K) of an arbitrary finite Galois extensionE/K in the sense of non-abelian local class field theory as wheren
G is the break in the upper ramification filtration ofG = Gal(E/K) defined by
. Next, we study the basic properties of the idealf(E/K) inO
k in caseE/K is a metabelian extension utilizing Koch-de Shalit metabelian local class field theory (cf. [8]).
After reviewing the Artin charactera
G : G → ℂ ofG := Gal(E/K) and Artin representationsA
g G → G →GL(V) corresponding toa
G : G → ℂ, we prove that (Proposition 3.2 and Corollary 3.5)
where Χgr
: G → ℂ is the character associated to an irreducible representation ρ: G → GL(V) ofG (over ℂ). The first main result (Theorem 1.2) of the paper states that, if in particular,ρ : G → GL(V) is an irreducible representation ofG(over ℂ) with metabelian image, then
where Gal(Eker(ρ)/Eker(ρ)•) is any maximal abelian normal subgroup of Gal(Eker(ρ)/K) containing Gal(Eker(ρ)
/K)′, and the break nG/ker(ρ) in the upper ramification filtration of G/ker(ρ) can be computed and located by metabelian local class field theory. The
proof utilizes Basmaji’s theory on the structure of irreducible faithful representations of finite metabelian groups (cf.
[1]) and on metabelian local class field theory (cf. [8]).
We then discuss the application of Theorem 1.2 on a problem posed by Weil on the construction of a ‘natural’A
G ofG over ℂ (Problem 1.3). More precisely, we prove in Theorem 1.4 that ifE/K is a metabelian extension with Galois group G, then
Kazim İlhan ikeda whereN runs over all normal subgroups of G, and for such anN, V
n denotes the collection of all ∼-equivalence classes [ω]∼, where ‘∼’ denotes the equivalence relation on the set of all representations
ω : (G/N)• → ℂΧ satisfying the conditions Inert(ω) = {δ ∈ G/N : ℂδ} = ω =(G/N) and
where δ runs over R((G/N)•/(G/N)), a fixed given complete system of representatives of (G/N)•/(G/N), by declaring that ω1 ∼ ω2 if and only if ω1
= ω
2,δ for some δ ∈ R((G/N)•/(G/N)).
Finally, we conclude our paper with certain remarks on Problem 1.1 and Problem 1.3. 相似文献
8.
Zheng Yan LIN Sung Chul LEE 《数学学报(英文版)》2006,22(2):535-544
Let {Xn,n ≥ 0} be an AR(1) process. Let Q(n) be the rescaled range statistic, or the R/S statistic for {Xn} which is given by (max1≤k≤n(∑j=1^k(Xj - ^-Xn)) - min 1≤k≤n(∑j=1^k( Xj - ^Xn ))) /(n ^-1∑j=1^n(Xj -^-Xn)^2)^1/2 where ^-Xn = n^-1 ∑j=1^nXj. In this paper we show a law of iterated logarithm for rescaled range statistics Q(n) for AR(1) model. 相似文献
9.
A. V. Demyanov 《Journal of Mathematical Sciences》2006,136(2):3706-3717
The problem of establishing necessary and sufficient conditions for l.s.c. under PDE constraints is studied for a special
class of functionals:
with respect to the convergence un → u in measure, vn ⇀ v in Lp(Ω;ℝd)
in W−1,p(Ω), and χn ⇀ χ in Lp(Ω), where χn ∈ Z:= {χ ∈ L∞(Ω): 0 ≤ χ(x) ≤ 1 for a.e. x}. Here
is a constant-rank partial differential operator. The main result is that if the characteristic cone of
has the full dimension, then the l.s.c. is equivalent to the fact that the F± are both
-quasiconvex and
for a.e. x ∈ Ω and for all u ∈ ℝd. As a corollary, we obtain several results for the functional
with respect to the same convergence. We show that this functional is l.s.c. iff
Bibliography: 14 titles.
Published in Zapiski Nauchnykh Seminarov POMI, Vol. 318, 2004, pp. 100–119. 相似文献
10.
We study the irrational factor function I(n) introduced by Atanassov and defined by , where is the prime factorization of n. We show that the sequence {G(n)/n}
n≧1, where G(n) = Π
ν=1
n
I(ν)1/n
, is convergent; this answers a question of Panaitopol. We also establish asymptotic formulas for averages of the function
I(n).
Research of the third author is supported in part by NSF grant number DMS-0456615. 相似文献
11.
We investigate the maximum number of edges that a graph G can have if it does not contain a given graph H as a minor (subcontraction). Let
We define a parameter γ(H) of the graph H and show that, if H has t vertices, then
where α = 0.319. . . is an explicit constant and o(1) denotes a term tending to zero as t→∞. The extremal graphs are unions of pseudo-random graphs.
If H has t1+τ edges then
, equality holding for almost all H and for all regular H. We show how γ(H) might be evaluated for other graphs H also, such as complete multi-partite graphs.
* Research supported by EPSRC studentship 99801140. 相似文献
12.
Pu Zhang 《数学学报(英文版)》2008,24(8):1387-1400
Let μ be the n-dimensional Marcinkiewicz integral and μb the multilinear commutator of μ. In this paper, the following weighted inequalities are proved for ω ∈ A∞ and 0 〈 p 〈 ∞,
||μ(f)||LP(ω)≤C|Mf|LP(ω) and ||μb(f)||LP(ω)≤C||ML(log L)^1/r f||LP(ω).
The weighted weak L(log L)^1/r -type estimate is also established when p=1 and ω∈A1. 相似文献
||μ(f)||LP(ω)≤C|Mf|LP(ω) and ||μb(f)||LP(ω)≤C||ML(log L)^1/r f||LP(ω).
The weighted weak L(log L)^1/r -type estimate is also established when p=1 and ω∈A1. 相似文献
13.
Linghai ZHANG 《数学年刊B辑(英文版)》2008,29(2):179-198
Let u=u(x,t,uo)represent the global solution of the initial value problem for the one-dimensional fluid dynamics equation ut-εuxxt+δux+γHuxx+βuxxx+f(u)x=αuxx,u(x,0)=uo(x), whereα〉0,β〉0,γ〉0,δ〉0 andε〉0 are constants.This equation may be viewed as a one-dimensional reduction of n-dimensional incompressible Navier-Stokes equations. The nonlinear function satisfies the conditions f(0)=0,|f(u)|→∞as |u|→∞,and f∈C^1(R),and there exist the following limits Lo=lim sup/u→o f(u)/u^3 and L∞=lim sup/u→∞ f(u)/u^5 Suppose that the initial function u0∈L^I(R)∩H^2(R).By using energy estimates,Fourier transform,Plancherel's identity,upper limit estimate,lower limit estimate and the results of the linear problem vt-εv(xxt)+δvx+γHv(xx)+βv(xxx)=αv(xx),v(x,0)=vo(x), the author justifies the following limits(with sharp rates of decay) lim t→∞[(1+t)^(m+1/2)∫|uxm(x,t)|^2dx]=1/2π(π/2α)^(1/2)m!!/(4α)^m[∫R uo(x)dx]^2, if∫R uo(x)dx≠0, where 0!!=1,1!!=1 and m!!=1·3…(2m-3)…(2m-1).Moreover lim t→∞[(1+t)^(m+3/2)∫R|uxm(x,t)|^2dx]=1/2π(x/2α)^(1/2)(m+1)!!/(4α)^(m+1)[∫Rρo(x)dx]^2, if the initial function uo(x)=ρo′(x),for some functionρo∈C^1(R)∩L^1(R)and∫Rρo(x)dx≠0. 相似文献
14.
Hong Lin Xiao-feng Guo 《应用数学学报(英文版)》2007,23(1):155-160
Let φ(G),κ(G),α(G),χ(G),cl(G),diam(G)denote the number of perfect matchings,connectivity,independence number,chromatic number,clique number and diameter of a graph G,respectively.In this note,by constructing some extremal graphs,the following extremal problems are solved:1.max{φ(G):|V(G)|=2n,κ(G)≤k}=k[(2n-3)!!],2.max{φ(G):|V(G)|=2n,α(G)≥k}=[multiply from i=0 to k-1(2n-k-i)[(2n-2k-1)!!],3.max{φ(G):|V(G)|=2n,χ(G)≤k}=φ(T_(k,2n))T_(k,2n)is the Turán graph,that is a complete k-partite graphon 2n vertices in which all parts are as equal in size as possible,4.max{φ(G):|V(G)|=2n,cl(G)=2}=n1,5.max{φ(G):|V(G)|=2n,diam(G)≥2}=(2n-2)(2n-3)[(2n-5)!!],max{φ(G):|V(G)|=2n,diam(G)≥3}=(n-1)~2[(2n-5)!!]. 相似文献
15.
A graph G with p vertices and q edges, vertex set V(G) and edge set E(G), is said to be super vertex-graceful (in short SVG), if there exists a function pair (f, f
+) where f is a bijection from V(G) onto P, f
+ is a bijection from E(G) onto Q, f
+((u, v)) = f(u) + f(v) for any (u, v) ∈ E(G),
and
We determine here families of unicyclic graphs that are super vertex-graceful.
相似文献
16.
Jing YANG Shi Xin LUO Ke Qin FENG 《数学学报(英文版)》2006,22(3):833-844
Assume that m ≥ 2, p is a prime number, (m,p(p - 1)) = 1,-1 not belong to 〈p〉 belong to (Z/mZ)^* and [(Z/mZ)^*:〈p〉]=4.In this paper, we calculate the value of Gauss sum G(X)=∑x∈F^*x(x)ζp^T(x) over Fq,where q=p^f,f=φ(m)/4,x is a multiplicative character of Fq and T is the trace map from Fq to Fp.Under our assumptions,G(x) belongs to the decomposition field K of p in Q(ζm) and K is an imaginary quartic abelian unmber field.When the Galois group Gal(K/Q) is cyclic,we have studied this cyclic case in anotyer paper:"Gauss sums of index four:(1)cyclic case"(accepted by Acta Mathematica Sinica,2003).In this paper we deal with the non-cyclic case. 相似文献
17.
Aleksandar Ivić 《Central European Journal of Mathematics》2004,2(4):494-508
Let Δ(x) denote the error term in the Dirichlet divisor problem, and E(T) the error term in the asymptotic formula for the mean square of
. If
with
, then we obtain
. We also show how our method of proof yields the bound
, where T
1/5+ε≤G≪T, T<t
1<...<t
R
≤2T, t
r
+1−t
r
≥5G (r=1, ..., R−1). 相似文献
18.
A. A. Ryabinin 《Mathematical Notes》1998,64(5):629-633
The system
, where Λ={λ
n
} is the set of zeros (of multiplicitiesm
n
) of the Fourier transform
of a singular Cantor-Lebesgue measure, is examined. We prove thate(Λ) is complete and minimal inL
p
(−a, a) withp≥1, and that |L(x+iy)|2 does not satisfy the Muckenhoupt condition on any horizontal line Imz=y≠0 in the complex plane. This implies thate(Λ) does not have the property of convergence extension.
Translated fromMatematicheskie Zametki, Vol. 64, No. 5, pp. 728–733, November, 1998. 相似文献
19.
Elton Pasku 《Semigroup Forum》2008,76(3):427-468
If a monoid S is given by some finite complete presentation ℘, we construct inductively a chain of CW-complexes
such that Δ
n
has dimension n, for every 2≤m≤n, the m-skeleton of Δ
n
is Δ
m
, and p
m
are critical (m+1)-cells with 1≤m≤n−2. For every 2≤m≤n−1, the following is an exact sequence of (ℤS,ℤS)-bimodules
where
if m=2. We then use these sequences to obtain a free finitely generated bimodule partial resolution of ℤS. Also we show that for groups properties FDT and FHT coincide. 相似文献
20.
NOTES ON GLAISHER'S CONGRUENCES 总被引:1,自引:0,他引:1
HONG Shaofang 《数学年刊B辑(英文版)》2000,21(1):33-38
Let p be an odd prime and let n≥1,k≥0 and r be integers,denote by Bk the kth Bernoulli number,It is proved that(i) If r≥1 is odd and suppose 1≥r+4,then ∑j=1^p-1 1/(np+j)^r=-(2n+1)r(r+1)/2(r+2)Bp-r-2p^2(mod p^3).(ii)If r≥2 is even and suppose p≥r+3, then p-1∑j=1 1/(np+j)^r=r/r+1Bv-r-1p(mod P^2).(iii) p-1∑j=1 1/(np+j)p-2=-(2n+1)p(mod P^2).This result generalizes the Glaisher‘s congruence. As a corollary, a generalization of the Wolsten-holme‘s theorem is obtained. 相似文献