6,475 research outputs found
The Cosmic Ray p+He energy spectrum in the 3-3000 TeV energy range measured by ARGO-YBJ
The ARGO-YBJ experiment is a full coverage air shower detector operated at
the Yangbajing International Cosmic Ray Observatory. The detector has been in
stable data taking in its full configuration since November 2007 to February
2013. The high altitude and the high segmentation and spacetime resolution
offer the possibility to explore the cosmic ray energy spectrum in a very wide
range, from a few TeV up to the PeV region. The high segmentation allows a
detailed measurement of the lateral distribution, which can be used in order to
discriminate showers produced by light and heavy elements. In this work we
present the measurement of the cosmic ray light component spectrum in the
energy range 3-3000 TeV. The analysis has been carried out by using a
two-dimensional unfolding method based on the Bayes' theorem.Comment: Talk given at RICAP14 conferenc
Optimal fidelity of teleportation of coherent states and entanglement
We study the Braunstein-Kimble protocol for the continuous variable
teleportation of a coherent state. We determine lower and upper bounds for the
optimal fidelity of teleportation, maximized over all local Gaussian operations
for a given entanglement of the two-mode Gaussian state shared by the sender
(Alice) and the receiver (Bob). We also determine the optimal local
transformations at Alice and Bob sites and the corresponding maximum fidelity
when one restricts to local trace-preserving Gaussian completely positive maps.Comment: 10 pages, 2 figure
Vandermonde-subspace Frequency Division Multiplexing for Two-Tiered Cognitive Radio Networks
Vandermonde-subspace frequency division multiplexing (VFDM) is an overlay
spectrum sharing technique for cognitive radio. VFDM makes use of a precoder
based on a Vandermonde structure to transmit information over a secondary
system, while keeping an orthogonal frequency division multiplexing
(OFDM)-based primary system interference-free. To do so, VFDM exploits
frequency selectivity and the use of cyclic prefixes by the primary system.
Herein, a global view of VFDM is presented, including also practical aspects
such as linear receivers and the impact of channel estimation. We show that
VFDM provides a spectral efficiency increase of up to 1 bps/Hz over cognitive
radio systems based on unused band detection. We also present some key design
parameters for its future implementation and a feasible channel estimation
protocol. Finally we show that, even when some of the theoretical assumptions
are relaxed, VFDM provides non-negligible rates while protecting the primary
system.Comment: 9 pages, accepted for publication in IEEE Transactions on
Communication
A general theorem on the divergence of vortex beams
The propagation and divergence properties of beams carrying orbital angular
momentum (OAM) play a crucial role in many applications. Here we present a
general study on the divergence of optical beams with OAM. We show that the
mean absolute value of the OAM imposes a lower bound on the value of the beam
divergence. We discuss our results for two different definitions of the
divergence, the so called rms or encircled-energy. The bound on the rms
divergence can be expressed as a generalized uncertainty principle, with
applications in long-range communication, microscopy and 2D quantum systems.Comment: RevTex, published versio
Measure for the Degree of Non-Markovian Behavior of Quantum Processes in Open Systems
We construct a general measure for the degree of non-Markovian behavior in
open quantum systems. This measure is based on the trace distance which
quantifies the distinguishability of quantum states. It represents a functional
of the dynamical map describing the time evolution of physical states, and can
be interpreted in terms of the information flow between the open system and its
environment. The measure takes on nonzero values whenever there is a flow of
information from the environment back to the open system, which is the key
feature of non-Markovian dynamics.Comment: 4 pages, 2 figures, published versio
Chapitre 4 • Tying surface seismic data
Approaches that are typically applied in deep exploration geophysics, combining different seismic and logging methods, can be technically adapted for certain geotechnical or hydrogeological surveys or some site characterizations in the framework of seismic hazard studies. Currently it is entirely feasible to implement this type of geophysical surveying if the situation requires. After reviewing the current state of knowledge regarding borehole measurements of subsurface shear velocities applied to the geotechnical field, this book illustrates the feasibility of carrying out vertical seismic profiles (VSPs) and logs in this field. This approach also illustrates the value of combining velocity measurements of formations provided by borehole seismic tools (VSP) and acoustic (sonic) tools. An innovative example of the application of borehole seismic and logging methods is then presented in the case study of a relatively near-surface (from 20 to 130 m) karst carbonate aquifer. It shows how a multi-scale description of the reservoir can be carried out by integrating the information provided by different 3D-THR surface seismic methods, full waveform acoustic logging, VSP with hydrophones, borehole optical televiewer and flow measurements. In this book the authors provide readers with guidelines to carry out these operations, in terms of acquisitions as well as processing and interpretation. Thus, users will be able to draw inspiration to continue transferring petroleum techniques and other innovative methods for use in near-surface studies
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