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341.
V. R. Gavrilov V. D. Ivashchuk U. Kasper V. N. Melnikov 《General Relativity and Gravitation》1997,29(5):599-612
The multidimensional cosmological model describing the evolution of n Einstein spaces in the presence of multicomponent perfect fluid is considered. We define vectors related to the equations of state of the components. If they are orthogonal with respect to the minisuperspace metric, the Einstein equations are integrable and a Kasner-like form of the solutions is presented. For special sets of parameters the cosmological model is reduced to the Euclidean Toda-like system connected with some Lie algebra. The integrable vacuum (1+5+5)-model with two 5-dimensional Einstein spaces and non-zero Ricci tensors is obtained. Its reduction to a (1+5+3+2)-solution is given. For a special choice of the integration constant and one of the spaces (M1 = S5) a non-singular solution with the topology
is obtained. 相似文献
342.
U. Kasper 《International Journal of Theoretical Physics》1992,31(6):1007-1014
Thermodynamic quantities and those describing the source of gravitational fields need not be identified. The standard approach is to identify them. If one does not follow this way, one opens the possibility of describing, on the level of phenomenology, the average of the quantum physical process behind the creation of particles and entropy in a comoving volume. Different approaches are briefly discussed. A variational principle with constraints modeling particle and entropy creation is formulated and leads to higher-order gravity field equations. They suggest on the level of phenomenology that the Minkowski space-time could be unstable against vacuum fluctuations. 相似文献
343.
Frabetti PL Cheung HW Cumalat JP Dallapiccola C Ginkel JF Greene SV Johns WE Nehring MS Butler JN Cihangir S Gaines I Garbincius PH Garren L Gourlay SA Harding DJ Kasper P Kreymer A Lebrun P Shukla S Vittone M Bianco S Fabbri FL Sarwar S Zallo A Culbertson R Gardner RW Greene R Wiss J Alimonti G Bellini G Caccianiga B Cinquini L Di Corato M Giammarchi M Inzani P Leveraro F Malvezzi S Menasce D Meroni E Moroni L Pedrini D Perasso L Sala A Sala S Torretta D Buchholz D Claes D Gobbi B O'Reilly B 《Physical review letters》1994,72(3):324-327
344.
Naples D Akchurin N Birmingham P Breuer H Chang CC Cihangir S Corcoran MD Davis WL Gustafson HR Holmgren H Kasper P Lincoln D Longo MJ Marraffino J McPherson J Miettinen HE Morrow G Mutchler GS Onel Y Thomas GP Traynor MM Waters JW Webster MS Xu JP Zhu Q 《Physical review letters》1994,72(15):2341-2344
345.
K. E. Shestermanov A. N. Vasiliev J. Butler A. A. Derevshchikov P. Kasper V. V. Kiselev V. I. Kravtsov Y. Kubota R. Kutschke Yu. A. Matulenko N. G. Minaev V. V. Mochalov D. A. Morozov L. V. Nogach M. Rovere A. V. Ryazantsev P. A. Semenov S. Stone A. V. Uzunian J. Yarba 《Physics of Atomic Nuclei》2007,70(6):1058-1073
A precise measurement of the angle α in the CKM triangle is very important for a complete test of the Standard Model. A theoretically clean method to extract
α is provided by B
0 → ρπ decays. Monte Carlo simulations to obtain the BTeV reconstruction efficiency and to estimate the signal-to-background ratio
for these decays were performed. Finally the time-dependent Dalitz plot analysis, using the isospin amplitude formalism for
tree and penguin contributions, was carried out. It was shown that, in one year of data taking, BTeV could achieve an accuracy
on α better than 5°.
The text was submitted by the authors in English 相似文献
346.
We propose an experimentally viable setup for the realization of one-dimensional ultracold atom gases in a nanoscale magnetic
waveguide formed by single doubly-clamped suspended carbon nanotubes. We show that all common decoherence and atom loss mechanisms
are small, guaranteeing a stable operation of the trap. Since the extremely large current densities in carbon nanotubes are
spatially homogeneous, our proposed architecture allows for creation of a very regular trapping potential for the atom cloud.
Adding a second nanowire allows creation of a double-well potential with a moderate tunneling barrier which is desired for
tunneling and interference experiments with the advantage of tunneling distances being in the nanometer regime.
PACS 03.75.Gg; 03.75.Dg; 73.63.Fg 相似文献
347.
C. Hofer C. Teichert M. Oehme J. Werner K. Lyutovich E. Kasper 《Applied Surface Science》2009,256(1):267-273
Ion assisted molecular beam epitaxy bears the potential to tune morphological and structural parameters of semiconductor heterolayers for opto- and nanoelectronic applications. The morphology evolution and the degree of relaxation are influenced by the ion beam parameters and the strain of the heteroepitaxial film. In this work, the morphology of silicon germanium (SiGe) layers due to Si+-ion beam treatment during growth is investigated by atomic force microscopy (AFM) as a function of ion energy and ion flux density. Ion energies range from 100 eV to 1000 eV. The AFM measurements are used to determine the roughness distribution across the wafers. A regular pattern of SiGe crystallites is found, where the damage due to low ion energy Si+-ion bombardment is medium and the degree of relaxation, determined by Raman spectroscopy, is below 25%. 相似文献
348.
D. D. Khalyavin I. O. Troyanchuk N. V. Kasper H. Szymczak 《Journal of Experimental and Theoretical Physics》2001,93(4):805-808
Slowly cooled Nd1 ? x BaxCoO3 ? δ samples were two-phase in the concentration interval 0.3 ≤ x ≤ 0.46. One of the phases had O-orthorhombic lattice distortions (Pbnm) characteristic of ferromagnetic samples with x ≤ 0.3, and the other phase had tetragonal distortions (P4/mmm) characteristic of samples with x ≥ 0.46. Tetragonal distortions were caused by ordering of Nd3+ and Ba2+ ions. Samples with ordered neodymium and barium ions (Nd1 ? y Ba1 + y Co2O6 ? γ at ?0.08 ≤ y ≤ 0.08) experienced metal-dielectric and orientation magnetic phase transitions. 相似文献
349.
Heilemann M Kasper R Tinnefeld P Sauer M 《Journal of the American Chemical Society》2006,128(51):16864-16875
Molecular photonic wires are one-dimensional representatives of a family of nanoscale molecular devices that transport excited-state energy over considerable distances in analogy to optical waveguides in the far-field. In particular, the design and synthesis of such complex supramolecular devices is challenging concerning the desired homogeneity of energy transport. On the other hand, novel optical techniques are available that permit direct investigation of heterogeneity by studying one device at a time. In this article, we describe our efforts to synthesize and study DNA-based molecular photonic wires that carry several chromophores arranged in an energetic downhill cascade and exploit fluorescence resonance energy transfer to convey excited-state energy. The focus of this work is to understand and control the heterogeneity of such complex systems, applying single-molecule fluorescence spectroscopy (SMFS) to dissect the different sources of heterogeneity, i.e., chemical heterogeneity and inhomogeneous broadening induced by the nanoenvironment. We demonstrate that the homogeneity of excited-state energy transport in DNA-based photonic wires is dramatically improved by immobilizing photonic wires in aqueous solution without perturbation by the surface. In addition, our study shows that the in situ construction of wire molecules, i.e., the stepwise hybridization of differently labeled oligonucleotides on glass cover slides, further decreases the observed heterogeneity in overall energy-transfer efficiency. The developed strategy enables efficient energy transfer between up to five chromophores in the majority of molecules investigated along a distance of approximately 14 nm. Finally, we used multiparameter SMFS to analyze the energy flow in photonic wires in more detail and to assign residual heterogeneity under optimized conditions in solution to different leakages and competing energy-transfer processes. 相似文献
350.