Overlap distributions for quantum quenches in the anisotropic Heisenberg chain

The dynamics after a quantum quench is determined by the weights of the initial state in the eigenspectrum of the final Hamiltonian, i.e., by the distribution of overlaps in the energy spectrum. We present an analysis of such overlap distributions for quenches of the anisotropy parameter in the one-dimensional anisotropic spin-1/2 Heisenberg model (XXZ chain). We provide an overview of the form of the overlap distribution for quenches from various initial anisotropies to various final ones, using numerical exact diagonalization. We show that if the system is prepared in the antiferromagnetic N\'eel state (infinite anisotropy) and released into a non-interacting setup (zero anisotropy, XX point) only a small fraction of the final eigenstates gives contributions to the post-quench dynamics, and that these eigenstates have identical overlap magnitudes. We derive expressions for the overlaps, and present the selection rules that determine the final eigenstates having nonzero overlap. We use these results to derive concise expressions for time-dependent quantities (Loschmidt echo, longitudinal and transverse correlators) after the quench. We use perturbative analyses to understand the overlap distribution for quenches from infinite to small nonzero anisotropies, and for quenches from large to zero anisotropy.Comment: 23 pages, 8 figure

Phonon dressing of a facilitated one-dimensional Rydberg lattice gas

We study the dynamics of a one-dimensional Rydberg lattice gas under facilitation (anti-blockade) conditions which implements a so-called kinetically constrained spin system. Here an atom can only be excited to a Rydberg state when one of its neighbors is already excited. Once two or more atoms are simultaneously excited mechanical forces emerge, which couple the internal electronic dynamics of this many-body system to external vibrational degrees of freedom in the lattice. This electron-phonon coupling results in a so-called phonon dressing of many-body states which in turn impacts on the facilitation dynamics. In our theoretical study we focus on a scenario in which all energy scales are sufficiently separated such that a perturbative treatment of the coupling between electronic and vibrational states is possible. This allows to analytically derive an effective Hamiltonian for the evolution of consecutive clusters of Rydberg excitations in the presence of phonon dressing. We analyze the spectrum of this Hamiltonian and show -- by employing Fano resonance theory -- that the interaction between Rydberg excitations and lattice vibrations leads to the emergence of slowly decaying bound states that inhibit fast relaxation of certain initial states.Comment: 26 pages, 5 figure

Could time detect a faking-good attitude? A study with the MMPI-2-RF

Background and Purpose: Research on the relationship between response latency (RL) and faking in self-administered testing scenarios have generated contradictory findings. We explored this relationship further, aiming to add further insight into the reliability of self-report measures. We compared RLs and T-scores on the MMPI-2-RF (validity and restructured clinical [RC] scales) in four experimental groups. Our hypotheses were that: the Fake-Good Speeded group would obtain a different completion time; show higher RLs than the Honesty Speeded Group in the validity scales; show higher T-Scores in the L-r and K-r scales and lower T-scores in the F-r and RC scales; and show higher levels of tension and fatigue. Finally, the impact of the speeded condition in malingering was assessed. Materials and Methods: The sample was comprised of 135 subjects (M = 26.64; SD = 1.88 years old), all of whom were graduates (having completed at least 17 years of instruction), male, and Caucasian. Subjects were randomly assigned to four groups: Honesty Speeded, Fake-Good Speeded, Honesty Un-Speeded, and Fake-Good Un-Speeded. A software version of the MMPI-2-RF and Visual Analog Scale (VAS) were administered. To test the hypotheses, MANOVAs and binomial logistic regressions were run. Results: Significant differences were found between the four groups, and particularly between the Honest and Fake-Good groups in terms of test completion time and the L-r and K-r scales. The speeded condition increased T-scores in the L-r and K-r scales but decreased T-scores in some of the RC scales. The Fake groups also scored higher on the VAS Tension subscale. Completion times for the first and second parts of the MMPI-2-RF and T-scores for the K-r scale seemed to predict malingering. Conclusion: The speeded condition seemed to bring out the malingerers. Limitations include the sample size and gender bias

Development of a multifunctional panel for aerospace use through SLM additive manufacturing

Lattice materials can overcome the need of light and stiff structures in the aerospace industry. The wing leading edge is one of the most critical parts for both on-board subsystem and structure features: it must withstand to the aerodynamic loads and bird-strike, integrating also the anti-ice system functions. Nowadays, this part is made by different components bonded together such as external skin, internal passageways, and feeding tubes. In the present work, a single-piece multifunctional panel made by additive manufacturing will be developed. Optimal design and manufacturing are discussed according to technological constraints, aeronautical performances and sustainability

Quantum Quench in one dimensional gases

In this work we discuss the relaxation properties of a quantum one dimensional gas. The interest in studying this kind of systems has recently grown due to the development of innovative experimental techniques that made possible the confinement of particles in quasi one-dimensional optical lattices weakly interacting with the environment. These properties can be explored using a quantum quench: we prepare the system in the ground state of a given hamiltonian, then we suddenly change a parameter and let it evolve unitarly. There are mainly two types of quantum quenches: local and global We consider a global quantum quench in a confined one dimensional bosonic gas. We show that relaxation occurs in slightly different manner than in the periodic case: the stationary correlation function "feels'' the boundaries also in the thermodynamic limit. Furthermore we find a compact expression for the time dependent density profile and for the fermionic correlation function. Both functions describe the non equilibrium behavior of the system. The solutions of the confined problem present difficulties which were absent in the periodic case. These have been overcome by some ingenious approximations which become exact in the thermodynamical limit, thus providing the analytical solution to the problem. In the course of the computation numerical analysis is often used as a support. We found out that the long-time state of the confined system is translationally invariant (we demonstrated that non translationally invariant corrections are finite-size effects), in particular the stationary density profile is the same as in the homogeneous case, as naively expected. But the effects of the confinement are visible both in the stationary two point correlation function and in the non trivial evolution of the density profile