37,336 research outputs found
The Measure for the Multiverse and the Probability for Inflation
We investigate the measure problem in the framework of inflationary
cosmology. The measure of the history space is constructed and applied to
inflation models. Using this measure, it is shown that the probability for the
generalized single field slow roll inflation to last for e-folds is
suppressed by a factor , and the probability for the generalized
-field slow roll inflation is suppressed by a much larger factor
. Some non-inflationary models such as the cyclic model do not
suffer from this difficulty.Comment: 16 page
Wavelet analysis of the transient QPOs in MAXI J1535571 with Insight-HXMT
Using wavelet analysis and power density spectrum, we investigate two
transient quasi-periodic oscillations (QPOs) observed in MAXI J1535571
observed with Insight-HXMT. The transient QPOs have a centroid frequency of
Hz with a FWHM Hz and an rms amplitude . Energy
spectra of QPO and non-QPO regimes are also separated and analyzed, and the
spectra become softer with higher in the non-QPO regime compared to
the QPO regime. Our results suggest that the transient QPOs detected in MJD
58016 and 58017 are still the type-C QPO, and the source remains in its HIMS.
The duration of all type-C QPO signals based on wavelet is positively
correlated with the mean count rate above keV, implying appearance of
QPOs in different time scales should be coupled with the corona. The transient
QPO properties could be related to the jet or flares, perhaps the partial
ejection of the corona is responsible for the disappearance of the type-C QPO.Comment: 10 pages, MNRAS in pres
The Holographic Model of Dark Energy and Thermodynamics of Non-Flat Accelerated Expanding Universe
Motivated by recent results on non-vanishing spatial curvature \cite{curve}
we employ the holographic model of dark energy to investigate the validity of
first and second laws of thermodynamics in non-flat (closed) universe enclosed
by apparent horizon and the event horizon measured from the sphere of
horizon named . We show that for the apparent horizon the first law is
roughly respected for different epochs while the second laws of thermodynamics
is respected while for as the system's IR cut-off first law is broken down
and second law is respected for special range of deceleration parameter. It is
also shown that at late-time universe is equal to and the
thermodynamic laws are hold, when the universe has non-vanishing curvature.
Defining the fluid temperature to be proportional to horizon temperature the
range for coefficient of proportionality is obtained provided that the
generalized second law of thermodynamics is hold.Comment: 12 pages, no figure, abstract and text extended, references added,
accepted for publication in JCA
86-GBaud subcarrier multiplexed 16QAM signal generation using an electrical 90 degree hybrid and IQ mixers
We experimentally demonstrate an aggregate 86-GBaud (over three sub-bands and one polarization) signal generation based on subcarrier multiplexing technique using IQ mixers, an electrical 90 degree hybrid, and diplexers. The electrical hybrid allows transmitter-side digital signal processing to be simplified to pulse shaping and digital pre-emphasis. We verified the configuration by testing the performance of an 86-GBaud Nyquist-shaped 16 quadrature amplitude modulation signal with differential bit encoding. The implementation penalty assuming 7% hard-decision forward error correction is reduced to 2 dB by utilizing a 31-tap decision-directed least mean square based multiple-input multiple-output equalizer for sideband crosstalk mitigation
The DArk Matter Particle Explorer mission
The DArk Matter Particle Explorer (DAMPE), one of the four scientific space
science missions within the framework of the Strategic Pioneer Program on Space
Science of the Chinese Academy of Sciences, is a general purpose high energy
cosmic-ray and gamma-ray observatory, which was successfully launched on
December 17th, 2015 from the Jiuquan Satellite Launch Center. The DAMPE
scientific objectives include the study of galactic cosmic rays up to
TeV and hundreds of TeV for electrons/gammas and nuclei respectively, and the
search for dark matter signatures in their spectra. In this paper we illustrate
the layout of the DAMPE instrument, and discuss the results of beam tests and
calibrations performed on ground. Finally we present the expected performance
in space and give an overview of the mission key scientific goals.Comment: 45 pages, including 29 figures and 6 tables. Published in Astropart.
Phy
Measurement of the chi_{c2} Polarization in psi(2S) to gamma chi_{c2}
The polarization of the chi_{c2} produced in psi(2S) decays into gamma
chi_{c2} is measured using a sample of 14*10^6 psi(2S) events collected by
BESII at the BEPC. A fit to the chi_{c2} production and decay angular
distributions in psi(2S) to gamma chi_{c2}, chi_{c2} to pi pi and KK yields
values x=A_1/A_0=2.08+/-0.44 and y=A_2/A_0=3.03 +/-0.66, with a correlation
rho=0.92 between them, where A_{0,1,2} are the chi_{c2} helicity amplitudes.
The measurement agrees with a pure E1 transition, and M2 and E3 contributions
do not differ significantly from zero.Comment: 6 pages, 4 figures, 1 tabl
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