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1.
Richard Urzúa Luz 《Bulletin of the Brazilian Mathematical Society》2003,34(2):287-302
Let a minimal affine
-action on the torus
T
q
,
p 2 and
q 1. The cohomology of
(see definition below) depends on both the algebraic properties
of the induced action on H
1(T
q
,
) and the arithmetical
properties of the translation cocycle. We give a Diophantine
condition that characterizes those affine actions whose first
cohomology group is finite dimensional. In this case it is
necessarily isomorphic to
. Thus the
-action
F
obtained by suspension of is parameter
rigid, i.e., any other
-action with the same
orbit foliation is smoothly conjugate to a reparametrization of
F
by
an automorphism of
.*Partially supported by CNPq fellowship by Fondecyt Grant
1000047 and DGICT-UCN and fundación Andes, Chile. 相似文献
2.
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
3.
Amnon Neeman 《K-Theory》2001,22(1-2):1-144
Let
be a triangulated category, and assume it admits at least one model. In this article, we define a K-theory for
. The main theorem is that, given any bounded i-structure on
, the K-theory of the heart agrees with the K-theory of
. An immediate consequence tells us that, if two Abelian categories occur as hearts of a triangulated category for two different t-structures, then their K-theories must be isomorphic.The proof was also sketched in previous articles in this series. The virtue of this article is in the careful detail in which it is written down. 相似文献
4.
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
5.
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
6.
7.
Here we study complete rotation hypersurfaces with constant k-th mean curvature Hk in
even and 2 < k < n. We prove the existence of a constant
such that there are no such hypersurfaces for
. We have only one compact hypersurface of this kind with
. For each
there is a corresponding family of complete immersed rotation hypersurfaces, each family containing two isoparametric hypersurfaces.
For Hk ≥ 0, there is also such a family, now containing only one isoparametric hypersurface. Finally, we prove the existence of
compact hypersurfaces with arbitrarily large Hk , neither isometric to a sphere nor to a product of spheres.
*Bull. Braz. Math. Soc. 30 (2), 1999, 139–161.
**Partially supported by FUNCAP, Brazil.
***Partially supported by CNPq, Brazil and DGAPA-UNAM, México. 相似文献
9.
In this paper, we continue our investigation on “Extremal problems under dimension constraints” introduced [1]. The general problem we deal with in this paper can be formulated as follows. Let
be an affine plane of dimension k in
. Given
determine or estimate
.Here we consider and solve the problem in the special case where
is a hyperplane in
and the “forbidden set”
. The same problem is considered for the case, where
is a hyperplane passing through the origin, which surprisingly turns out to be more difficult. For this case we have only partial results.AMS Classification: 05C35, 05B30, 52C99 相似文献
10.
Let
be realhomogeneous functions in
ofdegree
and let bethe Borel measure on
given by
where dx denotes theLebesgue measure on
and > 0. Let T
be the convolution operator
and let
Assume that, for x 0, the followingtwo conditions hold:
vanishes only at h = 0 and
. In this paper we show that if
then E
is the empty set and if
then E
is the closed segment withendpoints
and
. Also, we give some examples. 相似文献
11.
In this paper we fix a set * of positive elements of the free group
(e. g. the set of finite words occurring in a Markov subshift) as well as n partial isometries on a Hilbert space H. Based on these we define a map S :
which we prove to be a partial representation of
on H under certain conditions studied by Matsumoto.*Supported by Capes. 相似文献
12.
Let C be a set of objects in a triangulated compactly generated category
We denote by
the smallest suspended subcategory closed under coproducts which contains C (the smallest cosuspended subcategory closed under products which contains
C). We prove that if C is a set of compacts objects then
is a t-structure in
where TC
I is the dual of C with respect to an injective cogenerator
I in the category Mod
C. Moreover, we show that:
C is a tilting set if and only if
And, this is equivalent to TCI is a cotilting object in
Received: 28 March 2003 相似文献
13.
Given a surface S, a map N from S to
and a conformal structure on S, we solve the problem of the existence and uniqueness of an immersion
with a Gauss map N such that the conformal structure on S is the induced by the second fundamental form. 相似文献
14.
For suitable positive integers n and k let m(n, k) denote the maximum number of edges in a graph of order n which has a unique k-factor. In 1964, Hetyei and in 1984, Hendry proved
for even n and
, respectively. Recently, Johann confirmed the following conjectures of Hendry:
for
and kn even and
for n = 2kq, where q is a positive integer. In this paper we prove
for
and kn even, and we determine m(n, 3). 相似文献
15.
Hans Cuypers 《Designs, Codes and Cryptography》2005,34(2-3):333-337
In this note we prove the uniqueness of the tight spherical 7-design in
consisting of 4600 vectors and with automorphism group 2 × Co2 as well as the uniqueness of the tight spherical 5-design in
on 112 vectors and with automorphism group 2 × Sp6(2).To the memory of Jaap Seidel 相似文献
16.
George M. Bergman 《Algebra Universalis》2005,53(2-3):357-395
Properties of several sorts of lattices of convex subsets of
are examined. The lattice of convex sets containing the origin turns out, for n > 1, to satisfy a set of identities strictly between those of the lattice of all convex subsets of
and the lattice of all convex subsets of
The lattices of arbitrary, of open bounded, and of compact convex sets in
all satisfy the same identities, but the last of these is join-semidistributive, while for n > 1 the first two are not. The lattice of relatively convex subsets of a fixed set
satisfies some, but in general not all of the identities of the lattice of “genuine” convex subsets of
To the memory of Ivan RivalReceived April 22, 2003; accepted in final form February 16, 2005.This revised version was published online in August 2005 with a corrected cover date. 相似文献
17.
Igor Frenkel Mikhail Khovanov Catharina Stroppel 《Selecta Mathematica, New Series》2006,12(3-4):379-431
The purpose of this paper is to study categorifications of tensor products of finite-dimensional modules for the quantum group
for
. The main categorification is obtained using certain Harish-Chandra bimodules for the complex Lie algebra
. For the special case of simple modules we naturally deduce a categorification via modules over the cohomology ring of certain
flag varieties. Further geometric categorifications and the relation to Steinberg varieties are discussed.We also give a categorical
version of the quantised Schur–Weyl duality and an interpretation of the (dual) canonical bases and the (dual) standard bases
in terms of projective, tilting, standard and simple Harish-Chandra bimodules. 相似文献
18.
The generating line of the first single shift plane (cf. [11, p. 435]) is a 2-surface of
4 which we call the the affine part
of Knarr's surface. We compute all affinities leaving
invariant. After embedding
4 into PG(4,
) we calculate the uniquely determined projective closure
Kn
of
. Using a suitable projection we transform questions on Knarr's surface to questions on Cayley's surface in PG(3,
). In this way we determine all planes carrying 1-dimensional algebraic varieties of
Kn
. We exhibit all automorphic collineations of
Kn
. 相似文献
19.
Let F(k) denote the k-th
Fibonacci number in the Fibonacci sequence
F(0) := 0, F(1) := 1,..., F(k+1) := F(k-1)+F(k).
Motivated by proposals regarding putative mechanisms
that may be responsible for producing those often observed long repetitive patterns in
genomic DNA, we study in this note the Fibonacci-Cayley index
fcx of positive integers x, i.e.,
the largest integer
for which positive integers a, b
with x = aF(k-1)+bF(k)
exist and show that
holds for the arithmetic mean
of the indices of the smallest and the largest Fibonacci numbers occurring in the Zeckendorf
decomposition
AMS Subject Classification: 11B39, 11A99, 92D20. 相似文献
20.
Violeta Petkova 《Archiv der Mathematik》2005,84(4):311-324
Let
be a weighted space with weight . In this paper we show that for every Wiener-Hopf operator T on
and for every a I, there exists a function
such that
for all
Here (g)a denotes the function x g(x)eax for
and
where R+ is the spectral radius of the shift S : f(x) f(x–1) on
while
is the spectral radius of the backward shift S–1 : f(x) (P+f)(x+1) on
Moreover, there exists a constant C, depending on , such that
for every a I. If R– < R+, we prove that there exists a bounded holomorphic function v on
such that for
the function va is the restriction of v on the line
Received: 18 May 2004 相似文献