Weak Field Limit Research Articles

Cosserat elasticity as the weak-field limit of Einstein-Cartan relativity

Cosserat elasticity as the weak-field limit of Einstein-Cartan relativity

Born again

Born’s original 1933 theory of nonlinear electrodynamics (in contrast to the later Born-Infeld theory) is acausal for strong fields. We explore the issue of strong-field causality violation in families of theories containing Born and/or Born-Infeld, and many variants that have been previously proposed in contexts that include cosmology and black hole physics. Many of these variants are acausal and hence unphysical. A notable exception is the modified Born-Infeld theory with ModMax as its conformal weak-field limit.

Testing gravitational lensing effects by supermassive massive black holes with superstring theory metric: Astrophysical implications and EHT constraints

We investigate gravitational lensing, both strong and weak, induced by charged black holes within heterotic superstring theory – α′-corrected Reissner–Nordström (RN) black holes characterized by an additional parameter, denoted as α, in addition to mass M and charge Q. Our findings reveal that as the parameter α increases, various crucial parameters such as the unstable photon orbit radius rph, critical impact parameter uph, deflection angle αD(θ), and angular position θ∞ also increase. Concurrently, the angular separation s decreases, while the relative magnitude rmag increases with the growing value of α. Utilizing supermassive black holes (SMBH) Sgr A* and M87* as gravitational lenses, the deflection angle resulting from the α′-corrected RN black hole, in both strong and weak field limits, surpasses that of the RN black holes (α=0) and falls below that of Schwarzschild black holes (α=0, Q=0). For Sgr A*, the angular position θ∞ lies within (24.08, 26.38) μas, while for M87* it ranges from (18.23, 19.96) μas. Estimating the time delay between the first and second relativistic images using twenty supermassive galactic center black holes as lenses, we find, for instance, that the time delay for Sgr A* and M87*, with Q=0.5 and α=5, can reach approximately 9.81 min and 14835.6 min, respectively. Remarkably, the EHT results for Sgr A* impose more stringent limits on the parameter space of α′-corrected RN black holes compared to those established by the EHT results for M87*. Our analysis deduces that, within the 1σ region, a substantial portion of the parameter space for α′-corrected RN black holes aligns with the Event Horizon Telescope (EHT) results for M87* and Sgr A*, and that and one cannot rule out the possibility of that heterotic superstring theory’s α′-corrected RN black holes being strong candidates for astrophysical black holes.

Refracted Gravity Solutions from Small to Large Scales

If visible matter alone is present in the Universe, general relativity (GR) and its Newtonian weak field limit (WFL) cannot explain several pieces of evidence, from the largest to the smallest scales. The most investigated solution is the cosmological model Λ cold dark matter (ΛCDM), where GR is valid and two dark components are introduced, dark energy (DE) and dark matter (DM), to explain the ∼70% and ∼25% of the mass–energy budget of the Universe, respectively. An alternative approach is provided by modified gravity theories, where a departure of the gravity law from ΛCDM is assumed, and no dark components are included. This work presents refracted gravity (RG), a modified theory of gravity formulated in a classical way where the presence of DM is mimicked by a gravitational permittivity ϵ(ρ) monotonically increasing with the local mass density ρ, which causes the field lines to be refracted in small density environments. Specifically, the flatter the system the stronger the refraction effect and thus, the larger the mass discrepancy if interpreted in Newtonian gravity. RG presented several encouraging results in modelling the dynamics of disk and elliptical galaxies and the temperature profiles of the hot X-ray emitting gas in galaxy clusters and a covariant extension of the theory seems to be promising.

Weak gravitational lensing by multi-horizons black hole

We investigate the weak gravitational lensing caused by multi-horizon black hole (MHBH) on light. Using the Gauss-Bonnet theorem, which demonstrates that light bending is a topological and global phenomenon, we are able to deduce the deflection angle of light in the weak field limits. First, we use the Gauss-Bonnet theorem to estimate the Gaussian optical curvature and determine the MHBH deflection angle for spherically balanced spacetime. Further, we evaluate the deflection angle of light within the plasma medium framework. Likewise, the impact of plasma and the non-plasma medium clearly illustrate the dynamics of the deflection angle by multi-horizons black hole.

Deflection angle of light in an black hole with primary scalar hair geometry

Weak gravitational lensing of the primary scalar hair black hole is proposed within this work. We can figure out the deflection angle of light by applying the Gibbons and Werner approach with a primary scalar hair black hole. To do this, we compute the Gaussian curvature and find the deflection angle of the weak field limits by applying Gauss-Bonnet theorem. Furthermore, we compute the deflection angle of light when it comes across both plasma and non-plasma field. We also study how the deflection angle behaves graphically in both cases.

Short review of the main achievements of the scalar field, fuzzy, ultralight, wave, BEC dark matter model

The Scalar Field Dark Matter model has been known in various ways throughout its history; Fuzzy, BEC, Wave, Ultralight, Axion-like Dark Matter, etc. All of them consist in proposing that dark matter of the universe is a spinless field Φ that follows the Klein-Gordon (KG) equation of motion □Φ − dV/dΦ = 0, for a given scalar field potential V. The difference between different models is sometimes the choice of the scalar field potential V. In the literature we find that people usually work in the non-relativistic, weak-field limit of the Klein-Gordon equation, where it transforms into the Schrödinger equation and the Einstein equations into the Poisson equation, reducing the KG-Einstein system, to the Schrödinger-Poisson system. In this paper, we review some of the most interesting achievements of this model from the historical point of view and its comparison with observations, showing that this model could be the last answer to the question about the nature of dark matter in the universe.

GLADE: Gravitational Light-Bending Astrometry Dual-Satellite Experiment

Light bending is one of the classical tests of general relativity and is a crucial aspect to be taken into account for accurate assessments of photon propagation. In particular, high-precision astrometry can constrain theoretical models of gravitation in the weak field limit applicable to the Sun neighborhood. We propose a concept for experimental determination of the light deflection close to the Sun in the 10−7 to 10−8 range, in a modern rendition of the 1919 experiment by Dyson, Eddington and Davidson, using formation flying to generate an artificial long-lasting eclipse. The technology is going to be demonstrated by the forthcoming ESA mission PROBA3. The experimental setup includes two units separated by 150 m and aligned to the mm level: an occulter and a small telescope (0.3 m diameter) with an annular field of view covering a region 0∘.7 from the Sun. The design is compatible with a space weather payload, merging several instruments for observation of the solar corona and environment. We discuss the measurement conditions and the expected performance.

Weak gravitational lensing and fundamental frequencies of Einstein–Euler–Heisenberg black hole

This paper is suggested to analyze the gravitational weak lensing and fundamental frequencies in the framework of the Einstein–Euler–Heisenberg (EEH) black hole. We compute the deflection angle of light by the EEH black hole in weak field limits. Which represents that the bending of light is a global and topological effect. For this purpose, we deduce the Gaussian curvature and apply the Gauss–Bonnet theorem (GBT). Furthermore, we determine the deflection angle at which light is deflected by a plasma medium. We also look into how an EEH black hole behaves graphically in vacuum and plasma medium. Moreover, we study the fundamental frequencies with three different models of EEH black hole.

Gravitational waves in New General Relativity

The models of New General Relativity have recently got attention of research community, and there are some works studying their dynamical properties. The formal aspects of this investigation have been mostly restricted to the primary constraints in the Hamiltonian analysis. However, it is by far not enough for counting their degrees of freedom or judging whether they are any good and viable. In this paper we study linearised equations in vacuum around the trivial Minkowski tetrad. By taking the approach of cosmological perturbation theory we show that the numbers of primary constraints are very easily seen without any need of genuine Hamiltonian techniques, and give the full count of linearised degrees of freedom in the weak field limit of each and every version of New General Relativity without matter.

Confinement and nonlinear electrodynamics: Asymptotic Schwarzschild charged black hole

While most nonlinear electrodynamics (NED) models tend to Maxwell’s linear theory in the weak field regime, very recently a model of NED has been proposed in the context of heavy quark–antiquark confinement that gives the same limit in the strong field regime. This form of correction to Maxwell’s linear theory is shown to be applicable in such a confined system. In this model, the radial electric field of a point charge is described by E=qr2+ζqr which consists of a Coulomb term plus a term proportional to the NED parameter ζ. Here in this paper, we extend the previous study on the model and accordingly, first, present more on the properties of the model and then introduce the magnetic black hole solution obtained in the gravity coupled minimally to this NED. The solution due to the unique property of the NED is asymptotically Schwarzschild black hole. In addition to the thermodynamics of the black hole, we investigate the circular speed–radius curve of the hypothetical star orbiting the mentioned black hole. It is shown that again due to the correction of Maxwell’s theory in the weak field limit these curves are equivalent to the corresponding curves in the Schwarzschild black hole.

The open string pair production, its enhancement and the physics behind

Why adding a collinear magnetic field to the electric one on a D3 brane in a system of two parallel separated D3 branes can enhance the open string pair production? How is the open string pair production rate related to the QED ones in the weak field limit? We answer these questions and report the somehow expected but still remarkable relation between the weak field non-perturbative stringy rate and the corresponding QED ones in this letter.

Unveiling Coherent Control of Halomethane Dissociation Induced by a Single Strong Ultraviolet Pulse.

We present a theoretical investigation into the coherent control of photodissociation reactions in halomethanes, specifically focusing on CH2BrCl by manipulating the spectral phase of a single femtosecond laser pulse. We examine the photodissociation of CH2BrCl under an ultrashort pulse with a quadratic spectral phase and reveal the sensitivity of both the total dissociation probability and the resulting radical products (Br+CH2Cl and Cl+CH2Br) to chirp rates. To gain insights into the underlying mechanism, we calculate the population distributions of excited vibrational states in the ground electronic state, demonstrating the occurrence of resonance Raman scattering (RRS) in the strong-field limit regime. By utilizing chirped pulses, we show that this RRS phenomenon can be suppressed and even eliminated through quantum destructive interference. This highlights the high sensitivity of photodissociation into Cl+CH2Br to the spectral phase, showcasing a phenomenon that goes beyond the traditional one-photon photodissociation of isolated molecules in the weak-field limit regime. These findings emphasize the importance of coherent control in the exploration and utilization of photodissociation in polyatomic molecules, paving the way for new advancements in chemical physics and femtochemistry.

A phenomenological wobbling model for isolated pulsars and the braking index

ABSTRACT An isolated pulsar is a rotating neutron star possessing a very high magnetic dipole moment, thus providing a powerful radiating mechanism. These stars loose rotational energy E through various processes, including a plasma wind originating from a highly magnetized magnetosphere and the emission of magnetic dipole radiation (MDR). Such phenomena produce a time decreasing angular velocity Ω(t) of the pulsar that is usually quantified in terms of its braking index. Although these mechanisms are widely acknowledged as the primary drivers of the spin evolution of isolated pulsars, it is plausible that other contributing factors influencing this effect have yet to be comprehensively investigated. Most of young isolated pulsars present a braking index different from that given by the MDR and plasma wind processes. Working in the weak field (Newtonian) limit, we take in this work a step forward in describing the evolution of such a system by allowing the star’s shape to wobble around an ellipsoidal configuration as a backreaction effect produced by its rotational deceleration. It is assumed that an internal damping of the oscillations occurs, thus introducing another form of energy loss in the system, and this phenomenon may be related to the deviation of the braking index from the models based on $\dot{E} \sim -\Omega ^4$ predictions. Numerical calculations suggest that the average braking index for typical isolated pulsars can be thus explained by a simple phenomenological model.

Gravitational lensing effects of black hole with conformally coupled scalar hair

In this paper, we investigate the gravitational lensing effects in the weak and strong field limits of a static black hole with conformally coupled scalar field. In the weak field limit, with the use of Gauss–Bonnet theorem we calculate the deflection angle of the light. It is found that comparing to Schwarzschild and Reissner–Nordstro¨\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\ddot{\ ext {o}}$$\\end{document}m (RN) black holes in general relativity, the weak deflection angle can be enhanced/suppressed by the scalar hair. In the strong field limit, we first compute the light deflection angle via calculating the lensing coefficients, all of which increase as the values of electric and scalar charges increase. Then we evaluate the lensing observables in strong field regime by supposing the hairy black hole as the candidate of M87* and SgrA* supermassive black holes, respectively. We find that the scalar hair has significant influences on various observables. In particular, the lensing observables of the charged black hole with positive scalar hair and RN black hole have degeneracy, which will be broken by the case with negative scalar hair. Our theoretical findings imply that it is feasible to employ the gravitational lensing effects as a probe of Einstein–Maxwell theory with negative scalar field differentiating from general relativity, once the future astrophysical observation is precise enough.

Magnetic-field-induced splitting of Rydberg Electromagnetically Induced Transparency and Autler-Townes spectra in 87Rb vapor cell.

We theoretically and experimentally investigate the Rydberg electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting of 87Rb vapor under the combined influence of a magnetic field and a microwave field. In the presence of static magnetic field, the effect of the microwave field leads to the dressing and splitting of each mF state, resulting in multiple spectral peaks in the EIT-AT spectrum. A simplified analytical formula was developed to explain the EIT-AT spectrum in a static magnetic field, and the theoretical calculations agree qualitatively with experimental results. The Rydberg atom microwave electric field sensor performance was enhanced by making use of the splitting interval between the two maximum absolute mF states separated by the static magnetic field, which was attributed to the stronger Clebsch-Gordon coefficients between the extreme mF states and the frequency detuning of the microwave electric field under the static magnetic field. The traceable measurement limit of weak electric field by EIT-AT splitting method was extended by an order of magnitude, which is promising for precise microwave electric field measurement.

Gravitational lensing in a topologically charged Eddington-inspired Born–Infeld spacetime

In the present paper, we study several aspects of gravitational lensing caused by a topologically charged Monopole/Wormhole, both in the weak field limit and in the strong field limit. We calculate the light deflection and then use it to determine the observables, with which one can investigate the existence of these objects through observational tools. We emphasize that the presence of the topological charge produces changes in the observables in relation to the case of General Relativity Ellis–Bronnikov wormhole.

Flow of charge and heat in thermal QCD within the weak magnetic field limit: A Bhatnagar-Gross-Krook model approach

Flow of charge and heat in thermal QCD within the weak magnetic field limit: A Bhatnagar-Gross-Krook model approach

Second-order teleparallel gauge theory

In this work, we analyze second-order extensions of teleparallel theories of gravity as gauge theories for the translation group. We use Utiyama’s approach to gauge theories and show that it is possible to include second-order derivative terms in the Lagrangian of the gauge potential and preserve gauge invariance. Besides the usual field strength, a new object has to be introduced in order to preserve both gauge and diffeomorphism invariances. From this new object, we obtain a set of fourteen independent invariants which leads to equations that are linear in the fourth derivative of the tetrad field. We analyze a particular example with one of these invariants and evaluate the weak field limit, showing that the effective gravitational potential is a combination of Newton and Yukawa potentials.

High‐Frequency Gravitational Waves in Electromagnetic Waveguides

AbstractThe interaction between a very‐high‐frequency gravitational wave (VHFGW) and an electromagnetic wave (EMW) in a rectangular waveguide is discussed in the weak field limit. The background EMW is assumed to be initially in the TE10 mode along the waveguide. It is then shown that a VHFGW, having the same frequency and direction of propagation of the EMW, induces through the waveguide a TE mode with a frequency doubled when compared to the original EMW frequency. In that respect, the GW acts similar to a non‐linear medium, giving rise to a Second Harmonic Generation (SHG) effect.