13909552
Total Variation and Variational Symplectic-Energy- Momentum integrators
A discrete total variation calculus with variable time steps is presented in this letter. Using this discrete variation calculus, we generalize Lee’s discrete mechanics and derive variational symplecticenergy-momentum integrators by Kane, Marsden and Ortiz. The relationship among discrete total variation, Lee’s discrete mechanics and Kane-Marsden-Ortiz’s integrators is explored.
119356933
Super-Yangian Y( gl(1|1)) and its oscillator realization
On the basis of graded RTT formalism, the defining relation of the super-Yangian is derived and its oscillator realization is constructed.
124010822
ASSOCIATIVITY OF REPRESENTATIONS AND COCYCLES OF GAUGE GROUPS
It is shown that the consistency of certain representations of group requires a mod Z-cocycle condition which leads to some topological quantization constants in corresponding anomalous algebraic relations, such as anomalous commutators and anomalous Jacobi identities. It should be pointed out that the mod Z-cocycles for gauge groups could be constructed by means of the generalized secondary characteristic classes.
123950095
Global Solutions of Einstein–Dirac Equation on the Conformal Space*
The difference between the Riemann and Lorentz spinor manifolds of four dimensions is that the Dirac operator of the former is elliptic and that of the latter is hyperbolic. Moreover the spinor group of the former is a compact group and that of the latter is a noncompact group, which is isomorphic to SL(2,C). Hence the results and their interpretation coming from the two theories would be different. In this short note we study only the Lorentz spinor manifold and, especially, the solutions of Einstein-Dirac equations on the conformal space, which is closely related to the AdS/CFT correspondence.
123836451
ANOMALIES OF ARBITRARY GAUGE GROUP AND ITS REDUCTION GROUP, EINSTEIN AND LORENTZ ANOMALIES
Based upon the properties of the characteristic classes and their Chern-Simons secondary characteristic classes, the "Abelian" anomalies in , the Euler-Heisenberg effective actions in , as well as the non-Abelian anomalies in for arbitrary gauge group and its reduction subgroup have been investigated thoroughly and the application to the gravitational anomalies is made. It is shown that the "Abelian" anomalies of such groups are equal to each other, their Eu1er-Heisenberg actions are also closely related to each, other, and their non-Abelian anomalies are also equivalent if their common generating functional can be taken as a counter-term. For the gravitational anomalies we present the common generating functional for both non-Abelian Einstein and Lorentz anomalies in and show the relationship between them.
124820814
R-Matrices for Some Inhomogeneous Quantum Groups*
In this paper, some new generalized inhomogeneous quantum groups corresponding to the homogeneous multiparameter quantum groups are constructed, furthermore, the -matrices for these inhomogeneous quantum groups are found.
83259
Measuring the Motion of the Black Hole in GRO J1655–40
We report optical spectroscopic observations of the low-mass X-ray binary GRO J1655-40 during outbursts in 1994 August-September and in 1996 June. The spectra show emission and absorption lines from the accretion disk surrounding the X-ray source, which have enabled us to measure the motion of the black hole candidate in this system. It is the first time among black hole candidates that an emission-line radial velocity curve is seen in phase with the expected motion of the primary. The projected radial velocity semiamplitude determined for the primary (KX = 76.2±7.5 km s-1), combined with estimates of the projected radial velocity semiamplitude of the companion star from previous observations (KC=228.2±3.0 km s-2), yields a 95% confidence limit, derived purely from kinematics, of MX > 5.1 M☉ for the mass of the compact object in GRO J1655-40, confirming its black hole nature.
2064814
Ultra-Short Period Double-Degenerate Binaries
We review the current observational status of the ROSAT sources RX J1914.4+2456 and RX J0806.3+1527, and the evidence that these are ultra-short period (<10min) binary systems. We argue that an Intermediate Polar interpretation can be ruled out, that they are indeed compact binaries with a degenerate secondary, and that the period seen in the X-ray and optical is the orbital period. A white dwarf primary is preferred, but a neutron star cannot be excluded. We examine the capability of the three current double-degenerate models (Polar, Direct Accretor and Electric Star) to account for the observational characteristics of these systems. All models have difficulties with some aspects of the observations, but none can be excluded with confidence at present. The Electric Star model provides the best description, but the lifetime of this phase requires further investigation. These ultra-short period binaries will be strong gravitational wave emitters in the LISA bandpass, and because of their known source properties will be important early targets for gravitational wave studies.
117001120
Finding Periods in High Mass X-Ray Binaries
This is a call for amateur astronomers who have the equipment and experience for producing high quality photometry to contribute to a program of finding periods in the optical light curves of high mass X-ray binaries (HMXB). HMXBs are binary stars in which the lighter star is a neutron star or a black hole and the more massive star is an O type supergiant or a Be type main sequence star. Matter is transferred from the ordinary star to the compact object and X-rays are produced as the the gravitational energy of the accreting gas is converted into light. HMXBs are very bright, many are brighter than 10th magnitude, and so make perfect targets for experienced amateur astronomers with photometry capable CCD equipment coupled with almost any size telescope.
16762028
XMM-Newton optical monitor observations of LMC X-3
We study the optical counterpart of the black-hole X-ray binary LMC X-3, by using XMM-Newton/OM observations carried out during a low-hard X-ray state. We derive a better constraint for the temperature, mass and radius of the companion star, and we show that the star is likely to be a similar to B5 subgiant filling its Roche lobe. Taking into account the Effect of X-ray irradiation, we suggest a value f(M) approximate to 1.5 M. for the mass function in this system, lower than previously thought; we provide a more accurate lower limit to the mass of the compact object.
119085416
The First Chandra Field
Before the official first-light images, the Chandra X-ray Observatory obtained an X-ray image of the field to which its focal plane was first exposed. We describe this historic observation and report our study of the first Chandra field. Chandra's Advanced CCD Imaging Spectrometer (ACIS) detected 15 X-ray sources, the brightest being dubbed ''Leon X-1'' to honor the Chandra Telescope Scientist, Leon Van Speybroeck. Based upon our analysis of the X-ray data and spectroscopy at the European Southern Observatory (ESO; La Silla, Chile), we find that Leon X-1 is a Type-1 (unobscured) active galactic nucleus (AGN) at a redshift z = 0.3207. Leon X-1 exhibits strong Fe II emission and a broad-line Balmer decrement that is unusually flat for an AGN. Within the context of the Eigenvector-1 correlation space, these properties suggest that Leon X-1 may be a massive ({ge} 10{sup 9} M{sub {circle_dot}}) black hole, accreting at a rate approaching its Eddington limit.