42,755 research outputs found
Parsec-scale jet properties of the gamma-ray quasar 3C 286
The quasar 3C~286 is one of two compact steep spectrum sources detected by
the {\it Fermi}/LAT. Here, we investigate the radio properties of the
parsec(pc)-scale jet and its (possible) association with the -ray
emission in 3C~286. The Very Long Baseline Interferometry (VLBI) images at
various frequencies reveal a one-sided core--jet structure extending to the
southwest at a projected distance of 1 kpc. The component at the jet base
showing an inverted spectrum is identified as the core, with a mean brightness
temperature of ~K. The jet bends at about 600 pc (in
projection) away from the core, from a position angle of to
. Based on the available VLBI data, we inferred the proper motion
speed of the inner jet as mas yr (), corresponding to a jet speed of about at an inclination
angle of between the jet and the line of sight of the observer. The
brightness temperature, jet speed and Lorentz factor are much lower than those
of -ray-emitting blazars, implying that the pc-scale jet in 3C~286 is
mildly relativistic. Unlike blazars in which -ray emission is in
general thought to originate from the beamed innermost jet, the location and
mechanism of -ray emission in 3C~286 may be different as indicated by
the current radio data. Multi-band spectrum fitting may offer a complementary
diagnostic clue of the -ray production mechanism in this source.Comment: 9 pages, 4 figures, accept for publication in MNRA
Intruder level and deformation in the SD-pair shell model
The influence of the intruder level on nuclear deformation is studied within
the framework of the nucleon-pair shell model truncated to an SD-pair subspace.
The results suggest that the intruder level has a tendency to soften the
deformation and plays an important role in determining the onset of rotational
behavior.Comment: 2 input TeX files, 2 figures, submitted to Phys. Lett.
The non-compact elliptic genus: mock or modular
We analyze various perspectives on the elliptic genus of non-compact
supersymmetric coset conformal field theories with central charge larger than
three. We calculate the holomorphic part of the elliptic genus via a free field
description of the model, and show that it agrees with algebraic expectations.
The holomorphic part of the elliptic genus is directly related to an
Appell-Lerch sum and behaves anomalously under modular transformation
properties. We analyze the origin of the anomaly by calculating the elliptic
genus through a path integral in a coset conformal field theory. The path
integral codes both the holomorphic part of the elliptic genus, and a
non-holomorphic remainder that finds its origin in the continuous spectrum of
the non-compact model. The remainder term can be shown to agree with a function
that mathematicians introduced to parameterize the difference between mock
theta functions and Jacobi forms. The holomorphic part of the elliptic genus
thus has a path integral completion which renders it non-holomorphic and
modular.Comment: 13 page
Imaging and variability studies of CTA~102 during the 2016 January -ray flare
The -ray bright blazar CTA 102 is studied using imaging (new 15 GHz
and archival 43 GHz Very Long Baseline Array, VLBA data) and time variable
optical flux density, polarization degree and electric vector position angle
(EVPA) spanning between 2015 June 1 and 2016 October 1, covering a prominent
-ray flare during 2016 January. The pc-scale jet indicates expansion
with oscillatory features upto 17 mas. Component proper motions are in the
range 0.04 - 0.33 mas/yr with acceleration upto 1.2 mas followed by a slowing
down beyond 1.5 mas. A jet bulk Lorentz factor 17.5, position angle of
128.3 degrees, inclination angle 6.6 degrees and intrinsic half opening
angle 1.8 degrees are derived from the VLBA data. These inferences are
employed in a helical jet model to infer long term variability in flux density,
polarization degree, EVPA and a rotation of the Stokes Q and U parameters. A
core distance of = 22.9 pc, and a magnetic field
strength at 1 pc and the core location of 1.57 G and 0.07 G respectively are
inferred using the core shift method. The study is useful in the context of
estimating jet parameters and in offering clues to distinguish mechanisms
responsible for variability over different timescales.Comment: 20 pages, 7 figures, 3 tables; accepted for publication in Ap
Electron Delocalization in Gate-Tunable Gapless Silicene
The application of a perpendicular electric field can drive silicene into a
gapless state, characterized by two nearly fully spin-polarized Dirac cones
owing to both relatively large spin-orbital interactions and inversion symmetry
breaking. Here we argue that since inter-valley scattering from non-magnetic
impurities is highly suppressed by time reversal symmetry, the physics should
be effectively single-Dirac-cone like. Through numerical calculations, we
demonstrate that there is no significant backscattering from a single impurity
that is non-magnetic and unit-cell uniform, indicating a stable delocalized
state. This conjecture is then further confirmed from a scaling of conductance
for disordered systems using the same type of impurities.Comment: 6 pages, 3 figures, published versio
High-rate, high-fidelity entanglement of qubits across an elementary quantum network
We demonstrate remote entanglement of trapped-ion qubits via a
quantum-optical fiber link with fidelity and rate approaching those of local
operations. Two Sr qubits are entangled via the polarization
degree of freedom of two photons which are coupled by high-numerical-aperture
lenses into single-mode optical fibers and interfere on a beamsplitter. A novel
geometry allows high-efficiency photon collection while maintaining unit
fidelity for ion-photon entanglement. We generate remote Bell pairs with
fidelity at an average rate (success
probability ).Comment: v2 updated to include responses to reviewers, as published in PR
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