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Gadi Shimon Perets 《Israel Journal of Mathematics》1993,83(3):361-368
We construct a family of modules over Weyl algebras with the property of being non-simple of finite length and alsod-critical (i.e.d(M)>d(M/N) for every non-trivial submoduleN, ofM). Hered stands for the Gelfand-Kirillov dimension. We further study some properties of these modules. 相似文献
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Vidali G Pirronello V Li L Roser J Manicó G Congiu E Mehl H Lederhendler A Perets HB Brucato JR Biham O 《The journal of physical chemistry. A》2007,111(49):12611-12619
The study of the formation of molecular hydrogen on low-temperature surfaces is of interest both because it enables the exploration of elementary steps in the heterogeneous catalysis of a simple molecule and because of its applications in astrochemistry. Here, we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments, beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations, and the energy barriers of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results are used in order to evaluate the formation rate of H2 on dust grains under the actual conditions present in interstellar clouds. It is found that, under typical conditions in diffuse interstellar clouds, amorphous silicate grains are efficient catalysts of H2 formation when the grain temperatures are between 9 and 14 K. This temperature window is within the typical range of grain temperatures in diffuse clouds. It is thus concluded that amorphous silicates are good candidates to be efficient catalysts of H2 formation in diffuse clouds. 相似文献
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Bobeldijk I Bouwhuis M Ireland DG de Jager CW Jans E de Jonge N Kasdorp WJ Konijn J Lapikás L van Leeuwe JJ van der Meer RL Nooren GJ Passchier E Schroevers M van der Steenhoven G Steijger JJ Theunissen JA van Uden MA de Vries H de Vries R de Witt Huberts PK Blok HP van den Brink HB Dodge GE Harakeh MN Hesselink WH Kalantar-Nayestanaki N Pellegrino A Spaltro CM Templon JA Hicks RS Kelly JJ Marchand C 《Physical review letters》1994,73(20):2684-2687
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Perets HB Lahini Y Pozzi F Sorel M Morandotti R Silberberg Y 《Physical review letters》2008,100(17):170506
Quantum random walks are the quantum counterpart of classical random walks, and were recently studied in the context of quantum computation. Physical implementations of quantum walks have only been made in very small scale systems severely limited by decoherence. Here we show that the propagation of photons in waveguide lattices, which have been studied extensively in recent years, are essentially an implementation of quantum walks. Since waveguide lattices are easily constructed at large scales and display negligible decoherence, they can serve as an ideal and versatile experimental playground for the study of quantum walks and quantum algorithms. We experimentally observe quantum walks in large systems ( approximately 100 sites) and confirm quantum walks effects which were studied theoretically, including ballistic propagation, disorder, and boundary related effects. 相似文献