102,395 research outputs found
The overmassive black hole in NGC 1277: new constraints from molecular gas kinematics
We report the detection of CO(1-0) emission from NGC 1277, a lenticular
galaxy in the Perseus Cluster. NGC 1277 has previously been proposed to host an
overmassive black hole (BH) compared to the galaxy bulge luminosity (mass),
based on stellar-kinematic measurements. The CO(1-0) emission, observed with
the IRAM Plateau de Bure Interferometer (PdBI) using both, a more compact
(2.9-arcsec resolution) and a more extended (1-arcsec resolution)
configuration, is likely to originate from the dust lane encompassing the
galaxy nucleus at a distance of 0.9 arcsec (~320 pc). The double-horned CO(1-0)
profile found at 2.9-arcsec resolution traces of
molecular gas, likely orbiting in the dust lane at $\sim 550\ \mathrm{km\
s^{-1}}\sim 2\times 10^{10}\
M_\odot\sim
1.7\times 10^{10}\ M_\odotM/L_V=6.3\sim 5\times 10^{9}\ M_\odotM/L_V=10$. While the molecular gas reservoir
may be associated with a low level of star formation activity, the extended
2.6-mm continuum emission is likely to originate from a weak AGN, possibly
characterized by an inverted radio-to-millimetre spectral energy distribution.
Literature radio and X-ray data indicate that the BH in NGC 1277 is also
overmassive with respect to the Fundamental Plane of BH activity.Comment: 15 pages, 13 figures; accepted for publication in MNRAS on 20 January
2016; updated version including minor changes and note added in proo
Unchanged thermopower enhancement at the semiconductor-metal transition in correlated FeSbTe
Substitution of Sb in FeSb by less than 0.5% of Te induces a transition
from a correlated semiconductor to an unconventional metal with large effective
charge carrier mass . Spanning the entire range of the semiconductor-metal
crossover, we observed an almost constant enhancement of the measured
thermopower compared to that estimated by the classical theory of electron
diffusion. Using the latter for a quantitative description one has to employ an
enhancement factor of 10-30. Our observations point to the importance of
electron-electron correlations in the thermal transport of FeSb, and
suggest a route to design thermoelectric materials for cryogenic applications.Comment: 3 pages, 3 figures, accepted for publication in Appl. Phys. Lett.
(2011
High-Order Adiabatic Approximation for Non-Hermitian Quantum System and Complexization of Berry's Phase
In this paper the evolution of a quantum system drived by a non-Hermitian
Hamiltonian depending on slowly-changing parameters is studied by building an
universal high-order adiabatic approximation(HOAA) method with Berry's phase
,which is valid for either the Hermitian or the non-Hermitian cases. This
method can be regarded as a non-trivial generalization of the HOAA method for
closed quantum system presented by this author before. In a general situation,
the probabilities of adiabatic decay and non-adiabatic transitions are
explicitly obtained for the evolution of the non-Hermitian quantum system. It
is also shown that the non-Hermitian analog of the Berry's phase factor for the
non-Hermitian case just enjoys the holonomy structure of the dual linear bundle
over the parameter manifold. The non-Hermitian evolution of the generalized
forced harmonic oscillator is discussed as an illustrative examples.Comment: ITP.SB-93-22,17 page
Antenna Miniaturization Based on Supperscattering Effect
Antennas are essential components of all existing radio equipments. The miniaturization of antenna is a key issue of antenna technology. Based on supperscattering effect, we found that when a small horn antenna is located inside of a dielectric core and covered with a complementary layer, its far field radiation pattern will be equivalent to a large horn antenna. The complementary layer with only axial parameters varying with radius is obtained using coordinate transformation theory. Besides, the influence of loss and perturbations of parameters on supperscattering effect is also investigated. Results show that the device is robust against the perturbation in the axial material parameters when the refractive index is kept invariant. Full-wave simulations based on finite element method are performed to validate the design
The evolution of HI and CIV quasar absorption line systems at 1.9 < z < 3.2
We have investigated the distribution and evolution of ~3100 intergalactic HI
absorbers with HI column densities log N(HI) = [12.75, 17.0] at 1.9 < z < 3.2,
using 18 high resolution, high S/N quasar spectra obtained from the ESO
VLT/UVES archive. We used two sets of Voigt profile fitting analysis, one
including all the available high-order Lyman lines to obtain reliable HI column
densities of saturated lines, and another using only the Ly-alpha lines. There
is no significant difference between the results from the two fits. Combining
our results with literature data, the mean number density at 0 < z < 4 is not
well described by a single power law and strongly suggests that its evolution
slows down at z < 1.5 at the high and low column density ranges. We also
divided our entire HI absorbers at 1.9 < z < 3.2 into two samples, the
unenriched forest and the CIV-enriched forest, depending on whether HI lines
are associated with CIV at log N(CIV) > 12.2 within a given velocity range. The
entire HI column density distribution function (CDDF) can be described as the
combination of these two well-characterised populations which overlap at log
N(HI) ~ 15. At log N(HI) < 15, the unenriched forest dominates, showing a
similar power-law distribution to the entire forest. The CIV-enriched forest
dominates at log N(HI) > 15, with its distribution function proportional to
N(HI)^(-1.45). However, it starts to flatten out at lower N(HI), since the
enriched forest fraction decreases with decreasing N(HI). The deviation from
the power law at log N(HI) = [14, 17] shown in the CDDF for the entire HI
sample is a result of combining two different HI populations with a different
CDDF shape. The total HI mass density relative to the critical density is
Omega(HI) ~ 1.6 x 10^(-6) h^(-1), where the enriched forest accounts for ~40%
of Omega(HI).Comment: 26 pages, 20 figures, accepted for AA, in pres
An quantum approach of measurement based on the Zurek's triple model
In a close form without referring the time-dependent Hamiltonian to the total
system, a consistent approach for quantum measurement is proposed based on
Zurek's triple model of quantum decoherence [W.Zurek, Phys. Rev. D 24, 1516
(1981)]. An exactly-solvable model based on the intracavity system is dealt
with in details to demonstrate the central idea in our approach: by peeling off
one collective variable of the measuring apparatus from its many degrees of
freedom, as the pointer of the apparatus, the collective variable de-couples
with the internal environment formed by the effective internal variables, but
still interacts with the measured system to form a triple entanglement among
the measured system, the pointer and the internal environment. As another
mechanism to cause decoherence, the uncertainty of relative phase and its
many-particle amplification can be summed up to an ideal entanglement or an
Shmidt decomposition with respect to the preferred basis.Comment: 22pages,3figure
Use of integrated optical waveguide probes as an alternative to fiber probes for sensing of light backscattered from small volumes
We show that for light collection from thin samples, integrated probes can present a higher efficiency than conventional fiber probes, despite having a smaller collection area. Simulation results are validated by experiments
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