36,012 research outputs found

    Expansions of the real field by open sets: definability versus interpretability

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    An open set U of the real numbers R is produced such that the expansion (R,+,x,U) of the real field by U defines a Borel isomorph of (R,+,x,N) but does not define N. It follows that (R,+,x,U) defines sets in every level of the projective hierarchy but does not define all projective sets. This result is elaborated in various ways that involve geometric measure theory and working over o-minimal expansions of (R,+,x). In particular, there is a Cantor subset K of R such that for every exponentially bounded o-minimal expansion M of (R,+,x), every subset of R definable in (M,K) either has interior or is Hausdorff null.Comment: 14 page

    Distances of qubit density matrices on Bloch sphere

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    We recall the Einstein velocity addition on the open unit ball \B of R3\R^{3} and its algebraic structure, called the Einstein gyrogroup. We establish an isomorphism between the Einstein gyrogroup on \B and the set of all qubit density matrices representing mixed states endowed with an appropriate addition. Our main result establishes a relation between the trace metric for the qubit density matrices and the rapidity metric on the Einstein gyrogroup \B.Comment: I thank to my supervisor, Jimmie Lawson. This was accepted in Journal of Mathematical Physics at September 26, 201

    Quantum Lattice Fluctuations and Luminescence in C_60

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    We consider luminescence in photo-excited neutral C_60 using the Su-Schrieffer-Heeger model applied to a single C_60 molecule. To calculate the luminescence we use a collective coordinate method where our collective coordinate resembles the displacement of the carbon atoms of the Hg(8) phonon mode and extrapolates between the ground state "dimerisation" and the exciton polaron. There is good agreement for the existing luminescence peak spacing and fair agreement for the relative intensity. We predict the existence of further peaks not yet resolved in experiment. PACS Numbers : 78.65.Hc, 74.70.Kn, 36.90+

    Children hold owners responsible when property causes harm

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    Since ancient times, legal systems have held owners responsible for harm caused by their property. Across 4 experiments, we show that children aged 3–7 also hold owners responsible for such harm. Older children judge that owners should repair harm caused by property, and younger children may do this as well. Younger and older children judge that owners should apologize for harm, even when children do not believe the owners allowed the harm to occur. Children are also as likely to hold owners responsible for harm caused by property as for harm caused by the owners themselves. The present findings contribute to psychological accounts of ownership by showing that ownership not only confers rights to control property, but also responsibility for harm caused by property. The findings also contribute to our understanding of the attribution of responsibility, and challenge accounts claiming that directly causing harm, or allowing it to happen, is a prerequisite for responsibility. The findings provide support for an account claiming that property is an extension of its owner, and likewise reveal that responsibility for harm caused by property is an early developing aspect of the psychology of ownership. 2018 APA, all rights reserved

    Medical Information Management System (MIMS): A generalized interactive information system

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    An interactive information system is described. It is a general purpose, free format system which offers immediate assistance where manipulation of large data bases is required. The medical area is a prime area of application. Examples of the system's operation, commentary on the examples, and a complete listing of the system program are included

    Non-equilibrium Magnetization Dynamics in the Fe_8 Single-Molecule Magnet Induced by High-Intensity Microwave Radiation

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    Resonant microwave radiation applied to a single crystal of the molecular magnet Fe_8 induces dramatic changes in the sample's magnetization. Transitions between excited states are found even though at the nominal system temperature these levels have negligible population. We find evidence that the sample heats significantly when the resonance condition is met. In addition, heating is observed after a short pulse of intense radiation has been turned off, indicating that the spin system is out of equilibrium with the lattice.Comment: Version to appear in Europhysics Letters. Minor changes and updated reference

    Faraday spectroscopy of atoms confined in a dark optical trap

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    We demonstrate Faraday spectroscopy with high duty cycle and sampling rate using atoms confined to a blue-detuned optical trap. Our trap consists of a crossed pair of high-charge-number hollow laser beams, which forms a dark, box-like potential. We have used this to measure transient magnetic fields in a 500-micron-diameter spot over a 400 ms time window with nearly unit duty cycle at a 500 Hz sampling rate. We use these measurements to quantify and compensate time-varying magnetic fields to ~10 nT per time sample.Comment: 6 pages, 8 figures Accepted in Phys. Rev.

    Experimental Upper Bound on Superradiance Emission from Mn12 Acetate

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    We used a Josephson junction as a radiation detector to look for evidence of the emission of electromagnetic radiation during magnetization avalanches in a crystal assembly of Mn_12-Acetate. The crystal assembly exhibits avalanches at several magnetic fields in the temperature range from 1.8 to 2.6 K with durations of the order of 1 ms. Although a recent study shows evidence of electromagnetic radiation bursts during these avalanches [J. Tejada, et al., Appl. Phys. Lett. {\bf 84}, 2373 (2004)], we were unable to detect any significant radiation at well-defined frequencies. A control experiment with external radiation pulses allows us to determine that the energy released as radiation during an avalanche is less than 1 part in 10^4 of the total energy released. In addition, our avalanche data indicates that the magnetization reversal process does not occur uniformly throughout the sample.Comment: 4 RevTeX pages, 3 eps figure
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