Foreground removal requirements for measuring large-scale CMB B-modes in light of BICEP2

The most convincing confirmation that the B-mode polarization signal detected at degree scales by BICEP2 is due to the Cosmic Microwave Background (CMB) would be the measurement of its large-scale counterpart. We assess the requirements for diffuse component separation accuracy over large portions of the sky in order to measure the large-scale B-mode signal corresponding to a tensor to scalar ratio of r=0.1-0.2. We use the method proposed by Bonaldi & Ricciardi (2011) to forecast the performances of different simulated experiments taking into account noise and foreground removal issues. We do not consider instrumental systematics, and we implicitly assume that they are not the dominant source of error. If this is the case, the confirmation of an r=0.1-0.2 signal is achievable by Planck even for conservative assumptions regarding the accuracy of foreground cleaning. Our forecasts suggest that the combination of this experiment with BICEP2 will lead to an improvement of 25-45% in the constraint on r. A next-generation CMB polarization satellite, represented in this work by the COrE experiment, can reduce dramatically (by almost another order of magnitude) the uncertainty on r. In this case, however, the accuracy of foreground removal becomes critical to fully benefit from the increase in sensitivity.Comment: 8 pages, 3 figures, 1 table. Accepted by MNRA

Cosmological constraints from Sunyaev-Zeldovich cluster counts: an approach to account for missing redshifts

The accumulation of redshifts provides a significant observational bottleneck when using galaxy cluster surveys to constrain cosmological parameters. We propose a simple method to allow the use of samples where there is a fraction of the redshifts that are not known. The simplest assumption is that the missing redshifts are randomly extracted from the catalogue, but the method also allows one to take into account known selection effects in the accumulation of redshifts. We quantify the reduction in statistical precision of cosmological parameter constraints as a function of the fraction of missing redshifts for simulated surveys, and also investigate the impact of making an incorrect assumption for the distribution of missing redshifts.Comment: 6 pages, 5 figures, accepted by Ap

CMB component separation in the pixel domain

We show that the popular ILC approach is unstable in respect to the division of the sample of map pixels to the set of ``homogeneous'' subsamples. For suitable choice of such subsamples we can obtain the restored CMB signal with amplitudes ranged from zero to the amplitudes of the observed signal. We propose approach which allows us to obtain reasonable estimates of $C_\ell$ at $\ell\leq 30$ and similar to WMAP $C_\ell$ for larger $\ell$. With this approach we reduce some anomalies of the WMAP results. In particular, our estimate of the quadrupole is well consistent to theoretical one, the effect of the ``axis of evil'' is suppressed and the symmetry of the north and south galactic hemispheres increases. This results can change estimates of quadrupole polarization and the redshift of reionization of the Universe. We propose also new simple approach which can improve WMAP estimates of high $\ell$ power spectrum.Comment: 7 pages, 5 figure

A reassessment of the evidence of the Integrated Sachs-Wolfe effect through the WMAP-NVSS correlation

We reassess the estimate of the cross-correlation of the spatial distribution of the NRAO VLA Sky Survey (NVSS) radio sources with that of Cosmic Microwave Background (CMB) anisotropies from the Wilkinson Microwave Anisotropy Probe (WMAP). This re-analysis is motivated by the fact that most previous studies adopted a redshift distribution of NVSS sources inconsistent with recent data. We find that the constraints on the bias-weighted redshift distribution, b(z)xN(z), of NVSS sources, set by the observed angular correlation function, w(theta), strongly mitigate the effect of the choice of N(z). If such constraints are met, even highly discrepant redshift distributions yield NVSS-WMAP cross-correlation functions consistent with each other within statistical errors. The models favoured by recent data imply a bias factor, b(z), decreasing with increasing z, rather than constant, as assumed by most previous analyses. As a consequence, the function b(z)xN(z) has more weight at z<1, i.e. in the redshift range yielding the maximum contribution to the ISW in a standard LambdaCDM cosmology. On the whole, the NVSS turns out to be better suited for ISW studies than generally believed, even in the absence of an observational determination of the redshift distribution. The NVSS-WMAP cross-correlation function is found to be fully consistent with the prediction of the standard LambdaCDM cosmology.Comment: 6 pages, 2 figures, submitted to MNRA

Selective readout and back-action reduction for wideband acoustic gravitational wave detectors

We present the concept of selective readout for broadband resonant mass gravitational wave detectors. This detection scheme is capable of specifically selecting the signal from the contributions of the vibrational modes sensitive to the gravitational waves, and efficiently rejecting the contribution from non gravitationally sensitive modes. Moreover this readout, applied to a dual detector, is capable to give an effective reduction of the back-action noise within the frequency band of interest. The overall effect is a significant enhancement in the predicted sensitivity, evaluated at the standard quantum limit for a dual torus detector. A molybdenum detector, 1 m in diameter and equipped with a wide area selective readout, would reach spectral strain sensitivities 2x10^{-23}/sqrt{Hz} between 2-6 kHz.Comment: 9 pages, 4 figure

Inhomogeneous mechanical losses in micro-oscillators with high reflectivity coating

We characterize the mechanical quality factor of micro-oscillators covered by a highly reflective coating. We test an approach to the reduction of mechanical losses, that consists in limiting the size of the coated area to reduce the strain and the consequent energy loss in this highly dissipative component. Moreover, a mechanical isolation stage is incorporated in the device. The results are discussed on the basis of an analysis of homogeneous and non-homogeneous losses in the device and validated by a set of Finite-Element models. The contributions of thermoelastic dissipation and coating losses are separated and the measured quality factors are found in agreement with the calculated values, while the absence of unmodeled losses confirms that the isolation element integrated in the device efficiently uncouples the dynamics of the mirror from the support system. Also the resonant frequencies evaluated by Finite-Element models are in good agreement with the experimental data, and allow the estimation of the Young modulus of the coating. The models that we have developed and validated are important for the design of oscillating micro-mirrors with high quality factor and, consequently, low thermal noise. Such devices are useful in general for high sensitivity sensors, and in particular for experiments of quantum opto-mechanics

Detection of weak stochastic force in a parametrically stabilized micro opto-mechanical system

Measuring a weak force is an important task for micro-mechanical systems, both when using devices as sensitive detectors and, particularly, in experiments of quantum mechanics. The optimal strategy for resolving a weak stochastic signal force on a huge background (typically given by thermal noise) is a crucial and debated topic, and the stability of the mechanical resonance is a further, related critical issue. We introduce and analyze the parametric control of the optical spring, that allows to stabilize the resonance and provides a phase reference for the oscillator motion, yet conserving a free evolution in one quadrature of the phase space. We also study quantitatively the characteristics of our micro opto-mechanical system as detector of stochastic force for short measurement times (for quick, high resolution monitoring) as well as for the longer term observations that optimize the sensitivity. We compare a simple, naive strategy based on the evaluation of the variance of the displacement (that is a widely used technique) with an optimal Wiener-Kolmogorov data analysis. We show that, thanks to the parametric stabilization of the effective susceptibility, we can more efficiently implement Wiener filtering, and we investigate how this strategy improves the performance of our system. We finally demonstrate the possibility to resolve stochastic force variations well below 1% of the thermal noise

STREPTOMYCETES AS BIOLOGICAL CONTROL AGENTS AND PLANT GROWTH-PROMOTING BACTERIA

Developing no-chemical strategies for the control of soil borne pathogens is one of the major issues for the cultivation of leafy vegetables. The application of Biological Control Agents (BCAs) represents a valuable approach and nowadays some biocontrol products are available on the market for greenhouse and field applications. However, these products often show lack of consistency and variable results mainly due to the poor knowledge about their biology and modes of applications and how the agroecosystem components modulate their efficacy. Streptomycetes are soil inhabitants and have an important ecological role in the turn-over of organic matter; they can also establish beneficial relationships with plant roots enhancing host growth and protection against pathogens through the production of bioactive compounds, lytic enzymes, phytohormones and siderophores. This PhD project aimed to study streptomycetes as BCA and Plant Growth Promoting Bacteria for their use to manage soil borne fungal epidemics in horticulture. A collection of 200 endophytic streptomycete strains isolated from roots was used in this work. To be able to compare the activity of every strain against the pathogens, the dual culture assay was optimized for some representative fungal pathogens based on mycelium radial growth rate in vitro. Subsequently, the optimized method was applied to screen the collection. Some strains showed strong inhibitory activity, but it was specific for one target pathogen and in few cases comprised more than one pathogen. Based on the promising results obtained from the in vitro assays for Sclerotinia sclerotiorum, further studies were focused on the activity of ten strains used for biological control of lettuce drop in different conditions. In particular, it was studied the effect of the application timing of the antagonist and the pathogen, and the amount of the streptomycete used to improve lettuce drop protection. The survival analysis applied to the data of the growth chamber experiments showed that when lettuce was sown one week after the growth substrate inoculation with the pathogen and antagonists, disease control improved, and Streptomyces spp. FT05W, SW06W and SW29W reduced the risk of disease incidence by 42%. On the contrary, no beneficial effect was observed when lettuce was sown the same day of the growth substrate inoculation. Streptomycetes spore concentration significantly influenced lettuce drop protection, but this effect was strain-dependent. Based on these results we planned appropriate field experiment to confirm the results obtained, however, in the field we did not observed significant differences in lettuce protection. Therefore we speculated that moving from controlled to a more complex agroecosystem environment the streptomycete antagonistic activity could fade away probably due to unfavorable interaction in a more complex microflora. Indole-3-acetic acid and the siderophore production were observed for Streptomyces spp. CVM02R and SW29W in in vitro assays, but in field experiments no significant PGP effect on lettuce was obtained at harvest assessing the head weights of plants. The colonization of lettuce rhizosphere and root tissues was investigated using the EGFP labelled strain Streptomyces sp. ZEA17I. This strain showed both rhizospheric and endophytic competences, characters necessary for its successful use for biological control. In addition we showed that applying the strains as spore suspension in the growth substrate resulted in significantly higher roots and rhizosphere colonization than when delivered as seed coating. In conclusion, the results obtained in this study showed that bacteria of the genus Streptomycetes appear valuable candidates for the biological control of soil borne fungal pathogens. However, the complex interactions among the host plant, the antagonist and the pathogen occurring in the agroecosystem are mostly unknown and could generate contradictory results for different environments. Therefore, we think that further studies on simplified models are necessary in order to understand the mechanism on which biological control is based, in order to improve streptomycete activity as BCA for the management of fungal soil borne epidemics

An ultra-low dissipation micro-oscillator for quantum opto-mechanics

Generating non-classical states of light by opto-mechanical coupling depends critically on the mechanical and optical properties of micro-oscillators and on the minimization of thermal noise. We present an oscillating micro-mirror with a mechanical quality factor Q = 2.6x10^6 at cryogenic temperature and a Finesse of 65000, obtained thanks to an innovative approach to the design and the control of mechanical dissipation. Already at 4 K with an input laser power of 2 mW, the radiation-pressure quantum fluctuations become the main noise source, overcoming thermal noise. This feature makes our devices particularly suitable for the production of pondero-motive squeezing.Comment: 21 pages including Supplementary Informatio

An asymptotic plate model for magneto-electro-thermo-elastic sensors and actuators

International audienceWe present an asymptotic two-dimensional plate model for linear magneto-electro-thermo-elastic sensors and actuators, under the hypotheses of anisotropy and homogeneity. Four different boundary conditions pertaining to electromagnetic quantities are considered, leading to four different models: the sensor-actuator model, the actuator-sensor model, the actuator model and the sensor model. We validate the obtained two-dimensional models by proving weak convergence results. Each of the four plate problems turns out to be decoupled into a flexural problem, involving the transversal displacement of the plate, and a certain partially or totally coupled membrane problem