Abstract

The purpose of this paper is to study a Helmholtz problem with a spectral fractional Laplacian, instead of the standard Laplacian. Recently, it has been established that such a fractional Helmholtz problem better captures the underlying behavior in geophysical electromagnetics. We establish the well-posedness and regularity of this problem. We introduce a hybrid spectral-finite element approach to discretize it and show well-posedness of the discrete system. In addition, we derive a priori discretization error estimates. Finally, we introduce an efficient solver that scales as well as the best possible solver for the classical integer-order Helmholtz equation. We conclude with several illustrative examples that confirm our theoretical findings.

Keywords

  1. fractional Helmholtz equation
  2. spectral fractional Laplacian
  3. error analysis

MSC codes

  1. 65N12
  2. 65N22
  3. 65N30
  4. 65N38
  5. 65N55

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Supplementary Material


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Index of Supplementary Materials

Title of paper: A Fast Solver for the Fractional Helmholtz Equation

Authors: Harbir Antil, Marta D'Elia, Christian Glusa, Bart Van Bloemen Waanders, and Chester J. Weiss

File: supp.pdf

Type: PDF

Contents: Detailed proofs of auxiliary results

References

1.
M. Ainsworth and C. Glusa, Hybrid finite element--spectral method for the fractional Laplacian: Approximation theory and efficient solver, SIAM J. Sci. Comput., 40 (2018), pp. A2383--A2405, https://doi.org/10.1137/17M1144696.
2.
H. Antil, E. Otárola, and A. J. Salgado, Optimization with respect to order in a fractional diffusion model: Analysis, approximation and algorithmic aspects, J. Sci. Comput., 77 (2018), pp. 204--224, https://doi.org/10.1007/s10915-018-0703-0.
3.
H. Antil and J. Pfefferer, A Short MATLAB Implementation of Fractional Poisson Equation with Nonzero Boundary Conditions, Tech. report, George Mason University, Fairfax, VA, 2017.
4.
H. Antil, J. Pfefferer, and S. Rogovs, Fractional operators with inhomogeneous boundary conditions: Analysis, control, and discretization, Commun. Math. Sci., 16 (2018), pp. 1395--1426, https://doi.org/10.4310/CMS.2018.v16.n5.a11.
5.
H. Antil and C. N. Rautenberg, Sobolev spaces with non-Muckenhoupt weights, fractional elliptic operators, and applications, SIAM J. Math. Anal., 51 (2019), pp. 2479--2503, https://doi.org/10.1137/18M1224970.
6.
A. Bermúdez, P. Gamallo, and R. Rodríguez, Finite element methods in local active control of sound, SIAM J. Control Optim., 43 (2004), pp. 437--465, https://doi.org/10.1137/S0363012903431785.
7.
A. Bonito and J. E. Pasciak, Numerical approximation of fractional powers of elliptic operators, Math. Comp., 84 (2015), pp. 2083--2110, https://doi.org/10.1090/S0025-5718-2015-02937-8.
8.
J. H. Bramble, Multigrid Methods, Pitman Res. Notes Math. Ser. 294, Longman Scientific & Technical, Harlow, John Wiley & Sons, New York, 1993.
9.
L. Caffarelli and L. Silvestre, An extension problem related to the fractional Laplacian, Comm. Partial Differential Equations, 32 (2007), pp. 1245--1260.
10.
A. Capella, J. Dávila, L. Dupaigne, and Y. Sire, Regularity of radial extremal solutions for some non-local semilinear equations, Comm. Partial Differential Equations, 36 (2011), pp. 1353--1384, https://doi.org/10.1080/03605302.2011.562954.
11.
A. Ern and J.-L. Guermond, Theory and Practice of Finite Elements, Appl. Math. Sci. 159, Springer, New York, 2004, https://doi.org/10.1007/978-1-4757-4355-5.
12.
G. Grubb, Regularity of spectral fractional Dirichlet and Neumann problems, Math. Nachr., 289 (2016), pp. 831--844.
13.
R. A. Horn and C. R. Johnson, Matrix Analysis, Cambridge University Press, Cambridge, 2012.
14.
T. Kato, Note on fractional powers of linear operators, Proc. Japan Acad., 36 (1960), pp. 94--96.
15.
W. McLean, Strongly Elliptic Systems and Boundary Integral Equations, Cambridge University Press, Cambridge, 2000.
16.
J. M. Melenk and S. Sauter, Wavenumber explicit convergence analysis for Galerkin discretizations of the Helmholtz equations, SIAM J. Numer. Anal. 49 (2011), pp. 1210--1243, https://doi.org/10.1137/090776202.
17.
J. M. Melenk and S. Sauter, Convergence analysis for finite element discretizations of the Helmholtz equation with Dirichlet-to-Neumann boundary conditions, Math. Comp., 79 (2010), pp. 1871--1914.
18.
S. A. Molchanov and E. Ostrovskii, Symmetric stable processes as traces of degenerate diffusion processes, Theory Probab. Appl., 14 (1969), pp. 128--131.
19.
R. H. Nochetto, E. Otárola, and A. J. Salgado, A PDE approach to fractional diffusion in general domains: A priori error analysis, Found. Comput. Math., 15 (2015), pp. 733--791.
20.
S. A. Sauter and C. Schwab, Boundary Element Methods, Springer Ser. Comput. Math. 39, Springer-Verlag, Berlin, 2011, translated and expanded from the 2004 German original, https://doi.org/10.1007/978-3-540-68093-2.
21.
L. R. Scott and S. Zhang, Finite element interpolation of nonsmooth functions satisfying boundary conditions, Math. Comp., 54 (1990), pp. 483--493.
22.
R. Servadei and E. Valdinoci, On the spectrum of two different fractional operators, Proc. Roy. Soc. Edinburgh Sect. A, 144 (2014), pp. 831--855.
23.
J. Sprekels and E. Valdinoci, A new type of identification problems: Optimizing the fractional order in a nonlocal evolution equation, SIAM J. Control Optim., 55 (2017), pp. 70--93, https://doi.org/10.1137/16M105575X.
24.
P. R. Stinga and J. L. Torrea, Extension problem and Harnack's inequality for some fractional operators, Comm. Partial Differential Equations, 35 (2010), pp. 2092--2122.
25.
L. Tartar, An Introduction to Sobolev Spaces and Interpolation Spaces, Lect. Notes Unione Mat. Ital. 3, Springer, Berlin, UMI, Bologna, 2007.
26.
C. J. Weiss, B. G. van Bloemen Waanders, and H. Antil, Fractional operators applied to geophysical electromagnetics, Geophys. J. Int., 220 (2020), pp. 1242--1259.
27.
L. Zhu and H. Wu, Preasymptotic error analysis of CIP-FEM and FEM for Helmholtz equation with high wave number. Part II: $hp$ version, SIAM J. Numer. Anal., 51 (2013), pp. 1828--1852, https://doi.org/10.1137/120874643.

Information & Authors

Information

Published In

cover image SIAM Journal on Scientific Computing
SIAM Journal on Scientific Computing
Pages: A1362 - A1388
ISSN (online): 1095-7197

History

Submitted: 25 February 2020
Accepted: 12 January 2021
Published online: 26 April 2021

Keywords

  1. fractional Helmholtz equation
  2. spectral fractional Laplacian
  3. error analysis

MSC codes

  1. 65N12
  2. 65N22
  3. 65N30
  4. 65N38
  5. 65N55

Authors

Affiliations

Bart van Bloemen Waanders

Funding Information

Sandia National Laboratories https://doi.org/10.13039/100006234 : DE-NA0003525
National Science Foundation https://doi.org/10.13039/100000001 : DMS-1818772, DMS-1913004

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