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Saturday, June 30, 2007

Top-down structure of reality, which defies attempts to model it from the bottom up

The Pondicherry interpretation of quantum mechanics: An overview Ulrich Mohrhoff
An overview of the Pondicherry interpretation of quantum mechanics is presented. This interpretation proceeds from the recognition that the fundamental theoretical framework of physics is a probability algorithm, which serves to describe an objective fuzziness (the literal meaning of Heisenberg’s term “Unschaerfe,” usually mistranslated as “uncertainty”) by assigning objective probabilities to the possible outcomes of unperformed measurements. Although it rejects attempts to construe quantum states as evolving ontological states, it arrives at an objective description of the quantum world that owes nothing to observers or the goings-on in physics laboratories. In fact, unless such attempts are rejected, quantum theory’s true ontological implications cannot be seen. Among these are the radically relational nature of space, the numerical identity of the corresponding relata, the incomplete spatiotemporal differentiation of the physical world, and the consequent top-down structure of reality, which defies attempts to model it from the bottom up, whether on the basis of an intrinsically differentiated spacetime manifold or out of a multitude of individual building blocks.
Quantum mechanics needs no interpretation L. Skala, V. Kapsa
Probabilistic description of results of measurements and its consequences for understanding quantum mechanics are discussed. It is shown that the basic mathematical structure of quantum mechanics like the probability amplitude, Born rule, probability density current, commutation relations, momentum operator, uncertainty relations, rules for including the scalar and vector potentials and existence of antiparticles can be derived from the definition of the mean values of the space coordinates and time. Equations of motion of quantum mechanics, the Klein-Gordon equation, Schroedinger equation and Dirac equation are obtained from requirement of the relativistic invariance of the theory. Limit case of localized probability densities leads to the Hamilton-Jacobi equation of classical mechanics. Many particle systems are also discussed.
Non-unitary evolution of a pure state into a mixed state in the measurement problem from standard Quantum Mechanics and its impact on complex space-time, no-boundary proposal and information loss paradox of singularity-free Quantum Cosmology Pradip Kumar Chatterjee
In order to resolve the measurement problem of Quantum Mechanics, non-unitary time evolution has been derived from the unitarity of standard quantum formalism. New wave functions of free and non-free quantum systems follow from Schroedinger equation after inserting an ansatz. Quantum systems show up as probability waves before measurement. A pure entangled state of a composite system evolves non-unitarily, only to disentangle itself into a definite state after reduction at the measurement point. A classical space-time point is created momentarily in this event. Unitarity is restored at that point. The non-Hermitian observables defined in the domain of rigged Hilbert space transform into Hermitian ones at the measurement point. The problem of preferred basis is resolved by the requirement of specifying the position of measurement point. Two theorems prove that time is a non-Hermitian operator, thus placing space and time on an equal footing. Bound states are found to need discrete space-time, which supports its use in loop quantum gravity. Non-unitarity in the theory helps buttress the no-boundary proposal; and uncertainty relation makes a leeway to singularity-free Quantum Cosmology. Quantum Mechanics also accommodates complex and negative probabilities.
This entry was posted on Thursday, June 28th, 2007 at 9:31 pm and is filed under How...odd..., Foundational Quantum Mechanics, In Retrospect..., Operating Systems. by angryphysicist

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