153,070 research outputs found
Yibing Zhang, Piano
Piano Sonata Hob. XVI/50 / Joseph Haydn; Islamey op. 18 / Mily Balakirev; Piano Sonata No. 11 in A major, K. 331 / W. A. Mozart; Rigoletto de Verdi - Paraphrase de Concert, S434 / Franz Lisz
Calculated Momentum Dependence of Zhang-Rice States in Transition Metal Oxides
Using a combination of local density functional theory and cluster exact
diagonalization based dynamical mean field theory, we calculate many body
electronic structures of several Mott insulating oxides including undoped high
T_{c} materials. The dispersions of the lowest occupied electronic states are
associated with the Zhang-Rice singlets in cuprates and with doublets,
triplets, quadruplets and quintets in more general cases. Our results agree
with angle resolved photoemission experiments including the decrease of the
spectral weight of the Zhang--Rice band as it approaches k=0
An Instability-driven Dynamo for Gamma Ray Bursts
We show that an MHD-instability driven dynamo (IDD) operating in a hot
accretion disk is capable of generating energetically adequate magnetic flux
deposition rates above and below a mildly advective accretion disk structure.
The dynamo is driven by the magnetorotational instability (MRI) of a toroidal
field in a shear flow and is limited by the buoyancy of `horizontal' flux and
by reconnection in the turbulent medium. The efficiency of magnetic energy
deposition is estimated to be comparable to the neutrino losses although an MHD
collimation mechanism may deem this process a more viable alternative to
neutrino-burst-driven models of gamma ray bursts.Comment: 4 pages, no figures, to appear in Proc. of the 10^th Annual Maryland
October Astrophysics Conference: "Cosmic Explosions". Eds. S. S. Holt and W.
W. Zhang (AIP Press) (2nd revision AIP LaTex, extended text and equations
Current Issues
Cosmic explosions are observed in many astrophysical environments. They range
in scale from hydromagnetic instabilities in the terrestrial magnetotail and
solar ``nanoflares'' to cosmological gamma ray bursts, supernovae and the
protracted intervals of nuclear activity that produce the giant quasars and
radio galaxies. There are many parallels in the analyses of the explosion sites
that are highlighted at this workshop, specifically stellar coronae, accretion
disks, supernovae and compact objects. In this introductory talk, some general
issues are discussed and some more specific questions relating to the
individual sites are raised.Comment: To appear in Cosmic Explosions: Proc. 10th Maryland Conference on
Astrophysics. Ed. S. Holt and W. Zhang AI
New Models for X-Ray Synchrotron Radiation from the Remnant of Supernova 1006 AD
Galactic cosmic rays up to energies of around 10^15 eV are assumed to
originate in supernova remnants (SNRs). The shock wave of a young SNR like SN
1006 AD can accelerate electrons to energies greater than 1 TeV, where they can
produce synchrotron radiation in the X-ray band. A new model (SRESC) designed
to model synchrotron X-rays from Type Ia supernovae can constrain values for
the magnetic-field strength and electron scattering properties, with
implications for the acceleration of the unseen ions which dominate the
cosmic-ray energetics. New observations by ASCA, ROSAT, and RXTE have provided
enormously improved data, which now extend to higher X-ray energies. These data
allow much firmer constraints. We will describe model fits to these new data on
SN 1006 AD, emphasizing the physical constraints that can be placed on SNRs and
on the cosmic-ray acceleration process.Comment: 10 pages, 2 figures. to appear in "Cosmic Explosions", proceeding of
the 10th Annual October Astrophysics Conference (ed. S.S. Holt and W. W.
Zhang) LaTex aipproc.st
Multiwavelength analysis as a probe of accretion and radiative processes in LINERs
We study the multiwavelength properties of an optically selected sample of
Low Ionization Nuclear Emission-line Regions (LINERs), in an attempt to
determine the accretion mechanism powering their central engine. We show how
their X-ray spectral characteristics, and their spectral energy distribution
compare to luminous AGN, and briefly discuss their connection to their less
massive counter-parts galactic black-hole X-ray binaries.Comment: 2 Pages. Proceedings of IAUS 290 "Feeding Compact Objects: Accretion
on All Scales", C. M. Zhang, T. Belloni, M. Mendez & S. N. Zhang (eds.
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