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.

Weinstein's Shenanigans

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!