My thoughts on what the Hubble tension really is, based on George Efstathiou’s “To H0 or not to H0?“, arXiv:2103.08723.
After disappearing for a week, this week I cover three papers discussing why reducing the sound horizon is necessary but not sufficient to solve the Hubble tension, how to probe gravitational waves using astrometry, and whether unparticles might have something to do with dark energy. As of this week I’ve also decided to start including plots from the respective papers, where necessary, in my summaries, as a good plot is worth a thousand words. Enjoy!
This week I cover a proposal to confirm the possible Dirac nature of neutrinos exploiting a subtle correlation between cosmological and terrestrial measurements, how to determine the sound horizon and H0 from BAO independently of the details of recombination, and a possible interpretation of the recent detection of the stochastic gravitational wave background at nHz frequencies by NANOGrav as being due to cosmic strings. Enjoy and have a nice weekend!
This week’s entry discusses two papers on shadows (one in relation to superradiance, and one in relation to naked singularities), and one paper addressing the important question of how model-independent BAO measurements are. Following the discussion of the third paper, I have included a long-ish bonus discussion on what my opinion is on this whole BAO model-independence business (some readers might find the discussion provocative, if so that was not my intention). Enjoy!
