Isospectrality and Operator Complexity
等谱性与算子复杂性
Pradip Kattel, Yicheng Tang, Natan Andrei
AI总结 研究一对精确可解的等谱费米子链(一个强相互作用,一个二次型),通过非局域非线性幺正变换揭示其截然不同的相结构和算子动力学,证明自由多体谱与相互作用算子动力学在根本上是兼容的。
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我们研究一对精确可解的等谱费米子链,一个强相互作用,一个二次型,然而它们表现出显著不同的相结构和算子动力学。一个非局域非线性幺正变换将一个映射到另一个,同时保持整个多体谱不变,并将局域费米子算子转换为扩展的多体弦。因此,在二次模型中在线性闭子空间内演化的算子,在相互作用模型中成为产生越来越高的体项并表现出渐近Lanczos增长$b_n\propto\sqrt n$的相互作用算子。尽管谱相同,这两个模型实现了不同的相和截然不同的算子复杂性概念。我们的结果表明,自由多体谱和相互作用算子动力学在根本上是兼容的。
We study a pair of exactly solvable, isospectral fermion chains, one strongly interacting and one quadratic, that nevertheless display remarkably different phase structures and operator dynamics. A nonlocal nonlinear unitary transformation maps one onto the other while preserving the entire many-body spectrum and converting local fermion operators into extended many-body strings. Thus, operators that evolve within a closed linear subspace in the quadratic model become interacting operators that generate increasingly higher-body terms and exhibit asymptotic Lanczos growth $b_n\propto\sqrt n$. Despite their identical spectra, the two models realize distinct phases and sharply different notions of operator complexity. Our results demonstrate that free many-body spectra and interacting operator dynamics are fundamentally compatible.