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Title: Rapid evaluation of two-dimensional retarded time integrals

Abstract

We present two methods for rapid evaluation of two-dimensional retarded time integrals. For example, such integrals arise as the z = 0 trace U( t, x, y, 0) of a solution U( t, x, y, z) to 3 + 1 wave equation U = –2 f( t, x, y)δ( z) forced by a ‘‘sheet source’’ at z = 0. The spatial Fourier transform of a two-dimensional retarded time integral involves a temporal convolution with the zeroth order Bessel function J 0( t). Appealing to work by Alpert, Greengard, and Hagstrom and by Xu and Jiang on rational approximation in the Laplace-transform domain, our first method relies on approximation of J 0( t) as a sum of exponential functions. We achieve approximations with double precision accuracy near t ≃ 0, and maintain single precision accuracy out to T ≃ 10 8. Our second method involves evolution of the 3 + 1 wave equation in a ‘‘thin block’’ above the sheet, adopting the radiation boundary conditions of Hagstrom, Warburton, and Givoli based on complete plane wave expansions. We review their technique, present its implementation for our problem, and present new results on the nonlocal spacetime form of radiation boundary conditions. Our methodsmore » are relevant for the sheet-bunch formulation of the Vlasov–Maxwell system, although here we only test methods on a model problem, a Gaussian source following an elliptical orbit. Here, our concluding section discusses the complexity of both methods in comparison with naive evaluation of a retarded-time integral.« less

Authors:
 [1];  [1];  [1];  [1]
  1. Univ. of New Mexico, Albuquerque, NM (United States)
Publication Date:
Research Org.:
Univ. of New Mexico, Albuquerque, NM (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1511845
Alternate Identifier(s):
OSTI ID: 1416621; OSTI ID: 1530304
Grant/Contract Number:  
FG02-99ER41104; FG03-99ER41104; FG-99ER41104; AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Computational and Applied Mathematics
Additional Journal Information:
Journal Volume: 324; Journal Issue: C; Journal ID: ISSN 0377-0427
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION; Retarded time integral; Rational approximation; Radiation boundary conditions; Initial boundary value problem; Vlasov–Maxwell system; Accelerator beam physics

Citation Formats

Bizzozero, D. A., Ellison, J. A., Heinemann, K., and Lau, S. R. Rapid evaluation of two-dimensional retarded time integrals. United States: N. p., 2017. Web. doi:10.1016/j.cam.2017.04.007.
Bizzozero, D. A., Ellison, J. A., Heinemann, K., & Lau, S. R. Rapid evaluation of two-dimensional retarded time integrals. United States. doi:10.1016/j.cam.2017.04.007.
Bizzozero, D. A., Ellison, J. A., Heinemann, K., and Lau, S. R. Wed . "Rapid evaluation of two-dimensional retarded time integrals". United States. doi:10.1016/j.cam.2017.04.007. https://www.osti.gov/servlets/purl/1511845.
@article{osti_1511845,
title = {Rapid evaluation of two-dimensional retarded time integrals},
author = {Bizzozero, D. A. and Ellison, J. A. and Heinemann, K. and Lau, S. R.},
abstractNote = {We present two methods for rapid evaluation of two-dimensional retarded time integrals. For example, such integrals arise as the z = 0 trace U(t, x, y, 0) of a solution U(t, x, y, z) to 3 + 1 wave equation U = –2f(t, x, y)δ(z) forced by a ‘‘sheet source’’ at z = 0. The spatial Fourier transform of a two-dimensional retarded time integral involves a temporal convolution with the zeroth order Bessel function J0(t). Appealing to work by Alpert, Greengard, and Hagstrom and by Xu and Jiang on rational approximation in the Laplace-transform domain, our first method relies on approximation of J0(t) as a sum of exponential functions. We achieve approximations with double precision accuracy near t ≃ 0, and maintain single precision accuracy out to T ≃ 108. Our second method involves evolution of the 3 + 1 wave equation in a ‘‘thin block’’ above the sheet, adopting the radiation boundary conditions of Hagstrom, Warburton, and Givoli based on complete plane wave expansions. We review their technique, present its implementation for our problem, and present new results on the nonlocal spacetime form of radiation boundary conditions. Our methods are relevant for the sheet-bunch formulation of the Vlasov–Maxwell system, although here we only test methods on a model problem, a Gaussian source following an elliptical orbit. Here, our concluding section discusses the complexity of both methods in comparison with naive evaluation of a retarded-time integral.},
doi = {10.1016/j.cam.2017.04.007},
journal = {Journal of Computational and Applied Mathematics},
number = C,
volume = 324,
place = {United States},
year = {2017},
month = {4}
}

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Figures / Tables:

Figure 1 Figure 1: Retarded-time integration in terms of bunch history. In the right-hand figure the $z$-coordinate normal to the sheet is suppressed.

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