From: sarfatti@well.sf.ca.us (Jack Sarfatti)
Subject: re: Carlip's comments on The Force that is not a force.
Organization: Whole Earth 'Lectronic Link
Date: Tue, 5 Jan 1993 03:13:42 GMT


John Archibald Wheeler taught us:
Mass without mass.
Charge without charge.
It from bit.

I add the quantum connection which is
Force without force.
as well as
Cause without cause.
Physics without physics.
Sense without sense.

*Sarfatti comments* on:
General comment. Steve did not read what I wrote very carefully. He hits me
with a lot of very good and hard questions that no one knows the answers to
regarding quantum gravity. But that is irrelevant to my very modest claim
that the quantum gravity cut off for quantum electrodynamics in a classical
metric makes quantum electrodynamics divergence-free i nthe ultra-violet
limit (not infra-red).

From: carlip@landau.ucdavis.edu (Steve Carlip)
Newsgroups: sci.physics,alt.sci.physics.new-
theories,sci.skeptic,alt.paranormal,
alt.alien.visitors,alt.conspiracy
Subject: Re: The New Physics of "The Force" of "Star Wars".
Date: 4 Jan 93 17:46:17 GMT
Followup-To: sci.physics
Organization: Physics, UC Davis

I'm probably going to regret this follow-up, but there's enough almost-
physics here that I can't resist...

*I've got you under my spell!"*

In article <C0B988.A5D@well.sf.ca.us> sarfatti@well.sf.ca.us (Jack
Sarfatti) writes:
>1. Looking at Feynman's classic 1949 papers on quantum electrodynamics
>(QED) from the 1992 perspective of quantum gravity suggests that the
>"ultra-violet catastrophe" is easily avoided by using the Planck length
>(i.e. 10^-5 grams = 10^-33 cm etc.) as the high-momentum/short wavelength
>cut-off.

Easily?  Then you should by all means publish your results.

*I plan to when I'm finished. Is there any law against using this new
medium for brain-storming, refining half-baked ideas. Why do you want to
crush free inquiry. This is not the Physical Review!  What would have
happened to Feynman if Wheeler tried to crush him at the beginning? I feel
sorry for your research students if you have any!*

The speculation that Planck length effects cut off divergences in quantum
field theory has been around for years, and a lot of interesting work has
been done, but no one has yet managed to find a way to consistently
implement such a cutoff.

*Why not? Please amplify on this. What do you mean by "consistently"?*

Do you have a way to preserve approximate Lorentz invariance at low
energies?

*Do you mean that if we violate Lorentz invariance at a scale of 10^-33 cm
in one frame that there will be another frame in which this violation shows
up on a larger scale? I thought the length contracts not expands. Where are
you coming from. Please explain the problem here.*

Do you know how to avoid the divergences of quantum gravity itself?

*Do you? Does anyone? I have an idea though, that the problem is in the
technical constraint of causality - which does break down in quantum
gravity.  How about a review of the intrinsic divergence of quantum
gravity. What causes it?

I never claimed to solve the divergence of quantum gravity. I only claim
that the QED of Feynman et-al has no divergence (for classical gravity) if
we stick in the cut-off for QED at the Planck scale and start with zero
bare mass and zero bare charge for all particle fields.*

Is your cutoff at exactly the Planck length (no extra factors of two or
pi)?  Why?

*Good question. The self-consistency condition should be that the bare
mass, charge etc. are exactly zero (not infinite) and all observed mass and
charge is self-created out of the virtual fluctuations of the vacuum
starting at the Planck scale. The factors of 2 etc. are determined by this
self-consistency.

What variables are you applying this cutoff to?  In general relativity,
you can't just Fourier transform between position and momentum space, so a
momentum cutoff is not necessarily equivalent to a length cutoff.

*My remarks were only for quantum electrodynamics in flat-spacetime! The
vacuum fluctuations in flat spacetime would still cut off at the Planck
length. In curved space-time we will need some new "wavelet" sort of
variables that reduce to momentum and position for flat limit.

How do you deal with overlapping loops in Feynman diagrams?  Etc... The
idea that quantum gravity cuts off divergences is a very nice one, and I
hope it's true, but we're going to have to know a hell of a lot more than
we do now before this becomes more than an interesting conjecture.

*Agreed, but you are attributing to me more than I intended. The key idea
is that in flat QED the bare stuff is zero etc.*

>QED is "semi-classical" in that the spacetime metric is classical only the
>photon and electron fields are quantized.  The metric quantum fluctuates
so>strongly at the cut-off that Lorentz symmetry breaks down. There is no
>smoothness, no differentiability there.  The geometry of quantum gravity
is >fractal! Note that in semiclassical QED the worldlines of photons and
>electrons are fractal but the metric is not.

If the metric is nontrivial, Lorentz invariance breaks down independent of
how strong the fluctuations are.

*NO! You are wrong there. You violate the equivalence principle that GR is
locally flat (smooth, differentiable, etc.) when quantum metric
fluctuations are small.*

And if by "the worldlines of photons and electron" you mean "the paths that
contribute to the functional integral," then you're not quite right here --
- in quantum mechanics, nowhere-smooth paths dominate, but in quantum field
theory, the dominant configurations are not even continuous (nothing so
neat as a "fractal").As for quantum gravity, no one knows what the geometry
is like, or even whether geometry makes sense at the Planck scale.  Again,
if you have some real evidence for "fractal geometry," please publish!

*Lenny Susskind and others have published that the particle world lines
have a fractal dimension. A Frenchman has published similar stuff on
metric. I do not have references handy.*

>[much more deleted]

Steve Carlip
carlip@dirac.ucdavis.edu

Newsgroups: sci.physics