9,998 research outputs found
The signature of the scattering between dark sectors in large scale cosmic microwave background anisotropies
We study the interaction between dark sectors by considering the momentum
transfer caused by the dark matter scattering elastically within the dark
energy fluid. Describing the dark scattering analogy to the Thomson scattering
which couples baryons and photons, we examine the impact of the dark scattering
in CMB observations. Performing global fitting with the latest observational
data, we find that for a dark energy equation of state , the CMB gives
tight constraints on dark matter-dark energy elastic scattering. Assuming a
dark matter particle of proton mass, we derive an elastic scattering cross
section of where is the
cross section of Thomson scattering. For , however, the constraints are
poor. For , can formally take any value.Comment: 9 pages, 6 figures, accepted for publication in PR
Revisit of cosmic age problem
We investigate the cosmic age problem associated with 9 extremely old
globular clusters in M31 galaxy and 1 very old high- quasar APM 08279 + 5255
at . These 9 globular clusters have not been used to study the cosmic
age problem in the previous literature. By evaluating the age of the universe
in the CDM model with the observational constraints from the SNIa, the
BAO, the CMB, and the independent measurements, we find that the
existence of 5 globular clusters and 1 high- quasar are in tension (over
2 confidence level) with the current cosmological observations. So if
the age estimates of these objects are correct, the cosmic age puzzle still
remains in the standard cosmology. Moreover, we extend our investigations to
the cases of the interacting dark energy models. It is found that although the
introduction of the interaction between dark sectors can give a larger cosmic
age, the interacting dark energy models still have difficulty to pass the
cosmic age test.Comment: 11 pages, 5 figures, 1 table, accepted for publication in PR
Exploring the Latest Union2 SNIa Dataset by Using Model-Independent Parametrization Methods
We explore the cosmological consequences of the recently released Union2
sample of 557 Type Ia supernovae (SNIa). Combining this latest SNIa dataset
with the Cosmic microwave background (CMB) anisotropy data from the Wilkinson
Microwave Anisotropy Probe 7 year (WMAP7) observations and the baryon acoustic
oscillation (BAO) results from the Sloan Digital Sky Survey (SDSS) Data Release
7 (DR7), we measure the dark energy density function as a free function of redshift. Two
model-independent parametrization methods (the binned parametrization and the
polynomial interpolation parametrization) are used in this paper. By using the
statistic and the Bayesian information criterion, we find that the
current observational data are still too limited to distinguish which
parametrization method is better, and a simple model has advantage in fitting
observational data than a complicated model. Moreover, it is found that all
these parametrizations demonstrate that the Union2 dataset is still consistent
with a cosmological constant at 1 confidence level. Therefore, the
Union2 dataset is different from the Constitution SNIa dataset, which more
favors a dynamical dark energy.Comment: 11 pages, 8 figures, 2 tables, accepted for publication in PR
Dependence of the decoherence of polarization states in phase-damping channels on the frequency spectrum envelope of photons
We consider the decoherence of photons suffering in phase-damping channels.
By exploring the evolutions of single-photon polarization states and two-photon
polarization-entangled states, we find that different frequency spectrum
envelopes of photons induce different decoherence processes. A white frequency
spectrum can lead the decoherence to an ideal Markovian process. Some color
frequency spectrums can induce asymptotical decoherence, while, some other
color frequency spectrums can make coherence vanish periodically with variable
revival amplitudes. These behaviors result from the non-Markovian effects on
the decoherence process, which may give rise to a revival of coherence after
complete decoherence.Comment: 7 pages, 4 figures, new results added, replaced by accepted versio
Extraction of Plumes in Turbulent Thermal Convection
We present a scheme to extract information about plumes, a prominent coherent
structure in turbulent thermal convection, from simultaneous local velocity and
temperature measurements. Using this scheme, we study the temperature
dependence of the plume velocity and understand the results using the equations
of motion. We further obtain the average local heat flux in the vertical
direction at the cell center. Our result shows that heat is not mainly
transported through the central region but instead through the regions near the
sidewalls of the convection cell.Comment: 4 pages, 4 figures, submitted to Physical Review Letter
New archidermapteran earwigs (Dermaptera) from the Middle Jurassic of Inner Mongolia, China
Two new species of Archidermaptera are described and figured from the Middle Jurassic Jiulonghsan Formation of Daohugou, Inner Mongolia, China. Aneuroderma oiodes gen. & sp. nov. is described in the family Protodiplatyidae and Sinopalaeodermata concavum sp. nov. is established in the family Dermapteridae. Both new species share the typical characters of the extinct suborder Archidermaptera (e.g., pentamerous metatarsi, filiform and multimerous cerci, externalized ovipositor). Aneuroderma gen. nov. is compared with other genera of the Protodiplatyidae, while S. concavum sp. nov. allows us to emend the diagnosis of the genus Sinopalaeodermata. We briefly discuss the diversity of Archidermaptera and challenges to understanding relationships among this mid-Mesozoic diversity
The Online Data Quality Monitoring System at BESIII
The online Data Quality Monitoring (DQM) plays an important role in the data
taking process of HEP experiments. BESIII DQM samples data from online data
flow, reconstructs them with offline reconstruction software, and automatically
analyzes the reconstructed data with user-defined algorithms. The DQM software
is a scalable distributed system. The monitored results are gathered and
displayed in various formats, which provides the shifter with current run
information that can be used to find problems early. This paper gives an
overview of DQM system at BESIII.Comment: Already submit to Chinese Physics
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