22,335 research outputs found
Active Faraday optical frequency standards
We propose the mechanism of active Faraday optical clock, and experimentally
demonstrate active Faraday optical frequency standards based on 852 nm narrow
bandwidth Faraday atomic filter by the method of velocity-selective optical
pumping of cesium vapor. The center frequency of the active Faraday optical
frequency standards is determined by the cesium 6 = 4 to 6
= 4 and 5 crossover transition line. The optical heterodyne
beat between two similar independent setups shows that the frequency linewidth
reaches 996(26) Hz, which is 5.3 10 times smaller than the
natural linewidth of the cesium 852 nm transition line. The maximum emitted
light power reaches 75 \upmuW. The active Faraday optical frequency standards
reported here have advantages of narrow linewidth and reduced cavity pulling,
which can readily be extended to other atomic transition lines of alkali and
alkaline-earth metal atoms trapped in optical lattices at magic wavelengths,
making it useful for new generation of optical atomic clocks.Comment: 4 pages, 4 figure
Anisotropy in Inflation with Non-minimal Coupling
We study a new anisotropic inflation model, with an inflaton field
nonminimally coupled with the gravity and a vector field. We find that the
anisotropic attractor solution exists not only in the weak curvature coupling
limit, but more interestingly in the strong curvature coupling limit as well.
We show that in the strong curvature coupling limit, the contribution from the
anisotropy is greatly suppressed.Comment: V2, 12 pages, 3 figures, numerical analysis adde
Anti-shadowing Effect on Charmonium Production at a Fixed-target Experiment Using LHC Beams
We investigate charmonium production in Pb+Pb collisions at LHC beam energy
=2.76 A TeV at fixed-target experiment (=72 GeV). In the frame of a transport approach including cold
and hot nuclear matter effects on charmonium evolution, we focus on the
anti-shadowing effect on the nuclear modification factors and
for the yield and transverse momentum. The yield is more suppressed at
less forward rapidity (2) than that at very forward
rapidity (4) due to the shadowing and anti-shadowing in
different rapidity bins.Comment: 7 pages, 3 figures; submitted to Advances in High Energy Physics.
arXiv admin note: text overlap with arXiv:1409.555
Surface Potential Decay and DC Conductivity of TiO2-based Polyimide Nanocomposite Films
Polymer nanocomposites have attracted wide interest as a method of enhancing polymer properties and extending their applications. Surface potential decay has been used widely as a tool to monitor charge transport and trapping characteristics of insulating materials. Polyimide (PI) as an engineering material has been paid more attention due to high thermal and chemical stability, good mechanical property and excellent insulating property in a wide range of temperature. There has been a lot of work over last few years on optical, thermal and mechanical properties of polyimide nanocomposites. However, little attention has been given to the effect of nano-fillers on charge transport and trapping in polyimide nanocomposites. In the present paper, pure, 1%, 3%, 5% and 7% polyimide nanocomposites was examined by using surface potential decay in conjunction with dc conductivity measurement and both experiments showed that 3% is the optimal value for electrical insulation
Active optical clock based on four-level quantum system
Active optical clock, a new conception of atomic clock, has been proposed
recently. In this report, we propose a scheme of active optical clock based on
four-level quantum system. The final accuracy and stability of two-level
quantum system are limited by second-order Doppler shift of thermal atomic
beam. To three-level quantum system, they are mainly limited by light shift of
pumping laser field. These limitations can be avoided effectively by applying
the scheme proposed here. Rubidium atom four-level quantum system, as a typical
example, is discussed in this paper. The population inversion between
and states can be built up at a time scale of s.
With the mechanism of active optical clock, in which the cavity mode linewidth
is much wider than that of the laser gain profile, it can output a laser with
quantum-limited linewidth narrower than 1 Hz in theory. An experimental
configuration is designed to realize this active optical clock.Comment: 5 page
Thermal Charm and Charmonium Production in Quark Gluon Plasma
We study the effect of thermal charm production on charmonium regeneration in
high energy nuclear collisions. By solving the kinetic equations for charm
quark and charmonium distributions in Pb+Pb collisions, we calculate the global
and differential nuclear modification factors and
for s. Due to the thermal charm production in hot medium,
the charmonium production source changes from the initially created charm
quarks at SPS, RHIC and LHC to the thermally produced charm quarks at Future
Circular Collider (FCC), and the suppression () observed so
far will be replaced by a strong enhancement () at FCC at low
transverse momentum.Comment: 6 pages, 3 figure
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