Radiation Reaction Effects Research Articles

Bio-convection effects on Williamson nanofluid flow with exponential heat source and motile microorganism over a stretching sheet

This article studies the bio-convection impacts on Williamson nanofluid flow and covers the nonlinear thermal radiation and chemical reaction effects on stretching sheet. The fundamental focus is to enhance heat transfer. Nanofluids are the most important source of effective heat source, having many applications in scientific and technological processes. Nanomaterials with superior thermal characteristics offer a wide range of uses in medicine, energy generation, heat exchange, and electronic cooling systems, among others. The present physical problem involving this flow is contained the nonlinear partial differential equations (PDEs). An appropriate transformation is used to convert the partial differential equations (PDEs) to ordinary differential equations (ODEs), which are then numerically settled utilizing bvp4c method in MATLAB. The physical features of nanofluids such as fluid velocity, volumetric concentration, temperature, and profiles of motile organisms are studied in relation to various factors. Additionally, the skin friction coefficient, Nusselt number, Sherwood number as well as motile microorganism number are calculated numerically using tables. It is found that the velocity profile decreases for the boosted values of Walliamson fluid parameter, magnetic parameter, angle of inclination and buoyancy ratio parameter. The temperature grows by increasing the values of thermophoresis parameter, exponential space and thermally based heat source/sink parameter. A survey of the available literature corroborates the aforementioned results.

Conservative and Radiative Dynamics of Spinning Bodies at Third Post-Minkowskian Order Using Worldline Quantum Field Theory.

Using the spinning worldline quantum field theory formalism we calculate the quadratic-in-spin momentum impulse Δp_{i}^{μ} and spin kick Δa_{i}^{μ} from a scattering of two arbitrarily oriented spinning massive bodies (black holes or neutron stars) in a weak gravitational background up to third post-Minkowskian (PM) order (G^{3}). Two-loop Feynman integrals are performed in the potential region, yielding conservative results. For spins aligned to the orbital angular momentum we find a conservative scattering angle that is fully consistent with state-of-the-art post-Newtonian results. Using the 2PM radiated angular momentum previously obtained by Plefka, Steinhoff, and the present authors, we generalize the angle to include radiation-reaction effects, in which case it avoids divergences in the high-energy limit.

From boundary data to bound states. Part III. Radiative effects

We extend the boundary-to-bound (B2B) correspondence to incorporate radiative as well as conservative radiation-reaction effects. We start by deriving a map between the total change in observables due to gravitational wave emission during hyperbolic-like motion and in one period of an elliptic-like orbit, which is valid in the adiabatic expansion for non-spinning as well as aligned-spin configurations. We also discuss the inverse problem of extracting the associated fluxes from scattering data. Afterwards we demonstrate, to all orders in the Post-Minkowskian expansion, the link between the radiated energy and the ultraviolet pole in the radial action in dimensional regularization due to tail effects. This implies, as expected, that the B2B correspondence for the conservative sector remains unchanged for local-in-time radiation-reaction tail effects with generic orbits. As a side product, this allows us to read off the energy flux from the associated pole in the tail Hamiltonian. We show that the B2B map also holds for non-local-in-time terms, but only in the large-eccentricity limit. Remarkably, we find that all of the trademark logarithmic contributions to the radial action map unscathed between generic unbound and bound motion. However, unlike logarithms, other terms due to non-local effects do not transition smoothly to quasi-circular orbits. We conclude with a discussion on these non-local pieces. Several checks of the B2B dictionary are displayed using state-of-the-art knowledge in Post-Newtonian/Minkowskian theory.

Mixed convective flow of a magnetohydrodynamic Casson fluid through a permeable stretching sheet with first-order chemical reaction.

This research article presents the magnetohydrodynamic Casson fluid flow through an extending surface embedded in a porous medium. Furthermore, the Casson fluid flow is investigated under the effects of thermal radiation, Joule heating, viscous dissipation, and chemical reaction. The analytical solution of the modeled problem is utilized with the help of homotopy analysis method (HAM). The convergence region of the applied technique is portrayed graphically. The impacts of the embedded factors on the flow profiles are exhibited with the help of figures. Furthermore, numerical values of the surface drag force, heat, and mass transfer rates are highlighted via table. The results show that the augmented Darcy number, Casson and magnetic parameters have declined the velocity profile of the Casson fluid flow. Growth in Brownian motion augments the chaotic motion amongst the particles due to which the kinetic energy of the particles transforms to heat energy which consequently augmented the thermal profile, while reduced the concentration profile. The mass and energy profiles are positively effects with the increment of thermophoresis term. And the growing values of chemical reaction and Lewis number cause a reduction in the diffusivity of mass of fluid due to which less transfer of mass takes place that weakens the concentration layer thickness and declines the concentration profiles.

Effects of non-linear radiation and chemical reaction on Oldroyd‐B nanofluid near oblique stagnation point flow

The oblique stagnation point flow of a viscoelastic nanofluid over a stretching cylinder is entertained in presence of non-linear thermal radiation and chemical reaction. Buongiorno's model is used to incorporate the significance of Brownian motion and thermophoresis diffusion. The governing partial differential equations in cylindrical polar coordinates are first transformed to system of ordinary differential equations using suitable transformations and dimensionless variables and then simulated numerically. Impact of interesting parameters on flow and heat transfer features is analyzed graphically and numerically. It is noticed that axial velocity increases with the retardation parameter while tangential velocity reduces. The magnitude of both axial and tangential velocities is large over stretching cylinder as compared to stretching sheet. Radiation parameter enhanced temperature profile and chemical reaction parameter rise the concentration profile.

Ready-to-use analytic model for gravitational waves from a hierarchical triple with Kozai-Lidov oscillations

Gravitational waves emitted by inner binaries in hierarchical triple systems are interesting astrophysical candidates for space-based detectors like the Laser Interferometer Space Antenna, LISA. In the presence of a third body, such as a supermassive black hole, an inner binary consisting of intermediate mass black holes can undergo oscillations in eccentricity and inclination angle due to the Kozai-Lidov mechanism. In this work, we construct analytic gravitational waveforms in the Fourier domain, taking into account the Kozai-Lidov effect at Newtonian (leading) order. Using multiple-scale analysis, we make use of the separability of timescales to combine the effects of both Kozai-Lidov oscillations and radiation-reaction. We assume small eccentricity and present analytic solutions to the evolution of the other orbital elements. Our analytic calculation can be systematically extended to higher orders in eccentricity, and can be used to construct inspiral-merger-ringdown models. The imprint on the waveform, due to this combined evolution, is computed under the stationary-phase approximation. We find that the oscillations leave a clear signature on the Fourier amplitude of the waveform while leaving a measurable imprint on the gravitational wave phase, and that our analytic results are consistent with numerics. Further, with our study of the astrophysical parameters of the hierarchical triple, we outline potential source candidates, along with potential implications for gravitational wave data analysis.

Higher Order Chemical Reaction and Radiation Effects on Magnetohydrodynamic Flow of a Maxwell Nanofluid With Cattaneo–Christov Heat Flux Model Over a Stretching Sheet in a Porous Medium

Abstract In this paper, we investigated the heat and mass transfer analysis of an MHD convection flow of Maxwell nanofluid with Cattaneo–Christov heat flux model along with a porous stretching sheet. The effects of thermal radiation, viscous dissipation, suction/injection, and higher-order chemical reaction are taken into consideration. By using similarity transformations the governing equations of the study are reduced into a system of ordinary differential equations and solved numerically by using the BVP5C matlab package. The effects of dimensionless parameters on the present study are deliberated with the aid of graphs and tables. It is found that an increase in thermal Grashof number, thermal radiation, and thermal relaxation time parameter drops the temperature field. The heat transfer rate is declined with enhancing heat source, Brownian motion and thermophoresis parameters. Also, observed that the concentration field reduces with the rising value of chemical reaction. The numerically computed values of Nusselt number and Sherwood number are validated with existing literature and found a good agreement.

Analytical Solution for Impact of Caputo-Fabrizio Fractional Derivative on MHD Casson Fluid with Thermal Radiation and Chemical Reaction Effects

Fractional derivatives have been proven to showcase a spectrum of solutions that is useful in the fields of engineering, medical, and manufacturing sciences. Studies on the application of fractional derivatives on fluid flow are relatively new, especially in analytical studies. Thus, geometrical representations for fractional derivatives in the mechanics of fluid flows are yet to be discovered. Nonetheless, theoretical studies will be useful in facilitating future experimental studies. Therefore, the aim of this study is to showcase an analytical solution on the impact of the Caputo-Fabrizio fractional derivative for a magnethohydrodynamic (MHD) Casson fluid flow with thermal radiation and chemical reaction. Analytical solutions are obtained via Laplace transform through compound functions. The obtained solutions are first verified, then analysed. It is observed from the study that variations in the fractional derivative parameter, α, exhibits a transitional behaviour of fluid between unsteady state and steady state. Numerical analyses on skin friction, Nusselt number, and Sherwood number were also analysed. Behaviour of these three properties were in agreement of that from past literature.

Numerical solution of chemically reactive and thermally radiative MHD Prandtl nanofluid over a curved surface with convective boundary conditions

This study intends to elaborate the heat and mass transfer analysis of Prandtl nanofluid flow over a vertically heated curved surface together with MHD, thermal radiation, and chemical reaction effects. The boundary layer approximations developed the governing flow equations such as momentum, energy, and diffusion balance equations. The nonlinear system of PDEs is changed into nonlinear ordinary differential equations via proper transformations. By taking the assistance of the bvp4c algorithm, the numerical technique is imposed explicitly for attaining the dimensionless form of the fundamental equations. The nondimensional outcomes are apprehended here which rely on numerous physical constraints. The impression of these physical parameters on momentum and thermal boundary layers along with concentration outlines are discussed and demonstrated graphically. The impact of drag force, heat transfer coefficient, and mass flow rate are computed and presented through tables.

Radiation pressure acceleration of protons from structured thin-foil targets

The process of radiation pressure acceleration (RPA) of ions is investigated with the aim of suppressing the Rayleigh–Taylor-like transverse instabilities in laser–foil interaction. This is achieved by imposing surface and density modulations on the target surface. We also study the efficacy of RPA of ions from density modulated and structured targets in the radiation dominated regime where the radiation reaction effects are important. We show that the use of density modulated and structured targets and the radiation reaction effects can help in achieving the twin goals of high ion energy (in GeV range) and lower energy spread.

Soret radiation and chemical reaction effect on MHD Jeffrey fluid flow past an inclined vertical plate embedded in porous medium

In this manuscript a study of the unsteady magneto-hydrodynamic mixed convection Jeffrey fluid flow over an inclined permeable moving plate in presence of thermal radiation, heat generation, radiation, aligned magnetic field, thermophoresis effect and homogenous chemical reaction, subjected to variable suction has been undertaken. The governing equations are solved by using a regular perturbation technique. The expressions for the distributions of velocity, temperature and species concentration are obtained. With the aid of these, the expressions for skin friction, Nusselt number and Sherwood number also have been derived. The influences of various physical Parameters involved in the problem on the above mentioned quantities are discussed with the help of graphs and tables. From the significant findings, it has been found that the velocity increases with an increase in Jeffrey fluid in the presence of permeability. It shows reverse effects in the case of magnetic parameter, radiation parameter and chemical reaction parameter. Comparisons with previously published work performed and the results are found to be in the excellent agreement.

Radiative contributions to gravitational scattering

The linear-order effects of radiation-reaction on the classical scattering of two point masses, in General Relativity, are derived by a variation-of-constants method. Explicit expressions for the radiation-reaction contributions to the changes of 4-momentum during scattering are given to linear order in the radiative losses of energy, linear-momentum and angular momentum. The polynomial dependence on the masses of the 4-momentum changes is shown to lead to non-trivial identities relating the various radiative losses. At order $G^3$ our results lead to a streamlined classical derivation of results recently derived within a quantum approach. At order $G^4$ we compute the needed radiative losses to next-to-next-to-leading-order in the post-Newtonian expansion, thereby reaching the absolute fourth and a half post-Newtonian level of accuracy in the 4-momentum changes. We also provide explicit expressions, at the absolute sixth post-Newtonian accuracy, for the radiation-graviton contribution to {\it conservative} $O(G^4)$ scattering. At orders $G^5$ and $G^6$ we derive explicit theoretical expressions for the last two hitherto undetermined parameters describing the fifth-post-Newtonian dynamics. Our results at the fifth-post-Newtonian level confirm results of [Nucl. Phys. B \textbf{965}, 115352 (2021)] but exhibit some disagreements with results of [Phys. Rev. D \textbf{101}, 064033 (2020)].

Beamstrahlung-enhanced disruption in beam–beam interaction

The radiation reaction (beamstrahlung) effect on particle dynamics during interaction of oppositely charged beams is studied. It is shown that the beam focusing can be strongly enhanced due to beamstrahlung. An approximate analytical solution of the motion equations including the radiation reaction force is derived. The disruption parameter is calculated for classical and quantum regime of beamstrahlung. The analytical model is verified by QED-PIC simulations. The model for head-on collision of long beams undergoing a number of betatron oscillation during interaction is also developed. It is demonstrated that the beamstrahlung-enhanced disruption effect can play an important role in future lepton colliders with high-current particle beams.

Parametric analysis of MHD flow of nanofluid in stretching sheet under chemical sensitivity and thermal radiation

AbstractThis study examines the impact that entropy production has on electric magnetohydrodynamics (MHD) hybrid nanofluid (Al2O3–SiC) flows due to the effect of thermal radiation and chemical reaction on permeable stretching sheets. A key element of this study is that to increase thermal conductivity and improve convective heat transfer, the field of electricity is used in the MHD model with entropy production, and the solution technique utilizing “bvp4c” was presented. Through appropriate transformations and analyses of entropy generation, the constituent equations have been turned into strong, nonlinear, ordinary differential equations; the entropy generated rate for a system is crucial to optimize energy in the system to work efficiently. Subsequently, these transformed equations are solved by the “bvp4c” package in MATLAB. The thermal transfer system contains velocity, temperature, and concentration profiles with novel parameters included such as the unsteady parameter, the Grashof number, the mass Grashof number, Prandtl number, Brownian motion parameter, the Schmidt number, the thermophoresis parameter, the porosity parameter, the magnetic field parameter, the electric field parameter, the Eckert number, the Brinkman number, the radiation parameter, and chemical reaction. In addition, the study analyses the prediction accuracy of thermal conductivity enhancement using an artificial neural network (ANN) with data from the values of the numerical solution. This analysis is performed with the help of MATLAB. The result of this research concludes that the decrease in the magnetic field and porosity parameters stimulate a rise in the velocity of nanofluid; the parameters of the magnetic field, electric field, and thermal radiation increase, the temperature of the nanofluid increases, and the increase in the parameters of Schmidt number, Brownian motion, and the chemical reaction delivers a decrease in the concentration level of nanofluid. Two current methods are compared to the approach applied in this study. Finally, the ANN results in better accuracy of thermal conductivity enhancement values from the numerical values. Hence, this study concludes with the accurate thermal conductivity enhancement of the nanofluid with the impacts of a chemical reaction and thermal radiation.

Nanomechanical Concepts in Magnetically Guided Systems to Investigate the Magnetic Dipole Effect on Ferromagnetic Flow Past a Vertical Cone Surface

Because of the floating magnetic nanomaterial, ferrofluids have magneto-viscous properties, enabling controllable temperature changes as well as nano-structured fluid characteristics. The study’s purpose is to evolve and solve a theoretical model of bioconvection nanofluid flow with a magnetic dipole effect in the presence of Curie temperature and using the Forchheimer-extended Darcy law subjected to a vertical cone surface. The model also includes the nonlinear thermal radiation, heat suction/injection, viscous dissipation, and chemical reaction effects. The developed model problem is transformed into nonlinear ordinary differentials, which have been solved using the homotopy analysis technique. In this problem, the behavior of function profiles are graphically depicted and explained for a variety of key parameters. For a given set of parameters, tables representthe expected numerical values and behaviors of physical quantities. The nanofluid velocity decreases as the ferrohydrodynamic, local inertia, and porosity parameters increase and decrease when the bioconvection Rayleigh number increases. Many key parameters improved the thermal boundary layer and temperature. The concentration is low when the chemical reaction parameter and Schmidt number rises. Furthermore, as the bioconvection constant, Peclet and Lewis numbers rise, so does the density of motile microorganisms.

Effect of laser temporal intensity skew on enhancing pair production in laser—electron-beam collisions

Recent high-intensity laser experiments (Cole et al 2018 Phys. Rev. X 8 011020; Poder et al 2018 Phys. Rev. X 8 031004) have shown evidence of strong radiation reaction in the quantum regime. Experimental evidence of quantum effects on radiation reaction and electron–positron pair cascades has, however, proven challenging to obtain and crucially depends on maximising the quantum parameter of the electron (defined as the ratio of the electric field it feels in its rest frame to the Schwinger field). The quantum parameter can be suppressed as the electrons lose energy by radiation reaction as they traverse the initial rise in the laser intensity. As a result the shape of the intensity temporal envelope becomes important in enhancing quantum radiation reaction effects and pair cascades. Here we show that a realistic laser pulse with a faster rise time on the leading edge, achieved by skewing the temporal envelope, results in curtailing of pair yields as the peak power is reduced. We find a reduction in pair yields by orders of magnitude in contrast to only small reductions reported previously in large-scale particle-in-cell code simulations (Hojbota et al 2018 Plasma Phys. Control. Fusion 60 064004). Maximum pairs per electron are found in colliding 1.5 GeV electrons with a laser wakefield produced envelope 7.90 × 10−2 followed by a short 50 fs Gaussian envelope, 1.90 × 10−2, while it is reduced to 8.90 × 10−5, a factor of 100, for an asymmetric envelope.

Infrared divergences and the eikonal exponentiation

The aim of this article is to explore the interplay between the eikonal resummation in impact-parameter space and the exponentiation of infrared divergences in momentum space for gravity amplitudes describing collisions of massive objects. The eikonal governs the classical dynamics relevant to the two-body problem, and its infrared properties are directly linked to the zero-frequency limit of the gravitational wave emission spectrum and to radiation-reaction effects. Combining eikonal and infrared exponentiations it is possible to derive these properties at a given loop order starting from lower-loop data. This is illustrated explicitly in $\mathcal{N}=8$ supergravity and in general relativity by deriving the divergent part of the two-loop eikonal from tree-level and one-loop elastic amplitudes.

Significance of the physical quantities for the non-Newtonian fluid flow in an irregular channel with heat and mass transfer effects: Lie group analysis

Physical quantities such as skin friction coefficient, local Nusselt number, and local Sherwood number for Casson fluid flow in an irregular channel are determined in this article. Casson fluid properties are primarily enhanced in this flow due to the effects of magnetohydrodynamic (MHD), porous medium, thermal radiation, viscous dissipation, and chemical reaction. Because of the pressure gradient, oscillatory waves formed at the ends of the walls, which are also kept at constant temperatures and concentrations. The Lie group method is used to convert partial differential equations (PDEs) to ordinary differential equations (ODEs). Analytical solutions are provided for the momentum, energy, and concentration equations with benchmark solutions. Dimensionless numbers are computed to interpret physical quantities for this type of flow via graphs and tables. According to the variations of the emerging parameters, physical quantities exhibited reverse behaviour between the upper and lower walls. The velocity profile has an increasing attitude toward the Casson fluid parameter, the Darcy parameter, the wavelength, and the Reynolds number, but a decreasing attitude toward the Hartmann number. The concentration profile is decreasing due to the oscillation effect, but the Schmidt number has a growing influence.

Effects of radiation and chemical reaction on Cu–Al$$_{2}$$O$$_{3}$$/water hybrid flow past a melting surface in the existence of cross magnetic field

Effects of radiation and chemical reaction on Cu–Al$$_{2}$$O$$_{3}$$/water hybrid flow past a melting surface in the existence of cross magnetic field

Neutron stars in the effective fly-by framework: f-mode re-summation

Eccentric compact binaries pose not only a challenge for gravitational wave (GW) detectors, but also provide a probe into the nuclear equation of state if one of the objects is a neutron star. At the short pericenter passage, tidal interactions excite f-modes on the star, which in turn emit their own GWs. We derive an analytic waveform for these stellar oscillations within the effective fly-by framework, modeling the emission to leading post-Newtonian order. At this order, the f-mode response can be written in a Fourier decomposition in terms of orbital harmonics, with the amplitudes of each harmonic depending on Hansen coefficients. Re-summing the harmonics of the f-mode results in a simple decaying harmonic oscillator, with the amplitude now determined by a Hansen coefficient of complex harmonic number. We compute the match between the re-summed f-mode and numerical integrations of the tidal response, and find for systems with high orbital eccentricity (e > 0.8) and low semi-latus rectum (p < 15M) for three equations of state. We further compare our model to modes generated from subsequent pericenter passages under the effect of radiation reaction, and develop an accurate model to time pericenter passages. We show how the timing model can be used to specify initial conditions to accurate track the f-mode excitation across multiple pericenter passages.