共查询到20条相似文献,搜索用时 62 毫秒
1.
Jesüs M. Ruiz 《manuscripta mathematica》1984,46(1-3):193-214
Let XoR
n be an irreducible analytic germ and the order space of its field of meromorphicfunetion germs. A formal half-branch in Xo is a kind of C-map germ c[0,)Xo; an ordering is centered at c if it contains the functions which are positive on c. We obtain a partition 1,...,d, d=dim Xo, of the set * of central (i.e.: centered at some half-branch) orderings, according to the dimension of half-branches. Then we show that all e, e= 1,.,d, as well as the set \* of noncentral orderings, are dense in . Finally, we solve the 17th Hubert Problem for analytic germs. 相似文献
2.
Jürgen Weyer 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1985,36(4):499-507
We consider the nonlinear diffusion equationu
t
–a(x, u
x
x
)+b(x, u)=g(x, u) with initial boundary conditions
andu(t, 0)=u(t, 1)=0. Here,a, b, andg denote some real functions which are monotonically increasing with respect to the second variable. Then, the corresponding stationary problem has a positive solution if and only if(0,
*) or(0,
*]. The endpoint
* can be estimated by
, where
1
u denotes the first eigenvalue of the stationary problem linearized at the pointu. The minimal positive steady state solutions are stable with respect to the nonlinear parabolic equation.
Zusammenfassung Wir betrachten die nichtlineare Diffusionsgleichungu t –a(x, u x ) x +b(x, u)=g(x, u) mit Randbedingungen undu (t, 0)=u (t, 1)=0. Dabei sinda, b, undg monoton wachsende Funktionen bzgl. des zweiten Argumentes. Das zugehörige stationäre Problem hat genau dann eine positive Lösung, falls (0, *) oder(0, *]. Der Endpunkt * kann durch abgeschätzt werden, wobei 1 u den ersten Eigenwert des an der Stelleu linearisierten stationären Problems bezeichnet. Die minimale positive stationäre Lösung ist stabil bzgl. der obigen nichtlinearen parabolischen Gleichung.相似文献
3.
[8] . , , [2] , . - , , , . . 相似文献
4.
Dr. Richard Weiss 《Monatshefte für Mathematik》1977,83(1):65-75
An undirected graph of valencyd and girth is called a (d, )-cage if its automorphism group acts transitively on the set of alls-paths in ands(+1)/2. We discuss an elementary construction of two known families of cages which allows us to prove easily some facts about their automorphism groups. We give, for example, a new proof of the fact that the automorphism group ofSp
4(2
n
) contains elements which are not induced by Sp
4(2
n
). 相似文献
5.
Qi-Man Shao 《Probability Theory and Related Fields》1992,94(1):119-133
Summary Let {X(t),t 0} be a stationary Gaussian process withEX(t)=0,EX
2(t)=1 and covariance function satisfying (i)r(t) = 1 2212;C |t | + o (|t|)ast0 for someC>0, 0<2; (ii)r(t)=0(t
–2) as t for some >0 and (iii) supts|r(t)|<1 for eachs>0. Put (t)= sup {s:0 s t,X(s) (2logs)1/2}. The law of the iterated logarithm implies
a.s. This paper gives the lower bound of (t) and obtains an Erds-Rèvèsz type LIL, i.e.,
a.s. if 0<<2 and
. Applications to infinite series of independent Ornstein-Uhlenbeck processes and to fractional Wiener processes are also given.Research supported by the Fok Yingtung Education Foundation of China and by Charles Phelps Taft Postdoctoral Fellowship of the University of Cincinnati 相似文献
6.
H. G. Othmer L. E. Scriven 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1973,24(1):135-139
Summary The number of independent invariants ofn×n matricesA, B and their products on which the eigenvalues () of the matrix pencilA+B depend is determined by means of the theory of algebraic invariants and combinatorial analysis. Formulas are displayed for coefficients for the calculation of () forn5.
Zusammenfassung Wir bestimmen die Anzahl der unabhängigen Invarianten dern×n MatrizenA, B und ihrer Produkte, von denen die Eigenwerte () der MatrixbüschelA+B abhängen, mittels der Theorie der algebraischen Invarianten und mittels kombinatorischer Analyse. Formeln für Koeffizienten zur Berechnung von () werden angegeben fürn5.相似文献
7.
Dr. Richard Koch 《Monatshefte für Mathematik》1977,83(2):133-146
Let ={e(u)|uI} be a one-parameter family of straight lines forming a ruledC
r-2-surface E
n (n2,r1) without singular generatorse(u) (uI). As a synopsis, a generalization and an improvement of various results already known about the strictional properties of ruled surfaces E
n (especially in the casen=3) the author demonstrates a uniform geometrical way of defining and uniquely obtaining thestriction point S(u) and theparameter of distribution d(u) of a generatore(u) under the minimal assumptions thate(u)E
n
(n2) be noncylindrical andr1. Other methods of obtainingS(u) andd(u) are discussed in comparison, and special strictional properties ofskew ruled surfaces E
n are proved.
Herrn Prof. Dr. H. R. Müller zum 65. Geburtstag 相似文献
Herrn Prof. Dr. H. R. Müller zum 65. Geburtstag 相似文献
8.
Dr. Krishna Balasundaram Athreya 《Probability Theory and Related Fields》1969,12(4):320-332
Summary Let X(t)=(X
1
(t), X
2
(t), , X
t
(t)) be a k-type (2k<) continuous time, supercritical, nonsingular, positively regular Markov branching process. Let M(t)=((m
ij
(t))) be the mean matrix where m
ij
(t)=E(X
j
(t)¦X
r
(0)=
ir
for r=1, 2, , k) and write M(t)=exp(At). Let be an eigenvector of A corresponding to an eigenvalue . Assuming second moments this paper studies the limit behavior as t of the stochastic process
. It is shown that i) if 2 Re >1, then · X(t)e{–t¦ converges a.s. and in mean square to a random variable. ii) if 2 Re 1 then [ · X(t)] f(v · X(t)) converges in law to a normal distribution where f(x)=(x)
–1
if 2 Re <1 and f(x)=(x log x)–1 if 2 Re =1, 1 the largest real eigenvalue of A and v the corresponding right eigenvector.Research supported in part under contracts N0014-67-A-0112-0015 and NIH USPHS 10452 at Stanford University. 相似文献
9.
Summary We describe a large class of one-parameter families , {}, , of two-dimensional diffeomorphisms which arestable for <0, exhibit acycle for =0, and thereafter have a bifurcation set of positive but arbitrarily smallrelative measure for in small intervals [0, ]. A main assumption is that the basic sets involved in the cycle havelimit capacities that are not too large.The second author acknowledges hospitality and financial support from IMPA/CNPq during the period this paper was prepared 相似文献
10.
Yimin Xiao 《Journal of Theoretical Probability》1997,10(4):849-866
Let X(t) (tR) be a real-valued centered Gaussian process with stationary increments. We assume that there exist positive constants
0, C
1, and c
2 such that for any tR and hR with |h|0
and for any 0r<min{|t|, 0}
where
is regularly varying at zero of order (0 < < 1). Let be an inverse function of near zero such that (s)=(s) log log(1/s) is increasing near zero. We obtain exact estimates for the weak -variation of X(t) on [0,a]. 相似文献
11.
Rolf Rannacher 《Mathematische Zeitschrift》1976,149(1):69-77
Summary For piecewise linear Ritz approximation of second order elliptic Dirichlet problemsAu=f over domains
n
globalL
error boundsO(h
2|lnh|v) are obtained under the assumptionfL
(). The proof rests on interpolation ofH
2()-functions with second derivatives in the space of John and Nirenberg by piecewise linear splines and a technique of Nitsche [7] using weighted Sobolev norms.
Diese Note wurde verfaßt mit der Unterstützung des Sonderforschungsbereiches 72 der DFG, Bundesrepublik Deutschland 相似文献
Diese Note wurde verfaßt mit der Unterstützung des Sonderforschungsbereiches 72 der DFG, Bundesrepublik Deutschland 相似文献
12.
Xiangsheng Xu 《Applied Mathematics and Optimization》1996,34(3):299-324
A partial regularity theorem is established for a particular class of weak solutions to the systemu/t– div(K(u)u)=(u)¦¦2, div((u))=0 on a bounded domain inR
N
. Under our assumptions, (u) may exhibit exponential decay, and thus the system may be degenerate. Our proof is based upon a blow-up argument.This work was supported in part by NSF Grant DMS9424448. 相似文献
13.
Nathaniel Knox 《Semigroup Forum》1978,16(1):345-354
In this paper the inverse hull of the free semigroup on a non-empty set X is characterized. It is shown that if FO is a certain semilattice and (G,*) is the free group on X, then is isomorphic to a Rees factor semigroup of a subsemigroup of (FO x G, #), where (A,w)#(B,u) = ((A*w B)*w–1, w*u). Several properties of , including Green's relations on are also determined. 相似文献
14.
Mary E. Gbur 《Monatshefte für Mathematik》1976,81(2):95-107
C. Hightower found two infinite sequences of gaps in the Markov spectrum, (
n
,
n
) and (
n
,
n
) with
n
and
n
both Markov elements, converging to
. This paper exhibits Markov elements
n
*
and
n
*
such that, for alln 1, (
n
*
,
n
) and (
n
n
*
) are gaps in the Markov spectrum. Other results include showing that, for alln 1,
n
is completely isolated, while the other endpoints of the gaps are limit points in the Markov spectrum. 相似文献
15.
V. T. Gavrilyuk 《Ukrainian Mathematical Journal》1990,42(6):659-666
Asymptotic estimates, expressed in terms of the value of the modulus of continuity of r-th order (r2) at the point t=/n of a functionf
C
2 or of the (, )-derivative of a functionf
C
B
C, are established for the deviations of continuous periodic functions from their Fourier sums.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 42, No. 6, pp. 747–755, June, 1990. 相似文献
16.
Die Automorphismengruppen hyperelliptischer Kurven 总被引:1,自引:0,他引:1
Let be a hyperelliptic curve over an algebraically closed field of characteristic O and G a group of automorphisms of that contains the canonical involution of . We describe the group-theoretical structure of G by means of the arithmetical structure of the morphism G. 相似文献
17.
A spatially nonhomogeneous random walk t on the grid =m X n is considered. Let t
0 be a random walk homogeneous in time and space, and let t be obtained from it by changing transition probabilities on the set A= X n, || < , so that the walk remains homogeneous only with respect to the subgroup n of the group . It is shown that if >m 2 or the drift is distinct from zero, then the central limit theorem holds for t. 相似文献
18.
A. S. Serdyuk 《Ukrainian Mathematical Journal》2004,56(4):601-613
We establish asymptotically unimprovable interpolation analogs of Lebesgue-type inequalities on the classes of periodic infinitely differentiable functions C
C whose elements can be represented in the form of convolutions with fixed generating kernels. We obtain asymptotic equalities for upper bounds of approximations by interpolation trigonometric polynomials on the classes C
,
and C
H
.Translated from Ukrainskyi Matematychnyi Zhurnal, Vol. 56, No. 4, pp. 495–505, April, 2004. 相似文献
19.
Jacques Simon 《Annali di Matematica Pura ed Applicata》1986,146(1):65-96
Summary A characterization of compact sets in Lp (0, T; B) is given, where 1P and B is a Banach space. For the existence of solutions in nonlinear boundary value problems by the compactness method, the point is to obtain compactness in a space Lp (0,T; B) from estimates with values in some spaces X, Y or B where XBY with compact imbedding XB. Using the present characterization for this kind of situations, sufficient conditions for compactness are given with optimal parameters. As an example, it is proved that if {fn} is bounded in Lq(0,T; B) and in L
loc
1
(0, T; X) and if {fn/t} is bounded in L
loc
1
(0, T; Y) then {fn} is relatively compact in Lp(0,T; B), p相似文献
20.
Shiqi Song 《应用数学学报(英文版)》1993,9(2):115-124
LetX be the solution of the SDE:dX
t = (X
t)dB
t +b(X
t)dt, with andb C
b
(R) such that >0 for some constant , andB a real Brownian motion. Let be the law ofX onE=C([0, 1],R) andk E* – {0}, whereE* is the topological dual space ofE. Consider the classical form:
k
(u, v)=u / kv / kd, whereu andv are smooth functions onE. We prove that, if
k
is closable for anyk in a dense subset ofE* and if the smooth functions are contained in the domain of the generator of the closure of
k
, must be a constant function. 相似文献