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2002

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Articles 421 - 425 of 425

Full-Text Articles in Physics

Unequal Arm Space-Borne Gravitational Wave Detectors, Shane L. Larson, Ronald W. Hellings, William A. Hiscock Jan 2002

Unequal Arm Space-Borne Gravitational Wave Detectors, Shane L. Larson, Ronald W. Hellings, William A. Hiscock

All Physics Faculty Publications

Unlike ground-based interferometric gravitational wave detectors, large space-based systems will not be rigid structures. When the end stations of the laser interferometer are freely flying spacecraft, the armlengths will change due to variations in the spacecraft positions along their orbital trajectories, so the precise equality of the arms that is required in a laboratory interferometer to cancel laser phase noise is not possible. However, using a method discovered by Tinto and Armstrong, a signal can be constructed in which laser phase noise exactly cancels out, even in an unequal arm interferometer. We examine the case where the ratio of the …

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Calculation Of Spectral Degradation Due To Contaminant Films On Infrared And Optical Sensors, L. Gamble, John R. Dennison, B. Wood, J. Herrick, J. S. Dyer Jan 2002

Calculation Of Spectral Degradation Due To Contaminant Films On Infrared And Optical Sensors, L. Gamble, John R. Dennison, B. Wood, J. Herrick, J. S. Dyer

All Physics Faculty Publications

Molecular surface contaminants can cause degradation of optical systems, especially if the contaminants exhibit strong absorption bands in the region of interest. Different strategies for estimation of spectral degradation responses due to uniform films for various types of systems are reviewed. One tool for calculating the effects of contaminant film thickness on signal degradation in the mid IR region is the simulation program CALCRT. The CALCRT database will be reviewed to correlate spectral n and k values associated with specific classes of organic functional groups. Various schemes are also investigated to estimate the spectral degradation in the UV-Vis region. Experimental …

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Optimal Simulation Of Two-Qubit Hamiltonians Using General Local Operations, C. H. Bennett, J. I. Cirac, Matthew S. Leifer, D. W. Leung, N. Linden, S. Popescu, G. Vidal Jan 2002

Optimal Simulation Of Two-Qubit Hamiltonians Using General Local Operations, C. H. Bennett, J. I. Cirac, Matthew S. Leifer, D. W. Leung, N. Linden, S. Popescu, G. Vidal

Mathematics, Physics, and Computer Science Faculty Articles and Research

We consider the simulation of the dynamics of one nonlocal Hamiltonian by another, allowing arbitrary local resources but no entanglement or classical communication. We characterize notions of simulation, and proceed to focus on deterministic simulation involving one copy of the system. More specifically, two otherwise isolated systems A and B interact by a nonlocal Hamiltonian H≠HA+HB . We consider the achievable space of Hamiltonians H8 such that the evolution e2iH8t can be simulated by the interaction H interspersed with local operations. For any dimensions of A and B, and any nonlocal Hamiltonians H and H8, there exists a scale factor …

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Group-Fitted Ab Initio Single- And Multiple-Scattering Exafs Debye-Waller Factors, N. Dimakis, Grant Bunker Jan 2002

Group-Fitted Ab Initio Single- And Multiple-Scattering Exafs Debye-Waller Factors, N. Dimakis, Grant Bunker

Physics and Astronomy Faculty Publications and Presentations

X-ray absorption fine structure (XAFS) spectroscopy is one of the few direct probes of the structure of metalloprotein binding that is equally applicable to proteins in crystals, solutions, and membranes. Despite considerable progress in the calculation of the photoelectron scattering aspects of XAFS, calculation of the vibrational aspects has lagged because of the difficulty of the calculations. We report here initial results that express single- and multiple-scattering Debye-Waller factors as polynomial functions of first shell radial distance for metal-peptide complexes, enabling quantitatively accurate full multiple-scattering XAFS data analysis of active sites of unknown structure at arbitrary temperatures without the use …

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Correlation Functions Near Modulated And Rough Surfaces, Andreas Hanke, Mehran Kardar Jan 2002

Correlation Functions Near Modulated And Rough Surfaces, Andreas Hanke, Mehran Kardar

Physics and Astronomy Faculty Publications and Presentations

In a system with long-ranged correlations, the behavior of correlation functions is sensitive to the presence of a boundary. We show that surface deformations strongly modify this behavior as compared to a flat surface. The modified near surface correlations can be measured by scattering probes. To determine these correlations, we develop a perturbative calculation in the deformations in height from a flat surface. Detailed results are given for a regularly patterned surface, as well as for a self-affinely rough surface with roughness exponent ζ. By combining this perturbative calculation in height deformations with the field-theoretic renormalization-group approach, we also estimate …

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