标题： 严格局域态在非相互作用量子场论中的演化 显示英文标题

标题： Evolution of strictly localized states in non-interacting quantum field theories with background fields

摘要： 我们研究了在计算量子场论（QFT）框架内构建具有紧支集的空间自旋-1/2费米子和自旋-0玻色子波包的问题，该框架提供了背景场中相对论波动方程的时空解。 为了构造完全局域化的波包，我们引入了一个空间密度算符，用于描述正负电荷粒子。 我们考察了该算符的真空态和单粒子期望值的性质，并将其与标准QFT中的粒子和反粒子空间密度进行了比较。 通过数值计算严格局域化波包的Klein隧道动力学，该波包撞击超临界静电阶梯，来说明这一形式主义。这里引入的密度算符可能有助于建模那些希望避免处理纯粒子或反粒子波包固有的无限空间尾部的情况。 显示英文摘要

摘要： We investigate the construction of spin-1/2 fermionic and spin-0 bosonic wave-packets having compact spatial support in the framework of a computational quantum field theory (QFT) scheme offering space-time solutions of the relativistic wave equations in background fields. In order to construct perfectly localized wave-packets, we introduce a spatial density operator accounting for particles of both positive and negative charge. We examine properties of the vacuum and single-particle expectation values of this operator and compare them to the standard QFT particle and anti-particle spatial densities. The formalism is illustrated by computing numerically the Klein tunneling dynamics of strictly localized wave-packets impinging on a supercritical electrostatic step. The density operator introduced here could be useful to model situations in which it is desirable to avoid dealing with the infinite spatial tails intrinsic to pure particle or anti-particle wave-packets.