Publications (23)
Approximations to the Fisher Information Metric of Deep Generative Models for Out-Of-Distribution Detection
Sam Dauncey, Chris Holmes, Christopher Williams +1
Likelihood-based deep generative models such as score-based diffusion models and variational autoencoders are state-of-the-art machine learning models approximating high-dimensiona…
Provably Stable Full-Spectrum Dispersion Relation Preserving Schemes
Christopher Williams, Kenneth Duru
The dispersion error is often the dominant error for computed solutions of wave propagation problems with high-frequency components. In this paper, we define and give explicit exam…
A Unified Framework for U-Net Design and Analysis
Christopher Williams, Fabian Falck, George Deligiannidis +3
U-Nets are a go-to, state-of-the-art neural architecture across numerous tasks for continuous signals on a square such as images and Partial Differential Equations (PDE), however t…
A Digital-Receiver for the Murchison Widefield Array
Thiagaraj Prabu, K. S. Srivani, D. Anish Roshi +55
An FPGA-based digital-receiver has been developed for a low-frequency imaging radio interferometer, the Murchison Widefield Array (MWA). The MWA, located at the Murchison Radio-ast…
Metropolis-Adjusted Diffusion Models
Kevin H. Lam, Tyler Farghly, Christopher Williams +3
Sampling from score-based diffusion models incurs bias due to both time discretisation and the approximation of the score function. A common strategy for reducing this bias is to a…
Score-Optimal Diffusion Schedules
Christopher Williams, Andrew Campbell, Arnaud Doucet +1
Denoising diffusion models (DDMs) offer a flexible framework for sampling from high dimensional data distributions. DDMs generate a path of probability distributions interpolating…
L-Edge Spectroscopy of Dilute, Radiation-Sensitive Systems Using a Transition-Edge-Sensor Array
Charles J. Titus, Michael L. Baker, Sang Jun Lee +24
We present X-ray absorption spectroscopy and resonant inelastic X-ray scattering (RIXS) measurements on the iron L-edge of 0.5 mM aqueous ferricyanide. These measurements demonstra…
An update to Allocating Time on Scientific Platforms in Outer Space using five cycles of JWST General Observer programs
Christopher Williams
Allocating Time on Scientific Platforms in Outer Space (Williams, 2025 in Research Policy) explored time allocated to astronomers to use the James Webb Space Telescope (JWST). It w…
Observing the carbon-climate system
David Schimel, Piers Sellers, Berrien Moore +41
Increases in atmospheric CO2 and CH4 result from a combination of forcing from anthropogenic emissions and Earth System feedbacks that reduce or amplify the effects of those emissi…
The Murchison Widefield Array: Design Overview
Colin J. Lonsdale, Roger J. Cappallo, Miguel F. Morales +45
The Murchison Widefield Array (MWA) is a dipole-based aperture array synthesis telescope designed to operate in the 80-300 MHz frequency range. It is capable of a wide range of sci…
Towards Stratified Space Learning: Linearly Embedded Graphs
Yossi Bokor, Katharine Turner, Christopher Williams
In this paper, we consider the simplest class of stratified spaces -- linearly embedded graphs. We present an algorithm that learns the abstract structure of an embedded graph and…
Upwind summation by parts finite difference methods for large scale elastic wave simulations in 3D complex geometries
Kenneth Duru, Frederick Fung, Christopher Williams
High-order accurate summation-by-parts (SBP) finite difference (FD) methods constitute efficient numerical methods for simulating large-scale hyperbolic wave propagation problems.…
MeerTRAP in the era of multi-messenger astrophysics
Kaustubh Rajwade, Benjamin Stappers, Christopher Williams +9
Real-time detections of transients and rapid multi-wavelength follow-up are at the core of modern multi-messenger astrophysics. MeerTRAP is one such instrument that has been deploy…
Generalised Sierpinski Triangles
Kyle Steemson, Christopher Williams
The family of Generalised Sierpinski triangles consist of the classical Sierpinski triangle, the previously well investigated Pedal triangle and two new triangular shaped fractal o…
SETIBURST: A Robotic, Commensal, Realtime Multi-Science Backend for the Arecibo Telescope
Jayanth Chennamangalam, David MacMahon, Jeff Cobb +9
Radio astronomy has traditionally depended on observatories allocating time to observers for exclusive use of their telescopes. The disadvantage of this scheme is that the data thu…
A Multi-Resolution Framework for U-Nets with Applications to Hierarchical VAEs
Fabian Falck, Christopher Williams, Dominic Danks +5
U-Net architectures are ubiquitous in state-of-the-art deep learning, however their regularisation properties and relationship to wavelets are understudied. In this paper, we formu…
The Pierre Auger Observatory: Contributions to the 33rd International Cosmic Ray Conference (ICRC 2013)
The Pierre Auger Collaboration, Alexander Aab, Pedro Abreu +495
Contributions of the Pierre Auger Collaboration to the 33rd International Cosmic Ray Conference, Rio de Janeiro, Brazil, July 2013
Commissioning of ALFABURST: initial tests and results
Kaustubh Rajwade, Jayanth Chennamangalam, Duncan Lorimer +7
Fast Radio Bursts (FRBs) are apparently one-time, relatively bright radio pulses that have been observed in recent years. The origin of FRBs is currently unknown and many instrumen…
ColoRadar: The Direct 3D Millimeter Wave Radar Dataset
Andrew Kramer, Kyle Harlow, Christopher Williams +1
Millimeter wave radar is becoming increasingly popular as a sensing modality for robotic mapping and state estimation. However, there are very few publicly available datasets that…
First Spectroscopic Imaging Observations of the Sun at Low Radio Frequencies with the Murchison Widefield Array Prototype
Divya Oberoi, Lynn D. Matthews, Iver H. Cairns +67
We present the first spectroscopic images of solar radio transients from the prototype for the Murchison Widefield Array (MWA), observed on 2010 March 27. Our observations span the…
Accurate simulations of nonlinear dynamic shear ruptures on pre-existing faults in 3D elastic solids with dual-pairing SBP methods
Kenneth Duru, Christopher Williams, Frederick Fung
In this paper we derive and analyse efficient and stable numerical methods for accurate numerical simulations of nonlinear dynamic shear ruptures on non-planar faults embedded in 3…
Optimal Operation of a Tidal Lagoon as a Flexible Source of Electricity
Tong Zhang, Christopher Williams, Reza Ahmadian +1
As the demand for electricity and the need for power systems flexibility grow, it is crucial to exploit more reliable and clean sources of energy to produce electricity when needed…
ALFABURST: A realtime fast radio burst monitor for the Arecibo telescope
Jayanth Chennamangalam, Aris Karastergiou, David MacMahon +7
Fast radio bursts (FRBs) constitute an emerging class of fast radio transient whose origin continues to be a mystery. Realizing the importance of increasing coverage of the search…