cosmology, scattering

In the morning, Mustafa Amin (MIT) gave a short talk about consequences of potential shapes in inflation for the period between the end of inflation and the beginning of the normal physics of standard-model particles. In the afternoon, Joel Primack (Santa Cruz) gave the astrophysics seminar on the extragalactic background light. For the latter, some of the constraints come from the absorption of high-energy photons from blazars. I asked about scattering—when I was a boy I was told that whenever there is absorption there is always scattering, was that wrong?—but he implied in his answer that the scattering mechanisms are very different from the absorbing mechanisms. I am confused! If you do the classical calculation of a plane wave intercepted by finite absorbers, you have to get scattering too, just as a consequence of physical optics. Maybe my reader will un-confuse me.

Between talks, Jagannath and I discussed the implications of recent literature developments for our paper on fitting streams. I think we have a plan to re-scope it.