49,292 research outputs found
The linear request problem
We propose a simple approach to a problem introduced by Galatolo and
Pollicott, consisting in perturbing a dynamical system in order for its
absolutely continuous invariant measure to change in a prescribed way. Instead
of using transfer operators, we observe that restricting to an infinitesimal
conjugacy already yields a solution. This allows us to work in any dimension
and dispense from any dynamical hypothesis. In particular, we don't need to
assume hyperbolicity to obtain a solution, although expansion moreover ensures
the existence of an infinite-dimensional space of solutions.Comment: v2: the approach has been further simplified, only basic differential
calculus is in fact needed instead of basic PD
Optimal Cooperative MAC Protocol with Efficient Selection of Relay Terminals
A new cooperative protocol is proposed in the context of wireless mesh networks. The protocol implements ondemand
cooperation, i.e. cooperation between a source terminal
and a destination terminal is activated only when needed. In that case, only the best relay among a set of available terminals is re-transmitting the source message to the destination terminal. This typical approach is improved using three additional features. First, a splitting algorithm is implemented to select the best relay. This ensures a fast selection process. Moreover, the duration of the selection process is now completely characterized.
Second, only terminals that improve the outage probability of the direct link are allowed to participate to the relay selection. By this means, inefficient cooperation is now avoided. Finally, the destination terminal discards the source message when it fails to decode it. This saves processing time since the destination terminal does not need to combine the replicas of the source message: the one from the source terminal and the one from the best relay. We prove that the proposed protocol achieves an optimal performance in terms of Diversity-Multiplexing Tradeoff
(DMT)
A Pontryagin Maximum Principle in Wasserstein Spaces for Constrained Optimal Control Problems
In this paper, we prove a Pontryagin Maximum Principle for constrained
optimal control problems in the Wasserstein space of probability measures. The
dynamics, is described by a transport equation with non-local velocities and is
subject to end-point and running state constraints. Building on our previous
work, we combine the classical method of needle-variations from geometric
control theory and the metric differential structure of the Wasserstein spaces
to obtain a maximum principle stated in the so-called Gamkrelidze form.Comment: 35 page
Overview of MHz air shower radio experiments and results
In this paper, I present a review of the main results obtained in the last 10
years in the field of radio-detection of cosmic-ray air showers in the MHz
range. All results from all experiments cannot be reported here so that I will
focus on the results more than on the experiments themselves. Modern
experiments started in 2003 with CODALEMA and LOPES. In 2006, small-size
autonomous prototypes setup were installed at the Pierre Auger Observatory
site, to help the design of the Auger Engineering Radio Array (AERA). We will
discuss the principal aspects of the radio data analysis and the determination
of the primary cosmic ray characteristics: the arrival direction, the lateral
distribution of the electric field, the correlation with the primary energy,
the emission mechanisms and the sensitivity to the composition of the cosmic
rays.Comment: Proceedings of the ARENA2012 conference (Erlangen, Germany), to be
published in AIP Conference Proceeding
Observation of diffraction and measurement of the forward energy flow with the CMS detector
The observation of inclusive diffraction with the CMS detector at the LHC is
presented for centre-of-mass energies \sqrt s = 0.9 TeV and 2.36 TeV.
Diffractive events are selected by the presence of a Large Rapidity Gap in the
forward region of the CMS detector and uncorrected data are compared with Monte
Carlo simulations based on the event generators PYTHIA and PHOJET. The
measurement of the forward energy flow, in the pseudorapidity region 3.15 <
|\eta| < 4.9, is also presented at \sqrt s = 0.9 TeV, 2.36 TeV and 7 TeV.
Uncorrected data are compared with Monte Carlo simulations based on PYTHIA.Comment: 4 pages - 2 figures - proceedings of Physics at LHC 2010, 7-12 June
2010, DESY, Hambur
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