Search results for "GRAVITATION"
showing 10 items of 743 documents
Reply to Comment on Measurement of quantum states of neutrons in the Earth's gravitational field
2003
Physical review / D 68(10), 108702 (2003). doi:10.1103/PhysRevD.68.108702
Gauge-invariant Non-spherical Metric Perturbations of Schwarzschild Black-Hole Spacetimes
2005
The theory of gauge-invariant non-spherical metric perturbations of Schwarzschild black hole spacetimes is now well established. Yet, as different notations and conventions have been used throughout the years, the literature on the subject is often confusing and sometimes confused. The purpose of this paper is to review and collect the relevant expressions related to the Regge-Wheeler and Zerilli equations for the odd and even-parity perturbations of a Schwarzschild spacetime. Special attention is paid to the form they assume in the presence of matter-sources and, for the two most popular conventions in the literature, to the asymptotic expressions and gravitational-wave amplitudes. Besides…
A novel cooling scheme for antiprotons
2006
We propose a novel technique which uses laser-cooled negative osmium ions for sympathetic cooling of antiprotons. Temperatures down to the sub-millikelvin range might be achievable. These antiprotons could be used to form antihydrogen at ultra-cold temperatures, thus allowing efficient magnetic trapping of antihydrogen for high-resolution laser spectroscopy. Antihydrogen at sub-millikelvin temperatures might also enable first direct measurements of the gravitational acceleration of antimatter. Currently, no other technique exists which allows the cooling of large numbers of antiprotons to temperatures below that of the surrounding trap.
A Fast and Very Accurate Approach to the Computation of Microlensing Magnification Patterns Based on Inverse Polygon Mapping
2006
A new method of calculating microlensing magnification patterns is proposed that is based on the properties of the backward gravitational lens mapping of a lattice of polygonal cells defined at the image plane. To a first-order approximation, the local linearity of the transformation allows us to compute the contribution of each image-plane cell to the magnification by apportioning the area of the inverse image of the cell (transformed cell) among the source-plane pixels covered by it. Numerical studies in the κ = 0.1-0.8 range of mass surface densities demonstrate that this method (provided with an exact algorithm for distributing the area of the transformed cells among the source-plane pi…
Integrability of J f and 1∕J f
2013
In this chapter we study the optimal degree of integrability of J f and 1∕J f for mappings of finite distortion. As an application of our estimates we show that some sets are removable singularities for mappings with exponentially integrable distortion.
Finitely determined singularities of ruled surfaces in 3
2009
AbstractWe study local singularities of ruled surfaces in 3. We show that any map germ f : (2, 0) → (3, 0) with a simple singularity is -equivalent to a ruled surface. Moreover, we give a topological classification of -finitely determined singularities of ruled surfaces and show that there are just eleven topological classes.
A Study of the Correlation between the Amplification of the Fe Kα Line and the X‐Ray Continuum of Quasars due to Microlensing
2006
The observed enhancement of the Fe Kα line in three gravitationally lensed QSOs (MG J0414+0534, QSO 2237+0305, and H1413+117) is interpreted in terms of microlensing, even when equivalent X-ray continuum amplification is not observed. In order to interpret these observations, first we studied the effects of microlensing on quasar spectra produced by a straight fold caustic crossing over a standard relativistic accretion disk. The disk emission was analyzed using the ray-tracing method, considering Schwarzschild and Kerr metrics. When the emission is separated into two regions (an inner disk corresponding to the Fe Kα line and an outer annulus corresponding to the continuum, or vice versa), …
Measuring Microlensing using Spectra of Multiply Lensed Quasars
2012
We report on a program of spectroscopic observations of gravitationally-lensed QSOs with multiple images. We seek to establish whether microlensing is occurring in each QSO image using only single-epoch observations. We calculate flux ratios for the cores of emission lines in image pairs to set a baseline for no microlensing. The offset of the continuum flux ratios relative to this baseline yields the microlensing magnification free from extinction, as extinction affects the continuum and the lines equally. When we find chromatic microlensing, we attempt to constrain the size of the QSO accretion disk. SDSSJ1004+4112 and HE1104-1805 show chromatic microlensing with amplitudes $0.2< |\Delta …
Quantum motion of a neutron in a wave-guide in the gravitational field
2006
We study theoretically the quantum motion of a neutron in a horizontal waveguide in the gravitational field of the Earth. The waveguide in question is equipped with a mirror below and a rough surface absorber above. We show that such a system acts as a quantum filter, i.e. it effectively absorbs quantum states with sufficiently high transversal energy but transmits low-energy states. The states transmitted are determined mainly by the potential well formed by the gravitational field of the Earth and the mirror. The formalism developed for quantum motion in an absorbing waveguide is applied to the description of the recent experiment on the observation of the quantum states of neutrons in th…
Infrared singularities in one-loop amplitudes
2010
In this talk we discuss a purely numerical approach to next-to-leading order calculations in QCD. We present a simple formula, which provides a local infrared subtraction term for the integrand of a one-loop amplitude. In addition we briefly comment on local ultraviolet subtraction terms and on the required deformation of the contour of integration.