## 6. Caveats and summary## 6.1. CaveatsOur low A simple answer to the discrepancy between direct We emphasize that we have only considered a particular type of cosmological scenario, although arguably the simplest; the results we have presented here are valid under the assumption of inflation-based, Gaussian adiabatic initial conditions in a critical density universe () with no cosmological constant. We have not considered any early reionization scenarios or gravitational wave contribution. We have also not included any hot dark matter. Our assumption can be considered very
restrictive since plausible values for in the
range can change the power spectrum
significantly. For example, the position of the Doppler peak,
is roughly proportional to
. Thus low , by pushing
higher may permit higher Reionization models can affect the power spectra significantly by
lowering the Doppler peak but this can be compensated by In paper I we took a brief look at flat- models. The supernovae results of Perlmutter et al. (1997) can constrain better than the CMB data. The combination of the CMB, BBN and supernovae constraints in flat- models yields . If gravitational waves or any other effect plays an important role
in CMB anisotropy formation, we expect that the inclusion of this
effect in the family of models tested, will improve the resulting
fits. However the inclusion of gravitational waves seems to make the
fits slightly worse without changing the location of the minimum
(Liddle et al. 1996b). Bond and Jaffe (1997) analyzed the combined DMR
(Bennett et al. 1996), South Pole (Gunderson et al. 1995) and
Saskatoon (Netterfield et al. 1997) data using signal-to-noise
eigenmodes. They looked at the parameters There may be extra-relativistic degrees of freedom (hot dark matter (HDM) or mixed dark matter (MDM)). de Bernardis et al. (1997) found that current CMB anisotrophy measurements cannot distinguish between CDM and MDM models. We agree with this assessment and add that HDM and CDM models also cannot usefully be distinguished with current CMB data. In addition to the ## 6.2. SummaryCMB measurements have become sensitive enough to constrain
cosmological parameters in a restricted class of models. The results
we have presented here are valid under the assumption of Gaussian
adiabatic initial conditions in a critical density
() universe with no cosmological constant. We
have explored the 4-dimensional parameter space of CMB constraints are independent of other cosmological tests of
these parameters and are thus particularly important. The fact that
reasonable values are obtained means that the
current CMB data are consistent with inflationary-based CDM models
with a low Hubble constant. In the context of the models considered,
the CMB results are consistent with four other independent
cosmological measurements but are in disagreement with more direct
measurements of © European Southern Observatory (ESO) 1998 Online publication: December 16, 1997 |