The one - loop vacuum polarization is calculated for untwisted and twisted scalar fields in a flat space - time with the topology s1 r3 . the effect of vacuum polarization upon photon propagation is considered . it is found that for the untwisted scalar field some photon modes acquire a positive topological mass , thus travelling at a subluminal speed ; but for the twisted scalar field some photon modes get an imaginary topological mass and travel at a superluminal speed 本文中我们首先计算了在拓扑结构为s ~ 1 r ~ 3的非minkowski时空中扭曲标量场和非扭曲标量场的真空极化，然后考虑了真空极化对光子传播的影响，我们发现除了光子的极化方向和传播方向都垂直于紧致化方向的情形之外，非扭曲标量场的真空极化使所有其他的光子模式都获得实的拓扑质量从而导致这些光子以亚光速传播；但是，扭曲标量场的真空极化使光子获得虚的拓扑质量以致他们以超光速传播。
In chapter 3 , we studied the effect of gaussian transverse profile for the driving and laser fields on lasing without population inversion ( lwi ) in a closed v - type system and an open v - type system . moreover , we discussed also the effect of the unsaturated gain coefficient , the cavity - damping rate , the ratio of the atomic injection rates and atomic exit rate on the corresponding systems . in chapter 4 , we mainly discussed the effect of doppler broadening on the gain , dispersion and the frequency up - conversion of the open v - type lwi system and compared the differences and the same between the open system and the corresponding closed system 发现： ( 1 )在考虑doppler展宽的情况下，通过选取合适的实验室条件(比如合适的原子环境温度等)可得到合适doppler展宽值，从而使系统获得最佳增益； ( 2 )要想实现系统的频率上转换，同时又要获得足够强的无反转激光增益，则系统频率转换比不能选取的太大； ( 3 )对于开放系统，比较小的粒子注入速率比与退出速率对产生无反转激光是有利硕士学位论文摘要的： （ 4 ）由于dopp1oy展宽的存在，当探测场与驱动场的传播方向相反时，增益在探测场失谐的某一段区域产生振荡，且振荡的振幅、频率失谐范围的大小与dopper展宽的取值有关。
The green ' s function for point - source excitation is also very simple in homogeneous media . however , since global basic functions like plane waves occupy the entire domain and point source excitation radiates to all directions , their evolution through a non - homogeneous medium constitutes a problem that may become at least as difficult to solve as that of the propagation of the total field 例如dirac函数(点源)在空间域可以有精确的定位，但在传播方向上(波数域)却毫无确定性；而平面波(波数域的基本解)则具有精确的传播方向，但其波前却是无限延伸的，不具任何空间局域性。
As barium titanium is a typical ferroelectrics medium , in which the variation of the polarization intensity with the field strength is nonlinear under the external electric field . the behavior of microwave propagation in batio3 er fluids was also studied when considering the microwave propagation in a direction perpendicular and parallel to the particle chains , respectively . the microwave transmittance in the fluids could be adjusted by the electric field 考虑到batio _ 3是一种非线性介质，在外电场作用下自身介电行为变化的特殊性，对batio _ 3电流变液微波透射行为进行了研究，分别考虑微波传播方向与电流变液颗粒链相垂直和平行的情况，发现batio _ 3电流变液微波透射率亦可由外电场调控。
