My main research interests focus on problems in numerical analysis and the study of waves. In more detail I have worked on the following topics:

Numerical methods for evolution equations

A large part of my current ongoing research concerns the development and study of efficient numerical methods for time evolution equations. I have a particular interest in the study of dispersive equations which arise in the study of water waves, atmospheric models and relativistic wave equations in particle physics. In this work I study splitting methods, resonance-based methods and exponential integrators, and seek to better understand their properties including convergence rates for low-regularity data, geometric structure preservation, cost and their efficient numerical implementation.

Analysis of collocation methods for Fredholm integral equations

In collaboration with Prof. Daan Huybrechs at KU Leuven, we are studying the theoretical properties of collocation methods for integral equations that arise in wave scattering. In particular we are interested in understanding the effect of the location and the number of collocation points on the error of the approximate solution. This work is motivated by results from signal analysis and approximation theory, where it was found that oversampling allows for improved robustness to redundancies in the approximation spaces. The understanding of the strengths and limitations of collocation methods is especially relevant to practical applications since in collocation methods are often easier to implement and cheaper to compute than their traditionally stabler counterpart, the Galerkin method.

Computational high-frequency wave propagation

High-frequency wave scattering problems are beyond the reach of most conventional methods for numerical wave propagation due to the infeasible computational cost that large frequencies would require. As a result a significant amount of recent research has focussed on the development of hybrid numerical-asymptotic (HNA) methods, which are robust even for large frequencies and achieve in many cases a near frequency independent solution time. The underlying idea is to incorporate physical knowledge into numerical schemes to enhance quality and efficiency in the high-frequency regime, while preserving the precision and flexibility of a grid based approach. An essential step in boundary HNA methods is the numerical evaluation of highly oscillatory integrals. My current work focusses on the development of (provably) efficient quadrature methods for the specific types of oscillators and singularities encountered in boundary integral methods for computational wave scattering.

Wiener-Hopf method and applications

The Wiener-Hopf method is a very successful technique for solving certain boundary value problems which are relevant in acoustics, electromagnetic theory, hydrodynamics and elasticity. Typically the method exploits analyticity properties of Fourier half-line transforms combined with Liouville’s theorem to arrive at an explicit form of solution. I am currently applying this method to a specific model problem which arises from the need to understand noise development and propagation in turbofan engines.

The Wiener-Hopf method is a very successful technique for solving certain boundary value problems which are relevant in acoustics, electromagnetic theory, hydrodynamics and elasticity. Typically the method exploits analyticity properties of Fourier half-line transforms combined with Liouville’s theorem to arrive at an explicit form of solution. I am currently applying this method to a specific model problem which arises from the need to understand noise development and propagation in turbofan engines.

Symmetric low regularity integrators via a forest formula.
Alama Bronsard, Y., Bruned, Y., Maierhofer, G., Schratz, K.
In preparation.

Symplectic low-regularity integrators for the cubic non-linear Schrödinger equation.
Maierhofer, G., Schratz, K.
In preparation.

An accelerated Levin–Clenshaw–Curtis method for the evaluation of highly oscillatory integrals.
Maierhofer, G., Iserles, A.
In preparation.

Long-time error bounds of low-regularity integrators for nonlinear Schrödinger equations.
Feng, Y., Maierhofer, G., Schratz, K.
Under review.
Download: preprint

Numerical integration of Schrödinger maps via the Hasimoto transform.
Banica, V., Maierhofer, G., Schratz, K.
Under review.
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Bridging the gap: symplecticity and low regularity on the example of the KdV equation.
Maierhofer, G., Schratz, K.
Under review.
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Recursive moment computation in Filon methods and application to high-frequency wave scattering in two dimensions
Maierhofer, G., Iserles, A., Peake, N.
IMA Journal of Numerical Analysis.
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An analysis of least-squares oversampled collocation methods for compactly perturbed boundary integral equations in two dimensions.
Maierhofer, G., Huybrechs, D.
Journal of Computational and Applied Mathematics (2022).
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Convergence analysis of oversampled collocation boundary element methods in 2D
Maierhofer, G., Huybrechs, D.
Advances in Computational Mathematics (2022).
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Acoustic and hydrodynamic power of wave scattering by an infinite cascade of plates in mean flow
Maierhofer, G., Peake, N.
Journal of Sound and Vibration (2021).
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Wave scattering by an infinite cascade of non-overlapping blades
Maierhofer, G., Peake, N.
Journal of Sound and Vibration (2020).
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Learning the Sampling Pattern for MRI
Sherry, F., Benning, M., De los Reyes, J. C., Graves, M. J., Maierhofer, G., Williams, G., Schönlieb, C.-B. and Ehrhardt, M.
IEEE Transactions on Medical Imaging (2020).
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Mirror, Mirror, on the Wall, Who’s Got the Clearest Image of Them All? — A Tailored Approach to Single Image Reflection Removal
Heydecker, D., Maierhofer, G., Aviles-Rivero, A. I., Fan, Q., Chen, D., Schönlieb, C.-B. and Süsstrunk, S.
IEEE Transactions on Image Processing (2019).
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Peekaboo - Where are the Objects? Structure Adjusting Superpixels.
Maierhofer, G., Heydecker, D., Aviles-Rivero, A. I., Alsaleh, S. M. and Schönlieb, C.-B.
25th IEEE International Conference on Image Processing (2018).
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An extension of standard Latent Dirichlet Allocation to multiple corpora
Foster, A., Li, H., Maierhofer, G., Shearer, M.
SIAM Undergraduate Research Online Volume 9 (2016).
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Geometric Measure of Arens Irregularity
Hernandez Palomares, R., Hu, E., Maierhofer, G. A., Rao, P.
Fields Institute for Research in Mathematical Sciences (2015).
Download: published version