10,446 research outputs found
Topological Bulk Lasing Modes Using an Imaginary Gauge Field
Topological edge modes, which are robust against disorders, have been used to
enhance the spatial stability of lasers. Recently, it was revealed that
topological lasers can be further stabilized using a novel topological phase in
non-Hermitian photonic topological insulators. Here we propose a procedure to
realize topologically protected modes extended over a d-dimensional bulk by
introducing an imaginary gauge field. This generalizes the idea of zero-energy
extended modes in the one-dimensional Su-Schrieffer-Heeger lattice into higher
dimensional lattices allowing a d-dimensional bulky mode that is topologically
protected. Furthermore, we numerically demonstrate that the topological bulk
lasing mode can achieve high temporal stability superior to topological edge
mode lasers. In the exemplified topological extended mode in the kagome
lattice, we show that large regions of stability exist in its parameter space.Comment: 10 pages, 10 figure
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A Study of Density of States and Ground States in Hydrophobic-Hydrophilic Protein Folding Models by Equi-energy Sampling
We propose an equi-energy (EE) sampling approach to study protein folding in the two-dimensional hydrophobic-hydrophilic (HP) lattice model. This approach enables efficient exploration of the global energy landscape and provides accurate estimates of the density of states, which then allows us to conduct a detailed study of the thermodynamics of HP protein folding, in particular, on the temperature dependence of the transition from folding to unfolding and on how sequence composition affects this phenomenon. With no extra cost, this approach also provides estimates on global energy minima and ground states. Without using any prior structural information of the protein the EE sampler is able to find the ground states that match the best known results in most benchmark cases. The numerical results demonstrate it as a powerful method to study lattice protein folding models.Statistic
Teaching physical education abroad : Perspectives from host cooperating teachers, local students and Australian pre-service teachers using the social exchange theory
Research on pre-service teachers (PSTs) in international teaching practicums often focus on their experiences rather than how it ameliorates the host communities. Constructs of Social Exchange Theory were used to explore benefits and challenges experienced by four Australian PSTs, two Chinese cooperating teachers (CTs) and 169 local students. The PSTs experienced personal and professional growth, the CTs gained new pedagogical insights, and local students experienced cultural immersion with improved engagement in physical education. Despite mutual benefits, challenges emerged from teaching differences, language barrier, and personal obstacles. These underscore the necessity of investing time and resources to minimise such challenges
An HI study of the collisional ring galaxy NGC 922
We present new atomic hydrogen (HI) observations of the collisional ring
galaxy NGC 922 obtained using the Australia Telescope Compact Array. Our
observations reveal for the first time the vast extent of the HI disc of this
galaxy. The HI morphology and kinematics of NGC 922 show that this galaxy is
not the product of a simple drop-through interaction, but has a more complex
interaction history. The integrated HI flux density of NGC 922 from our
observations is 24.7 Jy km s, which is within the error of the flux
value obtained using the -m Parkes radio telescope. This flux density
translates to a total HI mass of M and corresponds to
an HI to total mass fraction (M/M) of approximately . The
gaseous structures of NGC 922 are more extended to the north and include an HI
tail that has a projected physical length of kpc. Gas warps are also
evident in the velocity field of NGC 922 and are more prominent on the
approaching and the western side of the disc. In comparison with a large sample
of star-forming galaxies in the local Universe, NGC 922 possesses a high gas
fraction relative to galaxies with a similar stellar mass of ~
M, and exhibits a high specific star formation rate.Comment: 11 pages, 8 figures, published in MNRA
Spontaneous Subtle Expression Detection and Recognition based on Facial Strain
Optical strain is an extension of optical flow that is capable of quantifying
subtle changes on faces and representing the minute facial motion intensities
at the pixel level. This is computationally essential for the relatively new
field of spontaneous micro-expression, where subtle expressions can be
technically challenging to pinpoint. In this paper, we present a novel method
for detecting and recognizing micro-expressions by utilizing facial optical
strain magnitudes to construct optical strain features and optical strain
weighted features. The two sets of features are then concatenated to form the
resultant feature histogram. Experiments were performed on the CASME II and
SMIC databases. We demonstrate on both databases, the usefulness of optical
strain information and more importantly, that our best approaches are able to
outperform the original baseline results for both detection and recognition
tasks. A comparison of the proposed method with other existing spatio-temporal
feature extraction approaches is also presented.Comment: 21 pages (including references), single column format, accepted to
Signal Processing: Image Communication journa
D mesons in matter and the in-medium properties of charmonium
We study the changes in the partial decay widths of excited charmonium states
into , when the D meson mass decreases in nuclear matter, taking the
internal structure of the hadrons into account. Calculations within the 3P0
model for and imply that naive estimates of the
in-medium widths based only on phase space are grossly exaggerated. Due to
nodes in the wave functions, these states may even become narrow at high
densities, if the D meson mass is decreased by about 200 MeV. For the
states, we generally expect stronger modifications of the widths. The relevance
of the widths for suppression in heavy ion collision is
discussed. These phenomena could be explored in experiments at the future
accelerator facility at GSI.Comment: 12 pages, 3 figures; allowed for two independent oscillator
parameters for the charmonium states and D mesons, results are not
significantly modified and conclusions remains unaltere
Heavy-quarkonium interaction in QCD at finite temperature
We explore the temperature dependence of the heavy-quarkonium interaction
based on the Bhanot-Peskin leading order perturbative QCD analysis. The Wilson
coefficients are computed solving the Schrodinger equation in a screened
Coulomb heavy-quark potential. The inverse Mellin transform of the Wilson
coefficients then allows for the computation of the 1S and 2S heavy-quarkonium
gluon and pion total cross section at finite screening/temperature. As a
phenomenological illustration, the temperature dependence of the 1S charmonium
thermal width is determined and compared to recent lattice QCD results.Comment: 14 pages, 5 figures. Clarification added, published versio
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