122695218
TOPOLOGICAL TERM OF THE ANTIFERROMAGNETIC HEISENBERG MODEL IN 2+1 DIMENSION
It is shown in this note that the two different ways2,4 of introducing the topological term in the discussion of the spin 1/2 antiferromagnetic Heisenberg model are identical to each other.
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.
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.
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.
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.
117593411
Gravitational Radiation and Electron‐Cyclotron Masers from Ultra‐Compact Double Degenerate Binaries
The compactness of short‐period white‐dwarf binaries allows strong electro‐magnetic interaction between their component stars. For systems with a magnetic white dwarf a large e.m.f can be generated via unipolar induction, and it drives the flows of electric currents between the two white dwarfs. The electro‐magnetic interaction between the white dwarfs and the tidal interaction between the orbit leads to spin‐orbit coupling. This alters the orbital dynamics and evolution of the system. It also modifies the gravitational waves emitted from the system. The converging of current flows at the field foot points of the magnetic white dwarf may lead to the development of particle instabilities and the generation of electron‐cyclotron masers. The unipolar induction model of ultra‐compact white‐dwarf binaries is also applicable to white‐dwarf planetary systems. The model predicts electron‐cyclotron masers from white‐dwarf planetary systems, and the masers provide a useful mean for the study of ‘dead’ solar systems.
118980202
XMM-Newton observations of the ultra-compact binary RX J1914+24
We present XMM‐Newton observations of the 569-s-period system RX J1914+24 (V407 Vul). This period is believed to represent the binary orbital period making it an ultracompact binary system. By comparing the phase of the rise to maximum X-ray flux at various epochs (this includes observations made using ROSAT, ASCA and Chandra )w efind that the system is spinning up at a rate of 3.17 ± 0.07 × 10 −12 ss −1 .W efind that the spectra soften as the X-ray flux declines towards the off-phase of the 569-s period. Further, the spectra are best fitted by an absorbed blackbody component together with a broad emission feature around 0.59 keV. This emission feature is most prominent at the peak of the on-phase. We speculate on its origin. Ke yw ords: binaries: general — stars: individual: RX J1914+24 ‐ novae, cataclysmic variables ‐ X-rays: stars.
14517712
Discrete and diffuse X-ray emission in the nucleus and disk of the starburst spiral galaxy M83
We have studied the face-on, barred spiral M83 (NGC 5236) with Chandra. Eighty-one point sources are detected (above 3.5-sigma) in the ACIS S3 image: 15 of them are within the inner 16 arcsec region (starburst nucleus, resolved for the first time with Chandra), and 23 within the inner 60 arcsec (including the bar). The luminosity distributions of the sources in the inner 60 arcsec region (nucleus and stellar bar) is a single power law, which we interpret as due to continuous, ongoing star formation. Outside this inner region, there is a smaller fraction of bright sources, which we interpret as evidence of an aging population from a past episode of star formation. About 50% of the total emission in the nuclear region is unresolved; of this, about 70% can be attributed to hot thermal plasma, and we interpret the rest as due to unresolved point sources (eg, faint X-ray binaries). The unresolved X-ray emission also shows differences between the nuclear region and the spiral arms. In the nuclear region, the electron temperature of the thermal plasma is = 0.58 keV. In the spiral arms, the thermal component is at kT = 0.31 keV and a power-law component dominates at energies >~1 keV. The high abundance of C, Ne, Mg, Si and S with respect to Fe suggests that the interstellar medium is enriched and heated by core-collapse supernova explosions and winds from massive stars.
14472253
Chandra X-Ray Observations of the Spiral Galaxy M81
A Chandra X-Ray Observatory ACIS-S imaging observation is used to study the population of X-ray sources in the nearby Sab galaxy M81 (NGC 3031). A total of 177 sources are detected with 124 located within the D25 isophote to a limiting X-ray luminosity of � 3 � 10 36 ergs s � 1 . Source positions, count rates, luminosities in the 0.3–8.0 keV band, limiting optical magnitudes, and potential counterpart identifications are tabulated. Spectral and timing analysis of the 36 brightest sources are reported including the low-luminosity active galactic nucleus, SN 1993J, and the Einstein-discovered ultraluminous X-ray source X6. The nucleus accounts for � 86%, or 5 � 10 40 ergs s � 1 , of the total X-ray emission from M81. Its spectrum is well fitted by an absorbed power law with photon index 1:98 � 0:08, consistent with previous observations (average index 1.9). SN 1993J has softened and faded since its discovery. At an age of 2594 days, SN 1993J displayed a complex thermal spectrum from a reverse shock rich in Fe L and highly ionized Mg, Si, and S but lacking O. A hard X-ray component, emitted by a forward shock, is also present. X6 is spatially coincident with a stellar object with optical brightness and colors consistent with an O9–B1 main-sequence star. It is also coincident with a weak radio source with a flux density of � 95 lJy at � ¼ 3:6 cm. The continuum-dominated X-ray spectrum of X6 is most closely reproduced by a blackbody disk model suggesting the X-ray source is
16616301
Spin up in RX J0806+15: the shortest period binary
RX J0806+15 has recently been identified as the binary system with the shortest known orbital period. We present a series of observations of RX J0806+15, including new optical observations taken one month apart. Using these observations and archival data, we find that the period of this system is decreasing over time. Our measurements imply that f = 6.11 x 10 - 1 6 Hz s - 1 , which is in agreement with a rate expected from the gravitational radiation for two white dwarfs orbiting at a given period. However, a smaller value off = 3.14 x 10 - 1 6 Hz s - 1 cannot be ruled out. Our result supports the idea that the 321.5-s period is the orbital period, that the system is the shortest period binary known so far and that it is one of the strongest sources of constant gravitational radiation in the sky. Furthermore, the decrease of the period strongly favours the unipolar inductor (or electric star) model rather than the accretion models.