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2004

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Articles 511 - 517 of 517

Full-Text Articles in Physics

Highest-Quality Modes In Disordered Photonic Crystals, Alexey Yamilov, Hui Cao Jan 2004

Highest-Quality Modes In Disordered Photonic Crystals, Alexey Yamilov, Hui Cao

Physics Faculty Research & Creative Works

We studied the modes of the highest-quality factor Qm in disordered photonic crystals. by varying the strength of disorder, we identified five different scaling regimes of the ensemble averaged (Qm) with the system size. For sufficiently large systems, (Qm) reaches the maximum at some finite degree of disorder, where its value is comparable to the quality factor of an intentionally introduced single defect at the center of a photonic band gap. Near this optimal degree of disorder, we predict a superexponential increase of (Qm) with the system size, due to migration of the frequencies of the highest-quality modes toward the …

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Progress At The Heidelberg Ebit, Jose R. Crespo Lopez-Urrutia, Jean Pierre Braun, Gunter Brenner, Hjalmar Bruhns, Christina Dimopoulou, I. N. Draganic, Daniel Fischer, Antonio J. Gonzalez, A. Lapierre, V. Mironov, Robert Moshammer, R. Soria Orts, Hiroyuki Tawara, M. Trinczek, Joachim Hermann Ullrich Jan 2004

Progress At The Heidelberg Ebit, Jose R. Crespo Lopez-Urrutia, Jean Pierre Braun, Gunter Brenner, Hjalmar Bruhns, Christina Dimopoulou, I. N. Draganic, Daniel Fischer, Antonio J. Gonzalez, A. Lapierre, V. Mironov, Robert Moshammer, R. Soria Orts, Hiroyuki Tawara, M. Trinczek, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

Two years after the relocation of the Heidelberg EBIT, several experiments are already in operation. Spectroscopic measurements in the optical region have delivered the most precise reported wavelengths for highly charged ions, in the case of the forbidden transitions of Ar XIV and Ar XV. The lifetimes of the metastable levels involved in those transitions has been determined with an error of less than 0.2%. A new, fully automatized x-ray crystal spectrometer allows systematic measurements with very high precision and reproducibility. Absolute measurements of the Lyman series of H-like ions are currently underway. Dielectronic recombination studies have yielded information on …

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Renormalization-Group Analysis Of The Generalized Sine-Gordon Model And Of The Coulomb Gas For D > 3 Dimensions, I. Nandori, Ulrich D. Jentschura, Kornel Sailer, Gerhard Soff Jan 2004

Renormalization-Group Analysis Of The Generalized Sine-Gordon Model And Of The Coulomb Gas For D > 3 Dimensions, I. Nandori, Ulrich D. Jentschura, Kornel Sailer, Gerhard Soff

Physics Faculty Research & Creative Works

Renormalization-group (RG) flow equations have been derived for the generalized sine-Gordon model (GSGM) and the Coulomb gas (CG) in d ≥ 3 of dimensions by means of the Wegner-Houghton method, and by way of the real-space RG approach. The UV scaling laws determined by the leading-order terms of the flow equations are in qualitative agreement for all dimensions d ≥ 3, independent of the dimensionality, and in sharp contrast to the special case d=2. For the 4-dimensional GSGM it is demonstrated explicitly (by numerical calculations) that the blocked potential tends to a constant effective potential in the infrared limit, satisfying …

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Loss And Dispersion Analysis Of Microstructured Fibers By Finite-Difference Method, Shangping Guo, Feng Wu, Sacharia Albin, Hsiang Tai, Robert S. Rogowski Jan 2004

Loss And Dispersion Analysis Of Microstructured Fibers By Finite-Difference Method, Shangping Guo, Feng Wu, Sacharia Albin, Hsiang Tai, Robert S. Rogowski

Electrical & Computer Engineering Faculty Publications

The dispersion and loss in microstructured fibers are studied using a full-vectorial compact-2D finite-difference method in frequency-domain. This method solves a standard eigen-value problem from the Maxwell’s equations directly and obtains complex propagation constants of the modes using anisotropic perfectly matched layers. A dielectric constant averaging technique using Ampere’s law across the curved media interface is presented. Both the real and the imaginary parts of the complex propagation constant can be obtained with a high accuracy and fast convergence. Material loss, dispersion and spurious modes are also discussed.

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Geminal Model Chemistry Ii. Perturbative Corrections, V. A. Rassolov, F. Xu, Sophya V. Garashchuk Jan 2004

Geminal Model Chemistry Ii. Perturbative Corrections, V. A. Rassolov, F. Xu, Sophya V. Garashchuk

Faculty Publications

We introduce and investigate a chemical model based on perturbative corrections to the product of singlet-type strongly orthogonal geminals wave function. Two specific points are addressed (i) Overall chemical accuracy of such a model with perturbative corrections at a leading order; (ii) Quality of strong orthogonality approximation of geminals in diverse chemical systems. We use the Epstein–Nesbet form of perturbation theory and show that its known shortcomings disappear when it is used with the reference Hamiltonian based on strongly orthogonal geminals. Application of this model to various chemical systems reveals that strongly orthogonal geminals are well suited for chemical models, …

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Bohmian Dynamics On Subspaces Using Linearized Quantum Force, V. A. Rassolov, Sophya V. Garashchuk Jan 2004

Bohmian Dynamics On Subspaces Using Linearized Quantum Force, V. A. Rassolov, Sophya V. Garashchuk

Faculty Publications

In the de Broglie–Bohm formulation of quantum mechanics the time-dependent Schrödinger equation is solved in terms of quantum trajectories evolving under the influence of quantum and classical potentials. For a practical implementation that scales favorably with system size and is accurate for semiclassical systems, we use approximate quantum potentials. Recently, we have shown that optimization of the nonclassical component of the momentum operator in terms of fitting functions leads to the energy-conserving approximate quantum potential. In particular, linear fitting functions give the exact time evolution of a Gaussian wave packet in a locally quadratic potential and can describe the dominant …

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Observation Of KS0KS0 Resonances In Deep Inelastic Scattering At Hera, S. Chekanov, M. Derrick, D. Krakauer, J. H. Loizides, S. Magill, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi Jan 2004

Observation Of KS0KS0 Resonances In Deep Inelastic Scattering At Hera, S. Chekanov, M. Derrick, D. Krakauer, J. H. Loizides, S. Magill, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi

Faculty Publications

Inclusive Ks0Ks0 production in deep inelastic ep scattering at HERA has been studied with the ZEUS detector using an integrated luminosity of 120 pb-1. Two states are observed at masses of 1537-8-9 MeV and 1726 ± 7 MeV, as well as an enhancement around 1300 MeV. The state at 1537 MeV is consistent with the well established f′2(1525). The state at 1726 MeV may be the glueball candidate f0(1710). However, it's width of 38 -14-20 MeV is narrower than 125 ± 10 MeV observed by previous experiments for the f0(1710). © 2003 Elsevier B.V. All rights reserved.

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