525 research outputs found
On the anomalous afterglow seen in a chameleon afterglow search
We present data from our investigation of the anomalous orange-colored
afterglow that was seen in the GammeV Chameleon Afterglow Search (CHASE). These
data includes information about the broad band color of the observed glow, the
relationship between the glow and the temperature of the apparatus, and other
data taken prior to and during the science operations of CHASE. While differing
in several details, the generic properties of the afterglow from CHASE are
similar to luminescence seen in some vacuum compounds. Contamination from this,
or similar, luminescent signatures will likely impact the design of
implementation of future experiments involving single photon detectors and high
intensity light sources in a cryogenic environment.Comment: 6 pages, 5 figures, submitted to PR
Residual Energies after Slow Quantum Annealing
Features of the residual energy after the quantum annealing are investigated.
The quantum annealing method exploits quantum fluctuations to search the ground
state of classical disordered Hamiltonian. If the quantum fluctuation is
reduced sufficiently slowly and linearly by the time, the residual energy after
the quantum annealing falls as the inverse square of the annealing time. We
show this feature of the residual energy by numerical calculations for
small-sized systems and derive it on the basis of the quantum adiabatic
theorem.Comment: 4 pages, 2 figure
Inhomogeneous quantum diffusion and decay of a meta-stable state
We consider the quantum stochastic dynamics of a system whose interaction
with the reservoir is considered to be linear in bath co-ordinates but
nonlinear in system co-ordinates. The role of the space-dependent friction and
diffusion has been examined in the decay rate of a particle from a meta-stable
well. We show how the decay rate can be hindered by inhomogeneous dissipation
due nonlinear system-bath coupling strength.Comment: To be published in Phys. Lett.
The Hong-Ou-Mandel effect with atoms
Controlling light at the level of individual photons has led to advances in
fields ranging from quantum information and precision sensing to fundamental
tests of quantum mechanics. A central development that followed the advent of
single photon sources was the observation of the Hong-Ou- Mandel (HOM) effect,
a novel two-photon path interference phenomenon experienced by
indistinguishable photons. The effect is now a central technique in the field
of quantum optics, harnessed for a variety of applications such as diagnosing
single photon sources and creating probabilistic entanglement in linear quantum
computing. Recently, several distinct experiments using atomic sources have
realized the requisite control to observe and exploit Hong-Ou-Mandel
interference of atoms. This article provides a summary of this phenomenon and
discusses some of its implications for atomic systems. Transitioning from the
domain of photons to atoms opens new perspectives on fundamental concepts, such
as the classification of entanglement of identical particles. It aids in the
design of novel probes of quantities such as entanglement entropy by combining
well established tools of AMO physics - unity single-atom detection, tunable
interactions, and scalability - with the Hong-Ou-Mandel interference.
Furthermore, it is now possible for established protocols in the photon
community, such as measurement-induced entanglement, to be employed in atomic
experiments that possess deterministic single-particle production and
detection. Hence, the realization of the HOM effect with atoms represents a
productive union of central ideas in quantum control of atoms and photons.Comment: 19 pages, 7 figure
Digital Data Preservation and Curation: A Collaboration Among Libraries, Publishers, and the Virtual Observatory
Digital Data Preservation and Curation: A Collaboration Among Libraries, Publishers, and the Virtual Observatory. Astronomers are producing and analyzing data at ever more prodigious rates. NASA's Great Observatories, ground-based national observatories, and major survey projects have archive and data distribution systems in place to manage their standard data products, and these are now interlinked through the protocols and metadata standards agreed upon in the Virtual Observatory. However, the digital data associated with peer-reviewed publications is only rarely archived. Most often, astronomers publish graphical representations of their data but not the data themselves. Other astronomers cannot readily inspect the data to either confirm the interpretation presented in a paper or extend the analysis. Highly processed data sets reside on departmental servers and the personal computers of astronomers, and may or may not be available a few years hence. We are investigating ways to preserve and curate the digital data associated with peer-reviewed journals in astronomy. The technology and standards of the VO provide one component of the necessary technology. A variety of underlying systems can be used to physically host a data repository, and indeed this repository need not be centralized. The repository, however, must be managed and data must be documented through high quality, curated metadata. Multiple access portals must be available: the original journal, the host data center, the Virtual Observatory, or any number of topically-oriented data services utilizing VO-standard access mechanisms
A Chandra Observation of the Obscured Star-Forming Complex W40
The young stellar cluster illuminating the W40 H II region, one of the
nearest massive star forming regions, has been observed with the ACIS detector
on board the Chandra X-ray Observatory. Due to its high obscuration, this is a
poorly-studied stellar cluster with only a handful of bright stars visible in
the optical band, including three OB stars identified as primary excitation
sources. We detect 225 X-ray sources, of which 85% are confidently identified
as young stellar members of the region. Two potential distances of the cluster,
260 pc and 600 pc, are used in the paper. Supposing the X-ray luminosity
function to be universal, it supports a 600 pc distance as a lower limit for
W40 and a total population of at least 600 stars down to 0.1 Mo under the
assumption of a coeval population with a uniform obscuration. In fact, there is
strong spatial variation in Ks-band-excess disk fraction and non-uniform
obscuration due to a dust lane that is identified in absorption in optical,
infrared and X-ray. The dust lane is likely part of a ring of material which
includes the molecular core within W40. In contrast to the likely ongoing star
formation in the dust lane, the molecular core is inactive. The star cluster
has a spherical morphology, an isothermal sphere density profile, and mass
segregation down to 1.5 Mo. However, other cluster properties, including a
\leq{1} Myr age estimate and ongoing star formation, indicate that the cluster
is not dynamically relaxed. X-ray diffuse emission and a powerful flare from a
young stellar object are also reported.Comment: Accepted for publication in The Astrophysical Journal. 60 pages, 16
figure
Glacial isostatic adjustment in Fennoscandia from GRACE data and comparison with geodynamical models
Architecture of soil microaggregates: Advanced methodologies to explore properties and functions
The functions of soils are intimately linked to their three-dimensional pore space and the associated biogeochemical interfaces, mirrored in the complex structure that developed during pedogenesis. Under stress overload, soil disintegrates into smaller compound structures, conventionally named aggregates. Microaggregates (<250 µm) are recognized as the most stable soil structural units. They are built of mineral, organic, and biotic materials, provide habitats for a vast diversity of microorganisms, and are closely involved in the cycling of matter and energy. However, exploring the architecture of soil microaggregates and their linkage to soil functions remains a challenging but demanding scientific endeavor. With the advent of complementary spectromicroscopic and tomographic techniques, we can now assess and visualize the size, composition, and porosity of microaggregates and the spatial arrangement of their interior building units. Their combinations with advanced experimental pedology, multi-isotope labeling experiments, and computational approaches pave the way to investigate microaggregate turnover and stability, explore their role in element cycling, and unravel the intricate linkage between structure and function. However, spectromicroscopic techniques operate at different scales and resolutions, and have specific requirements for sample preparation and microaggregate isolation; hence, special attention must be paid to both the separation of microaggregates in a reproducible manner and the synopsis of the geography of information that originates from the diverse complementary instrumental techniques. The latter calls for further development of strategies for synlocation and synscaling beyond the present state of correlative analysis. Here, we present examples of recent scientific progress and review both options and challenges of the joint application of cutting-edge techniques to achieve a sophisticated picture of the properties and functions of soil microaggregates
Close Companions to Young Stars. I. A Large Spectroscopic Survey in Chamaeleon I and Taurus-Auriga
We present the results of a multiplicity survey of 212 T Tauri stars in the
Chamaeleon I and Taurus-Auriga star-forming regions, based on high-resolution
spectra from the Magellan Clay 6.5 m telescope. From these data, we achieved a
typical radial velocity precision of ~80 m/s with slower rotators yielding
better precision, in general. For 174 of these stars, we obtained multi-epoch
data with sufficient time baselines to identify binaries based on radial
velocity variations. We identified eight close binaries and four close triples,
of which three and two, respectively, are new discoveries. The spectroscopic
multiplicity fractions we find for Cha I (7%) and Tau-Aur (6%) are similar to
each other, and to the results of field star surveys in the same mass and
period regime. However, unlike the results from imaging surveys, the frequency
of systems with close companions in our sample is not seen to depend on primary
mass. Additionally, we do not find a strong correlation between accretion and
close multiplicity. This implies that close companions are not likely the main
source of the accretion shut down observed in weak-lined T Tauri stars. Our
results also suggest that sufficient radial velocity precision can be achieved
for at least a subset of slowly rotating young stars to search for hot Jupiter
planets.Comment: Accepted for publication in ApJ. 55 pages, 37 figures, 7 tables.
Formatted with emulateapj. Full version with 221 figures will be available on
ApJ or upon request. Revised Tables 4, 5 & 6 and individual source figures to
correct MJ
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