Primordial black holes - The possibilities and pitfalls of studying something that may not exist
Marit Sandstad, NORDITA Stockholm
The idea that black holes of a wide range of masses could form from highly overdense regions in the very early universe has been around since the early seventies, when it prompted Steven Hawking to derive the theory of Hawking radiation. Since then, no primordial black holes have been seen, but as more accurate observations of the universe and our surrounding galaxies have been made they have been suggested as possible culprits for unexplained cosmic rays, the supermassive black holes in the centres of galaxies or the entirety of dark matter. However, as the unexplained cosmic rays turned out to be non-detections, so far all we have got at present are constraints on their abundance from various observations across nearly all possible scales. However, having only constraints might not be entirely a disadvantage. If the mechanisms proposed for the formation of primordial black holes is correct, their non-existence implies that the primordial power spectrum from inflation cannot have been too large. This is very interesting as... [abstract continued below]
[abstract, cont.] ... the constraints on these from primordial black holes could potentially cover yield information on much more of the inflationary potential than what is covered by the cosmic microwave background observations. However, the present understanding of primordial black hole formation is far from detailed enough to give any detailed power spectrum constraints at present.In this talk I will try to introduce the idea of primordial black holes, which constraints we have, how we can treat them, and a bit about the conclusions we can and can not draw from this.