The term ＇assortative mating＇ has been applied to describe two very different phenomena： （1） the tendency for indi- viduals to choose phenotypically similar mates from among conspecifics; or （2） the tendency to...The term ＇assortative mating＇ has been applied to describe two very different phenomena： （1） the tendency for indi- viduals to choose phenotypically similar mates from among conspecifics; or （2） the tendency to prefer conspecific over hete- rospecific mates （behavioral reproductive isolation）. Both forms of assortative mating are widespread in nature, but the relation- ship between these behaviors remains unclear. Namely, it is plausible that a preference for phenotypically similar conspecifics in cidentally reduces the probability of mating with phenotypically divergent heterospecifics. We present a model to calculate how the level of reproductive isolation depends on intraspecific assortative mating and the phenotypic divergence between species. For empirically reasonable levels of intraspecific assortment on a single trait axis, we show that strong reproductive isolation requires very substantial phenotypic divergence. We illustrate this point by applying our model to empirical data from threespine stickleback Gasterosteus aculeatus and Darwin＇s Finches （Geospiza spp）. We conclude that typical levels of intraspecific assortment cannot generally be extrapolated to explain levels of interspecific reproductive isolation. Instead, reproductive isolation between species likely arises from different mate choice behaviors, or multivariate assortative mating [Current Zoology 58 （3）： 484-492, 2012].展开更多
Corresponding to optical Fresnel diffraction, we show that the exponential quadratic operator exp is actually a generalized single-mode Fresnel operator （GFO） in compact form, where [Q,P]=ih. We also demonstrate tha...Corresponding to optical Fresnel diffraction, we show that the exponential quadratic operator exp is actually a generalized single-mode Fresnel operator （GFO） in compact form, where [Q,P]=ih. We also demonstrate that exp{iα[（Q1＋Q2）2＋（p1-P2）2]＋iβ[（Q1-Q2）2＋（p1＋p2）2]＋iy（Q1P2＋Q2P1）} is a two-mode GFO. Their disentangling formula and normal ordering form are derived with the use of technique of integration within an ordered product （IWOP） of operators and the coherent state representation. The squeezed states generated by these two GFOs are obtained.展开更多
The emission spectrum of a two-level atom interacting with a single mode radiation field in the case of periodic oscillation coupling coefficient is investigated.A general expression for the emission spectrum is deriv...The emission spectrum of a two-level atom interacting with a single mode radiation field in the case of periodic oscillation coupling coefficient is investigated.A general expression for the emission spectrum is derived.The numerical results for the initial field in pure number stare are calculated.It is found that the effect of the coupling coefficient modulation on the spectral structure is very obvious in the case of a low modulation frequency and larger amplitude when the initial field is vacuum,which is potentially useful for exploring a modulated light source.展开更多
文摘The term ＇assortative mating＇ has been applied to describe two very different phenomena： （1） the tendency for indi- viduals to choose phenotypically similar mates from among conspecifics; or （2） the tendency to prefer conspecific over hete- rospecific mates （behavioral reproductive isolation）. Both forms of assortative mating are widespread in nature, but the relation- ship between these behaviors remains unclear. Namely, it is plausible that a preference for phenotypically similar conspecifics in cidentally reduces the probability of mating with phenotypically divergent heterospecifics. We present a model to calculate how the level of reproductive isolation depends on intraspecific assortative mating and the phenotypic divergence between species. For empirically reasonable levels of intraspecific assortment on a single trait axis, we show that strong reproductive isolation requires very substantial phenotypic divergence. We illustrate this point by applying our model to empirical data from threespine stickleback Gasterosteus aculeatus and Darwin＇s Finches （Geospiza spp）. We conclude that typical levels of intraspecific assortment cannot generally be extrapolated to explain levels of interspecific reproductive isolation. Instead, reproductive isolation between species likely arises from different mate choice behaviors, or multivariate assortative mating [Current Zoology 58 （3）： 484-492, 2012].
基金supported by the Natural Science Foundation of Shandong Province of China (Grant No. Y2008A16)the Specialized Research Fund for the Doctoral Program of Higher Education China (Grant No.20103705110001)
文摘Corresponding to optical Fresnel diffraction, we show that the exponential quadratic operator exp is actually a generalized single-mode Fresnel operator （GFO） in compact form, where [Q,P]=ih. We also demonstrate that exp{iα[（Q1＋Q2）2＋（p1-P2）2]＋iβ[（Q1-Q2）2＋（p1＋p2）2]＋iy（Q1P2＋Q2P1）} is a two-mode GFO. Their disentangling formula and normal ordering form are derived with the use of technique of integration within an ordered product （IWOP） of operators and the coherent state representation. The squeezed states generated by these two GFOs are obtained.
基金Supported by the Shandong Province Natural Science Foundation under Grant No.ZR2009AM019
文摘The emission spectrum of a two-level atom interacting with a single mode radiation field in the case of periodic oscillation coupling coefficient is investigated.A general expression for the emission spectrum is derived.The numerical results for the initial field in pure number stare are calculated.It is found that the effect of the coupling coefficient modulation on the spectral structure is very obvious in the case of a low modulation frequency and larger amplitude when the initial field is vacuum,which is potentially useful for exploring a modulated light source.
