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The spherical centroid body of a centrally-symmetric convex body in the Euclidean unit sphere is introduced. Two alternative definitions - one geometric, the other probabilistic in nature - are given and shown to lead to the same objects.…

Metric Geometry · Mathematics 2019-02-28 Florian Besau , Thomas Hack , Peter Pivovarov , Franz E. Schuster

In this work, we present an adaptation of the classical stereographic projection, originally formulated for the sphere, now considering the context of the ellipsoid and the elliptic paraboloid. We begin by constructing the stereographic…

Differential Geometry · Mathematics 2025-06-11 W. F. C. Barboza , T. F. Cruz , R. B. Leal

Over the past decade, the BeSSeL Survey and the VERA project have measured trigonometric parallaxes to approximately 250 massive, young stars using VLBI techniques. These sources trace spiral arms over nearly half of the Milky Way. What is…

Instrumentation and Methods for Astrophysics · Physics 2022-09-21 Mark J Reid

Visible-light long baseline interferometry holds the promise of advancing a number of important applications in fundamental astronomy, including the direct measurement of the angular diameters and oblateness of stars, and the direct…

An all-spherical catadioptic telescope with the angular field of view of several tens of degrees in diameter and spherical focal surface is proposed for the monitoring of large sky areas. We provide a few examples of such a system with the…

Instrumentation and Methods for Astrophysics · Physics 2016-07-20 V. Yu. Terebizh

Second order perturbation theory predicts a specific dependence of the bispectrum, or three-point correlation function in the Fourier transform domain, on the shape of the configuration of its three wave vector arguments, which can be taken…

Astrophysics · Physics 2009-10-31 J. N. Fry , David Thomas

A simple and intuitive geometical method to analyze Fresnel formulas is presented. It applies to transparent media and is valid for perpendicular and parallel polarizations. The approach gives a graphical characterization particularly…

Optics · Physics 2009-11-07 J. J. Monzon , L. L. Sanchez-Soto

Parallax measurements allow distances to celestial objects to be determined. Coupled with measurement of their position on the celestial sphere, it gives a full three-dimensional picture of the location of the objects relative to the…

Astrophysics · Physics 2015-06-24 M. V. Sazhin , V. E. Zharov , T. A. Kalinina

High precision astrometric Space Very Long Baseline Interferometry (S-VLBI) at the low end of the conventional frequency range, i.e. 20cm, is a requirement for a number of high priority science goals. These are headlined by obtaining…

Instrumentation and Methods for Astrophysics · Physics 2015-06-15 R. Dodson , M. Rioja , Y. Asaki , H. Imai , X. -Y. Hong , Z. Shen

Astronomical imaging can be broadly classified into two types. The first type is amplitude interferometry, which includes conventional optical telescopes and Very Large Baseline Interferometry (VLBI). The second type is intensity…

Instrumentation and Methods for Astrophysics · Physics 2022-05-04 Manuel Bojer , Zixin Huang , Sebastian Karl , Stefan Richter , Pieter Kok , J. von Zanthier

A well studied family of random fractals called fractal percolation is discussed. We focus on the projections of fractal percolation on the plane. Our goal is to present stronger versions of the classical Marstrand theorem, valid for almost…

Dynamical Systems · Mathematics 2013-06-18 Michal Rams , Károly Simon

High precision differential astrometry assesses the positions, distances, and motions of celestial objects in relation to the stars. The focal plane of such space telescope must be calibrated with a precision down to the level of 1e-5 pixel…

Instrumentation and Methods for Astrophysics · Physics 2024-10-30 Fabrice Pancher , Sebastien Soler , Fabien Malbet , Manon Lizzana , Pierre Kern , Thierry Lepine , Alain Leger

Observing artificial satellites is a relatively new and unique branch of astronomy that is very interesting and dynamic. One specific aspect of observing these objects is that although they appear amongst the celestial background, as…

Space Physics · Physics 2015-07-02 Michael A. Earl

Stochastic microlensing is a central tool in probing dark matter on galactic scales. From first principles, we initiate the development of a mathematical theory of stochastic microlensing. Beginning with the random time delay function and…

Astrophysics · Physics 2015-05-13 Arlie O. Petters , Brian Rider , Alberto M. Teguia

Extraterrestrial communication signals are hypothesized to be present in an extensive search space. Using principles of communication theory and system design, methods are studied and implemented to reduce the signal search space, while…

Signal Processing · Electrical Eng. & Systems 2024-04-16 William J. Crilly

Using very long baseline interferometry data for the sources that comprise the third International Celestial Reference Frame (ICRF3), we examine the quality of the formal source position uncertainties of ICRF3 by determining the excess…

Instrumentation and Methods for Astrophysics · Physics 2024-08-05 Phil Cigan , Valeri Makarov , Nathan Secrest , David Gordon , Megan Johnson , Sebastien Lambert

Geometric constructions are widely used in computer graphics and engineering drawing. A right generalized cylinder is a ruled surface whose base curve is a plane curve perpendicular to the rulings. The paper discusses relations between the…

Differential Geometry · Mathematics 2024-11-27 C. L. Dinkova , R. P. Encheva , A. A. Ali

In this paper, we review the various ways in which an infrared stellar interferometer can be used to perform direct detection of extrasolar planetary systems. We first review the techniques based on classical stellar interferometry, where…

Instrumentation and Methods for Astrophysics · Physics 2015-03-17 O. Absil

In order to understand the nature of the lenses that generate microlensing events, one would like to measure their mass, distance, and velocity. Unfortunately, current microlensing experiments measure only one parameter of the events, the…

Astrophysics · Physics 2009-10-28 B. Scott Gaudi , Andrew Gould

We propose a method to build an astronomical interferometer using continuous variable quantum teleportation to overcome the transmission loss between distant telescopes. The scheme relies on two-mode squeezed states shared by distant…

Quantum Physics · Physics 2025-09-03 Yunkai Wang , Yujie Zhang , Virginia O. Lorenz