1,132 research outputs found
Photon polarization entanglement induced by biexciton: experimental evidence for violation of Bell's inequality
We have investigated the polarization entanglement between photon pairs
generated from a biexciton in a CuCl single crystal via resonant hyper
parametric scattering. The pulses of a high repetition pump are seen to provide
improved statistical accuracy and the ability to test Bell's inequality. Our
results clearly violate the inequality and thus manifest the quantum
entanglement and nonlocality of the photon pairs. We also analyzed the quantum
state of our photon pairs using quantum state tomography.Comment: 4 pages, 5 figure
Properties of the CO and HO MOLsphere of the red supergiant Betelgeuse from VLTI/AMBER observations
Context. Betelgeuse is the closest red supergiant (RSG); therefore, it is
well suited for studying the complex processes in its atmosphere that lead to
the chemical enrichment of the interstellar medium. Aims. We intend to
investigate the shape and composition of the close molecular layer (also known
as the MOLsphere) that surrounds the star. This analysis is part of a wider
program that aims at understanding the dynamics of the circumstellar envelope
of Betelgeuse. Methods. On January and February 2011, Betelgeuse was observed
using the Astronomical Multi-BEam combineR (AMBER) instrument of the Very Large
Telescope Interferometer (VLTI) in the H and K bands. Using the medium spectral
resolution of the instrument (R 1500), we were able to investigate the
carbon monoxide band heads and the water-vapor bands. We used two different
approaches to analyse our data: a model fit in both the continuum and
absorption lines and then a fit with a Radiative HydroDynamics (RHD)
simulation. Results. Using the continuum data, we derive a uniform disk
diameter of ~mas, a power law type limb-darkened disk diameter
of ~mas and a limb-darkening exponent of .
Within the absorption lines, using a single layer model, we obtain parameters
of the MOLsphere. Using a RHD simulation, we unveil the convection pattern in
the visibilities. Conclusions. We derived a new value of the angular diameter
of Betelgeuse in the K band continuum. Our observations in the absorption lines
are well reproduced by a molecular layer at 1.2 stellar radii containing both
CO and HO. The visibilities at higher spatial frequencies are matching a
convection pattern in a RHD simulation.Comment: 13 pages, 11 figures, accepted for publication in Astronomy &
Astrophysics; Language editin
Detection of Dark Matter Concentrations in the Field of Cl 1604+4304 from Weak Lensing Analysis
We present a weak-lensing analysis of a region around the galaxy cluster Cl
1604+4304 (z=0.897) on the basis of the deep observations with the HST/WFPC2.
We apply a variant of Schneider's aperture mass technique to the observed WFPC2
field and obtain the distribution of weak-lensing signal-to-noise (S/N) ratio
within the field. The resulting S/N map reveals a clear pronounced peak located
about 1.7 arcmin (850h_{50}^{-1} kpc at z=0.897) southwest of the second peak
associated with the optical cluster center determined from the dynamical
analysis of Postman et al. A non-linear finite-field inversion method has been
used to reconstruct the projected mass distribution from the observed shear
field. The reconstructed mass map shows a super-critical feature at the
location of the S/N peak as well as in the cluster central region. Assuming the
redshift distribution of field galaxies, we obtain the total mass in the
observed field to be 1.0 h_{50}^{-1} 10^{15} M_sun for =1.0. The estimated
mass within a circular aperture of radius 280h_{50}^{-1} kpc centered on the
dark clump is 2.4h_{50}^{-1} 10^{14} M_sun. We have confirmed the existence of
the ` dark ' mass concentration from another deep HST observation with a
slightly different ~20 arcsec pointing.Comment: 7 pages, 3 figure
The evolution of the peculiar Type Ia supernova SN 2005hk over 400 days
photometry and medium resolution optical spectroscopy of peculiar
Type Ia supernova SN 2005hk are presented and analysed, covering the
pre-maximum phase to around 400 days after explosion. The supernova is found to
be underluminous compared to "normal" Type Ia supernovae. The photometric and
spectroscopic evolution of SN 2005hk is remarkably similar to the peculiar Type
Ia event SN 2002cx. The expansion velocity of the supernova ejecta is found to
be lower than normal Type Ia events. The spectra obtained \gsim 200 days
since explosion do not show the presence of forbidden [\ion{Fe}{ii}],
[\ion{Fe}{iii}] and [\ion{Co}{iii}] lines, but are dominated by narrow,
permitted \ion{Fe}{ii}, NIR \ion{Ca}{ii} and \ion{Na}{i} lines with P-Cygni
profiles. Thermonuclear explosion model with Chandrasekhar mass ejecta and a
kinetic energy smaller (\KE = 0.3 \times 10^{51} {\rm ergs}) than that of
canonical Type Ia supernovae is found to well explain the observed bolometric
light curve. The mass of \Nifs synthesized in this explosion is 0.18 \Msun.
The early spectra are successfully modeled with this less energetic model with
some modifications of the abundance distribution. The late spectrum is
explained as a combination of a photospheric component and a nebular component.Comment: Accepted for publication in The Astrophysical Journal. Minor
revision, discussion section adde
Axial anomaly with the overlap-Dirac operator in arbitrary dimensions
We evaluate for arbitrary even dimensions the classical continuum limit of
the lattice axial anomaly defined by the overlap-Dirac operator. Our
calculational scheme is simple and systematic. In particular, a powerful
topological argument is utilized to determine the value of a lattice integral
involved in the calculation. When the Dirac operator is free of species
doubling, the classical continuum limit of the axial anomaly in various
dimensions is combined into a form of the Chern character, as expected.Comment: 9 pages, uses JHEP.cls and amsfonts.sty, the final version to appear
in JHE
On the origin of the Tully-Fisher relation
We discuss the origin of the Tully-Fisher (TF) relation using the
-body/SPH method, which includes cooling, star formation and stellar
feedback of energy, mass and metals. We consider initially rotating overdense
spheres, and trace formation processes of disk galaxies from to in
the Cold Dark Matter (CDM) cosmology. To clarify the origin of the TF relation,
we simulate formation of 14 galaxies with different masses and spin parameters,
and compute observable values, such as the total magnitude and the line-width.
We find that the simulated galaxies reproduce the slope and scatter of the TF
relation: the slope is originated in the difference of total galactic masses,
and the scatter is produced by the difference of initial spin parameters. As
well as the TF relation, observed features of spiral galaxies, such as the
exponential light-profile and the flat rotation curve, are reproduced in our
simulations, which were assumed {\it a priori} in past semi-analytical
approaches.Comment: 11 pages, including 6 figures, submitted to Ap
Coevolution of Supermassive Black Holes and Circumnuclear Disks
We propose a new evolutionary model of a supermassive black hole (SMBH) and a
circumnuclear disk (CND), taking into account the mass-supply from a host
galaxy and the physical states of CND. In the model, two distinct accretion
modes depending on gravitational stability of the CND play a key role on
accreting gas to a SMBH. (i) If the CMD is gravitationally unstable, energy
feedback from supernovae (SNe) supports a geometrically thick, turbulent gas
disk. The accretion in this mode is dominated by turbulent viscosity, and it is
significantly larger than that in the mode (ii), i.e., the CMD is supported by
gas pressure. Once the gas supply from the host is stopped, the high accretion
phase () changes to the low one (mode
(ii), ), but there is a delay with yr. Through this evolution, the gas-rich CND turns into the gas poor
stellar disk. We found that not all the gas supplied from the host galaxy
accrete onto the SMBH even in the high accretion phase (mode (i)), because the
part of gas is used to form stars. As a result, the final SMBH mass () is not proportional to the total gas mass supplied from the host
galaxy (); decreases with .This would indicate that it is difficult to form a SMBH with observed at high- QSOs. The evolution of the SMBH and CND would
be related to the evolutionary tracks of different type of AGNs.Comment: 11 pages, 11 figures, accepted for publication in Ap
Discovery of a new pulsating X-ray source with a 1549.1-s period, AX J183220-0840
A new pulsating X-ray source, AX J183220-0840, with a 1549.1-s period was
discovered at R.A.= 18h32m20s and Dec.=-8d40'30'' (J2000,
uncertainty=0.6degree) during an ASCA observation on the Galactic plane. The
source was observed two times, in 1997 and in 1999. A phase-averaged X-ray flux
of 1.1E-11 ergs cm-2 s-1 and pulsation period of 1549.1+/-0.4 s were
consistently obtained from these two observations. The X-ray spectrum was
represented by a flat absorbed power-law with a photon-index of =~0.8 and an
absorption column density of =~1.3E22 cm-2. Also, a signature of iron K-shell
line emission with a centroid of 6.7 keV and an equivalent width of
approximately 450 eV was detected. From the pulsation period and the iron-line
feature, AX J183220-0840 is likely to be a magnetic white dwarf binary with a
complexly absorbed thermal spectrum with a temperature of about 10 keV.Comment: 13 pages, 4 figures, accepted for publication in ApJ Letter
Antigen p57/Kip2 as a potential negative regulator of human astrocytoma growth
This study was performed to determine the relationship between p57/Kip2 and the growth of human astrocytomas. Immunohistochemical staining for p57/Kip2, p53, p16, and Ki67 antigen was performed on paraffin-embedded tissue specimens obtained from 36 patients with astrocytoma. Expression of p57/Kip2, p53, p16, and Ki67 antigen was generally increased in association with the astrocytoma tumor grade. Expression of p16 was higher in patients whose tumors express p57/Kip2 in greater than 10% of tumor cells (p < 0.05). Expression of p53 also tended to be higher, but not to a statistically significant extent, in patients whose tumors express p57/Kip2 in greater than 10% of tumor cells. These findings suggest that p57/Kip2 inhibits the growth of human astrocytomas, and may function in parallel with p16 and p53. However, p57/Kip2 is, by itself, insufficient to arrest the cellular proliferation of human astrocytomas.ArticleJOURNAL OF CLINICAL NEUROSCIENCE. 16(12):1615-1618 (2009)journal articl
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