scholarly journals Nonadiabatic nonlinear optics and quantum geometry — Application to the twisted Schwinger effect

2021 ◽  
Vol 11 (4) ◽  
Author(s):  
Shintaro Takayoshi ◽  
Jianda Wu ◽  
Takashi Oka
Keyword(s):  
Electric Fields ◽  
Quantum Geometry ◽  
Rectification Effect ◽  
Zener Model ◽  
Tunneling Mechanism ◽  
Valley Polarization ◽  
Schwinger Effect ◽  
Geometric Effects ◽  
Weyl Fermions ◽  
Sweep Speed

We study the tunneling mechanism of nonlinear optical processes in solids induced by strong coherent laser fields. The theory is based on an extension of the Landau-Zener model with nonadiabatic geometric effects. In addition to the rectification effect known previously, we find two effects, namely perfect tunneling and counterdiabaticity at fast sweep speed. We apply this theory to the twisted Schwinger effect, i.e., nonadiabatic pair production of particles by rotating electric fields, and find a nonperturbative generation mechanism of the opto-valley polarization and photo-current in Dirac and Weyl fermions.

Schwinger effect of Gaussian correlations in constant electric fields

2020 ◽  
Vol 37 (11) ◽  
pp. 115003
Author(s):  
Shu-Min Wu ◽  
Hao-Sheng Zeng
Keyword(s):  
Electric Fields ◽  
Schwinger Effect

scholarly journals Is classical flat Kasner spacetime flat in quantum gravity?

2016 ◽  
Vol 25 (08) ◽  
pp. 1642001 ◽  
Author(s):  
Parampreet Singh
Keyword(s):  
Quantum Gravity ◽  
Minkowski Spacetime ◽  
Quantum Geometry ◽  
Classical Level ◽  
Bianchi I ◽  
Spacetime Curvature ◽  
Loop Quantization ◽  
Universal Bounds ◽  
Vacuum Spacetime ◽  
Geometric Effects

Quantum nature of classical flat Kasner spacetime is studied using effective spacetime description in loop quantum cosmology (LQC). We find that even though the spacetime curvature vanishes at the classical level, nontrivial quantum gravitational effects can arise. For the standard loop quantization of Bianchi-I spacetime, which uniquely yields universal bounds on expansion and shear scalars and results in a generic resolution of strong singularities, we find that a flat Kasner metric is not a physical solution of the effective spacetime description, except in a limit. The lack of a flat Kasner metric at the quantum level results from a novel feature of the loop quantum Bianchi-I spacetime: quantum geometry induces nonvanishing spacetime curvature components, making it not Ricci flat even when no matter is present. The noncurvature singularity of the classical flat Kasner spacetime is avoided, and the effective spacetime transits from a flat Kasner spacetime in asymptotic future, to a Minkowski spacetime in asymptotic past. Interestingly, for an alternate loop quantization which does not share some of the fine features of the standard quantization, flat Kasner spacetime with expected classical features exists. In this case, even with nontrivial quantum geometric effects, the spacetime curvature vanishes. These examples show that the character of even a flat classical vacuum spacetime can alter in a fundamental way in quantum gravity and is sensitive to the quantization procedure.

scholarly journals A holographic description of the Schwinger effect in a confining gauge theory

2015 ◽  
Vol 30 (11) ◽  
pp. 1530026 ◽  
Author(s):  
Daisuke Kawai ◽  
Yoshiki Sato ◽  
Kentaroh Yoshida
Keyword(s):  
Pair Production ◽  
Production Rate ◽  
Electric Fields ◽  
String Tension ◽  
Critical Value ◽  
Remarkable Feature ◽  
Coulomb Phase ◽  
Holographic Approach ◽  
Schwinger Effect ◽  
Holographic Description

This is a review of the recent progress on a holographic description of the Schwinger effect. In 2011, Semenoff and Zarembo proposed a scenario to study the Schwinger effect in the context of the AdS/CFT correspondence. The production rate of quark–antiquark pairs was computed in the Coulomb phase. In particular, it provided the critical value of external electric field, above which particles are freely created and the vacuum decays catastrophically. Then the potential analysis in the holographic approach was invented and it enabled us to study the Schwinger effect in the confining phase as well. A remarkable feature of the Schwinger effect in the confining phase is to exhibit another kind of the critical value, below which the pair production cannot occur and the vacuum of the system is nonperturbatively stable. The critical value is tantamount to the confining string tension. We computed the pair production rate numerically and introduced new exponents associated with the critical electric fields.

Material Orientations and Geometric Effects in Piezoelectric Actuators

Aerospace ◽  
2006 ◽  
Author(s):  
Stephanie A. Wimmer ◽  
Virginia G. DeGiorgi
Keyword(s):  
Electric Fields ◽  
Complex Geometry ◽  
Computational Study ◽  
Piezoelectric Materials ◽  
Complex Loading ◽  
Piezoelectric Actuators ◽  
Tensile Specimen ◽  
Active Materials ◽  
Element Analysis ◽  
Geometric Effects

Piezoelectric materials are active materials that deform in response to both electrical and mechanical loadings. Traditional piezoelectric actuators are designed to exploit this deformation by aligning the material poling axes with the loading axes. However for complex loading or complex geometry this alignment may not maximize the desired actuation due to the anisotropic piezoelectric and elastic properties. A computational study of material and loading axes misalignment was completed to examine the performance of piezoelectric components. The study used finite element analysis to model difference geometries; a simple cylinder, an ASTM E8 tensile specimen, and a customized ASTM E8 tensile specimen. This study looked at electrical only and mechanical only loading. The material axes for each component is rotated from being aligned with the loading axes to various angles. The effect of rotating the material axes is discussed. Variations in stress, electric fields and deformations are noted.

scholarly journals Influence of backreaction of electric fields and Schwinger effect on inflationary magnetogenesis

2018 ◽  
Vol 98 (6) ◽  
Author(s):  
O. O. Sobol ◽  
E. V. Gorbar ◽  
M. Kamarpour ◽  
S. I. Vilchinskii
Keyword(s):  
Electric Fields ◽  
Schwinger Effect

Control of Metal Alloy Oxidation with Electric Fields

1973 ◽  
Vol 31 ◽  
pp. 164-165
Author(s):  
R. R. Dils ◽  
P. S. Follansbee
Keyword(s):  
Electric Fields ◽  
Oxidation Process ◽  
Base Alloy ◽  
Oxide Surface ◽  
Platinum Electrodes ◽  
Insulating Layer ◽  
Iron Base Alloy ◽  
Alloy Oxidation ◽  
Aluminum Oxide Layer ◽  
And Control

Electric fields have been applied across oxides growing on a high temperature alloy and control of the oxidation of the material has been demonstrated. At present, three-fold increases in the oxidation rate have been measured in accelerating fields and the oxidation process has been completely stopped in a retarding field.The experiments have been conducted with an iron-base alloy, Pe 25Cr 5A1 0.1Y, although, in principle, any alloy capable of forming an adherent aluminum oxide layer during oxidation can be used. A specimen is polished and oxidized to produce a thin, uniform insulating layer on one surface. Three platinum electrodes are sputtered on the oxide surface and the specimen is reoxidized.

Electron-Mirror Microscopic Aspects of Ferroelectric Domains of BaTiO3 And Ca2Sr (C2H5CO2)6

1970 ◽  
Vol 28 ◽  
pp. 478-479
Author(s):  
Teruo Someya ◽  
Jinzo Kobayashi
Keyword(s):  
Surface Layer ◽  
Electric Fields ◽  
Quantitative Study ◽  
Recent Progress ◽  
Ferroelectric Domain ◽  
Resolving Power ◽  
Surface Pattern ◽  
Crystal Surfaces ◽  
One Dimensional ◽  
Ferroelectric Domains

Recent progress in the electron-mirror microscopy (EMM), e.g., an improvement of its resolving power together with an increase of the magnification makes it useful for investigating the ferroelectric domain physics. English has recently observed the domain texture in the surface layer of BaTiO3. The present authors ) have developed a theory by which one can evaluate small one-dimensional electric fields and/or topographic step heights in the crystal surfaces from their EMM pictures. This theory was applied to a quantitative study of the surface pattern of BaTiO3).

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