22,183 research outputs found
InfluĂȘncia do espaçamento nas caracterĂsticas fĂsico-mecĂąnicas da madeira de Bagassa guianensis Aubl. (Tatajuba) no planalto de Belterra, ParĂĄ.
bitstream/item/59284/1/CPATU-ComTec88.pd
Cosmological constant constraints from observation-derived energy condition bounds and their application to bimetric massive gravity
Among the various possibilities to probe the theory behind the recent
accelerated expansion of the universe, the energy conditions (ECs) are of
particular interest, since it is possible to confront and constrain the many
models, including different theories of gravity, with observational data. In
this context, we use the ECs to probe any alternative theory whose extra term
acts as a cosmological constant. For this purpose, we apply a model-independent
approach to reconstruct the recent expansion of the universe. Using Type Ia
supernova, baryon acoustic oscillations and cosmic-chronometer data, we perform
a Markov Chain Monte Carlo analysis to put constraints on the effective
cosmological constant . By imposing that the cosmological
constant is the only component that possibly violates the ECs, we derive lower
and upper bounds for its value. For instance, we obtain that and within,
respectively, and confidence levels. In addition, about
30\% of the posterior distribution is incompatible with a cosmological
constant, showing that this method can potentially rule it out as a mechanism
for the accelerated expansion. We also study the consequence of these
constraints for two particular formulations of the bimetric massive gravity.
Namely, we consider the Visser's theory and the Hassan and Roses's massive
gravity by choosing a background metric such that both theories mimic General
Relativity with a cosmological constant. Using the
observational bounds along with the upper bounds on the graviton mass we obtain
constraints on the parameter spaces of both theories.Comment: 11 pages, 4 figures, 1 tabl
Experimental Observation of Quantum Correlations in Modular Variables
We experimentally detect entanglement in modular position and momentum
variables of photon pairs which have passed through -slit apertures. We
first employ an entanglement criteria recently proposed in [Phys. Rev. Lett.
{\bf 106}, 210501 (2011)], using variances of the modular variables. We then
propose an entanglement witness for modular variables based on the Shannon
entropy, and test it experimentally. Finally, we derive criteria for
Einstein-Podolsky-Rosen-Steering correlations using variances and entropy
functions. In both cases, the entropic criteria are more successful at
identifying quantum correlations in our data.Comment: 7 pages, 4 figures, comments welcom
Silvicultura de cinco espécies arbóreas da AmazÎnia: indicaçÔes de usos de seus produtos madeireiros e não-madeireiros.
bitstream/item/57645/1/CPATU-ComTec90.pd
InformaçÔes båsicas sobre ecologia e silvicultura de cinco espécies arbóreas da AmazÎnia brasileira.
bitstream/item/63525/1/Oriental-Doc101.PD
Symmetry Breaking Study with Random Matrix Ensembles
A random matrix model to describe the coupling of -fold symmetry is
constructed. The particular threefold case is used to analyze data on
eigenfrequencies of elastomechanical vibration of an anisotropic quartz block.
It is suggested that such experimental/theoretical study may supply a powerful
means to discern intrinsic symmetry of physical systems.Comment: 12 pages, 3 figures Contribution to the International Workshop on
Nuclei and Mesoscopic Physics (WNM07), 20-22 October, Michigan Sate
University, East Lansing, Michigan. To appear in a AIP Proceeding (Pawel
Danielewicz, Editor
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