Quantization of minisuperspaces as ordinary gauge systems

Simple cosmological models are used to show that gravitation can be quantized as an ordinary gauge system if the Hamilton-Jacobi equation for the model under consideration is separable. In this situation, a canonical transformation can be performed such that in terms of the new variables the model has a linear and homogeneous constraint, and therefore canonical gauges are admissible in the path integral. This has the additional practical advantage that gauge conditions that do not generate Gribov copies are then easy to choose.Comment: 12 page

A Very Brief Introduction to Machine Learning With Applications to Communication Systems

Given the unprecedented availability of data and computing resources, there is widespread renewed interest in applying data-driven machine learning methods to problems for which the development of conventional engineering solutions is challenged by modelling or algorithmic deficiencies. This tutorial-style paper starts by addressing the questions of why and when such techniques can be useful. It then provides a high-level introduction to the basics of supervised and unsupervised learning. For both supervised and unsupervised learning, exemplifying applications to communication networks are discussed by distinguishing tasks carried out at the edge and at the cloud segments of the network at different layers of the protocol stack

Underwater acoustic detection of UHE neutrinos with the ANTARES experiment

The ANTARES Neutrino Telescope is a water Cherenkov detector composed of an array of approximately 900 photomultiplier tubes in 12 vertical strings, spread over an area of about 0.1 km^2 with an instrumented height of about 350 metres. ANTARES, built in the Mediterranean Sea, is the biggest neutrino Telescope operating in the northern hemisphere. Acoustic sensors (AMADEUS project) have been integrated into the infrastructure of ANTARES, grouped in small arrays, to evaluate the feasibility of a future acoustic neutrino telescope in the deep sea operating in the ultra-high energy regime. In this contribution, the basic principles of acoustic neutrino detection will be presented. The AMADEUS array of acoustic sensors will be described and the latest results of the project summarized.Comment: Proceedings of the 31st ICRC conference, 4 pages, 5 figure

Addendum to "Thin-shell wormholes supported by ordinary matter in Einstein-Gauss-Bonnet gravity"

Thin-shell wormholes are constructed starting from the exotic branch of Wiltshire spherically symmetric solution of Einstein-Gauss-Bonnet gravity. The energy-momentum tensor of the shell is studied, and it is shown that configurations supported by matter satisfying the energy conditions exist for certain values of the parameters. Differing from the previous result associated to the normal branch of Wiltshire solution, this is achieved for small positive values of the Gauss-Bonnet parameter and for vanishing charge.Comment: 8 pages, 2 figures; published in Phys. Rev. D (2011). Addendum to arXiv:0710.2041v3[gr-qc] (Phys. Rev. D {\bf 76}, 087502 (2007); D {\bf 77}, 089903(E) (2008)

Path integral for minisuperspaces and its relation with non equivalent canonical quantizations

The relation between a recently proposed path integral for minisuperspaces and different canonical quantizations is established. The step of the procedure where a choice between non equivalent theories is made is identified. Coordinates avoiding such a choice are found for a class of homogeneous cosmologies.Comment: 11 pages, to appear in Physics Letters

A Conic Algorithm for the Group Minimization Problem

A new algorithm for the group minimization problem (GP) is proposed. The algorithm can be broadly described as follows. A suitable relaxation of(GP) is defined, in which any feasible point satisfies the group equation but may have negative components. The feasible points of the relaxation are then generated in order of ascending costs by a variant of a well-known algorithm of Glover, and checked for non-negativity. The first non-negative point is an optimal solution of (GP). Advantages and disadvantages of the algorithm are discussed; in particular, the implementation of the algorithm (which can be easily extended so as to solve integer linear programming problems) does not require group arithmetics.

The Generational Turnover in Agriculture: Theoretical Problems and Empirical Evidences

The purpose of this study is to understand the causes determining the exit from the sector of young adults. Drawing from migration and succession theories, a number of factors, hypothesised to influence the decision, are tested using a Probit model. The findings lend support for the selectivity hypothesis: low incomes are negatively related with the propensity to stay in the sector. The exit of young could be related to the low earnings and to the preferences of individuals. The intergenerational transfer seems to be the result of an involvement in the farm activity.Generational-turnover, migration, transfer farms, Farm Management,