7,768 research outputs found
Thermoelastic-damping noise from sapphire mirrors in a fundamental-noise-limited interferometer
We report the first high-precision interferometer using large sapphire
mirrors, and we present the first direct, broadband measurements of the
fundamental thermal noise in these mirrors. Our results agree well with the
thermoelastic-damping noise predictions of Braginsky, et al. [Phys. Lett. A
264, 1(1999)] and Cerdonio, et al.[Phys. Rev. D 63, 082003 (2001)], which have
been used to predict the astrophysical reach of advanced interferometric
gravitational wave detectors.Comment: 4 pages, 2 figure
Using boundary methods to compute the Casimir energy
We discuss new approaches to compute numerically the Casimir interaction
energy for waveguides of arbitrary section, based on the boundary methods
traditionally used to compute eigenvalues of the 2D Helmholtz equation. These
methods are combined with the Cauchy's theorem in order to perform the sum over
modes. As an illustration, we describe a point-matching technique to compute
the vacuum energy for waveguides containing media with different
permittivities. We present explicit numerical evaluations for perfect
conducting surfaces in the case of concentric corrugated cylinders and a
circular cylinder inside an elliptic one.Comment: To be published in the Proceedings of QFEXT09, Norman, OK
Keck Observations of the Hidden Quasar IRAS P09104+4109
We present imaging and spectro- polarimetric observations of the
ultraluminous infrared galaxy IRAS P09104+4109 using the Keck 10-m Telescope.
We detect the clear presence of broad Hb, Hg, and MgII 2800 emission lines in
the polarized flux spectra of the nucleus and of an extranuclear emission
region ~ 4" away, confirming the presence of a hidden central quasar. The
polarization of the broad Mg II emission line is high (~ 29%), consistent with
the remarkably high polarization (~ 30%-40%) observed in the extended continuum
emission. The narrow emission lines are polarized in a stratified fashion, with
the high ionization lines being polarized 0.7%-1.7% and [O II] essentially
unpolarized. The line polarizations are positively correlated with critical
density, ionization potential, and velocity width of the emission lines. This
indicates that the NLR may be partially shadowed by the putative torus, with
the higher ionization lines originating closer to the nucleus. One notable
characteristic of the extranuclear knot is that all species of Fe are markedly
absent in its spectrum, while they appear prominently in the nucleus. Our
favored interpretation is that there is a large amount of dust in the
extranuclear regions, allowing gaseous refractory metals to deposit. The
extended emission regions are most likely material shredded from nearby cluster
members and not gas condensed from the cooling flow or expelled from the
obscured quasar. Our data provide strong evidence for matter-bounded clouds in
addition to ionization-bounded clouds in the NLR. Ionization by pure velocity
shocks can be ruled out. Shocks with photoionizing precursors may be present,
but are probably not a dominant contributor to the energy input.Comment: 32 pages, including 9 figs and 2 tables, to be published in the
Astronomical Journa
Revisiting the location and environment of the central engine in NGC1068
We revisit in this paper the location of the various components observed in
the AGN of NGC1068. Discrepancies between previously published studies are
explained, and a new measurement for the absolute location of the K-band
emission peak is provided. It is found to be consistent with the position of
the central engine as derived by Gallimore (1997), Capetti (1997) and Kishimoto
(1999). A series of map overlays is then presented and discussed. Model
predictions of dusty tori show that the nuclear unresolved NIR-MIR emission is
compatible with a broad range of models: the nuclear SED alone does not
strongly constrain the torus geometry, while placing reasonable constraints on
its size and thickness. The extended MIR emission observed within the ionizing
cone is shown to be well explained by the presence of optically thick dust
clouds exposed to the central engine radiation and having a small covering
factor. Conversely, a distribution of diffuse dust particles within the
ionizing cone is discarded. A simple model for the H2 and CO emission observed
perpendicularly to the axis of the ionizing cone is proposed. We show that a
slight tilt between the molecular disc and the Compton thick central absorber
naturally reproduces the observed distribution of H2 of CO emission.Comment: 17 pages, 11 figures, revised version for A&
Dynamical Casimir effect in superconducting circuits: a numerical approach
We present a numerical analysis of the particle creation for a quantum field
in the presence of time dependent boundary conditions. Having in mind recent
experiments involving superconducting circuits, we consider their description
in terms of a scalar field in a one dimensional cavity satisfying generalized
boundary conditions that involve a time-dependent linear combination of the
field and its spatial and time derivatives. We evaluate numerically the
Bogoliubov transformation between {\it in} and {\it out}-states and find that
the rate of particle production strongly depends on whether the spectrum of the
unperturbed cavity is equidistant or not, and also on the amplitude of the
temporal oscillations of the boundary conditions. We provide analytic
justifications for the different regimes found numerically.Comment: 20 pages. 11 figure
A vestige low metallicity gas shell surrounding the radio galaxy 0943-242 at z=2.92
Observations are presented showing the doublet CIV 1550 absorption lines
superimposed on the CIV emission in the radio galaxy 0943-242. Within the
errors, the redshift of the absorption system that has a column density of
N_CIV = 10^{14.5 +- 0.1} cm-2 coincides with that of the deep Ly-alpha
absorption trough observed by Rottgering et al. (1995). The gas seen in
absorption has a resolved spatial extent of at least 13 kpc (the size of the
extended emission line region). We first model the absorption and emission gas
as co-spatial components with the same metallicity and degree of excitation.
Using the information provided by the emission and absorption line ratios of
CIV and Ly-alpha, we find that the observed quantities are incompatible with
photoionization or collisional ionization of cloudlets with uniform properties.
We therefore reject the possibility that the absorption and emission phases are
co-spatial and favour the explanation that the absorption gas has low
metallicity and is located further away from the host galaxy (than the emission
line gas). The estimated low metallicity for the absorption gas in 0943-242 (Z
\~ 1% solar) and its proposed location -outer halo outside the radio cocoon-
suggest that its existence preceeds the observed AGN phase and is a vestige of
the initial starburst at the onset of formation of the parent galaxy.Comment: 11 pages,5 figures, A&A accepte
Continuous variable entanglement measurement without phase locking
A new simple entanglement measurement method is proposed for the bright EPR
beams generated from a non-degenerate optical parametric amplifier operating at
deamplification. Due to the output signal and idler modes are frequency
degenerate and in phase, the needed phase shift of interference for the
measurement of the correlated phase quadratures and anti-correlated amplitude
quadratures can be accomplished by a quarter-wave plate and a half wave plate
without separating the signal and idler beam. Therefore, phase locking and
local oscillators are avoided.Comment: 8 pages,3 figure
Generation of Kerr non-Gaussian motional states of trapped ions
Non-Gaussian states represent a powerful resource for quantum information
protocols in the continuous variables regime. Cat states, in particular, have
been produced in the motional degree of freedom of trapped ions by controlled
displacements dependent on the ionic internal state. An alternative method
harnesses the Kerr nonlinearity naturally existent in this kind of system. We
present detailed calculations confirming its feasibility for typical
experimental conditions. Additionally, this method permits the generation of
complex non-Gaussian states with negative Wigner functions. Especially,
superpositions of many coherent states are achieved at a fraction of the time
necessary to produce the cat state.Comment: 6 pages, 5 figure
- …