Coupled quintessence and vacuum decay

We discuss observational consequences of a class of cosmological models characterized by the dilution of pressureless matter attenuated with respect to the usual $a^{-3}$ scaling due to the decay of vacuum energy. We carry out a joint statistical analysis of observational data from the new \emph{gold} sample of 182 SNe Ia, recent estimates of the CMB shift parameter, and BAO measurements from the SDSS to show that such models favor the decay of vacuum only into the dark matter sector, and that the separately conserved baryons cannot be neglected. In order to explore ways to more fundamentally motivated models, we also derive a coupled scalar field version for this general class of vacuum decay scenarios.Comment: 6 pages, 3 figures, LaTe

Geometrical Constraints on the Cosmological Constant

The cosmological constant problem is examined under the assumption that the extrinsic curvature of the space-time contributes to the vacuum. A compensation mechanism based on a variable cosmological term is proposed. Under a suitable hypothesis on the behavior of the extrinsic curvature, we find that an initially large $\Lambda(t)$ rolls down rapidly to zero during the early stages of the universe. Using perturbation analysis, it is shown that such vacuum behaves essentially as a spin-2 field which is independent of the metric.Comment: [email protected], 17 pages, Latex, 2 figures obtained by reques

Ideally embedded space-times

Due to the growing interest in embeddings of space-time in higher-dimensional spaces we consider a specific type of embedding. After proving an inequality between intrinsically defined curvature invariants and the squared mean curvature, we extend the notion of ideal embeddings from Riemannian geometry to the indefinite case. Ideal embeddings are such that the embedded manifold receives the least amount of tension from the surrounding space. Then it is shown that the de Sitter spaces, a Robertson-Walker space-time and some anisotropic perfect fluid metrics can be ideally embedded in a five-dimensional pseudo-Euclidean space.Comment: layout changed and typos corrected; uses revtex

Biology of the iberian chub (Squalius carolitertii) in an atlantic-type stream (river Lima basin-north Portugal). A preliminary approach

The iberian chub (Squalius carolitertii) is an endemic species whose biology is yet largely unknown and which is catalogued as being endangered. Therefore more information about its biology is essential to develop appropriate management strategies. The Estorâos River population has been studied from December 1995 to March 2002 through regular electro-fishing surveys. Additionally, a fish trap installed in the river from November 2001 to July 2002 allowed for the collection of information on population movements and reproduction. The results revealed some fluctuations in the density estimates, though the Squalius carolitertii population in the Estorâos River is quite low. Six age classes (0+ to 5+) were identified. Iberian chub growth is isometric and can reach a final length of 33.5 cm. Sexual dimorphism is evident, with males maturing earlier and at smaller sizes. An increase of the Iberian chub movements was detected from middle April onwards. These movements were related to the beginning of the reproductive period and were mainly correlated with the rise of water temperature. Our results indicate that the population characteristics do not differ substantially from those of other endemic chub populations in the Iberic peninsula.El bordallo (Squalius carolitertii) es una especie cuya biología es en gran parte desconocida y que está catalogada en peligro de extinción. El estudio de su biología es importante para la gestión de sus poblaciones y de su hábitat. La población del río Estorâos (Cuenca del río Límia) ha sido estudiada de Diciembre de 1995 a Marzo de 2002 mediante muestreos con pesca eléctrica. Un sistema de redes utilizado de Noviembre de 2001 a Julio de 2002 permitió la obtención de información sobre los movimientos y parámetros reproductivos de la población. Los datos indican fluctuaciones de la densidad, a pesar de la población presentar valores muy bajos. Seis clases de edad (0+ a 5+) han sido identificadas. El crecimiento de Squalius carolitertii es isométrico y puede llegar a una talla final de 33,5 cm. El dimorfismo sexual es evidente y los machos maduran más temprano y con tallas inferiores a de las hembras. Un creciente de movimientos del bordallo ha sido encontrado a mediados del mes de Abril, lo que está de acuerdo con la fecha del período reproductivo y también con el incremento de la temperatura del agua. Nuestros datos indican que esta población no es muy distinta de otras poblaciones de bordallos endémicos de la península Ibérica

Scalar field description of decaying-Λ\Lambda cosmologies

The conditions under which cosmologies driven by time varying cosmological terms can be described by a scalar field coupled to a perfect fluid are discussed. An algorithm to reconstruct potentials dynamically and thermodynamically analogue to given phenomenological $\Lambda$ models is presented. As a worked example, the deflationary cosmology, which evolves from a pure de Sitter vacuum state to a slightly modified FRW cosmology is considered. It is found that this is an example of nonsingular warm inflation with an asymptotic exponential potential. Differences with respect to other scalar field descriptions of decaying vacuum cosmologies are addressed and possible extensions are indicated.Comment: 12 pages, revtex, references added, corrected typos and minor text change

Reliability and validity of the Pittsburgh Sleep Quality Index in breast cancer patients

Purpose: We aimed to assess the factor structure, internal consistency, test-retest reliability, and construct validity of the European Portuguese version of the Pittsburgh Sleep Quality Index (PSQI) in breast cancer patients. Methods: This study was based on a cohort of breast cancer patients, among whom the PSQI was used to measure sleep quality three years after cancer diagnosis (N = 474). A sample of 62 participants underwent additional PSQI testing, wore a wrist actigraph for five consecutive days, and was reevaluated with the PSQI after one month. A confirmatory factor analysis, considering the components suggested by the principal component analysis (PCA), was performed to determine model fit. To evaluate internal consistency and test-retest reliability, Cronbach’s alpha and intraclass correlation coefficient (ICC) were calculated, respectively. To assess construct validity, Spearman’s correlation coefficients were computed between PSQI scores and actigraphy measures and other theoretical related constructs. Results: PCA suggested one or two components. The latter showed better fit to the data, though the two factors were strongly correlated (r = 0.76) and internal consistency was not satisfactory for one of the factors. Regarding the one-factor model, internal consistency (Cronbach’s alpha = 0.70) and test-retest reliability (ICC = 0.76) were adequate. Sleep duration, habitual sleep efficiency, and sleep disturbance dimensions were significantly correlated with the corresponding actigraphy measures; the PSQI global score derived from the one-factor model was more strongly correlated with subjective sleep complaints (r ≥ 0.60). Conclusions: The unidimensional construct of the European Portuguese version of the PSQI showed adequate reliability and validity among breast cancer patients.This study was funded by FEDER through the Operational Programme Competitiveness and Internationalization (POCI-01-0145-FEDER-016867) and national funding from the Foundation for Science and Technology (FCT) (Portuguese Ministry of Science, Technology and Higher Education) (PTDC/DTP-EPI/7283/2014) under the Unidade de Investigação em Epidemiologia - Instituto de Saúde Pública da Universidade do Porto (EPIUnit) (POCI-01-0145-FEDER-006862; Ref.UID/DTP/04750/2013); the PhD Grant SFRH/BD/92630/2013 (Filipa Fontes) co-funded by the FCT and the POPH/FSE Program