44,278 research outputs found
Decomposition of Triebel-Lizorkin and Besov spaces in the context of Laguerre expansions
A pair of dual frames with almost exponentially localized elements (needlets)
are constructed on \RR_+^d based on Laguerre functions. It is shown that the
Triebel-Lizorkin and Besov spaces induced by Laguerre expansions can be
characterized in terms of respective sequence spaces that involve the needlet
coefficients.Comment: 42 page
Mapping warm molecular hydrogen with Spitzer's Infrared Array Camera (IRAC)
Photometric maps, obtained with Spitzer's Infrared Array Camera (IRAC), can
provide a valuable probe of warm molecular hydrogen within the interstellar
medium. IRAC maps of the supernova remnant IC443, extracted from the Spitzer
archive, are strikingly similar to spectral line maps of the H2 pure rotational
transitions that we obtained with the Infrared Spectrograph (IRS) instrument on
Spitzer. IRS spectroscopy indicates that IRAC Bands 3 and 4 are indeed
dominated by the H2 v=0-0 S(5) and S(7) transitions, respectively. Modeling of
the H2 excitation suggests that Bands 1 and 2 are dominated by H2 v=1-0 O(5)
and v=0-0 S(9). Large maps of the H2 emission in IC433, obtained with IRAC,
show band ratios that are inconsistent with the presence of gas at a single
temperature. The relative strengths of IRAC Bands 2, 3, and 4 are consistent
with pure H2 emission from shocked material with a power-law distribution of
gas temperatures. CO vibrational emissions do not contribute significantly to
the observed Band 2 intensity. Assuming that the column density of H2 at
temperatures T to T+dT is proportional to T raised to the power -b for
temperatures up to 4000 K, we obtained a typical estimate of 4.5 for b. The
power-law index, b, shows variations over the range 3 to 6 within the set of
different sight-lines probed by the maps, with the majority of sight-lines
showing b in the range 4 to 5. The observed power-law index is consistent with
the predictions of simple models for paraboloidal bow shocks.Comment: 27 pages, including 11 figures. Accepted for publication in Ap
Symmetry protected fractional Chern insulators and fractional topological insulators
In this paper we construct fully symmetric wavefunctions for the
spin-polarized fractional Chern insulators (FCI) and time-reversal-invariant
fractional topological insulators (FTI) in two dimensions using the parton
approach. We show that the lattice symmetry gives rise to many different FCI
and FTI phases even with the same filling fraction (and the same
quantized Hall conductance in FCI case). They have different
symmetry-protected topological orders, which are characterized by different
projective symmetry groups. We mainly focus on FCI phases which are realized in
a partially filled band with Chern number one. The low-energy gauge groups of a
generic FCI wavefunctions can be either or
the discrete group , and in the latter case the associated low-energy
physics are described by Chern-Simons-Higgs theories. We use our construction
to compute the ground state degeneracy. Examples of FCI/FTI wavefunctions on
honeycomb lattice and checkerboard lattice are explicitly given. Possible
non-Abelian FCI phases which may be realized in a partially filled band with
Chern number two are discussed. Generic FTI wavefunctions in the absence of
spin conservation are also presented whose low-energy gauge groups can be
either or . The constructed wavefunctions
also set up the framework for future variational Monte Carlo simulations.Comment: 24 pages, 13 figures, published versio
CO observations and investigation of triggered star formation towards N10 infrared bubble and surroundings
We studied the environment of the dust bubble N10 in molecular emission.
Infrared bubbles, first detected by the GLIMPSE survey at 8.0 m, are ideal
regions to investigate the effect of the expansion of the HII region on its
surroundings eventual triggered star formation at its borders. In this work, we
present a multi-wavelength study of N10. This bubble is especially interesting
as infrared studies of the young stellar content suggest a scenario of ongoing
star formation, possibly triggered, on the edge of the HII region. We carried
out observations of CO(1-0) and CO(1-0) emission at PMO 13.7-m
towards N10. We also analyzed the IR and sub-mm emission on this region and
compare those different tracers to obtain a detailed view of the interaction
between the expanding HII region and the molecular gas. We also estimated the
parameters of the denser cold dust condensation and of the ionized gas inside
the shell. Bright CO emission was detected and two molecular clumps were
identified, from which we have derived physical parameters. We also estimate
the parameters for the densest cold dust condensation and for the ionized gas
inside the shell. The comparison between the dynamical age of this region and
the fragmentation time scale favors the "Radiation-Driven Implosion" mechanism
of star formation. N10 reveals to be specially interesting case with gas
structures in a narrow frontier between HII region and surrounding molecular
material, and with a range of ages of YSOs situated in region indicating
triggered star formation.Comment: Version 2 - Submmited to ApJ (under review
Measurement of nuclear effects in neutrino interactions with minimal dependence on neutrino energy
We present a phenomenological study of nuclear effects in neutrino
charged-current interactions, using transverse kinematic imbalances in
exclusive measurements. Novel observables with minimal dependence on neutrino
energy are proposed to study quasielastic scattering, and especially resonance
production. They should be able to provide direct constraints on nuclear
effects in neutrino- and antineutrino-nucleus interactions.Comment: 7 pages, 9 figures, accepted version by PR
Experimental position-time entanglement with degenerate single photons
We report an experiment in which two-photon interference occurs between
degenerate single photons that never meet. The two photons travel in opposite
directions through our fibre-optic interferometer and interference occurs when
the photons reach two different, spatially separated, 2-by-2 couplers at the
same time. We show that this experiment is analogous to the conventional
Franson-type entanglement experiment where the photons are entangled in
position and time. We measure wavefunction overlaps for the two photons as high
as 94 3%.Comment: Updated to published version, new fig. 4., corrected typo
Heart enhancers with deeply conserved regulatory activity are established early in zebrafish development.
During the phylotypic period, embryos from different genera show similar gene expression patterns, implying common regulatory mechanisms. Here we set out to identify enhancers involved in the initial events of cardiogenesis, which occurs during the phylotypic period. We isolate early cardiac progenitor cells from zebrafish embryos and characterize 3838 open chromatin regions specific to this cell population. Of these regions, 162 overlap with conserved non-coding elements (CNEs) that also map to open chromatin regions in human. Most of the zebrafish conserved open chromatin elements tested drive gene expression in the developing heart. Despite modest sequence identity, human orthologous open chromatin regions recapitulate the spatial temporal expression patterns of the zebrafish sequence, potentially providing a basis for phylotypic gene expression patterns. Genome-wide, we discover 5598 zebrafish-human conserved open chromatin regions, suggesting that a diverse repertoire of ancient enhancers is established prior to organogenesis and the phylotypic period
On The Orbital Evolution of Jupiter Mass Protoplanet Embedded in A Self-Gravity Disk
We performed a series of hydro-dynamic simulations to investigate the orbital
migration of a Jovian planet embedded in a proto-stellar disk. In order to take
into account of the effect of the disk's self gravity, we developed and adopted
an \textbf{Antares} code which is based on a 2-D Godunov scheme to obtain the
exact Reimann solution for isothermal or polytropic gas, with non-reflecting
boundary conditions. Our simulations indicate that in the study of the runaway
(type III) migration, it is important to carry out a fully self consistent
treatment of the gravitational interaction between the disk and the embedded
planet. Through a series of convergence tests, we show that adequate numerical
resolution, especially within the planet's Roche lobe, critically determines
the outcome of the simulations. We consider a variety of initial conditions and
show that isolated, non eccentric protoplanet planets do not undergo type III
migration. We attribute the difference between our and previous simulations to
the contribution of a self consistent representation of the disk's self
gravity. Nevertheless, type III migration cannot be completely suppressed and
its onset requires finite amplitude perturbations such as that induced by
planet-planet interaction. We determine the radial extent of type III migration
as a function of the disk's self gravity.Comment: 19 pages, 13 figure
From Jeff=1/2 insulator to p-wave superconductor in single-crystal Sr2Ir1-xRuxO4 (0 < x< 1)
Sr2IrO4 is a magnetic insulator assisted by strong spin-orbit coupling (SOC)
whereas the Sr2RuO4 is a p-wave superconductor. The contrasting ground states
have been shown to result from the critical role of the strong SOC in the
iridate. Our investigation of structural, transport, and magnetic properties
reveals that substituting 4d Ru4+ (4d4) ions for 5d Ir4+(5d5) ions in Sr2IrO4
directly adds holes to the t2g bands, reduces the SOC and thus rebalances the
competing energies in single-crystal Sr2Ir1-xRuxO4. A profound effect of Ru
doping driving a rich phase diagram is a structural phase transition from a
distorted I41/acd to a more ideal I4/mmm tetragonal structure near x=0.50 that
accompanies a phase transition from an antiferromagnetic-insulating state to a
paramagnetic-metal state. We also make a comparison drawn with Rh doped
Sr2IrO4, highlighting important similarities and differences.Comment: 18 pages,7 figure
Origin of the X-ray Emission in the Nuclei of FR Is
We investigate the X-ray origin in FRIs using the multi-waveband high
resolution data of eight FR I sources, which have very low Eddington ratios. We
fit their multi-waveband spectrum using a coupled accretion-jet model. We find
that X-ray emission in the source with the highest L_X (~1.8*10^-4 L_Edd) is
from the advection-dominated accretion flow (ADAF). Four sources with moderate
L_X(~several*10^-6 L_Edd) are complicated. The X-ray emission of one FR I is
from the jet, and the other three is from the sum of the jet and ADAF. The
X-ray emission in the three least luminous sources (L_X<1.0*10^-6L_Edd) is
dominated by the jet. These results roughly support the predictions of Yuan and
Cui(2005) where they predict that when the X-ray luminosity of the system is
below a critical value, the X-radiation will not be dominated by the emission
from the ADAF any longer, but by the jet. We also find that the accretion rates
in four sources must be higher than the Bondi rates, which implies that other
fuel supply (e.g., stellar winds) inside the Bondi radius should be important.Comment: 6 pages. To published in Journal of Physics, in proceedings of "The
Universe under the Microscope - Astrophysics at High Angular Resolution" (Bad
Honnef, Germany, April 2008), eds. R. Schoedel, A. Eckart, S. Pfalzner, and
E. Ro
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