Quench dynamics of one-dimensional interacting bosons in a disordered potential: Elastic dephasing and critical speeding-up of thermalization

The dynamics of interacting bosons in one dimension following the sudden switching on of a weak disordered potential is investigated. On time scales before quasiparticles scatter (prethermalized regime), the dephasing from random elastic forward scattering causes all correlations to decay exponentially fast, but the system remains far from thermal equilibrium. For longer times, the combined effect of disorder and interactions gives rise to inelastic scattering and to thermalization. A novel quantum kinetic equation accounting for both disorder and interactions is employed to study the dynamics. Thermalization turns out to be most effective close to the superfluid-Bose glass critical point where nonlinearities become more and more important. The numerically obtained thermalization times are found to agree well with analytic estimates.Comment: 10 pages, 3 figures, published versio

Suitable Electrode Choice for Robotic-Assisted Cochlear Implant Surgery: A Systematic Literature Review of Manual Electrode Insertion Adverse Events

BACKGROUND AND OBJECTIVE: The cochlear implant (CI) electrode insertion process is a key step in CI surgery. One of the aims of advances in robotic-assisted CI surgery (RACIS) is to realize better cochlear structure preservation and to precisely control insertion. The aim of this literature review is to gain insight into electrode selection for RACIS by acquiring a thorough knowledge of electrode insertion and related complications from classic CI surgery involving a manual electrode insertion process. METHODS: A systematic electronic search of the literature was carried out using PubMed, Scopus, Cochrane, and Web of Science to find relevant literature on electrode tip fold over (ETFO), electrode scalar deviation (ESD), and electrode migration (EM) from both pre-shaped and straight electrode types. RESULTS: A total of 82 studies that include 8,603 ears implanted with a CI, i.e., pre-shaped (4,869) and straight electrodes (3,734), were evaluated. The rate of ETFO (25 studies, 2,335 ears), ESD (39 studies, 3,073 ears), and EM (18 studies, 3,195 ears) was determined. An incidence rate (±95% CI) of 5.38% (4.4–6.6%) of ETFO, 28.6% (26.6–30.6%) of ESD, and 0.53% (0.2–1.1%) of EM is associated with pre-shaped electrodes, whereas with straight electrodes it was 0.51% (0.1–1.3%), 11% (9.2–13.0%), and 3.2% (2.5–3.95%), respectively. The differences between the pre-shaped and straight electrode types are highly significant (p < 0.001). Laboratory experiments show evidence that robotic insertions of electrodes are less traumatic than manual insertions. The influence of round window (RW) vs. cochleostomy (Coch) was not assessed. CONCLUSION: Considering the current electrode designs available and the reported incidence of insertion complications, the use of straight electrodes in RACIS and conventional CI surgery (and manual insertion) appears to be less traumatic to intracochlear structures compared with pre-shaped electrodes. However, EM of straight electrodes should be anticipated. RACIS has the potential to reduce these complications

Prethermalization, universal scaling at macroscopic short times, and thermalization following a quantum quench

The study of the quantum dynamics of many-particle systems has recently become the subject of intensive research, stimulated in part by enormous progress in experimental techniques, particularly the manipulation of ultracold atomic gases, which allow high tunability of artificial systems with decoherence and dissipation strongly suppressed. One of the simplest protocols for out of equilibrium dynamics is a quantum quench where the time-scale associated with an external variation is much smaller than the typical relaxation time of the system. Here we first study in detail the dynamics after a quantum quench in the one-dimensional sine-Gordon model in the phase where the boson spectrum remains gapless. We construct a Dyson equation to leading order in the cosine potential and show that the resulting quantum kinetic equation is atypical in that it involves multi-particle scattering processes. We also show that using an effective action, which generates the Dyson equation by a variational principle, the conserved stress-momentum tensor can be constructed. We solve the dynamics numerically by making a quasi-classical approximation that makes the quantum kinetic equation local in time while retaining the multi-particle nature of the scattering processes. At long times the system is found to thermalize, with a thermalization time that depends in a non-monotonic way on the amount of energy injected into the system by the quench. This non-monotonic behavior arises due to the competing effect of an increase of phase space for scattering on the one hand, and an enhancement of the orthogonality catastrophe on the other hand as the quench amplitude is increased. The approach to equilibrium is found to be purely exponential for large quench amplitudes but more complex for smaller ones. In the following chapter, the dynamics of interacting bosons in one dimension after a sudden switching on of a weak disordered potential is investigated. We find that on time scales before quasiparticles scatter, which correspond to the prethermalization regime, the dephasing from random elastic forward scattering causes the correlations to decay exponentially fast, while the system remains far from thermal equilibrium. For longer times however, the combined effect of disorder and interactions gives rise to inelastic scattering which eventually leads to thermalization. A novel quantum kinetic equation taking into account both disorder and interactions is employed to study the dynamics. It is found that thermalization becomes most effective close to the superfluid-Bose glass critical point where nonlinearities become increasingly important. The thermalization times obtained numerically are found to agree well with analytic estimates. In the last chapter we investigate the dynamics of a scalar field theory in spatial dimension d=4 after a quench close to a critical point, using renormalization-group methods. We show that after the system is quenched, but before eventually thermalizing due to dissipative effects, it approaches a different, thermal-like regime associated with a fixed-point describing a dynamical scaling behaviour. Within this regime the time dependence of the dynamical correlations is characterized by a novel short-time universal exponent

Short-time universal scaling in an isolated quantum system after a quench

Renormalization-group methods provide a viable approach for investigating the emergent collective behavior of classical and quantum statistical systems in both equilibrium and nonequilibrium conditions. Within this approach we investigate here the dynamics of an isolated quantum system represented by a scalar phi(4) theory after a global quench of the potential close to a dynamical critical point. We demonstrate that, within a prethermal regime, the time dependence of the relevant correlations is characterized by a short-time universal exponent, which we calculate at the lowest order in a dimensional expansion