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Mario Castagnino Susana Landau Fernando C. Lombardo 《General Relativity and Gravitation》1999,31(9):1407-1422
We consider a simple cosmological model in orderto show the importance of unstable particle creation forthe validity of the semiclassical approximation. Usingthe mathematical structure of rigged Hilbert spaces we show that particle creation is theseed of decoherence which enables the quantum toclassical transition. 相似文献
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Intermittent shear flow including start-up flow and small oscillatory amplitude time sweep or stress relaxation after cessation of shear flow was used to study the rheological behavior and internal structure of thermotropic liquid crystalline polymer (TLCP). There are two kinds of intermittent shear flow: all start-up flows are in the same direction (intermittent flow forward: IFF) and start-up flows change their directions alternately (intermittent flow reversal: IFR). The results show that the stress of start-up flow of IFF and IFR in the test process is not superposed, indicating different changes of internal structure of thermotropic LCP (TLCP). Two main factors affect structure changes in the experimental time scale. One relates to long-term texture relaxation process, the other is an interchain reaction that becomes important after 30 min. The two factors raise the stress of IFF, but express complex effects for the stress of IFR. The latter factor becomes very important at long time annealing process. The relaxation behavior was also studied by the application of wide range relaxation spectrum calculated from the combined dynamic modulus, which gave three characteristic relaxation times (0.3, 10 and 600 s) ascribable to the relaxations of less-phase orientation, domain orientation, and domain deformation, respectively. The result also shows that the domain coalescence (texture relaxation), a long relaxation time, is a much slow process and lasts beyond 2400 s of the test time. 相似文献
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对O(~3P+C_2F_4反应动力学的详细研究始于1976年.交叉分子束实验和流动余辉实验相继测得该反应的分支比,角分布和速度分布及内态分布.Bogan用相空间理论对该反应进行了近似计算.本文则由前文的结果,通过机制分析得到CF_2(~3B_1)的初生弯曲振动态相对布居和C_2F_4对CF_2(~3B_1)的弯曲振动弛豫常数,并对该结果进行了分析和讨论. 初生内能态分布和振动弛豫常数的计算前文结果如表1所示.其中C_2F_4的分气压由测得的总气压随C_2F_4流量的变化而推得,表中同时给出了态分布的拟合值. 产生观察到的内能态布居的过程可概括如下: 相似文献