4,619 research outputs found
Relative categories: Another model for the homotopy theory of homotopy theories
We lift Charles Rezk's complete Segal space model structure on the category
of simplicial spaces to a Quillen equivalent one on the category of relative
categories.Comment: 27 pages. Updated to correct typographical error
A characterization of simplicial localization functors
We characterize simplicial localization functors among relative functors from
relative categories to simplicial categories as any choice of homotopy inverse
to the delocalization functor of Dwyer and the second author.Comment: 7 pages. Typographical errors correcte
Kondo Effect in Fermi Systems with a Gap: A Renormalization Group Study
We present the results of a Wilson Renormalization Group study of the
single-impurity Kondo and Anderson models in a system with a gap in the
conduction electron spectrum. The behavior of the impurity susceptibility and
the zero-frequency response function, are discussed in the
cases with and without particle-hole symmetry. In addition, for the asymmetric
Anderson model the correlation functions, , are computed.Comment: 10 pages, 10 figure
Проблема денуклеаризации Корейского полуострова
Кан Д. С. Проблема денуклеаризации Корейского полуострова / Д. С. Кан // Актуальні проблеми політики зб. наук. пр. / редкол.: С. В. Ківалов (голов. ред.), Л. І. Кормич (заст. голов. ред.), М. А. Польовий (відп. секр.) [та ін.] ; НУ «ОЮА», Південноукр. центр гендер. проблем. – Одеса : Фенікс, 2015. – Вип. 55. – С. 11-23.В данной статье идет речь о проблеме денуклеаризации Корейского
полуострова, которая является ключевым фактором в обострении отношений между странами Северо-Восточной Азии. Проанализированы первый и второй ядерные кризисы и Женевское соглашение 1994 года. Статья дает возможность более глубоко понять суть ядерной проблемы в Северной Кореи и оценить степень важности ракетно-ядерной угрозы со стороны КНДР
In Situ Thermal Decomposition of Exfoliated Two-Dimensional Black Phosphorus
With a semiconducting band gap and high charge carrier mobility,
two-dimensional (2D) black phosphorus (BP), often referred to as phosphorene,
holds significant promise for next generation electronics and optoelectronics.
However, as a 2D material, it possesses a higher surface area to volume ratio
than bulk BP, suggesting that its chemical and thermal stability will be
modified. Herein, an atomic-scale microscopic and spectroscopic study is
performed to characterize the thermal degradation of mechanically exfoliated 2D
BP. From in situ scanning/transmission electron microscopy, decomposition of 2D
BP is observed to occur at ~400 {\deg}C in vacuum, in contrast to the 550
{\deg}C bulk BP sublimation temperature. This decomposition initiates via
eye-shaped cracks along the [001] direction and then continues until only a
thin, amorphous red phosphorous like skeleton remains. In situ electron energy
loss spectroscopy, energy-dispersive X-ray spectroscopy, and energy-loss
near-edge structure changes provide quantitative insight into this chemical
transformation process.Comment: In press: 4 figures in main manuscript, 27 pages with supporting
informatio
Spatiotemporal Mapping of Photocurrent in a Monolayer Semiconductor Using a Diamond Quantum Sensor
The detection of photocurrents is central to understanding and harnessing the
interaction of light with matter. Although widely used, transport-based
detection averages over spatial distributions and can suffer from low
photocarrier collection efficiency. Here, we introduce a contact-free method to
spatially resolve local photocurrent densities using a proximal quantum
magnetometer. We interface monolayer MoS2 with a near-surface ensemble of
nitrogen-vacancy centers in diamond and map the generated photothermal current
distribution through its magnetic field profile. By synchronizing the
photoexcitation with dynamical decoupling of the sensor spin, we extend the
sensor's quantum coherence and achieve sensitivities to alternating current
densities as small as 20 nA per micron. Our spatiotemporal measurements reveal
that the photocurrent circulates as vortices, manifesting the Nernst effect,
and rises with a timescale indicative of the system's thermal properties. Our
method establishes an unprecedented probe for optoelectronic phenomena, ideally
suited to the emerging class of two-dimensional materials, and stimulates
applications towards large-area photodetectors and stick-on sources of magnetic
fields for quantum control.Comment: 19 pages, 4 figure
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