48,320 research outputs found
Lifting units modulo exchange ideals and C*-algebras with real rank zero
Given a unital ring and a two-sided ideal of , we consider the
question of determining when a unit of can be lifted to a unit of .
For the wide class of separative exchange ideals , we show that the only
obstruction to lifting invertibles relies on a K-theoretic condition on .
This allows to extend previously known index theories to this context. Using
this we can draw consequences for von Neumann regular rings and C*-algebras
with real rank zero.Comment: 11 pages; to appear in Journal fur die Reine und Angewandte
Mathemati
On the -adic variation of Heegner points
In this paper, we prove an "explicit reciprocity law" relating Howard's
system of big Heegner points to a two-variable -adic -function
(constructed here) interpolating the -adic Rankin -series of
Bertolini-Darmon-Prasanna in Hida families. As applications, we obtain a direct
relation between classical Heegner cycles and the higher weight specializations
of big Heegner points, refining earlier work of the author, and prove the
vanishing of Selmer groups of CM elliptic curves twisted by 2-dimensional Artin
representations in cases predicted by the equivariant Birch and Swinnerton-Dyer
conjecture.Comment: 26 page
An Experiment on Learning Appropriate Selectional Restrictions from a Parsed Corpus
We present a methodology to extract Selectional Restrictions at a variable
level of abstraction from phrasally analyzed corpora. The method relays in the
use of a wide-coverage noun taxonomy and a statistical measure of the
co-occurrence of linguistic items. Some experimental results about the
performance of the method are provided.Comment: 11 page
On Reidys and Stadler's metrics for RNA secondary structures
We compute explicitly several abstract metrics for RNA secondary structures
defined by Reidys and Stadler.Comment: 6 page
Cosmological acceleration from a gas of strings
In string gas cosmology, the extra dimensions of the underlying theory are
kept at a microscopic scale by a gas of strings. In the matter-dominated era,
however, dust pressure can lead to oscillations of the extra dimensions and to
acceleration in the three visible dimensions, even with a vanishing
cosmological term. We review the resulting oscillating expansion history, that
provides an acceptable fit to the observed accelerated expansion of the
Universe.Comment: 6 pages, 2 figures. Proceedings of the GGI Dark Matter and Dark
Energy conferenc
TeV Dark Matter detection by Atmospheric Cerenkov Telescopes
Ground based Atmospheric Cerenkov Telescopes have recently unveiled a TeV
gamma-ray signal from the direction of the Galactic Centre. We examine whether
these gamma-rays, observed by the VERITAS, CANGAROO-II and HESS collaborations,
may arise from annihilations of dark matter particles. Emission from nearby
dwarf spheroidals, such as Sagittarius, could provide a test of this scenario.Comment: 4 pages, to appear in the proceedings of the 40th Rencontres de
Moriond, "Very High Energy Phenomena in the Universe
On the exceptional specializations of big Heegner points
We extend the -adic Gross-Zagier formula of Bertolini, Darmon, and
Prasanna to the semistable non-crystalline setting, and combine it with our
previous work to obtain a derivative formula for the specializations of
Howard's big Heegner points at exceptional primes in the Hida family.Comment: 23 page
The group structure of the normalizer of
We determine the group structure of the normalizer of in
modulo . These results correct the Atkin-Lehner
statement at the paper Hecke operators of
Equidistribution, L-functions, and Sato-Tate groups
In this expository note, we present an approach to the generalization of
Serre of the Sato-Tate Conjecture. Most of its content is taken from Serre's
original references. However, we provide a few new examples and supply
references to recent progress developed in the area.Comment: 23 page
-adic heights of Heegner points and Beilinson-Flach elements
We give a new proof of Howard's -adic Gross-Zagier formula, which we
extend to the context of indefinite Shimura curves over attached
to nonsplit quaternion algebras. This formula relates the cyclotomic derivative
of a two-variable -adic -function restricted to the anticyclotomic line
to the cyclotomic -adic heights of Heegner points over the anticyclotomic
tower, and our proof, rather than inspired by the original approaches of
Gross-Zagier and Perrin-Riou, is via Iwasawa theory, based on the connection
between Heegner points, Beilinson-Flach elements, and their explicit
reciprocity laws.Comment: To appear in J. Lond. Math. So
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