Multivariate medians and measure-symmetrization

We discuss two research areas dealing respectively with (1) a class of multivariate medians and (2) a symmetrization algorithm for probability measures.Comment: Published at http://dx.doi.org/10.1214/074921707000000201 in the IMS Lecture Notes Monograph Series (http://www.imstat.org/publications/lecnotes.htm) by the Institute of Mathematical Statistics (http://www.imstat.org

The Indirect Search for Dark Matter from the centre of the Galaxy with the Fermi LAT

Dark matter (DM) constitutes around a 25% of the Universe, while baryons only a 4%. DM can be reasonably assumed to be made of particles, and many theories (Super-symmetry, Universal Extra Dimensions, etc.) predict Weakly Interacting Massive Particles (WIMPs) as natural DM candidates at the weak scale. Self-annihilation (or decay) of WIMPs might produce secondary gamma-rays, via hadronization or as final state radiation. Since its launch in the 2008, the Large Area Telescope on-board of the Fermi gamma-ray Space Telescope has detected the largest amount of gamma-rays to date, in the 20MeV 300GeV energy range, allowing to perform a very sensitive indirect experimental search for DM (by means of high-energy gamma-rays). DM forms large gravitationally bounded structures, the halos, which can host entire galaxies, such as the Milky Way. The DM distribution in the central part of the halos is not experimentally know, despite a very large density enhancement might be present. As secondary gamma rays production is very sensitive to WIMP density, a very effective search can be performed from the regions where the largest density is expected. Therefore the information provided by the DM halo N-body simulations are crucial. The largest gamma-ray signal from DM annihilation is expected from the centre of the Galaxy. In the same region a large gamma-ray background is produced by bright discrete sources and the cosmic-rays interacting with the interstellar gas and the photons fields. Here we report an update of the indirect search for DM from the Galactic Center (GC).Comment: 6 pages, 2 figures. Invited talk presented at the Workshop "SciNeGHE 2010", September 8-10, 2010, Trieste, Italy. To appear in Il Nuovo Cimento C - Colloquia on physic

Role of heat generation and thermal diffusion during frontal photopolymerization

Frontal photopolymerization (FPP) is a rapid and versatile solidification process that can be used to fabricate complex three-dimensional structures by selectively exposing a photosensitive monomer-rich bath to light. A characteristic feature of FPP is the appearance of a sharp polymerization front that propagates into the bath as a planar traveling wave. In this paper, we introduce a theoretical model to determine how heat generation during photopolymerization influences the kinetics of wave propagation as well as the monomer-to-polymer conversion profile, both of which are relevant for FPP applications and experimentally measurable. When thermal diffusion is sufficiently fast relative to the rate of polymerization, the system evolves as if it were isothermal. However, when thermal diffusion is slow, a thermal wavefront develops and propagates at the same rate as the polymerization front. This leads to an accumulation of heat behind the polymerization front which can result in a significant sharpening of the conversion profile and acceleration of the growth of the solid. Our results also suggest that a novel way to tailor the dynamics of FPP is by imposing a temperature gradient along the growth directio

The 2004 Niger Food Crisis: What Role Can Price Discovery Play in Famine Early Warning Systems?

The 2005 food crisis centered in Niger received worldwide attention and extensive media coverage. Crops suffered from poor rainfall and were plagued by locusts throughout the growing season. Malnutrition flourished with the sudden disruption in food supplies. One-fifth of Niger's children suffered from moderate to severe forms of malnutrition by the summer of 2005. In an era of increased awareness and the introduction of famine early warning systems, the development community was left wondering why they were for the most part caught off guard by the food crisis. This paper tests whether market prices and price discovery could have played an active role in detecting the food crisis. Directed acyclic graphs are used to test whether price discovery mechanisms within Niger's millet markets were ahead of the early warning systems. Results suggest that as early as October 2005 markets in Arlit and the Dosso province had price anomalies that appeared to begin signaling the upcoming food crisis. This market based discovery came about two months earlier than the warnings issued by the regional early warning networks.Food Security and Poverty,

From the fuzzy disc to edge currents in Chern-Simons Theory

We present a brief review of the fuzzy disc, the finite algebra approximating functions on a disc, which we have introduced earlier. We also present a comparison with recent papers of Balachandran, Gupta and K\"urk\c{c}\"{u}o\v{g}lu, and of Pinzul and Stern, aimed at the discussion of edge states of a Chern-Simons theory.Comment: 8 pages, 6 figures, Talk presented at ``Space-time and Fundamental Interactions: Quantum Aspects'', conference in honour of A. P. Balachandran's 65th birthday. References added and one misprint correcte