A note on bigravity and dark matter

We show that a class of bi-gravity theories contain solutions describing dark matter. A particular member of this class is also shown to be equivalent to the Eddington-Born-Infeld gravity, recently proposed as a candidate for dark matter. Bigravity theories also have cosmological de Sitter backgrounds and we find solutions interpolating between matter and acceleration eras.Comment: 4 pages, 1 figure, minor corrections and reference additions, published in Phys. Rev.

The Atomic Lighthouse Effect

We investigate the deflection of light by a cold atomic cloud when the light-matter interaction is locally tuned via the Zeeman effect using magnetic field gradients. This "lighthouse" effect is strongest in the single-scattering regime, where deviation of the incident field is largest. For optically dense samples, the deviation is reduced by collective effects, as the increase in linewidth leads to a decrease of the magnetic field efficiency

Gender, education and reciprocal generosity: Evidence from 1,500 experiment subjects

There is not general consensus about if women are more or less generous than men. Although the number of papers supporting more generous females is a bit larger than the opposed it is not possible to establish any definitive and systematic gender bias. This paper provides new evidence on this topic using a unique experimental dataset. We used data from a field experiment conducted under identical conditions (and monetary payoffs) in 6 Latin American cities, Bogotá, Buenos Aires, Caracas, Lima, Montevideo and San José. Our dataset amounted to 3,107 experimental subjects who played the Trust Game. We will analyze the determinants of behavior of second movers, that is, what determines reciprocal generosity. In sharp contrast to previous papers we found that males are more generous than females. In the light of this result, we carried out a systematic analysis of individual features (income, education, age, etc.) for females and males separately. We found differential motivations for women and men. Third, we see that (individual) education enhances prosocial behavior. Lastly, we see that subjects’ expectations are crucial.reciprocal altruism, gender, education

Sensitivity of electromagnetically induced transparency to light-mediated interactions

Here we present a microscopic model that describes the Electromagnetically Induced Transparency (EIT) phenomenon in the multiple scattering regime. We consider an ensemble of cold three-level atoms, in a $\Lambda$ configuration, scattering a probe and a control field to the vacuum modes of the electromagnetic field. By first considering a scalar description of the scattering, we show that the light-mediated long-range interactions that emerge between the dipoles narrow the EIT transparency window for increasing densities and sample sizes. For a vectorial description, we demonstrate that near-field interacting terms can critically affect the atomic population transfer in the Stimulated Raman Adiabatic Passage (STIRAP). This result points out that standard STIRAP-based quantum memories in cold atomic ensembles would not reach high enough efficiencies for quantum information processing applications even in dilute regimes.Comment: 9 pages, 5 figure

Boussinesq Solitons as Propagators of Neural Signals

We  consider  certain  approximation for determining the  equation  of motion  for nerve  signals by  using  the  model  of the  lipid  melting  of membranes.   The  nerve  pulses  are  found  to  display nonlinearity and  dispersion  during  the  melting  transition.  In this  simplified model the  nonlinear equation  early  proposed  by  Heimburg  and  coworkers  transformed to  the  well known  integrable Boussinesq  non linear  equation.   Under  specific values of the  parametric space this  system  shows the  existence  of singular  and  regular  soliton  like structures.   After  their  collisions  the  mutual creation  and annihilation (each other)  of nerve signals along the  nerve,  during  their  propagation, has been observed.Keywords: Boussinesq equation,  singular  solitons,  single neurons,  neural  code

Black Hole Entropy and the Dimensional Continuation of the Gauss-Bonnet Theorem

The Euclidean black hole has topology $\Re^2 \times {\cal S}^{d-2}$. It is shown that -in Einstein's theory- the deficit angle of a cusp at any point in $\Re^2$ and the area of the ${\cal S}^{d-2}$ are canonical conjugates. The black hole entropy emerges as the Euler class of a small disk centered at the horizon multiplied by the area of the ${\cal S}^{d-2}$ there.These results are obtained through dimensional continuation of the Gauss-Bonnet theorem. The extension to the most general action yielding second order field equations for the metric in any spacetime dimension is given.Comment: 7 pages, RevTe

Uncontrolled Diabetes as an Associated Factor with Dynapenia in Adults Aged 50 Years or Older: Sex Differences

BACKGROUND: Epidemiological studies demonstrate an association between diabetes and low neuromuscular strength (NMS). However, none have grouped participants into non-diabetics (ND), undiagnosed diabetics (UDD), controlled diabetics (CD) and uncontrolled diabetics (UCD) or investigated what glycated hemoglobin levels (HbA1c) are associated with low NMS (dynapenia) by sex. METHODS: We analyzed the association between UDD, CD and UCD and dynapenia, the extent to which the different groupings of these individuals modifies this association and the association between HbA1c levels and NMS, by sex, in a cross-sectional study involving 5,290 participants ≥ 50 years from the ELSA study. In the first two analyses, logistic regression models were used with dynapenia (grip strength < 26kg in men and < 16kg in women) as outcome and diabetes [ND, UDD, CD and UCD] as exposure. Next, linear regression was performed with grip strength as outcome and the participants classified based on HbA1c level as exposure. The models were adjusted by sociodemographic, behavioral and clinical characteristics. RESULTS: Compared to ND only UCD was associated with dynapenia (men OR=2.37 95% CI 1.36-4.14; women OR=1.67 95% CI 1.01-2.79). This association was less clear, particularly in women, when CD and UCD groups were merged. HbA1c ≥ 6.5% in men and ≥ 8.0% in women were associated with lower NMS. CONCLUSIONS: UCD increases the chance of dynapenia in both sexes. The different groupings based on diabetes status modify the association between UCD and dynapenia. The threshold of HbA1c associated with reduced NMS is lower in men compared to women

Potencial antifúngico de substâncias vegetais à Moniliophthora perniciosa.

Este trabalho teve como objetivo a avaliação da fungitoxicidade in vitro de substâncias de origem vegetal a M. perniciosa