24,376 research outputs found
The Abell 85 BCG: a nucleated, core-less galaxy
New high-resolution r band imaging of the brightest cluster galaxy (BCG) in
Abell 85 (Holm 15A) was obtained using the Gemini Multi Object Spectrograph.
These data were taken with the aim of deriving an accurate surface brightness
profile of the BCG of Abell 85, in particular its central region. The new
Gemini data show clear evidence of a previously unreported nuclear emission
that is evident as a distinct light excess in the central kiloparsec of the
surface brightness profile. We find that the light profile is never flat nor
does it present a downward trend towards the center of the galaxy. That is, the
new Gemini data show a different physical reality from the featureless,
"evacuated core" recently claimed for the Abell 85 BCG. After trying different
models, we find that the surface brightness profile of the BCG of Abell 85 is
best fit by a double Sersic model.Comment: Gemini web feature: Supermassive black hole that wasn't -
http://gemini.edu/node/1247
Highly-efficient noise-assisted energy transport in classical oscillator systems
Photosynthesis is a biological process that involves the highly-efficient
transport of energy captured from the sun to a reaction center, where
conversion into useful biochemical energy takes place. Even though one can
always use a quantum perspective to describe any physical process, since
everything follows the laws of Quantum Mechanics, is the use of quantum theory
imperative to explain this high efficiency? Making use of the quantum-classical
correspondence of electronic energy transfer recently introduced by Eisfeld and
Briggs [Phys. Rev. E 85, 046118 (2012)], we show here that the highly-efficient
noise-assisted energy transport described by Rebentrost et al. [New J. Phys.
11, 033003 (2009)], and Plenio and Huelga [New J. Phys. 10, 113019 (2008)], as
the result of the interplay between the quantum coherent evolution of the
photosynthetic system and noise introduced by its surrounding environment, it
can be found as well in purely classical systems. The wider scope of
applicability of the enhancement of energy transfer assisted by noise might
open new ways for developing new technologies aimed at enhancing the efficiency
of a myriad of energy transfer systems, from information channels in
micro-electronic circuits to long-distance high-voltage electrical lines.Comment: 4 pages, 3 figure
Redundancy of classical and quantum correlations during decoherence
We analyze the time dependence of entanglement and total correlations between
a system and fractions of its environment in the course of decoherence. For the
quantum Brownian motion model we show that the entanglement and total
correlations have rather different dependence on the size of the environmental
fraction. Redundancy manifests differently in both types of correlations and
can be related with induced--classicality. To study this we introduce a new
measure of redundancy and compare it with the existing one.Comment: 6 pages, 4 figure
Comment on "General Non-Markovian Dynamics of Open Quantum Systems"
The existence of a "non-Markovian dissipationless" regime, characterized by
long lived oscillations, was recently reported for a class of quantum open
systems (Zhang et al, PRL, 109, 170402, (2012)). It is claimed this could
happen in the strong coupling regime, a surprising result which has attracted
some attention. We show that this regime exists if and only if the total
Hamiltonian is unbounded from below, casting serious doubts on the usefulness
of this result
Physical qubits from charged particles: IR divergences in quantum information
We consider soft photons effects (IR structure of QED) on the construction of
physical qubits. Soft-photons appear when we build charged qubits from the
asymptotic states of QED. This construction is necessary in order to include
the effect of soft photons on entanglement measures. The nonexistence of free
charged particles (due to the long range of QED interactions) lead us to
question the sense of the very concept of free charged qubit. In this letter,
using the "dressing" formalism, we build physical charged qubits from dressed
fields which have the correct asymptotic behavior, are gauge invariant, their
propagators have a particle pole structure and are free from infrared
divergences. Finally, we discuss the impact of the soft corrections on the
entanglement measures.Comment: 4 pages, 2 figures, RevTeX. Version 2: Some references update
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