Including birefringence into time evolution of CMB: current and future constraints

We introduce birefringence effects within the propagation history of CMB, considering the two cases of a constant effect and of an effect that increases linearly in time, as the rotation of polarization induced by birefringence accumulates during photon propagation. Both cases result into a mixing of E and B modes before lensing effects take place, thus leading to the fact that lensing is acting on spectra that are already mixed because of birefringence. Moreover, if the polarization rotation angle increases during propagation, birefringence affects more the large scales that the small scales. We put constraints on the two cases using data from WMAP 9yr and BICEP 2013 and compare these results with the constraints obtained when the usual procedure of rotating the final power spectra is adopted, finding that this dataset combination is unable to distinguish between effects, but it nevertheless hints for a non vanishing value of the polarization rotation angle. We also forecast the sensitivity that will be obtained using data from Planck and PolarBear, highlighting how this combination is capable to rule out a vanishing birefringence angle, but still unable to distinguish the different scenarios. Nevertheless, we find that the combination of Planck and PolarBear is sensitive enough to highlight the existence of degeneracies between birefringence rotation and gravitational lensing of CMB photons, possibly leading to false detection of non standard lensing effects if birefringence is neglected.Comment: 20 pages, 10 figures. New version matching the one accepted by JCAP. Corrected typos in equations 2.17-2.1

Constraints on cosmological parameters from future cosmic microwave background experiments

The Planck satellite experiment will soon let cosmologists to determine most of the cosmological parameters with unprecedented accuracy. In particular a strong improvement is expected in many parameters of interest, including neutrino mass, the amount of relativistic particles at recombination, the primordial Helium abundance and the injection of extra ionizing photon by dark matter self-annihilation. Here we review the constraints achievable by future experiments and discuss the implications for fundamental physics. © 2010 IOP Publishing Ltd

Effects of mooring compliancy on the mooring forces, power production, and dynamics of a floating wave activated body energy converter

The paper aims at investigating the interactions between a floating wave energy device (WEC) and its mooring system under a variety of wave conditions (regular and irregular, perpendicular and oblique, ordinary and extreme). The analyzed WEC is the DEXA, a wave activated body point absorber, of the type that performs better when aligned to the incident wave direction. Two typologies of mooring systems were studied: for limited depths, the spread system, with a disposition of the lines that do not constrain the yaw movements; for large depths, the catenary anchor leg mooring (CALM) system. The spread system was experimentally investigated, including a realistic power take-off system, to capture non-linear behaviors and assess device motions, power production, and forces on mooring lines. The CALM system was numerically simulated, as mooring modelling is more reliable in deep waters and allows testing of a number of different configurations, by changing the number of the mooring lines and the mooring layout. The experiments showed that a reduction of the mooring compliancy increases the power production. The numerical simulations showed that a redundancy on the number of chains allows a better distribution of the loads, with advantages on reliability and costs

2D Model of a Floating Body Under Nonlinear Waves

A model describing the dynamics of a floating body by solving the NS-equations in a moving grid framework with free surface is presented. The model has several interesting features, like the peculiar way of describing: a) the grid movements; b) the slip boundary conditions in presence of a wet and dry interface; c) the generation of waves and, to some extents, the sponge layers. The investigated feature is the ratio between the oscillation of the floating body and the wave oscillation, which is usually quite overestimated by viscousless models when the load frequency is close to the floating body eigenfrequency. A simulation of this condition with the non-linear model reproduced much more closely the experimental results described in Ruol and Martinelli (Comsol User Conference, 2007) than the corresponding simulation carried out with a classical model based on linear waves and irrotational flow

UNA METODOLOGIA PER LA VALUTAZIONE DI CRITICITÀ E PRIORITÀ DI INTERVENTO: IL CASO DEL LITORALE VENETO

open3nobilancio sedimentario, litorale Veneto, erosione, allagamento costiero, gestione integrata della zona costiera.openRuol, Piero; Martinelli, Luca; Favaretto, ChiaraRuol, Piero; Martinelli, Luca; Favaretto, Chiar

Sulla disposizione ottimale di frangiflutti galleggianti a catamarano combinati a convertitori di energia ondosa

- La ricerca in cui \ue8 inserito questo lavoro mira allo sviluppo di un dispositivo ibrido costituito da un convertitore di energia ondosa accoppiato ad un frangiflutti galleggiante. - Il frangiflutti, ancorato con pali, \ue8 costituito da elementi prefabbricati collegati rigidamente, in modo da formare una struttura a catamarano. - La configurazione migliore \ue8 la pi\uf9 stretta tra le due esaminate (8 m e 12 m di larghezza), che risulta molto efficiente pur senza essere soggetta a grosse sollecitazioni. - La struttura a catamarano \ue8 da preferire rispetto a quella tradizionale, a parit\ue0 di massa, sia in termini di trasmissione che di riflessione. - Il convertitore esaminato, idoneo ad integrare frangiflutti singoli, non \ue8 adatto ad integrare le strutture a catamarano

Cosmological constraints on the Hu-Sawicki modified gravity scenario

In this paper we place new constraints on a f(R) modified gravity model recently proposed by Hu and Sawicki. After checking that the Hu and Sawicki model produces a viable cosmology, i.e. a matter dominated epoch followed by a late-time acceleration, we constrain some of its parameters by using recent observations from the UNION compilation of luminosity distances of Supernovae type Ia, including complementary information from Baryonic Acoustic Oscillations, Hubble expansion, and age data. We found that the data considered is unable to place significant constraints on the model parameters and we discuss the impact of a different assumption of the background model in cosmic parameters inference

Formula to Predict Transmission for pi-Type Floating Breakwaters

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Modeling of Qiandao Lake submerged floating tunnel subject to multi-support seismic input

Abstract The modeling and seismic analysis of Qiandao lake submerged floating tunnel (SFT) is addressed with particular attention to the mooring system, to dissipation issues and to the spatial variability of the excitation, within a numerical procedure developed by the research group to perform the step-by-step dynamic analysis of discretized non-linear structural systems. The procedure, which can handle arbitrary external loading allowing for multiple-support seismic excitation, is enhanced by enriching the mooring cables model adding non-linear hydrodynamic loads. Different dissipation models account for hydrodynamic damping, structural damping and radiation damping which are included, respectively, as non-linear forces, as linear viscous damping equivalent to linear hysteretic by means of an iterative procedure, and as linear viscous damping. A possible solution is here studied to define an adequate cable discretization in order to correctly model nonlinear geometric effects and to avoid fictitious compressions. A uniformly modulated random process, whose spatial variability is governed by a single coherency function, is deemed adequate to model multi-support seismic input for the given structure. A novel method to obtain response spectrum compatible accelerograms is here proposed