22,524 research outputs found
The Montage Image Mosaic Service: Custom Image Mosaics On-Demand
The Montage software suite has proven extremely useful as a general engine for reprojecting, background matching, and mosaicking astronomical image data from a wide variety of sources. The processing algorithms support all common World Coordinate System (WCS) projections and have been shown to be both astrometrically accurate and flux conserving. The background âmatchingâ algorithm does not remove background flux but rather finds the best compromise background based on all the input and matches the individual images to that. The Infrared Science Archive (IRSA), part of the Infrared Processing and Analysis Center (IPAC) at Caltech, has now wrapped the Montage software as a CGI service and provided a compute and request management infrastructure capable of producing approximately 2 TBytes / day of image mosaic output (e.g. from 2MASS and SDSS data). Besides the basic Montage engine, this service makes use of a 16-node LINUX cluster (dual processor, dual core) and the ROME request management software developed by the National Virtual Observatory (NVO). ROME uses EJB/database technology to manage user requests, queue processing and load balance between users, and managing job monitoring and user notification. The Montage service will be extended to process userdefined data collections, including private data uploads
Spinless photon dark matter from two universal extra dimensions
We explore the properties of dark matter in theories with two universal extra
dimensions, where the lightest Kaluza-Klein state is a spin-0 neutral particle,
representing a six-dimensional photon polarized along the extra dimensions.
Annihilation of this 'spinless photon' proceeds predominantly through Higgs
boson exchange, and is largely independent of other Kaluza-Klein particles. The
measured relic abundance sets an upper limit on the spinless photon mass of 500
GeV, which decreases to almost 200 GeV if the Higgs boson is light. The
phenomenology of this dark matter candidate is strikingly different from
Kaluza-Klein dark matter in theories with one universal extra dimension.
Elastic scattering of the spinless photon with quarks is helicity suppressed,
making its direct detection challenging, although possible at upcoming
experiments. The prospects for indirect detection with gamma rays and
antimatter are similar to those of neutralinos. The rates predicted at neutrino
telescopes are below the sensitivity of next-generation experiments.Comment: 22 pages. Figure 7 corrected, leading to improved prospects for
direct detection. Some clarifying remarks include
New Results for Diffusion in Lorentz Lattice Gas Cellular Automata
New calculations to over ten million time steps have revealed a more complex
diffusive behavior than previously reported, of a point particle on a square
and triangular lattice randomly occupied by mirror or rotator scatterers. For
the square lattice fully occupied by mirrors where extended closed particle
orbits occur, anomalous diffusion was still found. However, for a not fully
occupied lattice the super diffusion, first noticed by Owczarek and Prellberg
for a particular concentration, obtains for all concentrations. For the square
lattice occupied by rotators and the triangular lattice occupied by mirrors or
rotators, an absence of diffusion (trapping) was found for all concentrations,
except on critical lines, where anomalous diffusion (extended closed orbits)
occurs and hyperscaling holds for all closed orbits with {\em universal}
exponents and . Only one point on these critical lines can be related to a
corresponding percolation problem. The questions arise therefore whether the
other critical points can be mapped onto a new percolation-like problem, and of
the dynamical significance of hyperscaling.Comment: 52 pages, including 18 figures on the last 22 pages, email:
[email protected]
Radiative corrections to the Casimir force and effective field theories
Radiative corrections to the Casimir force between two parallel plates are
considered in both scalar field theory of one massless and one massive field
and in QED. Full calculations are contrasted with calculations based on
employing ``boundary-free'' effective field theories. The difference between
two previous results on QED radiative corrections to the Casimir force between
two parallel plates is clarified and the low-energy effective field theory for
the Casimir effect in QED is constructed.Comment: 17 pages, revte
HySIA: Tool for Simulating and Monitoring Hybrid Automata Based on Interval Analysis
We present HySIA: a reliable runtime verification tool for nonlinear hybrid
automata (HA) and signal temporal logic (STL) properties. HySIA simulates an HA
with interval analysis techniques so that a trajectory is enclosed sharply
within a set of intervals. Then, HySIA computes whether the simulated
trajectory satisfies a given STL property; the computation is performed again
with interval analysis to achieve reliability. Simulation and verification
using HySIA are demonstrated through several example HA and STL formulas.Comment: Appeared in RV'17; the final publication is available at Springe
Coulomb interactions within Halo Effective Field Theory
I present preliminary results of effective field theory applied to nuclear
cluster systems, where Coulomb interactions play a significant role.Comment: Talk given at the 20th European Conference on Few-Body Problems in
Physics, Pisa, Italy, September 10-14, 200
Exploring universality in nuclear clusters with Halo EFT
I present results and highlight aspects of halo EFT to loosely bound systems
composed of nucleons and alpha particles, with emphasis on Coulomb
interactions.Comment: 3 pages, 2 figures, talk given at the 21th European Conference on
Few-Body Problems in Physics, Salamanca, Aug. 29th - Sep. 3rd, 201
The Scattering of Electromagnetic Waves from Two-Dimensional Randomly Rough Penetrable Surfaces
An accurate and efficient numerical simulation approach to electromagnetic
wave scattering from two-dimensional, randomly rough, penetrable surfaces is
presented. The use of the M\"uller equations and an impedance boundary
condition for a two-dimensional rough surface yields a pair of coupled
two-dimensional integral equations for the sources on the surface in terms of
which the scattered field is expressed through the Franz formulas. By this
approach, we calculate the full angular intensity distribution of the scattered
field that is due to a finite incident beam of -polarized light. We
specifically check the energy conservation (unitarity) of our simulations (for
the non-absorbing case). Only after a detailed numerical treatment of {\em
both} diagonal and close-to-diagonal matrix elements is the unitarity condition
found to be well-satisfied for the non-absorbing case (), a
result that testifies to the accuracy of our approach.Comment: Revtex, 4 pages, 2 figure
On the non-equivalence of Lorenz System and Chen System
In this paper, we prove that the Chen system with a set of chaotic parameters
is not smoothly equivalent to the Lorenz system with any parameters
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