Loop quantum gravity

[jeffery...@mail.com]

What do you think of the following article about loop quantum gravity in
Physics Today?

http://www.physicstoday.org/resource/1/phtoad/v66/i3/p35_s1

At the end, he argues that loop quantum gravity is "falsifiable",
implying that it is more falsifiable than string theory. Do you think
that loop quantum gravity is more "falsifiable" than string theory?

He also leaves out that since loop quantum gravity is Lorentz violating,
that implies it is also CPT violating.

http://jefferywinkler.com

[Sylvia Else]

Not being a subscriber, I can't read the paper.

Still, I wonder at your inference that he's saying that it is more
falsifiable that string theory. I question whether levels of
falsifiability actually exist, beyond falsifiable and not falsifiable.
One theory may have been developed to the point where it makes more
potentially falsifiable predictions than another, but that's not the
same thing. All of a theory's known testable predictions could be
experimentally verified, while the theory itself is actually false.

Sylvia.

[Alfred Einstead]

On Apr 6, 4:38 pm, Sylvia Else <syl...@not.at.this.address> wrote:
> Not being a subscriber, I can't read the paper.

I see that Bojowald has been quite prolific on the preprint server as
of late. You may get what you're looking for (and a lot more) by
accessing these articles, instead.

http://arxiv.org/abs/1302.5695 Quantum matter in quantum space-time
http://arxiv.org/abs/1212.5150 A loop quantum multiverse?
http://arxiv.org/abs/1212.4773 Deformed General Relativity

There's more besides this, but this gives you the general idea of
where he's coming from.

Everything's gone cliquish these days, and you have all these small,
easily-distinguishable niches running around. I notice that Kiefer is
an Author #2 on one of the preprint papers. So, this is probably one
of the "Kiefer people".

If you want an assessment of where LQG is these days, you need only
look at who's in this clique and (more significantly) who's left it.
As is also the case with string theory, the operative question is (and
always has been): "does it lead to deep changes in the foundations of
the field that enable one to successfully approach problems that are
currently "swept under the rug" and called "solved because we can't
see them anymore"? Or does it amplify the language, ideas, and
conventions of the previous century whose continued use has only led
to an impasse when dealing with the issue of developing a consistent,
unified foundation for the field?

Experimental checks are nice. But let's first get the house in order
and the ducks in a row before presuming to line them up for target
practice. As long as any field, methodology or formalism continues to
use (or even take for granted) the "regularization" or "infinite
renormalization"[1] step, it has not succeeded in explaining anything.

Both LQG and string theory take the infinite renormalization step as a
given. Therefore, they do not qualify for the label of "new
foundation", but only for label "20th century writ large".

Note:
[1] The emphasis is on "infinite" not "renormalization". Finite
renormalization is an entirely different matter, which has no bearing
on the issue at hand.