24,142 research outputs found
Reply to Comment on: "Are stress-free membranes really 'tensionless'?"
This is a reply to a comment on the paper arXiv:1204.2075 "Are stress-free
membranes really tensionless ?" (EPL 95,28008 (2011))
Local structure in nematic and isotropic liquid crystals
By computer simulations of systems of ellipsoids, we study the influence of
the isotropic/nematic phase transition on the direct correlation functions
(DCF) in anisotropic fluids. The DCF is determined from the pair distribution
function by solving the full Ornstein-Zernike equation, without any
approximations. Using a suitable molecular-fixed reference frame, we can
distinguish between two qualitatively different contributions to the DCF: One
which preserves rotational invariance, and one which breaks it and vanishes in
the isotropic phase. We find that the symmetry preserving contribution is
barely affected by the phase transition. However, symmetry breaking
contributions emerge in the nematic phase and may become quite substantial.
Thus the DCF in a nematic fluid is not rotationally invariant. In the isotropic
fluid, the DCF is in good agreement with the prediction of the Percus-Yevick
theory.Comment: to appear in J. Chem. Phy
The Dirac propagator in the Kerr-Newman metric
We give an alternative proof of the completeness of the Chandrasekhar ansatz
for the Dirac equation in the Kerr-Newman metric. Based on this, we derive an
integral representation for smooth compactly supported functions which in turn
we use to derive an integral representation for the propagator of solutions of
the Cauchy problem with initial data in the above class of functions. As a
by-product, we also obtain the propagator for the Dirac equation in the
Minkowski space-time in oblate spheroidal coordinates.Comment: 29 pages, modifications in the abstract and in the introduction,
small improvements in section 2.
Raman Scattered He II 6545 Line in the Symbiotic Star V1016 Cygni
We present a spectrum of the symbiotic star V1016 Cyg observed with the 3.6 m
Canada-France-Hawaii Telescope, in order to illustrate a method to measure the
covering factor of the neutral scattering region around the giant component
with respect to the hot emission region around the white dwarf component. In
the spectrum, we find broad wings around H and a broad emission feature
around 6545 that is blended with the [N II] 6548 line.
These two features are proposed to be formed by Raman scattering by atomic
hydrogen, where the incident radiation is proposed to be UV continuum radiation
around Ly in the former case and He II 1025 emission line
arising from transitions for the latter feature. We remove the
H wings by a template Raman scattering wing profile and subtract the [N
II] 6548 line using the 3 times stronger [N II] 6583
feature in order to isolate the He II Raman scattered 6545 \AA line. We obtain
the flux ratio of the He II 6560 emission
line and the 6545 \AA feature for V1016 Cyg. Under the assumption that the He
II emission from this object is isotropic, this ratio is converted to the ratio
of the number of the incident photons and that
of the scattered photons. This implies that the scattering region with H I
column density covers 17 per cent of the
emission region. By combining the presumed binary period yrs of this
system we infer that a significant fraction of the slow stellar wind from the
Mira component is ionized and that the scattering region around the Mira
extends a few tens of AU, which is closely associated with the mass loss
process of the Mira component.Comment: 12 pages, 6 figures, accepted for publication in Ap
Spectropolarimetry of the borderline Seyfert 1 galaxy ESO 323-G077
We report the detection of high linear polarization in the bright Seyfert 1
galaxy ESO 323-G077. Based on optical spectropolarimetry with FORS1 at the VLT
we find a continuum polarization which ranges from 2.2 % at 8300A to 7.5 % at
3600A. Similar amounts of linear polarization are found for the broad emission
lines, while the narrow lines are not polarized. The position angle of the
polarization is independent of the wavelength and found to be perpendicular to
the orientation of the extended [OIII] emission cone of this galaxy. Within the
standard model of Seyfert nuclei the observations can be well understood
assuming that this AGN is observed at an inclination angle where the nucleus is
partially obscured and seen mainly indirectly in the light scattered by dust
clouds within or above the torus and the illuminated inner edge of the dust
torus itself. Hence we conclude that ESO 323-G077 is a borderline Seyfert 1
galaxy which can provide important information on the geometric properties of
active nuclei
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