Future constraints on variations of the fine structure constant from combined CMB and weak lensing measurements

We forecast the ability of future CMB and galaxy lensing surveys to constrain variations of the fine structure constant. We found that lensing data, as those expected from satellite experiments as Euclid could improve the constraint from future CMB experiments leading to a \Delta \alpha / \alpha = 8*10^{-4} accuracy. A variation of the fine structure constant \alpha is strongly degenerate with the Hubble constant H_0 and with inflationary parameters as the scalar spectral index n_s. These degeneracies may cause significant biases in the determination of cosmological parameters if a variation in \alpha as large as \sim 0.5 % is present at the epoch of recombination.Comment: 6 pages, 6 figures, improved text and few typos correcte

Handlungen und T\ue4tigkeiten in Hegels Philosophie des objektiven und des absoluten Geistes

Uno degli aspetti che evidenzia la distanza tra la filosofia dello spirito oggettivo e la filosofia dello spirito assoluto riguarda le azioni tematizzate nella prima e le produzioni in cui si articola la seconda. Nel contesto dello spirito oggettivo Hegel discute i problemi connessi all\u2019azione intenzionale e alle sue implicazioni giuridiche e morali, insieme al riconoscimento del valore sociale o politico di quelle azioni, che acquistano un peso oggettivo in relazione a ruoli, relazioni, istituzioni. Il saggio esamina le differenze esistenti tra le attivit\ue0 dello spirito assoluto e le azioni descritte nello spirito oggettivo a partire dalla conclusione dell\u2019Enciclopedia, in cui l\u2019idea di filosofia \ue8 definita come T\ue4tigkeit, die \u201csich ewig als absoluter Geist bet\ue4tigt, erzeugt und genie ft\u201d (Enz. \ua7 577)

Rock fractures analysis using Structure from Motion technology: new insight from Digital Outcrop Models

Fractures are one of the most important features of the rocks of the upper crust since they strongly influence their physical and chemical behavior and reflect their tectonic history. For this reason, fracture study plays a key role in different branches of the geosciences. Notwithstanding, the quantification of the features and parameters describing fractures could be unsatisfactory using the standard field techniques because they are mainly based on direct-contact methodologies that are affected by errors, as orientation bias and trace censoring, and scarce representativeness, due to the limited possibility of acquiring information of outcrops partially or totally inaccessible. Recently new remote sensing technologies, such as Terrestrial Laser Scanner (TLS) and Digital Photogrammetry (DP), can help to overcome these limitations. Whereas TLS could be very expensive and difficult to use in geological study, DP permits to obtain similar results in an easier way due to cheaper and lighter equipment and more straightforward procedures. Moreover, DP becomes even more useful when combined with Unmanned Aerial Vehicle (UAV) because permits to acquire digital images from positions inaccessible to humans, allowing to analyze geological objects from points of view previously unimaginable. The images acquired from the ground and/or by the UAV can be then processed using different digital algorithms, such as Structure from Motion (SfM), that permit to create 3D model of the studied outcrop. In geosciences, the 3D model representing the surface of the outcrop is often called Digital Outcrop Model (DOM). Despite DOMs can be really useful in different branches of geosciences, their applications are quite well limited because the procedures of their development and sampling/analysis are scarcely analyzed in literature. It is important to highlight that whereas the UAV-based SfM approach is fairly discussed in literature for simple flat areas, is scarcely treated for application to near vertical and not-planar slopes. Moreover, the validity of some procedures of fracture sampling on 3D model, with special regards to the automatic ones, that have been recently presented in literature, is not well treated for real cases of study. The scarce knowledge about these approaches could cause different troubles to the scientific-users: from the application of avoidable time-consuming routine, to the acquisition and interpretation of erroneous data. This research aims to contribute to the scientific knowledge of the use of digital photogrammetry for fractured rock mass analysis, creating and defining new approaches and procedures for the development, analysis and application of DOMs. Here, a workflow for the fracture analysis of steep rocky outcrops and slopes using the 3D DOM is presented. In particular, the following steps are discussed: (i) image acquisition; (ii) development of 3D model; (iii) sampling of DOM; (iv) quantification and parametrization of the 3D measures; (v) application of the 3D quantitative data and parameters to different case of study. Four different cases of study were selected to validate the proposed method: the upper Staffora Valley and Ponte Organasco (Northern Apennines, Italy), Ormea (Ligurian Alps, Italy), and Gallivaggio (Western Alps, Italy) cases of study. However, this methodology could not completely replace the 'direct-contact' field activity, because some information as roughness, infilling and aperture of fractures cannot be measured satisfactory, and because, where possible, field control measures to validate the 3D data are necessary. However, this methodology could be considered as a new necessary procedure for rock-fracture studies because it allows to overcome the inevitable errors of the ground-based traditional methodology and because the DOMs are always available for the analysis, promoting data sharing and comparison, two fundamental principles on which science have and will have to be basedFractures are one of the most important features of the rocks of the upper crust since they strongly influence their physical and chemical behavior and reflect their tectonic history. For this reason, fracture study plays a key role in different branches of the geosciences. Notwithstanding, the quantification of the features and parameters describing fractures could be unsatisfactory using the standard field techniques because they are mainly based on direct-contact methodologies that are affected by errors, as orientation bias and trace censoring, and scarce representativeness, due to the limited possibility of acquiring information of outcrops partially or totally inaccessible. Recently new remote sensing technologies, such as Terrestrial Laser Scanner (TLS) and Digital Photogrammetry (DP), can help to overcome these limitations. Whereas TLS could be very expensive and difficult to use in geological study, DP permits to obtain similar results in an easier way due to cheaper and lighter equipment and more straightforward procedures. Moreover, DP becomes even more useful when combined with Unmanned Aerial Vehicle (UAV) because permits to acquire digital images from positions inaccessible to humans, allowing to analyze geological objects from points of view previously unimaginable. The images acquired from the ground and/or by the UAV can be then processed using different digital algorithms, such as Structure from Motion (SfM), that permit to create 3D model of the studied outcrop. In geosciences, the 3D model representing the surface of the outcrop is often called Digital Outcrop Model (DOM). Despite DOMs can be really useful in different branches of geosciences, their applications are quite well limited because the procedures of their development and sampling/analysis are scarcely analyzed in literature. It is important to highlight that whereas the UAV-based SfM approach is fairly discussed in literature for simple flat areas, is scarcely treated for application to near vertical and not-planar slopes. Moreover, the validity of some procedures of fracture sampling on 3D model, with special regards to the automatic ones, that have been recently presented in literature, is not well treated for real cases of study. The scarce knowledge about these approaches could cause different troubles to the scientific-users: from the application of avoidable time-consuming routine, to the acquisition and interpretation of erroneous data. This research aims to contribute to the scientific knowledge of the use of digital photogrammetry for fractured rock mass analysis, creating and defining new approaches and procedures for the development, analysis and application of DOMs. Here, a workflow for the fracture analysis of steep rocky outcrops and slopes using the 3D DOM is presented. In particular, the following steps are discussed: (i) image acquisition; (ii) development of 3D model; (iii) sampling of DOM; (iv) quantification and parametrization of the 3D measures; (v) application of the 3D quantitative data and parameters to different case of study. Four different cases of study were selected to validate the proposed method: the upper Staffora Valley and Ponte Organasco (Northern Apennines, Italy), Ormea (Ligurian Alps, Italy), and Gallivaggio (Western Alps, Italy) cases of study. However, this methodology could not completely replace the 'direct-contact' field activity, because some information as roughness, infilling and aperture of fractures cannot be measured satisfactory, and because, where possible, field control measures to validate the 3D data are necessary. However, this methodology could be considered as a new necessary procedure for rock-fracture studies because it allows to overcome the inevitable errors of the ground-based traditional methodology and because the DOMs are always available for the analysis, promoting data sharing and comparison, two fundamental principles on which science have and will have to be base

Constraints on a scale-dependent bias from galaxy clustering

We forecast the future constraints on scale-dependent parametrizations of galaxy bias and their impact on the estimate of cosmological parameters from the power spectrum of galaxies measured in a spectroscopic redshift survey. For the latter we assume a wide survey at relatively large redshifts, similar to the planned Euclid survey, as baseline for future experiments. To assess the impact of the bias we perform a Fisher matrix analysis and we adopt two different parametrizations of scale-dependent bias. The fiducial models for galaxy bias are calibrated using a mock catalogs of H$\alpha$ emitting galaxies mimicking the expected properties of the objects that will be targeted by the Euclid survey. In our analysis we have obtained two main results. First of all, allowing for a scale-dependent bias does not significantly increase the errors on the other cosmological parameters apart from the rms amplitude of density fluctuations, $\sigma_{8}$, and the growth index $\gamma$, whose uncertainties increase by a factor up to two, depending on the bias model adopted. Second, we find that the accuracy in the linear bias parameter $b_{0}$ can be estimated to within 1-2\% at various redshifts regardless of the fiducial model. The non-linear bias parameters have significantly large errors that depend on the model adopted. Despite of this, in the more realistic scenarios departures from the simple linear bias prescription can be detected with a $\sim2\,\sigma$ significance at each redshift explored. Finally, we use the Fisher Matrix formalism to assess the impact of assuming an incorrect bias model and found that the systematic errors induced on the cosmological parameters are similar or even larger than the statistical ones.Comment: new section added; conclusions unchanged; accepted for publication in PR

Paesaggi marginali e paesaggi mediati

L’evoluzione socio-economica ha radicalmente cambiato i paesaggi dell’europa, che erano stati plasmati dalle comunità rurali. Il recupero, con una valorizzazione economica e simbolica, è possibile solo con una nuova consapevolezza e responsabilità dell’intera società

New Constraints on variations of the fine structure constant from CMB anisotropies

We demonstrate that recent measurements of Cosmic Microwave Background temperature and polarization anisotropy made by the ACBAR, QUAD and BICEP experiments substantially improve the cosmological constraints on possible variations of the fine structure constant in the early universe. This data, combined with the five year observations from the WMAP mission yield the constraint alpha/alpha_0 = 0.987 \pm 0.012 at 68% c.l.. The inclusion of the new HST constraints on the Hubble constant further increases the accuracy to alpha/alpha_0 = 1.001 \pm 0.007 at 68% c.l., bringing possible deviations from the current value below the 1% level and improving previous constraints by a factor 3.Comment: 3 pages, 2 figure

Constraining Variations in the Fine Structure Constant in the presence of Early Dark Energy

We discuss present and future cosmological constraints on variations of the fine structure constant $\alpha$ induced by an early dark energy component having the simplest allowed (linear) coupling to electromagnetism. We find that current cosmological data show no variation of the fine structure constant at recombination respect to the present-day value, with $\alpha$ / $\alpha_0$ = 0.975 \pm 0.020 at 95 % c.l., constraining the energy density in early dark energy to $\Omega_e$ < 0.060 at 95 % c.l.. Moreover, we consider constraints on the parameter quantifying the strength of the coupling by the scalar field. We find that current cosmological constraints on the coupling are about 20 times weaker than those obtainable locally (which come from Equivalence Principle tests). However forthcoming or future missions, such as Planck Surveyor and CMBPol, can match and possibly even surpass the sensitivity of current local tests.Comment: 5 pages, 3 figure

The Fine Structure Constant and the CMB Damping Scale

The recent measurements of the Cosmic Microwave Background anisotropies at arcminute angular scales performed by the ACT and SPT experiments are probing the damping regime of CMB fluctuations. The analysis of these datasets unexpectedly suggests that the effective number of relativistic degrees of freedom is larger than the standard value of Neff = 3.04, and inconsistent with it at more than two standard deviations. In this paper we study the role of a mechanism that could affect the shape of the CMB angular fluctuations at those scales, namely a change in the recombination process through variations in the fine structure constant. We show that the new CMB data significantly improve the previous constraints on variations of {\alpha}, with {\alpha}/{\alpha}0 = 0.984 \pm 0.005, i.e. hinting also to a more than two standard deviation from the current, local, value {\alpha}0. A significant degeneracy is present between {\alpha} and Neff, and when variations in the latter are allowed the constraints on {\alpha} are relaxed and again consistent with the standard value. Deviations of either parameter from their standard values would imply the presence of new, currently unknown physics.Comment: 4 pages, 1 figur