13,775 research outputs found
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
Conformal Truncation of Chern-Simons Theory at Large
We set up and analyze the lightcone Hamiltonian for an abelian Chern-Simons
field coupled to fermions in the limit of large using conformal
truncation, i.e. with a truncated space of states corresponding to primary
operators with dimension below a maximum cutoff . In both the
Chern-Simons theory, and in the model at infinite , we compute the
current spectral functions analytically as a function of and
reproduce previous results in the limit that the truncation
is taken to . Along the way, we determine how to preserve gauge
invariance and how to choose an optimal discrete basis for the momenta of
states in the truncation space.Comment: 32+25 pages, 8 figures. v2: updated ref
On Reduced Time Evolution for Initially Correlated Pure States
A new method to deal with reduced dynamics of open systems by means of the
Schr\"odinger equation is presented. It allows one to consider the reduced time
evolution for correlated and uncorrelated initial conditions.Comment: accepted in Open Sys. Information Dy
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