477 research outputs found
Topological Quantum Critical Points in the Extended Bose-Hubbard Model
The combination of topology and quantum criticality can give rise to an exotic mix of counterintuitive effects. Here, we show that unexpected topological properties take place in a paradigmatic strongly correlated Hamiltonian: the 1D extended Bose-Hubbard model. In particular, we reveal the presence of two distinct topological quantum critical points with localized edge states and gapless bulk excitations. Our results show that the topological critical points separate two phases, one topologically protected and the other topologically trivial, both characterized by a long-range ordered string correlation function. The long-range order persists also at the topological critical points and explains the presence of localized edge states protected by a finite charge gap. Finally, we introduce a superresolution quantum gas microscopy scheme for dipolar dysprosium atoms, which provides a reliable route towards the experimental study of topological quantum critical points
Is there really a debris disc around ?
The presence of a debris disc around the Gyr-old solar-type star
was suggested by the infrared
excess detection. Follow-up observations with /PACS revealed
a double-lobed feature, that displayed asymmetries both in brightness and
position. Therefore, the disc was thought to be edge-on and significantly
eccentric. Here we present ALMA/ACA observations in Band 6 and 7 which
unambiguously reveal that these lobes show no common proper motion with
. In these observations, no flux has been detected
around that exceeds the levels. We
conclude that surface brightness upper limits of a debris disc around
are at 1.3 mm, and
at 870 microns. Our results overall demonstrate
the capability of the ALMA/ACA to follow-up observations of
debris discs and clarify the effects of background confusion.Comment: 6 pages, 2 figures, 2 table
Hydrologic responses to deforestation in southwestern amazon sub-basins corroborated by hydrologic simulations.
In-vivo 3D Magnetic Resonance Volumetric Analysis of Fetal Cerebellum: From normal to pathology (unilateral cerebellar hypoplasia)
Interacting second-order topological insulators in one-dimensional fermions with correlated hopping
Automated brain extraction in fetal mri by multi-atlas fusion strategy: Study on healthy and pathological subjects
Self-gravitating fragmentation of eccentric accretion disks
We consider the effects of eccentricity on the fragmentation of
gravitationally unstable accretion disks, using numerical hydrodynamics. We
find that eccentricity does not affect the overall stability of the disk
against fragmentation, but significantly alters the manner in which such
fragments accrete gas. Variable tidal forces around an eccentric orbit slow the
accretion process, and suppress the formation of weakly-bound clumps. The
"stellar" mass function resulting from the fragmentation of an eccentric disk
is found to have a significantly higher characteristic mass than that from a
corresponding circular disk. We discuss our results in terms of the disk(s) of
massive stars at ~0.1pc from the Galactic Center, and find that the
fragmentation of an eccentric accretion disk, due to gravitational instability,
is a viable mechanism for the formation of these systems.Comment: 9 pages, 7 figures. Accepted for publication in Ap
Assessment of fetal corpus callosum biometry by 3D super-resolution reconstructed T2-weighted magnetic resonance imaging.
To assess the accuracy of corpus callosum (CC) biometry, including sub-segments, using 3D super-resolution fetal brain MRI (SR) compared to 2D or 3D ultrasound (US) and clinical low-resolution T2-weighted MRI (T2WS).
Fetal brain biometry was conducted by two observers on 57 subjects [21-35 weeks of gestational age (GA)], including 11 cases of partial CC agenesis. Measures were performed by a junior observer (obs1) on US, T2WS and SR and by a senior neuroradiologist (obs2) on T2WS and SR. CC biometric regression with GA was established. Statistical analysis assessed agreement within and between modalities and observers.
This study shows robust SR to US concordance across gestation, surpassing T2WS. In obs1, SR aligns with US, except for genu and CC length (CCL), enhancing splenium visibility. In obs2, SR closely corresponds to US, differing in rostrum and CCL. The anterior CC (rostrum and genu) exhibits higher variability. SR's regression aligns better with literature (US) for CCL, splenium and body than T2WS. SR is the method with the least missing values.
SR yields CC biometry akin to US (excluding anterior CC). Thanks to superior 3D visualization and better through plane spatial resolution, SR allows to perform CC biometry more frequently than T2WS
Evolution of massive stars with new hydrodynamic wind models
Here we present evolutionary models for a set of massive stars, introducing a
new prescription for the mass-loss rate obtained from hydrodynamical
calculations in which the wind velocity profile, , and the
line-acceleration, , are obtained in a self consistently way.
Replacing mass-loss rates at the Main Sequence stage from the standard Vink's
formula by our new recipe, we generate a new set of evolutionary tracks for
and and metallicities
(Galactic), (LMC), and (SMC).
Our new derived formula for mass-loss rate predicts a dependence , where is not longer constant but dependent on the stellar
mass: ranging from when , to when
.
We found that models adopting the new recipe for retain more mass
during their evolution, which is expressed in larger radii and consequently
more luminous tracks over the Hertzsprung-Russell diagram. These differences
are more prominent for the cases of and 120 at
solar metallicity, where we found self-consistent tracks are dex
brighter and keep extra mass up to 20 , compared with the classical
models using the previous formulation for mass-loss rate.
Moreover, we observed remarkable differences for the evolution of the
radionuclide isotope Al in the core and the surface of the star. Since
are weaker than the commonly adopted values for evolutionary
tracks, self-consistent tracks predict a later modification in the abundance
number of Al in the stellar winds. This new behaviour could provide
useful information about the real contribution of this isotope from massive
stars to the Galactic interstellar medium.Comment: Accepted for publication in Astronomy & Astrophysic
- …