共查询到20条相似文献,搜索用时 15 毫秒
1.
Jeong Ja Bae 《数学物理学报(B辑英文版)》2009,29(5):1203-1215
It is proved that the global existence for the nonhomogeneous quasilinear wave equation with a localized weakly nonlinear dissipation in exterior domains. 相似文献
2.
《Numerical Functional Analysis & Optimization》2013,34(3-4):441-453
The purpose of the paper is to present a unified numerical method for problems consisting of the conventional boundary value problem. Cauchy problem, under-determined problem, and over-determined problem. The method is based on the direct variational approach, which paraphrases the problems into the primary and adjoint boundary value problems that can be tackled by commonly used computer programs for the numerical solution of the Laplace equation. 相似文献
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4.
In this paper, we consider mixed problems with a spacelike boundary derivative condition for semilinear wave equations with exponential nonlinearities in a quarter plane. Results similar to those obtained earlier by Caffarelli-Friedman for Cauchy problems and power nonlinearities are proved in the present situation, namely we show that solutions either are global or blow up on a spacelike curve. Weaker results are also obtained if the boundary vector field is tangent to the characteristic which leaves the domain in the future. Received January 7, 2000 / Accepted July 17, 2000 /Published online December 8, 2000 相似文献
5.
Fer's factorization as a symplectic integrator 总被引:1,自引:0,他引:1
F. Casas 《Numerische Mathematik》1996,74(3):283-303
Summary.
In this paper we analyze the main
features of the so-called Fer expansion as a new
method for integrating the ordinary differential
equations derived from explicitly time-dependent
Hamiltonian dynamical systems. This method is
based on a factorization of the evolution operator as
an infinite product of exponentials of Lie operators
and thus exactly preserves the Poincaré integral
invariants. Third and fourth-order expansions are
considered and numerical results are presented for a
quadratic Hamiltonian with various time-dependent
frequencies. Comparison is done with other
numerical integration schemes.
Received
July 11, 1994 / Revised version received August 8, 1995 相似文献
6.
This paper is concerned with the stability of the rarefaction wave for the generalized KdV-Burgers equationRoughly speaking, under the assumption that u_ < u+, the solution u(x,t) to Cauchy problem (1) satisfying sup \u(x,t) -uR(x/t)| -0 as t - , where uR(x/t) is the rarefac-tion wave of the non- viscous Burgers equation ut + f(u)x=0 with Riemann initial data 相似文献
7.
Hong Wang 《Combinatorica》1998,18(3):441-447
. Our main result is as follows: For any integer , if G is a claw-free graph of order at least and with minimum degree at least 3, then G contains k vertex-disjoint triangles unless G is of order and G belongs to a known class of graphs. We also construct a claw-free graph with minimum degree 3 on n vertices for each such that it does not contain k vertex-disjoint triangles. We put forward a conjecture on vertex-disjoint triangles in -free graphs.
Received: November 21, 1996/Revised: Revised February 19, 1998 相似文献
8.
The finite endodualisable double Stone algebras are characterised, and every finite endoprimal double Stone algebra is shown
to be endodualisable.
The authors wish to express their gratitude to B. A. Davey and T. Katriňák for their helpful remarks and to J. G. Pitkethly
for her assistance with the pictures. A support by Slovak grants VEGA 1/4057/97, 1/3026/06 and APVV-51-009605 is acknowledged
by the first author who also wishes to thank the Mathematical Institute of the University of Oxford and the School of Mathematical
and Statistical Sciences of La Trobe University for their hospitality. 相似文献
9.
Mekkia Kouider 《Combinatorica》2000,20(2):219-226
G =(V,E) is a 2-connected graph, and X is a set of vertices of G such that for every pair x,x' in X, , and the minimum degree of the induced graph <X> is at least 3, then X is covered by one cycle.
This result will be in fact generalised by considering tuples instead of pairs of vertices.
Let be the minimum degree in the induced graph <X>. For any ,
.
If , and , then X is covered by at most (p-1) cycles of G. If furthermore , (p-1) cycles are sufficient.
So we deduce the following:
Let p and t () be two integers.
Let G be a 2-connected graph of order n, of minimum degree at least t. If , and , then V is covered by at most cycles, where k is the connectivity of G.
If furthermore , (p-1) cycles are sufficient.
In particular, if and , then G is hamiltonian.
Received April 3, 1998 相似文献
10.
A.F.M. ter Elst Derek W. Robinson 《Calculus of Variations and Partial Differential Equations》1999,8(4):327-363
Let G be a connected Lie group with Lie algebra and an algebraic basis of . Further let denote the generators of left translations, acting on the -spaces formed with left Haar measure dg, in the directions . We consider second-order operators corresponding to a quadratic form with complex coefficients , , , . The principal coefficients are assumed to be H?lder continuous and the matrix is assumed to satisfy the (sub)ellipticity condition uniformly over G. We discuss the hierarchy relating smoothness properties of the coefficients of H with smoothness of the kernel. Moreover, we establish Gaussian type bounds for the kernel and its derivatives. Similar theorems are proved for operators in nondivergence form for which the principal coefficients are at least once differentiable. Received January 24, 1997 / Accepted June 5, 1998 相似文献
11.
Let be a hypergraph. A panchromatic t-colouring of is a t-colouring of its vertices such that each edge has at least one vertex of each colour; and is panchromatically t-choosable if, whenever each vertex is given a list of t colours, the vertices can be coloured from their lists in such a way that each edge receives at least t different colours. The Hall ratio of is . Among other results, it is proved here that if every edge has at least t vertices and whenever , then is panchromatically t-choosable, and this condition is sharp; the minimum such that every t-uniform hypergraph with is panchromatically t-choosable satisfies ; and except possibly when t = 3 or 5, a t-uniform hypergraph is panchromatically t-colourable if whenever , and this condition is sharp. This last result dualizes to a sharp sufficient condition for the chromatic index of a hypergraph
to equal its maximum degree.
Received November 10, 1998
RID="*"
ID="*" This work was carried out while the first author was visiting Nottingham, funded by Visiting Fellowship Research Grant
GR/L54585 from the Engineering and Physical Sciences Research Council. The work of this author was also partly supported by
grants 96-01-01614 and 97-01-01075 of the Russian Foundation for Fundamental Research. 相似文献
12.
《偏微分方程通讯》2013,38(11-12):2065-2091
13.
The product of operators with closed range in Hilbert C-modules 总被引:1,自引:0,他引:1
K. Sharifi 《Linear algebra and its applications》2011,435(5):1122-1130
Suppose T and S are bounded adjointable operators with close range between Hilbert C∗-modules, then TS has closed range if and only if Ker(T)+Ran(S) is an orthogonal summand, if and only if Ker(S∗)+Ran(T∗) is an orthogonal summand. Moreover, if the Dixmier (or minimal) angle between Ran(S) and Ker(T)∩[Ker(T)∩Ran(S)]⊥ is positive and is an orthogonal summand then TS has closed range. 相似文献
14.
Terence Tao 《Mathematische Zeitschrift》2001,238(2):215-268
Recently Wolff [25] obtained a nearly sharp bilinear restriction theorem for bounded subsets of the cone in general dimension. We obtain the endpoint of Wolff's estimate and generalize to the case when one of the subsets is large. As a consequence, we are able to deduce some nearly-sharp null form estimates. Received: 24 September 1999 / in final form: 25 April 2000 / Published online: 4 May 2001 相似文献
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17.
Morris Newman 《Linear and Multilinear Algebra》2013,61(4):363-366
Let Rbe a principal ideal ringRn the ring of n× nmatrices over R, and dk (A) the kth determinantal divisor of Afor 1 ? k? n, where Ais any element of Rn , It is shown that if A,BεRn , det(A) det(B:) ≠ 0, then dk (AB) ≡ 0 mod dk (A) dk (B). If in addition (det(A), det(B)) = 1, then it is also shown that dk (AB) = dk (A) dk (B). This provides a new proof of the multiplicativity of the Smith normal form for matrices with relatively prime determinants. 相似文献
18.
Svante Linusson 《Combinatorica》1999,19(2):255-266
M -sequences (a.k.a. f-vectors for multicomplexes or O-sequences) in terms of the number of variables and a maximum degree. In particular, it is shown that the number of M-sequences for at most 2 variables are powers of two and for at most 3 variables are Bell numbers. We give an asymptotic estimate
of the number of M-sequences when the number of variables is fixed. This leads to a new lower bound for the number of polytopes with few vertices.
We also prove a similar recursive formula for the number of f-vectors for simplicial complexes. Keeping the maximum degree fixed we get the number of M-sequences and the number of f-vectors for simplicial complexes as polynomials in the number of variables and it is shown that these numbers are asymptotically
equal.
Received: February 28, 1996/Revised: February 26, 1998 相似文献
19.
Noga Alon 《Combinatorica》1998,18(3):301-310
For an undirected graph , let denote the graph whose vertex set is in which two distinct vertices and are adjacent iff for all i between 1 and n either or . The Shannon capacity c(G) of G is the limit , where is the maximum size of an independent set of vertices in . We show that there are graphs G and H such that the Shannon capacity of their disjoint union is (much) bigger than the sum of their capacities. This disproves
a conjecture of Shannon raised in 1956.
Received: December 8, 1997 相似文献
20.
《偏微分方程通讯》2013,38(5-6):1161-1181
Abstract A symbolic calculus for the transposes of a class of bilinear pseudodifferential operators is developed. The calculus is used to obtain boundedness results on products of Lebesgue spaces. A larger class of pseudodifferential operators that does not admit a calculus is also considered. Such a class is the bilinear analog of the so-called exotic class of linear pseudodifferential operators and fail to produce bounded operators on products of Lebesgue spaces. Nevertheless, the operators are shown to be bounded on products of Sobolev spaces with positive smoothness, generalizing the Leibniz rule estimates for products of functions. 相似文献