24,933 research outputs found
Nonlinear Zeno dynamics due to atomic interactions in Bose-Einstein condensate
We show that nonlinear interactions induce both the Zeno and anti-Zeno
effects in the generalised Bose-Josephson model (with the on-site interactions
and the second-order tunneling) describing Bose-Einstein condensate in
double-well trap subject to particle removal from one of the wells. We find
that the on-site interactions induce \textit{only} the Zeno effect, which
appears at long evolution times, whereas the second-order tunneling leads to a
strong decay of the atomic population at short evolution times, reminiscent of
the anti-Zeno effect, and destroys the nonlinear Zeno effect due to the on-site
interactions at long times.Comment: 8 pages, 3 figures. Physica B, DOI: 10.1016/j.physb.2014.08.00
Group Quantization on Configuration Space: Gauge Symmetries and Linear Fields
A new, configuration-space picture of a formalism of group quantization, the
GAQ formalism, is presented in the context of a previous, algebraic
generalization. This presentation serves to make a comprehensive discussion in
which other extensions of the formalism, particularly to incorporate gauge
symmetries, are developed as well. Both images are combined in order to
analyse, in a systematic manner and with complete generality, the case of
linear fields (abelian current groups). To ilustrate these developments we
particularize them for several fields and, in particular, we carry out the
quantization of the abelian Chern-Simons models over an arbitrary closed
surface in detail.Comment: Plain LaTeX, 31 pages, no macros. To appear in J. Math. Phy
The Electromagnetic and Proca Fields Revisited: a Unified Quantization
Quantizing the electromagnetic field with a group formalism faces the
difficulty of how to turn the traditional gauge transformation of the vector
potential, , into a
group law. In this paper it is shown that the problem can be solved by looking
at gauge transformations in a slightly different manner which, in addition,
does not require introducing any BRST-like parameter. This gauge transformation
does not appear explicitly in the group law of the symmetry but rather as the
trajectories associated with generalized equations of motion generated by
vector fields with null Noether invariants. In the new approach the parameters
of the local group, , acquire dynamical content outside the
photon mass shell, a fact which also allows a unified quantization of both the
electromagnetic and Proca fields.Comment: 16 pages, latex, no figure
Electromagnetic quasinormal modes of five-dimensional topological black holes
We calculate exactly the QNF of the vector type and scalar type
electromagnetic fields propagating on a family of five-dimensional topological
black holes. To get a discrete spectrum of quasinormal frequencies for the
scalar type electromagnetic field we find that it is necessary to change the
boundary condition usually imposed at the asymptotic region. Furthermore for
the vector type electromagnetic field we impose the usual boundary condition at
the asymptotic region and we discuss the existence of unstable quasinormal
modes in the five-dimensional topological black holes.Comment: 16 pages. Already published in Revista Mexicana de Fisic
Moduli Spaces and Formal Operads
Let overline{M}_{g,n} be the moduli space of stable algebraic curves of genus
g with n marked points. With the operations which relate the different moduli
spaces identifying marked points, the family (overline{M}_{g,n})_{g,n} is a
modular operad of projective smooth Deligne-Mumford stacks, overline{M}. In
this paper we prove that the modular operad of singular chains
C_*(overline{M};Q) is formal; so it is weakly equivalent to the modular operad
of its homology H_*(overline{M};Q). As a consequence, the "up to homotopy"
algebras of these two operads are the same. To obtain this result we prove a
formality theorem for operads analogous to Deligne-Griffiths-Morgan-Sullivan
formality theorem, the existence of minimal models of modular operads, and a
characterization of formality for operads which shows that formality is
independent of the ground field.Comment: 36 pages (v3: some typographical corrections
A Cartan-Eilenberg approach to Homotopical Algebra
In this paper we propose an approach to homotopical algebra where the basic
ingredient is a category with two classes of distinguished morphisms: strong
and weak equivalences. These data determine the cofibrant objects by an
extension property analogous to the classical lifting property of projective
modules. We define a Cartan-Eilenberg category as a category with strong and
weak equivalences such that there is an equivalence between its localization
with respect to weak equivalences and the localised category of cofibrant
objets with respect to strong equivalences. This equivalence allows us to
extend the classical theory of derived additive functors to this non additive
setting. The main examples include Quillen model categories and functor
categories with a triple, in the last case we find examples in which the class
of strong equivalences is not determined by a homotopy relation. Among other
applications, we prove the existence of filtered minimal models for \emph{cdg}
algebras over a zero-characteristic field and we formulate an acyclic models
theorem for non additive functors
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