Jesper Larsson

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The macroscopic characteristics of a material are determined by its elementary excitations, which dictate the response of the system to external stimuli. The spectrum of excitations is related to fluctuations in the density–density correlations and is typically measured through frequency-domain neutron1 or X-ray2–4 scattering. Time-domain measurements of(More)
We report on radio-to-γ -ray observations during 2011 May–September of PMN J0948+0022, the first narrow-line Seyfert 1 (NLSy1) galaxy detected in γ -rays by Fermi-Large Area Telescope. Strong variability was observed in γ -rays, with two flaring periods peaking on 2011 June 20 and July 28. The variability observed in optical and near-infrared seems to have(More)
A. M. Lindenberg,1 I. Kang,1 S. L. Johnson,1 T. Missalla,2,5 P. A. Heimann,2 Z. Chang,3 J. Larsson,4 P. H. Bucksbaum,3 H. C. Kapteyn,3 H. A. Padmore,2 R. W. Lee,5 J. S. Wark,6 and R. W. Falcone1,7 1Department of Physics, University of California, Berkeley, California 94720 2Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California(More)
We argue the need for algorithms for collective communication operations that can exploit the hierarchical structure of contemporary parallel systems like clusters of symmetric multiprocessors (SMPs). We support the argument by results achieved on a 16 node, dual-processor PC cluster with very simple improvements to commonly used implementations of(More)
High-intensity X-ray pulses from third-generation synchrotron sources make it possible to study the temporal dynamics of rapidly evolving materials. We report a study of rapid and reversible disordering of the structure of an InSb crystal induced by an ultrashort laser pulse. A novel crosscorrelation detection technique is described, which allowed us to(More)
We report on measurements of the light absorption efficiency of InSb nanowires. The absorbed 70 fs light pulse generates carriers, which equilibrate with the lattice via electron-phonon coupling. The increase in lattice temperature is manifested as a strain that can be measured with X-ray diffraction. The diffracted X-ray signal from the excited sample was(More)
We report the first molecular line survey of Supernova 1987A in the millimetre wavelength range. In the ALMA 210–300 and 340–360 GHz spectra, we detected cold (20–170 K) CO, 28SiO, HCO and SO, with weaker lines of 29SiO from ejecta. This is the first identification of HCO and SO in a young supernova remnant. We find a dip in the J=6–5 and 5–4 SiO line(More)
We report on multifrequency observations performed during 2012 December–2013 August of the first narrow-line Seyfert 1 galaxy detected in γ rays, PMN J0948+0022 (z = 0.5846). A γ-ray flare was observed by the Large Area Telescope on board Fermi during 2012 December–2013 January, reaching a daily peak flux in the 0.1–100 GeV energy range of (155 ± 31)×10 ph(More)
We have studied an X-ray switch based on a gold coated indium antimonide crystal using time-resolved X-ray diffraction and demonstrated that the switch could reduce the pulse duration of a 100 ps X-ray pulse down to 20 ps with a peak reflectivity of 8%. We have used a dynamical diffraction code to predict the performance of the switch, which was then(More)