Re: The chance for a vet to stand tall.

On Sun, 30 Aug 2009 17:02:19 +0100, Oz wrote:

Steve B <steve@xxxxxxxxxxxxxx> writes

I've just found a copy of 'the road to reality' by Roger Penrose in the
local library. I find it is not amenable to speed reading,

His stuff usually is like that. I thought I had a copy but I don't seem
to, at least any more. Can't remember what it was about...

however it does seem to be
very comprehensive. In fact, it might take me quite a (long) while to
absorb all the detail. I think I shall have to buy a copy.

<shudder>

Hmmm...

I don't know that I have read it ...

I'm not sure that many people have, tho' I suspect that many are in the
process of reading it.
It seems, in part, to be intended as an accompaniment to a series of
lectures. Certainly, a lot of lecturers are more understandable at the
chalk face, as it were, than in print. It would be useful if it were
possible to buy video recordings of these things, however I expect that
would be in contravention of academic principles (and principals).


thanks for the write up below, it carries more insight than the amazon
reviews that I looked at.

==============================

Not Even Wrong
‹ Weil’s Letter From Prison
The Next Few Years in Particle Physics › The Road to Reality

Roger Penrose’s new book The Road to Reality is being released in the
U.S. in a week or so. I’d been intending to write something about the
book ever since I got a copy of the British edition a couple months ago,
but this is quite a daunting task. The book is nearly 1100 pages long
and actually comes close to living up to its subtitle: “A Complete Guide
to the Laws of the Universe”. It certainly is the most wide-ranging book
on theoretical physics that I can think of, offering not just a summary
of a lot of material, but an in-depth treatment of many of the more
sophisticated ideas of the subject.

Penrose’s point of view is that of a relativist, so his treatment of
geometry, general relativity and classical field equations is the
deepest and most detailed part of the book. But he also discusses
quantum theory extensively as well as the various attempts to quantize
gravity. Compared to the general relativity parts, his treatment of
particle physics and quantum field theory is rather sketchy, but quite
original.

One of the unique aspects of the book is its extensive use of drawings
to illustrate mathematical, geometrical and physical concepts. In this
respect it is unparalleled by any other mathematically sophisticated
text I’ve ever seen. One of Penrose’s main fascinations is the crucial
role that complex numbers play, both in quantization and in the geometry
of spinors. He has always been motivated by the idea that complex
structures provide an important link between these two subjects, one
that is still poorly understood. I very much agree with him about this.
Related to this issue, some of the topics covered in the book that
aren’t in any non-technical reference that I know of are his discussions
of hyperfunctions and the Fourier transform, the geometry of spinors and
twistors, and the use of complex structures in quantization and quantum
field theory.

Penrose also carefully lays out areas in which his point of view differs
from the general consensus of most theoretical physicists. An example is
his emphasis on the importance for cosmology of understanding why the
universe had such low entropy at the Big Bang. For more about this, see
a posting by Sean Carroll.

A second area where Penrose is less than orthodox is his belief that
quantum gravity somehow modifies quantum theory and resolves its
measurement paradoxes. He explains an experimental set-up that could in
principle test whether gravity plays a role in quantum state reduction,
but he doesn’t have a concrete proposal for how standard quantum
mechanics is to be modified.

Finally, there’s a remarkable chapter on supersymmetry, extra
dimensions, and string theory. Penrose is very skeptical of the whole
idea of introducing more that 4 space-time dimensions. One reason is
that the beautiful spinor and twistor geometry that fascinates him is
special to 4 dimensions. Another reason he gives is the classical
instability of higher-dimensional space-times. Under a small
perturbation, such space-times should collapse and form singularities.
The difficulties in stabilizing extra dimensions are at the heart of the
problems of string theory, with the only known way of doing it leading
to the “Landscape” picture and ruining any ability to get predictions
out of the theory.

Penrose is critical of the supposed calculation of black hole entropy
from string theory, noting: ” As appears to be usual with such string-
theoretic proclamations, this conclusion is very considerably
overblown.” He has quite a few other very critical comments about string
theory and the way in which research in the field has been pursued. As
you might guess, I’m very much in agreement with his point of view and
glad to see it in print. I’d be very curious to know whether recent
ideas about strings in twistor space and Yang-Mills theory have changed
his views much on the whole topic of string theory.

Update: A commenter pointed out that Science magazine has a review of
Penrose’s book by Frank Wilczek (subscription required). Wilczek is
right that there isn’t very much about particle physics in the book and
Penrose gets something wrong about neutral K-meson mixing. Wilczek also
says Penrose makes incorrect statements about electroweak symmetry
breaking, but in a quick look at the book I couldn’t find what he was
objecting to. He seems to object strongly to the speculative later parts
of the book, but I don’t quite understand why. Penrose is up-front about
what is speculation (e.g. relations between twistor theory and QM) and
what is solid science, and Wilczek’s comment that “at present twistor
ideas appear more as the desire for a physical theory than the
embodiment of one”, could equally be applied to string theory, leaving
one wondering why he doesn’t write strongly critical reviews of books on
that subject.

If you want to read Lubos Motl’s comments on a book he hasn’t read,
they’re here.

.

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