Wisniacki D A, Roncaglia A J
Departamento de Física, FCEyN, UBA and IFIBA, CONICET, Pabellón 1, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
Phys Rev E Stat Nonlin Soft Matter Phys. 2013 May;87(5):050902. doi: 10.1103/PhysRevE.87.050902. Epub 2013 May 17.
The local density of states or its Fourier transform, usually called fidelity amplitude, are important measures of quantum irreversibility due to imperfect evolution. In this Rapid Communication we study both quantities in a paradigmatic many body system, the Dicke Hamiltonian, where a single-mode bosonic field interacts with an ensemble of N two-level atoms. This model exhibits a quantum phase transition in the thermodynamic limit, while for finite instances the system undergoes a transition from quasi-integrability to quantum chaotic. We show that the width of the local density of states clearly points out the imprints of the transition from integrability to chaos but no trace remains of the quantum phase transition. The connection with the decay of the fidelity amplitude is also established.
态密度的局部值或其傅里叶变换，通常称为保真度振幅，是由于不完美演化导致的量子不可逆性的重要度量。在本快报中，我们在一个典型的多体系统——迪克哈密顿量中研究这两个量，其中单模玻色场与N个两能级原子的系综相互作用。该模型在热力学极限下呈现量子相变，而对于有限的情况，系统经历从准可积性到量子混沌的转变。我们表明，态密度的局部值的宽度清楚地指出了从可积性到混沌转变的印记，但量子相变没有留下任何痕迹。还建立了与保真度振幅衰减的联系。
