35,338 research outputs found

    Resolving the problem of definite outcomes of measurements

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    The heart of the measurement puzzle, namely the problem of definite outcomes, remains unresolved. This paper shows that Josef Jauch's 1968 reduced density operator approach is the solution, even though many question it: The entangled "Measurement State" implies local mixtures of definite but indeterminate eigenvalues even though the MS continues evolving unitarily. A second, independent, argument based on the quantum's nonlocal entanglement with its measuring apparatus shows that the outcomes must be definite eigenvalues because of relativity's ban on instant signaling. Experiments with entangled photon pairs show the MS to be a non-paradoxical superposition of correlations between states rather than a "Schrodinger's cat" superposition of states. Nature's measurement strategy is to shift the superposition--the coherence--from the detected quantum to the correlations between the quantum and its detector, allowing both subsystems to collapse locally to mixtures of definite eigenvalues. This solution implies an innocuous revision of the standard eigenvalue-eigenstate link. Three frequent objections to this solution are rebutted.Comment: 16 pages, 2 figure

    Re-assessment of the state of Schroedinger's cat, final version

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    The quantum state of Schroedinger's cat is usually incorrectly described as a superposition of "dead" and "alive," despite an argument by Rinner and Werner that, locally, the cat should be considered to be in a mixture of non-superposed states. Here, it is rigorously proven that the cat is not in a superposition. This is central to the measurement problem. Nonlocal two-photon interferometry experiments throw further light on the measurement state by probing the effect of a variable phase factor inserted between its superposed terms. These experiments demonstrate that both subsystems really are in locally mixed states rather than superpositions, and they tell us what the measurement state superposition actually superposes. They show that measurement transfers the coherence in Schroedinger's nuclear superposition neither to the cat nor to the nucleus, but only to the correlations between them. This explains the collapse process--but not its subsequent irreversible dissipation--within the context of unitary dynamics with no need for external entities such as the environment, a human mind, other worlds, or collapse mechanisms.Comment: 11 page

    Understanding self and other

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    Interpersonal understanding is rooted in social engagement. The question is: How? What features of intersubjective coordination are essential for the growth of concepts about the mind, and how does development proceed on this basis? Carpendale & Lewis (C&L) offer many telling insights, but their account begs questions about the earliest forms of self-other linkage and differentiation, especially as mediated by processes of identification

    Quantum realism is consistent with quantum facts

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    Despite the unparalleled accuracy of quantum-theoretical predictions across an enormous range of phenomena, the theory's foundations are still in doubt. The theory deviates radically from classical physics, predicts counterintuitive phenomena, and seems inconsistent. The biggest stumbling block is measurement, where the Schrodinger equation's unitary evolution seems inconsistent with collapse. These doubts have inspired a variety of proposed interpretations and alterations of the theory. Most interpretations posit the theory represents only observed appearances rather than reality. The realistic interpretations, on the other hand, posit entities such as other universes, hidden variables, artificial collapse mechanisms, or human minds, that are not found in the standard mathematical formulation. Surprisingly, little attention has been paid to the possibility that the standard theory is both realistic and correct as it stands. This paper examines several controversial issues, namely quantization, field particle duality, quantum randomness, superposition, entanglement, non-locality, and measurement, to argue that standard quantum physics, realistically interpreted, is consistent with all of them.Comment: 25 pages, 5 figures, 1 tabl

    The production of radiation tolerant vacuum phototriodes and their HV filters for the compact muon solenoid endcap electromagnetic calorimeter

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    Particle detectors which will operate at the Large Hadron Collider face unprecedented challenges in both the number of active detector elements and in operating without maintenance in a high radiation environment for many years. In the Compact Muon Solenoid (CMS) detector the scintillating crystal electromagnetic calorimeter uses vacuum photodetectors in the endcap where the lifetime neutron and hadron fluence is too high for the silicon avalanche photodiodes used in the barrel. Over 15000 radiation tolerant vacuum phototriodes (VPT) have been now been produced by industry for the endcap calorimeter. The VPT have to operate in an environment which has both a significant lifetime dose (up to 50 kGy) from electrons and gamma rays and a high neutron fluence (up to nearly 10^15 n.cm^−2 for E > 100 keV). This paper discusses the steps taken during both the development and production of the VPT to ensure that the response to the scintillation light from the lead tungstate scintillator will not be significantly degraded during the operational lifetime of the experiment. Data from the quality assurance procedures and radiation induced degradation of complete VPT devices is presented. Other components of the endcap calorimeter are also exposed to a similarly intense radiation field. The quality assurance procedure used to select the passive components (resistors and capacitors) used in the high-voltage filter cards is described

    Fake Exponential Brownian Motion

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    We construct a fake exponential Brownian motion, a continuous martingale different from classical exponential Brownian motion but with the same marginal distributions, thus extending results of Albin and Oleszkiewicz for fake Brownian motions. The ideas extend to other diffusions.Comment: 8 page

    Hydraulic brake safety valve

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    Safety device, consisting of three separate fluid chambers, insures that two wheels of a brake system continue to function if a failure occurs
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