37,090 research outputs found
Hypersensitivity and chaos signatures in the quantum baker's maps
Classical chaotic systems are distinguished by their sensitive dependence on
initial conditions. The absence of this property in quantum systems has lead to
a number of proposals for perturbation-based characterizations of quantum
chaos, including linear growth of entropy, exponential decay of fidelity, and
hypersensitivity to perturbation. All of these accurately predict chaos in the
classical limit, but it is not clear that they behave the same far from the
classical realm. We investigate the dynamics of a family of quantizations of
the baker's map, which range from a highly entangling unitary transformation to
an essentially trivial shift map. Linear entropy growth and fidelity decay are
exhibited by this entire family of maps, but hypersensitivity distinguishes
between the simple dynamics of the trivial shift map and the more complicated
dynamics of the other quantizations. This conclusion is supported by an
analytical argument for short times and numerical evidence at later times.Comment: 32 pages, 6 figure
Linear Information Coupling Problems
Many network information theory problems face the similar difficulty of
single letterization. We argue that this is due to the lack of a geometric
structure on the space of probability distribution. In this paper, we develop
such a structure by assuming that the distributions of interest are close to
each other. Under this assumption, the K-L divergence is reduced to the squared
Euclidean metric in an Euclidean space. Moreover, we construct the notion of
coordinate and inner product, which will facilitate solving communication
problems. We will also present the application of this approach to the
point-to-point channel and the general broadcast channel, which demonstrates
how our technique simplifies information theory problems.Comment: To appear, IEEE International Symposium on Information Theory, July,
201
The Linear Information Coupling Problems
Many network information theory problems face the similar difficulty of
single-letterization. We argue that this is due to the lack of a geometric
structure on the space of probability distribution. In this paper, we develop
such a structure by assuming that the distributions of interest are close to
each other. Under this assumption, the K-L divergence is reduced to the squared
Euclidean metric in an Euclidean space. In addition, we construct the notion of
coordinate and inner product, which will facilitate solving communication
problems. We will present the application of this approach to the
point-to-point channel, general broadcast channel, and the multiple access
channel (MAC) with the common source. It can be shown that with this approach,
information theory problems, such as the single-letterization, can be reduced
to some linear algebra problems. Moreover, we show that for the general
broadcast channel, transmitting the common message to receivers can be
formulated as the trade-off between linear systems. We also provide an example
to visualize this trade-off in a geometric way. Finally, for the MAC with the
common source, we observe a coherent combining gain due to the cooperation
between transmitters, and this gain can be quantified by applying our
technique.Comment: 27 pages, submitted to IEEE Transactions on Information Theor
Astrometric Method to Break the Photometric Degeneracy between Binary-source and Planetary Microlensing Perturbations
An extra-solar planet can be detected by microlensing because the planet can
perturb the smooth lensing light curve created by the primary lens. However, it
was shown by Gaudi that a subset of binary-source events can produce light
curves that closely resemble those produced by a significant fraction of
planet/star lens systems, causing serious contamination of a sample of
suspected planetary systems detected via microlensing. In this paper, we show
that if a lensing event is observed astrometrically, one can unambiguously
break the photometric degeneracy between binary-source and planetary lensing
perturbations. This is possible because while the planet-induced perturbation
in the trajectory of the lensed source image centroid shifts points away from
the opening of the unperturbed elliptical trajectory, while the perturbation
induced by the binary source companion points always towards the opening.
Therefore, astrometric microlensing observations by using future high-precision
interferometers will be important for solid confirmation of microlensing planet
detections.Comment: total 5 pages, including 1 figure and no table, ApJ, submitted,
better quality pdf file is avalilable at
http://astroph.chungbuk.ac.kr/~cheongho/publication.htm
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