Weinstein's Universe
By Alok Jha
The Guardian, May 23, 2013
Edited by Andy Ross
Three big questions in modern
physics:
1 Dark matter and dark energy make up over 95% of the
universe, but no one knows what they are.
2 Elementary particles come
in three sets, the same except for the particle masses, but no one knows
why.
3 Quantum mechanics and the general theory of relativity are
pillars of physics, but no one can fit them together.
Eric Weinstein
has new theory. With a Harvard doctorate in mathematical physics, he
left academia more than two decades ago and is now a hedge fund
consultant in New York. At the invitation of Oxford mathematician Marcus
du Sautoy, Weinstein delivers a lecture today in Oxford.
Weinstein calls his theory
Geometric Unity. His 14D "observerse" has our 4D spacetime continuum
embedded in it. In 14D there is no missing dark matter, which he says comes
from the handedness of the Standard Model of particle physics. His theory is
even-handed, but we cannot easily detect the dark matter because when space
is relatively flat, the left-handed and right-handed spaces become
disconnected from each other. He proposes that dark energy is a fifth force
beside the familiar four. The force pushes space apart and its strength
varies. His theory also predicts more than 150 new elementary particles.
Weinstein has not shared his ideas widely yet. Scientists who have seen
some details agree on its elegant mathematics. But it takes more than math
to make good physics. Two reactions:
Johns Hopkins University
particle theorist David Kaplan: "What I would encourage him to do is modest
things and take steps and commit to a physical manifestation of his theory."
University of California at Berkeley mathematician Edward Frenkel: "I
think that both mathematicians and physicists should take Eric's ideas very
seriously. Even independently of their physical implications, I believe that
Eric's insights will be useful to mathematicians."
Weinstein plans to
post an ArXiv paper on all this.
Weinstein's Answer
By Marcus du Sautoy
The Guardian, May 23, 2013
Edited by Andy Ross
Two years ago in New York,
Eric Weinstein, whom I've known for more than 20 years, explained his theory
to me, and I began to see potential answers for many of the major problems
in physics. He has spent the past two years taking me through the ins and
outs of the theory.
Symmetry is a key ingredient of his theory. The
idea is not new, but despite the great success of the Standard Model there
remain questions that have intrigued physicists for years.
The SM
particles fall into three generations. In generation 1 we see the electron,
the electron neutrino, two quarks, and their anti-particles. But then in G2
and G3 we have two more versions of these particles that are just the same
except that they are more massive. The G2 version of the electron is the
muon and the G3 version is the tau particle.
Physicists are
challenged to provide a natural explanation for these three generations.
Weinstein does so in a new geometric structure involving a much larger
symmetry including the symmetry of the Standard Model. The geometry not only
explains G1 and G2 but also predicts that G3 will behave differently at high
energies.
The SM particles have spin. The 3G fermions all have spin
1/2. But Weinstein predicts new particles with spin 3/2 showing familiar
responses to forces other than gravity, plus a slew of new particles with
familiar spin but unfamiliar responses to the SM forces.
Weinstein's
geometry also explains dark matter and why we can't see it. When the
symmetry in Weinstein's model breaks, a part gets separated from the half we
interact with. The particles in this part of the broken symmetry might
gravitate but otherwise be dark.
Weinstein's symmetry group emerges
from his reconciliation of Einstein's field equations with the Yang-Mills
equations and the Dirac equation. The field equations describe the curvature
of spacetime and embody a theory of gravity, whereas the Yang-Mills and
Dirac equations are a theory of particle interactions in quantum theory.
Both theories are successful, but they are not compatible with each
other. Most attempts to unify them move the geometry of Einstein into the
quantum world. Weinstein's ideas are more in line with Einstein's belief in
the power of geometry. Weinstein calls his proposal Geometric Unity.
His theory is the first major challenge to the validity of Einstein's
field equations. It reveals that just as Newton's equations were an
approximation to nature so too are Einstein's. On the way, Weinstein weaves
in a solution to the mystery of dark energy.
Recently we have
discovered that the universe is not only expanding but also accelerating,
pushed by dark energy. Weinstein provides a coherent mathematical
justification for dark energy. In his account, it varies with the curvature
of the universe. We are in a relatively flat piece of the universe, which
explains why we don't feel it.
Weinstein's theory also improves on
the Higgs mechanism. The Higgs field was added retrospectively to the
Standard Model to account for the fact that most SM particles have mass.
Geometric Unity has a mass term that emerges naturally from the theory.
It has been a privilege to be one of the first to see the ideas that
Weinstein is proposing. This is such a major project that it will take some
time to work it all out. For me, what is so appealing about Weinstein's
ideas is that things aren't inserted arbitrarily to make the theory fit the
data but instead emerge naturally from the mathematics.
By Andrew Pontzen
New Scientist, May 24, 2013
Edited by Andy Ross
Yesterday, Eric Weinstein, encouraged by Marcus du Sautoy, went public with
a loud splash at the University of Oxford. While Weinstein was delivering
his lecture, the theoretical physicists were in a different room listening
to a different speaker discuss a different topic. Only afterwards did anyone
spot news of the event next door. Hosting a lecture in a university physics
department without inviting any physicists is, at best, an unforgivable
oversight. Yesterday's shenanigans were anything but scientific.
AR This is wildly exciting — but I fear I may
never get to understand the theory properly.
And now for something completely different ...
Maybe No Space Brain Threat
By Adam Becker
New Scientist, May 2013
Edited by Andy Ross
Large numbers of disembodied brains floating in deep space threaten to
undermine our understanding of the universe. New work suggests string theory
and the multiverse may banish them.
Boltzmann brains are
free-floating conscious entities that form spontaneously in outer space. The
laws of physics don't rule them out, so long as time goes on long enough for
them to form. If the universe expands exponentially forever, it will
eventually spawn inconceivable numbers of Boltzmann brains, far outnumbering
every human who has ever, or will ever, live. In that case, summed over all
time, their experience of the universe will overwhelm our own.
Our
understanding of the universe presumes that humans are typical observers. If
we're not, our basic experience of time looks iffy, because Boltzmann brains
would exist in the far future when the universe is an inky void, with a past
indistinguishable from the future. In a long-lived universe, time loses its
arrow. So to prevent a plague of Boltzmann brains, we need to show that the
universe has a finite lifespan.
According to string theory, there
may be a vast number of big-bang universes. All of them come from eternal
inflation in a boiling ocean that endlessly spawns them like bubbles. This
is the multiverse. Many of these other universes could host lots of
conscious creatures early in their histories when the past is distinct from
the future. That could help make our point of view the standard one. But if
these universes live on too long, they will grow Boltzmann brains, tipping
the balance away from us again.
Claire Zukowski and Raphael Bousso
suggest this won't happen. Universes are constantly budding off a parent
universe in the multiverse, and the parent limits what kinds of baby
universes gestate in it, and whether those universes will live long enough
to fill up with Boltzmann brains or die first.
Bousso and Zukowski
performed a mathematical analysis of multiverses that start out in one of
two different initial states: an older model first suggested by Stephen
Hawking and James Hartle and a newer model based on string theory and the
multiverse. While the Ha-Ha model ended up overrun with Boltzmann brains,
our kind of minds prevail in the new model and time is saved.
AR Whew, that was close!
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