4,745 research outputs found
Fast Characterization of Dispersion and Dispersion Slope of Optical Fiber Links using Spectral Interferometry with Frequency Combs
We demonstrate fast characterization (~1.4 microseconds) of both the
dispersion and dispersion slope of long optical fiber links (~25 km) using dual
quadrature spectral interferometry with an optical frequency comb. Compared to
previous spectral interferometry experiments limited to fiber lengths of
meters, the long coherence length and the periodic delay properties of
frequency combs, coupled with fast data acquisition, enable spectral
interferometric characterization of fibers longer by several orders of
magnitude. We expect that our method will be useful to recently proposed
lightwave techniques like coherent WDM and to coherent modulation formats by
providing a real time monitoring capability for the link dispersion. Another
area of application would be in stabilization of systems which perform
frequency and timing distribution over long fiber links using stabilized
optical frequency combs.Comment: 3 pages, 3 figures, Minor changes to tex
Evolution of cooperation in multilevel public goods games with community structures
In a community-structured population, public goods games (PGG) occur both
within and between communities. Such type of PGG is referred as multilevel
public goods games (MPGG). We propose a minimalist evolutionary model of the
MPGG and analytically study the evolution of cooperation. We demonstrate that
in the case of sufficiently large community size and community number, if the
imitation strength within community is weak, i.e., an individual imitates
another one in the same community almost randomly, cooperation as well as
punishment are more abundant than defection in the long run; if the imitation
strength between communities is strong, i.e., the more successful strategy in
two individuals from distinct communities is always imitated, cooperation and
punishment are also more abundant. However, when both of the two imitation
intensities are strong, defection becomes the most abundant strategy in the
population. Our model provides insight into the investigation of the
large-scale cooperation in public social dilemma among contemporary
communities.Comment: 6 pages, 4 figures, Accepted by EP
Gaussian-shaped Optical Frequency Comb Generation for Microwave Photonic Filtering
Using only electro-optic modulators, we generate a 41-line 10-GHz
Gaussian-shaped optical frequency comb. We use this comb to demonstrate
apodized microwave photonic filters with greater than 43-dB sidelobe
suppression without the need for a pulse shaper.Comment: 3 pages, 4 figure
An Enhanced Archive Facilitating Climate Impacts and Adaptation Analysis
We describe the expansion of a publicly available archive of downscaled climate and hydrology projections for the United States. Those studying or planning to adapt to future climate impacts demand downscaled climate model output for local or regional use. The archive we describe attempts to fulfill this need by providing data in several formats, selectable to meet user needs. Our archive has served as a resource for climate impacts modelers, water managers, educators, and others. Over 1,400 individuals have transferred more than 50 TB of data from the archive. In response to user demands, the archive has expanded from monthly downscaled data to include daily data to facilitate investigations of phenomena sensitive to daily to monthly temperature and precipitation, including extremes in these quantities. New developments include downscaled output from the new Coupled Model Intercomparison Project phase 5 (CMIP5) climate model simulations at both the monthly and daily time scales, as well as simulations of surface hydrologi- cal variables. The web interface allows the extraction of individual projections or ensemble statistics for user-defined regions, promoting the rapid assessment of model consensus and uncertainty for future projections of precipitation, temperature, and hydrology. The archive is accessible online (http://gdo-dcp.ucllnl.org/downscaled_ cmip_projections)
Cosmological Constant, Dark Matter, and Electroweak Phase Transition
Accepting the fine tuned cosmological constant hypothesis, we have recently
proposed that this hypothesis can be tested if the dark matter freeze out
occurs at the electroweak scale and if one were to measure an anomalous shift
in the dark matter relic abundance. In this paper, we numerically compute this
relic abundance shift in the context of explicit singlet extensions of the
Standard Model and explore the properties of the phase transition which would
lead to the observationally most favorable scenario. Through the numerical
exploration, we explicitly identify a parameter space in a singlet extension of
the standard model which gives order unity observable effects. We also clarify
the notion of a temperature dependence in the vacuum energy.Comment: 58 pages, 10 figure
Experimental Line Parameters of the b^(1)Σ^(+)_g ← X^(3)Σ^(-)_g Band of Oxygen Isotopologues at 760 nm Using Frequency-Stabilized Cavity Ring-Down Spectroscopy
Positions, intensities, self-broadened widths, and collisional narrowing coefficients of the oxygen isotopologues ^(16)O^(18)O, ^(16)O^(17)O, ^(17)O^(18)O, and ^(18)O^(18)O have been measured for the b^(1)Σg + ← X^(3)Σg − (0,0) band using frequency-stabilized cavity ring-down spectroscopy. Line positions of 156 P-branch transitions were referenced against the hyperfine components of the ^(39)K D_1 (4s ^(2)S_(1/2) → 4p ^(2)P_(1/2)) and D_2 (4s ^(2)S_(1/2) → 4p ^(2)P_(3/2)) transitions, yielding precisions of ~0.00005 cm^(−1) and absolute accuracies of 0.00030 cm^(−1) or better. New excited b^(1)Σg + state molecular constants are reported for all four isotopologues. The measured line intensities of the ^(16)O^(18)O isotopologue are within 2% of the values currently assumed in molecular databases. However, the line intensities of the ^(16)O^(17)O isotopologue show a systematic, J-dependent offset between our results and the databases. Self-broadening half-widths for the various isotopologues are internally consistent to within 2%. This is the first comprehensive study of the line intensities and shapes for the ^(17)O^(18)O or ^(18)O_2 isotopologues of the b^(1)Σg + ← X^(3)Σg − (0,0) band of O_2. The ^(16)O_2, ^(16)O^(18)O, and ^(16)O^(17)O line parameters for the oxygen A-band have been extensively revised in the HITRAN 2008 database using results from the present study
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