[Cosmo-torun] Re: Journal Club

Boud Roukema boud w astro.uni.torun.pl
Pią, 15 Paź 2004, 14:51:15 CEST

  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...


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

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