Narrow Results

The relativistic quantum interference effects in the spacetime of slowly rotating object in the Hořava–Lifshitz gravity as the Sagnac effect and phase shift of interfering particle in neutron interferometer are derived. We consider the extension of Kehagias–Sfetsos (KS) solution⁴⁸ in the Hořava–Lifshitz gravity for the slowly rotating gravitating object. Using the covariant Klein–Gordon equation in the nonrelativistic approximation, it is shown that the phase shift in the interference of particles includes the gravitational potential term with the KS parameter ω. It is found that in the case of the Sagnac effect, the influence of the KS parameter ω is becoming important due to the fact that the angular velocity of the locally non-rotating observer is increased in Hořava gravity. From the results of the recent experiments⁵⁰ we have obtained lower limit for the coupling KS constant as ω ≃ 1.25 ⋅10^-25cm^-2. Finally, as an example, we apply the obtained results to the calculation of the UCN (ultra-cold neutrons) energy level modification in the gravitational field of slowly rotating gravitating object in the Hořava–Lifshitz gravity.

A Sagnac type experiment is analyzed in the most well-known (2+1)-dimensional Bañados, Teitelboim and Zanelli (BTZ) spacetime and discussed vis-a-vis corresponding results in (3+1)-dimensional spacetime. The angular velocity of locally non-rotating observer has formally been predicted using Sagnac effect. Occurrence of arbitrarily large Sagnac delay (SD) for geodesic motion is observed for extreme BTZ black hole universally as its remarkable feature.

The simultaneity framework describes the relativistic interaction of time with space. The two major proposed simultaneity frameworks are differential simultaneity, in which time is offset with distance in “moving” or rotating frames for each “stationary” observer, and absolute simultaneity, in which time is not offset with distance. We use the Mansouri and Sexl test theory to analyze the simultaneity framework in rotating frames in the absence of spacetime curvature. The Mansouri and Sexl test theory has four parameters. Three parameters describe relativistic effects. The fourth parameter, $𝜖(v)$, was described as a convention on clock synchronization. We show that $𝜖(v)$ is not a convention, but is instead a descriptor of the simultaneity framework whose value can be determined from the extent of anisotropy in the unidirectional one-way speed of light. In rotating frames, one-way light speed anisotropy is described by the Sagnac effect equation. We show that four published Sagnac equations form a relativistic series based on relativistic kinematics and simultaneity framework. Only the conventional Sagnac effect equation, and its associated isotropic two-way speed of light, is found to match high-resolution optical data. Using the conventional Sagnac effect equation, we show that $𝜖(v)$ has a null value in rotating frames, which implies absolute simultaneity. Introducing the empirical Mansouri and Sexl parameter values into the test theory equations generates the rotational form of the absolute Lorentz transformation, implying that this transformation accurately describes rotational relativistic effects.

We investigate the effects of conformal gravity as a phase shift by quantum interference and alternate approach of Sagnac effect which is based on the anisotropy of the coordinate speed of light in the fourth-order theory of conformal Weyl space–time. In the nonrelativistic approximation, it has been shown that the phase shift of the interfering particle in neutron interferometer includes the potential terms with the Weyl parameter of the conformal fourth-order theory. Comparing the results of the measurement of the gravitational redshift by the interferometer in the gravitational field of the earth with our theoretical prediction, it has been obtained upper limit for the Weyl parameter as $\gamma \le 2\cdot 10^{-20}{\mathrm{\text{cm}}}^{-1}$.

The role of preferred frames for light propagation and time dilation in the region of a massive, spherical, gravitating bodies, where according to general relativity, space–time curvature is described by the Schwarzschild metric equation, is discussed in the context of the Sagnac effect (for light propagation) and the Hafele–Keating experiment (for time dilation). Predictions for both translational and rotational motion relative to the preferred frame are calculated up to order ${(v/c)}^3$. Different published theoretical calculations of the Sagnac effect are critically reviewed. The conflation in the literature of measured time differences in Sagnac experiments (a classical order $v/c$ effect) and time dilation (a relativistic order ${(v/c)}^2$ effect) are also discussed.

The Sagnac effect of exciton polaritons is discussed and the rotational phase shift is calculated. This phase shift shows a crossover between the optical and matter-wave behaviors in a small region around the energy level of the exciton. For typical semiconductor GaAs, we point out that a large rotational sensitivity and a moderate optical component in the polariton can be obtained simultaneously. The potential exciton polariton interferometer is also suggested.

In this research, the angular rotation speed in a passive photonic gyroscope based on the combination of side nanoring resonators and compensating waveguides has been analyzed by creating nonlinear effects in the control factors of the rings using the Sagnac effect. This structure consists of a central waveguide, two identical square resonators, and an almost U-shaped waveguide. The U-shaped waveguide causes coupling between the two resonators in a counterclockwise (CCW) mode. In this structure, a phase shift has been created in the output from the interference of two clockwise (CW) and CCW waves inside the resonators, and according to this phase shift and the central wavelength, the angular rotation speed has been estimated. In the proposed design of the gyroscope, by managing the nonlinear effects in the radius and refractive index (RI) of the coupling and inner rods, we have been able to control the changes in power, phase, and wavelength of the output from the device. With the increase in the intensity of power, the output power has an increasing slope at first, and at the point of creating a nonlinear effect in the sensor, the output power slope decreases. Also, this nonlinear effect directly affects the output phase of the structure. The maximum angular rotation speed in this gyroscope was $6.68\times 10^8{}^{\circ }$/s. By changing the RI of the inner rods from 3.2 to 3.7, the maximum output-to-input power ratio changes from 0.38 W/$\mu$m² to 0.75 W/$\mu$m². By changing the radius of the coupling rods from 93 nm to 97 nm, the maximum power ratio decreases from 0.78 W/$\mu$m² to 0.55 W/$\mu$m². The field distribution profile and photonic bandgap in this gyroscope have been analyzed using the finite-difference time-domain (FDTD) and plane-wave expansion (PWE) methods, respectively. Also, the gyroscope has a footprint of 163.5 $\mu$m².

Gyroscopes IN General Relativity (GINGER) is a proposal of an Earth-base experiment to measure the Lense–Thirring effect. GINGER uses an array of ring lasers, which are the most sensitive inertial sensors to measure the rotation rate of the Earth. GINGER is based on a three-dimensional array of large size ring lasers, able to measure the de Sitter and Lense–Thirring effects. The instrument will be located in the INFN Gran Sasso underground laboratory, in Italy. We describe preliminary developments and measurements. Earlier prototypes based in Italy, GP2, GINGERino, and G-LAS are also described and their preliminary results reported.

This paper proposes a strategy for detecting the presence of a gravito-magnetic field due to the rotation of the galactic dark halo. Visible matter in galaxies rotates and dark matter, supposed to form a halo incorporating baryonic matter, rotates also, since it interacts gravitationally with the rest. Pursuing the same line of reasoning, dark matter should produce all gravitational effects predicted by general relativity, including a gravito-magnetic field. I discuss a possible strategy for measuring that field. The idea recovers the old Sagnac effect and proposes to use a triangle having three Lagrange points of the Sun–Earth pair at its vertices. The asymmetry in the times of flight along the loop in opposite directions is proportional to the gravito-magnetic galactic field.

The scalar–tensor–vector–gravity (STVG), a prototype of modified gravity developed by Moffat, can correctly explain galaxy rotation curves, cluster dynamics, Bullet Cluster phenomena and cosmological data without invoking the observationally elusive general relativistic (GR) dark matter. Further, recent observations of neutron star masses are shown to defy some GR predictions, whereas STVG turns out to be more consistent with those observations. These successes indicate that STVG could be a potential candidate for a new theory of gravity. However, an important question concerns the possible range of values of the STVG dimensionless parameter $\alpha$ imposed by various physical scenarios. In the literature, the range $0.03<\alpha <2.47$ corresponding to different central source masses has been suggested. We show here that the $\alpha$ can be considerably constrained into the range $0<\alpha <10^{-5}$ assuming that the updated GPS fluctuation does not exceed the $\alpha$-dependent correction to the terrestrial Sagnac delay.

In this paper, some analogies between the Shapiro effect in the solar gravitational field and the Sagnac phase shift have been found. Starting from Einstein equivalence principle (EEP), which states the equivalence between the gravitational force and the pseudo-force experienced by an observer in a noninertial frame of reference, we imagine an observer on a rotating platform immersed in a gravitational field. In the Shapiro effect, for example, we know that the speed of an electromagnetic signal, calculated from the Earth, is less than $c$, but, if we calculate the speed using a clock at rest in the solar gravitational field, where the photon is passing, we get that the speed of light is $c$. Similarly, by considering the fictitious gravitational field of the rotating platform, if we look for a clock with respect to which the signal speed is $c$, we can interpret the time delay as a gravitational effect.

The Lagrange points of the Sun/Earth pair form an interesting reference frame corotating with the Earth around the barycenter of the pair. Here we propose to use them as a base for a “rigid” physical loop allowing for the propagation of electromagnetic signals along a closed contour. If a gravito-magnetic field is concatenated with the loop, it produces an asymmetry of the times of flight in opposite directions, just as for the classical Sagnac effect. Due to the large scale of the loop, an experiment based on these premises could allow for a measurement of the angular momentum of the Sun and also the detection of the angular momentum of the dark halo of the Milky Way, if it exists.

Ring laser Gyroscopes (RLG) are very versatile devices that find application in many fields as navigation, seismology and geophysics. Moreover, thanks to their sensitivity and accuracy, in the last years they have been used in fundamental physics research field.

GINGER (Gyroscopes IN GEneral Relativity) research group aims to exploit a large RLG to test general relativity theory. Our research team has two working RLG, both with a square shape, one installed in Pisa and named GP2. (1.6 m side), and the other installed in the INFN underground laboratory of Gran Sasso near L’Aquila named GINGERINO (3.6 m side). The final goal of GINGER is to measure the Earth rotation rate with enough precision to take into consideration general relativity predicted corrections.

To reach this target, one of the requirements is the stability of the laser and the optical cavity of the RLG. We will show the last developed techniques aimed to satisfy this stability requirement. Working on GP2 we have tested two different techniques to control the ring shape. One is based on the stabilization of the two Fabry-Pèrot resonators formed along the square diagonals by the opposite mirrors of the RLG. The other, consist in controlling the ring perimeter by monitoring its free spectral range through a beet-note between one of the counterpropagating beams and a frequency stabilized laser source. We will show the characteristics, the potentialities and the tests of these two methods.

We present here the proposal to use the LISA interferometer for detecting the gravitomagnetic field due to the rotation of the Milky Way, including the contribution given by the dark matter halo. The galactic signal would be superposed to the gravitomagnetic field of the Sun. The technique to be used is based on the asymmetric propagation of light along the closed contour of the space interferometer (Sagnac-like approach). Both principle and practical aspects of the proposed experiment are discussed. The strategy for disentangling the sought for signal from the kinematic terms due to proper rotation and orbital motion is based on the time modulation of the time of flight asymmetry. Such modulation will be originated by the annual oscillation of the plane of the interferometer with respect to the galactic plane. Also the effect of the gravitomagnetic field on the polarization of the electromagnetic signals is presented as an in principle detectable phenomenon.

In the main article [CQG 38 (2021) 055003], a new “canonical” form for the Lewis metrics of the Weyl class has been obtained, depending only on three parameters — Komar mass and angular momentum per unit length, plus the angle deficit — corresponding to a coordinate system fixed to the “distant stars” and an everywhere timelike Killing vector field. Such form evinces the local but non-global static character of the spacetime, and striking parallelisms with the electromagnetic analogue. We discuss here its generality, main physical features and important limits (the Levi-Civita static cylinder, and spinning cosmic strings). We contrast it on geometric and physical grounds with the Kerr spacetime — as an example of a metric which is locally non-static.

Relativity Theory (RT) incorporates serious inconsistencies:- (1) embracing the function of transverse e.m. (TEM) waves as perfect messengers but denying the presence of a Maxwell’s equations aether lest it might invalidate that perfection, despite it being essential for their existence; (2) assuming the physical absurdity that the external physical properties (mass, magnetic moment) of fundamental particles can be developed in zero volume (“spatially infinitesimal singularities”), despite powerful evidence that they are of finite size. It thereby overlooks that if two electromagnetically defined objects are of finite size the force communication between them is progressively velocity-limited, falling to zero at c [Heaviside 1889]. So this is what happens in electromagnetic accelerators, not massincrease. For more than a century these defects have hampered progress in understanding the physics of the mass property of particles, thus compelling it to be regarded as ‘intrinsic’ to those specific infinitesimal points in space. A rewarding substitute, Continuum Theory (CT), outlined here, (A) implements Maxwell’s aether as a massless all-pervasive quasi-superfluid elastic continuum of (negative) electric charge, and (B) follows others [Clerk Maxwell, both Thompsons, Larmor, Milner] in seeing mass-bearing fundamental particles as vortical constructs of aether in motion, not as dichotomously different from it. To encompass that motion, these cannot be infinitesimal singularities. Electron-positron scattering provides guidance as to that size. For oppositely-charged particles, one sort contains more aether and the other less, so particle-pair creation is ‘easy’, and abundantly observed, but has been attributed to ‘finding’. This electron-positron relationship defines mean aether density as >1030 coulomb.cm-3, thus constituting the near-irrotational reference frame of our directional devices. Its inherent self-repulsion also offers an unfathomable force capability should the means for displacing its local density exist; that, we show, is the nature of gravitational action and brings gravitation into the electromagnetic family of forces. Under (B) the particle mass is measured by the aether-sucking capability of its vortex, positiveonly gravitation being because the outward-diminishing force developed by each makes mutual convergence at any given point the statistically prevalent expectation. This activity maintains a radial aether (charge) density gradient - the Gravity-Electric (G-E) Field - around and within any gravitationally retained assemblage. So Newton’s is an incomplete description of gravitation; the corresponding G-E field is an inseparable facet of the action. The effect on c of that charge density gradient yields gravitational lensing. We find that G-E field action on plasma is astronomically ubiquitous. This strictly radial outward force on ions has the property of increasing the orbital angular momentum of material, by moving it outwards, but at constant tangential velocity. Spiral galaxies no longer require Cold Dark Matter (CDM) to explain this. The force (maybe 30 V.m-1 at solar surface) has comprehensive relevance to the high orbital a.m. achieved during solar planet formation, to their prograde spins and to exoplanet observations. The growth of high-mass stars is impossible if radiation pressure rules, whereas G-E field repulsion is low during dust-opaque infall, driving their prodigious mass loss rates when infall ceases and the star establishes an ionized environment. Its biggest force-effect (~1012 V.m-1) is developed at neutron stars, where it is likely the force of supernova explosions, and leads to a fertile model for pulsars and the acceleration of 1019 eV extreme-energy cosmic rays. Our only directly observed measure of the G-E field is recorded at about 1 V.m-1 in the ionosphere-to-Earth electric potential. And temporary local changes of ionosphere electron density, monitored by radio and satellite, have been discovered to act as earthquake precursors, presumably, we suggest, by recording change of G-E field and gravitational potential at Earth surface when its elastic deformation occurs, even when this is deep below electrically conducting ocean water. The paper concludes by noting experimental evidence of the irrelevance of the Lorentz transformations in CT and with a discussion of CT’s competence in such matters as perihelion advance and Sagnac effect, widely regarded as exclusively RT attributes. Finally we broach the notion that the aether is the site of inertia. This could explain the established equality of gravitational and inertial masses. In an accompanying paper we explore the cosmological and other aspects of ‘making particles out of aether’. This link undermines the expectation of fully distinct dynamical behaviour by particles and aether which motivated the Michelson-Morley experiment.

GINGER is a proposal for a new experiment aimed to the detection of the gravito-magnetic Lense-Thirring effect at the surface of the Earth. A three-dimensional set of ring lasers will be mounted on a rigid “monument”. In a ring laser a light beam traveling counterclockwise is superposed to another beam traveling in the opposite sense. The anisotropy in the propagation leads to standing waves with slightly different frequencies in the two directions; the resulting beat frequency is proportional to the absolute rotation rate in space, including the gravito-magnetic drag. The experiment is planned to be built in the Gran Sasso National Laboratories in Italy and is based on an international collaboration among four Italian groups, the Technische Universität München and the University of Canterbury in Christchurch (NZ).