My thoughts on what the Hubble tension really is, based on George Efstathiou’s “To H0 or not to H0?“, arXiv:2103.08723.
This week’s entry discusses a new measurement of the Hubble constant from Type II Supernovae, a map from Poincaré gauge theories to bi-scalar-tensor theories useful for cosmological applications, and a map between fluid and field approaches to interacting dark energy valid at the background and first-order perturbation level.
This week’s entry discusses the effects of the Hubble constant on the growth of high-redshift supermassive black holes, a new test of General Relativity from galaxy-galaxy lensing and clustering amplitudes, and a new WIMP dark matter production mechanism from conformal or disformal couplings to ultra-light scalars.
This week’s entry features the return of the Hubble tension, the first discussion in this blog on the lensing anomaly (Alens tension), and for the second time a discussion on cross-correlations between ultra-high energy cosmic rays and large-scale structure (this time done on real data). As a totally random observation, all three papers discussed this week feature authors which already appeared earlier in this blog. Misha Ivanov already featured on Week 7 (#2), Julien Lesgourgues already featured on Week 11 (again #1!), Marc Kamionkowski already featured on Week 16 (#3), Avi Loeb already featured on Week 15 (#3), and Pavel Motloch already featured with another single-author paper on Week 17 (#3). And no, this is a totally random observation and I’m not trying to imply anything about these authors or the quality of their work (you might want to read my welcome post disclaimers once again), but rather you might start to see some interesting patterns regarding the type of works I am interested in. Enjoy!
This week’s installment covers a new Bayesian analysis code (particularly designed for cosmological studies!) called Cobaya, a gravitational wave constraint on the number π (yes, you’ve read correctly) as a null test of General Relativity, and a new proposal for holographic dark energy based on John Barrow’s recent COVID-19-inspired proposal for fractal structure on a black hole event horizon. Enjoy!
This week’s entry features a futuristic way for obtaining a direct geometrical measurement of the Hubble constant using the so-called cosmic secular parallax, a study on the possibility of cross-correlating ultra-high energy cosmic rays and large-scale structure and what we would learn from this cross-correlation, and the second-best constraint on the tidal charge of brane-world black holes from the shadow of M87* detected by the Event Horizon Telescope. Enjoy!
This week’s entry features a new proposal by Ed Witten for hunting Planet 9, a study on signatures of scattering between dark energy and visible matter in cosmological observations, and new constraints on light dark matter produced from primordial black hole evaporation. As usual, comments are welcome, and hope you enjoy!
With a week of delay due to Italian bureaucracy-induced commitments, my Week 17 summaries are now out. There is a new entry in terms of topics covered, i.e. the thorny issue of naturalness in particle physics and cosmology (besides two papers covering limits on the duration of inflation, and independent inferences of the baryon energy density from Planck). As always, comments are very welcome!
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!
This week’s entry focuses on observational tests of a specific class of string inflationary models (which allow to set limits on the fundamental microscopic string parameters), observational tests of naked singularity spacetimes from their shadows and the continuum spectrum emitted from accretion disks, and finally a study addressing the interesting question of what was the maximum initial temperature of the Universe in the radiation domination epoch. Happy Easter to those readers who celebrate it!
