* Astronomy

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RE: Theory of Everything

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Electromagnetic Field

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RE: Theory of Everything

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Watch the 2011 Isaac Asimov Memorial Debate: The Theory of Everything

Can the entire universe be explained with a single, unifying theory? This is perhaps the most fundamental question in all of science, and it may also be the most controversial.
The 2011 Isaac Asimov Memorial debate, moderated by Hayden Planetarium Director Neil deGrasse Tyson, featured a compelling discussion with six of the worlds leading voices on the subject: Dr. Katherine Freese, professor of physics at the University of Michigan; Dr. Jim Gates, professor of physics at the University of Maryland-College Park; Dr. Janna Levin, professor of physics and astronomy at Barnard College; Dr. Marcello Gleiser, professor of physics and astronomy at Dartmouth College; Dr. Brian Greene, professor of physics and mathematics at Columbia University; and Dr. Lee Smolin, theoretical physicist at Perimeter Institute for Theoretical Physics.

Podcast: Download (1 hour, 45 mins, 127 MB)

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Physicists Prove to Be of Many Minds about a Unified Theory of the Universe

Brian Greene, a Columbia University physicist and author of the new book The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos (Knopf, 2011), explained that he only believes ideas that make testable predictions - an area where string theory has fallen short. But that does not mean string theory is without value, Greene was quick to point out.
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Title: Evidence Against Fine Tuning for Life
Authors: Don N. Page

The effective coupling `constants' of physics, especially the cosmological constant, are observed to have highly biophilic values. If this is not a hugely improbable accident, or a consequence of some mysterious logical necessity or of some simple principle of physics, it might be explained as a consequence either of an observership selection principle within a multiverse of many sets of effective coupling constants, or else of some biophilic principle that fine tunes the constants of physics to optimize life. Here evidence is presented against the hypothesis of fine tuning by a biophilic principle that maximises the fraction of baryons that form living beings.

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A Geometric Theory of Everything

Modern physics began with a sweeping unification: in 1687 Isaac Newton showed that the existing jumble of disparate theories describing everything from planetary motion to tides to pendulums were all aspects of a universal law of gravitation. Unification has played a central role in physics ever since. In the middle of the 19th century James Clerk Maxwell found that electricity and magnetism were two facets of electromagnetism. One hundred years later electromagnetism was unified with the weak nuclear force governing radioactivity, in what physicists call the electroweak theory.
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Title: An M Theory Solution to the Strong CP Problem and Constraints on the Axiverse
Authors: Bobby Samir Acharya, Konstantin Bobkov, Piyush Kumar
(Version v2)

We give an explicit realization of the "String Axiverse" discussed in Arvanitaki et. al {Arvanitaki:2009fg} by extending our previous results on moduli stabilization in M theory to include axions. We extend the analysis of {Arvanitaki:2009fg} to allow for high scale inflation that leads to a moduli dominated pre-BBN Universe. We demonstrate that an axion which solves the strong-CP problem naturally arises and that both the axion decay constants and GUT scale can consistently be around 2 x 10^{16} GeV with a much smaller fine tuning than is usually expected. Constraints on the Axiverse from cosmological observations, namely isocurvature perturbations and tensor modes are described. Extending work of Fox et. al {Fox:2004kb}, we note that {the observation of tensor modes at Planck will falsify the Axiverse completely.} Finally we note that Axiverse models whose lightest axion has mass of order 10^{-15} eV and with decay constants of order 5 x 10^{14} GeV require no (anthropic) fine-tuning, though standard unification at 10^{16} GeV is difficult to accommodate.

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The imperfect universe: Goodbye, theory of everything

Fifteen years ago, I was a physicist hard at work hunting for a theory of nature that would unify the very big and the very small. There was good reason to hope. The great and the good were committed. Even Einstein, who recognised that our understanding of reality is necessarily incomplete, had spent the last 20 years of his life searching for a unified field theory that would describe the two main forces we see acting around us - gravity and electromagnetism - as manifestations of a single force. For him, such a mathematical theory represented the purest and most elegant expression of nature and the highest achievement of the human intellect.
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There is no "Theory of Everything" inside E8
by Jacques Distler and Skip Garibaldi

The main content of this paper is a mathematical theorem (regarding copies of SL(2, C) in real or complex forms of E8) and its proof. From this mathematical statement, we deduce that one cannot obtain a Theory of Everything by embedding the gauge groups of gravity and the Standard Model into a real or complex form of E8. In particular, the sort of theory outlined in Garrett Lisi's preprint An exceptionally simple theory of everything (AESTOE) lacks certain representation-theoretic properties required by physical reality.

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