Jurek tells us about the prospects for constraining axion (aka ultralight aka fuzzy) dark matter with future 21cm intensity mapping survey such as SKA and HIRAX.

Axion models arising from specific energy scales predict that an axion with a given mass will only provide a certain fraction of the total dark matter. It seems plausible that with SKA we will be able to detect ultralight dark matter even if it arises from a GUT scale axion model. An observational noise model for SKA was included to make this claim, but as of yet no theoretical uncertainty is included in the calculation.

Paper: https://arxiv.org/abs/2003.09655

Omar tells us about the excellent quality lensing map he’s produced with the Atacama Cosmology Telescope collaboration. You honestly won’t believe how well this lensing map correlates with the cosmic infrared background (sorry about the clickbait). The map will be incredibly useful to cross-correlate with any dataset of tracers inside the relatively large window of ACT observations.

Omar also explains how he and the collaboration, for the first time, removed the annoying thermal Sunyaev–Zeldovich contamination that ordinarily produces a ~10% bias in sigma8 (and thus any other cosmological parameter correlated with sigma8).

Paper: https://arxiv.org/abs/2004.01139
Omar: http://www.damtp.cam.ac.uk/person/od261
Map page on NASA LAMBDA: https://lambda.gsfc.nasa.gov/product/act/act_dr4_derived_maps_get.cfm

Deanna tells us about what we could learn from future measurements of the spectral distortions in the CMB, as well as how spectral distortions complement current and future measurements of CMB anisotropies. She also discusses CLASS (v3.0), the code you can use to calculate predictions for both.

There is a guaranteed spectral distortion signal to detect within ΛCDM and the possibility to constrain many possible deviations, including primordial black holes and decaying dark matter. In fact, we can detect the signal even if the PBHs and/or decaying dark matter only make up one part in a million of the total dark matter!

Paper: https://arxiv.org/abs/1910.04619​
Deanna: https://www2.ulb.ac.be/sciences/physth/people_DCHooper.html
Twitter: https://twitter.com/DCHooper91​
CLASS: https://lesgourg.github.io/class_public/class.html

Julien tells us about the cosmological effects of different neutrino mass states (i.e. the same sum of masses, but different masses for each individual neutrino – e.g. “normal” vs “inverted”).

There are effects, but they’re all very small and not even the best future experiments will distinguish them.

Non-standard model neutrinos would still have interesting effects, but it seems that cosmology’s insight on the SM ones will be limited to the sum of the masses.

Paper: https://arxiv.org/abs/2003.03354
Julien: https://lesgourg.github.io/

Sesh tells us how the void-galaxy cross correlation provides information about cosmology via redshift space distortions and (importantly) the Alcock Paczynski effect. The information is independent of Baryon Acoustic Oscillations (BAO) and improves error bars by up to a factor of four. The combination of voids and BAO have very interesting insights into the Hubble discrepancy and the late-time acceleration of the Universe.

Speaker: Seshadri Nadathur

(the most relevant) Papers: https://arxiv.org/abs/2001.11044​ and https://arxiv.org/abs/1904.01030

Reference for cosmological perturbation theory: https://arxiv.org/abs/0809.4944​

Reference for Post Newtonian Theory

Paper: https://arxiv.org/abs/2001.00394

Graham tells us how Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background can be used to constrain the potential existence of particles beyond the Standard Model.

The focus is on light dark matter (masses less than 1GeV), which escapes direct detection bounds by being too light to kick nucleons hard enough and is most interesting to cosmology because it has precisely the masses relevant in the early universe processes we can “observe”, e.g. BBN.

Graham volunteered to give this talk on less than 36 hours notice, so huge thanks to him for pulling something together so quickly!!

Speaker: Graham White https://www.triumf.ca/theory/graham-white

Graham’s paper: https://arxiv.org/abs/2003.02273