共查询到20条相似文献,搜索用时 31 毫秒
1.
Andreas Weingartner 《Journal of Number Theory》2004,108(1):18-28
Let 1=d1(n)<d2(n)<?<dτ(n)=n be the sequence of all positive divisors of the integer n in increasing order. We say that the divisors of n are t-dense iff max1?i<τ(n)di+1(n)/di(n)?t. Let D(x,t) be the number of positive integers not exceeding x whose divisors are t-dense. We show that for x?3, and , we have , where , and d(w) is a continuous function which satisfies d(w)?1/w for w?1. We also consider other counting functions closely related to D(x,t). 相似文献
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Zhi-Hong Sun 《Journal of Number Theory》2007,124(1):62-104
Let p>3 be a prime, u,v,d∈Z, gcd(u,v)=1, p?u2−dv2 and , where is the Legendre symbol. In the paper we mainly determine the value of by expressing p in terms of appropriate binary quadratic forms. As applications, for we obtain a general criterion for and a criterion for εd to be a cubic residue of p, where εd is the fundamental unit of the quadratic field . We also give a general criterion for , where {Un} is the Lucas sequence defined by U0=0, U1=1 and Un+1=PUn−QUn−1 (n?1). Furthermore, we establish a general result to illustrate the connections between cubic congruences and binary quadratic forms. 相似文献
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In this note we show that a harmonic quasiconformal mapping f=u+iv with respect to the Poincaré metric of the upper half plane onto itself such that v(x,y)=v(y) or u(x,y)=u(x) is a conformal mapping. 相似文献
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Toru Kojima 《Discrete Mathematics》2008,308(7):1282-1295
The bandwidth B(G) of a graph G is the minimum of the quantity max{|f(x)-f(y)|:xy∈E(G)} taken over all proper numberings f of G. The strong product of two graphs G and H, written as G(SP)H, is the graph with vertex set V(G)×V(H) and with (u1,v1) adjacent to (u2,v2) if one of the following holds: (a) u1 and v1 are adjacent to u2 and v2 in G and H, respectively, (b) u1 is adjacent to u2 in G and v1=v2, or (c) u1=u2 and v1 is adjacent to v2 in H. In this paper, we investigate the bandwidth of the strong product of two connected graphs. Let G be a connected graph. We denote the diameter of G by D(G). Let d be a positive integer and let x,y be two vertices of G. Let denote the set of vertices v so that the distance between x and v in G is at most d. We define δd(G) as the minimum value of over all vertices x of G. Let denote the set of vertices z such that the distance between x and z in G is at most d-1 and z is adjacent to y. We denote the larger of and by . We define η(G)=1 if G is complete and η(G) as the minimum of over all pair of vertices x,y of G otherwise. Let G and H be two connected graphs. Among other results, we prove that if δD(H)(G)?B(G)D(H)+1 and B(H)=⌈(|V(H)|+η(H)-2)/D(H)⌉, then B(G(SP)H)=B(G)|V(H)|+B(H). Moreover, we show that this result determines the bandwidth of the strong product of some classes of graphs. Furthermore, we study the bandwidth of the strong product of power of paths with complete bipartite graphs. 相似文献
7.
The Wiener index W(G)=∑{u,v}⊂V(G)d(u,v), the hyper-Wiener index and the reverse-Wiener index , where d(u,v) is the distance of two vertices u,v in G, d2(u,v)=d(u,v)2, n=|V(G)| and D is the diameter of G. In [M. Eliasi, B. Taeri, Four new sums of graphs and their Wiener indices, Discrete Appl. Math. 157 (2009) 794-803], Eliasi and Taeri introduced the F-sums of two connected graphs. In this paper, we determine the hyper- and reverse-Wiener indices of the F-sum graphs and, subject to some condition, we present some exact expressions of the reverse-Wiener indices of the F-sum graphs. 相似文献
8.
Sebastián Lorca 《Journal of Mathematical Analysis and Applications》2004,295(1):276-286
We study the existence of positive solutions to the elliptic equation ε2Δu(x,y)−V(y)u(x,y)+f(u(x,y))=0 for (x,y) in an unbounded domain subject to the boundary condition u=0 whenever is nonempty. Our potential V depends only on the y variable and is a bounded or unbounded domain which may coincide with . The positive parameter ε is tending to zero and our solutions uε concentrate along minimum points of the unbounded manifold of critical points of V. 相似文献
9.
Jie Xiao 《Journal of Differential Equations》2006,224(2):277-295
Let u(t,x) be the solution of the heat equation (∂t-Δx)u(t,x)=0 on subject to u(0,x)=f(x) on Rn. The main goal of this paper is to characterize such a nonnegative measure μ on that f(x)?u(t2,x) induces a bounded embedding from the Sobolev space , p∈[1,n) into the Lebesgue space , q∈(0,∞). 相似文献
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Zhi-Hong Sun 《Journal of Number Theory》2005,114(1):88-123
If and are two sequences such that a1=b1 and , then we say that (an,bn) is a Newton-Euler pair. In the paper, we establish many formulas for Newton-Euler pairs, and then make use of them to obtain new results concerning some special sequences such as and Bn, where p(n) is the number of partitions of n, σ(n) is the sum of divisors of n, and Bn is the nth Bernoulli number. 相似文献
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In this paper, we show that if (un)n?1 is a Lucas sequence, then the Diophantine equation in integers n?1, k?1, m?2 and y with |y|>1 has only finitely many solutions. We also determine all such solutions when (un)n?1 is the sequence of Fibonacci numbers and when un=(xn-1)/(x-1) for all n?1 with some integer x>1. 相似文献
12.
Paul Pollack 《Journal of Number Theory》2010,130(8):1732-1736
Write s(n) for the sum of the proper divisors of the natural number n. We call n sociable if the sequence n, s(n), s(s(n)), … is purely periodic; the period is then called the order of sociability of n. The ancients initiated the study of order 1 sociables (perfect numbers) and order 2 sociables (amicable numbers), and investigations into higher-order sociable numbers began at the end of the 19th century. We show that if k is odd and fixed, then the number of sociable n?x of order k is bounded by as x→∞. This improves on the previously best-known bound of , due to Kobayashi, Pollack, and Pomerance. 相似文献
13.
Florian Luca 《Journal of Number Theory》2003,102(2):298-305
In this paper, we prove two results. The first theorem uses a paper of Kim (J. Number Theory 74 (1999) 307) to show that for fixed primes p1,…,pk, and for fixed integers m1,…,mk, with , the numbers (ep1(n),…,epk(n)) are uniformly distributed modulo (m1,…,mk), where ep(n) is the order of the prime p in the factorization of n!. That implies one of Sander's conjectures from Sander (J. Number Theory 90 (2001) 316) for any set of odd primes. Berend (J. Number Theory 64 (1997) 13) asks to find the fastest growing function f(x) so that for large x and any given finite sequence , there exists n<x such that the congruences hold for all i?f(x). Here, pi is the ith prime number. In our second result, we are able to show that f(x) can be taken to be at least , with some absolute constant c1, provided that only the first odd prime numbers are involved. 相似文献
14.
Sankar Sitaraman 《Journal of Number Theory》2003,99(1):29-35
Let p>5 be a prime number and ζ a pth root of unity. Let c be an integer divisible only by primes of the form kp−1,(k,p)=1.Let Cp(i) be the eigenspace of the p-Sylow subgroup of ideal class group C of corresponding to ωi,ω being the Teichmuller character.In this article we extend the main theorem in Sitaraman (J. Number Theory 80 (2000) 174) and get the following: For any fixed odd positive integer n<p−4, assume:
- (a)
- At least one of Cp(3),Cp(5),…,Cp(n) is non-trivial.
- (b)
- Cp(i)=0 for p−n−1?i?p−2.
- (c)
- for 1?i?n+1.
15.
C. Hooley 《Journal of Number Theory》2009,129(6):1443-1455
The following theorem is proved. Suppose that for integers r,s?2, f(x,y) is an inhomogeneous polynomial of degree r with rational integral coefficients that is irreducible over the rationals, that is not a polynomial in a linear combination of x and y, that has no fixed sth power divisors other than 1, and that is a product of linear factors over some extension field of the rationals. Then, if N(X) denote the number of integers m,n of magnitude not exceeding X for which f(m,n) is sth power-free, the asymptotic formula
16.
John Brillhart 《Journal of Number Theory》2004,106(1):79-111
Using the theory of elliptic curves, we show that the class number h(−p) of the field appears in the count of certain factors of the Legendre polynomials , where p is a prime >3 and m has the form (p−e)/k, with k=2,3 or 4 and . As part of the proof we explicitly compute the Hasse invariant of the Hessian curve y2+αxy+y=x3 and find an elementary expression for the supersingular polynomial ssp(x) whose roots are the supersingular j-invariants of elliptic curves in characteristic p. As a corollary we show that the class number h(−p) also shows up in the factorization of certain Jacobi polynomials. 相似文献
17.
We study the stability of conservative solutions of the Cauchy problem for the Camassa-Holm equation ut−uxxt+κux+3uux−2uxuxx−uuxxx=0 with periodic initial data u0. In particular, we derive a new Lipschitz metric dD with the property that for two solutions u and v of the equation we have dD(u(t),v(t))?eCtdD(u0,v0). The relationship between this metric and usual norms in and is clarified. 相似文献
18.
Chun-Gil Park 《Journal of Mathematical Analysis and Applications》2005,307(2):753-762
It is shown that every almost linear bijection of a unital C∗-algebra A onto a unital C∗-algebra B is a C∗-algebra isomorphism when h(n2uy)=h(n2u)h(y) for all unitaries u∈A, all y∈A, and n=0,1,2,…, and that almost linear continuous bijection of a unital C∗-algebra A of real rank zero onto a unital C∗-algebra B is a C∗-algebra isomorphism when h(n2uy)=h(n2u)h(y) for all , all y∈A, and n=0,1,2,…. Assume that X and Y are left normed modules over a unital C∗-algebra A. It is shown that every surjective isometry , satisfying T(0)=0 and T(ux)=uT(x) for all x∈X and all unitaries u∈A, is an A-linear isomorphism. This is applied to investigate C∗-algebra isomorphisms between unital C∗-algebras. 相似文献
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R.C. Vaughan 《Journal of Number Theory》2003,100(1):169-183
Let r(n) denote the number of integral ideals of norm n in a cubic extension K of the rationals, and define and Δ(x)=S(x)−αx where α is the residue of the Dedekind zeta function ζ(s,K) at 1. It is shown that the abscissa of convergence of