633 research outputs found
About the connection between the power spectrum of the Cosmic Microwave Background and the Fourier spectrum of rings on the sky
In this article we present and study a scaling law of the CMB
Fourier spectrum on rings which allows us (i) to combine spectra corresponding
to different colatitude angles (e.g. several detectors at the focal plane of a
telescope), and (ii) to recover the power spectrum once the
coefficients have been measured. This recovery is performed numerically below
the 1% level for colatitudes degrees. In addition, taking
advantage of the smoothness of the and of the , we provide
analytical expressions which allow to recover one of the spectrum at the 1%
level, the other one being known.Comment: 8 pages, 8 figure
Probing neutrino masses with CMB lensing extraction
We evaluate the ability of future cosmic microwave background (CMB)
experiments to measure the power spectrum of large scale structure using
quadratic estimators of the weak lensing deflection field. We calculate the
sensitivity of upcoming CMB experiments such as BICEP, QUaD, BRAIN, ClOVER and
PLANCK to the non-zero total neutrino mass M_nu indicated by current neutrino
oscillation data. We find that these experiments greatly benefit from lensing
extraction techniques, improving their one-sigma sensitivity to M_nu by a
factor of order four. The combination of data from PLANCK and the SAMPAN
mini-satellite project would lead to sigma(M_nu) = 0.1 eV, while a value as
small as sigma(M_nu) = 0.035 eV is within the reach of a space mission based on
bolometers with a passively cooled 3-4 m aperture telescope, representative of
the most ambitious projects currently under investigation. We show that our
results are robust not only considering possible difficulties in subtracting
astrophysical foregrounds from the primary CMB signal but also when the minimal
cosmological model (Lambda Mixed Dark Matter) is generalized in order to
include a possible scalar tilt running, a constant equation of state parameter
for the dark energy and/or extra relativistic degrees of freedom.Comment: 13 pages, 4 figures. One new figure and references added. Version
accepted for publicatio
Nondissipative Addressing for Time-Division SQUID Multiplexing
International audienceRecent and future astronomical instruments are based on a focal plane mapped by a large array of superconducting bolometers. Cryogenic analog multiplexing readout techniques, based on superconducting quantum interference devices (SQUIDs), are currently developed to achieve the readout of large arrays of this kind of low noise background-limited detectors. To effectively reduce the number of cryogenic wires (particularly, SQUID biasing), line/column addressing is currently used in time-division multiplexing, i.e., same biasing is applied to a few SQUIDs (on a line) of different columns. This technique should dramatically increase power consumption if parallel biasing is applied via resistors to isolate each column; the power budget is particularly limited on this kind of front-end cryogenic readout. A design with one transformer per SQUID is also used to read out SQUID biased in series with no excess of consumption and crosstalk. We propose here a new biasing technique using simple surface-mounted capacitors, which is easier to implement. These capacitors are used to parallel bias SQUIDs without additional Joule effect while minimizing crosstalk. However, capacitors do not allow dc biasing and need a current mean value equal to zero to avoid biasing source saturation. We have then tested square current biasing through capacitors on a commercial SQUID. This measurement shows that capacitors are able to proper bias SQUID and then to perform a nondissipative addressing for time-division SQUID multiplexing
Charting the New Frontier of the Cosmic Microwave Background Polarization
The anisotropies of the cosmic microwave background are a gold mine for
cosmology and fundamental physics. ESA's Planck satellite should soon extract
all information from the temperature vein but will be limited concerning the
measurement of the degree of polarization of the anisotropies. This
polarization information allows new independent tests of the standard
cosmological paradigm, improves knowledge of cosmological parameters and last
but not least is the best window available for constraining the physics of the
very early universe, particularly the expected background of primordial
gravitational waves. But exploiting this vein will be a challenge, since the
sensitivity required is {\em at least} 10 times better than what Planck might
achieve at best, with the necessary matching level of control of all
systematics effects, both instrumental and astrophysical (foregrounds). We here
recall the cosmological context and the case for CMB polarization studies. We
also briefly introduce the SAMPAN project, a design study at CNES that aims at
detecting the primoridal gravitational wave background for a tensor to scalar
ratio T/S as small as 0.001.Comment: 4 pages, to appear in SF2A 2005 proceeding
Correctors for some nonlinear monotone operators
In this paper we study homogenization of quasi-linear partial differential
equations of the form -\mbox{div}\left( a\left( x,x/\varepsilon _h,Du_h\right)
\right) =f_h on with Dirichlet boundary conditions. Here the
sequence tends to as
and the map is periodic in monotone in
and satisfies suitable continuity conditions. We prove that
weakly in as where
is the solution of a homogenized problem of the form -\mbox{div}\left(
b\left( x,Du\right) \right) =f on We also derive an explicit
expression for the homogenized operator and prove some corrector results,
i.e. we find such that in
La tournĂ©e de ForĂȘt MĂ©diterranĂ©enne - RĂ©cit dâune 11e tournĂ©e Ă la dĂ©couverte des Parcs naturels dâAndalousie
Cette annĂ©e, lâassociation ForĂȘt MĂ©diterranĂ©enne a choisi dâorganiser sa tournĂ©e forestiĂšre annuelle dans le sud de lâEspagne, en Andalousie. Du 5 au 8 mai 2016, plus de vingt participants sont ainsi partis Ă la dĂ©couverte des plus grands Parcs et espaces naturels dâEspagne. Cet article est le compte rendu de ce voyage
The High Frequency Instrument of Planck: Requirements and Design
The Planck satellite is a project of the European Space Agency based on a wide international collaboration, including United States and Canadian laboratories. It is dedicated to the measurement of the anisotropy of the Cosmic Microwave Background (CMB) with unprecedented sensitivity and angular resolution. The detectors of its High frequency Instrument (HFI) are bolometers cooled down to 100 mK. Their sensitivity will be limited by the photon noise of the CMB itself at low frequencies, and of the instrument background at high frequencies. The requirements on the measurement chain are directly related to the strategy of observation used for the satellite. Due to the scanning on the sky, time features of the measurement chain are directly transformed into angular features in the sky maps. This impacts the bolometer design as well as other elements: For example, the cooling system must present outstanding temperature stability, and the amplification chain must show, down to very low frequencies, a flat noise spectrum
Use of High Sensitivity Bolometers for Astronomy: Planck High Frequency Instrument
The Planck satellite is dedicated to the measurement of the anisotropy of the Cosmic Microwave Background (CMB) with unprecedented sensitivity and angular resolution. It is a
project of the European Space Agency based on a wide international collaboration, including United States and Canadian laboratories. The detectors of its High Frequency Instrument (HFI) are bolometers cooled down to 100 mK. Their sensitivity will be limited by the photon noise of
the CMB itself at low frequencies, and of the instrument background at high frequencies. The requirements on the measurement chain are directly related to the strategy of observation used for the satellite. This impacts the bolometer design as well as other elements: The cooling system must present outstanding temperature stability, and the amplification chain must show a flat noise spectrum down to very low frequencies
Automated End to End Carrier Ethernet Provisioning over a Disaggregated WDM Metro Network with a Hierarchical SDN Control and Monitoring Platform
This demo shows how a hierarchical control plane of ONOS SDN controllers orchestrates the dynamic provisioning of end-to-end Carrier Ethernet circuits on a composite network, programming the whole data path from the CPE to the core optical equipment
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