16,403 research outputs found
The properties of active galaxies at the extreme of eigenvector 1
Eigenvector 1 (EV1) is the formal parameter which allows the introduction of
some order in the properties of the unobscured type 1 active galaxies. We aim
to understand the nature of this parameter by analyzing the most extreme
examples of quasars with the highest possible values of the corresponding
eigenvalues . We selected the appropriate sources from the Sloan
Digital Sky Survey (SDSS) and performed detailed modeling, including various
templates for the Fe II pseudo-continuum and the starlight contribution to the
spectrum. Out of 27 sources with larger than 1.3 and with the
measurement errors smaller than 20\% selected from the SDSS quasar catalog,
only six sources were confirmed to have a high value of , defined as
being above 1.3. All other sources have of approximately 1. Three
of the high objects have a very narrow H line, below 2100 km
s but three sources have broad lines, above 4500 km s, that do
not seem to form a uniform group, differing considerably in black hole mass and
Eddington ratio; they simply have a very similar EW([OIII]5007) line.
Therefore, the interpretation of the EV1 remains an open issue.Comment: Astronomy and Astrophysics (in press
Fidelity susceptibility in the two-dimensional spin-orbit models
We study the quantum phase transitions in the two-dimensional spin-orbit
models in terms of fidelity susceptibility and reduced fidelity susceptibility.
An order-to-order phase transition is identified by fidelity susceptibility in
the two-dimensional Heisenberg XXZ model with Dzyaloshinsky-Moriya interaction
on a square lattice. The finite size scaling of fidelity susceptibility shows a
power-law divergence at criticality, which indicates the quantum phase
transition is of second order. Two distinct types of quantum phase transitions
are witnessed by fidelity susceptibility in Kitaev-Heisenberg model on a
hexagonal lattice. We exploit the symmetry of two-dimensional quantum compass
model, and obtain a simple analytic expression of reduced fidelity
susceptibility. Compared with the derivative of ground-state energy, the
fidelity susceptibility is a bit more sensitive to phase transition. The
violation of power-law behavior for the scaling of reduced fidelity
susceptibility at criticality suggests that the quantum phase transition
belongs to a first-order transition. We conclude that fidelity susceptibility
and reduced fidelity susceptibility show great advantage to characterize
diverse quantum phase transitions in spin-orbit models.Comment: 11 pages. 11 figure
Structural lifetime assessment for the DEMO divertor targets: Design-by-analysis approach and outstanding issues
Quantum entanglement of spin-1 bosons with coupled ground states in optical lattices
We examine particle entanglement, characterized by pseudo-spin squeezing, of
spin-1 bosonic atoms with coupled ground states in a one-dimensional optical
lattice. Both the superfluid and Mott-insulator phases are investigated
separately for ferromagnetic and antiferromagnetic interactions. Mode
entanglement is also discussed in the Mott insulating phase. The role of a
small but nonzero angle between the polarization vectors of counter-propagating
lasers forming the optical lattice on quantum correlations is investigated as
well.Comment: 18 pages, 8 figures. To be published in Journal of Physics
The mass of the black hole in RE J1034+396
The black hole mass measurement in active galaxies is a challenge,
particularly in sources where the reverberation method cannot be applied. We
aim to determine the black hole mass in a very special object, RE J1034+396,
one of the two AGN with QPO oscillations detected in X-rays, and a single
bright AGN with optical band totally dominated by starlight. We fit the stellar
content using the code starlight, and the broad band disk contribution to
optical/UV/X-ray emission is modeled with optxagnf. We also determine the black
hole mass using several other independent methods. Various methods give
contradictory results. Most measurements of the blacc hole mass are in the
range 1.e6-1.e7 Msun, and the measurements based on dynamics give higher values
than measurements based on Hbeta and Mg II emission lines.Comment: A&A, in pres
Variational perturbation approach to the Coulomb electron gas
The efficiency of the variational perturbation theory [Phys. Rev. C {\bf 62},
045503 (2000)] formulated recently for many-particle systems is examined by
calculating the ground state correlation energy of the 3D electron gas with the
Coulomb interaction. The perturbation beyond a variational result can be
carried out systematically by the modified Wick's theorem which defines a
contraction rule about the renormalized perturbation. Utilizing the theorem,
variational ring diagrams of the electron gas are summed up. As a result, the
correlation energy is found to be much closer to the result of the Green's
function Monte Carlo calculation than that of the conventional ring
approximation is.Comment: 4 pages, 3 figure
A hybrid wetland map for China: A synergistic approach using census and spatially explicit datasets
Wetlands play important ecological, economic, and cultural roles in societies around the world. However, wetland degradation has become a serious ecological issue, raising the global sustainability concern. An accurate wetland map is essential for wetland management. Here we used a fuzzy method to create a hybrid wetland map for China through the combination of five existing wetlands datasets, including four spatially explicit wetland distribution data and one wetland census. Our results show the total wetland area is 384,864 km2, 4.08% of China's national surface area. The hybrid wetland map also shows spatial distribution of wetlands with a spatial resolution of 1 km. The reliability of the map is demonstrated by comparing it with spatially explicit datasets on lakes and reservoirs. The hybrid wetland map is by far the first wetland mapping that is consistent with the statistical data at the national and provincial levels in China. It provides a benchmark map for research on wetland protection and management. The method presented here is applicable for not only wetland mapping but also for other thematic mapping in China and beyond
Scattering of short laser pulses from trapped fermions
We investigate the scattering of intense short laser pulses off trapped cold
fermionic atoms. We discuss the sensitivity of the scattered light to the
quantum statistics of the atoms. The temperature dependence of the scattered
light spectrum is calculated. Comparisons are made with a system of classical
atoms who obey Maxwell-Boltzmann statistics. We find the total scattering
increases as the fermions become cooler but eventually tails off at very low
temperatures (far below the Fermi temperature). At these low temperatures the
fermionic degeneracy plays an important role in the scattering as it inhibits
spontaneous emission into occupied energy levels below the Fermi surface. We
demonstrate temperature dependent qualitative changes in the differential and
total spectrum can be utilized to probe quantum degeneracy of trapped Fermi gas
when the total number of atoms are sufficiently large . At smaller
number of atoms, incoherent scattering dominates and it displays weak
temperature dependence.Comment: updated figures and revised content, submitted to Phys.Rev.
- …