A Note on the Local Cosmological Constant and the Dark Energy Coincidence Problem

It has been suggested that the Dark Energy Coincidence Problem could be interpreted as a possible link between the cosmological constant and a massive graviton. We show that by using that link and models for the graviton mass a dark energy density can be obtained that is indeed very close to measurements by WMAP. As a consequence of the models, the cosmological constant was found to depend on the density of matter. A brief outline of the cosmological consequences such as the effect on the black hole solution is given

Análises de tecido vegetal: manual de laboratório.

bitstream/item/57831/1/CPATU-Doc92.pd

Métodos de superação de dormência em Piptadenia adiantoides (SPRENG.) J.F. MACBR. (Fabaceae:Mimosoideae).

O objetivo deste trabalho foi avaliar os tratamentos mais eficazes na promoção da germinação de sementes de P. adiantoides, propor sua utilização como alternativa para o reflorestamento e proporcior novas informações sobre a espécie Piptadenia adiantoides

Quintessence and Scalar Dark Matter in the Universe

Continuing with previous works, we present a cosmological model in which dark matter and dark energy are modeled by scalar fields $\Phi$ and $\Psi$, respectively, endowed with the scalar potentials $V(\Phi)=V_{o}[ \cosh {(\lambda \sqrt{\kappa_{o}}\Phi)}-1]$ and $\tilde{V}(\Psi)=\tilde{V_{o}}[ \sinh {(\alpha \sqrt{\kappa_{o}}\Psi)}] ^{\beta}$. This model contains 95% of scalar field. We obtain that the scalar dark matter mass is $m_{\Phi}\sim 10^{-26}eV.$ The solution obtained allows us to recover the success of the standard CDM. The implications on the formation of structure are reviewed. We obtain that the minimal cutoff radio for this model is $r_{c}\sim 1.2 kpc.$Comment: 4 pages REVTeX, 3 eps color figures. Minor changes and references updated. To appear in Classical and Quantum Gravity as a Letter to the Editor. More information at http://www.fis.cinvestav.mx/~siddh/PHI

Automatic detection of hyperarticulated speech

Hyperarticulation is a speech adaptation that consists of adopting a clearer form of speech in an attempt to improve recognition levels. However, it has the opposite effect when talking to ASR systems, as they are not trained with such kind of speech. We present approaches for automatic detection of hyperarticulation, which can be used to improve the performance of spoken dialog systems. We performed experiments on Let’s Go data, using multiple feature sets and two classification approaches. Many relevant features are speaker dependent. Thus, we used the first turn in each dialog as the reference for the speaker, since it is typically not hyperarticulated. Our best results were above 80 % accuracy, which represents an improvement of at least 11.6 % points over previously obtained results on similar data. We also assessed the classifiers’ performance in scenarios where hyperarticulation is rare, achieving around 98 % accuracy using different confidence thresholds.info:eu-repo/semantics/acceptedVersio

Quantum mechanical counterpart of nonlinear optics

Raman-type laser excitation of a trapped atom allows one to realize the quantum mechanical counterpart of phenomena of nonlinear optics, such as Kerr-type nonlinearities, parametric amplification, and multi-mode mixing. Additionally, huge nonlinearities emerge from the interference of the atomic wave function with the laser waves. They lead to a partitioning of the phase space accompanied by a significantly different action of the time evolution in neighboring phase-space zones. For example, a nonlinearly modified coherent "displacement" of the motional quantum state may induce strong amplitude squeezing and quantum interferences.Comment: 6 pages, 4 figures, to be published in Phys. Rev. A 55 (June

Renormalization of Quantum Anosov Maps: Reduction to Fixed Boundary Conditions

A renormalization scheme is introduced to study quantum Anosov maps (QAMs) on a torus for general boundary conditions (BCs), whose number ($k$) is always finite. It is shown that the quasienergy eigenvalue problem of a QAM for {\em all} $k$ BCs is exactly equivalent to that of the renormalized QAM (with Planck's constant $\hbar ^{\prime}=\hbar /k$) at some {\em fixed} BCs that can be of four types. The quantum cat maps are, up to time reversal, fixed points of the renormalization transformation. Several results at fixed BCs, in particular the existence of a complete basis of ``crystalline'' eigenstates in a classical limit, can then be derived and understood in a simple and transparent way in the general-BCs framework.Comment: REVTEX, 12 pages, 1 table. To appear in Physical Review Letter

Quantum-state synthesis of multi-mode bosonic fields: Preparation of arbitrary states of 2-D vibrational motion of trapped ions

We present a universal algorithm for an efficient deterministic preparation of an arbitrary two--mode bosonic state. In particular, we discuss in detail preparation of entangled states of a two-dimensional vibrational motion of a trapped ion via a sequence of laser stimulated Raman transitions. Our formalism can be generalized for multi-mode bosonic fields. We examine stability of our algorithm with respect to a technical noise.Comment: 8 pages, revtex, including 2 ps-figures, section about physical implementation added, references updated, submitted to Phys. Rev. A, computer program available at http://www.savba.sk/sav/inst/fyzi/qo