**7.10. The End of Cosmology?**

When the WMAP results came out at the end of this school I was asked
"So is this the end of cosmology? We know all the cosmological
parameters...what is there left to do?
To what precision does one really want to know the value of
_{m}?"
In his talk, Brian Schmidt asked the rhetorical question: "We know
Hubble's parameter to about 10%, is that
good enough?" Well, now we know it to about 5%. Is that good enough?
Obviously the more precision on any one parameter the better, but we are
talking about constraining an entire
model of the universe defined by a network of parameters.
As we determine 5 parameters to less than 10%, it enables us to turn a
former upper limit on another parameter into
a detection. For example we still have only upper limits on the tensor
to scalar ratio *r* and
this limits our ability to test inflation. We only have an upper limit on
the density of neutrinos
_{}
and this limits our ability to go beyond the standard model
of particle physics. And we have only a tenuous detection of the running
of the scalar spectral index
*dn* / *dlnk* 0,
and this limits our ability to constrain inflaton potential model
builders.

We still know next to nothing about
_{} ~
0.7, most of the Universe.
CDM is an
observational result that has yet to be
theoretically confirmed. From a quantum field theoretic point of view
_{} ~
0.7 presents a huge problem. It is a quantum term in
a classical equation. But the last time such a
quantum term appeared in a classical equation, Hawking radiation
was discovered. A similar revelation may be in the offing.
The Friedmann equation will eventually be seen as a low energy approximation
to a more complete quantum model in much the same way that
1/2 *mv*^{2} is a low energy approximation to *pc*.

Inflation solves the origin of structure problem with quantum fluctuations,
and this is just the beginning of quantum contributions to cosmology.
Quantum cosmology is opening up many new doors.
Varying coupling constants are expected at high energy
(Wilczek 1999)
and *c* variation, *G* variation,
(fine structure
constant) variation, and
_{}
variation (quintessence) are being discussed.
We may be in an ekpyrotic universe or a cyclic one
(Steinhardt & Turok 2002).
The topology of the Universe is also alluringly fundamental
(Levin 2002).
Just as we were getting precise estimates of the parameters
of classical cosmology,
whole new sets of quantum cosmological parameters are being proposed.
The next high profile goal of cosmology may be trying to figure out if
we are living in a multiverse.
And what, pray tell, is the connection between inflation and dark matter?