Radiation from hot spots orbiting an extreme Reissner-Nordström black hole

The general-relativistic effects of an extreme Reissner-Nordström black hole on the flux of radiation emitted by a hot spot orbiting the hole with a thin accretion disk are investigated. The light curves, the redshift factor, and the solid angle against the spot orbit position are given. The results are then compared with those of a spot orbiting a Schwarzschild black hole.     

General integrable problems of classical mechanics

Several classical problems of mechanics are shown to be integrable for the special systems of coupled rigid bodies, introduced in this work and calledC ^k -central configurations. It is proven that dynamics of an arbitraryC ^k -central configuration in a Newtonian gravitational field with an arbitrary quadratic potential is integrable in the Liouville sense and in the theta-functions of Riemann surfaces. Hidden symmetry of the inertial dynamics of these configurations is disclosed and reductions of the Lagrange equations to the Euler equations on Lie coalgebras are obtained. Reductions and integrable cases of a heavyC ^k -central configuration rotation around a fixed point are indicated. Separation of rotations of a space station type orbiting system, being aC ^k -central configuration of rigid bodies, is proven. This result leads to the possibility of the independent stabilization of rotations of the rigid bodies in such orbiting configurations.Supported by the Ministry of Colleges and Universities of Ontario and the Natural Sciences and Engineering Research Council of Canada     

Earth-to-deep-space optical communications system with adaptive tilt and scintillation correction by use of near-Earth relay mirrors

Performance of an Earth-to-deep-space optical telecommunications system is degraded by distortion of the beam as it propagates through the turbulent atmosphere. Conventional approaches to correcting distortions, based on natural or artificial guide stars, have practical difficulties or are not adequate for correction of distortions, which are important for Earth-to-deep-space optical links. A beam-relay approach that overcomes these difficulties is discussed. A downward-directed laser near an orbiting relay mirror provides a reference for atmospheric correction. Adaptive optics at the ground station compensate the uplink beam so that after it passes through the atmosphere uplink propagation effects are removed. The orbiting mirror then directs the corrected beam to the distant spacecraft.     

温度场对动涡旋盘应力与应变的影响

针对不同的温度场,运用有限元分析软件ANSYS对汽车空调涡旋压缩机的动涡旋盘进行了应力与应变的模拟和研究。计算结果表明,温度载荷对涡旋盘的应力和应变有着重要影响。其中,非均匀温度场会导致涡旋盘的涡旋齿产生较大应力与应变,涡旋齿断裂故障发生的概率较大。     

Bound and unbound rovibrational states of the methane-argon dimer

ABSTRACT

Peculiarities of the intermolecular rovibrational quantum dynamics of the methane-argon complex are studied using a new, ab initio potential energy surface [Y.N. Kalugina, S.E. Lokshtanov, V.N. Cherepanov, and A.A. Vigasin, J. Chem. Phys. 144, 054304 (2016)], variational rovibrational computations, and detailed symmetry considerations within the molecular symmetry group of this floppy complex as well as within the point groups corresponding to the local minimum structures. The computed (ro)vibrational states up to and beyond the dissociation asymptote are characterised using two limiting models: the rigidly rotating molecule's model and the coupled-rotor model of the rigidly rotating methane and an argon atom orbiting around it.     

Accurate evolutions of orbiting black-hole binaries without excision

We present a new algorithm for evolving orbiting black-hole binaries that does not require excision or a corotating shift. Our algorithm is based on a novel technique to handle the singular puncture conformal factor. This system, based on the Baumgarte-Shapiro-Shibata-Nakamura formulation of Einstein's equations, when used with a "precollapsed" initial lapse, is nonsingular at the start of the evolution and remains nonsingular and stable provided that a good choice is made for the gauge. As a test case, we use this technique to fully evolve orbiting black-hole binaries from near the innermost stable circular orbit regime. We show fourth-order convergence of waveforms and compute the radiated gravitational energy and angular momentum from the plunge. These results are in good agreement with those predicted by the Lazarus approach.     

Strains and rigidity in black-hole fields

In General Relativity a body is said to be rigid when it suffers no deformations, namely when the relative acceleration of any pair of its neighbouring elements vanishes identically. Here we apply this criterion to a system orbiting a Schwarzschild and Kerr black hole and calculate the strains which the body has to sustain in order to avoid deformation. We then discuss the relations between our results and the physical measurements which can be performed in orbiting frames and find that the only measurement of strains leads to ambiguous information.     

Geometrical theory of diffracted rays, orbiting and complex rays

In this article, the ray tracing method is studied beyond the classical geometrical theory. The trajectories are here regarded as geodesics in a Riemannian manifold, whose metric and topological properties are those induced by the refractive index (or, equivalently, by the potential). First, we derive the geometrical quantization rule, which is relevant to describe the orbiting bound-states observed in molecular physics. Next, we derive properties of the diffractive rays, regarded here as geodesics in a Riemannian manifold with boundary. A particular attention is devoted to the following problems: (i) modification of the classical stationary phase method suited to a neighborhood of a caustic; (ii) derivation of the connection formulas which enable one to obtain the uniformization of the classical eikonal approximation by patching up geodesic segments crossing the axial caustic; (iii) extension of the eikonal equation to mixed hyperbolic-elliptic systems, and generation of complex-valued rays in the shadow of the caustic. By these methods, we can study creeping waves in diffractive scattering, describe the orbiting resonances present in molecular scattering beside the orbiting bound-states, and, finally, describe the generation of evanescent waves, which are relevant in the nuclear rainbow. “Lumen propagatur seu diffunditur non solum directe, refracte ac reflexe, sed etiam alio quodam quarto modo, diffracte.” Francesco Maria Grimaldi (Physico-Mathesis de lumine, coloribus, et iride, aliisque adnexis libri duo; Bononiae 1665)     

Growth of Harmonic Perturbations of an Electron Shell Orbiting a Positively-Charged Wire (Orbitron)

The negative-mass instability of a cylindrical shell of electrons orbiting a positively-charged wire was studied. The harmonics of the orbital frequency are found to grow faster than the fundamental, with a growth constant proportional to the square root of the harmonic number.     

Charge-magnetic-dipole bound states using the Klein-Gordon equation

We investigate bound states of a composite system consisting of a charged particle orbiting a neutral, stationary magnetic dipole. We find all bound states are metastable and none exist with angular momentum less than eleven. Our calculations is performed in two space dimensions.     

Searching for gravitational waves from rotating neutron stars

Rotating neutron stars are one of the important sources of gravitational waves (GW) for the ground based as well as space based detectors. Since the waves are emitted continuously, the source is termed as a continuous gravitational wave (CGW) source. The expected weakness of the signal requires long integration times (∼year). The data analysis problem involves tracking the phase coherently over such large integration times, which makes it the most computationally intensive problem among all GW sources envisaged. In this article, the general problem of data analysis is discussed, and more so, in the context of searching for CGW sources orbiting another companion object. The problem is important because there are several pulsars, which could be deemed to be CGW sources orbiting another companion star. Differential geometric techniques for data analysis are described and used to obtain computational costs. These results are applied to known systems to assess whether such systems are detectable with current (or near future) computing resources.     

Floating and sinking: the imprint of massive scalars around rotating black holes

We study the coupling of massive scalar fields to matter in orbit around rotating black holes. It is generally expected that orbiting bodies will lose energy in gravitational waves, slowly inspiraling into the black hole. Instead, we show that the coupling of the field to matter leads to a surprising effect: because of superradiance, matter can hover into "floating orbits" for which the net gravitational energy loss at infinity is entirely provided by the black hole's rotational energy. Orbiting bodies remain floating until they extract sufficient angular momentum from the black hole, or until perturbations or nonlinear effects disrupt the orbit. For slowly rotating and nonrotating black holes floating orbits are unlikely to exist, but resonances at orbital frequencies corresponding to quasibound states of the scalar field can speed up the inspiral, so that the orbiting body sinks. These effects could be a smoking gun of deviations from general relativity.     

Thin cylindrical shells in general relativity

The sources of static cylindrically symmetric fields in the form of thin cylindrical shells are studied. The results are compared (in the case of the thin shell consisting of orbiting particles with the result of Raychaudhuri and Som). A special solution is also found, represented by a collapsing shell which is the source of the static field.     

Left-right asymmetry and orbiting valence quarks in polarized protons and antiprotons

It is shown that the asymmetry observed in the recent single-spin large-x _F inclusive pion production experiments at high-energies should be considered as a strong indication for the existence of orbiting valence quarks in polarized protons and antiprotons. The underlying physical picture in which orbiting valence quarks give rise to flavor-currents is discussed. The close connection between these currents and the measured quantities — in particular baryon's magnetic moment and the abovementioned asymmetry — is pointed out.     

Relativistic dynamics of spherical counter-rotating dust bodies

Spherically symmetric dust clusters, of the type first proposed by Einstein, are generalized to nonstationaxy cases. Particular attention is paid to a massive spherical shell of particles orbiting a central body, using a method developed by Israel. Shells provide comparisons with Schwarzschild test particles, and offer as well a simplified approach to continuously distributed clusters.     

Gravitomagnetic Effects

The paper summarizes the most important effects in Einsteinian gravitomagnetic fields related to propagating light rays, moving clocks and atoms, orbiting objects, and precessing spins. Emphasis is put onto the gravitational interaction of spinning objects. The gravitomagnetic field lines of a rotating or spinning object are given in analytic form.     

Nonstatic spherically symmetric space-times in Rosen's bimetric gravitation theory

Time dependent metrics, conformally equivalent to the static spherically symmetric metric, are considered. The one-body problem is investigated and some general conditions for accelerated and geometrically modified orbiting are obtained. The radial and nonradial null geodesics are investigated and it is shown that their differential equations are not modified by the conformal factor.     

Precession of Orbiting Gyroscope in Higher-Order Gravitational Field Caused by Rotating Body

The metric for a spinning massive object with any shape and composition is found by the use of linearized higher-order theory of gravitation. The geodesic and the Lense–Thirring precessions for an orbiting gyroscope in a general weak higher-order gravitational field are considered. The influences of the additional Yukawa forces included in the linearized higher-order gravitation on the precessions are investigated.     

Nuclear reactions in the 86Kr + 139La system at 710 MeV

Two distinct groups of reaction products are observed in the ⁸⁶Kr + ¹³⁹La system at 710 MeV. Partially damped events show an angular distribution peaked near the grazing angle while fully damped products exhibit a strongly forward-peaked angular distribution suggestive of nuclear orbiting.