October 24th, 2012
In 1956 Hugh Everett III published his Ph.D. dissertation titled “The Theory of the Universal Wave Function.” In this paper Everett argued for the relative state formulation of quantum theory and a quantum philosophy, which denied wave collapse. Initially, this interpretation was highly criticized by the physics community, and when Everett visited Niels Bohr in Copenhagen in 1959 Bohr was unimpressed with Everett’s most recent development . In 1957 Everett coined his theory as the Many Worlds Interpretation (MWI) of quantum mechanics. In an attempt to circumvent the problem of defining the mechanism for the state of collapse Everett suggested that all orthogonal relative states are equally valid ontologically. An orthogonal state is one that is mutually exclusive. A system cannot be in two orthogonal states at the same time. As a result of the measurement interaction, the states of the observer have evolved into exclusive states precisely linked to the results of the measurement. At the end of the measurement process the state of the observer is the sum of eigenstate—or a combination of the sums of eigenstates, one sum for each possible value of the eigenvalue. Each sum is the relative state of the observer given the value of the eigenvalue . What this means is that all-possible states are true and exist simultaneously.
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October 23rd, 2012
In a brief section of Karl Popper’s Quantum Theory and the Schism in Physics he discusses his attraction to the Many Worlds Interpretation of quantum physics as well as the reason for his rejection of it. Popper is actually quite pleased with Everett’s three-fold contribution to the field of quantum physics. Despite his attraction to the interpretation he rejects it based on the falsifiability of the symmetry behind the Schrödinger equation.
Popper’s model allows for a theory to be scientific prior to supported evidence. There is no positive case for purporting a theory under his model. There can only be a negative case to falsify it and as long as it may be potentially falsified it is scientific. Thus, a scientific theory could have no evidence or substantiated facts to provide good reasons for why it may be true. What makes this discussion of MWI interesting is that despite Popper’s attraction to MWI it’s not the attraction that makes it scientific, it’s his criterion of falsification.
In favor of MWI:
- The MWI is completely objective in its discussion of quantum mechanics.
- Everett removes the need and occasion to distinguish between ‘classical’ physical systems, like the measurement apparatus, and quantum mechanical systems, like elementary particles. All systems are quantum (including the universe as a whole).
- Everett shows that the collapse of the state vector, something originally thought to be outside of Schrödinger’s theory, can be shown to arise within the universal [Schrödinger] wave function.
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July 11th, 2012
Word of the Week: Decoherence
Definition: A loss of coherence between the angles of components in a superposition and a loss of information due to environment, which gives the appearance of a wave function collapse.
More about the term: A wave function collapse occurs when the outcome of a quantum state is determined by an observer. An observer can be a concious observer or even the interaction of particles. Instead of a determinate state, decoherence is akin to pulling one string out from an entire knot of strings. Decoherence is a major talking point and factor in multiverse scenarios.
In 1956 Hugh Everett III published his Ph.D. dissertation titled “The Theory of the Universal Wave Function.” In this paper Everett argued for the relative state formulation of quantum theory and a quantum philosophy, which denied wave collapse. Initially, this interpretation was highly criticized by the physics community and when Everett visited Niels Bohr in Copenhagen in 1959 Bohr was unimpressed with Everett’s most recent development.
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April 24th, 2012
I’ll be the first to admit that settling on an interpretation of quantum mechanics can be very difficult. I’ve always preferred my science to be deterministic. This appears in many interpretations such as Many-Minds and Many-Worlds. A less controversial interpretation is the de Broglie-Bohm interpretation. Below is an introduction to the theory taken from a paper by Ward Struyve.
In de Broglie’s pilot-wave theory the description of a quantum system by means of the wavefunction is extended by considering point particles which follow deﬁnite trajectories. The velocity ﬁeld of these particles is fully determined by the wavefunction. Given the initial positions of the particles, their trajectories are fully determined by this velocity ﬁeld. In this sense the particles are ‘piloted’ by the wavefunction, hence the name pilotwave theory.
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February 8th, 2012
The Word of the Week is: Multiverse
Definition: The term to designate the existence of many worlds or universes. Contrary to just one world, a uni-verse, there are many worlds, a multi-verse.
More about the term: The multiverse is not monolithic but it is modeled after the contemporary understanding of an inflationary model of the beginning of this universe suggesting a plurality of worlds. Max Tegmark has championed the most prominent versions of the multiverse. There are four levels of the multiverse.
- Level One: The level one is, for the most part, more space beyond the observable universe. So, theoretically, if we were to go to the “edge” of the universe there would be more space. Having this model as a version of the multiverse may be misleading because there is still only one volume, landscape, or system involved. A generic prediction of cosmological inflation is an infinite space, which contains Hubble volumes (what we see in our universe) realizing in all conditions—including an identical copy of each of us about 10^10^29 meters away.
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