Relativistic Theory Of Gravitation Research Articles

From high-energy physics to the relativistic theory of gravity

We give a brief review of the most important results on inclusive processes and the relativistic theory of gravity obtained by A. A. Logunov.

Connecting Newton’s G with the Rest of Physics—Modern Newtonian Gravitation Resolving the Problem of “Big G’s” Value

As a simplified, idealized understanding of a physical system the General Relativity model has been highly successful in its gravitational role. However, it fails to address the problem of sufficiently precise measurement of “Big G”, the Newtonian Gravitation Constant, and has failed to obtain connection of “Big G” to the rest of physics. Because “Big G” arises naturally from Newton’s treatment of gravitation, this paper elaborates the Modern Newtonian Model of Gravitation and through it resolves the problems of “Big G” at which General Relativity has failed. Specifically: The causes of the problems in measuring “Big G” are resolved, “Big G” is connected to the rest of physics, and a sufficiently precise value of “Big G” is obtained by calculation from other fundamental physical constants. The companion paper The Experimental Data Validation of Modern Newtonian Gravitation over General Relativity Gravitation, which is available in this journal, publishes the results of this paper’s “Part V—Testing the Hypothesis and the Derivation”.

A note on the mass origin in the relativistic theories of gravity

We investigate the most general Lagrangian in the Minkowski space for the symmetric tensor field of the second rank. Then, we apply the Higgs mechanism to provide the mass to the appropriate components.

RELATIVISTIC MEASUREMENTS FROM TIMING THE BINARY PULSAR PSR B1913+16

ABSTRACT We present relativistic analyses of 9257 measurements of times-of-arrival from the first binary pulsar, PSR B1913+16, acquired over the last 35 years. The determination of the “Keplerian” orbital elements plus two relativistic terms completely characterizes the binary system, aside from an unknown rotation about the line of sight, leading to a determination of the masses of the pulsar and its companion: 1.438 ± 0.001 M ☉ and 1.390 ± 0.001 M ☉, respectively. In addition, the complete system characterization allows for the creation of relativistic gravitation test by comparing measured and predicted sizes of various relativistic phenomena. We find that the ratio of the observed orbital period decrease caused by gravitational wave damping (corrected by a kinematic term) to the general relativistic prediction is 0.9983 ± 0.0016, thereby confirms the existence and strength of gravitational radiation as predicted by general relativity. For the first time in this system, we have also successfully measured the two parameters characterizing the Shapiro gravitational propagation delay, and found that their values are consistent with general relativistic predictions. For the first time in any system, we have also measured the relativistic shape correction to the elliptical orbit, δ θ , although its intrinsic value is obscured by currently unquantified pulsar emission beam aberration. We have also marginally measured the time derivative of the projected semimajor axis, which, when improved in combination with beam aberration modeling from geodetic precession observations, should ultimately constrain the pulsar’s moment of inertia.

Execution and other details for the space experiment proposed for theories of relativistic gravitation

Execution and other details for the space experiment proposed for theories of relativistic gravitation

Metric and connections in theories of gravity. The role of equivalence principle

Fundamental issues underlying gravitational physics and some of the shortcomings of Einstein’s general relativity (GR) are discussed. In particular, after taking into account the role of the two main objects of relativistic theories of gravity, i.e. the metric and the connection fields, we consider the possibility that they are not trivially related so that the geodesic structure and the causal structure of the spacetime could be disentangled, as supposed in the Palatini formulation of gravity. In this perspective, the equivalence principle (EP), in its weak and strong formulations, can play a fundamental role in discriminating among competing theories. The possibility of its violation at quantum level could open new perspectives in gravitational physics and in unification with other interactions. We shortly debate the possibility of EP measurements by ground-based and space experiments.

Spacetime Causal Structure and Dimension from Horismotic Relation

A reflexive relation on a set can be a starting point in defining the causal structure of a spacetime in General Relativity and other relativistic theories of gravity. If we identify this relation as the relation between lightlike separated events (the horismos relation), we can construct in a natural way the entire causal structure: causal and chronological relations, causal curves, and a topology. By imposing a simple additional condition, the structure gains a definite number of dimensions. This construction works with both continuous and discrete spacetimes. The dimensionality is obtained also in the discrete case, so this approach can be suited to prove the fundamental conjecture of causal sets. Other simple conditions lead to a differentiable manifold with a conformal structure (the metric up to a scaling factor) as in Lorentzian manifolds. This structure provides a simple and general reconstruction of the spacetime in relativistic theories of gravity, which normally requires topological structure, differential structure, and geometric structure (which decomposes in the conformal structure, giving the causal relations and the volume element). Motivations for such a reconstruction come from relativistic theories of gravity, where the conformal structure is important, from the problem of singularities, and from Quantum Gravity, where various discretization methods are pursued, particularly in the causal sets approach.

Some properties of the dynamics of collapse in massive and massless relativistic theories of gravity

We investigate the dynamics of collapse in massive and massless relativistic theories of gravity for different equations of state for matter numerically and analytically. This allows clarifying the character of the collapse dynamics in the massive relativistic theory of gravity; in particular, we establish the graviton-mass dependence of the time of reaching the turning point (i.e., the point of transition from contraction to expansion). For the massless relativistic theory of gravity, we clarify the relation between the known general relativity solution for cold dust and the corresponding solution in the relativistic theory of gravity. We show that the harmonic time is singular, including the case of a smooth distribution of matter corresponding to a compact object with a strongly diffused boundary, which means that the Oppenheimer–Snyder solution cannot be fully embedded into the Minkowski space. We in addition investigate the effect of a nonzero pressure on the collapse dynamics.

The BepiColombo MORE gravimetry and rotation experiments with the orbit14 software

TheBepiColombomission toMercury is an ESA/JAXAcornerstonemission, consisting of two spacecraft in orbit around Mercury addressing several scientific issues. One spacecraft is the Mercury Planetary Orbiter, with full instrumentation to perform radio science experiments. Very precise radio tracking from Earth, on-board accelerometer and optical measurements will provide large data sets. From these it will be possible to study the global gravity field of Mercury and its tidal variations, its rotation state and the orbit of its centre of mass. With the gravity field and rotation state, it is possible to constrain the internal structure of the planet. With the orbit of Mercury, it is possible to constrain relativistic theories of gravitation. In order to assess that all the scientific goals are achievable with the required level of accuracy, full cycle numerical simulations of the radio science experiment have been performed. Simulated tracking, accelerometer and optical camera data have been generated, and a long list of variables including the spacecraft initial conditions, the accelerometer calibrations and the gravity field coefficients have been determined by a least-squares fit. The simulation results are encouraging: the experiments are feasible at the required level of accuracy provided that some critical terms in the accelerometer error are moderated. We will show that BepiColombo will be able to provide at least an order of magnitude improvement in the knowledge of Love number k2, libration amplitudes and obliquity, along with a gravity field determination up to degree 25 with a signal-to-noise ratio of 10.

Dark energy and graviton mass in the nearby universe

The problem of the local Hubble flow on scales of several Mpc induced by the dark energy realized by a scalar quintessence field is considered within the framework of relativistic gravity theory (RGT). The observational Hubble Space Telescope data are shown to be well described in RGT by a model similar to the Chernin–Baryshev–Teerikorpi model constructed in general relativity, with the local Hubble constant being smaller than the cosmological Hubble constant. A stringent constraint has been placed on the quintessence parameter, 0 ≤ ν ≤ 0.05.

Randers geometry as MOND/dark matter

We consider a deviation of the physical length from the Riemann geometry toward the Randers'. We construct a consistent second-order relativistic theory of gravity that dynamically reduces to the Einstein-Hilbert theory for the strong and Newtonian gravity while its weak gravitational regime reproduces MOND and the gravitational lensing attributed to the dark matter halo. It also naturally accommodates the observed value of the cosmological constant. We show that it predicts a few percent deviation for the post Newtonian parameter γ in a part of the regime that interpolates the Newtonian regime to the MOND regime. The deviation is consistent with the reported observations but can possibly be detected by fine-tuned refinements of the current data or specified future observations.

Signature of biased range in the non-dynamical Chern–Simons modified gravity and its measurements with satellite-satellite tracking missions: theoretical studies

Having great accuracy in the range and range rate measurements,he GRACE mission and the planed GRACE Follow On mission can in principle be employed to place strong constraints on certain relativistic gravitational theories. In this paper, we work out the range observable of the non-dynamical Chern-Simons modified gravity for the Satellite-to-Satellite Tracking (SST) measurements. We find out that a characteristic time accumulating range signal appears in non-dynamical Chern-Simons gravity, which has no analogue found in the standard parity-preserving metric theories of gravity. The magnitude of this Chern-Simons range signal will reach a few times of $\chi cm$ for each free flight of these SST missions, here $\chi$ is the dimensionless post-Newtonian parameter of the non-dynamical Chern-Simons theory. Therefore, with the 12 years data of the GRACE mission, one expects that the mass scale $M_{CS}=\frac{4\hbar c}{\chi a}$ of the non-dynamical Chern-Simons gravity could be constrained to be larger than $1.9\times10^{-9}eV$. For the GRACE FO mission that scheduled to be launched in 2017, the much stronger bound that $M_{CS}\geq5\times10^{-7}eV$ is expected.

Relativistic gravity and parity-violating nonrelativistic effective field theories

We show that the relativistic gravity theory can offer a framework to formulate the non-relativistic effective field theory in a general coordinate invariant way. We focus on the parity violating case in 2+1 dimensions which is particularly appropriate for the study on quantum Hall effects and chiral superfluids. We discuss how the non-relativistic spacetime structure emerges from relativistic gravity. We present covariant maps and constraints that relate the field contents in the two theories, which also serve as the holographic dictionary in context of gauge/gravity duality. A low energy effective action for fractional quantum Hall states is constructed, which captures universal geometric properties and generates non-universal corrections systematically. We give another holographic example with dyonic black brane background to calculate thermodynamic and transport properties of strongly coupled non-relativistic fluids in magnetic field. In particular, by identifying the shift function in the gravity as minus of guiding center velocity, we obtain the Hall viscosity with its relation to Landau orbital angular momentum density proportional to Wen-Zee shift. Our formalism has a good projection to lowest Landau level.

Alan Lightman’s Response to “Imagining the Future of Medicine” Commentary

Alan Lightman, is a novelist, essayist, physicist and educator, who from an early age, was entranced by both science and the arts. Lightman received his AB degree in physics from Princeton University in 1970, Phi Beta Kappa and magna cum laude, and his PhD in theoretical physics from the California Institute of Technology in 1974. Lightman’s essays, short fiction and reviews have appeared in the American Scholar, the Atlantic Monthly, Boston Review, Harper’s Magazine, Harvard Magazine, Nature, the New Yorker, the New York Review of Books, the New York Times and many more publications. He has lectured at more than 100 universities nationwide about the similarities and differences in the ways that scientists and artists view the world. In his scientific work, Lightman has made fundamental contributions to the theory of astrophysical processes under conditions of extreme temperatures and densities. In particular, his research has focused on relativistic gravitation theory, the structure and behavior of accretion disks, stellar dynamics, radiative processes and relativistic plasmas. He was the first professor at MIT to receive a joint appointment in the sciences and the humanities. Lightman is currently Professor of the Practice of the Humanities at the Massachusetts Institute of Technology (MIT).

Pulsars and gravity

Pulsars are wonderful gravitational probes. Their tiny size and stellar mass give their rotation periods a stability comparable to that of atomic frequency standards. This is especially true of the rapidly rotating "millisecond pulsars" (MSPs). Many of these rapidly rotating pulsars are in orbit with another star, allowing pulsar timing to probe relativistic perturbations to the orbital motion. Pulsars have provided the most stringent tests of theories of relativistic gravitation, especially in the strong-field regime, and have shown that Einstein's general theory of relativity is an accurate description of the observed motions. Many other gravitational theories are effectively ruled out or at least severely constrained by these results. MSPs can also be used to form a "Pulsar Timing Array" (PTA). PTAs are Galactic-scale interferometers that have the potential to directly detect nanohertz gravitational waves from astrophysical sources. Orbiting super-massive black holes in the cores of distant galaxies are the sources most likely to be detectable. Although no evidence for gravitational waves has yet been found in PTA data sets, the latest limits are seriously constraining current ideas on galaxy and black-hole evolution in the early universe.

Mach’s principle for cosmological solutions in relativistic theory of gravity

Mach’s principle in the relativistic theory of gravity (RTG) allows preliminarily selecting all possible solutions of the theory, including cosmological ones. It is shown that Mach’s principle in the RTG with massive gravitons admits only flat and open universe evolution scenarios, excluding the closed universe version. Unlike a standard cosmological solution in the RTG containing only a single free constant to be constrained from above by the causality principle, the most general flat scenario should have two parameters. It is shown that the second constant does not significantly affect realistic cosmological solutions. The open scenario for massless graviton theory is ruled out by the causality principle.

Effect of accumulation of a body’s excess internal energy as a result of gravitational compression in relativistic gravitational theory

Effect of accumulation of a body’s excess internal energy as a result of gravitational compression in relativistic gravitational theory

Outline of a dynamical inferential conception of the application of mathematics

We outline a framework for analyzing episodes from the history of science in which the application of mathematics plays a constitutive role in the conceptual development of empirical sciences. Our starting point is the inferential conception of the application of mathematics, recently advanced by Bueno and Colyvan (2011). We identify and discuss some systematic problems of this approach. We propose refinements of the inferential conception based on theoretical considerations and on the basis of a historical case study. We demonstrate the usefulness of the refined, dynamical inferential conception using the well-researched example of the genesis of general relativity. Specifically, we look at the collaboration of the physicist Einstein and the mathematician Grossmann in the years 1912–1913, which resulted in the jointly published “Outline of a Generalized Theory of Relativity and a Theory of Gravitation,” a precursor theory of the final theory of general relativity. In this episode, independently developed mathematical theories, the theory of differential invariants and the absolute differential calculus, were applied in the process of finding a relativistic theory of gravitation. The dynamical inferential conception not only provides a natural framework to describe and analyze this episode, but it also generates new questions and insights. We comment on the mathematical tradition on which Grossmann drew, and on his own contributions to mathematical theorizing. The dynamical inferential conception allows us to identify both the role of heuristics and of mathematical resources as well as the systematic role of problems and mistakes in the reconstruction of episodes of conceptual innovation and theory change.

MOND as the basis for an extended theory of gravity

This review describes why the geometric nature of space–time, the Einstein equivalence principle, and the geodesic motion of particles show the possibility of building an extended relativistic theory of gravity on regions where the Tully–Fisher law is valid. It is also shown how a metric construction of gravity can have a modified Newtonian dynamics behaviour compatible with the Tully–Fisher law and the bending of light observed in individual, groups, and clusters of galaxies. It is also reviewed how this metric theory of gravity fits reasonably well on cosmological scales explaining the current acceleration of the universe.

External gravitational field of a nonstatic spherically symmetric body in the relativistic theory of gravitation

We demonstrate that the external gravitational field of a nonstatic spherically symmetric body is static.