STARpod.org Required Reading

Many lives in many worlds

Abstract: I argue that accepting quantum mechanics to be universally true means that you should also believe in parallel universes. I give my assessment of Everett's theory as it celebrates its 50th anniversary.

http://arxiv.org/pdf/0707.2593

Parallel Universes

Abstract: I survey physics theories involving parallel universes, which form a natural four-level hierarchy of multiverses allowing progressively greater diversity.
Level I: A generic prediction of inflation is an infinite ergodic universe, which contains Hubble volumes realizing all initial conditions - including an identical copy of you about 10^{10^29} meters away.
Level II: In chaotic inflation, other thermalized regions may have different effective physical constants, dimensionality and particle content.
Level III: In unitary quantum mechanics, other branches of the wavefunction add nothing qualitatively new, which is ironic given that this level has historically been the most controversial.
Level IV: Other mathematical structures give different fundamental equations of physics. The key question is not whether parallel universes exist (Level I is the uncontroversial cosmological concordance model), but how many levels there are. I discuss how multiverse models can be falsified and argue that there is a severe "measure problem" that must be solved to make testable predictions at levels II-IV.

http://arxiv.org/pdf/astro-ph/0302131

A new empirical approach in the Search for Extraterrestrial Intelligence: Astrobiological nonlocality at the cosmological level

Over a period of several decades a concerted effort has been made to determine whether intelligent life exists outside of our solar system, known as the Search for Extraterrestrial Intelligence or SETI. This has been based primarily upon attempting to intercept possible radio transmissions at different frequencies with arrays of radio telescopes. In addition, astrophysical observations have also been undertaken to see if other worlds or solar systems exist with similar conditions such as ours, which might be conducive to life. And, numerous papers have been written exploring different possibilities for the existence of life or why we have not observed it as of yet, since none of these approaches have been successful. It may now be possible to explore this issue from another standpoint. Recent theoretical and experimental results in the field of biophysics appear to indicate the possibility of quantum entanglement and nonlocality at the biological level, between spatially separated pairs of human subjects and also between basins containing neurons derived from human neural stem cells. If this research continues to be upheld in a more replicable fashion, this could have very important implications in the area of controllable superluminal communication. Experiments are proposed in an attempt to address the issue of whether controllable superluminal communication is possible and, if it is, to utilize it in an attempt to determine if extraterrestrial intelligence really exists, within the framework of astrobiological nonlocality.

http://xxx.lanl.gov/pdf/physics/0608285

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The importance of quantum decoherence in brain processes

Authors: Max Tegmark

(Submitted on 5 Jul 1999 (v1), last revised 10 Nov 1999 (this version, v2))

Abstract: Based on a calculation of neural decoherence rates, we argue that that the degrees of freedom of the human brain that relate to cognitive processes should be thought of as a classical rather than quantum system, i.e., that there is nothing fundamentally wrong with the current classical approach to neural network simulations. We find that the decoherence timescales ~10^{-13}-10^{-20} seconds are typically much shorter than the relevant dynamical timescales (~0.001-0.1 seconds), both for regular neuron firing and for kink-like polarization excitations in microtubules. This conclusion disagrees with suggestions by Penrose and others that the brain acts as a quantum computer, and that quantum coherence is related to consciousness in a fundamental way.

http://arxiv.org/abs/quant-ph/9907009

Quantum Computation in Brain Microtubules? Decoherence and Biological Feasibility

Authors: S. Hagan, S. R. Hameroff, J. A. Tuszyński

(Submitted on 4 May 2000)

Abstract: The Penrose-Hameroff (`Orch OR') model of quantum computation in brain microtubules has been criticized as regards the issue of environmental decoherence. A recent report by Tegmark finds that microtubules can maintain quantum coherence for only $10^{-13}$ s, far too short to be neurophysiologically relevant. Here, we critically examine the assumptions behind Tegmark's calculation and find that: 1) Tegmark's commentary is not aimed at an existing model in the literature but rather at a hybrid that replaces the superposed protein conformations of the `Orch OR' theory with a soliton in superposition along the microtubule, 2) Tegmark predicts decreasing decoherence times at lower temperature, in direct contradiction of the observed behavior of quantum states, 3) recalculation after correcting Tegmark's equation for differences between his model and the `Orch OR' model (superposition separation, charge vs. dipole, dielectric constant) lengthens the decoherence time to $10^{-5} - 10^{-4}$ s and invalidates a critical assumption of Tegmark's derivation, 4) incoherent metabolic energy supplied to the collective dynamics ordering water in the vicinity of microtubules at a rate exceeding that of decoherence can counter decoherence effects (in the same way that lasers avoid decoherence at room temperature), and 5) phases of actin gelation may enhance the ordering of water around microtubule bundles, further increasing the decoherence-free zone by an order of magnitude and the decoherence time to $10^{-2} - 10^{-1}$ s. These revisions bring microtubule decoherence into a regime in which quantum gravity can interact with neurophysiology.

http://arxiv.org/abs/quant-ph/0005025

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EDGE.org IT'S A MUCH BIGGER THING THAN IT LOOKS

A Talk with David Deutsch

However useful the theory [of quantum computation] as such is today and however spectacular the practical applications may be in the distant future, the really important thing is the philosophical implications — epistemological and metaphysical — and the implications for theoretical physics itself. One of the most important implications from my point of view is one that we get before we even build the first qubit [quantum bit]. The very structure of the theory already forces upon us a view of physical reality as a multiverse. Whether you call this the multiverse or 'parallel universes' or 'parallel histories', or 'many histories', or 'many minds' — there are now half a dozen or more variants of this idea — what the theory of quantum computation does is force us to revise our explanatory theories of the world, to recognize that it is a much bigger thing than it looks. I'm trying to say this in a way that is independent of 'interpretation': it's a much bigger thing than it looks.

 

On Math, Matter and Mind

Authors: Piet Hut (IAS), Mark Alford (WashU), Max Tegmark (MIT)

(Submitted on 21 Oct 2005 (v1), last revised 15 Jan 2006 (this version, v2))

Abstract: We discuss the nature of reality in the ontological context of Penrose's math-matter-mind triangle. The triangle suggests the circularity of the widespread view that math arises from the mind, the mind arises out of matter, and that matter can be explained in terms of math. Non-physicists should be wary of any claim that modern physics leads us to any particular resolution of this circularity, since even the sample of three theoretical physicists writing this paper hold three divergent views. Some physicists believe that current physics has already found the basic framework for a complete description of reality, and only has to fill in the details. Others suspect that no single framework, from physics or other sources, will ever capture reality. Yet others guess that reality might be approached arbitrarily closely by some form of future physics, but probably based on completely different frameworks. We will designate these three approaches as the fundamentalist, secular and mystic views of the world, as seen by practicing physicists. We present and contrast each of these views, which arguably form broad categories capturing most if not all interpretations of physics. We argue that this diversity in the physics community is more useful than an ontological monoculture, since it motivates physicists to tackle unsolved problems with a wide variety of approaches.

http://arxiv.org/abs/physics/0510188

100 Years of the Quantum

Authors: Max Tegmark, John Archibald Wheeler

(Submitted on 17 Jan 2001)

Abstract: As quantum theory celebrates its 100th birthday, spectacular successes are mixed with outstanding puzzles and promises of new technologies. This article reviews both the successes of quantum theory and the ongoing debate about its consequences for issues ranging from quantum computation to consciousness, parallel universes and the nature of physical reality. We argue that modern experiments and the discovery of decoherence have have shifted prevailing quantum interpretations away from wave function collapse towards unitary physics, and discuss quantum processes in the framework of a tripartite subject-object-environment decomposition. We conclude with some speculations on the bigger picture and the search for a unified theory of quantum gravity.

http://arxiv.org/abs/quant-ph/0101077