34,091 research outputs found

### Radiation Pressure Quantization

Kepler's observation of comets tails initiated the research on the radiation
pressure of celestial objects and 250 years later they found new incarnation
after the Maxwell's equations were formulated to describe a plethora of
light-matter coupling phenomena. Further, quantum mechanics gave birth to the
photon drag effect. Here, we predict a novel universal phenomenon which can be
referred to as quantization of the radiation pressure. We develop a microscopic
theory of this effect which can be applied to a general system containing
Bose-Einstein-condensed particles, which possess an internal structure of
quantum states. By analyzing the response of the system to an external
electromagnetic field we find that such drag results in a flux of particles
constituting both the condensate and the excited states. We show that in the
presence of the condensed phase, the response of the system becomes quantized
which manifests itself in a step-like behavior of the particle flux as a
function of electromagnetic field frequency with the elementary quantum
determined by the internal energy structure of the particles.Comment: Manuscript: 4 pages, 3 figure

### Stellar feedback by radiation pressure and photoionization

The relative impact of radiation pressure and photoionization feedback from
young stars on surrounding gas is studied with hydrodynamic radiative transfer
(RT) simulations. The calculations focus on the single-scattering (direct
radiation pressure) and optically thick regime, and adopt a moment-based
RT-method implemented in the moving-mesh code AREPO. The source luminosity, gas
density profile and initial temperature are varied. At typical temperatures and
densities of molecular clouds, radiation pressure drives velocities of order
~20 km/s over 1-5 Myr; enough to unbind the smaller clouds. However, these
estimates ignore the effects of photoionization that naturally occur
concurrently. When radiation pressure and photoionization act together, the
latter is substantially more efficient, inducing velocities comparable to the
sound speed of the hot ionized medium (10-15 km/s) on timescales far shorter
than required for accumulating similar momentum with radiation pressure. This
mismatch allows photoionization to dominate the feedback as the heating and
expansion of gas lowers the central densities, further diminishing the impact
of radiation pressure. Our results indicate that a proper treatment of the
impact of young stars on the interstellar medium needs to primarily account for
their ionization power whereas direct radiation pressure appears to be a
secondary effect. This conclusion may change if extreme boosts of the radiation
pressure by photon trapping are assumed.Comment: 18 pages, 19 figures (main results presented in 13 pages, 10 figures;
extended appendix for RT tests with extra 9 figures). Accepted for
publication in MNRAS after tiny change

### Micromechanical resonator driven by radiation pressure force

Radiation pressure exerted by light on any surface is the pressure generated by the momentum of impinging photons. The associated force - fundamentally, a quantum mechanical aspect of light - is usually too small to be useful, except in large-scale problems in astronomy and astrodynamics. In atomic and molecular optics, radiation pressure can be used to trap or cool atoms and ions. Use of radiation pressure on larger objects such as micromechanical resonators has been so far limited to its coupling to an acoustic mode, sideband cooling, or levitation of microscopic objects. In this Letter, we demonstrate direct actuation of a radio-frequency micromechanical plate-type resonator by the radiation pressure force generated by a standard laser diode at room temperature. Using two independent methods, the magnitude of the resonator's response to forcing by radiation pressure is found to be proportional to the intensity of the incident light.https://www.nature.com/articles/s41598-017-16063-4.epdfPublished versio

### Precise Model for Small-Body Thermal Radiation Pressure Acting on Spacecraft

A precise representation of small-body surface thermal radiation pressure effects acting on orbiting spacecraft is discussed. The proposed framework takes advantage of a general Fourier series expansion to compute small-body surface thermal radiation pressure. Fourier series expansion has been used before for the precise representation of solar radiation pressure effects on spacecraft orbiting small bodies. This framework takes into account the geometric relationship of orbiting spacecraft with the small-body surface, surface thermal parameters of the small body, and the shape and surface properties of spacecraft allowing for the computation of thermal radiation pressure, which may also be used for the generation of precise orbit determination solutions. After presenting the general model, an example application of the model for the OSIRIS-REx spacecraft in orbit about Asteroid (101955) Bennu is provided. Simulation studies were used to evaluate the effect of mismodeling of thermal radiation pressure on the spacecraft and study the use of the proposed method for generating precise orbit determination solutions

### Theory for planetary exospheres: III. Radiation pressure effect on the Circular Restricted Three Body Problem and its implication on planetary atmospheres

The planetary exospheres are poorly known in their outer parts, since the
neutral densities are low compared with the instruments detection capabilities.
The exospheric models are thus often the main source of information at such
high altitudes. We present a new way to take into account analytically the
additional effect of the stellar radiation pressure on planetary exospheres. In
a series of papers, we present with an Hamiltonian approach the effect of the
radiation pressure on dynamical trajectories, density profiles and escaping
thermal flux. Our work is a generalization of the study by Bishop and
Chamberlain (1989). In this third paper, we investigate the effect of the
stellar radiation pressure on the Circular Restricted Three Body Problem
(CR3BP), called also the photogravitational CR3BP, and its implication on the
escape and the stability of planetary exospheres, especially for Hot Jupiters.
In particular, we describe the transformation of the equipotentials and the
location of the Lagrange points, and we provide a modified equation for the
Hill sphere radius that includes the influence of the radiation pressure.
Finally, an application to the hot Jupiter HD 209458b reveals the existence of
a blow-off escape regime induced by the stellar radiation pressure

### Radiation Pressure Feedback in Galaxies

We evaluate radiation pressure from starlight on dust as a feedback mechanism
in star-forming galaxies by comparing the luminosity and flux of star-forming
systems to the dust Eddington limit. The linear LFIR--L'HCN correlation
provides evidence that galaxies may be regulated by radiation pressure
feedback. We show that star-forming galaxies approach but do not dramatically
exceed Eddington, but many systems are significantly below Eddington, perhaps
due to the "intermittency" of star formation. Better constraints on the
dust-to-gas ratio and the CO- and HCN-to-H2 conversion factors are needed to
make a definitive assessment of radiation pressure as a feedback mechanism.Comment: To appear in "Conditions and impact of star formation: New results
with Herschel and beyond", Proceedings of the 5th Zermatt ISM symposium. 2
pages, 2 figure

### Quantum Fluctuations of Radiation Pressure

Quantum fluctuations of electromagnetic radiation pressure are discussed. We
use an approach based on the quantum stress tensor to calculate the
fluctuations in velocity and position of a mirror subjected to electromagnetic
radiation. Our approach reveals that radiation pressure fluctuations are due to
a cross term between vacuum and state dependent terms in a stress tensor
operator product. Thus observation of these fluctuations would entail
experimental confirmation of this cross term. We first analyze the pressure
fluctuations on a single, perfectly reflecting mirror, and then study the case
of an interferometer. This involves a study of the effects of multiple bounces
in one arm, as well as the correlations of the pressure fluctuations between
arms of the interferometer. In all cases, our results are consistent with those
previously obtained by Caves using different mehods.Comment: 23 pages, 3 figures, RevTe

### Measurement of Radio-Frequency Radiation Pressure

We perform measurements of the radiation pressure of a radio-frequency (RF)
electromagnetic field which may lead to a new SI-traceable power calibration.
There are several groups around the world investigating methods to perform more
direct SI traceable measurement of RF power (where RF is defined to range from
100s of MHz to THz). A measurement of radiation pressure offers the possibility
for a power measure traceable to the kilogram and to Planck's constant through
the redefined SI. Towards this goal, we demonstrate the ability to measure the
radiation pressure/force carried in a field at 15~GHz.Comment: 2 pages 4 figure

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