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1.
We assume that in a linear space
there is a
non-empty set M of points with the property that every plane
containing a point of M is a projective plane. In
section 3 an example is given that in general
is not a
projective space. But if M can be completed by two
points to a generating set of P, then
is a projective space. 相似文献
2.
In this work we determine the group of modular automorphisms of the
Drinfeld modular curve
for any nonconstant polynomial
.Received: 19 September 2002 相似文献
4.
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
5.
Summary.
We study certain functional equations derived from the
definition of a Jordan *-derivation pair.
More precisely, if A is a complex
*-algebra and M is a
bimodule over A, having the structure of a complex vector space
compatible with the structure of A,
such that
implies
m = 0 and
implies m
= 0 and
if
are unknown additive mappings satisfying
then E and
F can be represented by double centralizers. The
obtained result implies that one of the equations in the
definition of a Jordan *-derivation pair is redundant.
Furthermore, a remark on the extension of this result to unknown
additive mappings
such that
is given in a special case. 相似文献
6.
Consider the Schrödinger operator
with a complex-valued
potential v of period
Let
and
be the eigenvalues of L that are close to
respectively, with periodic (for n even),
antiperiodic (for n odd), and Dirichelet
boundary conditions on [0,1], and let
be the diameter of the spectral
triangle with vertices
We prove the following statement: If
then v(x) is a Gevrey function, and moreover
相似文献
7.
In this paper we show that, given a complete lattice
, the following three
lattices are the same: (1) the lattice of closure relations on
, (2) the lattice of meet-closed subsets of
, and (3) the lattice of complete join congruence relations on
. 相似文献
8.
9.
We study the application,
, where
is the
supremum of positive s such that the problem
admits a solution. Where B 1 is the unit ball in
We show that
is a decreasing function, with
where
is the unique solution of the
problem
.
We also give the explicit solutions of the problem
, when
and show that
. We show that the problem
doesnt admit a solution.
In the end, we give a numerical approximation of
, when
. 相似文献
10.
Let
be the set of all coloured permutations on the symbols 1, 2, . . . , n
with colours 1, 2, . . . , r, which is the analogous of the
symmetric group when r = 1, and the hyperoctahedral
group when r = 2. Let
be a subset of d colours; we define
to be the set of all coloured permutations
.
We prove that the number of
-avoiding coloured permutations in
.
We then prove that for any
,
the number of coloured permutations in
which avoid all patterns in
except for and contain exactly once equals
.
Finally, for any
,
this number equals
.
These results generalize recent results due to Mansour, Mansour and West, and Simion.AMS Subject Classification: 05A05, 05A15. 相似文献
11.
Let
be a family of holomorphic functions in the unit disk
,
which are also holomorphic in a parameter
. We express
cyclicity (=generalized multiplicity) of a zero of
at
via
some algebraic characteristics of the ideal generated by the Taylor
coefficients of
. As an example we estimate the cyclicity of the
family of generalized exponential polynomials. 相似文献
12.
For a class of stable planes we define a notion of isotopy equivalence with
respect to that class and prove that any two planes of a certain class of
-planes comprising all affine
-planes are isotopy equivalent. Furthermore we obtain that all affine
-planes are isotopy equivalent in the class of affine
-planes. Finally we give an example which shows that this approach cannot be easily generalized
to 2-dimensional projective planes, and we outline a different way for a
possible generalization.Received: 27 April 2001 相似文献
13.
We prove that a finite group G is
-constrained if and only if it contains a nilpotent subgroup
I satisfying
for all
.Received: 22 July 2002 相似文献
15.
In this paper the set of minimal periods of periodic points of
1-norm nonexpansive maps
is studied. This set is denoted by R(n). The main goal is to
present a characterization of R(n) by arithmetical and
combinatorial constraints. More precisely, it is shown that
, where
denotes the set of periods of
restricted admissible arrays on 2n
symbols. The important point of this equality is that
is determined by
arithmetical and combinatorial constraints only, and that it can
be computed in finite time. By using this equality the set R(n)
is computed for
. Furthermore it is shown that the largest element
of
R(n) satisfies:
相似文献
16.
In this paper we shall consider the critical elliptic
equation
where
and a(x)
is a real continuous, non
negative function, not identically zero. By using a local Pohozaev
identity, we show that problem (0.1) does not admit a
family of solutions
which blows-up and concentrates as
at some zero point x0 of a(x)
if the order of flatness of the function a(x) at x0 is
相似文献
17.
V. Yu. Popov 《Algebra and Logic》2001,40(1):55-66
It is proved that there exists an infinite sequence of finitely based semigroup varieties
such that, for all i, an equational theory for
and for the class
of all finite semigroups in
is undecidable while an equational theory for
and for the class
of all finite semigroups in
is decidable. An infinite sequence of finitely based semigroup varieties
is constructed so that, for all i, an equational theory for
and for the class
of all finite semigroups in
is decidable whicle an equational theory for
and for the class
of all finite semigroups in
is not. 相似文献
18.
Maribel Loaiza 《Integral Equations and Operator Theory》2005,51(1):141-153
Let
and
be a finite collection of smooth curves in D. Given k points
consider the family
of all bounded and continuous functions on
with finite limits at
and radial limits at zk. We study the Toeplitz operator algebra
corresponding to Mr and we prove that its Calkin algebra is isomorphic to the algebra of all continuous functions on some compact set. This fact implies that the commutator of two Toeplitz operators with this kind of symbols is compact. We also prove that the semi-commutator of such Toeplitz operators is not compact, in general. 相似文献
19.
Let
be a C*-algebra and X a Hilbert C*
-module. If
is a projection, let
be the p-sphere of X. For φ a state of
with support p in
and
consider the modular vector state φx of
given by
The spheres
provide fibrations
and
These fibrations enable us to examine the homotopy type of the sets of modular vector states, and relate it to the homotopy type of unitary groups and spaces of projections. We regard modular vector states as generalizations of pure states to the context of Hilbert C*-modules, and the above fibrations as generalizations of the projective fibration of a Hilbert space. 相似文献
20.
We consider the three-dimensional Schrödinger operators
and
where
, A is a magnetic potential generating a constant magnetic
field of strength
, and
where
decays fast enough at infinity. Then, A. Pushnitskis representation of the spectral shift function (SSF)
for the pair of operators
is well defined for energies
We study the behaviour of the associated representative of the equivalence class
determined by the SSF, in a neighbourhood of the Landau levels
Reducing our analysis to the study of the eigenvalue asymptotics for a family of
compact operators of Toeplitz type, we establish a relation between the type of the
singularities of the SSF at the Landau levels and the decay rate of V at infinity.
Communicated by Bernard HelfferSubmitted 23/09/03, accepted 15/01/04 相似文献