Source Of Gravity Research Articles

Magnetized Black Holes: Interplay between Charge and Rotation

Already in the cornerstone works on astrophysical black holes published as early as in the 1970s, Ruffini and collaborators have revealed the potential importance of an intricate interaction between the effects of strong gravitational and electromagnetic fields. Close to the event horizon of the black hole, magnetic and electric lines of force become distorted and dragged even in a purely electro-vacuum system. Moreover, as the plasma effects inevitably arise in any astrophysically realistic environment, particles of different electric charges can separate from each other, become accelerated away from the black hole or accreted onto it, and contribute to the net electric charge of the black hole. From the point of principle, the case of super-strong magnetic fields is of particular interest, as the electromagnetic field can act as a source of gravity and influence spacetime geometry. In a brief celebratory note, we revisit aspects of rotation and charge within the framework of exact (asymptotically non-flat) solutions of mutually coupled Einstein–Maxwell equations that describe magnetized, rotating black holes.

Can the Present-Day Cosmology Really Make the Universe Understandable as a Sheer Physical System Operating as it must?

The modern and present day cosmology starts from the main idea, that our universe had one common begin in the so-called "Big-Bang", and that the traces of this begin can be clearly extrapolated from the presently observable cosmic facts, which still now can be found in the universe. In addition one assumes, based on the "cosmologic principle" that no space point in this universe is privileged with respect to any others, rather this universe in its energy depositions and physical conditionings represents itself as a totally homogeneous building in which everywhere happens the same, i.e. for all space points the past, the presence and the future are identical in this universe - at least when studied on reasonably large space- and time- dimensions and when studied on such "reasonable" dimensions it is subject to a common and ubiquitously identical evolution, bringing up the same future simultaneously at all of its places [1-3]. In this article here, we shall subject this standard cosmologic view to an extended critical exam in order to expose its rational weaknesses and intellectual impudence’s. It will be shown that the upcoming fate of the present universe strongly depends on its present internal Hubble expansion dynamics and its internal cosmic ingredients, which influence this expansion dynamics. Amongst these latter ingredients, one finds the mass content of the universe which by its gravitational attraction decelerates the cosmic expansion, and its opponent, the vacuum energy, that is seen as an enigmatic physical phenomenon which accelerates the cosmic expansion. We will show, however, that both these obviously essential cosmic ingredients are only poorly understood. Especially this concerns the mysterious vacuum energy of which we demonstrate that acceleration of cosmic dynamics can only be connected with pressure, but if vacuum pressure accelerates the expansion of the universe and so does perform thermodynamic work, it then cannot be constant as once proposed by Einstein and thus as such taken for granted by [4]. In addition, the internal cosmic gravity as we show is only poorly understood especially what concerns the source of this internal gravity, which usually is ascribed to the mass content of the universe connected with the mean cosmic mass density. Just this latter quantity, however, is a highly problematic physical quantity as we intensively demonstrate in this article. Taking everything together it is therefore hard to feel safe in this "explained universe" which cosmologists presently are offering to the community as their understanding of how this cosmos works

Thermal instability analysis in magneto-hybrid nanofluid layer between rough surfaces with variable gravity and space-dependent heat source

The onset of thermal instability with hybrid nanoparticles Al2O3–Cu in nanofluid is investigated with the combined effects of variable gravity, variable heat source and Lorentz force in a porous medium. Its applications are in many areas like chemical engineering, geophysics, astrophysics, etc. Based on literature, many gravity variations are assumed in the present analysis, along with a space-dependent heat source/sink parameter that varies along the width of the channel. The finite difference-based Lobatto IIIa method has been applied to solve the system under no nanoparticle flux and rough boundary conditions, and approximate analytical results are generated for some special cases. The roughness parameters ([Formula: see text]), Darcy number (Da), gravity variation function ([Formula: see text]), and Chandrasekhar number (Q) delay the onset of convection and thus stabilize the system. It is also observed that an increase in the Lewis number Le, power index in variable heat source, and the nanoparticle Rayleigh concentration number Rn decreases the critical Rayleigh number [Formula: see text] which destabilizes the system, and increases the critical wave number, which enlarges the convection cell size. In the case of exponential variation ([Formula: see text]) in the gravity variation parameter, the system becomes stabilized due to a delay in the onset of convection. In addition, we have considered multilayer perceptron-artificial neural network (MLP-ANN) computation to predict the critical Rayleigh number as per function of important controlling parameters. The data set of 625 observations is chosen keeping 70% for testing, 15% for training and 15% for validation using efficient Levenberg−Marquardt back propagation algorithm with optimal accuracy measures i.e., root mean square deviation (RMSE), root mean relative error (RMRE) and [Formula: see text] (coefficient of determination). Finally, the regression plots are drawn that correlate, target and output data.

Precession of bounded orbits and shadow in quantum black hole spacetime

The geodesics around compact objects are one of the best tools to understand the geometrical properties of the central gravity source. In this paper, we study timelike and lightlike geodesics of a quantum black hole proposed in [E. Binetti et al., Phys. Rev. D 106, 046006 (2022).], which does not require committing to a specific model of quantum gravity. We analyze the quantum correction on the related obsrevables: periapsis precession of bounded orbits and angular shadow size. We find that, compared to the classical case, the quantum correction will enhance the periapsis precession as well as the black hole shadow. This effect is more significant for a smaller quantum black hole.

Космологическая модель с квантовым туннелированием

The cosmological model with expansion and rotation with Bianchi type II metric is constructed within the framework of general relativity. The source of gravity of the model is an accompanying aniso-tropic fluid. The Wheeler–DeWitt equation is derived. The possibility of minisuperdimensional quantization of the model is considered. The tunneling wave function and the tunneling coefficient are found.

A Well-Balanced HLL Scheme for Hyperbolic Conservation Systems With Source Terms

This paper presents new finite volume schemes for hyperbolic conservation system with source terms. The classical finite volume schemes could not accurately simulate the dynamic problems caused by the balance between flux term and source terms. In order to deal with this problem, an approximate Riemann solver with source terms was designed in accordance with the classical HLL approximation Riemann solver. The well-balanced HLL schemes (WB-HLL) was obtained by modifying the flux calculation schemes for one-dimensional Euler equations and ideal MHD with gravity source terms, and a proof for well-balanced property of the new schemes has been presented.Two numerical examples of one-dimensional Euler equation and ideal MHD demonstrated that the WB-HLL scheme has higher accuracy and faster convergence than the classical HLL.

Bouguer Anomaly Re-Reduction and Interpretative Remarks of the Phlegraean Fields Caldera Structures (Southern Italy)

Phlegraean Fields is a large, active caldera located in the densely populated westernmost sector of Naples’s Bay (Southern Italy). Several Bouguer anomaly surveys are available for this area with different resolution and accuracy; gravity data derive from the integration of stations placed below and above the sea level as the caldera develops both onshore and offshore. The comparison of these maps with the Digital Elevation Model shows a still remaining Terrain Effect hiding the shallower and deep caldera structure’s signal. This effect has an impact on the modelling of the gravity source’s depth and geometry. In this research, we apply a geologically constrained terrain correction method to the higher resolution Free Air dataset available for the study area to enhance the complete Bouguer reduction. The correlation analysis between the residual and the topography allows us to assess the quality of the outcomes. The results represent an improvement in the anomalies’ isolation and clearly show a continuous circular-like clustering of maxima related to the geometry of the caldera rim. The minima are associated with volcano-tectonic depression filled with pyroclastic and sediment. Furthermore, features alignments overlap the fault systems, along which the volcanic activity occurred.

Mapping the structural configuration of the western Gulf of Guinea using advanced gravity interpretation methods

The western Gulf of Guinea has important implications for seismic-hazard estimates of the adjoining sub-Sahara West Africa region because of the presence of four active transform faults, namely the St. Paul, Romanche, Chain and Charcot fault zones. A satellite gravity data analysis was performed over the western Gulf of Guinea to delineate the structural configuration of the area. Initially, the energy spectrum analysis was used to determine regional and residual gravity effects. Further, the advanced techniques such as the tilt angle of the gradient amplitude (TAHG), the improved horizontal tilt angle (ITDX), the enhanced gradient amplitude (EHGA), and the fast sigmoid-based edge detection filter (FSED) were applied to the residual gravimetric anomaly to extract lineaments of the western Gulf of Guinea. The major trend of the detected lineaments has an ENE-WSW direction and depths of the gravity sources range from 3.4 to 13 km corresponding to widespread altered basalt, breccia, serpentinized peridotite and minor gabbro. Our findings closely agree with known information but are also able to confirm the presence of various other structures. Our results thus provide a structural map that helps us to have a better understanding of the tectonic and structural framework of the western Gulf of Guinea.

Imaging the Volcanic Structures Beneath Gran Canaria Island Using New Gravity Data

AbstractFrom a new gravity data set that covers homogeneously the whole surface of Gran Canaria (Canary Islands, Spain) and marine gravity data in the nearest offshore, we have obtained a Bouguer anomaly gravity map of the island which improves the previous ones. Using these gravity anomalies, we have applied a gravity inversion approach to investigate the structures beneath the surface of Gran Canaria Island and derive a 3D gravity sources model. The geometry of structures with anomalous density values is constrained up to a depth of approximately 20,000 m below the sea level. The interpretation of the density model identified structures related to the different volcanic stages of Gran Canaria. Several deep‐rooted high‐density structures represent the intrusive bodies emplaced in the early formation of Gran Canaria and the magma plumbing system of the Miocene volcanic edifices. A low‐density body in the center of the island may be associated with the syenitic core of the felsic central volcanic edifice (Tejeda Caldera). Shallow low‐density structures identified fractures which acted as feeder dikes of monogenetic volcanoes during the rejuvenated stage. Finally, the NW‐SE rift, which is the most important volcano‐tectonic structure of Gran Canaria, has a characteristic gravimetric signature and represents a long‐lived extensional fracture zone that has controlled the volcanic activity at least since the Miocene.

Possibility of detecting the gravity of an object frozen in a spatial superposition by the Zeno effect

While quantum probes surely feel gravity, no source of gravity has been prepared in a delocalized quantum state yet. Two basic questions need to be addressed: how to delocalize a mass sufficiently large to generate detectable gravity; and, once that state has been prepared, how to fight localization by decoherence. We propose to fight decoherence by freezing the source in the desired state through the Zeno effect. Successful implementation can be verified by scattering a probe in the effective potential generated by the source. Besides putting forward the idea, we provide an estimation of the values of the parameters required for the proposal to be feasible. Overall, the proposal seems as challenging as other existing ones, although the specific challenges are different (e.g. no entanglement needs to be preserved or detected, but the Zeno freezing must be implemented).

Methods for Underwater Gravity Measurement Error Compensations Based on Correlation Analysis

The measurement of Earth’s gravitational field is important in geophysics, geodynamics, geodesy, oceanography, and space science. The ocean covers 71% of the earth’s surface; therefore, measuring the ocean’s gravitational field is crucial. Compared with shipborne gravimetry, underwater gravimetry near the seafloor is closer to gravity sources and can obtain short-wavelength gravity information that is useful for small-scale deposit detection and seawater intrusion monitoring. This article focuses on gravimetric errors caused by the poor dynamics of the carrier; an error compensation method for underwater gravimetry based on correlation analysis is proposed. By analyzing the error sources that affect the dynamics of the carrier, the relationship between the gravimetry error and impact factors related to the dynamics was established, and the model’s parameters were estimated by the least-squares fitting method. The experimental data show that this method can effectively compensate for gravimetric errors caused by carrier dynamics and provide the theoretical basis and algorithm model for underwater gravimetry in the bottom-tracking mode.

Passage of Cosmic Photons Over Stellar Limbs

In several preceding papers [1,2,3,4] we have discussed particle and photon propagations through cosmic gravity fields under the new aspect that gravitational field sources are seen by moving masses or photons under relativistically aberrated positions. This causes astonishing effects like the reduction of peculiar motions of stars or a permanent increase of redshifts of photons at their propagations through cosmic space with uniform matter distribution. In this paper here we shall, however, now study under the given new auspices of relativistically displaced gravity sources the passage of photons over the limbs of stellar surfaces and ask whether such photons not only thereby experience the well known and proven Einstein‘ían deflection, but may also be subject to a discrete, asymptotic energy loss which is related to the mass of the touched star and the impact distance of the photon from this star. We shall investigate here this effect and compare it with Einsteinìan expectations.

Effects of throughflow on thermosolutal penetrative convection in a fluid layer with variable gravity field

AbstractIn this study, the start of thermosolutal penetrative convection in a horizontal fluid layer heated and salted from below was investigated analytically and graphically in the presence of throughflow and changeable gravity field effects. The normal mode technique is used to test the system's stability properties. The mathematical expressions for stationary and oscillatory Rayleigh numbers are obtained as a function of the governing parameters. The analysis demonstrates that the vertical throughflow, gravity parameter, and heat source effect all have a considerable influence on the beginning of convective motion in double‐diffusive flow. The impacts of variable gravity, vertical throughflow, and heat source parameters, as well as other physical parameters such as Solutal Rayleigh numbers and Lewis numbers, on stationary and oscillatory convection, are studied and illustrated graphically, and some previously published results are recovered in the limiting cases.

Substructure detection reanalysed: dark perturber shown to be a line-of-sight halo

ABSTRACT Observations of structure at subgalactic scales are crucial for probing the properties of dark matter, which is the dominant source of gravity in the universe. It will become increasingly important for future surveys to distinguish between line-of-sight haloes and subhalos to avoid wrong inferences on the nature of dark matter. We reanalyse a subgalactic structure (in lens JVAS B1938 + 666) that has been previously found using the gravitational imaging technique in galaxy-galaxy lensing systems. This structure has been assumed to be a satellite in the halo of the main lens galaxy. We fit the redshift of the perturber of the system as a free parameter, using the multiplane thin-lens approximation, and find that the redshift of the perturber is $z_\mathrm{int} = 1.42^{+0.10}_{-0.15}$ (with a main lens redshift of z = 0.881). Our analysis indicates that this structure is more massive than the previous result by an order of magnitude. This constitutes the first dark perturber shown to be a line-of-sight halo with a gravitational lensing method.

Inversion of large-scale gravity data with application of VNet

SUMMARY Inversion of large-scale gravity data set is generally a challenging problem due to memory requirements and computational costs. In this study, based on VNet, we present an efficient strategy for the large-scale gravity inverse problem by simultaneously tackling several base-scale gravity data. We first construct a large number of base-scale geological models including gravity sources, with different shapes and dimensions, and also their forward model data sets. Then, the idea of semantic segmentation is used to train an inversion network. In the next step, a finite number of base-scale and similar size area of gravity data, clipped from the original large data set with a fixed stride, are fed into the trained network. Finally, the individual recovered models are combined to provide the inversion result for the whole subsurface area. The feasibility and effectiveness of the presented inversion algorithm are tested on a large-scale complicated synthetic model. The algorithm is, then, verified for the inversion of the gravity data set obtained over the Morro do Engenho complex in central Brazil.

Crustal configuration of the Naama and El Bayadh region of northwest Algeria: Inferences from gravity and magnetic analysis

Northwestern Algeria is located where the Saharan Atlas borders the Saharan Platform along the South Atlas Front. The origin of the South Atlas Front is controversial, thus a detailed gravity and magnetic analysis constrained by seismic reflection profiles and well data were conducted to determine the structural configuration of this region. A residual gravity anomaly map created using upward continuation and a reduced to the pole magnetic anomaly map indicated a series of northwest-trending maxima anomalies parallel to the Atlassic orogeny folds and faults and east-trending maxima within the Benoud foreland basin. These maxima mostly coincide with Paleozoic basement uplifts based on seismic reflection profiles. Depth analyses based on upward continuation, and two-dimensional forward modeling of the gravity and magnetic data indicated that the source of the maxima are mainly 5 km in depth with the magnetic sources being approximately 0.5 km deeper than the gravity sources. The gravity and magnetic models indicate that the source bodies are steep-sided and coincide with interpreted faults from the seismic reflection profiles. The maxima anomalies are mainly caused by basement uplifts instead of variations in density and/or magnetic susceptibility in the Paleozoic or older basement lithologies. The South Atlas Front and the Saharan Atlas on the central and eastern portions of Algeria is governed by a thin-skinned tectonics style involving the Mesozoic-Cenozoic sedimentary cover. While the western part was probably controlled by a mixed thin- and thick-skinned tectonic style with the reactivation of deeply rooted Triassic and Jurassic faults during Tertiary compressive events in the interpreted Paleozoic basement.Our gravity and magnetic models illustrate a crustal architecture model of the Paleozoic basement which is consistent with a north-dipping basement normal fault between less deformed Saharan Platform than the more deformed Atlassic domain. Such a crustal model aids in determining the nature of the Atlassic orogeny as geological and geophysical studies have been determining the variations of structural styles along its entire length.

DGP and DGP-like cosmologies from f(Q) actions

In this work we explore and test new formulations of cosmological scenarios in $f(Q)$ theories. In these settings, the nonmetricity scalar ($Q$) is the main source of gravity and Friedmann equations are modified to account for the associated degrees of freedom. This work focuses first on the derivation, and then theoretical and observational analysis of two such (new) exact cosmological models; they both display a nonstandard behavior in which an additional parameter encoding nonmetricity effects acts in the fashion of a screened cosmological constant. One of the new settings has the same background evolution as the well know DGP cosmological model, while the other resembles the former considerably, although its origin is purely phenomenological. We use the Markov Chain Montecarlo method combined with standard statistical techniques to perform observational astrophysical tests relying upon background data, specifically these are type Ia supernovae luminosities and direct Hubble data (from cosmic clocks), along with cosmic microwave background shift and baryon acoustic oscillations data. In addition, we compute some of the cosmographic parameters and other discriminators with the purpose of refining our knowledge about these models in the light of their theoretical and observational signatures, and this allows for a better comparison with the (concordance) $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ setup. We conclude that these scenarios do not show signatures indicating a departure from the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ behavior.

Local positioning system as a classic alternative to atomic navigation

A local positional system (LPS) is proposed, in which particles are launched at given velocities, and a sensor system measures the trajectory of the particles in the platform frame. These measurements allow us to restore the position and orientation of the platform in the frame of the rotating Earth, without solving navigation equations. When the platform velocity is known and if the platform orientation stays the same, the LPS technique allows a navigational accuracy of 100 $\mu$m per one hour to be achieved. In this case, the LPS technique is insensitive to the type of platform trajectory. If there are also velocimeters installed on the platform, then one can restore the platform velocity and angular rate of the platform rotation with respect to the Earth. Instead of navigational equations, it is necessary to obtain the classical trajectory of a particle in the field of a rotating gravity source. Taking into account the gravity-gradient, Coriolis, and centrifugal forces, the exact expression for this trajectory is derived, which can be widely used in atomic interferometry. A new iterative method for restoring the orientation of the platform without using gyroscopes is developed. The simulation allows us to determine the conditions under which the LPS navigation error per hour is approximately $10$ m.

(2+1)-dimensional black holes of Einstein\u2019s theory with Born\u2013Infeld type electrodynamic sources

A new family of (2+1)-dimensional black holes are investigated in the background of Born–Infeld type theories coupled to a Riemannian curved spacetime. We know that both the scale and dual invariances are violated for these nonlinear electromagnetic theories. In this set-up, first we consider a pure magnetic source in a model of exponential electrodynamics and find a magnetically charged (2+1)-dimensional black hole solution in terms of magnetic charge q and nonlinearity parameter beta . In the second case we consider a pure electric source of gravity in the framework of arcsin electrodynamics and derive the associated (2+1)-dimensional black hole solution in terms of electric charge Q and the parameter beta . The asymptotic behaviour of the solutions at infinity as well as at rrightarrow 0 in both the frameworks is discussed. The asymptotic expressions of curvature invariants in the case of exponential electrodynamics shows that there exists a finite value of curvature at the origin, while in arcsin electrodynamics, the corresponding asymptotic behaviour shows that there is a true curvature singularity at the centre of the charged object. Furthermore, thermodynamics of the resulting charged black holes within the context of both the models is studied. It is shown that the thermodynamic quantities corresponding to these objects satisfy the first law of black hole thermodynamics.

How are cosmic gravity fields seen by moving objects? can gravitons deny their origins?

We put the question, how gravitational fields are communicated to space, and how they are recognized in space by moving objects. The general answer given to this question in these days is that field quanta of the gravitational field, called gravitons, are responsible for the communication of such fields. This answer is taken serious here, and then consequently is put into serious doubts when studying several physically coherent consequences. We start by investigating the gravitational influence of cosmic mass associations on moving massive objects when hereby the effect of propagating gravity field quanta, i.e. the gravitons, communicating the position of gravity sources, is taken into account. It is shown that moving objects are affected by gravity sources from a relativistically displaced position, like stars are seen under an aberration angle compared to the true source position. The astonishing effect of that mislocation is that a moving object at its passage through the center of a centrally symmetric galactic mass association undergoes a permanent gravitational deceleration of its relative motion. Furtheron it is shown that under this new view the problem of a planetary object, orbiting a central mass like the sun, takes a non-Keplerian solution, because the orbiting planet permanently should lose orbital angular momentum, since it permanently experiences a gravitational force component antiparallel to its orbital motion. From that an orbital decay time can be derived which predicts that a terrestrial planet should have a spiralling-in period of only a few 104 years which, compared to the expected age of the Earth of about 4.5 Billion years, represents a big problem of understanding. In addition, in view of the presumed action of gravitons from an aberrated source position, this article studies the propagation of cosmic photons over the photospheric limbs of stars. We show that when the center of the gravity field acts from a relativistically displaced position, then no energy change of limb photons when again propagating to larger distances should occur - which does confirm Einstein‘s view - , but also no deflection from the original propagation direction of the photon should occur - which contradicts Einstein‘s derivations. In this article we do not yet offer a rational solution of these newly pinpointed problems, but we simply end with the recommendation to perhaps reinvestigate the theoretical concept of gravitons, thought as to be the quantum messengers of gravitational fields.