HAMEV and SQRED: Fortran 77 Subroutines for Computing the Eigenvalues of Hamiltonian Matrices Using Van Loanss Square Reduced Method

This paper describes LAPACK-based Fortran 77 subroutines for the reduction of a Hamiltonian matrix to square-reduced form and the approximation of all its eigenvalues using the implicit version of Van Loan's method. The transformation of the Hamilto- nian matrix to a square-reduced Hamiltonian uses only orthogonal symplectic similarity transformations. The eigenvalues can then be determined by applying the Hessenberg QR iteration to a matrix of half the order of the Hamiltonian matrix and taking the square roots of the computed values. Using scaling strategies similar to those suggested for algebraic Riccati equations can in some cases improve the accuracy of the computed eigenvalues. We demonstrate the performance of the subroutines for several examples and show how they can be used to solve some control-theoretic problems

Patients’ quest for recognition and continuity in health care: time for a new research agenda?

User involvement is important in democratization of health care and is assumed to contribute to better and more relevant research. Despite increased requirements for user involvement in research, more studies are still needed. This study aimed at exploring what research agenda people with varied health problems consider as important, based on their own experience. The study had a phenomenological approach with a qualitative design. The sample consisted of 23 informants; nine had been critically ill and 14 were suffering from chronic muscle pain. Data were collected in five focus group interviews and one individual interview. A phenomenological approach was used in analyzing the data. Written consent was obtained from all the participants, and ethical considerations were taken throughout the entire research process. Despite various experiences among the participants, a quest to be taken seriously over time by healthcare professionals emerged as a strong meaning structure in both groups. Based on these experiences, continuity across lifetime changes turned out to be an important research topic for future research. User involvement should be appreciated in all parts of the research process. A crucial prerequisite is that the users get the opportunity to bring their own experiences into the process.acceptedVersio

Electron-hole correlation effects in the emission of light from quantum wires

We present a self-consistent treatment of the electron-hole correlations in optically excited quantum wires within the ladder approximation, and using a contact potential interaction. The limitations of the ladder approximation to the excitonic low-density region are largely overcome by the introduction of higher order correlations through self consistency. We show relevance of these correlations in the low-temperature emission, even for high density relevant in lasing, when large gain replaces excitonic absorption.Comment: 4 paes 3 figure

The Paranormal is (Still) Normal: The Sociological Implications of a Survey of Paranormal Experiences in Great Britain

Historically, there has been limited sociological interest in the paranormal and no systematic study of reported paranormal experiences. There are also few medium-to-large-scale survey results with nationally representative populations focusing on paranormal experiences. This paper provides details of an exploratory survey conducted in 2009 with a nationally representative sample of 4,096 adults aged 16 years and over across Great Britain. Our findings show that 37% of British adults report at least one paranormal experience and that women, those who are middle-aged or individuals resident in the South West are more likely to report such experiences. These results establish incidence levels of reported paranormal experiences in contemporary Britain. We argue also that they merit a more sustained sociological consideration of the paranormal. In this respect we renew and update the robust justification and call for serious research positioning the paranormal as a social phenomenon, originally proposed well over thirty years ago by Greeley (1975)

Parallel computation of 3-D soil-structure interaction in time domain with a coupled FEM/SBFEM approach

The final publication is available at Springer via http://dx.doi.org/10.1007/s10915-011-9551-xThis paper introduces a parallel algorithm for the scaled boundary finite element method (SBFEM). The application code is designed to run on clusters of computers, and it enables the analysis of large-scale soil-structure-interaction problems, where an unbounded domain has to fulfill the radiation condition for wave propagation to infinity. The main focus of the paper is on the mathematical description and numerical implementation of the SBFEM. In particular, we describe in detail the algorithm to compute the acceleration unit impulse response matrices used in the SBFEM as well as the solvers for the Riccati and Lyapunov equations. Finally, two test cases validate the new code, illustrating the numerical accuracy of the results and the parallel performances. © Springer Science+Business Media, LLC 2011.Jose E. Roman and Enrique S. Quintana-Orti were partially supported by the Spanish Ministerio de Ciencia e Innovacion under grants TIN2009-07519, and TIN2008-06570-C04-01, respectively.Schauer, M.; Román Moltó, JE.; Quintana Orti, ES.; Langer, S. (2012). Parallel computation of 3-D soil-structure interaction in time domain with a coupled FEM/SBFEM approach. Journal of Scientific Computing. 52(2):446-467. doi:10.1007/s10915-011-9551-xS446467522Anderson, E., Bai, Z., Bischof, C., Demmel, J., Dongarra, J., Croz, J.D., Greenbaum, A., Hammarling, S., McKenney, A., Sorensen, D.: LAPACK User’s Guide. Society for Industrial and Applied Mathematics, Philadelphia (1992)Antes, H., Spyrakos, C.: Soil-structure interaction. In: Beskos, D., Anagnotopoulos, S. (eds.) Computer Analysis and Design of Earthquake Resistant Structures, p. 271. Computational Mechanics Publications, Southampton (1997)Appelö, D., Colonius, T.: A high-order super-grid-scale absorbing layer and its application to linear hyperbolic systems. J. Comput. 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Algorithms 20(1), 75–100 (1999)Benner, P., Byers, R., Quintana-Ortí, E., Quintana-Ortí, G.: Solving algebraic Riccati equations on parallel computers using Newton’s method with exact line search. Parallel Comput. 26(10), 1345–1368 (2000)Benner, P., Quintana-Ortí, E.S., Quintana-Ortí, G.: Solving linear-quadratic optimal control problems on parallel computers. Optim. Methods Softw. 23(6), 879–909 (2008)Bettess, P.: Infinite Elements. Penshaw Press, Sunderland (1992)Blackford, L.S., Choi, J., Cleary, A., D’Azevedo, E., Demmel, J., Dhillon, I., Dongarra, J., Hammarling, S., Henry, G., Petitet, A., Stanley, K., Walker, D., Whaley, R.C.: ScaLAPACK Users’ Guide. Society for Industrial and Applied Mathematics, Philadelphia (1997)Borsutzky, R.: Braunschweiger Schriften zur Mechanik - Seismic Risk Analysis of Buried Lifelines, vol. 63. Mechanik-Zentrum Technische Universität. Braunschweig (2008)Dongarra, J.J., Whaley, R.C.: LAPACK working note 94: A user’s guide to the BLACS v1.1. Tech. Rep. 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Continuous, Semi-discrete, and Fully Discretized Navier-Stokes Equations

The Navier--Stokes equations are commonly used to model and to simulate flow phenomena. We introduce the basic equations and discuss the standard methods for the spatial and temporal discretization. We analyse the semi-discrete equations -- a semi-explicit nonlinear DAE -- in terms of the strangeness index and quantify the numerical difficulties in the fully discrete schemes, that are induced by the strangeness of the system. By analyzing the Kronecker index of the difference-algebraic equations, that represent commonly and successfully used time stepping schemes for the Navier--Stokes equations, we show that those time-integration schemes factually remove the strangeness. The theoretical considerations are backed and illustrated by numerical examples.Comment: 28 pages, 2 figure, code available under DOI: 10.5281/zenodo.998909, https://doi.org/10.5281/zenodo.99890

Lightcurves of 20--100 kilometer Kuiper Belt Objects using the Hubble Space Telescope

We report high precision photometry of three small and one larger Kuiper Belt Objects (KBOs) obtained with the Advanced Camera for Surveys onboard the Hubble Space Telescope (ACS/HST). The three small bodies are the smallest KBOs for which lightcurve measurements are available. 2003 BF91 has a diameter of 20 kilometers (assuming 10% albedo) and a 1.09 magnitude, 9.1-hour lightcurve that is feasibly explained by the rotation of an elongated, coherent body that is supported by material strength and best imagined as an icy outer Solar System analog to asteroid (243) Ida. Two other small KBOs, 2003 BG91 and 2003 BH91 (diameters 31 and 18 km, with albedo 10%), exhibit an unremarkable lightcurve and no detectable photometric variation, respectively. For the larger KBO 2000 FV53 (116 km diameter, assuming 10% albedo) we strongly detect a non-sinusoidal periodic (7.5 hours) brightness variation with a very small amplitude (0.07 mag). This KBO may be nearly spherical, a result that might not be unusual in the Kuiper Belt but would be remarkable among outer Solar System satellites of similar size. We carry out a study of possible physical states and bulk densities under the assumptions of both fluid equilibrium and finite, non-zero internal friction. The densities for the these KBOs are likely to be in the range 1--2 g/cm3, and a plausible solution for 2000 FV53 is a rubble pile of this density that is held slightly out of the minimum-energy shape by internal friction among constituent blocks that are relatively small. Our interpretation of 2000 FV53 as a pulverized but essentially primordial object and 2003 BF91 as a collisional fragment is consistent with models of collisional timescales in the outer Solar System. We compile all published KBO lightcurve data and compare our results to the larger population. [abridged]Comment: AJ, in press. Tables 1-4 will be electronic only in published version but appear here in full. Figures 1,3,5 in colo

Strong anisotropy of superexchange in the copper-oxygen chains of La_{14-x}Ca_{x}Cu_{24}O_{41}

Electron spin resonance data of Cu^{2+} ions in La_{14-x}Ca_{x}Cu_{24}O_{41} crystals (x=9,11,12) reveal a very large width of the resonance line in the paramagnetic state. This signals an unusually strong anisotropy of ~10% of the isotropic Heisenberg superexchange in the Cu-O chains of this compound. The strong anisotropy can be explained by the specific geometry of two symmetrical 90 degree Cu-O-Cu bonds, which boosts the importance of orbital degrees of freedom. Our data show the apparent limitations of the applicability of an isotropic Heisenberg model to the low dimensional cuprates.Comment: 14 pages, 3 figures included, to be published in Phys. Rev. Let