Narrow Results

This paper uses two empirical tools to quantify the impact of tariff changes on bilateral trade and welfare. Both tools are rooted in structural gravity literature. The first tool estimates the impact of tariff changes on bilateral trade for 5,020 products in a partial equilibrium framework. The second tool quantifies the impact on bilateral aggregate trade in a general equilibrium setup, allowing estimates of trade diversion and welfare changes. These tools are used to estimate the impact of tariff changes on Armenia with regard to (i) its alignment with the external tariff of the Eurasian Economic Union; (ii) free trade agreements between the Eurasian Economic Union and other economies, including Iran and the People’s Republic of China; and (iii) Armenia’s loss of beneficiary status under the Generalised Scheme of Preferences of the European Union.

In this paper, we examine the correlation functions associated with intensity interferometry and gravito-optics of gravitational wave (GW) signals from compact binary coalescences (CBC). Previous theoretical studies of the gravito-optics of GWs have concentrated on the characterization of both the classical and the nonclassical properties of signals from cosmological sources in the early Universe. These previous works assume a periodic signal similar to the signals studied widely in optics and quantum optics and do not apply to transient signals. We develop the gravito-optics of intensity correlations for descriptions of the detection of transient signals from CBC and apply these methods to calculate the two-point intensity correlations for the GW discovery. We also discuss the necessary theoretical work required for the description of the quantum gravito-optics of intensity correlations in the detection of signals from binary inspirals.

The classical-quantum duality at the basis of quantum theory is here extended to the Planck scale domain. The classical/semiclassical gravity (G) domain is dual (in the precise sense of the classical-quantum duality) to the quantum (Q) elementary particle domain: $O_Q=o_P^2{O}_G^{-1}$, $o_P$ being the Planck scale. This duality is universal. From the gravity (G) and quantum (Q) variables $(O_G,O_Q)$, we define new quantum gravity (QG) variables $O_{\mathrm{\text{QG}}}=(1/2)(O_G+O_Q)$ which include all (classical, semiclassical and QG) domains passing through the Planck scale and the elementary particle domain. The QG variables are more complete than the usual ($O_Q$, $O_G$) ones which cover only one domain (Q or G). Two$O_G$ or $O_Q$ values $(\pm )$ are needed for each value of $O_{\mathrm{\text{QG}}}$ (reflecting the two dual ways of reaching the Planck scale). We perform the complete analytic extension of the QG variables through analytic (holomorphic) mappings which preserve the light-cone structure. This allows us to reveal the classical-quantum duality of the Schwarzschild–Kruskal spacetime: exterior regions are classical or semiclassical while the interior is totally quantum: its boundaries being the Planck scale. Exterior and interior lose their difference near the horizon: four Planck scale hyperbolae border the horizons as a quantum dressing or width: “l’horizon habillé”. QG variables are naturally invariant under $O_G\to O_Q$. Spacetime reflections, antipodal symmetry and PT or CPT symmetry are contained in the QG symmetry, which also shed insight on the global properties of the Kruskal manifold and its present renewed interest.

In this paper, we discussed the longitudinal harmonic waves reflection from a solid elastic half-space with electromagnetic and gravity fields influence, considering a fractional order via fractional exponential function method. The clarifications are required for the reflection amplitudes ratios (i.e. the ratios between the reflected waves amplitude and the incident waves amplitude). The results obtained were calculated analytically and displayed by graphs to show the physical meaning of the phenomenon. A comparison has been made between the fractional and integer derivatives. The results of this paper demonstrate the rigor and effectiveness of the considered fractional technique.

We develop the covariant formalism of the cosmological perturbation theory for the Brans-Dicke gravity, and use it to calculate the cosmic microwave background (CMB) anisotropy and large scale structure (LSS) power spectrum. We introduce a new parameter ζ which is related to the Brans-Dicke parameter ζ = ln(1/ω + 1), and use the Markov-Chain Monte Carlo (MCMC) method to explore the parameter space. Using the latest CMB data published by WMAP, ACBAR, CBI, Boomerang teams, and the LSS data from the SDSS survey DR4, we find that the the 2σ (95.5%) bound on ζ is about |ζ| > 10^-2, or |ω| > 10², the precise limit depends somewhat on the prior used.

On the basis of our recent modifications of the Dirac formalism we generalize the Bargmann-Wigner formalism for higher spins to be compatible with other formalisms for bosons and fermions. Connections with dual electrodynamics, with the Ogievetskii-Polubarinov notoph and the Weinberg 2(2S+1) theory are found. Next, we proceed to derive the equations for the symmetric tensor of the second rank on the basis of the Bargmann-Wigner formalism in a straightforward way. The symmetric multispinor of the fourth rank is used. It is constructed out of the Dirac 4-spinors. Due to serious problems with the interpretation of results we generalize the standard procedure and we obtain the spin-2 relativistic equations, which are consistent with the Einstein-Hilbert equation. We introduce the dual analogues of the Riemann tensor and we derive corresponding dynamical equations in the Minkowski space. Connections with the Marques-Spehler chiral gravity theory are discussed. The importance of the 4-vector field (and its gauge part) is pointed out. The spin-3/2 case is briefly discussed too.

The vierbein (tetrad) fields for closed and open Friedmann-Robertson-Walker cosmologies are hard to work out in most of the theories featuring absolute parallelism. The difficulty is traced in the fact that these theories are not invariant under local Lorentz transformations of the vierbein. We illustrate this issue in the framework of f(T) theories and Born-Infeld determinantal gravity. In particular, we show that the early Universe as described by the Born-Infeld scheme is singularity free and naturally inflationary as a consequence of the very nature of Born-Infeld gravitational action.

We consider some of the obstacles that will have to be overcome in order to perform a direct measurement of the gravitational free-fall of positronium atoms. Foremost among these are the production of positronium atoms in a cryogenic environment, efficient excitation of these atoms to suitably long-lived Rydberg states, and their subsequent control via the interaction of their large electric dipole moments with inhomogeneous electric fields. Recent developments in all of these areas can be directly applied to a positronium free-fall gravity measurement, making such an endeavour both timely and feasible.

A fundamental question in physics that has yet to be addressed experimentally is whether particles of antimatter, such as the antiproton or positron, obey the weak equivalence principle (WEP). Several theoretical arguments have been put forward arguing limits for possible violations of WEP. No direct `classical' gravitational experiment, the measurement of the free fall of an antiparticle, has been performed to date to determine if a particle of antimatter would experience a force in the gravitational potential of a normal matter body that is different from normal gravity. 30 years ago we proposed a free fall experiment using protons and antiprotons, modeled after the experiment to measure the gravitational acceleration of a free electron. At that time we gave consideration to yet another possible observation of gravitational differences between matter and antimatter based on the gravitational red shift of clocks. I will recall the original arguments and make a number of comments pertaining to the technical problems and other issues that prevented the execution of the antiproton free fall measurement. Note that a different gravitational force on antimatter in the gravitational field of matter would not constitute a violation of CPT, as this is only concerned with the gravitational acceleration of antimatter in the gravitational field of an antimatter body.

experiment's main goal is to measure the local gravitational acceleration of antihydrogen and thus perform a direct test of the weak equivalence principle with antimatter. In the first phase of the experiment the aim is to measure with 1% relative precision. This paper presents the antihydrogen production method and a description of some components of the experiment, which are necessary for the gravity measurement. Current status of the experimental apparatus is presented and recent commissioning results with antiprotons are outlined. In conclusion we discuss the short-term goals of the collaboration that will pave the way for the first gravity measurement in the near future.

The classical Weak Equivalence Principle has not yet been tested using antimatter in matter gravitational fields. The GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment, recently approved by CERN, proposes to measure the free-fall acceleration of antihydrogen. In this experiment, positive antihydrogen ions will be produced, and subsequently cooled down using laser cooled Be⁺ ions. Then, when a temperature of around 20 μK has been reached, the excess positron will be detached and the free-fall time will be measured using the antiproton annihilation products. An overview of the experiment will be given together with its present status.

In the GBAR experiment, cold antihydrogen atoms will be left to fall on an annihilation plate with the aim of measuring the gravitational acceleration of antimatter. Here, we study the quantum reflection of these antiatoms due to the Casimir-Polder potential above the plate. We give realistic estimates of the potential and quantum reflection amplitudes, taking into account the specificities of antihydrogen and the optical properties of the plate. We find that quantum reflection is enhanced for weaker potentials, for example above thin slabs, graphene and nanoporous media.

The motivation of the AEgIS experiment is to test the universality of free fall with antimatter. The goal is to reach a relative uncertainty of 1% for the measurement of the earth's gravitational acceleration on an antihydrogen beam. High vertex position resolution is required for a position detector. An emulsion based detector can measure the annihilation vertex of antihydrogen atoms with a resolution of 1-2 μm, which if realized in the actual experiment will enable a 1% measurement of with less than 1000 atoms. Developments and achievements on emulsion detectors for the AEgIS experiment are presented here.

In the early eighties, the development of ballistic absolute gravimeters based on laser interferometer opened the doors to new research areas in various scientific domains such as geodesy, geophysics or metrology. After a brief overview of the most used technique for gravity measurements, the implication of gravity in the context of an improved SI, especially for a new definition of the mass unit kg, will be presented.

We present a brief, and unfortunately incomplete, summary of the 2013 Workshop on Antimatter Gravity (WAG) held at Bern, Switzerland.

The interactions of hadron spin with gravity and electromagnetic field and their implication for hadron spin structure are considered. The extension of equivalence principle naturally leads to the closeness of vector meson magnetic moment to that of electroweak boson. This similarity is confirmed in the lattice QCD. The effective gravity in AdS/QCD allows to connect the $t$-dependence of GPDs (and therefore electromagnetic and gravitational form factors) with $k_T$-dependemce of TMDs. The possible cosmological implications of equivalence principle extension are discussed.

Searches for the role of spin in gravitation dated before the firm establishment of the electron spin in 1925. Since mass and spin, or helicity in the case of zero mass, are the Casimir invariants of the Poincaré group and mass participates in universal gravitation, these searches are natural steps to pursue. In this update, we report on the progress on this topic in the last five years after our last review. We begin with how is Lorentz/Poincaré group in local physics arisen from spacetime structure as seen by photon and matter through experiments/observations. The cosmic verification of the Galileo Equivalence Principle for photons/electromagnetic wave packets (Universality of Propagation in spacetime independent of photon energy and polarization, i.e. nonbirefringence) constrains the spacetime constitutive tensor to high precision to a core metric form with an axion degree and a dilaton degree of freedom. Hughes-Drever-type experiments then constrain this core metric to agree with the matter metric. Thus comes the metric with axion and dilation. In local physics this metric gives the Lorentz/Poincaré covariance. Constraints on axion and dilaton from polarized/unpolarized laboratory/astrophysical/cosmic experiments/observations are presented. In the end, we review the theoretical progress on the issue of gyrogravitational ratio for fundamental particles and the experimental progress on the measurements of possible long range/intermediate range spin-spin, spin-monopole and spin-cosmos interactions.

In this paper, a novel model in a nonlocal porous thermoelastic solid is formulated based on the dual-phase-lag model (DPL), the Lord–Shulman theory and coupled theory with a memory-dependent derivative. The Laplace–Fourier technique is used to solve the problem and to obtain the exact expressions of physical fields. Numerical calculation of temperature, displacement, change in the volume fraction and stress is carried out and displayed graphically. Comparisons are made with the results predicted in the absence and presence of the gravity field as well as a nonlocal parameter. Comparisons are also made with results for different memory Kernel.

The novelty of 21st-century physics is the development of the “superfluid quantum vacuum” model, also named “superfluid quantum space” that is replacing space-time as the fundamental arena of the universe. It also represents the model that has the potential of unifying four fundamental forces of the universe. Superfluid quantum space is represented as the time-invariant fundamental field of the universe where time is merely the duration of material changes.

Fascinated people from the dawn of history, gravity is not understood, still. Here, we suggest that gravity is a result of a process in the material: (1) Gravitational photons are produced by all atoms that exist in nonzero temperature and or interact with radiation, similar to black body radiation. (2) Then, these photons move in the material. The electromagnetic properties of the gravitational photons and the structure of the object cause the photons’ trajectories to bend. (3) Such trajectories generate a force pointing to the center of mass of the object, due to the circular motion and the electromagnetic properties of the gravitational photons. These trajectories are radiated outwards, as in antennae, although at a much slower rate, due to that force. So basically gravity is a simple process (as black body radiation), just a sort of generalized radiation pressure due to the process of gravity in the material, resulting in antenna like radiation emission, of these unique electromagnetic waves that are pressed towards the radiating object center of mass during their circular motion in the object. Going beyond the dynamical model, we identify various possible forms of the gravitational photons, and their general invariant properties. With this theory, we (1) explain various unexplained phenomena that are related to gravity, yet also suggest (2) method and apparatus for gravity shielding, and (3) gravitational radiation energy cultivation. This theory can form the missing part for the “theory of everything”.