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arXiv 1502.08006nlin.PS
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外驱动力作用下的非线性Dirac方程孤立波

Nonlinear Dirac equation solitary waves in the presence of external driving forces

Franz G. Mertens, Fred Cooper, Niurka R. Quintero, Sihong Shao, Avinash Khare, Avadh Saxena

摘要:

考虑一类具有阻尼和外力的1+1维非线性Dirac(NLD)方程$ f(x,t) - i μγ^0 Ψ$,其中$f$和$Ψ$都是二分量旋量.我们发展了一个近似的变分方法,使用集体坐标(CC)的孤立波的时间相关的响应,这些外力的研究。该方法预测了孤立波的固有振荡,即振幅、宽度和相位都以相同的频率振荡。平移运动也受到影响,因为孤立子的位置振荡周围的平均轨迹。然后,我们比较变分近似的结果与数值模拟的NLD方程,并找到一个很好的协议,如果我们考虑到一定的线性激发与特定的波数,激发与内在振荡,使动量在变换的NLD方程是保守的。我们还明确解决了CC方程的变分近似在非相对论制度的均匀外力,并获得良好的协议与CC方程的数值解。

英文摘要:

We consider the nonlinear Dirac (NLD) equation in 1+1 dimension with scalar-scalar self-interaction in the presence of external forces as well as damping of the form $ f(x,t) - i μγ^0 Ψ$, where both $f$ and $Ψ$ are two-component spinors. We develop an approximate variational approach using collective coordinates (CC) for studying the time dependent response of the solitary waves to these external forces. This approach predicts intrinsic oscillations of the solitary waves, i.e. the amplitude, width and phase all oscillate with the same frequency. The translational motion is also affected, because the soliton position oscillates around a mean trajectory. We then compare the results of the variational approximation with numerical simulations of the NLD equation, and find a good agreement, if we take into account a certain linear excitation with specific wavenumber that is excited together with the intrinsic oscillations such that the momentum in a transformed NLD equation is conserved. We also solve explicitly the CC equations of the variational approximation in the non-relativistic regime for a homogeneous external force and obtain excellent agreement with the numerical solution of the CC equations.

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