Primordial Black Hole DM - II (Lecture 2) by Yacine Ali Haimoud

PROGRAM

LESS TRAVELLED PATH OF DARK MATTER: AXIONS AND PRIMORDIAL BLACK HOLES (ONLINE)

ORGANIZERS: Subinoy Das (IIA, Bangalore), Koushik Dutta (IISER, Kolkata / SINP, Kolkata), Raghavan Rangarajan (Ahmedabad University) and Vikram Rentala (IIT Bombay)

DATE: 09 November 2020 to 13 November 2020

VENUE: Online

The existence of dark matter (DM) has been inferred from its gravitational interactions, yet the identity of the dark matter particles remains completely unknown. The dominant candidate for DM over the last 30 years has been Weakly Interacting Massive Particles (WIMPs). However, despite extensive underground (direct), telescope (indirect), and collider searches, dedicated experiments have not found any evidence of WIMPs. Meanwhile, several astrophysical small-scale structure and cosmological hints might be an indication that DM has non-gravitational interactions that cannot easily be explained with vanilla WIMPs.

This online workshop on the Less Travelled Path of Dark Matter (LTPDM) will bring together particle physicists and cosmologists from all over the world to address current trends in DM searches, focused on axions and primordial black holes, and map the way forward. The program will also include a school, with lectures addressed to students and postdocs, familiarizing them with new and advanced concepts.

We plan to have a longer physical workshop on dark matter, with a larger perspective, in the near future once the current global pandemic crisis has subsided.

0:00:00 Primordial Black Hole DM - II (Lecture 2)
0:00:11 C-Accretion
0:01:55 Accretion rate M
0:02:12 Radiative efficiency
0:02:52 Efficiency of deposition
0:04:20 Effect on free-electron fraction...
0:04:54 ... and CMB anisotropies
0:05:40 Limits from Planck
0:06:39 Potential reach if accretion was disk-like
0:07:31 Summary of lecture 1
0:14:59 CMB and GW constraints on Primordial Black Holes
0:15:06 Plan of this lecture
0:15:55 1- Basics of gravitational waves
0:17:36 TT (t, r) = = Q.j(t -~]
0:20:08 The gravitational-wave landscape
0:22:03 Linearly polarized plane wave
0:23:10 Basics of pulsar timing arrays
0:25:30 For each pulsar p: Time residual Rp(t) = TOA - timing model(t)
0:30:40 NANOGrav 12.5-year results
0:32:06 For each pulsar p:
0:32:14 Basics of pulsar timing arrays
0:34:02 Questions?
0:34:10 2-A- GWs induced at second-order by small-scale density perturbations
0:36:34 A very simple estimate
0:42:33 2-B- Formation of PBH binaries in the late Universe (Bird et al. 2016)
0:45:33 =Cross-section for capture through GW radiation:
0:50:43 2-C- Formation of PBH binaries in the early Universe (Nakamura et al. 1997)
0:51:52 Once a pair decouples from the Hubble flow, it falls almost head-on
0:52:31 If PBH binaries are undisturbed between formation and merger
0:53:05 PBH binaries typically start with a very small angular momentum.
0:54:20 Summary of lecture 2
1:00:49 NANOGrav 12.5-year results
1:04:17 Two aspects to this problem