On 21-09-2019 14:50, Philip Thrift wrote:
On Saturday, September 21, 2019 at 7:32:43 AM UTC-5, John Clark wrote:
On Sat, Sep 21, 2019 at 7:29 AM Bruce Kellett <bhkel...@gmail.com>
wrote:
_> Has Carroll forgotten about effective theories? Even QFT is
just an "effective theory". We use classical approximations to
quantum mechanics because they work -- not for ideological or
philosophical reasons._
Read the book, Carroll devote several chapters to those exact
topics.
John k Clark
I doubt Sean has any better "approach" that combines QM and GR than
any of the many others.
But if you go on a well-marketed book tour with a well-written book
(and fiction can be well-written) then you gan get the
science-interested public to think that it is the best approach that
exists today.
Combining QM with GR is trivial, there is no problem here. The problem
is with regularizing quantum gravity. A non-renormalizable theory is not
per se wrong, just inconvenient for physicists who want to do
computations with it. If you write down some arbitrary field theory
formulated on a lattice and you consider the effective field theory at
some large length scale, the non-renormalizable terms become very small.
So, the fact that gravity is very weak could well be due to it being
non-renormalizable. This is a point that's sometimes made in books on
renormalization group methods as applied in statistical physics. In that
context non-renormalizable terms are a normal occurrence.
Saibal
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