Results 91 to 100 of about 1,337 (262)

Self-gravitating stellar collapse: explicit geodesics and path integration

Frontiers in Astronomy and Space Sciences, 2016
We extend the work of Oppenheimer-Synder to model the gravitational collapse of a star to a black hole by including quantum mechanical effects. We first derive closed-form solutions for classical paths followed by a particle on the surface of the ...
Jayashree Balakrishna, Ruxandra Bondarescu, Christine Corbett-Moran   +2 more
doaj   +1 more source

Refining techniques for high‐frequency monitoring of chlorophyll a fluorescence in estuarine systems

Limnology and Oceanography: Methods, EarlyView.
Abstract Concentrations of the photosynthetic pigment chlorophyll a are commonly used as a proxy for phytoplankton biomass in aquatic systems. Traditional methods for extracting chlorophyll a in discrete samples limit measurement frequency, while in situ sensor technology provides high frequency chlorophyll a fluorescence measurements at a more ...
Nicole Dix, Hannah Nicklay, Jacob Cianci‐Gaskill, Shannon Dunnigan Kimmel, J. Silas Tanner, Kim Cressman, Steven E. McMurray, Yoshimi M. Rii, Rikke Jeppesen, Rachel Guy, Erik Smith   +10 more
wiley   +1 more source

There Are No Conformal Einstein Rescalings of Pseudo-Riemannian Einstein Spaces with n Complete Light-Like Geodesics

Mathematics, 2019
In the present paper, we study conformal mappings between a connected n-dimension pseudo-Riemannian Einstein manifolds. Let g be a pseudo-Riemannian Einstein metric of indefinite signature on a connected n-dimensional manifold M.
Josef Mikeš, Irena Hinterleitner, Nadezda Guseva   +2 more
doaj   +1 more source

Visibility and Intersection Density for Boolean Models in Hyperbolic Space

Mathematische Nachrichten, EarlyView.
ABSTRACT For Poisson particle processes in hyperbolic space we introduce and study concepts analogous to the intersection density and the mean visible volume, which were originally considered in the analysis of Boolean models in Euclidean space. In particular, we determine a necessary and sufficient condition for the finiteness of the mean visible ...
Tillmann Bühler, Daniel Hug, Christoph Thäle   +2 more
wiley   +1 more source

A Geometric Interpretation for the Algebraic Properties of Second‐Order Ordinary Differential Equations

Mathematical Methods in the Applied Sciences, Volume 48, Issue 6, Page 6912-6917, April 2025.
ABSTRACT Nowadays, a substantial portion of investigations concerning the symmetry analysis of differential equations predominantly adhere to a framework comprising the following key procedures: (i) the derivation of symmetries, (ii) the determination of an optimal system, (iii) the utilization of these symmetries to construct invariants or ...
A. Paliathanasis, S. Moyo, P. G. L. Leach   +2 more
wiley   +1 more source

Analytic study of self-gravitating polytropic spheres with light rings

European Physical Journal C: Particles and Fields, 2018
Ultra-compact objects describe horizonless solutions of the Einstein field equations which, like black-hole spacetimes, possess null circular geodesics (closed light rings).
Shahar Hod
doaj   +1 more source

On Geometric Phase Model in the Theory of Curves With Myller Configuration

Mathematical Methods in the Applied Sciences, EarlyView.
ABSTRACT In this paper, we introduce a linearly polarized light wave in an optical fiber and rotation of the polarization plane through the Frenet‐type frame with Myller configuration. Since the geometric evaluation and interpretations of a polarized light wave are associated with geometric phase, a new type of geometric phase model has been ...
Zehra İşbilir, Bahar Doğan Yazıcı, Murat Tosun   +2 more
wiley   +1 more source

Beyond Directions: Symmetry‐Aware Rotation Sets for Triaxial Diffusion Encoding by Geometric Filter Optimization

Magnetic Resonance in Medicine, EarlyView.
ABSTRACT Purpose To improve the accuracy of diffusion‐weighted powder average signals for diffusion encoding with arbitrary b‐tensors. Methods We identify an intrinsic dihedral (D2$$ {D}_2 $$) symmetry of diffusion signals for arbitrary diffusion encoding, which defines their natural signal space (a quotient of 3D rotations).
Sune Nørhøj Jespersen, Filip Szczepankiewicz   +1 more
wiley   +1 more source

Main‐chain polyfullerenes: Taking fullerene to the next dimension

Polymer International, EarlyView.
This short review appraises main‐chain polyfullerenes. Their slow development over 30 years has suddenly boomed with a rapid growth due to exciting developments in solar energy. Abstract This mini‐review gives an overview of the development, chemistry, properties and applications of main‐chain polyfullerenes.
Marco Antônio GB Gomes, Orisson Ponce Gomes, Patricia Targon Campana, Didier Bégué, Roger C Hiorns   +4 more
wiley   +1 more source

Quantifying the Surface Deformation of Pingos on the Alaskan North Slope Using Interferometric Synthetic Aperture Radar (InSAR)

Permafrost and Periglacial Processes, EarlyView.
ABSTRACT Pingos are large mounds with cores formed of intrusive ice that form in periglacial landscapes. These ice structures can form in regions of discontinuous permafrost, commonly as hydraulic or open‐system pingos, or in locations of continuous permafrost, commonly as hydrostatic or closed‐system pingos.
Venezia M. Follingstad, Roger J. Michaelides, Matthew R. Siegfried, Tyler M. Meng, John Bradford, Kynan H. G. Hughson, Alexia R. Kubas, Andrew Mullen, Enrica Quartini, Austin Routt, Hanna G. Sizemore, Andrei Swidinsky, Britney E. Schmidt   +12 more
wiley   +1 more source