16 research outputs found
Fundamental limits to learning closed-form mathematical models from data
Given a finite and noisy dataset generated with a closed-form mathematical
model, when is it possible to learn the true generating model from the data
alone? This is the question we investigate here. We show that this
model-learning problem displays a transition from a low-noise phase in which
the true model can be learned, to a phase in which the observation noise is too
high for the true model to be learned by any method. Both in the low-noise
phase and in the high-noise phase, probabilistic model selection leads to
optimal generalization to unseen data. This is in contrast to standard machine
learning approaches, including artificial neural networks, which are limited,
in the low-noise phase, by their ability to interpolate. In the transition
region between the learnable and unlearnable phases, generalization is hard for
all approaches including probabilistic model selection
Silicon Photomultiplier Research and Development Studies for the Large Size Telescope of the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) is the the next generation facility of
imaging atmospheric Cherenkov telescopes; two sites will cover both
hemispheres. CTA will reach unprecedented sensitivity, energy and angular
resolution in very-high-energy gamma-ray astronomy. Each CTA array will include
four Large Size Telescopes (LSTs), designed to cover the low-energy range of
the CTA sensitivity (20 GeV to 200 GeV). In the baseline LST design, the
focal-plane camera will be instrumented with 265 photodetector clusters; each
will include seven photomultiplier tubes (PMTs), with an entrance window of 1.5
inches in diameter. The PMT design is based on mature and reliable technology.
Recently, silicon photomultipliers (SiPMs) are emerging as a competitor.
Currently, SiPMs have advantages (e.g. lower operating voltage and tolerance to
high illumination levels) and disadvantages (e.g. higher capacitance and cross
talk rates), but this technology is still young and rapidly evolving. SiPM
technology has a strong potential to become superior to the PMT one in terms of
photon detection efficiency and price per square mm of detector area. While the
advantage of SiPMs has been proven for high-density, small size cameras, it is
yet to be demonstrated for large area cameras such as the one of the LST. We
are working to develop a SiPM-based module for the LST camera, in view of a
possible camera upgrade. We will describe the solutions we are exploring in
order to balance a competitive performance with a minimal impact on the overall
LST camera design.Comment: 8 pages, 5 figures. In Proceedings of the 34th International Cosmic
Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions
at arXiv:1508.0589
Search for gamma-ray emission from supernova remnants with the Fermi/LAT and MAGIC telescopes
Vegeu ircresum1de1.pd
Search for gamma-ray emission from supernova remnants with the Fermi/LAT and MAGIC telescopes
Vegeu ircresum1de1.pd
A Bayesian machine scientist to aid in the solution of challenging scientific problems
Closed-form, interpretable mathematical models have been instrumental for advancing our understanding of the world; with the data revolution, we may now be in a position to uncover new such models for many systems from physics to the social sciences. However, to deal with increasing amounts of data, we need “machine scientists� that are able to extract these models automatically from data. Here, we introduce a Bayesian machine scientist, which establishes the plausibility of models using explicit approximations to the exact marginal posterior over models and establishes its prior expectations about models by learning from a large empirical corpus of mathematical expressions. It explores the space of models using Markov chain Monte Carlo. We show that this approach uncovers accurate models for synthetic and real data and provides out-of-sample predictions that are more accurate than those of existing approaches and of other nonparametric methods
Gammapy: An open-source Python package for gamma-ray astronomy
International audienceIn the past decade imaging atmospheric Cherenkov telescope arrays such as H.E.S.S., MAGIC, VERITAS, as well as the Fermi-LAT space telescope have provided high quality images and spectra of the γ-ray universe. Currently the γ-ray community is preparing to build the nextgeneration Cherenkov Telecope Array (CTA), which will be operated as an open observatory. Gammapy v0.3 (available at https://github.com/gammapy/gammapy under the open-source BSD license) is a new in-development Astropy affiliated package for high-level analysis and simulation of astronomical γ-ray data. It is built on the scientific Python stack (Numpy, Scipy, matplotlib and scikit-image) and makes use of other open-source astronomy packages such as Astropy, Sherpa and Naima to provide a flexible set of tools for γ-ray astronomers. We present an overview of the Gammapy scope, development workflow, status, structure, features, application examples and goals. We would like Gammapy to become a community-developed project and a place of collaboration between scientists interested in γ-ray astronomy with Python. Contributions welcome