4,626 research outputs found
Nonnegative polynomials and their Carath\'eodory number
In 1888 Hilbert showed that every nonnegative homogeneous polynomial with
real coefficients of degree in variables is a sum of squares if and
only if (quadratic forms), (binary forms) or (ternary
quartics). In these cases, it is interesting to compute canonical expressions
for these decompositions. Starting from Carath\'eodory's Theorem, we compute
the Carath\'eodory number of Hilbert cones of nonnegative quadratic and binary
forms.Comment: 9 pages. Discrete & Computational Geometry (2014
Spectrum Trading: An Abstracted Bibliography
This document contains a bibliographic list of major papers on spectrum
trading and their abstracts. The aim of the list is to offer researchers
entering this field a fast panorama of the current literature. The list is
continually updated on the webpage
\url{http://www.disp.uniroma2.it/users/naldi/Ricspt.html}. Omissions and papers
suggested for inclusion may be pointed out to the authors through e-mail
(\textit{[email protected]})
Analysis of cloud storage prices
Cloud storage is fast securing its role as a major repository for both
consumers and business customers. Many companies now offer storage solutions,
sometimes for free for limited amounts of capacity. We have surveyed the
pricing plans of a selection of major cloud providers and compared them using
the unit price as the means of comparison. All the providers, excepting Amazon,
adopt a bundling pricing scheme; Amazon follows instead a block-declining
pricing policy. We compare the pricing plans through a double approach: a
pointwise comparison for each value of capacity, and an overall comparison
using a two-part tariff approximation and a Pareto-dominance criterion. Under
both approaches, most providers appear to offer pricing plans that are more
expensive and can be excluded from a procurement selection in favour of a
limited number of dominant providers.Comment: 17 pages, 17 figures, 17 reference
Distinctiveness Centrality in Social Networks
The determination of node centrality is a fundamental topic in social network
studies. As an addition to established metrics, which identify central nodes
based on their brokerage power, the number and weight of their connections, and
the ability to quickly reach all other nodes, we introduce five new measures of
Distinctiveness Centrality. These new metrics attribute a higher score to nodes
keeping a connection with the network periphery. They penalize links to
highly-connected nodes and serve the identification of social actors with more
distinctive network ties. We discuss some possible applications and properties
of these newly introduced metrics, such as their upper and lower bounds.
Distinctiveness centrality provides a viewpoint of centrality alternative to
that of established metrics
- …