arXiv
(422,153 recursos)
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Mostrando recursos 141 - 160 de 66,283
141.
Banach function algebras with dense invertible group - Dales, H. G.; Feinstein, J. F.
In an earlier paper, Dawson and the second author asked whether or not a
Banach function algebra with dense invertible group can have a proper Shilov
boundary. We give an example of a uniform algebra showing that this can happen,
and investigate the properties of such algebras.
142.
The Amalgamated product of free groups and residual solvability - Kahrobaei, Delaram
In this paper we study residual solvability of the amalgamated product of two
finitely generated free groups, in the case of doubles. We find conditions
where this kind of structure is residually solvable, and show that in general
this is not the case. However this kind of structure is always
meta-residually-solvable.
143.
A simple proof of a theorem of Karrass and Solitar - Kahrobaei, Delaram
In this note we give a particularly short and simple proof of the following
theorem of Karrass and Solitar. Let $H$ be a finitely generated subgroup of a
free group $F$ with infinite index $[F:H]$. Then there is a nontrivial normal
subgroup $N$ of $F$ such that $N\cap H = \{1\}$.
144.
The topology of the category of open and closed strings - Baas, Nils A.; Cohen, Ralph L.; Ramirez, Antonio
In this paper we study the topology of the cobordism category of open and
closed strings. This is a 2-category in which the objects are compact
one-manifolds whose boundary components are labeled by an indexing set (the set
of "D-branes"), the 1-morphisms are cobordisms of manifolds with boundary, and
the 2-morphisms are diffeomorphisms of the surface cobordisms. Our methods and
techniques are direct generalizations of those used by U. Tillmann in her study
of the category of closed strings. We input the striking theorem of Madsen and
Weiss regarding the topology of the stable mapping class group to identify the
homotopy type of the geometric realization of the...
145.
Elliptic Genera of Complete Intersections - Ma, Xiaoguang; Zhou, Jian
We propose a new definition of the elliptic genera for complete
intersections, not necessarily nonsingular, in projective spaces. We also prove
they coincide with the expressions obtained from Landau-Ginzburg model by an
elementary argument.
146.
Recurrence relations for the Lerch Phi function and applications - Dalai, Marco
In this paper we present a simple method for deriving recurrence relations
and we apply it to obtain two equations involving the Lerch Phi function and
sums of Bernoulli and Euler polynomials. Connections between these results and
those obtained in a paper of H.M. Srivastava, M.L. Glasser and V. Adamchik are
pointed out, emphasizing the usefulness of this approach with some meaningful
examples.
147.
The polynomial analogue of a theorem of Renyi - Morrison, Kent E.
Renyi's result on the density of integers whose prime factorizations have
excess multiplicity has an analogue for polynomials over a finite field.
148.
Irreducible Complexity in Pure Mathematics - Chaitin, G. J.
By using ideas on complexity and randomness originally suggested by the
mathematician-philosopher Gottfried Leibniz in 1686, the modern theory of
algorithmic information is able to show that there can never be a "theory of
everything" for all of mathematics.
149.
Coincidences of simplex centers and related facial structures - Edmonds, Allan L.; Hajja, Mowaffaq; Martini, Horst
We investigate the geometric properties of simplices in Euclidean
d-dimensional space for which two or more of the analogues of the classical
triangle centers (including the centroid, circumcenter, incenter, orthocenter
or Monge point, and the Fermat-Torricelli point) coincide. We also investigate
the geometric significance of the cevian line segments through a given center
having the same length. We give a unified presentation, including known results
for d=2 and d=3.
150.
Root numbers of curves - Sabitova, M.
We generalize a theorem of D. Rohrlich concerning root numbers of elliptic
curves over the field of rational numbers. Our result applies to curves of all
higher genera over number fields. Namely, under certain conditions which
naturally extend the conditions used by D. Rohrlich, we show that the root
number associated to a smooth projective curve over a number field F and a
complex finite-dimensional irreducible representation of the absolute Galois
group of F with real-valued character is equal to 1. In the case where the
ground field is the field of rational numbers, we show that our result is
consistent with the refined version of the conjecture...
151.
Simple Permutations Mix Even Better - Hoory, Shlomo; Brodsky, Alex
We study the random composition of a small family of O(n^3) simple
permutations on {0,1}^n. Specifically we ask how many randomly selected simple
permutations need be composed to yield a permutation that is close to k-wise
independent. We improve on the results of Gowers 1996 and Hoory, Magen, Myers
and Rackoff 2004, and show that up to a polylogarithmic factor, n^2*k^2
compositions of random permutations from this family suffice. In addition, our
results give an explicit construction of a degree O(n^3) Cayley graph of the
alternating group of 2^n objects with a spectral gap Omega(2^{-n}/n^2), which
is a substantial improvement over previous constructions.
152.
Clifton-Pohl torus and geodesic completeness by a 'complex' point of view - Meneghini, Claudio
We show that a natural complexification and a mild generalization of the idea
of completeness guarantee geodesic completeness of Clifton-Pohl torus; we
explicitely compute all of its geodesics.
153.
Framed quiver moduli, cohomology, and quantum groups - Reineke, Markus
Framed quiver moduli parametrize stable pairs consisting of a quiver
representation and a map to a fixed graded vector space. Geometric properties
and explicit realizations of framed quiver moduli for quivers without oriented
cycles are derived, with emphasis on their cohomology. Their use for quantum
group constructions is discussed.
154.
Jordan algebras, exceptional groups, and higher composition laws - Krutelevich, Sergei
We consider an integral version of the Freudenthal construction relating
Jordan algebras and exceptional algebraic groups. We show how this construction
is related to higher composition laws of M.Bhargava in number theory.
We propose an algorithmic approach to studying orbit spaces of groups
underlying higher composition laws. Using this method we discover two new
examples of spaces sharing similar properties, and indicate several more
examples of spaces where such composition laws may be introduced.
155.
Verma modules and preprojective algebras - Geiss, Christof; Leclerc, Bernard; Schröer, Jan
We give a geometric construction of the Verma modules of a symmetric
Kac-Moody Lie algebra in terms of constructible functions on the varieties of
nilpotent finite-dimensional modules of the corresponding preprojective
algebra.
156.
Continuous Fraisse Conjecture - Beckmann, Arnold; Goldstern, Martin; Preining, Norbert
We investigate the relation of countable closed subsets of the reals with
respect to continuous monotone embeddability; we show that there are exactly
aleph_1 many equivalence classes with respect to this embeddability relation.
This is an extension of Laver's 1971 result, who considered (plain)
embeddability, which yields coarser equivalence classes.
Using this result we show that there are only countably many different Godel
logics.
157.
Variation of parabolic cohomology and Poincare duality - Dettweiler, Michael; Wewers, Stefan
We continue our study of the variation of parabolic cohomology
(math.AG/0310139) and derive an exact formula for the underlying Poincare
duality. As an illustration of our methods, we compute the monodromy of the
Picard-Euler system and its invariant Hermitian form, reproving a classical
theorem of Picard.
158.
The $L^p$ Dirichlet Problem for Elliptic Systems on Lipschitz Domains - Shen, Zhongwei
We develop a new approach to the $L^p$ Dirichlet problem via $L^2$ estimates
and reverse Holder inequalities. We apply this approach to second order
elliptic systems and the polyharmonic equation on a bounded Lipschitz domain
$\Omega$ in $R^n$. For $n\ge 4$ and $2-\epsilon
159.
A note on projective modules over real affine algebras - Keshari, Manoj Kumar
Let A be an affine algebra over the field of real numbers of dimension d. Let
f \in A be an element not belonging to any real maximal ideal of A. Let P be a
projective A-module of rank \geq d-1. Let (a,p) \in A_f \oplus P_f be a
unimodular element. Then the projective A_f module Q=A_f \oplus P_f/(a,p)A_f is
extended from A.
160.
New obstructions to doubly slicing knots - Kim, Taehee
A knot in the 3-sphere is called doubly slice if it is a slice of an
unknotted 2-sphere in the 4-sphere. We give a bi-sequence of new obstructions
for a knot being doubly slice. We construct it following the idea of
Cochran-Orr-Teichner's filtration of the classical knot concordance group. This
yields a bi-filtration of the monoid of knots (under the connected sum
operation) indexed by pairs of half integers. Doubly slice knots lie in the
intersection of this bi-filtration. We construct examples of knots which
illustrate non-triviality of this bi-filtration at all levels. In particular,
these are new examples of algebraically doubly slice knots that are not doubly
slice,...
141.
