March 29th, 2021

лошадь, диаграмма, Фейнман

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A Spacetime Finite Elements Method to Solve the Dirac Equation:
Rylee Sundermann, Hyun Lim, Jace Waybright, Jung-Han Kimn
In this work, a fully implicit numerical approach based on space-time finite element method is presented to solve the Dirac equation in 1 (space) + 1 (time), 2 + 1, and 3 + 1 dimensions. We utilize PETSc/Tao library to implement our linear system and for using Krylov subspace based solvers such as GMRES. We demonstrate our method by analyzing several different cases including plane wave solution, Zitterbewegung, and Klein paradox. Parallel performance of this implementation is also presented.
лошадь, диаграмма, Фейнман

Кошачьи усы в ламинарном потоке

Статья в свежем Phys. Rev. Lett.

Symmetry Breaking of Tail-Clamped Filaments in Stokes Flow
Jian Deng, Xuerui Mao, and Luca Brandt
Phys. Rev. Lett. 126, 124501 – Published 22 March 2021

Symmetry breaking (SB) of fluid-structure interaction problems plays an important role in our understanding of animals’ locomotive and sensing behaviors. In this Letter, we study the SB of flexible filaments clamped at one end and placed in a spanwise periodic array in Stokes flow. The equilibrium state of the filament along the streamwise direction loses stability and experiences two-dimensional and then three-dimensional SBs as the spanwise distance increases, or as the filament rigidity reduces. For slightly deformed filaments, the viscous and pressure forces are commensurate, while for extremely deformed filaments the viscous force becomes dominant.

лошадь, диаграмма, Фейнман

(no subject)

Гарсия де Абахо опять что-то интересное написал...

Optical Modulation of Electron Beams in Free Space
F. Javier García de Abajo and Andrea Konečná
Phys. Rev. Lett. 126, 123901 – Published 22 March 2021

We exploit free-space interactions between electron beams and tailored light fields to imprint on-demand phase profiles on the electron wave functions. Through rigorous semiclassical theory involving a quantum description of the electrons, we show that monochromatic optical fields focused in vacuum can be used to correct electron beam aberrations and produce selected focal shapes. Stimulated elastic Compton scattering is exploited to imprint the required electron phase, which is proportional to the integral of the optical field intensity along the electron path and depends on the transverse beam position. The required light intensities are attainable in currently available ultrafast electron microscope setups, thus opening the field of free-space optical manipulation of electron beams.

лошадь, диаграмма, Фейнман

Хаос в квантовой теории поля

Signatures of Chaos in Nonintegrable Models of Quantum Field Theories
Miha Srdinšek, Tomaž Prosen, and Spyros Sotiriadis
Phys. Rev. Lett. 126, 121602 – Published 22 March 2021

We study signatures of quantum chaos in (1+1)D quantum field theory (QFT) models. Our analysis is based on the method of Hamiltonian truncation, a numerical approach for the construction of low-energy spectra and eigenstates of QFTs that can be considered as perturbations of exactly solvable models. We focus on the double sine-Gordon, also studying the massive sine-Gordon and ϕ^4 model, all of which are nonintegrable and can be studied by this method with sufficiently high precision from small to intermediate perturbation strength. We analyze the statistics of level spacings and of eigenvector components, which are expected to follow random matrix theory predictions. While level spacing statistics are close to the Gaussian orthogonal ensemble (GOE) as expected, on the contrary, the eigenvector components follow a distribution markedly different from the expected Gaussian. Unlike in the typical quantum chaos scenario, the transition of level spacing statistics to chaotic behavior takes place already in the perturbative regime. Moreover, the distribution of eigenvector components does not appear to change or approach Gaussian behavior, even for relatively large perturbations. Our results suggest that these features are independent of the choice of model and basis.