93 research outputs found
The stabilization of the Frobenius--Hecke traces on the intersection cohomology of orthogonal Shimura varieties
The orthogonal Shimura varieties are associated to special orthogonal groups
over of signature at infinity. We consider the intersection
cohomology of their Baily--Borel compactifications, and prove a version of
Morel's formula for the Frobenius--Hecke traces on it for almost all primes.
Our main result is the stabilization of this formula. As an application, we
compute the Hasse--Weil zeta function of the intersection cohomology in some
special cases, using the recent work of Arthur and Ta\"ibi on the endoscopic
classification of automorphic representations of special orthogonal groups
6G Non-Terrestrial Networks Enabled Low-Altitude Economy: Opportunities and Challenges
The unprecedented development of non-terrestrial networks (NTN) utilizes the
low-altitude airspace for commercial and social flying activities. The
integration of NTN and terres- trial networks leads to the emergence of
low-altitude economy (LAE). A series of LAE application scenarios are enabled
by the sensing, communication, and transportation functionalities of the
aircrafts. The prerequisite technologies supporting LAE are introduced in this
paper, including the network coverage and aircrafts detection. The LAE
functionalities assisted by aircrafts with respect to sensing and communication
are then summarized, including the terrestrial and non-terrestrial targets
sensing, ubiquitous coverage, relaying, and traffic offloading. Finally,
several future directions are identified, including aircrafts collaboration,
energy efficiency, and artificial intelligence enabled LAE.Comment: This paper has been submitted to IEEE for possible publicatio
Integer and fractional Chern insulators in twisted bilayer MoTe2
Chern insulators, which are the lattice analogs of the quantum Hall states,
can potentially manifest high-temperature topological orders at zero magnetic
field to enable next-generation topological quantum devices. To date, integer
Chern insulators have been experimentally demonstrated in several systems at
zero magnetic field, but fractional Chern insulators have been reported only in
graphene-based systems under a finite magnetic field. The emergence of
semiconductor moir\'e materials, which support tunable topological flat bands,
opens a new opportunity to realize fractional Chern insulators. Here, we report
the observation of both integer and fractional Chern insulators at zero
magnetic field in small-angle twisted bilayer MoTe2 by combining the local
electronic compressibility and magneto-optical measurements. At hole filling
factor {\nu}=1 and 2/3, the system is incompressible and spontaneously breaks
time reversal symmetry. We determine the Chern number to be 1 and 2/3 for the
{\nu}=1 and {\nu}=2/3 gaps, respectively, from their dispersion in filling
factor with applied magnetic field using the Streda formula. We further
demonstrate electric-field-tuned topological phase transitions involving the
Chern insulators. Our findings pave the way for demonstration of quantized
fractional Hall conductance and anyonic excitation and braiding in
semiconductor moir\'e materials
Enhancing Spatio-Temporal Fusion of MODIS and Landsat Data by Incorporating 250 m MODIS Data
Spatio-temporal fusion of MODIS and Landsat data aims to produce new data that have simultaneously the Landsat spatial resolution and MODIS temporal resolution. It is an ill-posed problem involving large uncertainty, especially for reproduction of abrupt changes and heterogeneous landscapes. In this paper, we proposed to incorporate the freely available 250 m MODIS images into spatio-temporal fusion to increase prediction accuracy. The 250 m MODIS bands 1 and 2 are fused with 500 m MODIS bands 3-7 using the advanced area-to-point regression kriging approach. Based on a standard spatio-temporal fusion approach, the interim 250 m fused MODIS data are then downscaled to 30 m with the aid of the available 30 m Landsat data on temporally close days. The 250 m data can provide more information for the abrupt changes and heterogeneous landscapes than the original 500 m MODIS data, thus increasing the accuracy of spatio-temporal fusion predictions. The effectiveness of the proposed scheme was demonstrated using two datasets
Anomalous stopping of laser-accelerated intense proton beam in dense ionized matter
Ultrahigh-intensity lasers (10-10W/cm) have opened up new
perspectives in many fields of research and application [1-5]. By irradiating a
thin foil, an ultrahigh accelerating field (10 V/m) can be formed and
multi-MeV ions with unprecedentedly high intensity (10A/cm) in short
time scale (ps) are produced [6-14]. Such beams provide new options in
radiography [15], high-yield neutron sources [16], high-energy-density-matter
generation [17], and ion fast ignition [18,19]. An accurate understanding of
the nonlinear behavior of beam transport in matter is crucial for all these
applications. We report here the first experimental evidence of anomalous
stopping of a laser-generated high-current proton beam in well-characterized
dense ionized matter. The observed stopping power is one order of magnitude
higher than single-particle slowing-down theory predictions. We attribute this
phenomenon to collective effects where the intense beam drives an decelerating
electric field approaching 1GV/m in the dense ionized matter. This finding will
have considerable impact on the future path to inertial fusion energy.Comment: 8 pages, 4 figure
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