The fate of non-trivial entanglement under gravitational collapse

We analyse the evolution of the entanglement of a non-trivial initial quantum field state (which, for simplicity, has been taken to be a bipartite state made out of vacuum and the first excited state) when it undergoes a gravitational collapse. We carry out this analysis by generalising the tools developed to study entanglement behaviour in stationary scenarios and making them suitable to deal with dynamical spacetimes. We also discuss what kind of problems can be tackled using the formalism spelled out here as well as single out future avenues of research.Comment: 9 pages, 2 figures. v2: Added Journal reference and small changes to match published versio

Echo of the Quantum Bounce

We identify a signature of quantum gravitational effects that survives from the early universe to the current era: Fluctuations of quantum fields as seen by comoving observers are significantly influenced by the history of the early universe. In particular we show how the existence (or not) of a quantum bounce leaves a trace in the background quantum noise that is not damped and would be non-negligible even nowadays. Furthermore, we estimate an upper bound for the typical energy and length scales where quantum effects are relevant. We discuss how this signature might be observed and therefore used to build falsifiability tests of quantum gravity theories.Comment: Revtex4.1. 2 Figures. V2: Content extended and edited to match published versio

The Quantum Echo of the Early Universe

We show that the fluctuations of quantum fields as seen by late comoving observers are significantly influenced by the history of the early Universe, and therefore they transmit information about the nature of spacetime in timescales when quantum gravitational effects were non-negligible. We discuss how this may be observable even nowadays, and thus used to build falsifiability tests of quantum gravity theories.Comment: 3 pages. 2 Figures. Proceedings Theory Canada 9. Published in Canadian Journal of Physics. (http://www.nrcresearchpress.com/doi/abs/10.1139/cjp-2014-0567

Violation of the strong Huygen's principle and timelike signals from the early Universe

We analyze the implications of the violations of the strong Huygens principle in the transmission of information from the early universe to the current era via massless fields. We show that much more information reaches us through timelike channels (not mediated by real photons) than it is carried by rays of light, which are usually regarded as the only carriers of information.Comment: 5 pages, 2 figures. RevTeX 4.1. V2: Updated to match published version. Previous title "A glimpse of the early universe without real light" modified to match Physical Review Letters published versio

The Unruh effect without thermality

We show that uniformly accelerated detectors can display genuinely thermal features even if the Kubo-Martin-Schwinger (KMS) condition fails to hold. These features include satisfying thermal detailed balance and having a Planckian response identical to cases in which the KMS condition is satisfied. In this context, we discuss that satisfying the KMS condition for accelerated trajectories is just sufficient but not necessary for the Unruh effect to be present in a given quantum field theory. Furthermore, we extract the necessary and sufficient conditions for the response function of an accelerated detector to be thermal in the infinitely adiabatic limit. This analysis provides new insights about the interplay between the KMS condition and the Unruh effect, and a solid framework in which the robustness of the Unruh effect against deformations of quantum field theories (perhaps Lorentz-violating) can be answered unambiguously.Comment: 6 pages. no figures. RevTeX 4.

Numerical modeling of multiple steady-state convective modes in a tilted porous medium heated from below

Numerical simulations are carried out to determine the steady-state convective modes in a rectangular porous cavity heated from below. The property of multiplicity of solutions for a given set of governing parameters is examined in this paper. The multiple steady-state solutions that appear in a horizontal cavity for a given Rayleigh number are obtained by means of suitable initial conditions. Each of these solutions is then perturbed by increasing the inclination angle in order to identify the transition angle to a different convective mode. It is observed that for an odd-number of convective cells, if the counterclockwise rotating cells dominate the configuration, the Nusselt number increases with the slope angle up to a maximum and then decreases before the transition to single cell convection. Otherwise, if there are more clockwise rotating cells, the Nusselt number decreases monotonically and the configuration becomes unstable. Since multicellular configurations with even number of convective cells have equal number of clockwise and counterclockwise rotating cells, this case presents a single behavior characterized by a decrease in the Nusselt number. The transition angles from multicellular to single cell convection are found to be as large as 45° when the aspect ratio of the cavity is large, so that this angle is the upper limit to destabilize multicellular convection

Magnified expansion and compression of subpicosecond pulses from a frequency-doubled Nd:YLF laser

Includes bibliographical references.Pulses from a mode-locked frequency-doubled Nd:YLF laser have been spectrally broadened and subsequently expanded to more than 200 ps and recompressed to 750 fs by grating compressors with magnifying telescopes. The new design magnifies the time delay dispersion to a factor 10 times larger than achievable with standard compressors of similar size. The design of the system and its sensitivity to the variations in the position of its optical components is analyzed. The scheme will allow efficient amplification of subpicosecond pulses in dye amplifiers.This work was supported by N.S.F.-CONICET U.S.A./Argentina Cooperative Science Program under Grant INT 8802563, and by the National Science Foundation under Grants ECS 870507 and ECS 8606226. M. C. Marconi was supported by a Fellowship from the Universidad Nacional de Buenos Aires and Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina

De la biografía a la prosopografía: los parlamentarios de los distritos de Vasconia en la II República española (1931-1939)

Having carried out a micro-biographical analysis, using primary sources, of the 610 parliamentarians who represented the Basque districts between 1808 and 1939 in successive biographical dictionaries, we now undertake a prosopographical analysis of 44 parliamentarians who represented the districts of the Basque Country in the Spanish II Republic (1931-1939). Aspects covered include: geographical origin, age, life expectancy, educational and professional profile, cultural level and sociability, continuity in political activity between the Monarchy and the Republic. The work offers novel comparative conclusions.Realizado un análisis microbiográfico, con fuentes primarias, de los 610 parlamentarios que representaron a los distritos vascos entre 1808 y 1939 en sucesivos diccionarios biográficos, abordamos el análisis prosopográfico de los 44 parlamentarios que representaron a los distritos de Vasconia en la II República española (1931-1939): origen geográfico, edad, esperanza de vida, perfil educativo y profesional, nivel cultural y sociabilidad, continuidad en la actividad política entre la Monarquía y la República. El trabajo ofrece conclusiones comparativas novedosas