Witam, Agnieszka: i think what Bartek and i answered to your question about OGLE/MACHO/EROS was wrong - if MACHOs are mirror matter, then there is no problem with violating nucleosynthesis. As far as nucleosynthesis constraints are concerned, Omega_MACHO *could* be as big as 0.20, provided that it is *not* baryonic. So it seems to me, anyway.
So the possible argument against MACHOs being mirror matter and providing Omega_MACHO=0.20 (Omega_m - Omega_baryon = 0.25 - 0.05 =0.20) depends on which observational/Galaxy-structure analysis of OGLE/MACHO/EROS you believe.
E.g. http://de.arxiv.org/abs/astro-ph/0303100 Afonso et al 2003 say expected "optical depths" towards the Galactic Bulge are something like 4e-7 for "ordinary" stars and 8e-7 if there is a population of brown dwarfs, probably just citing these from Paczynski 1991 and Griest 1991.
What they find is about 9e-7, while the first OGLE results (1994) found 33e-7 which is about 4 times higher, and Afonso et al say they can't calculate an optical depth for OGLE II because the experimental parameters (detection efficiency) are not published.
Even if Afonso et al are right, there's still the possibility that the Om_b/Om_b' \approx 0.5 is right (instead of 0.2) and that there are at least two different non-baryonic types of dark matter in significant quantities (the Universe often turns up out complicated than we expect, at least in terms of new particles...), in which case Omega_mirror \approx 0.1 instead of 0.05 and it could be the MACHO population.
So probably the challenge is to see if there is some experimental way of distinguishing a baryonic MACHO from a mirror-baryonic MACHO...
pozdr boud
On Wed, 13 Oct 2004, Agnieszka Slowikowska wrote:
Witam,
zapraszam na kolejny Journal Club, ktory odbedzie sie w najblizszy piatek o godzinie 10.15 w sali seminaryjnej kamieniczki CAMK.
Boud Roukema opowie nam o "Mirror matter and the 7 yr DAMA NaI results: has DM already been detected?".
Pozdrawiam, aga