Analytic and numerical study of preheating dynamics

Chiral Instabilities and the Onset of Chiral Turbulence in QED Plasmas

We present a first principles study of chiral plasma instabilities and the onset of chiral turbulence in QED plasmas with strong gauge matter interaction (e^{2}N_{f}=64), far from equilibrium. By performing classical-statistical lattice simulations of the microscopic theory, we show that the generation of strong helical magnetic fields from a helicity imbalance in the fermion sector proceeds via three distinct phases. During the initial linear instability regime the helicity imbalance of the fermion sector causes an exponential growth (damping) of magnetic field modes with right- (left-) handed polarization, for which we extract the characteristic growth (damping) rates. Secondary growth of unstable modes accelerates the helicity transfer from fermions to gauge fields and ultimately leads to the emergence of a self-similar scaling regime characteristic of a decaying turbulence, where magnetic helicity is efficiently transferred to macroscopic length scales. Within this turbulent regime, the evolution of magnetic helicity spectrum can be described by an infrared power spectrum with spectral exponent κ=10.2±0.5 and dynamical scaling exponents α=1.14±0.50 and β=0.37±0.13.

Floquet prethermalization and regimes of heating in a periodically driven, interacting quantum system

We study the regimes of heating in the periodically driven O(N)-model, which is a well established model for interacting quantum many-body systems. By computing the absorbed energy with a non-equilibrium Keldysh Green's function approach, we establish three dynamical regimes: at short times a single-particle dominated regime, at intermediate times a stable Floquet prethermal regime in which the system ceases to absorb, and at parametrically late times a thermalizing regime. Our simulations suggest that in the thermalizing regime the absorbed energy grows algebraically in time with an exponent that approaches the universal value of 1/2, and is thus significantly slower than linear Joule heating. Our results demonstrate the parametric stability of prethermal states in a many-body system driven at frequencies that are comparable to its microscopic scales. This paves the way for realizing exotic quantum phases, such as time crystals or interacting topological phases, in the prethermal regime of interacting Floquet systems.

Propofol sedation versus no sedation in detection of pharyngeal and upper gastrointestinal superficial squamous cell carcinoma using endoscopic narrow band imaging: a multicenter prospective trial

Intravenous propofol can provide a superior quality of sedation compared to standard sedation for upper gastrointestinal endoscopy. However, the utility of propofol sedation for the endoscopic early detection of superficial pharyngeal and esophageal squamous cell carcinoma has not been investigated. In a multicenter, prospective trial, 255 patients with esophageal squamous cell carcinomas (ESCCs) were assigned to receive propofol sedation or no sedation according to their own willingness. The primary aim was to compare the detection rates of superficial cancer in the pharyngeal region and the esophagus between two groups. The secondary aim was to evaluate factors associated with technical adequacy. The detection rate was higher in the propofol sedation vs. no sedation group for H&N region (6.06% vs. 2.40%), but not significantly (P=0.22). However, the small lesion (less than 10 mm in diameter) detection rate was higher in sedation vs. no sedation group for H&N region (88.89% vs. 33.33%; P=0.048). The median time for pharyngeal observation in the sedation group was faster than in the no sedation group (20.6 s vs. 44.3 s; P<0.001). Ninety-five percent of H&N region evaluations were totally complete in sedation compared with sixty percent in the no sedation group (P<0.001). The overall p value indicated that only smoking habit was associated with incomplete pharyngeal observation (P<0.05), and it was more difficult to accomplish a complete pharyngeal observation in patients who smoked more than 10 packs per day. Intravenous propofol sedation compared to no intravenous sedation during conventional upper gastrointestinal endoscopy can facilitate a more complete pharyngeal examination and increase the detection rate of superficial H&N squamous cell carcinoma in high risk patients.

Lamé polynomials, hyperelliptic reductions and Lamé band structure

The band structure of the Lamé equation, viewed as a one-dimensional Schrödinger equation with a periodic potential, is studied. At integer values of the degree parameter l, the dispersion relation is reduced to the l=1 dispersion relation, and a previously published l=2 dispersion relation is shown to be partly incorrect. The Hermite-Krichever Ansatz, which expresses Lamé equation solutions in terms of l=1 solutions, is the chief tool. It is based on a projection from a genus-l hyperelliptic curve, which parametrizes solutions, to an elliptic curve. A general formula for this covering is derived, and is used to reduce certain hyperelliptic integrals to elliptic ones. Degeneracies between band edges, which can occur if the Lamé equation parameters take complex values, are investigated. If the Lamé equation is viewed as a differential equation on an elliptic curve, a formula is conjectured for the number of points in elliptic moduli space (elliptic curve parameter space) at which degeneracies occur. Tables of spectral polynomials and Lamé polynomials, i.e. band-edge solutions, are given. A table in the earlier literature is corrected.

Parametric resonance in quantum field theory

We present the first study of parametric resonance in quantum field theory from a complete next-to-leading order calculation in a 1/N expansion of the two-particle irreducible effective action, which includes scattering and memory effects. We present a complete numerical solution for an O(N)-symmetric scalar theory and provide an approximate analytic description of the nonlinear dynamics in the entire amplification range. We find that the classical resonant amplification at early times is followed by a collective amplification regime with explosive particle production in a broad momentum range, which is not accessible in a leading-order calculation.

Dissipation, noise, and vacuum decay in quantum field theory

We study the process of vacuum decay in quantum field theory focusing on the stochastic aspects of the interaction between long- and short-wavelength modes. This interaction results in a diffusive behavior of the reduced Wigner function describing the state of long-wavelength modes, and thereby to a finite activation rate even at zero temperature. This effect can make a substantial contribution to the total decay rate.

Resonant production of topological defects

We describe a novel phenomenon in which vortices are produced due to resonant oscillations of a scalar field which is driven by a periodically varying temperature T, with T remaining much below the critical temperature T(c). Also, in a rapid heating of a localized region to a temperature below T(c), far separated vortex and antivortex can form. We compare our results with recent models of defect production during reheating after inflation. We also discuss possible experimental tests of our predictions of topological defect production without ever going through a phase transition.