On Jun 25, 2:01*pm, Jos Bergervoet wrote:
On 6/25/2012 9:08 AM, Eric Gisse wrote:

On Jun 24, 12:10 pm, Jos Bergervoet wrote:
* ...
Zero. The only black holes that have been detected are ones that are
stellar mass or higher.

Same question. How are we sure they are *not* primordial?

Basically the size of the accretion disk is a rough indicator, and a
more quantitative notion is that iron gets ionized as it gets sucked
down and emits some lines in the ~5-6KeV range that allow you to get a
pretty good bead on the strength of the gravitational field there.

There's nothing out there that is known to be consistent with being
less than a solar mass.

This still doesn't answer it.. Why can't those black
holes of more than one solar mass be primordial?

--
Jos

In principle there's nothing but in practice black holes are only
found by their accretion which tends to happen in bound systems of
somesort which preclude being here from day one.

OTOH the line blurs a bit when you think about supermassive black
holes but my notion is "if it doesn't predate decoupling, it isn't
primordial."