[Phys-l] Smolin's preons = geons?

[Spinoza321@aol.com]

This is a basic explanation of what I am talking about in the earlier  posts. 
Unfortunately I cannot send the pictures. This article is available in  the 
New Scientist publication. Basically fundamental particles are modeled as  
triplets of string like objects which can twist and cross each other creating  
topological charges which are postulated as the source of electroweak,  strong 
and helicity of the fundamental particles of the SM. For Fermions you end  with 
two three dimensional flavor spaces and two four dimensional flavor spaces  
based on electric charge and helicity.
 
 
 ( + L) = { e(+) U d(+)   }_L                     ( - R) = {e(-) U(-) d }_R 
 
 
  (+R)= { e(+) U d(+) v}  _R                     ( - L) = { e(-) U(-) d v}_L 
 
 
Note here the neutrino is it's own antiparticle. 
 
 
 
Bob Zannelli 
 
 
 
 ==================  
Lee Smolin and colleagues have come up with an interesting particle model  
that looks to 
me to be quite compatible with 4-geons. The relevant papers  [1] are 
discussed in this 
Physics Forums thread:
 

http://www.physicsfhttp://wwwhttp://www.http://www.p
 

(I see Carl is active in that thread!)
and are also discussed in a  New Scientist article [2]
Some of the figures in the papers [1] conjure up  images that are more or 
less what I have 
always had in my mind when I  imagined what 4-geons might "look" like.

Mark, I wonder whether you have  any comments on this? Is this what you have 
in mind for 
what a 4-geon might  "look" like? (Hmm ... I wonder whether the "4-" in 
4-geon applies to 
their  stuff ..)

David

PS: Sorry I've been neglecting this group for the  past 6 months. I've 
started a rewrite of my 
MMWI paper from scratch, mainly  so that I can get it under 6000 words 
(required for 
submission to  international foundation of louis de Broglie). I should say 
that the second  
paper in [1] (0603022) uses the idea of a superposition of spacetimes in,  
afaict, exactly 
the same way that I use it. And their basic idea of a preon  is also, afaict, 
exactly what I 
have in mind when I think of geons. Hmmm ...  what they HAVEN'T done is show 
how the 
Born rule emerges -- which I know how  to do!!

[1]
http://arxiv.http://arxivhttp://arx
 

http://arxiv.http://arxivhttp://arx

[2]
http://www.newscienhttp://wwhttp://www.newschttp://www.newschtt
 
 

You are made of space-time
12 August 2006
> From New Scientist  Print Edition. Subscribe and get 4 free issues.
Davide  Castelvecchi
Valerie Jamieson

LEE SMOLIN is no magician. Yet he and  his colleagues have pulled off one of 
the greatest 
tricks imaginable.  Starting from nothing more than Einstein's general theory 
of relativity,  
they have conjured up the universe. Everything from the fabric of space to  
the matter that 
makes up wands and rabbits emerges as if out of an empty  hat.

It is an impressive feat. Not only does it tell us about the origins  of 
space and matter, it 
might help us understand where the laws of the  universe come from. Not 
surprisingly, 
Smolin, who is a theoretical physicist  at the Perimeter Institute in 
Waterloo, Ontario, is very 
excited. "I've been  jumping up and down about these ideas," he says.

This promising approach  to understanding the cosmos is based on a collection 
of theories 
called loop  quantum gravity, an attempt to merge general relativity and 
quantum  
mechanics into a single consistent theory.

The origins of loop  quantum gravity can be traced back to the 1980s, when 
Abhay 
Ashtekar, now at  Pennsylvania State University in University Park, rewrote 
Einstein's  
equations of general relativity in a quantum framework. Smolin and Carlo  
Rovelli of the 
University of the Mediterranean in Marseille, France, later  developed 
Ashtekar's ideas and 
discovered that in the new framework, space  is not smooth and continuous but 
instead 
comprises indivisible chunks just  10-35 metres in diameter. Loop quantum 
gravity then 
defines space-time as a  network of abstract links that connect these volumes 
of space, 
rather like  nodes linked on an airline route map.

> From the start, physicists noticed  that these links could wrap around one 
another to form 
braid-like  structures. Curious as these braids were, however, no one 
understood their  
meaning. "We knew about braiding in 1987," says Smolin, "but we didn't know  
if it 
corresponded to anything physical."

Enter Sundance  Bilson-Thompson, a theoretical particle physicist at the 
University of  
Adelaide in South Australia. He knew little about quantum gravity when, in  
2004, he began 
studying an old problem from particle physics.  Bilson-Thompson was trying to 
understand 
the true nature of what physicists  think of as the elementary particles - 
those with no 
known sub-components.  He was perplexed by the plethora of these particles in 
the 
standard model,  and began wondering just how elementary they really were. As 
a first step  
towards answering this question, he dusted off some models developed in the  
1970s that 
postulated the existence of more fundamental entities called  preons.

Just as the nuclei of different elements are built from protons  and 
neutrons, these preon 
models suggest that electrons, quarks, neutrinos  and the like are built from 
smaller, 
hypothetical particles that carry  electric charge and interact with each 
other. The models 
eventually ran into  trouble, however, because they predicted that preons 
would have vastly 
more  energy than the particles they were supposed to be part of. This fatal 
flaw saw  the 
models abandoned, although not entirely  forgotten.

Bilson-Thompson took a different tack. Instead of thinking of  preons as 
particles that join 
together like Lego bricks, he concentrated on  how they interact. After all, 
what we call a 
particle's properties are  really nothing more than shorthand for the way it 
interacts with 
everything  around it. Perhaps, he thought, he could work out how preons 
interact, and  
from that work out what they are.

To do this, Bilson-Thompson  abandoned the idea that preons are point-like 
particles and 
theorised that  they in fact possess length and width, like ribbons that 
could somehow  
interact by wrapping around each other. He supposed that these ribbons could  
cross over 
and under each other to form a braid when three preons come  together to make 
a particle. 
Individual ribbons can also twist clockwise or  anticlockwise along their 
length. Each twist, 
he imagined, would endow the  preon with a charge equivalent to one-third of 
the charge 
on an electron,  and the sign of the charge depends on the direction of the 
twist.

The  simplest braid possible in Bilson-Thompson'The  simplest braid possible 
in Bilson-
and corresponds to an electron neutrino (see Graphic). Flip it over  in a 
mirror and you have 
its antimatter counterpart, the electron  anti-neutrino. Add three clockwise 
twists and you 
have something that  behaves just like an electron; three anticlockwise 
twists and you have 
a  positron. Bilson-Thompson'a  positron. Bilson-Thompson'<WBR>s model also 
produces pho
particles that carry the electromagnetic and weak forces. In  fact, these 
braided ribbons 
seem to map out the entire zoo of particles in  the standard model.

Bilson-Thompson published his work online last year  
(www.arxiv.org/Bilson-Thom
0503213). Despite its achievements, however,  he still didn't know what the 
preons were. 
Or what his braids were really  made from. "I toyed with the idea of them 
being micro-
wormholes, which  wrapped round each other. Or some other extreme distortions 
in the 
structure  of space-time," he recalls.

It was at this point that Smolin stumbled  across Bilson-Thompson'It was at 
this point t
this, we got very excited  because we had been looking for anything that 
might explain 
braiding," says  Smolin. Were the two types of braids one and the same? Are 
particles 
nothing  more than tangled plaits in space-time?

Smolin invited Bilson-Thompson to  Waterloo to help him find out. He also 
enlisted the 
help of Fotini  Markopoulou at the institute, who had long suspected that the 
braids in  
space might be the source of matter and energy. Yet she was also aware that  
this idea sits 
uneasily with loop quantum gravity. At every instant, quantum  fluctuations 
rumple the 
network of space-time links, crinkling it into a  jumble of humps and bumps. 
These 
structures are so ephemeral that they last  for around 10-44 seconds before 
morphing into 
a new configuration. "If the  network changes everywhere all the time, how 
come anything 
survives?" asks  Markopoulou. "Even at the quantum level, I know that a 
photon or an 
electron  lives for much longer that 10-44 seconds."

Markopoulou had already found  an answer in a radical variant of loop quantum 
gravity she 
had been  developing together with David Kribs, an expert in quantum 
computing at the  
University of Guelph in Ontario. While traditional computers store  
information in bits that 
can take the values 0 or 1, quantum computers use  "qubits" that, in 
principle at least, can 
be 0 and 1 at the same time, which  is what makes quantum computing such a 
powerful 
idea. Individual qubits'  delicate duality is always at risk of being lost as 
a result of 
interactions  with the outside world, but calculations have shown that 
collections of qubits  
are far more robust than one might expect, and that the data stored on them  
can survive 
all kinds of disturbance.

In Markopoulou and Kribs's  version of loop quantum gravity, they considered 
the universe 
as a giant  quantum computer, where each quantum of space is replaced by a 
bit of  
quantum information. Their calculations showed that the qubits' resilience  
would preserve 
the quantum braids in space-time, explaining how particles  could be so 
long-lived amid 
the quantum turbulence.

Smolin,  Markopoulou and Bilson-Thompson have now confirmed that the braiding 
of this  
quantum space-time can produce the lightest particles in the standard model  
- the 
electron, the "up" and "down" quarks, the electron neutrino and their  
antimatter partners 
(www.arxiv.org/(www.arxiv.(www.arxi

All  from nothing at all

So far the new theory reproduces only a few of the  features of the standard 
model, such as 
the charge of the particles and  their "handedness"the charge of the 
particles and  
particle's  quantum-mechanical spin relates to its direction of travel in 
space. Even so,  
Smolin is thrilled with the progress. "After 20 years, it is wonderful to  
finally make some 
connection to particle physics that isn't put in by hand,"  he says.

The correspondence between braids and particles suggests that  more 
properties may be 
waiting to be derived from the theory. The most  substantial achievement, 
Smolin says, 
would be to calculate the masses of  the elementary particles from first 
principles. It is a 
hugely ambitious  goal: predicting the masses and other fundamental constants 
of nature 
was  something string theorists set out to do more than 20 years ago - and 
have now  all 
but given up on.

As with string theory, devising experiments to  test for the new theory will 
also be difficult. 
This is a problem that  plagues loop quantum gravity in all its guises, 
because no 
conceivable  experiment can probe space down to 10-35 metres.

Ironically, the best  arena in which to look for experimental proof might be 
the largest 
scales in  the universe, not the smallest. "The closest anyone is getting to 
making  
predictions is in the area of cosmology," says John Baez, a mathematician  
and expert on 
quantum gravity at the University of California, Irvine.  Markopoulou is now 
trying to think 
of ways of testing the braid model using  the fossil radiation left over from 
the big bang, 
the so-called cosmic  microwave background that permeates the universe. 
Physicists 
believe that  the patterns we see today in that radiation may have originated 
from quantum  
fluctuations during the earliest moments of the big bang, when all of the  
matter in the 
universe was crammed into a space small enough for quantum  effects to be 
significant.

Meanwhile, Markopoulou'Meanwhile, Markopoulou'<WBR>s vision of the  universe 
as a gian
more than a useful analogy: it  might be true, according to some theorists. 
If so, there is 
one startling  consequence: space itself might not exist. By replacing loop 
quantum  
gravity's chunks of space with qubits, what used to be a frame of reference  
- space itself - 
becomes just a web of information. If the notion of space  ceases to have 
meaning at the 
smallest scale, Markopoulou says, some of the  consequences of that could 
have been 
magnified by the expansion that  followed the big bang. "My guess is that the 
non-
existence of space has  effects that are measurable, if you can only see it 
right." Because 
it's  pretty hard to wrap your mind around what it means for there to be no 
space, she  
adds.

Hard indeed, but worth the effort. If this version of loop  quantum gravity 
can reproduce all 
of the features of the standard model of  particle physics and be borne out 
in experimental 
tests, we could be onto  the best idea since Einstein. "It's a beautiful 
idea. It's a brave, 
strange  idea," says Rovelli. "And it might just work."

Of course, most physicists  are reserving judgement. Joe Polchinski, a string 
theorist at 
Stanford  University in California, believes that Smolin and his colleagues 
still have a  lot of 
work to do to show that their braids capture all of the details of  the full 
standard model. 
"This is in a very preliminary stage. One has to  play with it and see where 
it goes," 
Polchinski says.

If the new loop  quantum gravity does go the distance, though, it could give 
us a new 
sense  of our place in the universe. If electrons and quarks - and thus atoms 
and  people - 
are a consequence of the way space-time tangles up on itself, we  could be 
nothing more 
than a bundle of stubborn dreadlocks in space. Tangled  up as we are, we 
could at least 
take comfort in knowing at last that we  truly are at one with the universe.

Supersizing quantum  gravity

For loop quantum gravity to succeed as a fundamental theory of  gravity, it 
should at the 
very least predict that apples fall to Earth. In  other words, Newton's law 
of gravity should 
naturally arise from it. It is a  tall order for a theory that generates 
space and time from 
scratch to  describe what happens in the everyday world, but Carlo Rovelli at 
the University  
of the Mediterranean in Marseille, France, and his team have succeeded in  
doing just that. 
"Essentially we have calculated Newton's law starting from  a world with no 
space and no 
time," he says  (www.arxiv.org/time," he time," he

Newton's law of gravity  describes the attractive force between two masses 
separated by a 
given  distance. However, it is not so simple to measure this separation when 
space has  a 
complex quantum architecture of the sort in loop quantum gravity, where it  
is not even 
clear what is meant by distance. This has been the biggest  obstacle to 
showing how 
Newton's law can emerge from quantised  space.

The naive way to measure length in quantised space is to hop from  one 
quantum to 
another, counting how many steps it takes to reach the final  destination. 
According to 
loop quantum gravity, however, the fabric of space  seethes with quantum 
fluctuations, so 
the distance between two points is  forever changing, and can even take 
several values at 
the same  time.

Working with Eugenio Bianchi of the University of Pisa, Leonardo  Modesto of 
the University 
of Bologna and Simone Speziale of the Perimeter  Institute in Waterloo, 
Ontario, Rovelli 
circumvented the problem. The team  found a mathematical way of isolating 
regions of 
space for long enough to  measure the separation between two points. When 
they zoomed 
out and used  this mathematics to look at space-time on much larger scales, 
they found  
that Newton's law popped out of their theory.

The calculation by  Rovelli's team does not yet reproduce the full complexity 
of Einstein's  
general relativity, which also describes masses large enough to curve space  
appreciably. 
Their result does point in the right direction, however. Lee  Smolin of the 
Perimeter 
Institute calls it a major step forward. "Their work  shows that loop quantum 
gravity 
definitely has gravity in it," he says.  "It's no longer just pie in the sky."