21,365 research outputs found

    From computation to black holes and space-time foam

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    We show that quantum mechanics and general relativity limit the speed ν~\tilde{\nu} of a simple computer (such as a black hole) and its memory space II to \tilde{\nu}^2 I^{-1} \lsim t_P^{-2}, where tPt_P is the Planck time. We also show that the life-time of a simple clock and its precision are similarly limited. These bounds and the holographic bound originate from the same physics that governs the quantum fluctuations of space-time. We further show that these physical bounds are realized for black holes, yielding the correct Hawking black hole lifetime, and that space-time undergoes much larger quantum fluctuations than conventional wisdom claims -- almost within range of detection with modern gravitational-wave interferometers.Comment: A misidentification of computer speeds is corrected. Our results for black hole computation now agree with those given by S. Lloyd. All other conclusions remain unchange

    Probing spacetime foam with extragalactic sources

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    Due to quantum fluctuations, spacetime is probably ``foamy'' on very small scales. We propose to detect this texture of spacetime foam by looking for core-halo structures in the images of distant quasars. We find that the Very Large Telescope interferometer will be on the verge of being able to probe the fabric of spacetime when it reaches its design performance. Our method also allows us to use spacetime foam physics and physics of computation to infer the existence of dark energy/matter, independent of the evidence from recent cosmological observations.Comment: LaTeX, 11 pages, 1 figure; version submitted to PRL; several references added; very useful comments and suggestions by Eric Perlman incorporate

    Comparison of chemical profiles and effectiveness between Erxian decoction and mixtures of decoctions of its individual herbs : a novel approach for identification of the standard chemicals

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    Acknowledgements This study was partially supported by grants from the Seed Funding Programme for Basic Research (Project Number 201211159146 and 201411159213), the University of Hong Kong. We thank Mr Keith Wong and Ms Cindy Lee for their technical assistances.Peer reviewedPublisher PD

    Electronic theory for the normal state spin dynamics in Sr2_2RuO4_4: anisotropy due to spin-orbit coupling

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    Using a three-band Hubbard Hamiltonian we calculate within the random-phase-approximation the spin susceptibility, χ(q,ω)\chi({\bf q},\omega), and NMR spin-lattice relaxation rate, 1/T1_1, in the normal state of the triplet superconductor Sr2_2RuO4_4 and obtain quantitative agreement with experimental data. Most importantly, we find that due to spin-orbit coupling the out-of-plane component of the spin susceptibility χzz\chi^{zz} becomes at low temperatures two times larger than the in-plane one. As a consequence strong incommensurate antiferromagnetic fluctuations of the quasi-one-dimensional xzxz- and yzyz-bands point into the zz-direction. Our results provide further evidence for the importance of spin fluctuations for triplet superconductivity in Sr2_2RuO4_4.Comment: revised versio

    On the Stability and the Approximation of Branching Distribution Flows, with Applications to Nonlinear Multiple Target Filtering

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    We analyse the exponential stability properties of a class of measure-valued equations arising in nonlinear multi-target filtering problems. We also prove the uniform convergence properties w.r.t. the time parameter of a rather general class of stochastic filtering algorithms, including sequential Monte Carlo type models and mean eld particle interpretation models. We illustrate these results in the context of the Bernoulli and the Probability Hypothesis Density filter, yielding what seems to be the first results of this kind in this subject
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