This is an announcement for the paper "Parallelogram norm" by Madjid
Mirzavaziri and Mohammad Sal Moslehian.
Abstract: Replacing the triangle inequality by \|x+y\|^2\leq 2(\|x\|^2 +
\|y\|^2) in the definition of norm we obtain the notion of parallelogram
norm. We establish that every parallelogram norm is a norm in the
usual sense.
Archive classification: Functional Analysis
Mathematics Subject Classification: 46B20; 46C05
Remarks: 3 pages
The source file(s), Paral1.tex: 4582 bytes, is(are) stored in gzipped
form as 0503616.gz with size 2kb. The corresponding postcript file has
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Submitted from: msalm(a)math.um.ac.ir
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This is an announcement for the paper "Sampling from large matrices:
an approach through geometric functional analysis" by Mark Rudelson
and Roman Vershynin.
Abstract: We study random submatrices of a large matrix A. We show how to
approximately compute A from its random submatrix. This improves known
algorithms for computing low-rank approximations of large matrices. We
also estimate norms of random submatrices of A. This yields an improved
approximation algorithm for all MAX-2CSP problems (which includes MAX-CUT
and other graph problems). Our results are essentially dimension-free;
the picture is only controlled by the norms of the matrix and not by
its size or rank. We use methods of Probability in Banach spaces, in
particular the law of large numbers for random operators.
Archive classification: Functional Analysis; Numerical Analysis
Mathematics Subject Classification: 15A60, 68W20, 15A18
The source file(s), rv-random-submatrices.tex: 50699 bytes, is(are)
stored in gzipped form as 0503442.gz with size 16kb. The corresponding
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Submitted from: vershynin(a)math.ucdavis.edu
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This is an announcement for the paper "Centroids and comparison of
volumes" by V.Yaskin and M.Yaskina.
Abstract: For $-1<p<1$ we introduce the concept of a polar $p$-centroid
body ${\Gamma^*_p K}$ of a star body $K$. We consider the question of
whether ${\Gamma^*_p K}\subset {\Gamma^*_p L}$ implies $\mathrm{vol}(L)\le
\mathrm{vol}(K).$ Our results extend the studies by Lutwak in the case
$p=1$ and Grinberg, Zhang in the case $p> 1$.
Archive classification: Functional Analysis
Mathematics Subject Classification: 52Axx
Remarks: 18 pages
The source file(s), centr.tex: 51970 bytes, is(are) stored in gzipped
form as 0503290.gz with size 13kb. The corresponding postcript file has
gzipped size 71kb.
Submitted from: yaskinv(a)math.missouri.edu
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This is an announcement for the paper "A solution to the lower dimensional
Busemann-Petty problem in the hyperbolic space" by V.Yaskin.
Abstract: The lower dimensional Busemann-Petty problem asks whether
origin symmetric convex bodies in $\mathbb{R}^n$ with smaller volume
of all $k$-dimensional sections necessarily have smaller volume. As
proved by Bourgain and Zhang, the answer to this question is negative
if $k>3$. The problem is still open for $k=2,3$. In this article we
formulate and completely solve the lower dimensional Busemann-Petty
problem in the hyperbolic space $\mathbb{H}^n$.
Archive classification: Functional Analysis; Metric Geometry
Mathematics Subject Classification: 52A55, 52A20, 46B20
Remarks: 12 pages, 2 figures
The source file(s), LDHBP.tex: 70816 bytes, pic04.eps: 9457 bytes,
pic06.eps: 9542 bytes, is(are) stored in gzipped form as 0503289.tar.gz
with size 25kb. The corresponding postcript file has gzipped size 59kb.
Submitted from: yaskinv(a)math.missouri.edu
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This is an announcement for the paper "On the intrinsic and the spatial
numerical range" by Miguel Martin, Javier Meri and Rafael Paya.
Abstract: For a bounded function $f$ from the unit sphere of a closed
subspace $X$ of a Banach space $Y$, we study when the closed convex
hull of its spatial numerical range $W(f)$ is equal to its intrinsic
numerical range $V(f)$. We show that for every infinite-dimensional
Banach space $X$ there is a superspace $Y$ and a bounded linear operator
$T:X\longrightarrow Y$ such that $\ecc W(T)\neq V(T)$. We also show
that, up to renormig, for every non-reflexive Banach space $Y$, one can
find a closed subspace $X$ and a bounded linear operator $T\in L(X,Y)$
such that $\ecc W(T)\neq V(T)$.
Finally, we introduce a sufficient condition for the closed convex
hull of the spatial numerical range to be equal to the intrinsic numerical
range, which we call the Bishop-Phelps-Bollobas property, and which is
weaker than the uniform smoothness and the finite-dimensionality. We
characterize strong subdifferentiability and uniform smoothness in terms
of this property.
Archive classification: Functional Analysis
Mathematics Subject Classification: 46B20; 47A12
Remarks: 12 pages
The source file(s), MartinMeriPaya.tex: 40725 bytes, is(are) stored in
gzipped form as 0503076.gz with size 13kb. The corresponding postcript
file has gzipped size 70kb.
Submitted from: mmartins(a)ugr.es
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This is an announcement for the paper "Weak OH-type 2 and weak OH-cotype
2 of operator spaces" by Hun Hee Lee.
Abstract: Recently, OH-type and OH-cotype of operator spaces, an operator
space version of type and cotype, were introduced and investigated by the
author. In this paper we define weak OH-type 2 (resp. weak OH-cotype 2) of
operator spaces, which lies strictly between OH-type 2 (resp. OH-cotype 2)
and OH-type $p$ for all $1 \leq p < 2$. (resp. OH-cotype $q$ for all $2<
q <= \infty$) This is an analogue of weak type 2 and weak cotype 2 in
Banach space case, so we develop analogous theory focusing on the local
properties of spaces with such conditions.
Archive classification: Functional Analysis; Operator Algebras
Remarks: 21 pages
The source file(s), WeakOH.tex: 55124 bytes, is(are) stored in gzipped
form as 0502337.gz with size 15kb. The corresponding postcript file has
gzipped size 85kb.
Submitted from: hunmada(a)hanmail.net
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This is an announcement for the paper "Eigenvalues of completely nuclear
maps and completely bounded projection constants" by Hun Hee Lee.
Abstract: We investigate the distribution of eigenvalues of completely
nuclear maps on an operator space. We prove that eigenvalues of
completely nuclear maps are square-summable in general and summable if
the underlying operator space is Hilbertian and homogeneous. Conversely,
if eigenvalues are summable for all completely nuclear maps, then
every finite dimensional subspace of the underlying operator space is
uniformly completely complemented. As an application we consider an
estimate of completely bounded projection constants of $n$-dimensional
operator spaces.
Archive classification: Functional Analysis; Operator Algebras
Remarks: 10 pages
The source file(s), EigenComNuclear.tex: 27465 bytes, is(are) stored in
gzipped form as 0502335.gz with size 9kb. The corresponding postcript
file has gzipped size 55kb.
Submitted from: hunmada(a)hanmail.net
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This is an announcement for the paper "OH-type and OH-cotype of operator
spaces and completely summing maps" by Hun Hee Lee.
Abstract: The definition and basic properties of OH-type and OH-cotype
of operator spaces are given. We prove that every bounded linear map
from C(K) into OH-cotype q (2<= q < infinity) space (including most
of commutative L_q-spaces) for a compact set K satisfies completely
(q,2)-summing property, a noncommutative analogue of absolutely
(q,2)-summing property. At the end of this paper, we observe that
``OH-cotype 2" is equivalent to the previous definition of ``OH-cotype 2"
of G. Pisier.
Archive classification: Functional Analysis; Operator Algebras
Remarks: 17 pages
The source file(s), OH-typecotype.tex: 46265 bytes, is(are) stored in
gzipped form as 0502302.gz with size 13kb. The corresponding postcript
file has gzipped size 80kb.
Submitted from: hunmada(a)hanmail.net
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This is an announcement for the paper "Geometric approach to error
correcting codes and reconstruction of signals" by Mark Rudelson and
Roman Vershynin.
Abstract: We develop an approach through geometric functional analysis to
error correcting codes and to reconstruction of signals from few linear
measurements. An error correcting code encodes an n-letter word x into
an m-letter word y in such a way that x can be decoded correctly when
any r letters of y are corrupted. We prove that most linear orthogonal
transformations Q from R^n into R^m form efficient and robust robust
error correcting codes over reals. The decoder (which corrects the
corrupted components of y) is the metric projection onto the range of Q
in the L_1 norm. An equivalent problem arises in signal processing: how
to reconstruct a signal that belongs to a small class from few linear
measurements? We prove that for most sets of Gaussian measurements,
all signals of small support can be exactly reconstructed by the L_1
norm minimization. This is a substantial improvement of recent results
of Donoho and of Candes and Tao. An equivalent problem in combinatorial
geometry is the existence of a polytope with fixed number of facets and
maximal number of lower-dimensional facets. We prove that most sections
of the cube form such polytopes.
Archive classification: Functional Analysis; Combinatorics
Mathematics Subject Classification: 46B07; 94B75, 68P30, 52B05
Remarks: 17 pages, 3 figures
The source file(s), ecc.tex: 50560 bytes, ecc1.eps: 4526 bytes, ecc2.eps:
17097 bytes, ecc3.eps: 4645 bytes, is(are) stored in gzipped form as
0502299.tar.gz with size 23kb. The corresponding postcript file has
gzipped size 84kb.
Submitted from: vershynin(a)math.ucdavis.edu
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