Category: Science
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Measuring line-of-sight shear with Einstein rings
Today I released a paper written in collaboration with Pierre Fleury, Julien Larena and Matteo Martinelli on how we can measure line-of-sight shear from Einstein rings. But what is line-of-sight shear, and why are we interested in measuring it in the first place? To answer these questions, let’s review the phenomenon of strong gravitational lensing.…
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The howling Universe
Before I moved from IFT to IPhT, I filmed a video all about what standard sirens are and why they’re useful for cosmology. The video is now on Youtube, in English with Spanish subtitles. Take a look!
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Thesis off-cuts: the reproducibility crisis in cosmology
As we frequently hear1, we’re now in the precision era of cosmology. What this really means is that we’re in the era of measuring things really well, and we’re getting really good at measuring things because we keep building ever more enormous and powerful telescopes. I remember attending the STFC Introductory Summer School on Astronomy…
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Thesis off-cuts: how special is our place in the Universe?
Thanks to many hundreds of people making dedicated observations of the sky over many decades, we know that the majority of our Universe is comprised of two substances: dark matter and dark energy. Dark matter is an unknown type of matter, referred to as “dark” because it does not interact electromagnetically, meaning that it doesn’t…
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The distance duality relation
The distance duality relation tells us how, assuming that photons propagate on null geodesics in a pseudo-Riemannian spacetime and that their number is conserved, luminosity and angular diameter distances are related, via where dL is the luminosity distance, dA the angular diameter distance and z the redshift. This relation was introduced by Etherington in 1933,…
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Thesis off-cuts: the ancient history of general relativity
I have recently been thinking a lot about what introductory and background material I want to include in my PhD thesis, as my self-imposed December deadline continues to hurtle towards me at an alarming speed. Concurrent with this thinking, I’ve also recently been enjoying a fantastic book called The Poincaré Conjecture by Donal O’Shea, all…
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Paper day! Madrid week seven
Today my first paper as first author came out on the arXiv! You can check it out here: https://arxiv.org/abs/2002.10449. In this work, we reconstruct a coupling function between dark matter and vacuum energy. Such models are generally motivated as solution to problems such as the Hubble tension, so we were keen to update our previous…
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Constraints on the interacting vacuum — geodesic CDM scenario
At the very end of February, I published my first paper. In this post, I want to provide a brief, non-technical overview of what we* were doing in this work and the results we found. The manuscript is currently under review at MNRAS but you can view the preprint here: http://www.arxiv.org/abs/1902.10694. The aim of this…
Natalie B. Hogg 