9,078 research outputs found
Quark Condensates in Nuclear Matter in the Global Color Symmetry Model of QCD
With the global color symmetry model being extended to finite chemical
potential, we study the density dependence of the local and nonlocal scalar
quark condensates in nuclear matter. The calculated results indicate that the
quark condensates increase smoothly with the increasing of nuclear matter
density before the critical value (about 12) is reached. It also
manifests that the chiral symmetry is restored suddenly as the density of
nuclear matter reaches its critical value. Meanwhile, the nonlocal quark
condensate in nuclear matter changes nonmonotonously against the space-time
distance among the quarks.Comment: 15 pages, 3 figure
Evolution of pore structure, submaceral composition and produced gases of two Chinese coals during thermal treatment
This research was funded by the Research Program for Excellent Doctoral Dissertation Supervisor of Beijing (grant no. YB20101141501), the Fundamental Research Funds for Central Universities (grant no. 35832015136) and Key Project of Coal-based Science and Technology in Shanxi Province-CBM accumulation model and reservoir evaluation in Shanxi province (grant no. MQ2014-01).Peer reviewedPostprin
Observation of recoil-induced resonances and electromagnetically induced absorption of cold atoms in diffuse light
In this paper we report an experiment on the observation of the
recoil-induced resonances (RIR) and electromagnetically induced absorption
(EIA) of cold Rb87 atoms in diffuse light. The pump light of the RIR and the
EIA comes from the diffuse light in an integrating sphere, which also serves
the cooling light. The probe light beam is a weak laser split from the cooling
laser in order to keep the cooling and probe lasers correlated. We measured the
RIR and the EIA signal varying with the detuning of the diffuse laser light,
and also measured the temperature of the cold atoms at the different detunings.
The mechanism of RIR and EIA in the configuration with diffuse-light pumping
and laser probing is discussed, and the difference of nonlinear spectra of cold
atoms between in diffuse-light cooling system and in optical molasses as well
as in a magneto-optical trap (MOT) are studied.Comment: 9 pages, 6 figure
Reevaluation of the density dependence of nucleon radius and mass in the global color symmetry model of QCD
With the global color symmetry model (GCM) at finite chemical potential, the
density dependence of the bag constant, the total energy and the radius of a
nucleon in nuclear matter is investigated. A relation between the nuclear
matter density and the chemical potential with the action of QCD being taken
into account is obtained. A maximal nuclear matter density for the existence of
the bag with three quarks confined within is given. The calculated results
indicate that, before the maximal density is reached, the bag constant and the
total energy of a nucleon decrease, and the radius of a nucleon increases
slowly, with the increasing of the nuclear matter density. As the maximal
nuclear matter density is reached, the mass of the nucleon vanishes and the
radius becomes infinite suddenly. It manifests that a phase transition from
nucleons to quarks takes place.Comment: 18 pages, 3 figure
A feedback-driven bubble G24.136+00.436: a possible site of triggered star formation
We present a multi-wavelength study of the IR bubble G24.136+00.436. The
J=1-0 observations of CO, CO and CO were carried out with
the Purple Mountain Observatory 13.7 m telescope. Molecular gas with a velocity
of 94.8 km s is found prominently in the southeast of the bubble,
shaping as a shell with a total mass of . It is
likely assembled during the expansion of the bubble. The expanding shell
consists of six dense cores. Their dense (a few of cm) and
massive (a few of ) characteristics coupled with the broad
linewidths ( 2.5 km s) suggest they are promising sites of forming
high-mass stars or clusters. This could be further consolidated by the
detection of compact HII regions in Cores A and E. We tentatively identified
and classified 63 candidate YSOs based on the \emph{Spitzer} and UKIDSS data.
They are found to be dominantly distributed in regions with strong emission of
molecular gas, indicative of active star formation especially in the shell. The
HII region inside the bubble is mainly ionized by a O8V star(s), of the
dynamical age 1.6 Myr. The enhanced number of candidate YSOs and
secondary star formation in the shell as well as time scales involved, indicate
a possible scenario of triggering star formation, signified by the "collect and
collapse" process.Comment: 13 pages, 10 figures, 4 tables, accepted by Ap
Topological Imbert-Fedorov shift in Weyl semimetals
The Goos-H\"anchen (GH) shift and the Imbert-Fedorov (IF) shift are optical
phenomena which describe the longitudinal and transverse lateral shifts at the
reflection interface, respectively. Here, we report the GH and IF shifts in
Weyl semimetals (WSMs) - a promising material harboring low energy Weyl
fermions, a massless fermionic cousin of photons. Our results show that GH
shift in WSMs is valley-independent which is analogous to that discovered in a
2D relativistic material - graphene. However, the IF shift has never been
explored in non-optical systems, and here we show that it is valley-dependent.
Furthermore, we find that the IF shift actually originates from the topological
effect of the system. Experimentally, the topological IF shift can be utilized
to characterize the Weyl semimetals, design valleytronic devices of high
efficiency, and measure the Berry curvature
Cooling mechanical resonators to quantum ground state from room temperature
Ground-state cooling of mesoscopic mechanical resonators is a fundamental
requirement for test of quantum theory and for implementation of quantum
information. We analyze the cavity optomechanical cooling limits in the
intermediate coupling regime, where the light-enhanced optomechanical coupling
strength is comparable with the cavity decay rate. It is found that in this
regime the cooling breaks through the limits in both the strong and weak
coupling regimes. The lowest cooling limit is derived analytically at the
optimal conditions of cavity decay rate and coupling strength. In essence,
cooling to the quantum ground state requires , with being the mechanical quality factor and
being the thermal phonon number. Remarkably, ground-state
cooling is achievable starting from room temperature, when mechanical
-frequency product , and both of the
cavity decay rate and the coupling strength exceed the thermal decoherence
rate. Our study provides a general framework for optimizing the backaction
cooling of mesoscopic mechanical resonators
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