Radiation Friction Research Articles

QED cascades induced by circularly polarized laser fields

The results of Monte-Carlo simulations of electron-positron-photon cascades initiated by slow electrons in circularly polarized fields of ultra-high strength are presented and discussed. Our results confirm previous qualitative estimations [A.M. Fedotov, et al., PRL 105, 080402 (2010)] of the formation of cascades. This sort of cascades has revealed the new property of the restoration of energy and dynamical quantum parameter due to the acceleration of electrons and positrons by the field and may become a dominating feature of laser-matter interactions at ultra-high intensities. Our approach incorporates radiation friction acting on individual electrons and positrons.

A Hamiltonian model of dissipative wave–particle interactions and the negative-mass effect

The effect of radiation friction is included in the Hamiltonian treatment of wave–particle interactions with autoresonant phase-locking, yielding a generalized canonical approach to the problem of dissipative dynamics near a nonlinear resonance. As an example, the negative-mass effect exhibited by a charged particle in a pump wave and a static magnetic field is studied in the presence of the friction force due to cyclotron radiation. Particles with negative parallel masses m ∥ are shown to transfer their kinetic energy to the pump wave, thus amplifying it. Counterintuitively, such particles also undergo stable dynamics, decreasing their transverse energy monotonically due to cyclotron cooling, whereas some of those with positive m ∥ undergo cyclotron heating instead, extracting energy from the pump wave.

Absence of Embedded Mass Shells: Cerenkov Radiation and Quantum Friction

We show that, in a model where a non-relativistic particle is coupled to a quantized relativistic scalar Bose field, the embedded mass shell of the particle dissolves in the continuum when the interaction is turned on, provided the coupling constant is sufficiently small. More precisely, under the assumption that the fiber eigenvectors corresponding to the putative mass shell are differentiable as functions of the total momentum of the system, we show that a mass shell could exist only at a strictly positive distance from the unperturbed embedded mass shell near the boundary of the energy-momentum spectrum.

Schwinger Limit Attainability with Extreme Power Lasers

High intensity colliding laser pulses can create abundant electron-positron pair plasma [A. R. Bell and J. G. Kirk, Phys. Rev. Lett. 101, 200403 (2008)], which can scatter the incoming electromagnetic waves. This process can prevent one from reaching the critical field of quantum electrodynamics at which vacuum breakdown and polarization occur. Considering the pairs are seeded by the Schwinger mechanism, it is shown that the effects of radiation friction and the electron-positron avalanche development in vacuum depend on the electromagnetic wave polarization. For circularly polarized colliding pulses, these effects dominate not only the particle motion but also the evolution of the pulses. For linearly polarized pulses, these effects are not as strong. There is an apparent analogy of these cases with circular and linear electron accelerators to the corresponding constraining and reduced roles of synchrotron radiation losses.

Parameters determining water temperature of a proglacial stream: The Phelan Creek and the Gulkana Glacier, Alaska

AbstractThe heat budget of a proglacial stream, Phelan Creek, from the Gulkana Glacier, Alaska, is estimated by using the hourly time series of stream water temperature, discharge and meteorology obtained in the summer of 2006. As an analytical result, the net shortwave radiation and bed friction occupied 32.1 and 38.2% of the total thermal input to the stream, respectively. The time series of the water temperature were simulated by a deterministic model with the coupling of the heat budget and the thermal advective diffusion equation. The simulated result is agreeable to the observed one with the Nash‐Sutcliffe efficiency (NASH) of 0.747 and the root‐mean‐square error (RMSE) of 0.236°C over the observation period. However, under condition that the rainfall of more than 1 mm h−1 occurs continually for more than a day, the simulation was less reasonable with NASH = 0.225 and RMSE = 0.226°C. This is probably because the relatively warm subsurface flow input to the stream channel from the non‐glacial area. Copyright © 2009 John Wiley & Sons, Ltd.

Effect of tunnel resonances on fluxon radiation loss in a long S-I-S tunnel junction with weak structural disorder in the I layer

The expression for the density of the bias current, which compensates for the radiation loss of a fluxon moving in an S-I-S (superconductor-insulator-superconductor) tunnel junction with tunnel resonances-quantum resonant percolation trajectories (quantum jumpers), randomly formed in the disordered I layer [1], has been derived. The substantial physical difference between the described model and the model with microjumpers in the I layer [2] is that radiation friction acts on fluxon only in the narrow energy range of tunnel resonances.

Computation of springing transfer functions

Ship vibrations excited continually by regular waves are predicted by a potential method. It takes into account the interaction of the oscillatory flow with the steady flow due to the ship's forward speed, including steady ship waves and squat, but it excludes non-linear oscillatory wave forces. A three-dimensional Rankine source patch method is used both for the steady and the oscillatory flow. Vibration damping by an immersed transom, wave radiation, bilge keels, propeller, and hatch cover friction are approximated. Application to a large containership demonstrates that, in this example, damping is mostly attributable to the transom.

Quantum statistical theory of radiation friction of a relativistic electron

We comprehensively investigate the effect of quantum space-time nonlocality that accounts for retardation of the electron interaction with both the electron’s own radiation field and the fluctuation field of the electromagnetic vacuum. We rigorously show that the quantum nonlocality effect eliminates the self-acceleration and the causality violation paradoxes that are inherent in the classical theory of radiation friction.

On the limits of induced radiation concept in FELs

We discuss a restriction of the induced radiation concept in classical beam systems due to accompanying spontaneous radiation (radiation friction). For short wave FELs, spontaneous radiation renders a noticeable influence on the phasing of particles, which is the base mechanism of induced radiation in classical systems. It leads to an essential restriction on the radiating system length and gain which cannot be compensated by an increase in the beam current.

ON THE PROBLEM OF RADIATION FRICTION BEYOND FOUR AND SIX DIMENSIONS

We count the number of independent structures which can arise in expressions for radiation friction force in different even space–time dimensions and demonstrate that their number is too big at d ≥ 8 to allow determination of this force from the transversality condition alone, as was done by B. Kosyakov in 6d. This implies that in general one cannot bypass a tedious calculation involving explicit regularization and evaluation of emerging counterterms. However, simple Kosyakov's method works nicely in any dimension for the special case of circular motion with constant angular velocity.

Experimental investigation of effects of bio-additives on fuel economy of the gasoline engine

The matter extracted from palm oil was considered as gasoline additive. The effect of various percentages (0.2%, 0.4% and 0.6%) of the bio-additives on fuel economy of SI engine respectively running on prime gasoline, gasoline with known components, ethanol gasoline, and methanol gasoline under typical urban operation condition 2000 r/min was investigated. The results showed that the bio-additives can remarkably improve the fuel economy of SI engine while operating on all kinds of fuel. The optimal ratio of bio-additive to gasoline depends on the fuel used and on the different engine operating conditions. Besides, the experiments of constant volume combustion bomb, analysis of in cylinder processes, the synchrotron radiation and high-temperature friction were conducted to probe into the mechanism of the bio-additive impact on fuel economy. It indicated that the bio-additives can increase the maximum cylinder combustion pressure, improve exhaust emissions and largely reduce the frication coefficient.

Doppler Optomechanics of a Photonic Crystal

A laser beam directed at a mirror attached onto a flexible mount adds friction to its mechanical motion by the Doppler effect. For a normal mirror the efficiency of this radiative Doppler friction is very weak and practically masked by laser shot noise. We find that it can become very efficient using a photonic crystal mirror near its photonic band gaps. As an example, a Bragg mirror used at the long wavelength edge of its band stop can be efficiently optically cooled using the Doppler friction. The opposite effect opens new routes for optical pumping of mechanical systems: a laser pointing at a Bragg mirror and tuned at its short wavelength edge induces amplification of the vibrational excitation of the mirror leading eventually to its self-oscillation. These new effects rely on the strong dependency of a photonic crystal reflectivity on the wavelength.

Self-interaction and regularization of classical electrodynamics in higher dimensions

The classical electrodynamic system of a field and a single point-like source is considered in even-dimensional spacetime. The problem of self-interaction is discussed. It is manifestly shown that all singular terms appearing in these equations can be regularized. Relations between formulas for radiation and radiation friction are discussed.

Investigation of Divertor Detachment in EAST by `Two-Point' Model

Divertor plasma detachment offers one of the most promisingoperating modes for fusion devices because of low target powerloading. In this article a `two-point' model is used to investigatethe formation of detachment and explore the route to detachment inEAST, in order to find an ideal operation window. The simulationresults show that impurity radiation and ion-neutral friction arethe main causes of divertor plasma detachment at the target plates.Raising the safety factor and reducing the upstream power densityprovide effective means to achieve the detachment due to theincreased radiation power fraction. Puffing Ar and Ne impurities andraising the safety factor can bring the upstream high plasmatemperature region (above 100 eV) and the low target plasmatemperature region (below 10 eV) close to each other in terms ofthe separatrix density. But it is difficult to find a commonoperating region which satisfies both conditions. High recycling anddetached regimes provides an ideal operation window because of thesteady upstream condition and low target power load.

Interaction of plane gravitational waves with a Fabry-Perot cavity in the local Lorentz frame

We analyze the interaction of the plane `$+$'-polarized gravitational waves with a Fabry-Perot cavity in the local Lorentz frame of the cavity's input mirror outside of the range of long-wave approximation with the force of radiation pressure taken into account. The obtained detector's response signal is represented as a sum of two parts: (i) the phase shift due to displacement of a movable mirror under the influence of a gravitational wave and the force of light pressure, and (ii) the phase shift due to the direct interaction of a gravitational wave with light wave inside the cavity. We obtain the formula for the movable mirror's law of motion paying close attention to the phenomena of optical rigidity, radiative friction, and direct coupling of a gravitational wave to light wave. Some issues concerning the detection of high-frequency gravitational waves and the role of optical rigidity in it are discussed. We also examine in detail special cases of optical resonance and small detuning from it and compare our results with the known ones.

Dynamics of triple black hole systems in hierarchically merging massive galaxies

Galaxies with stellar bulges are generically observed to host supermassive black holes (SMBHs). The hierarchical merging of galaxies should therefore lead to the formation of SMBH binaries. Merging of old massive galaxies with little gas promotes the formation of low-density nuclei where SMBH binaries are expected to survive over long times. If the binary lifetime exceeds the typical time between mergers, then triple black hole (BH) systems may form. We study the statistics of close triple SMBH encounters in galactic nuclei by computing a series of three-body orbits with physically motivated initial conditions appropriate for giant elliptical galaxies. Our simulations include a smooth background potential consisting of a stellar bulge plus a dark matter halo, drag forces due to gravitational radiation and dynamical friction on the stars and dark matter, and a simple model of the time evolution of the inner density profile under heating and mass ejection by the SMBHs. We find that the binary pair coalesces as a result of repeated close encounters in ∼85 per cent of our runs, and in ∼15 per cent of cases a new eccentric binary forms from the third SMBH and binary remnant and coalesces during the run time. In about 40 per cent of the runs the lightest BH is left wandering through the galactic halo or escapes the galaxy altogether, but escape of all three SMBHs is exceedingly rare. The triple systems typically scour out cores with mass deficits ∼one–two times their total mass, which can help to account for the large cores observed in some massive elliptical galaxies, such as M87. The high coalescence rate, prevalence of very high-eccentricity orbits, and gravitational radiation ‘spikes’ during close encounters in our runs, may provide interesting signals for the future Laser Interferometer Space Antenna (LISA).

Radiative losses in plasma accelerators

We investigate the dynamics of a relativistic electron in a strongly nonlinear plasma wave in terms of classical mechanics by taking into account the action of the radiative reaction force. The two limiting cases are considered. In the first case where the energy of the accelerated electrons is low, the electron makes many betatron oscillations during the acceleration. In the second case where the energy of the accelerated electrons is high, the betatron oscillation period is longer than the electron residence time in the accelerating phase. We show that the force of radiative friction can severely limit the rate of electron acceleration in a plasma accelerator.

Radiation friction in fractal clusters

The classical problem of radiation damping is formulated for fractal clusters in terms of interference of radiation friction forces within a small number of aggregated particles, with their interactions being described in the dipole-dipole approximation. The general theory is developed for spherical particles with arbitrary sizes. For particular configurations, the interference nature of the radiation widths of the normal dipole oscillations of aggregates is demonstrated.

Dipole traps for neutral atoms formed by nonuniformly polarised Laguerre modes

Field configurations of two counterpropagating nonuniformly polarised Laguerre modes forming three-dimensional dipole traps for neutral atoms are proposed. Peculiarities of the stochastic dynamics of atoms in such traps, associated with the anisotropy of dipole forces and manifestations of various radiative friction mechanisms are analysed. The problem of increasing the confinement time for atoms in such field configurations is studied.

Superradiation from crystals of high-spin molecular nanomagnets

Phenomenological theory of superradiation from crystals of high-spin molecules is suggested. We show that radiation friction can cause a superradiation pulse and investigate the role of magnetic anisotropy, external magnetic field, and dipole-dipole interactions. Depending on the contribution of all these factors at low temperature, several regimes of magnetization of crystal sample are described. Very fast switch of magnetization's direction for some sets of parameters is predicted.