辐射退相干、态矢坍缩和QED非等价表示
Radiation Decohernce, State Vector Collapse and QED Nonequivalent Representations
摘要：
用非微扰QED方法分析了初始测量纯态与集体量子系统或自由度N很大的光场相互作用中态矢量的演化。作为例子，考虑了散射在原子核或中微子上的电子末态的测量，在非微扰场论中，系统态的完备流形是不可分的，即用无穷多个独立Hilbert空间的张量积来描述。该系统与被测态的相互作用可以导致最终态属于不同的Hilbert空间，对应于不同的经典观测量值，即发生自发对称性破缺。在任何厄米可观测量的测量中，这种状态之间的干扰项（IT）是无限小的，因此最终的纯态无法与混合态区分开来，这是状态崩溃的特征。系统从初始态到最终态的演化是非幺正的，在无限时间的极限下成为形式上不可逆的。在电子散射过程中产生的电磁韧致辐射中含有数量不受限制的软光子，其辐射通量成为经典可观测的。本文简要地讨论了在铁磁和声子激发的第二类相变中出现的类似过程。
英文摘要：
The state vector evolution in the interaction of initial measured pure state with collective quantum system or the field with a very large number of degrees of freedom N is analysed in a nonperturbative QED formalism. As the example the measurement of the electron final state scattered on nucleus or neutrino is considered.In the nonperturbative field theory the complete manifold of the system states is nonseparable i.e. is described by tensor product of infinitely many independent Hilbert spaces. The interaction of this system with the measured state can result in the final states which belong to different Hilbert spaces which corresponds to different values of some classical observables,i.e. spontaneous symmetry breaking occurs. Interference terms (IT) between such states in the measurement of any Hermitian observable are infinitely small and due to it the final pure states can't be distinguished from the mixed ones, characteristic for the state collapse. The evolution from initial to final system state is nonunitary and become formally irreversible in the limit of infinite time. The electromagnetic (e-m) bremmstrahlung produced in the electron scattering process contain the unrestricted number of soft photons which radiation flux become classic observable. Analoguous processes which occurs in the second kind phase transitions in ferromagnetic and phonon excitations in cristall lattice are considered briefly.
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