2,195 research outputs found
Anelastic sensitivity kernels with parsimonious storage for adjoint tomography and full waveform inversion
We introduce a technique to compute exact anelastic sensitivity kernels in
the time domain using parsimonious disk storage. The method is based on a
reordering of the time loop of time-domain forward/adjoint wave propagation
solvers combined with the use of a memory buffer. It avoids instabilities that
occur when time-reversing dissipative wave propagation simulations. The total
number of required time steps is unchanged compared to usual acoustic or
elastic approaches. The cost is reduced by a factor of 4/3 compared to the case
in which anelasticity is partially accounted for by accommodating the effects
of physical dispersion. We validate our technique by performing a test in which
we compare the sensitivity kernel to the exact kernel obtained by
saving the entire forward calculation. This benchmark confirms that our
approach is also exact. We illustrate the importance of including full
attenuation in the calculation of sensitivity kernels by showing significant
differences with physical-dispersion-only kernels
Fast Differential Emission Measure Inversion of Solar Coronal Data
We present a fast method for reconstructing Differential Emission Measures
(DEMs) using solar coronal data. On average, the method computes over 1000 DEMs
per second for a sample active region observed by the Atmospheric Imaging
Assembly (AIA) on the Solar Dynamics Observatory (SDO), and achieves reduced
chi-squared of order unity with no negative emission in all but a few test
cases. The high performance of this method is especially relevant in the
context of AIA, which images of order one million solar pixels per second. This
paper describes the method, analyzes its fidelity, compares its performance and
results with other DEM methods, and applies it to an active region and loop
observed by AIA and by the Extreme-ultraviolet Imaging Spectrometer (EIS) on
Hinode.Comment: 22 Pages, 11 Figures; submitted to The Astrophysical Journal. This
version (2) includes clarifications in the text and reflects improvements to
the DEM cod
Status and Future Perspectives for Lattice Gauge Theory Calculations to the Exascale and Beyond
In this and a set of companion whitepapers, the USQCD Collaboration lays out
a program of science and computing for lattice gauge theory. These whitepapers
describe how calculation using lattice QCD (and other gauge theories) can aid
the interpretation of ongoing and upcoming experiments in particle and nuclear
physics, as well as inspire new ones.Comment: 44 pages. 1 of USQCD whitepapers
Some improved inclusion methods for polynomial roots with Weierstrass' corrections
AbstractOne decade ago, the third order method without derivatives for the simultaneous inclusion of simple zeros of a polynomial was proposed in [1]. Following Nourein's idea [2], some modifications of this method with the increased convergence are proposed. The acceleration of convergence is attained by using Weierstrass' corrections without additional calculations, which provides a high computational efficiency of the modified methods. It is proved that their R-orders of convergence are asymptotically greater than 3.5. The presented interval methods are realized in circular complex arithmetic
Parallel software for lattice N=4 supersymmetric Yang--Mills theory
We present new parallel software, SUSY LATTICE, for lattice studies of
four-dimensional supersymmetric Yang--Mills theory with gauge
group SU(N). The lattice action is constructed to exactly preserve a single
supersymmetry charge at non-zero lattice spacing, up to additional potential
terms included to stabilize numerical simulations. The software evolved from
the MILC code for lattice QCD, and retains a similar large-scale framework
despite the different target theory. Many routines are adapted from an existing
serial code, which SUSY LATTICE supersedes. This paper provides an overview of
the new parallel software, summarizing the lattice system, describing the
applications that are currently provided and explaining their basic workflow
for non-experts in lattice gauge theory. We discuss the parallel performance of
the code, and highlight some notable aspects of the documentation for those
interested in contributing to its future development.Comment: Code available at https://github.com/daschaich/sus
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