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Boundary layers in turbulent flows require fine grid spacings near the walls which depend on the choice of turbulence model. To satisfy these requirements a semi-structured mesh is generally used in this area with orthogonal and layered…

流体动力学 · 物理学 2014-05-06 Kedar C. Chitale , Michel Rasquin , Onkar Sahni , Mark S. Shephard , Kenneth E. Jansen

In the present paper we consider quantitative estimation of the tolerances widening in optical systems with curved detectors. The gain in image quality allows to loosen the margins for manufacturing and assembling errors. On another hand,…

We investigate the construction of early stopping rules in the nonparametric regression problem where iterative learning algorithms are used and the optimal iteration number is unknown. More precisely, we study the discrepancy principle, as…

统计理论 · 数学 2020-04-21 Alain Celisse , Martin Wahl

With the discovery of gravitational waves and fast radio bursts, wave optics has become increasingly relevant in astrophysics. This paper studies the behaviour of random gravitational and plasma lenses, presenting the refractive and…

宇宙学与河外天体物理 · 物理学 2026-02-26 Job Feldbrugge , Samuel Crew , Ue-Li Pen

When gravitational waves propagate near massive objects, their paths curve resulting in gravitational lensing, which is expected to be a promising new instrument in astrophysics. If the time delay between different paths is comparable with…

广义相对论与量子宇宙学 · 物理学 2022-07-14 Oleg Bulashenko , Helena Ubach

There is recent interest in the use of light beams carrying orbital angular momentum (OAM) for creating multiple channels within free-space optical communication systems. One limiting issue is that, for a given beam size at the transmitter,…

量子物理 · 物理学 2015-06-23 Miles J. Padgett , Filippo M. Miatto , Martin Lavery , Anton Zeilinger , Robert W. Boyd

Goos-Haenchen and Imbert-Fedorov shifts are diffractive corrections to geometrical optics that have been extensively studied for a Gaussian beam that is reflected or transmitted by a dielectric interface. Propagating in free space before…

光学 · 物理学 2015-05-20 Andrea Aiello , J. P. Woerdman

The advisability of the use of the Fresnel number as the measure (characteristic) of the ratio of diffraction and focusing properties for ultrasonic transducers and its radiated beams is proposed and demonstrated. Althought this…

流体动力学 · 物理学 2008-01-10 Yu. N. Makov , V. J. Sanchez-Morcillo

Consider a perfect AO system with a very fine wavefront sampling interval and a very small actuator interval. If this AO system senses wavefront at a wavelength, lambda_{WFS}, and does science imaging at another wavelength, lambda_{SCI},…

天体物理学 · 物理学 2008-11-26 Tadashi Nakajima

The laws of geometric optics and their corrections are derived for scalar, electromagnetic, and gravitational waves propagating in generic curved spacetimes. Local peeling-type results are obtained, where different components of…

广义相对论与量子宇宙学 · 物理学 2019-01-08 Abraham I. Harte

A cornerstone equation of optics, Snell's law, relates the angles of incidence and refraction for light passing through an interface between two media. It is built on two fundamental constrains: the conservation of tangential momentum and…

光学 · 物理学 2015-07-20 Amr Shaltout , Alexander Kildishev , Vladimir Shalaev

Context. Adaptive optics (AO) is now a tool commonly deployed in astronomy. The real time correction of the atmospheric turbulence that AO enables allows telescopes to perform close to the diffraction limit at the core of their point spread…

天体物理仪器与方法 · 物理学 2023-06-21 Anthony Berdeu , Michel Tallon , Éric Thiébaut , Maud Langlois

We investigate theoretically the Goos-H\"anchen (GH) shift of a p-polarized terahertz beam incident on a 2D material surface with complex conductivity. Taking monolayer graphene to be the model material, we determine the dependence of GH…

The development of new techniques for characterizing atmospheric optical turbulence (OT) has become an active topic of research again in recent years. In order to facilitate these studies, we reconsidered known theoretical results and…

天体物理仪器与方法 · 物理学 2021-08-18 Victor Kornilov , Boris Safonov , Matwey Kornilov

The present study addresses the question of total internal reflection of a plane wave from an amplifying or attenuating medium. Inspection on the expressions for the modal gain or loss of an asymmetric planar waveguide having an amplifying…

光学 · 物理学 2020-10-22 Takeyuki Kobayashi

It is well known that magnification bias, the modulation of galaxy or quasar source counts by gravitational lensing, can change the observed angular correlation function. We investigate magnification-induced changes to the shape of the…

天体物理学 · 物理学 2008-12-18 Marilena LoVerde , Lam Hui , Enrique Gaztanaga

Adaptive optics (AO) has revolutionized imaging in {fields} from astronomy to microscopy by correcting optical aberrations. In label-free microscopes, however, conventional AO faces limitations due to the absence of guidestar and the need…

Angular filter refractometry is an optical diagnostic that measures absolute contours of line-integrated density gradient by placing a filter with alternating opaque and transparent zones in the focal plane of a probe beam, which produce…

等离子体物理 · 物理学 2023-11-30 P. V. Heuer , D. Haberberger , S. T. Ivancic , C. A. Walsh , J. R. Davies

We present an analytical derivation of the on-axis performance of Adaptive Optics systems using a given number of guide stars of arbitrary altitude, distributed at arbitrary angular positions in the sky. The expressions of the residual…

天体物理仪器与方法 · 物理学 2015-06-17 E. Tatulli , A. N. Ramaprakash

We consider reflection and transmission of polarized paraxial light beams at a plane dielectric interface. The field transformations taking into account a finite beam width are described based on the plane-wave representation and geometric…

光学 · 物理学 2013-01-18 Konstantin Y. Bliokh , Andrea Aiello