Dr. Luke Hart

@ Lake Windermere, Lake District

Hello, my name is Luke and welcome to my website :-) I am currently working as a software engineer for TNEI Services Ltd., focussing on the deployment and development of the power systems software IPSA. Previously I was a cosmologist for the Jodrell Bank Center of Astrophysics with Jens Chluba, studying the cosmic microwave background, recombination and spectral distortions.

Originally I was studying tension quantifying methods for cosmological datasets alongside Richard Battye as a student intern within the University of Manchester. In 2016, I attained my Master of Physics at the University of Manchester under the supervision of Sarah Bridle, Joe Zuntz and Michael Troxel. In 2020, I attained my Ph.D in cosmology under the supervision of Jens Chluba.

As a researcher, I mainly focused on recombination physics, the cosmic microwave background and fundamental physics. You can see my research interests in more detail here I’ve worked on research with statistical methods such as principal component analysis and maximum likelihood estimators. This culminated in the development of my first software package FEARec++ which produces functional principal components for recombination variations as well as predicting how the components can reconstruct noise constraints.

Since August 2021, I have been the software lead of IPSA. This has involved modification and improvement of the iteration/engineering code written in Fortran, the UI and partial-engine interface code developed in C++ and the scripting capabilities/solution building API in Python. In our team, we developed many new features for IPSA 2.10.0 which was released in May 2022: including updated IEEE arc flash calculations, a new Windows-10 modernised UI aesthetic, developed capability for networks parsed in CIM (Common Information Model) and the ability to quickly build units of energy storage for capability such as P28 studies.

selected publications

MNRAS

Using the cosmological recombination radiation to probe early dark energy and fundamental constant variations

Hart, Luke, and Chluba, Jens

Monthly Notices of the Royal Astronomical Society Dec 2022

Abs arXiv PDF

The cosmological recombination radiation (CRR) is one of the guaranteed spectral distortion signals from the early Universe. The CRR photons from hydrogen and helium pre-date the last scattering process and as such allow probing physical phenomena in the pre-recombination era. Here we compute the modifications to the CRR caused by early dark energy models and varying fundamental constants. These new physics examples have seen increased recent activity in connection with the Hubble tension, motivating the exploratory study presented here. The associated CRR responses are spectrally-rich but the level of the signals is small. We forecast the possible sensitivity of future spectrometers to these effects. Our estimates demonstrate that the CRR directly depends to changes in the expansion history and recombination physics during the pre-recombination era. However, futuristic sensitivities are required for spectrometer-only constraints that are competitive with other cosmological probes. Nevertheless, measurements of the CRR can directly reach into phases that otherwise remain inaccessible, highlighting the potential these types of observations could have as a probe of the early Universe. A combination with Planck data further shows that a synergistic approach is very promising.
MNRAS

Varying fundamental constants principal component analysis: additional hints about the Hubble tension

Hart, Luke, and Chluba, Jens

Monthly Notices of the Royal Astronomical Society Oct 2021

Abs arXiv PDF

Varying fundamental constants (VFC) [e.g., the fine-structure constant, αEM] can arise in numerous extended cosmologies. Through their effect on the decoupling of baryons and photons during last scattering and reionisation, these models can be directly constrained using measurements of the cosmic microwave background (CMB) temperature and polarization anisotropies. Previous investigations focused mainly on time-independent changes to the values of fundamental constants. Here we generalize to time-dependent variations. Instead of directly studying various VFC parameterizations, we perform a model-independent principal component analysis (PCA), directly using an eigenmode decomposition of the varying constant during recombination. After developing the formalism, we use Planck 2018 data to obtain new VFC limits, showing that three independent VFC modes can be constrained at present. No indications for significant departures from the standard model are found with Planck data. Cosmic variance limited modes are also compared and simple forecasts for The Simons Observatory are carried out, showing that in the future improvements of the current constraints by a factor of ≃3 can be anticipated. Our modes focus solely on VFC at redshifts z≥300. This implies that they do not capture some of the degrees of freedom relating to the reionisation era. This aspect provides important new insights into the possible origin of the Hubble tension, hinting that indeed a combined modification of recombination and reionisation physics could be at work. An extended PCA, covering both recombination and reionisation simultaneously, could shed more light on this question, as we emphasize here.