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cardboard adolescent · 04-20-2009, 12:42 AM

...
The MWI, due admittedly in part to its complexity, offers solutions to other problems as well. For instance, there is the issue of “anthropic bias,” which is the apparent “bias” required in our universe to support the presence of life. If, however, we take the MWI to suggest that all “possible” universes evolve in the multiverse, the very notion of “bias” becomes irrelevant. Instead, there are some universes which can support life and some which can't, and by definition we must necessarily find ourselves in one capable of sustaining life (Ratzsch, 2005). According to David Deutsch, the field of quantum computing also provides support for the MWI. Quantum computing takes advantage of particles' superpositions to do many different calculations simultaneously. An example of this is Shor's algorithm, which factors numbers with hundreds of digits in polynomial time. Factoring a number with 250 digits, for instance, could be done in a realistic amount of time even though it would take “10^500 or so times the computational resources that can be seen to be present.” Deutsch explains this by stating that there are 10^500 universes performing the calculation and they are sharing their results through interference, and challenges detractors to explain how else this is possible. The algorithm itself has been run by an IBM team and found to work, though it was only capable of factoring 15 into 5 and 3 (Deutsch, 1997). The MWI is also often favored by cosmologists, since it allows a complete description of the universe without specifying an external observer, though they are often agnostic regarding the ontological reality of the extra worlds. As shown, the MWI has implications that extend beyond philosophy into the practice of other areas of science.
But is it really as simple as it claims to be? Ockham's razor, as provided by the Stanford Encylopedia of Philosophy, holds “don't multiply entities beyond necessity” (Spade, 2006). It is easy to point out that the MWI does essentially the opposite by multiplying the one world we observe into an infinite of parallel worlds. However, this claim can be rejected on several grounds. The most popular is that the MWI reduces physics to just one entity, the wave function, and thus is the simplest interpretation of Quantum Mechanics. Whether or not the structure which arises from this foundation is simpler is not important to determining its congruence with Ockham's razor, in fact, a complex structure with simple rules seems to be the scientific ideal we are striding towards. Others, such as Deutsch, argue that the simplest realist explanation for interference effects is the existence of multiple universes. A competing construct such as Bohmian mechanics is considered inferior (i.e., more complex) because it requires additional structure to describe particle position and trajectories. Furthermore, Deutsch points out that Bohmian mechanics consists of large interacting sets, which he holds are equivalent to his “worlds,” interacting according to a global wave function, and that it is therefore simply the MWI with disguising excess baggage (Deutsch, 1997, Brown & Wallace, 2004). These claims only hold true, however, if we can show that the wave function does not require excess structure to make the MWI consistent with reality.
According to skeptics the formalism of the MWI fails to account for preferred basis or probability. When a “split” is said to occur, all of the universes formed correspond to elements of the wave function which previously described one universe. Preferred basis is the problem of identifying these elements and justifying how they are decomposed. Most contemporary supporters of the MWI attempt to solve this problem with the theory of decoherence (Bacciagaluppi, 2007). Wallace, for instance, claims that no inherent structure or preferred basis is necessary, and that the classical world emerges from the quantum world through the recurrence of patterns, which can in turn be explained by decoherence (Wallace, 2005). The issue of probability is similar. The argument against the MWI is that while it works perfectly in scenarios where the probability is 50/50, such as Schrödinger's cat, it doesn't account for situations where one outcome is more heighly weighted than another. Consider a Schrödinger's cat experiment, for instance, where the chance of survival is 1% and the chance of death is 99%. Since all the MWI states is that two universes are created it requires some additional formalism to account for the probability not being 50/50. This additional formalism does exist, and is known as the “probability postulate,” which states that the probability constants in the wave function correspond to a “measure of reality.” (Vaidman, 2002) Supporters of this postulate claim that it does not invalidate the MWI because all Quantum Mechanics interpretations require probability postulates, and as such the argument is a moot point. David Deutsch, however, takes a different approach. In his paper, “Quantum Theory of Probability and Decisions,” he combines the axioms of quantum mechanics with classical decision making to derive quantum probabilities. Because the MWI offers such an intuitive way to understand probability, this represents an incredible advancement.
To sum up, the Many Worlds Interpretation of quantum mechanics restores realism, determinism, locality by reducing Quantum Mechanics to just the wave function. Though this sounds ideal, it does so at the cost of a complex ontology. As I have shown, however, it is able to fit all these standards without postulating additional structure, and as such should be seen as the most viable alternative to the standard interpretation. Though there are other relative state formulations which accomplish similar goals, such as the Many Minds Interpretation, the Many Worlds Interpretation follows most clearly from Everett's original description. Also, I believe that the Many Minds Interpretation simply shifts the ontological “weirdness” of Everett's ideas from the physical to the psycho-physical realm, thus making it less accessible.
The implications of the MWI remain mysterious. In a universe of infinite Toms, which one am I? Am I the Tom defined by chance or is there a Tom ideal which all these Toms are simply permutations of? Some have even suggested that paranormal phenomena like poltergeists can be explained by interference effects from parallel universes. The common consensus among MWI proponents seems to be this: we live in a strange world, and a strange world requires a strange explanation.

Bibliography

Bacciagaluppi, G. (2007). The Role of Decoherence in Quantum Mechanics. Stanford Encyclopedia of Philosophy. The Role of Decoherence in Quantum Mechanics (Stanford Encyclopedia of Philosophy).
Berkovitz, J. (2007). Action at a Distance in Quantum Mechanics. Stanford Encyclopedia of Philosophy. Action at a Distance in Quantum Mechanics (Stanford Encyclopedia of Philosophy).
Brown, H. & Wallace, D. (2004). Solving the measurement problem: de Broglie-Bohm loses out to Everett. arXiv:quant-ph/0403094v1.
Deutsch, D. (1997). Fabric of Reality. New York: Penguin Books.
Deutsch, D. (1999). Quantum Theory of Probability and Decisions. arXiv:quant-ph/9906015v1.
Ratzsch, D. (2005). Teological Argument for God's Existence. Stanford Encyclopedia of Philsophy. Teleological Arguments for God's Existence (Stanford Encyclopedia of Philosophy).
Spade, P.V. (2006). William of Ockham. Stanford Encyclopedia of Philosophy. William of Ockham (Stanford Encyclopedia of Philosophy).
Tegmark, M. (1997). The Interpretation of Quantum Mechanics: Many Worlds or Many Words? arXiv:quant-ph/9709032v1.
Vaidman, L. (2002). Many-Worlds Interpretation of Quantum Mechanics. Stanford Encyclopedia of Philosophy. Many-Worlds Interpretation of Quantum Mechanics (Stanford Encyclopedia of Philosophy).
Wallace, D. (2005). Everett and Structure. Studies in the History and Philosophy of Modern Physics 34 (2003), pp. 87-105. arXiv:quant-ph/0107144v2.
Zeh, H. D. (2005). How decoherence can solve the measurement problem. SolveMeas.html.

04-20-2009, 12:42 AM	#28 (permalink)
cardboard adolescent ;) Join Date: Nov 2005 Location: CA Posts: 3,503	... The MWI, due admittedly in part to its complexity, offers solutions to other problems as well. For instance, there is the issue of “anthropic bias,” which is the apparent “bias” required in our universe to support the presence of life. If, however, we take the MWI to suggest that all “possible” universes evolve in the multiverse, the very notion of “bias” becomes irrelevant. Instead, there are some universes which can support life and some which can't, and by definition we must necessarily find ourselves in one capable of sustaining life (Ratzsch, 2005). According to David Deutsch, the field of quantum computing also provides support for the MWI. Quantum computing takes advantage of particles' superpositions to do many different calculations simultaneously. An example of this is Shor's algorithm, which factors numbers with hundreds of digits in polynomial time. Factoring a number with 250 digits, for instance, could be done in a realistic amount of time even though it would take “10^500 or so times the computational resources that can be seen to be present.” Deutsch explains this by stating that there are 10^500 universes performing the calculation and they are sharing their results through interference, and challenges detractors to explain how else this is possible. The algorithm itself has been run by an IBM team and found to work, though it was only capable of factoring 15 into 5 and 3 (Deutsch, 1997). The MWI is also often favored by cosmologists, since it allows a complete description of the universe without specifying an external observer, though they are often agnostic regarding the ontological reality of the extra worlds. As shown, the MWI has implications that extend beyond philosophy into the practice of other areas of science. But is it really as simple as it claims to be? Ockham's razor, as provided by the Stanford Encylopedia of Philosophy, holds “don't multiply entities beyond necessity” (Spade, 2006). It is easy to point out that the MWI does essentially the opposite by multiplying the one world we observe into an infinite of parallel worlds. However, this claim can be rejected on several grounds. The most popular is that the MWI reduces physics to just one entity, the wave function, and thus is the simplest interpretation of Quantum Mechanics. Whether or not the structure which arises from this foundation is simpler is not important to determining its congruence with Ockham's razor, in fact, a complex structure with simple rules seems to be the scientific ideal we are striding towards. Others, such as Deutsch, argue that the simplest realist explanation for interference effects is the existence of multiple universes. A competing construct such as Bohmian mechanics is considered inferior (i.e., more complex) because it requires additional structure to describe particle position and trajectories. Furthermore, Deutsch points out that Bohmian mechanics consists of large interacting sets, which he holds are equivalent to his “worlds,” interacting according to a global wave function, and that it is therefore simply the MWI with disguising excess baggage (Deutsch, 1997, Brown & Wallace, 2004). These claims only hold true, however, if we can show that the wave function does not require excess structure to make the MWI consistent with reality. According to skeptics the formalism of the MWI fails to account for preferred basis or probability. When a “split” is said to occur, all of the universes formed correspond to elements of the wave function which previously described one universe. Preferred basis is the problem of identifying these elements and justifying how they are decomposed. Most contemporary supporters of the MWI attempt to solve this problem with the theory of decoherence (Bacciagaluppi, 2007). Wallace, for instance, claims that no inherent structure or preferred basis is necessary, and that the classical world emerges from the quantum world through the recurrence of patterns, which can in turn be explained by decoherence (Wallace, 2005). The issue of probability is similar. The argument against the MWI is that while it works perfectly in scenarios where the probability is 50/50, such as Schrödinger's cat, it doesn't account for situations where one outcome is more heighly weighted than another. Consider a Schrödinger's cat experiment, for instance, where the chance of survival is 1% and the chance of death is 99%. Since all the MWI states is that two universes are created it requires some additional formalism to account for the probability not being 50/50. This additional formalism does exist, and is known as the “probability postulate,” which states that the probability constants in the wave function correspond to a “measure of reality.” (Vaidman, 2002) Supporters of this postulate claim that it does not invalidate the MWI because all Quantum Mechanics interpretations require probability postulates, and as such the argument is a moot point. David Deutsch, however, takes a different approach. In his paper, “Quantum Theory of Probability and Decisions,” he combines the axioms of quantum mechanics with classical decision making to derive quantum probabilities. Because the MWI offers such an intuitive way to understand probability, this represents an incredible advancement. To sum up, the Many Worlds Interpretation of quantum mechanics restores realism, determinism, locality by reducing Quantum Mechanics to just the wave function. Though this sounds ideal, it does so at the cost of a complex ontology. As I have shown, however, it is able to fit all these standards without postulating additional structure, and as such should be seen as the most viable alternative to the standard interpretation. Though there are other relative state formulations which accomplish similar goals, such as the Many Minds Interpretation, the Many Worlds Interpretation follows most clearly from Everett's original description. Also, I believe that the Many Minds Interpretation simply shifts the ontological “weirdness” of Everett's ideas from the physical to the psycho-physical realm, thus making it less accessible. The implications of the MWI remain mysterious. In a universe of infinite Toms, which one am I? Am I the Tom defined by chance or is there a Tom ideal which all these Toms are simply permutations of? Some have even suggested that paranormal phenomena like poltergeists can be explained by interference effects from parallel universes. The common consensus among MWI proponents seems to be this: we live in a strange world, and a strange world requires a strange explanation. Bibliography Bacciagaluppi, G. (2007). The Role of Decoherence in Quantum Mechanics. Stanford Encyclopedia of Philosophy. The Role of Decoherence in Quantum Mechanics (Stanford Encyclopedia of Philosophy). Berkovitz, J. (2007). Action at a Distance in Quantum Mechanics. Stanford Encyclopedia of Philosophy. Action at a Distance in Quantum Mechanics (Stanford Encyclopedia of Philosophy). Brown, H. & Wallace, D. (2004). Solving the measurement problem: de Broglie-Bohm loses out to Everett. arXiv:quant-ph/0403094v1. Deutsch, D. (1997). Fabric of Reality. New York: Penguin Books. Deutsch, D. (1999). Quantum Theory of Probability and Decisions. arXiv:quant-ph/9906015v1. Ratzsch, D. (2005). Teological Argument for God's Existence. Stanford Encyclopedia of Philsophy. Teleological Arguments for God's Existence (Stanford Encyclopedia of Philosophy). Spade, P.V. (2006). William of Ockham. Stanford Encyclopedia of Philosophy. William of Ockham (Stanford Encyclopedia of Philosophy). Tegmark, M. (1997). The Interpretation of Quantum Mechanics: Many Worlds or Many Words? arXiv:quant-ph/9709032v1. Vaidman, L. (2002). Many-Worlds Interpretation of Quantum Mechanics. Stanford Encyclopedia of Philosophy. Many-Worlds Interpretation of Quantum Mechanics (Stanford Encyclopedia of Philosophy). Wallace, D. (2005). Everett and Structure. Studies in the History and Philosophy of Modern Physics 34 (2003), pp. 87-105. arXiv:quant-ph/0107144v2. Zeh, H. D. (2005). How decoherence can solve the measurement problem. SolveMeas.html.