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1.
Summary.
Let
We say that
preserves the distance d 0 if
for each
implies
Let A
n
denote the set of all positive numbers
d such that any map
that preserves unit distance preserves also distance
d.
Let D
n
denote the set of all positive numbers
d with the property: if
and
then there exists a finite set
S
xy
with
such that any map
that preserves unit distance preserves also the distance between
x and y.
Obviously,
We prove:
(1)
(2)
for n 2
D
n
is a
dense subset of
(2) implies that each mapping
f
from
to
(n 2)
preserving unit distance preserves all distances,
if f is continuous with respect to the product topologies
on
and
相似文献
2.
We present a (320, 88, 24)-difference set in
, the existence of which was previously open. This new difference set improves a theorem of Davis-Jedwab with the removal of the exceptional case. It also enables us to state a theorem of Schmidt on Davis-Jedwab difference sets more neatly. 相似文献
3.
J. E. Marcos 《Czechoslovak Mathematical Journal》2003,53(3):689-706
We define various ring sequential convergences on
and
. We describe their properties and properties of their convergence completions. In particular, we define a convergence
on
by means of a nonprincipal ultrafilter on the positive prime numbers such that the underlying set of the completion is the ultraproduct of the prime finite fields
Further, we show that
is sequentially precompact but fails to be strongly sequentially precompact; this solves a problem posed by D. Dikranjan. 相似文献
4.
W. Hazod 《Probability Theory and Related Fields》1971,20(4):259-270
Ohne ZusammenfassungBezeichnungen und Symbole
G
lokalkompakte topologische Gruppe
-
M(G)/R(G)/P(G)/
regulÄre komplexe/reelle/positive Ma\e/
-
Q(G)/W(G)
Ma\e mit · l/Wahrscheinlichkeitsma\e
-
x
Punktma\:
x(f)=f(x)
-
v
Faltung,
— Bekanntlich bildet M(G) bezüglich der Faltung eine Banachalgebra;
-
Involution in M(G),
, wobei — die Komplexkonjugierte bezeichnet
- ×
diskreter Anteil eines Ma\es,
-
T
gm
Faltungsoperator auf L
2 (G) (bezüglich des linken Haarschen Ma\es),
f.ü.
-
p(·)/q(·)/u(·)
- exp(·.)
Exponentialfunktion, exp
- normal/unitÄr/symmetrisch/positiv definit
bezeichnet man ein Ma\ , wenn der Faltungsoperator T
diese Eigenschaft besitzt
- invertierbar
hei\t
M(G), wenn ein vM(G) existiert, so da\ v = v=
e
-
1/n
n-te Wurzel von
1
hei\t wenn(
1/n)n=
1
-
1 hei\t unendlich teilbar
wenn zu jedem natürlichen n eine n-te Wurzel
1/n von existiert
-
N
Menge der natürlichen Zahlen 相似文献
5.
A. A. Rakhimov 《Journal of Mathematical Sciences》2001,107(4):4073-4082
We consider *-automorphisms and *-antiautomorphisms of real and complex factors. We establish both the uniqueness of the class of *-automorphisms (with
) of a real injective
factor and the uniqueness of the class of *-antiautomorphisms (with
) of a complex injective
factor. It is well known that, for complex factors, the notions of hyperfiniteness and injectivity are equivalent. Here we prove that, for real factors, the two notions are no longer equivalent. Bibliography: 15 titles. 相似文献
6.
V. É. Geit 《Mathematical Notes》1973,13(2):101-106
We find the necessary and sufficient conditions for the imbeddings
in terms of the majorants and (R=L2,C2;l>k).Translated from Matematicheskie Zametki, Vol. 13, No. 2, pp. 169–178, February, 1973. 相似文献
7.
LetF be an algebraic number field and F such thatx
m– is irreducible, wherem is an integer. Let
be a prime ideal inF with
. The prime decomposition of
in
is explicitly obtained in the following cases. Case 1:
, (a,m) = 1 (where
means
, 0
). Case 2:m lt, wherel is a prime andl 0
. Case 3:m 0
and every prime that dividesm also dividespf–1. It is not assumed that thev
th roots of unity are inF for anyv 2. 相似文献
8.
We propose new formulas for singular vectors in Verma modules over the affine Lie superalgebra
. We analyze the coexistence of singular vectors of different types and identify the twisted modules arising as submodules and quotient modules of
Verma modules. We show that with the twists (spectral flow transformations) properly taken into account, a resolution of irreducible representations can be constructed consisting of only the
modules. 相似文献
9.
This paper is concerned with the problem of absolute stability for a control system with several executive elements. Necessary and sufficient conditions are obtained for the existence of Liapunov function of Lur'e form with negative semi-definite derivative (i.e.
). 相似文献
10.
This is a follow-up of a paper of Bourgain, Brezis and Mironescu [2]. We study how the existence of the limit
for
continuous and
converging to
, is related to the weak regularity of
. This approach gives an alternative way of defining the Sobolev spaces W
1,p
. We also briefly discuss the
-convergence of (1) with respect to the
-topology.Received: 12 November 2002, Accepted: 7 January 2003, Published online: 22 September 2003Mathematics Subject Classification (2000):
46E35, 49J45Augusto C. Ponce: ponce@ann.jussieu.fr 相似文献
11.
P. G. Grinevich 《Theoretical and Mathematical Physics》1994,99(2):599-605
The direct and the inverse scattering problems for the heat-conductivity operator
are studied for the following class of potentials:u(x,y)=u
o
(x,y)+u
1(x,y), whereu
o
(x,y) is a nonsingular real finite-gap potential andu
1(x,y) decays sufficiently fast asx
2+y2. We show that the scattering data for such potentials is the
data on the Riemann surface corresponding to the potentialu
o
(x,y). The scattering data corresponding to real potentials is characterized and it is proved that the inverse problem corresponding to such data has a unique nonsingular solution without the small norm assumption. Analogs of these results for the fixed negative energy scattering problem for the two-dimensional time-independent Schrödinger operator
are obtained.L. D. Landau Institute for Theoretical Physics, Kosygina 2, GSP-1, Moscow 177940, Russia. E-mail: pgg@cpd.landau.free.net. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 99, No. 2, pp. 300–308, May, 1994. 相似文献
12.
Necessary and sufficient conditions for an orthogonal series to be the Fourier series of a function in the space
,
, are obtained. In the special case of regular summation methods we recover the classical results of Orlicz and Lomnicki. 相似文献
13.
I. V. Sokolenko 《Ukrainian Mathematical Journal》2004,56(5):799-816
We obtain asymptotic formulas for the deviations of Fourier operators on the classes of continuous functions
and
in the uniform metric. We also establish asymptotic laws of decrease of functionals characterizing the problem of the simultaneous approximation of
-integrals of continuous functions by Fourier operators in the uniform metric.Translated from Ukrainskyi Matematychnyi Zhurnal, Vol. 56, No. 5, pp. 663–676, May, 2004. 相似文献
14.
Giuseppe Zampieri 《Compositio Mathematica》2000,121(2):155-161
For a domain of
we introduce a fairly general and intrinsic condition of weak q-pseudoconvexity, and prove, in Theorem 4, solvability of the
-complex for forms with
-coefficients in degree
. All domains whose boundary have a constant number of negative Levi eigenvalues are easily recognized to fulfill our condition of q-pseudoconvexity; thus we regain the result of Michel (with a simplified proof). Our method deeply relies on the L
2-estimates by Hörmander (with some variants). The main point of our proof is that our estimates (both in weightened-L
2 and in Sobolev norms) are sufficiently accurate to permit us to exploit the technique by Dufresnoy for regularity up to the boundary. 相似文献
15.
Makhlouf Derridj 《Inventiones Mathematicae》1991,104(1):631-642
Résume Nous étudions des estimations précises pour
sur des hypersurfaces dont la matrice de Levi dans une base a une certaine forme. En particulier, nous donnons, par la méthode de microlocalisation, une démonstration très simple des estimations dites maximales lorsque les valeurs propres sont comparables. Nous obtenons en fait une précision supplémentaire (inégalité 3.17) qui permet de considérer des cas plus généraux. Finalement, de telles estimations, on déduit des estimations sous elliptiques optimales pour
.
Oblatum 3-IX-1990 相似文献
Summary We study precise estimates for on hypersurfaces the Levi matrix of which has certain form. In particular, we give and simple proof of the so-called maximal estimates, using the microlocal analysis. In fact, we obtain a refined version (inequality 3.17), which permits the study of more general cases. Finally, from such estimates, we deduce optimal subelliptic estimates for .
Oblatum 3-IX-1990 相似文献
16.
We study two questions posed by Johnson, Lindenstrauss, Preiss, and
Schechtman, concerning the structure of level sets of uniform and Lipschitz
quotient mappings from
. We show that if
, is a uniform quotient mapping then for every
has
a bounded number of components, each component of
separates
and the upper bound of the number of components depends
only on
and the moduli of co-uniform and uniform continuity of
.Next we prove that all level sets of any co-Lipschitz uniformly
continuous mapping from
to
are locally connected, and we show
that for every pair of a constant
and a function
with
, there exists a natural number
, so that
for every co-Lipschitz uniformly continuous map
with a
co-Lipschitz constant
and a modulus of uniform continuity
, there
exists a natural number
and a finite set
with
card
so that for all
has exactly
components,
has exactly
components and
each component of
is homeomorphic with the real line and
separates the plane into exactly 2 components. The number and form
of components of
for
are also described - they have a
finite tree structure. 相似文献
17.
Takuya Hara 《Integral Equations and Operator Theory》1992,15(4):551-567
Let
be a Hilbert space. A continuous positive operatorT on
uniquely determines a Hilbert space
which is continuously imbedded in
and for which
with the canonical imbedding
. A Kreîn space version of this result, however, is not valid in general. This paper provides a necessary and sufficient condition for that a continuous selfadjoint operatorT uniquely determines a Kreîn space (
) which is continuously imbedded in
and for which
with the canonical imbedding
. 相似文献
18.
We derive bosonic-type formulas for the characters of
2 coinvariants. 相似文献
19.
Let
be a sequence of complex numbers such that
as
. For
close to the imaginary axis, upper bounds of the indicator of a nonzero entire function of exponential type with minimal growth vanishing on
is obtained. These bounds give sufficient conditions for the system of exponents
to be incomplete in an unbounded domain in
. 相似文献
20.
In this note we prove that the Laplacian with generalized Wentzell boundary
conditions on an open bounded regular domain in
defined by
generates an analytic semigroup of angle
on
for every > 0 and
(for the definition of
cf. (1.3)).Received: 13 July 2002 相似文献