1,143 research outputs found

    Dynamic scaling of fronts in the quantum XX chain

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    The dynamics of the transverse magnetization in the zero-temperature XX chain is studied with emphasis on fronts emerging from steplike initial magnetization profiles. The fronts move with fixed velocity and display a staircase like internal structure whose dynamic scaling is explored both analytically and numerically. The front region is found to spread with time sub-diffusively with the height and the width of the staircase steps scaling as t^(-1/3) and t^1/3, respectively. The areas under the steps are independent of time, thus the magnetization relaxes in quantized "steps" of spin-flips.Comment: 4 pages, 3 eps figures, RevTe

    Observation of Anomalous Internal Pair Creation in 8^8Be: A Possible Signature of a Light, Neutral Boson

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    Electron-positron angular correlations were measured for the isovector magnetic dipole 17.6 MeV state (Jπ=1+J^\pi=1^+, T=1T=1) \rightarrow ground state (Jπ=0+J^\pi=0^+, T=0T=0) and the isoscalar magnetic dipole 18.15 MeV (Jπ=1+J^\pi=1^+, T=0T=0) state \rightarrow ground state transitions in 8^{8}Be. Significant deviation from the internal pair creation was observed at large angles in the angular correlation for the isoscalar transition with a confidence level of >5σ> 5\sigma. This observation might indicate that, in an intermediate step, a neutral isoscalar particle with a mass of 16.70±0.35\pm0.35 (stat)±0.5\pm 0.5 (sys) MeV/c2/c^2 and Jπ=1+J^\pi = 1^+ was created.Comment: 5 pages, 5 figure

    Transmission resonance spectroscopy in the third minimum of 232Pa

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    The fission probability of 232Pa was measured as a function of the excitation energy in order to search for hyperdeformed (HD) transmission resonances using the (d,pf) transfer reaction on a radioactive 231Pa target. The experiment was performed at the Tandem accelerator of the Maier-Leibnitz Laboratory (MLL) at Garching using the 231Pa(d,pf) reaction at a bombarding energy of E=12 MeV and with an energy resolution of dE=5.5 keV. Two groups of transmission resonances have been observed at excitation energies of E=5.7 and 5.9 MeV. The fine structure of the resonance group at E=5.7 MeV could be interpreted as overlapping rotational bands with a rotational parameter characteristic to a HD nuclear shape. The fission barrier parameters of 232Pa have been determined by fitting TALYS 1.2 nuclear reaction code calculations to the overall structure of the fission probability. From the average level spacing of the J=4 states, the excitation energy of the ground state of the 3rd minimum has been deduced to be E(III)=5.05 MeV.Comment: 6 pages, 8 figure

    Elastic properties of grafted microtubules

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    We use single-particle tracking to study the elastic properties of single microtubules grafted to a substrate. Thermal fluctuations of the free microtubule's end are recorded, in order to measure position distribution functions from which we calculate the persistence length of microtubules with contour lengths between 2.6 and 48 micrometers. We find the persistence length to vary by more than a factor of 20 over the total range of contour lengths. Our results support the hypothesis that shearing between protofilaments contributes significantly to the mechanics of microtubules.Comment: 9 pages, 3 figure

    Low-lying GT(+) strength in Co-64 studied via the Ni-64(d,He-2)Co-64 reaction

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    The Ni-64(d,He-2)Co-64 reaction was studied at the AGOR cyclotron of KVI, Groningen, with the Big-Bite Spectrometer and the EuroSuperNova detector using a 171-MeV deuteron beam. An energy resolution of about 110 keV was achieved. In addition to the J(pi) = 1(+) ground state, several other 1(+) states could be identified in Co-64 and the strengths of the corresponding Gamow-Teller transitions were determined. The obtained strength distribution was compared with theoretical predictions and former (n,p) experimental results and displayed a good agreement. Due to the good energy resolution, detailed spectroscopic information was obtained, which supplements the data base needed for network calculations for supernova scenarios

    Systematic investigation of the elastic proton-deuteron differential cross section at intermediate energies

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    To investigate the importance of three-nucleon forces (3NF) systematically over a broad range of intermediate energies, the differential cross sections of elastic proton-deuteron scattering have been measured at proton bombarding energies of 108, 120, 135, 150, 170 and 190 MeV at center-of-mass angles between 3030^\circ and 170170^\circ. Comparisons with Faddeev calculations show unambiguously the shortcomings of calculations employing only two-body forces and the necessity of including 3NF. They also show the limitations of the latest few-nucleon calculations at backward angles, especially at higher beam energies. Some of these discrepancies could be partially due to relativistic effects. Data at lowest energy are also compared with a recent calculation based on \chipt

    Human-human, human-machine communication: on the HuComTech multimodal corpus

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    The present paper describes HuComTech, a multimodal corpus featuring over 50 hours of video taped interviews with 112 informants. The interviews were carried out in a lab equipped with multiple cameras and microphones able to record posture, hand gestures, facial expressions, gaze etc. as well as the acoustic and linguistic features of what was said. As a result of large-scale manual and semi-automatic annotation, the HuComTech corpus offers a rich dataset on 47 annotation levels. The paper presents the objectives, the workflow, the annotation work, focusing on two aspects in particular i.e. time alignment made with the Leipzig tool WEBMaus and the automatic detection of intonation contours developed by the HuComTech team. Early exploitation of the corpus included analysis of hidden patterns with the use of sophisticated multivariat analysis of temporal relations within the data points. The HuComTech corpus is one o the flagship language resources available through the HunCLARIN repositor
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