26,913 research outputs found
Radio Emission from Pulsar Wind Nebulae without Surrounding Supernova Ejecta: Application to FRB 121102
In this paper, we propose a new scenario in which a rapidly-rotating
strongly-magnetized pulsar without any surrounding supernova ejecta produces
fast radio bursts (FRBs) repeatedly via some mechanisms, and meanwhile, an
ultra-relativistic electron/positron pair wind from the pulsar sweeps up its
ambient dense interstellar medium, giving rise to a non-relativistic pulsar
wind nebula (PWN). We show that the synchrotron radio emission from such a PWN
is bright enough to account for the recently-discovered persistent radio source
associated with the repeating FRB 121102 in reasonable ranges of the model
parameters. In addition, our PWN scenario is consistent with the non-evolution
of the dispersion measure inferred from all the repeating bursts observed in
four years.Comment: 6 pages, 1 figure, ApJ Letters in pres
An exactly solvable phase transition model: generalized statistics and generalized Bose-Einstein condensation
In this paper, we present an exactly solvable phase transition model in which
the phase transition is purely statistically derived. The phase transition in
this model is a generalized Bose-Einstein condensation. The exact expression of
the thermodynamic quantity which can simultaneously describe both gas phase and
condensed phase is solved with the help of the homogeneous Riemann-Hilbert
problem, so one can judge whether there exists a phase transition and determine
the phase transition point mathematically rigorously. A generalized statistics
in which the maximum occupation numbers of different quantum states can take on
different values is introduced, as a generalization of Bose-Einstein and
Fermi-Dirac statistics.Comment: 17 pages, 2 figure
Spin and Lattice Structure of Single Crystal SrFe2As2
We use neutron scattering to study the spin and lattice structure on single
crystals of SrFe2As2, the parent compound of the FeAs based superconductor
(Sr,K)Fe2As2. We find that SrFe2As2 exhibits an abrupt structural phase
transitions at 220K, where the structure changes from tetragonal with lattice
parameters c > a = b to orthorhombic with c > a > b. At almost the same
temperature, Fe spins in SrFe2As2 develop a collinear antiferromagnetic
structure along the orthorhombic a-axis with spin direction parallel to this
a-axis. These results are consistent with earlier work on the RFeAsO (R = rare
earth elements) families of materials and on BaFe2As2, and therefore suggest
that static antiferromagnetic order is ubiquitous for the parent compound of
these FeAs-based high-transition temperature superconductors.Comment: 14 pages with 4 figure
Spin Susceptibility of the Topological Superconductor UPt3 from Polarized Neutron Diffraction
Experiment and theory indicate that UPt3 is a topological superconductor in
an odd-parity state, based in part from temperature independence of the NMR
Knight shift. However, quasiparticle spin-flip scattering near a surface, where
the Knight shift is measured, might be responsible. We use polarized neutron
scattering to measure the bulk susceptibility with H||c, finding consistency
with the Knight shift but inconsistent with theory for this field orientation.
We infer that neither spin susceptibility nor Knight shift are a reliable
indication of odd-parity
Doping evoluton of antiferromagnetic order and structural distortion in LaFeAsOF
We use neutron scattering to study the structural distortion and
antiferromagnetic (AFM) order in LaFeAsOF as the system is doped
with fluorine (F) to induce superconductivity. In the undoped state, LaFeAsO
exhibits a structural distortion, changing the symmetry from tetragonal (space
group ) to orthorhombic (space group ) at 155 K, and then
followed by an AFM order at 137 K. Doping the system with F gradually decreases
the structural distortion temperature, but suppresses the long range AFM order
before the emergence of superconductivity. Therefore, while superconductivity
in these Fe oxypnictides can survive in either the tetragonal or the
orthorhombic crystal structure, it competes directly with static AFM order.Comment: reference update
Structural and resistance switching properties of ZnO₃/ SrTiO/GaAs heterostructure grown by laser molecular beam epitaxy
Author name used in this publication: J. Y. Dai2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
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