8,809 research outputs found
The impact of the new Earth gravity models on the measurement of the Lense-Thirring effect
In this paper we use, in a preliminary way, the recently released EIGEN2
Earth gravity model, which is based on six months of data of CHAMP only, in
order to reassess the systematic error due to the mismodelling in the even
zonal harmonics of geopotential in the LAGEOS-LAGEOS II Lense-Thirring
experiment involving the nodes of both the LAGEOS satellites and the perigee of
LAGEOS II. The first results from the GGM01C Earth gravity model including the
first GRACE data are very promising.Comment: LaTeX, 15 pages, no figures, 4 tables. To appear in General
Relativity and Gravitatio
Forward-backward truncated Newton methods for convex composite optimization
This paper proposes two proximal Newton-CG methods for convex nonsmooth
optimization problems in composite form. The algorithms are based on a a
reformulation of the original nonsmooth problem as the unconstrained
minimization of a continuously differentiable function, namely the
forward-backward envelope (FBE). The first algorithm is based on a standard
line search strategy, whereas the second one combines the global efficiency
estimates of the corresponding first-order methods, while achieving fast
asymptotic convergence rates. Furthermore, they are computationally attractive
since each Newton iteration requires the approximate solution of a linear
system of usually small dimension
Tight entropic uncertainty relations for systems with dimension three to five
We consider two (natural) families of observables for systems with
dimension : the spin observables , and , and the
observables that have mutually unbiased bases as eigenstates. We derive tight
entropic uncertainty relations for these families, in the form
, where is the Shannon entropy of the
measurement outcomes of and is a constant. We show that most
of our bounds are stronger than previously known ones. We also give the form of
the states that attain these inequalities
State independent uncertainty relations from eigenvalue minimization
We consider uncertainty relations that give lower bounds to the sum of
variances. Finding such lower bounds is typically complicated, and efficient
procedures are known only for a handful of cases. In this paper we present
procedures based on finding the ground state of appropriate Hamiltonian
operators, which can make use of the many known techniques developed to this
aim. To demonstrate the simplicity of the method we analyze multiple instances,
both previously known and novel, that involve two or more observables, both
bounded and unbounded.Comment: 14 pages, 3 figure
Douglas-Rachford Splitting: Complexity Estimates and Accelerated Variants
We propose a new approach for analyzing convergence of the Douglas-Rachford
splitting method for solving convex composite optimization problems. The
approach is based on a continuously differentiable function, the
Douglas-Rachford Envelope (DRE), whose stationary points correspond to the
solutions of the original (possibly nonsmooth) problem. By proving the
equivalence between the Douglas-Rachford splitting method and a scaled gradient
method applied to the DRE, results from smooth unconstrained optimization are
employed to analyze convergence properties of DRS, to tune the method and to
derive an accelerated version of it
Multipartite steering inequalities based on entropic uncertainty relations
We investigate quantum steering for multipartite systems by using entropic
uncertainty relations. We introduce entropic steering inequalities whose
violation certifies the presence of different classes of multipartite steering.
These inequalities witness both steerable states and genuine multipartite
steerable states. Furthermore, we study their detection power for several
classes of states of a three-qubit system.Comment: 3 figure
From local to global deformation quantization of Poisson manifolds
We give an explicit construction of a deformation quantization of the algebra
of functions on a Poisson manifolds, based on Kontsevich's local formula. The
deformed algebra of functions is realized as the algebra of horizontal sections
of a vector bundle with flat connection.Comment: 16 pages. Reference and dedication added. Sign corrected, remark on
Poisson vector fields adde
Remote Tracking via Encoded Information for Nonlinear Systems
The problem addressed in this paper is to control a plant so as to have its
output tracking (a family of) reference commands generated at a remote location
and transmitted through a communication channel of finite capacity. The
uncertainty due to the presence of the communication channel is counteracted by
a suitable choice of the parameters of the regulator
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