Archive for Jacques Delabrouille

Post-Planck Cosmology: Day 1

Posted in The Universe and Stuff with tags , , , on October 9, 2017 by telescoper

Well, I’m just back to my guest flat from a pleasant birthday party for one of the conference organizers, Tarun Souradeep, is now in the same decade as me! I don’t have time to write about all the talks today so apologies to anyone I don’t mention by name. I also got called away to have tea with an old friend so missed the final session and consequently missed the last session. I can’t do that again tomorrow as I’m chairing the last session tomorrow (including a presentation from Paul Steinhardt via Skype).

Also, I forgot to take my camera to today’s session so here are a couple of pics that I’ve stolen without permission from the Director of IUCAA, Somak Raychaudhury showing Francois Bouchet and Jacques Delabrouille who gave the first two talks.

Here are some brief notes.

Francois Bouchet delivered an expert summary on the state of cosmology up to and including the Planck mission. He started by saying out that before the discovery of the cosmic microwave background, cosmology was a `semi-crackpot subject’ and went on to show how much the field has moved on: there are no longer any semi-crackpots in cosmology. Three particularly interesting points he made on his grand tour were: (i) that the `inflationary prediction’ that the spectral index of primordial density fluctuations is not that n=1 (which was argued for before inflation by Harrison and Zeld’dovich) but n=0.96, and that the difference between these numbers is very significant; (ii) there aren’t enough independent modes in the (2D) CMB to improve current limits on non-Gaussianity by much so we will have to use (3D) galaxy clustering data; and (iii) the apparent `tension’ in measurements of the Hubble constant is not solely a problem with the CMB (he mentioned this paper in particular.

Next up, Jacques Delabrouille spoke about future CMB space missions. Unfortunately none of the three putative missions currently on the table (LiteBIRD, CORE and PIXIE) has been selected for Phase A by the relevant space agencies. Although not officially dead, any of these will need to find international partners to proceed, and none will be launched for at least a decade. The current generation of CMB scientists will therefore probably have to rely on ground-based data for the immediate future. However, he was ambitious in the science goals for future missions: `we want to measure it all!’

We then had a series of talks about various matters, including the resurgence of interest in spectral distortions of the CMB that I blogged about recently.

Anyway, that will do for this evening. I’ll try to post about Day 2 tomorrow, though it is the conference dinner in the evening so I may not be in a fit state!