Universe

Editorial

Jump to: Research, Review

4 pages, 164 KiB

Open AccessEditorial

Rotation Effects in Relativity

by Matteo Luca Ruggiero

Universe 2020, 6(12), 224; https://doi.org/10.3390/universe6120224 - 27 Nov 2020

Cited by 1 | Viewed by 2020

Abstract

Rotation has always been a central thread in physics and has influenced its development [...] Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

Research

Jump to: Editorial, Review

41 pages, 534 KiB

Open AccessArticle

Generalised Uncertainty Relations for Angular Momentum and Spin in Quantum Geometry

by Matthew J. Lake, Marek Miller and Shi-Dong Liang

Universe 2020, 6(4), 56; https://doi.org/10.3390/universe6040056 - 19 Apr 2020

Cited by 31 | Viewed by 3182

Abstract

We derive generalised uncertainty relations (GURs) for orbital angular momentum and spin in the recently proposed smeared-space model of quantum geometry. The model implements a minimum length and a minimum linear momentum and recovers both the generalised uncertainty principle (GUP) and extended uncertainty [...] Read more.

We derive generalised uncertainty relations (GURs) for orbital angular momentum and spin in the recently proposed smeared-space model of quantum geometry. The model implements a minimum length and a minimum linear momentum and recovers both the generalised uncertainty principle (GUP) and extended uncertainty principle (EUP), previously proposed in the quantum gravity literature, within a single formalism. In this paper, we investigate the consequences of these results for particles with extrinsic and intrinsic angular momentum and obtain generalisations of the canonical

so (3)

and

su (2)

algebras. We find that, although

SO (3)

symmetry is preserved on three-dimensional slices of an enlarged phase space, corresponding to a superposition of background geometries, individual subcomponents of the generalised generators obey nontrivial subalgebras. These give rise to GURs for orbital angular momentum while leaving the canonical commutation relations intact except for a simple rescaling,

ħ \to ħ + β

. The value of the new parameter,

β ≃ ħ \times 10^{- 61}

, is determined by the ratio of the dark energy density to the Planck density, and its existence is required by the presence of both minimum length and momentum uncertainties. Here, we assume the former to be of the order of the Planck length and the latter to be of the order of the de Sitter momentum

\sim ħ \sqrt{Λ}

, where

Λ

is the cosmological constant, which is consistent with the existence of a finite cosmological horizon. In the smeared-space model, ħ and

β

are interpreted as the quantisation scales for matter and geometry, respectively, and a quantum state vector is associated with the spatial background. We show that this also gives rise to a rescaled Lie algebra for generalised spin operators, together with associated subalgebras that are analogous to those for orbital angular momentum. Remarkably, consistency of the algebraic structure requires the quantum state associated with a flat background to be fermionic, with spin eigenvalues

\pm β / 2

. Finally, the modified spin algebra leads to GURs for spin measurements. The potential implications of these results for cosmology and high-energy physics, and for the description of spin and angular momentum in relativistic theories of quantum gravity, including dark energy, are briefly discussed. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

22 pages, 432 KiB

Open AccessArticle

Gravitoelectromagnetism, Solar System Tests, and Weak-Field Solutions in f (T,B) Gravity with Observational Constraints

by Gabriel Farrugia, Jackson Levi Said and Andrew Finch

Universe 2020, 6(2), 34; https://doi.org/10.3390/universe6020034 - 18 Feb 2020

Cited by 45 | Viewed by 3869

Abstract

Gravitomagnetism characterizes phenomena in the weak-field limit within the context of rotating systems. These are mainly manifested in the geodetic and Lense-Thirring effects. The geodetic effect describes the precession of the spin of a gyroscope in orbit about a massive static central object, [...] Read more.

Gravitomagnetism characterizes phenomena in the weak-field limit within the context of rotating systems. These are mainly manifested in the geodetic and Lense-Thirring effects. The geodetic effect describes the precession of the spin of a gyroscope in orbit about a massive static central object, while the Lense-Thirring effect expresses the analogous effect for the precession of the orbit about a rotating source. In this work, we explore these effects in the framework of Teleparallel Gravity and investigate how these effects may impact recent and future missions. We find that teleparallel theories of gravity may have an important impact on these effects which may constrain potential models within these theories. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

75 pages, 9847 KiB

Open AccessFeature PaperArticle

Influence of Cosmic Repulsion and Magnetic Fields on Accretion Disks Rotating around Kerr Black Holes

by Zdeněk Stuchlík, Martin Kološ, Jiří Kovář, Petr Slaný and Arman Tursunov

Universe 2020, 6(2), 26; https://doi.org/10.3390/universe6020026 - 29 Jan 2020

Cited by 171 | Viewed by 6237

Abstract

We present a review of the influence of cosmic repulsion and external magnetic fields on accretion disks rotating around rotating black holes and on jets associated with these rotating configurations. We consider both geometrically thin and thick disks. We show that the vacuum [...] Read more.

We present a review of the influence of cosmic repulsion and external magnetic fields on accretion disks rotating around rotating black holes and on jets associated with these rotating configurations. We consider both geometrically thin and thick disks. We show that the vacuum energy represented by the relic cosmological constant strongly limits extension of the accretion disks that is for supermassive black holes comparable to extension of largest galaxies, and supports collimation of jets at large distances from the black hole. We further demonstrate that an external magnetic field crucially influences the fate of ionized Keplerian disks causing creation of winds and jets, enabling simultaneously acceleration of ultra-high energy particles with energy up to

10^{21}

eV around supermassive black holes with

M \sim 10^{10} M_{⊙}

surrounded by sufficiently strong magnetic field with

B \sim 10^{4}

G. We also show that the external magnetic fields enable existence of “levitating” off-equatorial clouds or tori, along with the standard equatorial toroidal structures, if these carry a non-vanishing, appropriately distributed electric charge. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

► Show Figures

Figure 1

22 pages, 5584 KiB

Open AccessArticle

Electrodynamics and Radiation from Rotating Neutron Star Magnetospheres

by Jérôme Pétri

Universe 2020, 6(1), 15; https://doi.org/10.3390/universe6010015 - 15 Jan 2020

Cited by 16 | Viewed by 3347

Abstract

Neutron stars are compact objects rotating at high speed, up to a substantial fraction of the speed of light (up to 20% for millisecond pulsars) and possessing ultra-strong electromagnetic fields (close to and sometimes above the quantum critical field of 4.4 [...] Read more.

Neutron stars are compact objects rotating at high speed, up to a substantial fraction of the speed of light (up to 20% for millisecond pulsars) and possessing ultra-strong electromagnetic fields (close to and sometimes above the quantum critical field of 4.4

\times 10^{9}

T

). Moreover, due to copious

e^{\pm}

pair creation within the magnetosphere, the relativistic plasma surrounding the star is forced into corotation up to the light cylinder where the corotation speed reaches the speed of light. The neutron star electromagnetic activity is powered by its rotation which becomes relativistic in the neighborhood of this light cylinder. These objects naturally induce relativistic rotation on macroscopic scales about several thousands of kilometers, a crucial ingredient to trigger the central engine as observed on Earth. In this paper, we elucidate some of the salient features of this corotating plasma subject to efficient particle acceleration and radiation, emphasizing several problems and limitations concerning current theories of neutron star magnetospheres. Relativistic rotation in these systems is indirectly probed by the radiation produced within the magnetosphere. Depending on the underlying assumptions about particle motion and radiation mechanisms, different signatures on their light curves, spectra, pulse profiles and polarization angles are expected in their broadband electromagnetic emission. We show that these measurements put stringent constraints on the way to describe particle electrodynamics in a rotating neutron star magnetosphere. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

► Show Figures

Figure 1

39 pages, 515 KiB

Open AccessArticle

Simultaneity and Precise Time in Rotation

by Don Koks

Universe 2019, 5(12), 226; https://doi.org/10.3390/universe5120226 - 16 Dec 2019

Cited by 4 | Viewed by 4088

Abstract

I analyse the role of simultaneity in relativistic rotation by building incrementally on its role in simpler scenarios. Historically, rotation has been analysed in

1 + 1

dimensions; but my stance is that a

2 + 1

-dimensional treatment is necessary. This treatment [...] Read more.

I analyse the role of simultaneity in relativistic rotation by building incrementally on its role in simpler scenarios. Historically, rotation has been analysed in

1 + 1

dimensions; but my stance is that a

2 + 1

-dimensional treatment is necessary. This treatment requires a discussion of what constitutes a frame, how coordinate choices differ from frame choices, and how poor coordinates can be misleading. I determine how precisely we are able to define a meaningful time coordinate on a gravity-free rotating Earth, and discuss complications due to gravity on our real Earth. I end with a critique of several statements made in relativistic precision-timing literature, that I maintain contradict the tenets of relativity. Those statements tend to be made in the context of satellite-based navigation; but they are independent of that technology, and hence are not validated by its success. I suggest that if relativistic precision-timing adheres to such analyses, our civilian timing is likely to suffer in the near future as clocks become ever more precise. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

► Show Figures

Figure 1

13 pages, 541 KiB

Open AccessArticle

Monitoring Jovian Orbital Resonances of a Spacecraft: Classical and Relativistic Effects

by Luis Acedo

Universe 2019, 5(12), 222; https://doi.org/10.3390/universe5120222 - 3 Dec 2019

Cited by 1 | Viewed by 2896

Abstract

Orbital resonances continue to be one of the most difficult problems in celestial mechanics. They have been studied in connection with the so-called Kirkwood gaps in the asteroid belt for many years. On the other hand, resonant trans-Neptunian objects are also an active [...] Read more.

Orbital resonances continue to be one of the most difficult problems in celestial mechanics. They have been studied in connection with the so-called Kirkwood gaps in the asteroid belt for many years. On the other hand, resonant trans-Neptunian objects are also an active area of research in Solar System dynamics, as are the recently discovered resonances in extrasolar planetary systems. A careful monitoring of the trajectories of these objects is hindered by the small size of asteroids or the large distances of the trans-Neptunian bodies. In this paper, we propose a mission concept, called CHRONOS (after the greek god of time), in which a spacecraft could be sent to with the initial condition of resonance with Jupiter in order to study the future evolution of its trajectory. We show that radio monitoring of these trajectories could allow for a better understanding of the initial stages of the evolution of resonant trajectories and the associated relativistic effects. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

► Show Figures

Graphical abstract

14 pages, 330 KiB

Open AccessArticle

Dynamics of Electromagnetic Fields and Structure of Regular Rotating Electrically Charged Black Holes and Solitons in Nonlinear Electrodynamics Minimally Coupled to Gravity

by Irina Dymnikova and Evgeny Galaktionov

Universe 2019, 5(10), 205; https://doi.org/10.3390/universe5100205 - 27 Sep 2019

Cited by 14 | Viewed by 3234

Abstract

We study the dynamics of electromagnetic fields of regular rotating electrically charged black holes and solitons replacing naked singularities in nonlinear electrodynamics minimally coupled to gravity (NED-GR). They are related by electromagnetic and gravitational interactions and described by the axially symmetric NED-GR solutions [...] Read more.

We study the dynamics of electromagnetic fields of regular rotating electrically charged black holes and solitons replacing naked singularities in nonlinear electrodynamics minimally coupled to gravity (NED-GR). They are related by electromagnetic and gravitational interactions and described by the axially symmetric NED-GR solutions asymptotically Kerr-Newman for a distant observer. Geometry is described by the metrics of the Kerr-Schild class specified by

T_{t}^{t} = T_{r}^{r} (p_{r} = - ρ)

in the co-rotating frame. All regular axially symmetric solutions obtained from spherical solutions with the Newman-Janis algorithm belong to this class. The basic generic feature of all regular objects of this class, both electrically charged and electrically neutral, is the existence of two kinds of de Sitter vacuum interiors. We analyze the regular solutions to dynamical equations for electromagnetic fields and show which kind of a regular interior is favored by electromagnetic dynamics for NED-GR objects. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

► Show Figures

Figure 1

18 pages, 350 KiB

Open AccessArticle

Nonlocal Gravitomagnetism

by Bahram Mashhoon and Friedrich W. Hehl

Universe 2019, 5(9), 195; https://doi.org/10.3390/universe5090195 - 5 Sep 2019

Cited by 16 | Viewed by 2607

Abstract

We briefly review the current status of nonlocal gravity (NLG), which is a classical nonlocal generalization of Einstein’s theory of gravitation based on a certain analogy with the nonlocal electrodynamics of media. Nonlocal gravity thus involves integro-differential field equations and a causal constitutive [...] Read more.

We briefly review the current status of nonlocal gravity (NLG), which is a classical nonlocal generalization of Einstein’s theory of gravitation based on a certain analogy with the nonlocal electrodynamics of media. Nonlocal gravity thus involves integro-differential field equations and a causal constitutive kernel that should ultimately be determined from observational data. We consider the stationary gravitational field of an isolated rotating astronomical source in the linear approximation of nonlocal gravity. In this weak-field and slow-motion approximation of NLG, we describe the gravitomagnetic field associated with the rotating source and compare our results with gravitoelectromagnetism (GEM) of the standard general relativity theory. Moreover, we briefly study the energy-momentum content of the GEM field in nonlocal gravity. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

20 pages, 1214 KiB

Open AccessArticle

Kerr Black Holes within a Modified Theory of Gravity

by Peter O. Hess and Enrique López-Moreno

Universe 2019, 5(9), 191; https://doi.org/10.3390/universe5090191 - 28 Aug 2019

Cited by 14 | Viewed by 3701

Abstract

The Kerr black hole is studied within a modified theory of gravity, which adds the effects of vacuum fluctuations near a black hole. These vacuum fluctuations are treated as a dark energy. A parameter is introduced to account for these fluctuations. It is [...] Read more.

The Kerr black hole is studied within a modified theory of gravity, which adds the effects of vacuum fluctuations near a black hole. These vacuum fluctuations are treated as a dark energy. A parameter is introduced to account for these fluctuations. It is zero for the standard theory and acquires a maximal value, just before there would be no event horizon. The existence of an event horizon not only depends on the value of this parameter, but also on the spin of the black hole. In addition, we study the existence of a light-ring. We also elaborate on the relation of the appearance and vanishing of the event horizon and light-ring to phase transitions. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

► Show Figures

Figure 1

11 pages, 1106 KiB

Open AccessArticle

Rotation Sensing Lasers in General Relativity: Some Technical Notes and Current Advances

by K. Ulrich Schreiber, André Gebauer, Jan Kodet, Caroline L. Anyi and Jon-Paul R. Wells

Universe 2019, 5(9), 190; https://doi.org/10.3390/universe5090190 - 21 Aug 2019

Cited by 2 | Viewed by 2758

Abstract

We review the current status of large ring laser gyroscopes having the potential to contribute to terrestrial measurements of general relativistic precessions. At this point in time, although these devices possess the raw sensitivity for such a measurement, they remain limited by long-term [...] Read more.

We review the current status of large ring laser gyroscopes having the potential to contribute to terrestrial measurements of general relativistic precessions. At this point in time, although these devices possess the raw sensitivity for such a measurement, they remain limited by long-term geometric instability, detection noise and imperfections in the physical models required to isolate geophysical effects. Furthermore, minute non-reciprocal biases provide a null-shift error and therefore no currently constructed laser system meets the requirement of absolute rotation rate sensing. Nevertheless, we are of the view that these are surmountable problems and the ability of ring laser gyroscopes to measure low frequency to DC signals has vastly increased in the last decade. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

► Show Figures

Figure 1

8 pages, 230 KiB

Open AccessArticle

A Theory of Inertia Based on Mach’s Principle

by Volkmar Putz

Universe 2019, 5(8), 188; https://doi.org/10.3390/universe5080188 - 16 Aug 2019

Cited by 3 | Viewed by 3843

Abstract

A non-relativistic theory of inertia based on Mach’s principle is presented as has been envisaged, but not achieved, by Ernst Mach in 1872. The central feature is a space-dependent, anisotropic, symmetric inert mass tensor. The contribution of a mass element

d m

to [...] Read more.

A non-relativistic theory of inertia based on Mach’s principle is presented as has been envisaged, but not achieved, by Ernst Mach in 1872. The central feature is a space-dependent, anisotropic, symmetric inert mass tensor. The contribution of a mass element

d m

to the inertia of a particle

m_{0}

experiencing an acceleration from rest is proportional to

{cos}^{2} α

, where

α

is the angle between the line connecting

m_{0}

and

d m

and the direction of the acceleration. Apsidal precession for planets circling around a central star is not a consequence of this theory, thereby avoiding the prediction of an apsidal precession with the wrong sign as is done by Mach-like theories with isotropic inert mass. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

► Show Figures

Figure 1

26 pages, 1114 KiB

Open AccessEditor’s ChoiceArticle

A HERO for General Relativity

by Lorenzo Iorio

Universe 2019, 5(7), 165; https://doi.org/10.3390/universe5070165 - 5 Jul 2019

Cited by 7 | Viewed by 3626

Abstract

HERO (Highly Eccentric Relativity Orbiter) is a space-based mission concept aimed to perform several tests of post-Newtonian gravity around the Earth with a preferably drag-free spacecraft moving along a highly elliptical path fixed in its plane undergoing a relatively fast secular precession. We [...] Read more.

HERO (Highly Eccentric Relativity Orbiter) is a space-based mission concept aimed to perform several tests of post-Newtonian gravity around the Earth with a preferably drag-free spacecraft moving along a highly elliptical path fixed in its plane undergoing a relatively fast secular precession. We considered two possible scenarios—a fast, 4-h orbit with high perigee height of

1047 km

and a slow, 21-h path with a low perigee height of

642 km

. HERO may detect, for the first time, the post-Newtonian orbital effects induced by the mass quadrupole moment

J_{2}

of the Earth which, among other things, affects the semimajor axis a via a secular trend of ≃4–12

cm {yr}^{- 1}

, depending on the orbital configuration. Recently, the secular decay of the semimajor axis of the passive satellite LARES was measured with an error as little as

0.7 cm {yr}^{- 1}

. Also the post-Newtonian spin dipole (Lense-Thirring) and mass monopole (Schwarzschild) effects could be tested to a high accuracy depending on the level of compensation of the non-gravitational perturbations, not treated here. Moreover, the large eccentricity of the orbit would allow one to constrain several long-range modified models of gravity and accurately measure the gravitational red-shift as well. Each of the six Keplerian orbital elements could be individually monitored to extract the

G J_{2} / c^{2}

signature, or they could be suitably combined in order to disentangle the post-Newtonian effect(s) of interest from the competing mismodeled Newtonian secular precessions induced by the zonal harmonic multipoles

J_{ℓ}

of the geopotential. In the latter case, the systematic uncertainty due to the current formal errors

σ_{J_{ℓ}}

of a recent global Earth’s gravity field model are better than

1 %

for all the post-Newtonian effects considered, with a peak of

≃ 10^{- 7}

for the Schwarzschild-like shifts. Instead, the gravitomagnetic spin octupole precessions are too small to be detectable. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

► Show Figures

Figure A1

9 pages, 265 KiB

Open AccessArticle

Gravitational Radiation, Vorticity And Super–Energy: A Conspicuous Threesome

by Luis Herrera

Universe 2019, 5(7), 164; https://doi.org/10.3390/universe5070164 - 4 Jul 2019

Cited by 3 | Viewed by 2397

Abstract

We elaborate on the link relating gravitational radiation, vorticity and a flux of super–energy on the plane orthogonal to the vorticity vector. We examine the vorticity appearing in the congruence of observers at the outside of the source, as well as the vorticity [...] Read more.

We elaborate on the link relating gravitational radiation, vorticity and a flux of super–energy on the plane orthogonal to the vorticity vector. We examine the vorticity appearing in the congruence of observers at the outside of the source, as well as the vorticity of the fluid distribution, the source of the gravitational radiation is made of. The information provided by the study of the physical aspects of the source poses new questions which could, in principle, be solved by the observational evidence. Besides the study of the theoretical issues associated to such relationship, we also stress the new observational possibilities to detect gravitational radiation, appearing as consequence of the above mentioned link. The high degree of development achieved in the gyroscope technology, as well as recent proposals to detect rotations by means of ring lasers, atom interferometers, atom lasers and anomalous spin–precession experiments, lead us to believe that an alternative to the laser interferometers used so far to detect gravitational waves, may be implemented based on the detection of the vorticity associated with gravitational radiation. Additionally, this kind of detectors might be able to elucidate the open question about the physical properties of the tail of the waves appearing as the consequence of the violation of the Huygens’s principle in general relativity. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

19 pages, 368 KiB

Open AccessArticle

Gravitational Qubits

by Giorgio Papini

Universe 2019, 5(5), 123; https://doi.org/10.3390/universe5050123 - 21 May 2019

Cited by 3 | Viewed by 2595

Abstract

We report on the behavior of two-level quantum systems, or qubits, in the background of rotating and non-rotating metrics and provide a method to derive the related spin currents and motions. The calculations are performed in the external field approximation. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

Review

Jump to: Editorial, Research

15 pages, 289 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Measuring Electromagnetic Fields in Rotating Frames of Reference

by Clive C. Speake and Antonello Ortolan

Universe 2020, 6(2), 31; https://doi.org/10.3390/universe6020031 - 11 Feb 2020

Cited by 7 | Viewed by 4279

Abstract

We review the problem of transforming electromagnetic fields between inertial and rotating reference frames. We compare the method of straightforward tensor coordinate transformations adopted by Schiff in his well-known paper of 1939 with the method of Orthogonal Tetrads (OT) that was applied to [...] Read more.

We review the problem of transforming electromagnetic fields between inertial and rotating reference frames. We compare the method of straightforward tensor coordinate transformations adopted by Schiff in his well-known paper of 1939 with the method of Orthogonal Tetrads (OT) that was applied to this problem in 1964 by Irvine. Although both methods are mathematically rigorous, the transformed fields have different forms depending on the method adopted. We emphasize that the OT method is expected to predict the fields that would actually be measured by an observer in a rotating frame of reference. We briefly discuss existing experimental evidence that supports the OT approach, but point out that there appears to be little awareness in the physics community of this problem or its resolution. We use both methods to transform the electrostatic and magnetic fields generated by rotating charged spherical shells from an inertial into a co-rotating system. We also briefly describe how such an arrangement of shells could be used to measure rotation relative to the fixed stars. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

11 pages, 407 KiB

Open AccessFeature PaperReview

Rotating Disc around a Schwarzschild Black Hole

by Oldřich Semerák and Pavel Čížek

Universe 2020, 6(2), 27; https://doi.org/10.3390/universe6020027 - 3 Feb 2020

Cited by 2 | Viewed by 2838

Abstract

A stationary and axisymmetric (in fact circular) metric is reviewed which describes the first-order perturbation of a Schwarzschild black-hole space-time due to a rotating finite thin disc encircling the hole symmetrically. The key Green functions of the problem (corresponding to an infinitesimally thin [...] Read more.

A stationary and axisymmetric (in fact circular) metric is reviewed which describes the first-order perturbation of a Schwarzschild black-hole space-time due to a rotating finite thin disc encircling the hole symmetrically. The key Green functions of the problem (corresponding to an infinitesimally thin ring)—the one for the gravitational potential and the one for the dragging angular velocity—were already derived, in terms of infinite series, by Will in 1974, but we have now put them into closed forms using elliptic integrals. Such forms are more practical for numerical evaluation and for integration in problems involving extended sources. This last point mostly remains difficult, but we illustrate that it may be workable by using the simple case of a finite thin disc with constant Newtonian surface density. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

► Show Figures

Figure 1

7 pages, 229 KiB

Open AccessReview

Rotation and Spin and Position Operators in Relativistic Gravity and Quantum Electrodynamics

by Robert F. O’Connell

Universe 2020, 6(2), 24; https://doi.org/10.3390/universe6020024 - 26 Jan 2020

Cited by 2 | Viewed by 2260

Abstract

First, we examine how spin is treated in special relativity and the necessity of introducing spin supplementary conditions (SSC) and how they are related to the choice of a center-of-mass of a spinning particle. Next, we discuss quantum electrodynamics and the Foldy–Wouthuysen transformation [...] Read more.

First, we examine how spin is treated in special relativity and the necessity of introducing spin supplementary conditions (SSC) and how they are related to the choice of a center-of-mass of a spinning particle. Next, we discuss quantum electrodynamics and the Foldy–Wouthuysen transformation which we note is a position operator identical to the Pryce–Newton–Wigner position operator. The classical version of the operators are shown to be essential for the treatment of classical relativistic particles in general relativity, of special interest being the case of binary systems (black holes/neutron stars) which emit gravitational radiation. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

89 pages, 1802 KiB

Open AccessFeature PaperReview

In the Quest for Cosmic Rotation

by Vladimir A. Korotky, Eduard Masár and Yuri N. Obukhov

Universe 2020, 6(1), 14; https://doi.org/10.3390/universe6010014 - 15 Jan 2020

Cited by 5 | Viewed by 3174

Abstract

This paper analyzes the problem of global rotation in general relativity (GR) theory. Simple cosmological models with rotation and expansion are presented, which give a natural explanation of the modern values of the acceleration parameter at different red shifts without involving the concepts [...] Read more.

This paper analyzes the problem of global rotation in general relativity (GR) theory. Simple cosmological models with rotation and expansion are presented, which give a natural explanation of the modern values of the acceleration parameter at different red shifts without involving the concepts of “dark energy” and “dark matter”. It is shown that due to the smallness of the cosmological rotation, for its detection one should use observations that do not depend on the magnitude of the angular velocity of the Universe. Such tests include the effects of the cosmic mirror and the cosmic lens. For the first time on the basis of modern electronic catalogs the search on the celestial sphere of images of our Galaxy and other galaxies is made. Viable candidates for both effects have been found. Full article

(This article belongs to the Special Issue Rotation Effects in Relativity)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Rotation Effects in Relativity

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Published Papers (19 papers)

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI