No Arabic abstract
According to this principle (EEP), in order that the local physical laws cannot change, after changes of velocity and potentials of a measuring system, the relativistic changes of any particle and any stationary radiation (like those used to measure it) must occur in identical proportion. Thus particles and stationary radiations must have the same general physical properties. In principle more exact and better defined physical laws for particles and their gravitational (G) fields can be derived from properties of particle models made up of radiation in stationary states after using fixed reference frames that dont change in the same way as the objects. Effectively, the new laws derived in this way do correspond with relativistic quantum mechanics and with all of the G tests. The main difference with current gravity is the linearity fixed by the EEP, i.e., the G field itself has not a real field energy to exchange with the bodies and it is not a secondary source of field. G work liberates energy confined in the models stationary states. The EEP also fixes a new astrophysical context that has fundamental differences with the current ones. This one has been presented in a separated work as a test for the EEP. The whole theory,including the new universe context fixed by the EEP, was published in a book.
Occurrence of spacetime singularities is one of the peculiar features of Einstein gravity, signalling limitation on probing short distances in spacetime. This alludes to the existence of a fundamental length scale in nature. On contrary, Heisenberg quantum uncertainty relation seems to allow for probing arbitrarily small length scales. To reconcile these two conflicting ideas in line with a well known framework of quantum gravity, several modifications of Heisenberg algebra have been proposed. However, it has been extensively argued that such a minimum length would introduce nonlocality in theories of quantum gravity. In this Letter, we analyze a previously proposed deformation of the Heisenberg algebra (i.e. $p rightarrow p (1 + lambda p^{-1})$) for a particle confined in a box subjected to a gravitational field. For the problem in hand, such deformation seems to yield an energy-dependent behavior of spacetime in a way consistent with gravitys rainbow, hence demonstrating a connection between non-locality and gravitys rainbow.
Theories of gravity that obey the Weak Equivalence Principle have the same Parametrised Post-Newtonian parameter $gamma$ for all particles at all energies. The large Shapiro time delays of extragalactic sources allow us to put tight constraints on differences in $gamma$ between photons of different frequencies from spectral lag data, since a non-zero $Delta gamma$ would result in a frequency-dependent arrival time. The majority of previous constraints have assumed that the Shapiro time delay is dominated by a few local massive objects, although this is a poor approximation for distant sources. In this work we consider the cosmological context of these sources by developing a source-by-source, Monte Carlo-based forward model for the Shapiro time delays by combining constrained realisations of the local density field using the BORG algorithm with unconstrained large-scale modes. Propagating uncertainties in the density field reconstruction and marginalising over an empirical model describing other contributions to the time delay, we use spectral lag data of Gamma Ray Bursts from the BATSE satellite to constrain $Delta gamma < 3.4 times 10^{-15}$ at $1 sigma$ confidence between photon energies of $25 {rm , keV}$ and $325 {rm , keV}$.
We investigate leading order deviations from general relativity that violate the Einstein equivalence principle in the gravitational standard model extension. We show that redshift experiments based on matter waves and clock comparisons are equivalent to one another. Consideration of torsion balance tests, along with matter wave, microwave, optical, and Mossbauer clock tests, yields comprehensive limits on spin-independent Einstein equivalence principle-violating standard model extension terms at the $10^{-6}$ level.
This work refers to the new formula for the superpotential Uikl in conservation laws in general relativity satisfying the integral and differential conservation laws within the Schwarzschild metric. The new superpotential is composed of two terms. The first term is based on Mollers concept and its a function of the metric gik and its first derivative only. The second term is the antisymmetric tensor density of weight plus one and it consists of higher derivatives of the metric gik. Although the new superpotential consists of higher derivatives of the metric gik it might bring a new evaluation of the conservative quantities in general relativity
Backgrounds are pervasive in almost every application of general relativity. Here we consider the Lagrangian formulation of general relativity for large perturbations with respect to a curved background spacetime. We show that Noethers theorem combined with Belinfantes symmetrization method applied to the group of displacements provide a conserved vector, a superpotential and a energy-momentum that are independent of any divergence added to the Hilbert Lagrangian of the perturbations. The energy-momentum is symmetrical and divergenceless only on backgrounds that are Einstein spaces in the sense of A.Z.Petrov.