New Views

Today I arrived in Chicago for two days at New Views of the Cosmos, a new Kavli conference in honor of Dave Schramm. I saw talks about dark matter (Frieman), neutrinos (Conrad), the composition of cosmic rays (Hoerandel), neutrino dark matter (Abazajian), accelerator production of dark matter (Baltz), positrons at the Galactic Center (Yuksel) and many others.

Something that interested me greatly was what Jedamzik said about discrepancies (relative to big-bang nucleosynthesis) in the ⁷Li and ⁶Li abundances relative to predictions (⁷Li is too low by a factor of 3 to 4, and ⁶Li is too high by a lot). This used to be thought to be a problem with stars (maybe ⁷Li is somehow depleted or destroyed) and cosmic rays (maybe ⁶Li is produced entirely by CR spallation), but now neither mechanism seems to be working well, especially since both abundances show little system-to-system scatter and a weak dependence on overall metallicity. This might be a window into new physics, such as energy injection at MeV at BBN (decaying SUSY particles?) to spallate ⁷Li and ⁴He to ³He (which then makes ⁶Li). As Jedamzik noted, Dave Schramm would have liked the idea that BBN anomalies could be used to discover new physics. (Later, Dave Tytler also discussed this a bit).

At lunch, Blandford and I discussed finding cosmic strings in HST data by searching for patterns of multiple imaging. Nice, and possible!