scholarly journals Quasi-Local Energy-Momentum and Angular Momentum in GR: A Review Article

2004 ◽  
Vol 7 (1) ◽  
Author(s):  
László B. Szabados
Keyword(s):  
Angular Momentum ◽  
Review Article ◽  
Local Energy

scholarly journals 2 × 2 Matrices: Manifolds, Realizations, Applications

2021 ◽  
Vol 11 (16) ◽  
pp. 7479
Author(s):  
Kenan Uriostegui ◽  
Kurt Bernardo Wolf
Keyword(s):  
Angular Momentum ◽  
Light Propagation ◽  
Double Cover ◽  
Quantum Spin ◽  
Review Article ◽  
Matrix Group ◽  
Wave Optics ◽  
Linear Transformations ◽  
Wave Models ◽  
Classical And Quantum Mechanics

Both geometric and wave optical models, as well as classical and quantum mechanics, realize linear transformations with matrices; for plane optics, these are 2×2 and of unit determinant. Students and some researchers could assume that the structure of this matrix group is fairly evident and hardly interesting. However, the properties and applications even of this lowest 2×2 case are already unexpectedly rich. While in mechanics they cover classical angular momentum, quantum spin, and represent ‘2+1’ relativity, in optical models they lead from the geometrical description of light propagation in the paraxial regime to wave optics via linear canonical transforms requiring a more penetrating view of their manifold structure and multiple covers. The purpose of this review article is to highlight the topological space of 2×2 matrices as it applies to classical versus quantum and wave models, to underline how the latter requires the double cover of the former, thus using 2×2 matrices as an alternative viewpoint of the quantization process, beside the traditional characterization by commutation and non-commutations of position and momentum.

scholarly journals On the Jeans Theorem and the “Tolman–Oppenheimer–Volkoff Equation” inR2Gravity

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Rishabh Jain ◽  
Burra G. Sidharth ◽  
Christian Corda
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Vlasov Equation ◽  
Final Section ◽  
Essential Element ◽  
Partial Solution ◽  
Spherically Symmetric ◽  
Stationary States ◽  
Local Energy ◽  
Star Density

Corda, Mosquera Cuesta, and Lorduy Gòmez have shown that spherically symmetric stationary states can be used as a model for galaxies in the framework of the linearizedR2gravity. Those states could represent a partial solution to the Dark Matter Problem. Here, we discuss an improvement of this work. In fact, as the star density is a functional of the invariants of the associated Vlasov equation, we show that any of these invariants is in its turn a functional of the local energy and the angular momentum. As a consequence, the star density depends only on these two integrals of the Vlasov system. This result is known as the “Jeans theorem.” In addition, we find an analogy of the historical Tolman–Oppenheimer–Volkoff equation for the system considered in this paper. For the sake of completeness, in the final section of the paper, we consider two additional models which argue that Dark Matter could not be an essential element.

Desiderata in connection by the calibration of the MK-system

1966 ◽  
Vol 24 ◽  
pp. 348-349
Author(s):  
Th. Schmidt-Kaler
Keyword(s):  
Absolute Magnitude ◽  
Review Article ◽  
Stellar Systems ◽  
Astronomical Data ◽  
Intrinsic Colour

This is only an informal remark about some difficulties I am worrying about.I have tried to recalibrate the MK system in terms of intrinsic colour (B–V)0and absolute magnitudeMv. The procedures used have been described in a review article by Voigt (Mitt. Astr. Ges.1963, p. 25–35), and the results for stars of the luminosity classes Ia-O,I and II have been given also in Blaauw's article on the calibration of luminosity criteria in vol. III (Basic Astronomical Data, p. 401) ofStars and Stellar Systems.

Electron-deficient boron-based catalysts for C–H bond functionalisation

2021 ◽  
Author(s):  
Yuanhong Ma ◽  
Shao-Jie Lou ◽  
Zhaomin Hou
Keyword(s):  
Review Article ◽  
Current Status ◽  
Comprehensive Overview

This review article provides a comprehensive overview to recognise the current status of electron-deficient boron-based catalysis in C–H functionalisations.

Amino-functional polyethers: versatile, stimuli-responsive polymers

2020 ◽  
Vol 11 (24) ◽  
pp. 3940-3950 ◽  
Author(s):  
Patrick Verkoyen ◽  
Holger Frey
Keyword(s):  
Ring Opening ◽  
Review Article ◽  
Stimuli Responsive ◽  
New Class ◽  
Stimuli Responsive Polymers ◽  
Responsive Polymers

Amino-functional polyethers have emerged as a new class of “smart”, i.e. pH- and thermoresponsive materials. This review article summarizes the synthesis and applications of these materials, obtained from ring-opening of suitable epoxide monomers.

Developing Evidence-Based Assessment to Prevent Over- or Underidentification of Disorders for New Language Learners

2020 ◽  
Vol 5 (4) ◽  
pp. 1026-1038
Author(s):  
Sandra Levey ◽  
Li-Rong Lilly Cheng ◽  
Diana Almodovar
Keyword(s):  
Language Learners ◽  
Grade Level ◽  
Reading Skills ◽  
Language Disorder ◽  
Academic Development ◽  
Review Article ◽  
Evidence Based ◽  
Clinical Knowledge ◽  
Language And Literacy ◽  
Support Evidence

Purpose The purpose of this review article is to present certain linguistic domains to consider in the assessment of children learning a new language. Speech-language pathologists frequently face difficulty when determining if a bilingual or multilingual child possesses a true speech or language disorder. Given the increased number of new language learners across the world, clinicians must understand differences versus disorders to prevent underidentification or overidentification of a disorder. Conclusions Early identification of a true disorder has been shown to prevent language and literacy difficulties, given that children are able to achieve grade-level reading skills when given intervention. Clinical knowledge and skills are strongly required so that children receive evidence-based assessment to support their academic development. Learning Goal Readers will gain an understanding of the factors that support evidence-based assessment of bilingual and multilingual language learners.

Treatment Considerations for Adolescents Who Exhibit Cognitive/Communication Problems: A Neuroscience Perspective

2020 ◽  
Vol 5 (6) ◽  
pp. 1767-1775
Author(s):  
Martha S. Burns
Keyword(s):  
Social Communication ◽  
Transition Period ◽  
Clinical Intervention ◽  
Review Article ◽  
Sensitive Period ◽  
Clinical Implications ◽  
Evidence Based ◽  
Communication Problems ◽  
Treatment Considerations ◽  
Behavioral Growth

Purpose Adolescence is a period of substantial neurophysiological and behavioral growth, representing a second sensitive period of brain development. It is a psychological and social transition period between childhood and adulthood with many beneficial changes occurring, especially with respect to potential responsiveness to clinical intervention. However, adolescent behavioral complexities introduce clinical challenges as well. The purpose of this review article is to review the current neuroimaging research on neurophysiological changes observed during adolescence and the cognitive and social behavioral counterparts, with specific attention to the clinical implications. The review article will then summarize currently available intervention tools that can be utilized by speech-language pathologists working with this population. It will conclude with available evidence-based social-communication approaches that may be applicable as well as available evidence-based supplemental technological cognitive interventions that may be useful in working with adolescents who exhibit language and communication issues. Conclusion As a transition period between childhood and adulthood, adolescence represents a second sensitive period during which there is opportunity for clinically derived beneficial cognitive and communication growth.

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