30,721 research outputs found
Symmetry Breaking Study with Deformed Ensembles
A random matrix model to describe the coupling of m-fold symmetry in
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 powerful
means to discern intrinsic symmetries in physical systems.Comment: 12 pages, 5 figure
Cosmic homogeneity: a spectroscopic and model-independent measurement
Cosmology relies on the Cosmological Principle, i.e., the hypothesis that the
Universe is homogeneous and isotropic on large scales. This implies in
particular that the counts of galaxies should approach a homogeneous scaling
with volume at sufficiently large scales. Testing homogeneity is crucial to
obtain a correct interpretation of the physical assumptions underlying the
current cosmic acceleration and structure formation of the Universe. In this
Letter, we use the Baryon Oscillation Spectroscopic Survey to make the first
spectroscopic and model-independent measurements of the angular homogeneity
scale . Applying four statistical estimators, we show that the
angular distribution of galaxies in the range 0.46 < z < 0.62 is consistent
with homogeneity at large scales, and that varies with
redshift, indicating a smoother Universe in the past. These results are in
agreement with the foundations of the standard cosmological paradigm.Comment: 5 pages, 2 figures, Version accepted by MNRA
Influência do espaçamento nas características físico-mecânicas da madeira de Bagassa guianensis Aubl. (Tatajuba) no planalto de Belterra, Pará.
bitstream/item/59284/1/CPATU-ComTec88.pd
Forecasting cosmological constraints from age of high-z galaxies
We perform Monte Carlo simulations based on current age estimates of high-z
objects to forecast constraints on the equation of state (EoS) of the dark
energy. In our analysis, we use two different EoS parameterizations, namely,
the so-called CPL and its uncorrelated form and calculate the improvements on
the figure of merit for both cases. Although there is a clear dependence of the
FoM with the size and accuracy of the synthetic age samples, we find that the
most substantial gain in FoM comes from a joint analysis involving age and
baryon acoustic oscillation data.Comment: 4 pages, 13 figures, late
Probing the two-scale-factor universality hypothesis by exact rotation symmetry-breaking mechanism
We probe the two-scale factor universality hypothesis by evaluating, firstly
explicitly and analytically at the one-loop order, the loop quantum corrections
to the amplitude ratios for O() scalar field theories with
rotation symmetry-breaking in three distinct and independent methods in which
the rotation symmetry-breaking mechanism is treated exactly. We show that the
rotation symmetry-breaking amplitude ratios turn out to be identical in the
three methods and equal to their respective rotation symmetry-breaking ones,
although the amplitudes themselves, in general, depend on the method employed
and on the rotation symmetry-breaking parameter. At the end, we show that all
these results can be generalized, through an inductive process based on a
general theorem emerging from the exact calculation, to any loop level and
physically interpreted based on symmetry ideas.Comment: 17 pages, 3 figure
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
Controlling entanglement by direct quantum feedback
We discuss the generation of entanglement between electronic states of two
atoms in a cavity using direct quantum feedback schemes. We compare the effects
of different control Hamiltonians and detection processes in the performance of
entanglement production and show that the quantum-jump-based feedback proposed
by us in Phys. Rev. A {\bf 76} 010301(R) (2007) can protect highly entangled
states against decoherence. We provide analytical results that explain the
robustness of jump feedback, and also analyse the perspectives of experimental
implementation by scrutinising the effects of imperfections and approximations
in our model.Comment: 10 pages, 8 figures. To appear in PR
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