Radiation Energy Research Articles

Strong noninertial radiative shifts in atomic spectra at low accelerations

Despite numerous proposals investigating various properties of accelerated detectors in different settings, detecting the Unruh effect remains challenging due to the typically weak signal at achievable accelerations. For an atom with frequency gap ω0, accelerated in free space, significant acceleration-induced modification of properties like transition rates and radiative energy shifts requires accelerations of the order of ω0c. In this paper, we make the case for a suitably modified density of field states to be complemented by a judicious selection of the system property to be monitored. We study the radiative energy-level shift in inertial and uniformly accelerated atoms coupled to a massless quantum scalar field inside a cylindrical cavity. Uniformly accelerated atoms experience thermal correlations in the inertial vacuum, and the radiative shifts are expected to respond accordingly. We show that the noninertial contribution to the energy shift can be isolated and significantly enhanced relative to the inertial contribution by suitably modifying the density of field modes inside a cylindrical cavity. Moreover, we demonstrate that monitoring the radiative energy shift, as compared to transition rates, allows us to reap a stronger purely noninertial signal. We find that a purely noninertial radiative shift as large as 50 times the inertial energy shift can be obtained at small, experimentally achievable accelerations (a∼10−9ω0c) if the cavity’s radius R is specified with a relative precision of δR/R0∼10−7. Given that radiative shifts for inertial atoms have already been measured with high accuracy, we argue that the radiative energy-level shift is a promising observable for detecting Unruh thermality with current technology. Published by the American Physical Society 2024

Impact of photobiomodulation therapy on pro-inflammation functionality of human peripheral blood mononuclear cells – a preliminary study

Research into the efficacy of photobiomodulation therapy (PBMT) in reducing inflammation has been ongoing for years, but standards for irradiation methodology still need to be developed. This study aimed to test whether PBMT stimulates in vitro human peripheral blood mononuclear cells (PBMCs) to synthesize pro-inflammatory cytokines, including chemokines. PBMCs were irradiated with laser radiation at two wavelengths simultaneously (λ = 808 nm in continuous emission and λ = 905 nm in pulsed emission). The laser radiation energy was dosed in one dose as a whole (5 J, 15 J, 20 J) or in a fractionated way (5 J + 15 J and 15 J + 5 J) with a frequency of 500, 1,500 and 2,000 Hz. The surface power densities were 177, 214 and 230 mW/cm2, respectively. A pro-inflammatory effect was observed at both the transcript and protein levels for IL-1β after PBMT at the energy doses 5 J and 20 J (ƒ=500 Hz) and only at the transcript level after application of PBMT at energy doses of 20 J (ƒ= 1,500; ƒ=2,000 Hz) and 5 + 15 J (ƒ=500 Hz). An increase in CCL2 and CCL3 mRNA expression was observed after PBMT at 5 + 15 J (ƒ=1,500 Hz) and 15 + 5 J (ƒ=2,000 Hz) and CCL3 concentration after application of an energy dose of 15 J (frequency of 500 Hz). Even though PBMT can induce mRNA synthesis and stimulate PBMCs to produce selected pro-inflammatory cytokines and chemokines, it is necessary to elucidate the impact of the simultaneous emission of two wavelengths on the inflammatory response mechanisms.

Vibration analysis of functionally graded saturated porous beams using radiative energy transfer method

An energy flow model based on the radiative energy transfer method (RETM) is established for the high-frequency response prediction of finite functionally graded saturated porous beams. The Timoshenko beam theory and the Biot thoery are applied to derive the motion governing equations of the beam. The response of the beam loaded by a high-frequency point force is described by vibrational energy density and intensity. The energy response of the beam is contributed by the rays emitted from the actual source set at load point and then reflected through the fictitious sources at the boundaries. Fictitious sources are determined by the energy balance equations at the boundaries. Numerical examples show that the energy distributions of the saturated porous beams are well predicted by the proposed approach.

Sound source characteristics of heat exchanger under flow conditions

Heat exchangers are the most important equipment in ship cooling system, which generate vibration and noise due to flow excitation during operation, affecting structural safety and having a significant impact on acoustic stealth performance. Mastering the characteristics of sound source has guiding significance for noise reduction design. The acoustic signal directly obtained from the hydrophone inside the pipe including reflected sound wave, which cannot accurately characterize the sound radiation energy from heat exchanger into pipe. In order to accurately evaluate the sound source characteristics of heat exchanger under flow conditions, experimental method was used to test the sound source characteristics of heat exchanger which are not affected by connected pipelines based on the two-port sound source theory. The main factors affecting the sound source characteristics of heat exchanger were analyzed, such as flow rate, background pressure, and temperature. The research can provide reference for the vibration and noise reduction design of heat exchangers.

Significant statistical model of heat transfer rate in radiative Carreau tri-hybrid nanofluid with entropy analysis using response surface methodology used in solar aircraft

The recent advancement of technologies focuses on the use of solar-based heat radiation and nanotechnology. The primary source of heat is solar energy, which is obtained by absorbing sunlight. In addition, solar thermal planes, photovoltaic cells, and sun-based hybrid nanofluids all help to harness solar energy. Therefore, main concern of the study is to explored the two-dimensional Engine oil-based Carreau tri-hybrid nanofluid (SiO2 (silica dioxide), MOS2 (Molybdenum disulfide), Fe3O4(black iron oxide)) flow via a stretching sheet within solar wings. The flow phenomena of the non-Newtonian fluid enrich for the effects of radiant energy and the external heat source. By adopting similarity transfiguration, the dimensional partial main flow equations are changed into nonlinear dimensionless ordinary differential equations. The most effective and powerful tool of the semi-analytical method ADM (Adomain Decomposition Method) is utilized to solve the nanofluid flow problem. The uniqueness of the proposed study arises due to the analysis of entropy generation obtained by various irreversibility processes. The graphical illustration of outcome of various governing parameters on velocity, temperature, entropy terms and engineering quantities have been presented and theoretically analyzed. The findings reveal that The Carreau ternary hybrid nanofluids enhance the system's thermal conductivity for optimal temperature regulation in solar aircraft and better heat dissipation. The use of Carreau ternary hybrid nanofluids significantly reduces entropy generation, which implies a more reversible process, enhancing the overall efficiency of the energy conversion systems in solar aircraft. The heat flow of the system is accurately reflected by the chosen variables and their interactions, as demonstrated by the constructed model's strong statistical significance. For real-world applications, this improves the model's predictability and dependability.

Comparison of methods for changing the spectrum of radiation of a pulse x-ray source to determine the most effective two-energy image processing

For detecting substances with similar chemical composition and density, one of the promising methods of non-destructive testing is dual-energy processing of X-ray images. In particular, dual-energy transformation algorithms can be used to search for minerals hidden within barren rock. This method is most effective when the conditions for registering X-ray images and energy levels are properly selected. This study compares the effectiveness of image processing using the dual-energy method for three cases of spectral composition variation: firstly, as a result of adjusting the voltage on the X-ray tube; secondly, by attenuating low-energy radiation through the use of a copper filter; and thirdly, by combining these two methods. Beryl particles embedded in ground muscovite are used as samples for detection. The study utilizes a pulsed X-ray radiation source that generates radiation pulses of nanosecond duration. An original high-voltage generator scheme has been implemented for the method of regulating radiation energy by changing the peak voltage on the X-ray tube. The use of X-ray sources of this type enables the acquisition of high-resolution X-ray images of moving objects.

Sifting the debris: Patterns in the SNR population with unsupervised ML methods

Context. Supernova remnants (SNRs) carry vast amounts of mechanical and radiative energy that heavily influence the structural, dynamical, and chemical evolution of galaxies. To this day, more than 300 SNRs have been discovered in the Milky Way, exhibiting a wide variety of observational features. However, existing classification schemes are mainly based on their radio morphology. Aims. In this work, we introduce a novel unsupervised deep learning pipeline to analyse a representative subsample of the Galactic SNR population (~50% of the total) with the aim of finding a connection between their multi-wavelength features and their physical properties. Methods. The pipeline involves two stages: (1) a representation learning stage, consisting of a convolutional autoencoder that feeds on imagery from infrared and radio continuum surveys (WISE 22 μm, Hi-GAL 70 μm and SMGPS 30 cm) and produces a compact representation in a lower-dimensionality latent space; and (2) a clustering stage that seeks meaningful clusters in the latent space that can be linked to the physical properties of the SNRs and their surroundings. Results. Our results suggest that this approach, when combined with an intermediate uniform manifold approximation and projection (UMAP) reprojection of the autoencoded embeddings into a more clusterable manifold, enables us to find reliable clusters. Despite a large number of sources being classified as outliers, most clusters relate to the presence of distinctive features, such as the distribution of infrared emission, the presence of radio shells and pulsar wind nebulae, and the existence of dust filaments.

Assessing the impact of artificial geotextile covers on glacier mass balance and energy fluxes

As global warming accelerates, leading to the retreat of glaciers, the effectiveness of artificial coverings, in particular geotextiles, in reducing glacier ablation has emerged as a topic of increasing concern. Nevertheless, a critical gap in knowledge persists regarding the specific physical processes involved in the mitigation provided by these coverings. This study explores the underlying mechanisms that govern the interaction through field observations and COSIPY model simulations at Bailanghe Glacier No. 21 in the Qilian Mountains from 26 June to 17 September 2023. It compares covered and uncovered areas to evaluate differences in mass and energy balance fluxes. It was discovered that geotextiles could decrease ice melt by up to 1000 mm w.e. in comparison to the surface of glaciers without cover, primarily because of a 23% increase in albedo compared to ice, leading to a decrease in net short-wave radiation and available melt energy. The effect of covering the entire glacier with a geotextile, which has varying albedo properties, was also simulated. It was found that, with every 5% increase in the albedo of the geotextile, ablation was reduced by 10%‒25%, resulting in a decrease in ice volume loss of approximately 2.5 × 105 m3. While artificially covering glaciers can reduce ablation rates, it faces challenges such as high costs, environmental risks, and issues with replicability. Ultimately, this study aims to analyze the feasibility of glacier coverage from a mechanistic perspective for glacier management amidst ongoing climate change.

Radiation Hydrodynamic Simulations of Massive Stars in Gas-rich Environments: Accretion of AGN Stars Suppressed by Thermal Feedback

Massive stars may form in or be captured into active galactic nuclei (AGN) disks. Recent 1D studies employing stellar-evolution codes have demonstrated the potential for rapid growth of such stars through accretion up to a few hundred solar masses. We perform 3D radiation hydrodynamic simulations of moderately massive stars’ envelopes in order to determine the rate and critical radius R crit of their accretion process in an isotropic gas-rich environment in the absence of luminosity-driven mass loss. We find that in the “fast-diffusion” regime where characteristic radiative diffusion speed c/τ is faster than the gas sound speed c s , the accretion rate is suppressed by feedback from gravitational and radiative advection energy flux, in addition to the stellar luminosity. Alternatively, in the “slow-diffusion” regime where c/τ < c s , due to adiabatic accretion, the stellar envelope expands quickly to become hydrostatic and further net accretion occurs on thermal timescales in the absence of self-gravity. When the radiation entropy of the medium is less than that of the star, however, this hydrostatic envelope can become more massive than the star itself. Within this subregime, the self-gravity of the envelope excites runaway growth. Applying our results to realistic environments, moderately massive stars (≲100M ⊙) embedded in AGN disks typically accrete in the fast-diffusion regime, leading to a reduction of steady-state accretion rate 1–2 orders of magnitudes lower than expected by previous 1D calculations and R crit smaller than the disk scale height, except in the opacity window at temperature T ∼ 2000 K. Accretion in slow diffusion regime occurs in regions with very high density ρ ≳ 10−9 g cm−3, and needs to be treated with caution in 1D long-term calculations.

CHIANTI—An Atomic Database for Emission Lines—Paper. XVIII. Version 11, Advanced Ionization Equilibrium Models: Density and Charge Transfer Effects

Version 11 of the chianti database and software package is presented. Advanced ionization equilibrium models have been added for low charge states of seven elements (C, N, O, Ne, Mg, Si, and S), and represent a significant improvement especially when modeling the solar transition region. The models include the effects of higher electron density and charge transfer on ionization and recombination rates. As an illustration of the difference these models make, a synthetic spectrum is calculated for an electron pressure of 7 × 1015 cm−3 K and compared with an active region observation from HRTS. Increases are seen in factors of 2–5 in the predicted radiances of the strongest lines in the UV from Si iv, C iv, and N v, compared to the previous modeling using the coronal approximation. Much better agreement (within 20%) with the observations is found for the majority of the lines. The new atomic models better equip both those who are studying the transition region and those who are interpreting the emission from higher-density astrophysical and laboratory plasma. In addition to the advanced models, several ion data sets have been added or updated, and data for the radiative recombination energy loss rate have been updated.

Two-dimensional viscous study of coupled nonlinear fluid resonances in two narrow gaps

The wave-induced hydrodynamics of coupled nonlinear piston-mode fluid resonances within two narrow gaps between three barges are numerically investigated using a two-dimensional viscous wave flume. This study aims to explore the time-dependent nonlinear interactions between fluid oscillations in the two gaps. The coupled synchronous dynamic behaviors of fluid oscillations during the transient evolution stage are first examined in terms of amplitude and frequency modulation. It is shown that phase dynamics, including phase slipping, trapping, and locking, play significant roles in establishing the coupled synchronous dynamic evolutions of fluid oscillations in the two gaps. The quasi-steady state of the amplitude- and phase-frequency responses of fluid oscillations within the gaps, along with the reflection and transmission waves in front of and behind the three-barge system, are further analyzed. This analysis clarifies the significance of viscous damping energy dissipation and radiation damping energy transfer involved in gap resonance problems. This clarification also explains the performance of fully nonlinear potential flow solvers in predicting fluid resonances in the two narrow gaps. Finally, the nonlinear dynamic features of fluid oscillations are examined. The effects of incident wave nonlinearity, i.e., wave steepness, on resonant frequencies, response amplitudes, energy dissipation, and reflection and transmission coefficients are investigated. Harmonic analysis via Fourier transformation reveals the contributions of first-, second-, and third-order harmonics to the overall response amplitudes. The physical insights gained from this study provide a deeper understanding of the coupled nonlinear dynamics of piston-mode fluid resonances in multiple narrow gaps.

Thermal analysis of mathematical model of heat and mass transfer through bioconvective Carreau nanofluid flow over an inclined stretchable cylinder

In this proceeding the main focus to scrutinize the heat and mass transfer rate increment due to the involvement of motile microorganisms in the Carreau nanofluid flow through an inclined stretchable cylinder under the consequences of activation energy and thermal radiation. This phenomenon has many physical applications in the field of civil, mechanical and seismographic engineering. The research focuses on creating and analyzing new nanocomposites with applications in energy storage, showcasing the transformative impact of nanotechnology on the advancement of high-performance materials. First of all, for the numerical treatment of the above physical model mathematical model is developed in the form of partial differential equations (PDE's) by considering all involving quantities. The resultant model is highly nonlinear and of higher order. Appropriate similarity variables are defined to transform this system of PDE's into first order ordinary differential equations (ODE's). For numerical results we develop a numerical algorithm from nonlinear ODE's and use ‘bvp4c’ built in package of MATLAB. Numerical results are acquired from software in the form of graphical visuals and tabular data as narrated in the results and discussion section. Using this tabular data streamlines are constructed for the better understanding of heat and mass transfer through this phenomenon under the defined constraints. From results, velocity profile increased by the augmentation of values of curvature parameter. Thermal profile is stronger when values of thermophoresis parameter is boosted, Concentration of nanoparticle profile get smoother when temperature coefficient increased, and motile microorganism's density profile is enlarged upon inclining the values of bioconvection lewis number.

Efficient Permeable Monolithic Hybrid Tribo-Piezo-Electromagnetic Nanogenerator Based on Topological-Insulator-Composite.

Escalating energy demands of self-independent on-skin/wearable electronics impose challenges on corresponding power sources to offer greater power density, permeability, and stretchability. Here, a high-efficient breathable and stretchable monolithic hybrid triboelectric-piezoelectric-electromagnetic nanogenerator-based electronic skin (TPEG-skin) is reported via sandwiching a liquid metal mesh with two-layer topological insulator-piezoelectric polymer composite nanofibers. TPEG-skin concurrently extracts biomechanical energy (from body motions) and electromagnetic radiations (from adjacent appliances), operating as epidermal power sources and whole-body self-powered sensors. Topological insulators with conductive surface states supply notably enhanced triboelectric and piezoelectric effects, endowing TPEG-skin with a 288V output voltage (10 N, 4Hz), ∼3 times that of state-of-the-art devices. Liquid metal meshes serve as breathable electrodes and extract ambient electromagnetic pollution (±60V, ±1.6µA cm-2). TPEG-skin implements self-powered physiological and body motion monitoring and system-level human-machine interactions. This study provides compatible energy strategies for on-skin/wearable electronics with high power density, monolithic device integration, and multifunctionality.

Investigating the radiative properties of large dust aggregate particles via the Monte Carlo ray tracing method

Understanding the radiative properties of particles is essential for interpreting and analyzing atmospheric remote sensing, target detection, combustion diagnostics, etc. At present, there is a relative lack of studies and understanding of the radiative properties of large aggregate particles. In this work, we comprehensively investigate the radiative properties of large dust aggregate particles via the developed Monte Carlo ray tracing method. Large dust aggregate models with monodisperse and polydisperse monomers are constructed, respectively. The effects of various factors on the radiative properties of large dust aggregate particles are analyzed. We find that the larger geometric standard deviation and the greater number of monomers lead to slightly larger backscattering and an increase of the overall radiative energy distribution on the receiving surface. With increasing the size parameter, the scattering phase function becomes smoother and the difference between the scattering phase function of spheres and aggregates diminishes. The absorptivity is proportional to the size parameter and inversely proportional to the number of monomers. At a size parameter of 100, the absorptivity and the peak of the radiative energy distribution of monodisperse monomer aggregates are higher than those of polydisperse monomer aggregates, and gradually converge with the increase of particle size parameter. Overall, this work helps to enhance the knowledge of the radiative properties of large aggregate particles.

Study the impact of spacer at thermal degradation process of MLI-based insulation in fire condition

To reduce CO2 emissions, energy carriers such as hydrogen are considered to be a solution. Consumption of hydrogen as a fuel meets several limitations such as its low volumetric energy density in gas phase. To tackle this problem, storage as well as transportation in liquified phase is recommended. To be able to handle this component in liquid phase, an efficient thermal insulation e.g., MLI insulation is required. Different studies have been addressed the vulnerability of such insulation against high thermal loads e.g., in an accident engaging fire. Some of research works have highlighted the importance of considering the MLI thermal degradation focusing on its reflective layer. However, limited number of studies addressed the thermal degradation of spacer material and its effect on the overall heat flux.In this study, through systematic experimental measurements, the effect of thermal loads on glass fleece, glass paper as well as polyester spacers are investigated. The results are reported in various temperature and heat flux profiles. Interpreting the temperature profiles revealed that, as the number of spacers in the medium increases, the peak temperature detectable by the temperature sensor on the measurement plate decreases. Each individual spacer contributes to mitigating the radiative energy received by the measurement plate. Stacks of 20–50 spacers (this is the number of layers in commercial MLI systems applied for liquid hydrogen applications) can potentially reduce the thermal radiation by 1–2 orders of magnitude.An empirical correlation to predict a heat flux attenuation factor is proposed, which is useful for further numerical and analytical studies in the temperature range from ambient to 300 °C.

Study on Characteristics of Epoxy Resin-Based Plastic Scintillators for Detectors with Simulation Using Monte Carlo Code

Abstract To determine the presence of radioactive materials emitting gamma rays entering or exiting nuclear facilities, ports, airports, international borders, or other strategic locations, radiation portal monitors (RPMs) capable of detecting such gamma radiation need to be installed in these places. National Research and Innovation Agency of Indonesia (BRIN) is currently developing RPMs with detector components made of plastic scintillator based on epoxy resin and augmented with aromatic fluorescent materials to produce visible light, which is the working range of the photomultiplier tube (PMT) or silicon photomultiplier (SiPM). This research aims to study the characteristics of the gamma photon radiation energy spectrum from Co-60, Cs-137, and Ir-192 sources in an epoxy resin plastic scintillator and study the absorbed dose of the scintillator to gamma photon radiation energy from Co-60, Cs-137, and Ir-192 sources as a function of source distance and incidence angle of gamma rays with simulations using the MCNPX code. The scintillator is modeled in the form of a cylinder with a diameter of 5 cm and a height of 5 cm. To simulate the gamma photon radiation energy spectrum in the scintillator, the F4 tally was used and to simulate the scintillator absorbed dose, the F6 tally was used. This simulation used gamma sources of Co-60, Cs-137, and Ir-192 of 1 mCi each. These characteristics of the epoxy resin plastic scintillator have been successfully simulated. Data on the characteristics of epoxy resin plastic scintillators is important to know and study as supporting data in making plastic detectors as part of the manufacture and development of RPM.

Factors Influencing Radiation Sound Fields in Logging While Drilling Using an Acoustic Dipole Source

With the increasing number of complex well types in the development stage of oil and gas fields, it is becoming increasingly urgent to use remote detection logging while drilling (LWD) to explore the geological structures in a formation. In this paper, the feasibility and reliability of the dipole remote detection of logging while drilling are demonstrated theoretically. For this purpose, we use an asymptotic solution of elastic wave far-field displacement to derive the calculation formula for the radiation pattern and energy flux of an LWD dipole source. The effects of influencing factors, including the source frequency, formation property, drill collar size, and mud parameter, on the radiation pattern and energy flux are analyzed. The results show that the horizontally polarized shear wave (SH-wave) has a greater advantage in imaging the reflector compared with the cases of the compressive wave (P-wave) and vertically polarized shear wave (SV-wave), which indicates the dominance of the SH-wave in dipole remote detection while drilling. The optimal source excitation frequency of 2.5 kHz and inner and outer radii of the drill collar of 0.02 and 0.1 m, respectively, should be considered in the design of an LWD dipole shear wave reflection tool. However, the heavy drilling mud is not conducive to remote detection during logging while drilling. In addition, the reflection of the SH-wave for the LWD condition is simulated. Under the conditions of optimal source frequency, drill collar size, and mud parameters, the reflection of the SH-wave signal is still detected under the fast formation.

Variation in the Quanta-to-Energy Ratio of Photosynthetically Active Radiation under the Cloudless Atmosphere

The quanta-to-energy ratio plays a crucial role in converting energy units to quantum units in the context of photosynthetically active radiation (PAR). Despite its widespread use, the effects of atmospheric particles and solar zenith angle (SZA) on the quanta-to-energy ratio remain unclear. In this study, both simulation and observation data revealed that the principal wavelength, which can be transformed into the quanta-to-energy ratio using a constant, exhibits a slow initial growth, followed by a rapid increase beyond 60° solar zenith angles and a subsequent dramatic decrease after reaching its maximum value. The measured quanta-to-energy ratio demonstrates a variable range of less than 3% for SZA under 70° in a cloudless atmosphere, with significant changes only occurring at zenith angles above 80°. Simulation data indicate that ozone, wind speed, surface-level pressure, surface air temperature, and relative humidity have negligible effects on the quanta-to-energy ratio. The Ångstrom exponent exerts a minor influence on the quanta-to-energy ratio by affecting diffuse radiation. Visibility, however, is found to have a substantial impact on the quanta-to-energy ratio. As a result, two relationships are established, linking the principal wavelength to visibility and the diffuse fraction of PAR. The principal wavelength serves as an effective measure of solar spectrum variability, remaining unaffected by radiation energy. This implies that atmospheric parameters which do not alter the solar spectrum will not influence the principal wavelength. The strong correlations between the principal wavelength, visibility, and the diffuse fraction of PAR suggest a broader range of applications for the principal wavelength in various research domains, opening up new avenues for exploration and potential contributions to numerous fields.

Circular orbits of accretion flow around charged black hole coupled with a nonlinear electrodynamics field

This study investigates the particle’s geodesic motion and accretion around the spherically symmetric Reissner–Nordström black hole coupled with a nonlinear electrodynamics field. The formation of the disc-like structure in the accretion process arises from the geodesic motion exhibited by particles near the black hole. In the equatorial plane, we analyze the circular orbits of particles and their stability in detail. The analysis of the fluid’s critical flow, maximum accretion rate, radiant flux energy, radioactive efficiency, and radiant temperature are also examined near the central object. We analyze the perturbations experienced by particles throughout, employing restoring forces and the oscillatory behavior of the particles around the black hole. Our results show that the NED parameter ζ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\zeta $$\\end{document} affects the circular geodesics of particles and the maximum accretion rate of the Reissner–Nordström black hole coupled with nonlinear electrodynamics.

Energy of gravitational radiation and the background energy of the space-time

We address the issue of gravitational radiation in the context of the Bondi-Sachs space-time, and consider the expression for the gravitational energy of the radiation obtained in the realm of the teleparallel equivalent of general relativity (TEGR). This expression is independent of the radial distance (i.e., of powers of 1/r) and depends exclusively on the functions c(u,θ,ϕ) and d(u,θ,ϕ), which yield the news functions (u is the retarded time, u=t−r). We investigate the mathematical and physical features of this energy expression in the simpler framework of axial symmetry. Once a burst of gravitational radiation takes place in a self gravitating system, that leads to a loss of the Bondi mass, gravitational radiation is emitted throughout the whole space-time. The existence and presence of this radiation in the background structure of the space-time is consistent with the analysis developed by Papapetrou, and Hallidy and Janis, who found no proof that a gravitational system that emits a burst of gravitational radiation is preceded and followed by two stationary gravitational field configurations, namely, it seems that it is impossible for a gravitational system, which is initially stationary, to return to a stationary state after emitting a burst of axially symmetric gravitational radiation, in which case the space-time is not even asymptotically stationary. Therefore, it is plausible that the gravitational energy of radiation is present in the background structure of the space-time, and this is the energy predicted in the TEGR. This analysis leads us to conjecture that the noise detected in the large terrestrial gravitational wave observatories is intrinsically related to the background gravitational radiation.