共查询到20条相似文献,搜索用时 78 毫秒
1.
Jelena V. Manojlović 《Czechoslovak Mathematical Journal》2005,55(1):41-60
New oscillation criteria are given for the second order sublinear differential equation
where a C
1 ([t
0, )) is a nonnegative function, , f C() with (x) 0, xf(x) / (x) > 0 for x 0, , f have continuous derivative on \ {0} with [f(x) / #x03C8;(x)] 0 for x 0 and q C([t
0, )) has no restriction on its sign. This oscillation criteria involve integral averages of the coefficients q and a and extend known oscillation criteria for the equation x (t) + q(t)x(t) = 0. 相似文献
2.
We establish a criterion for the existence of a solution of the interpolation problem f(
n
) = b
n in the class of functions f analytic in the unit disk and satisfying the relation
where : [1; +) (0; +) is an increasing function such that the function ln(t) is convex with respect to lnt on the interval [1; +) and lnt = o(ln(t)), t . 相似文献
3.
M. P. Moklyachuk 《Ukrainian Mathematical Journal》1993,45(3):414-423
We study the problem of optimal linear estimation of the transformation
of a stationary random process (t) with values in a Hilbert space by observations of the process (t) + (t) fort0. We obtain relations for computing the error and the spectral characteristic of the optimal linear estimate of the transformationA for given spectral densities of the processes (t) and (t). The minimax spectral characteristics and the least favorable spectral densities are obtained for various classes of densities.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 45, No. 3, pp. 389–397, March, 1993. 相似文献
4.
Michel Weber 《Journal of Theoretical Probability》1996,9(1):105-112
Let (Y,,,T) be an ergodic dynamical system. LetA be an nonempty subset ofL
2() such that
, whereA=sup{||sȒt||2
,s, tA} andN(A, u) is the smallest number ofL
2()-open balls of radiusu, centered inA, enough to coverA. Let
. We prove as a consequence of a more general result, thatC(A) is aGB subset ofL
2(). 相似文献
5.
V. L. Sharan 《Journal of Mathematical Sciences》2001,107(1):3601-3603
A new criterion of solvability of the interpolation problem f(
n
)=bn in the class of functions f, analytic in the right half-plane
and such that there exists c
1(0;+) such that |f(z)|c
1exp((c1|z|)) for all z
, where is a positive increasing continuous differentiable function on [0;+), for which (t)+ as t+ and there exists c
2(0;+) such that
for all t 1 is described. 相似文献
6.
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
7.
Let {\bold x}[] be a stationary Gaussian process with zero mean and spectral density f, let
be the -algebra induced by the random variables {\bold x}[], D(R1), and let
t, t > 0, be the -algebra induced by the random variables x[],supp [-t,t]. Denote by
(f) the Gaussian measure on
generated by {\bold x}. Let
t(f) be the restriction of
(f) to
t. Let f and g be nonnegative functions such that the measures
t(f) and
t(g) are absolutely continuous. Put
For a fixed g(u) and for f(u)= ft(u) close to g(u) in some sense, the asymptotic normality of
t(f,g) is proved under some regularity conditions. Bibliography: 14 titles. 相似文献
8.
Lian-Xi Ku 《Southeast Asian Bulletin of Mathematics》2000,24(3):375-382
In this note, we prove that, for Robins boundary value problem, a unique solution exists if fx(t, x, x), fx(t, x, x), (t), and (t) are continuous, and fx -(t), fx -(t), 4(t) 2 + 2(t) ++ 2(t), and 4(t) 2 + 2(t) + 2(t).AMS Subject Classification (2000) 34B15 相似文献
9.
Let M
f(r) and f(r) be, respectively, the maximum of the modulus and the maximum term of an entire function f and let be a continuously differentiable function convex on (–, +) and such that x = o((x)) as x +. We establish that, in order that the equality
be true for any entire function f, it is necessary and sufficient that ln (x) = o((x)) as x +. 相似文献
10.
Dr. Karl Umgeher 《Monatshefte für Mathematik》1976,81(4):311-314
We consider the set of regular functions
. We construct a Borel measure and a class of outer measures
h
onH. With these and
h
we show that: (HS)=0 and
h
(HS)=0, (S is the set of normed univalent functions). From
h
(HS)=0 follows—forh=t
—that the Hausdorff—Billingsley-dimension ofHS is zero. 相似文献
11.
We study the existence of positive solutions of the nonlinear elliptic problem
in D with u=0 on D, where and are two Randon's measures belonging to a Kato subclass and D is an unbounded smouth domain in
d(d3). When g is superlinear at 0 and 0f(t)t for t(0,b), then probabilistic methods and fixed point argument are used to prove the existence of infinitely many bounded continuous solutions of this problem. 相似文献
12.
Bolesław Gaweł 《Aequationes Mathematicae》1996,52(1):55-71
Summary In the paper we consider, from a topological point of view, the set of all continuous functionsf:I I for which the unique continuous solution:I – [0, ) of(f(x)) (x, (x)) and(x, (x)) (f(x)) (x, (x)), respectively, is the zero function. We obtain also some corollaries on the qualitative theory of the functional equation(f(x)) = g(x, (x)).
No assumption on the iterative behaviour off is imposed. 相似文献
13.
G. F. Webb 《Annali di Matematica Pura ed Applicata》1981,129(1):43-55
Summary
This paper treats the nonlinear age-dependent population problem (1)(0,a)=(a), a I; (2)(t, 0)=F((t, ·)), t0; (3)
,t0,where I is the age range of the population, (t, ·) is the unknown age density at time t, is the known initial age distribution, and the functionals F and G are nonlinear. The problems of existence, uniqueness, continuous dependence upon initial values, and the positivity of solutions are investigated using the method of nonlinear semigroups.Supported in part by the National Science Foundation Grant NSF 75-06332A01. 相似文献
14.
Given f L
loc
1
(R
+), we define
Our permanent assumption is that (t) A as t , where A is a finite number.First, we consider real-valued functions, and prove that s(t) A as t if and only if two one-sided Tauberian conditions are satisfied. In particular, these two conditions are satisfied if s(t) is slowly decreasing (or increasing) in the sense of R. Schmidt; in particular, if f(x) obeys a Landau type one-sided Tauberian condition.Second, we extend these results for complex-valued functions by giving a two-sided Tauberian condition, being necessary and sufficient in order that (t) A imply s(t) A as t . In particular, this condition is satisfied if s(t) is slowly oscillating; in particular if f(x) obeys a Landau type two-sided Tauberian condition. 相似文献
15.
Let
be a real separable Banach space and {X, X
n, m; (n, m) N
2} B-valued i.i.d. random variables. Set
. In this paper, the compact law of the iterated logarithm, CLIL(D), for B-valued random variables with two-dimensional indices ranging over a subset D of N
2 is studied. There is a gap between the moment conditions for CLIL(N
1) and those for CLIL(N
2). The main result of this paper fills this gap by presenting necessary and sufficient conditions for the sequence
to be almost surely conditionally compact in B, where, for 0, 1 r 2, N
r
(, ) = {(n, m) N
2; n
m n
exp{(log n)
r–1 (n)}} and (·) is any positive, continuous, nondecreasing function such that (t)/(log log t) is eventually decreasing as t , for some > 0. 相似文献
16.
Let (K(s,t), 0s1, t1) be a Kiefer process, i.e., a continuous two-parameter centered Gaussian process indexed by [0,1]×+ whose covariance function is given by
(K(s1,t1) K(s2,t2))=(s1s2-s1s2)t1t2, 0s1, s21, t1, t2 0. For each t>0, the process K(·,t) is a Brownian bridge on the scale of
. Let M
1
*
(t) M
2
*
(t) M
j
*
(t) 0 be the ranked excursion heights of K(,t). In this paper, we study the path properties of the process tM
j
*
(t). Two laws of the iterated logarithm are established to describe the asymptotic behaviors of M
j
*
(t) as t goes to infinity. 相似文献
17.
Terence Chan 《Journal of Theoretical Probability》1995,8(3):643-667
For 0<<1, let
. The questions addressed in this paper are motivated by a result due to Strassen: almost surely, lim sup
t
U
((t))=1–exp{–4(–1)–1}. We show that Strassen's result is closely related to a large deviations principle for the family of random variablesU
(t), t>0. Also, when =1,U
(t)0 almost surely and we obtain some bounds on the rate of convergence. Finally, we prove an analogous limit theorem for discounted averages of the form
as 0, whereD is a suitable discount function. These results also hold for symmetric random walks. 相似文献
18.
In this note we consider the Gross-Pitaevskii equation i
t
++(1–2)=0, where is a complex-valued function defined on N×, and study the following 2-parameters family of solitary waves: (x, t)=e
it
v(x
1–ct, x), where
and x denotes the vector of the last N–1 variables in
N
. We prove that every distribution solution , of the considered form, satisfies the following universal (and sharp) L
-bound:
This bound has two consequences. The first one is that is smooth and the second one is that a solution 0 exists, if and only if
. We also prove a non-existence result for some solitary waves having finite energy. Some more general nonlinear Schrödinger equations are considered in the third and last section. The proof of our theorems is based on previous results of the author ([7]) concerning the Ginzburg-Landau system of equations in
N
.Received May 31, 2002
Published online February 7, 2003 相似文献
19.
Manabu Naito 《Czechoslovak Mathematical Journal》1998,48(3):419-432
The neutral differential equation
is considered under the following conditions: n 2, > 0, = ±1, F(t, u) is nonnegative on [t
0, ) × (0, ) and is nondecreasing in u (0, infin;), and lim g(t) = as t . It is shown that equation (1.1) has a solution x(t) such that
0}}{\text{.}} \hfill \\ \end{gathered} $$
" align="middle" border="0">
Here, k is an integer with 0 k n–1. To prove the existence of a solution x(t) satisfying (1.2), the Schauder-Tychonoff fixed point theorem is used. 相似文献
20.
D. O'Regan 《Periodica Mathematica Hungarica》1994,28(2):151-171
This paper is devoted to the problem of existence of solutions to the nonlinear singular two point boundary value problem
, withy satisfying either mixed boundary datay(1)=Limy0+p(t)y(t)=0 or dirichlet boundary datay(0)=y(1)=0. Throughout our nonlinear termqf is allowed to be singular att=0,t=1,y=0 and/orpy=0. 相似文献