921 research outputs found
Discriminating different scenarios to account for the cosmic excess by synchrotron and inverse Compton radiation
The excesses of the cosmic positron fraction recently measured by PAMELA and
the electron spectra by ATIC, PPB-BETS, Fermi and H.E.S.S. indicate the
existence of primary electron and positron sources. The possible explanations
include dark matter annihilation, decay, and astrophysical origin, like
pulsars. In this work we show that these three scenarios can all explain the
experimental results of the cosmic excess. However, it may be difficult
to discriminate these different scenarios by the local measurements of
electrons and positrons. We propose possible discriminations among these
scenarios through the synchrotron and inverse Compton radiation of the primary
electrons/positrons from the region close to the Galactic center. Taking
typical configurations, we find the three scenarios predict quite different
spectra and skymaps of the synchrotron and inverse Compton radiation, though
there are relatively large uncertainties. The most prominent differences come
from the energy band MHz for synchrotron emission and GeV for inverse Compton emission. It might be able to discriminate at least
the annihilating dark matter scenario from the other two given the high
precision synchrotron and diffuse -ray skymaps in the future.Comment: published in Pr
Weak cosmic censorship conjecture for the novel charged Einstein-Gauss-Bonnet black hole with test scalar field and particle
Recent researches of the novel Einstein-Gauss-Bonnet (EGB) gravity have
attracted great attention. In this paper, we investigate the validity of the
weak cosmic censorship conjecture for a novel charged EGB black hole with
test charged scalar field and test charged particle respectively. For the test
charged field scattering process, we find that both extremal and near-extremal
black holes cannot be overcharged. For the test charged particle injection, to
first order, an extremal black hole cannot be overcharged while a near-extremal
charged EGB black hole can be destroyed. To second order, however, both
extremal and near-extremal charged EGB black holes can be overcharged for
positive Gauss-Bonnet coupling constant; for negative Gauss-Bonnet coupling
constant, an extremal black hole cannot be overcharged and the validity of the
weak cosmic censorship conjecture for a near-extremal black hole depends on the
Gauss-Bonnet coupling constant.Comment: 13 pages,1 figure;V2: discussions and references added; V3: published
versio
High-frequency monitoring reveals how hydrochemistry and dissolved carbon respond to rainstorms at a karstic critical zone, Southwestern China
Hydrochemical behavior and dissolved carbon dynamics are highly-sensitive to hydrological variations in the monsoon-influenced karstic critical zone which has high chemical weathering rates and experiences strong anthropogenic impact. Continuous high-frequency monitoring in the spring outlet of a karstic catchment in Southwestern China revealed that most hydrochemical variables changed distinctively in response to hydrologic variations, influenced by mixing of different sources and miscellaneous biogeochemical processes. Na+, K+ and SO42− varied significantly with hydrology, showing weak chemostatic behavior controlled by dilution. The flushing effect and random behavior of NO3− and Cl− likely reflect agricultural inputs from high throughflow. Soil CO2 in infiltrated water supports carbonate weathering, enabling DIC (dissolved inorganic carbon) and weathering products (e.g., Ca2+ and Mg2+) to maintain chemostatic behavior. Biogenic DIC exhibited a stronger chemostatic response than carbonate sources and was the foremost control in DIC behavior. Carbon exchange between DIC and DOC (dissolved organic carbon) did not significantly influence DIC concentration and δ13C due to very low DOC concentration. More DOC was exported by flushing from increasing discharge. Hysteretic analysis indicated that the transport processes were controlled by proximal sources mixing and diverse mobilization in various periods responding to rainstorms. NO3− and Cl− presented different hysteresis behavior as sourced from agricultural activities. DOC increased on the hydrograph rising limb and was controlled by a transport-limited regime. However, the hysteresis behavior of most weathering products and DIC were regulated by a process-limited regime in the karstic critical zone. Overall, biogeochemical processes, hydrogeological properties, storm intensity/magnitude and the timing of storms (antecedent conditions) are main factors influencing the response of hydrochemical variables and dissolved carbon to storm events
Observation of quantum fingerprinting beating the classical limit
Quantum communication has historically been at the forefront of advancements,
from fundamental tests of quantum physics to utilizing the quantum-mechanical
properties of physical systems for practical applications. In the field of
communication complexity, quantum communication allows the advantage of an
exponential reduction in the information transmitted over classical
communication to accomplish distributed computational tasks. However, to date,
demonstrating this advantage in a practical setting continues to be a central
challenge. Here, we report an experimental demonstration of a quantum
fingerprinting protocol that for the first time surpasses the ultimate
classical limit to transmitted information. Ultra-low noise superconducting
single-photon detectors and a stable fibre-based Sagnac interferometer are used
to implement a quantum fingerprinting system that is capable of transmitting
less information than the classical proven lower bound over 20 km standard
telecom fibre for input sizes of up to two Gbits. The results pave the way for
experimentally exploring the advanced features of quantum communication and
open a new window of opportunity for research in communication complexity and
testing the foundations of physics.Comment: 19 pages, 4 figure
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