29,538 research outputs found
Simulating dynamical quantum Hall effect with superconducting qubits
We propose an experimental scheme to simulate the dynamical quantum Hall
effect and the related interaction-induced topological transition with a
superconducting-qubit array. We show that a one-dimensional Heisenberg model
with tunable parameters can be realized in an array of superconducting qubits.
The quantized plateaus, which is a feature of the dynamical quantum Hall
effect, will emerge in the Berry curvature of the superconducting qubits as a
function of the coupling strength between nearest neighbor qubits. We
numerically calculate the Berry curvatures of two-, four- and six-qubit arrays,
and find that the interaction-induced topological transition can be easily
observed with the simplest two-qubit array. Furthermore, we analyze some
practical conditions in typical experiments for observing such dynamical
quantum Hall effect.Comment: 9 pages, 6 figures, version accepted by PR
The prediction of using LHAASO's cosmic-ray electron measurements to constrain decaying heavy dark matter
LHAASO is an instrument designed for detecting cosmic rays (CRs) and gamma
rays at TeV to PeV energies. The decays of heavy dark matter particles in the
Galactic halo may produce high-energy electrons that can be detected by LHAASO.
The main background for the LHAASO's CR electron measurements is the hadron
residuals due to mis-identification of the particle species. In this paper, we
estimate the LHAASO's electron background using the known all-particle CR
spectrum and the hadron rejection efficiency of LHAASO. With the estimated
background, we predict the capability of LHAASO to constrain DM decay lifetime
at 95% confidence level for various channels. We find that, if neglecting
systematic uncertainties, the CR electron measurement by LHAASO can improve the
current best results by up to on order of magnitude for DM masses between 100 -
1000TeV. However, indirect measurements of CR electrons by ground-based
experiments suffer from uncertainties included in the calculation, the
projected constraints will be largely weakened. So for using the CR electron
observation of LHAASO to constrain the DM parameters, the key point is whether
the systematic error can be effectively reduced.Comment: 11 pages, 8 figures, accepted for publication in PR
Strong enhancement of chlorophyll a concentration by a weak typhoon
Recent studies demonstrate that chlorophyll a (chl a) concentrations in the
surface ocean can be significantly enhanced due to typhoons. The present study
investigated chl a concentrations in the middle of the South China Sea (SCS)
from 1997-2007. Only the Category1 (minimal) Typhoon Hagibis (2007) had a
notable effect on the chl a concentrations. Typhoon Hagibis had a strong
upwelling potential due to its location near the equator, and the forcing time
of the typhoon (>82 h) was much longer than the geostrophic adjustment time
(~63 h). The higher upwelling velocity and the longer forcing time increased
the depth of the mixed-layer, which consequently induced a strong phytoplankton
bloom that accounted for about 30% of the total annual chl a concentration in
the middle of the SCS. The implication is that the forcing time of a typhoon
should be long enough to establish a strong upwelling and consequently for the
induction of significant upper ocean responses.Comment: Typhoon-Ocean Environment interaction
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