880 research outputs found
Constraining Primordial Magnetic Fields with Future Cosmic Shear Surveys
The origin of astrophysical magnetic fields observed in galaxies and clusters
of galaxies is still unclear. One possibility is that primordial magnetic
fields generated in the early Universe provide seeds that grow through
compression and turbulence during structure formation. A cosmological magnetic
field present prior to recombination would produce substantial matter
clustering at intermediate/small scales, on top of the standard inflationary
power spectrum. In this work we study the effect of this alteration on one
particular cosmological observable, cosmic shear. We adopt the semi-analytic
halo model in order to describe the non-linear clustering of matter, and feed
it with the altered mass variance induced by primordial magnetic fields. We
find that the convergence power spectrum is, as expected, substantially
enhanced at intermediate/small angular scales, with the exact amplitude of the
enhancement depending on the magnitude and power-law index of the magnetic
field power spectrum. We use the predicted statistical errors for a future
wide-field cosmic shear survey, on the model of the ESA Cosmic Vision mission
\emph{Euclid}, in order to forecast constraints on the amplitude of primordial
magnetic fields as a function of the spectral index. We find that the amplitude
will be constrained at the level of nG for , and at the
level of nG for . The latter is at the same level of
lower bounds coming from the secondary emission of gamma-ray sources, implying
that for high spectral indices \emph{Euclid} will certainly be able to detect
primordial magnetic fields, if they exist. The present study shows how
large-scale structure surveys can be used for both understanding the origins of
astrophysical magnetic fields and shedding new light on the physics of the
pre-recombination Universe. (abridged)Comment: 24 pages, 9 figures. To appear on JCA
Imprints of primordial non-Gaussianity on the number counts of cosmic shear peaks
We studied the effect of primordial non-Gaussianity with varied bispectrum
shapes on the number counts of signal-to-noise peaks in wide field cosmic shear
maps. The two cosmological contributions to this particular weak lensing
statistic, namely the chance projection of Large Scale Structure and the
occurrence of real, cluster-sized dark matter halos, have been modeled
semi-analytically, thus allowing to easily introduce the effect of non-Gaussian
initial conditions. We performed a Fisher matrix analysis by taking into
account the full covariance of the peak counts in order to forecast the joint
constraints on the level of primordial non-Gaussianity and the amplitude of the
matter power spectrum that are expected by future wide field imaging surveys.
We find that positive-skewed non-Gaussianity increases the number counts of
cosmic shear peaks, more so at high signal-to-noise values, where the signal is
mostly dominated by massive clusters as expected. The increment is at the level
of ~1 for f_NL=10 and ~10 for f_NL=100 for a local shape of the primordial
bispectrum, while different bispectrum shapes give generically a smaller
effect. For a future survey on the model of the proposed ESA space mission
Euclid and by avoiding the strong assumption of being capable to distinguish
the weak lensing signal of galaxy clusters from chance projection of Large
Scale Structures we forecasted a 1-sigma error on the level of non-Gaussianity
of ~30-40 for the local and equilateral models, and of ~100-200 for the less
explored enfolded and orthogonal bispectrum shapes.Comment: 13 pages, 8 figures, 1 table. Submitted to MNRA
Primordial density perturbations with running spectral index: impact on non-linear cosmic structures
(abridged) We explore the statistical properties of non-linear cosmic
structures in a flat CDM cosmology in which the index of the
primordial power spectrum for scalar perturbations is allowed to depend on the
scale. Within the inflationary paradigm, the running of the scalar spectral
index can be related to the properties of the inflaton potential, and it is
hence of critical importance to test it with all kinds of observations, which
cover the linear and non-linear regime of gravitational instability. We focus
on the amount of running allowed by an updated
combination of CMB anisotropy data and the 2dF Galaxy Redshift Survey. Our
analysis constrains
at 95% Confidence Level when (not) taking into
account primordial gravitational waves in a ratio as predicted by canonical
single field inflation, in agreement with other works. For the cosmological
models best fitting the data both with and without running we studied the
abundance of galaxy clusters and of rare objects, the halo bias, the
concentration of dark matter halos, the Baryon Acoustic Oscillation, the power
spectrum of cosmic shear, and the Integrated Sachs-Wolfe effect. We find that
counting galaxy clusters in future X-ray and Sunyaev-Zel'dovich surveys could
discriminate between the two models, more so if broad redshift information
about the cluster samples will be available. Likewise, measurements of the
power spectrum of cosmological weak lensing as performed by planned all-sky
optical surveys such as EUCLID could detect a running of the primordial
spectral index, provided the uncertainties about the source redshift
distribution and the underlying matter power spectrum are well under control.Comment: 17 pages, 14 figures, 4 tables. Accepted for publication on MNRA
A cross-case analysis of ICT courses in teacher training programmes for special needs: technology affordances and Universal Design for Learning
The special needs teacher is a highly qualified professional whose role is to work in collaboration with all class teachers to activate an inclusive approach for the benefit of all students and to enable individual potentialities. Technology can be of paramount importance in designing learning activities according to the principles of Universal Design for Learning in an interdisciplinary approach and with a holistic perspective of all involved actors in the teaching/learning process. In Italy, the prospective special needs teacher has the opportunity to be fully trained thanks to a comprehensive specialization course where the areas of competence of digital literacy are addressed in a specific course. The study reports a cross analysis of three editions of an Information and Communication Technology course, with a focus on the results of the last edition, whose online format was discussed starting from strengths identified in the first two face-to-face editions of the same course
The effect of primordial non-Gaussianity on the skeleton of cosmic shear maps
(abridged) We explore the imprints of deviations from Gaussian primordial
density fluctuations on the skeleton of the large-scale matter distribution as
mapped through cosmological weak lensing. We computed the skeleton length of
simulated effective convergence maps covering sq. deg each, extracted
from a suite of cosmological body runs with different levels of local
primordial non-Gaussianity. The latter is expected to alter the structure
formation process with respect to the fiducial Gaussian scenario, and thus to
leave a signature on the cosmic web. We found that alterations of the initial
conditions consistently modify both the cumulative and the differential
skeleton length, although the effect is generically smaller than the cosmic
variance and depends on the smoothing of the map prior to the skeleton
computation. Nevertheless, the qualitative shape of these deviations is rather
similar to their primordial counterparts, implying that skeleton statistics
retain good memory of the initial conditions. We performed a statistical
analysis in order to find out at what Confidence Level primordial
non-Gaussianity could be constrained by the skeleton test on cosmic shear maps
of the size we adopted. At 68.3% Confidence Level we found an error on the
measured level of primordial non-Gaussianity of ,
while at 90% Confidence Level it is of . While
these values by themselves are not competitive with the current constraints,
weak lensing maps larger than those used here would have a smaller
field-to-field variance, and thus would likely lead to tighter constraints. A
rough estimate indicates a few tens at 68.3%
Confidence Level for an all-sky weak lensing survey.Comment: 11 pages, 9 figures. Accepted for publication on MNRA
Particle acceleration and radiation friction effects in the filamentation instability of pair plasmas
The evolution of the filamentation instability produced by two
counter-streaming pair plasmas is studied with particle-in-cell (PIC)
simulations in both one (1D) and two (2D) spatial dimensions. Radiation
friction effects on particles are taken into account. After an exponential
growth of both the magnetic field and the current density, a nonlinear
quasi-stationary phase sets up characterized by filaments of opposite currents.
During the nonlinear stage, a strong broadening of the particle energy spectrum
occurs accompanied by the formation of a peak at twice their initial energy. A
simple theory of the peak formation is presented. The presence of radiative
losses does not change the dynamics of the instability but affects the
structure of the particle spectra.Comment: 8 pages, 8 figures, submitted to MNRA
An Autoethnographic Approach to Faculty Development Through a Longitudinal Analysis of a Co-taught Workshop
The present contribution explores howa co-taughtworkshop, designed
and delivered in the last two academic years within two curricular disciplines of the third year of the degree course in Science of Education at University of Macerata (Italy), took advantage of autoethnography as a reflective method to enrich the interdisciplinary relationship between the two professors involved and their mutual growth in terms of instructional design and teaching practices. The exploration of Self as a data source allowed both researchers (in their teaching role) to reflect on core areas of faculty development in connection with the specific co-teaching style they adopted. Autoethnography allowed all the involved actors (students and professors) to visualize a transformative direction in their academic identity and professional growth. The discussion of the results is based on a content
analysis of different data sources where all the data were triangulated in a double connotation, that is, between professors and among the different sources in an iterative process
Charged di-boson production at the LHC in a 4-site model with a composite Higgs boson
We investigate the scope of the LHC in probing the parameter space of a
4-site model supplemented by one composite Higgs state, assuming all past,
current and future energy and luminosity stages of the CERN machine. We
concentrate on the yield of charged di-boson production giving two
opposite-charge different-flavour leptons and missing (transverse) energy,
i.e., events induced via the subprocess
+ , which enables the production in the intermediate step of all
additional neutral and charged gauge bosons belonging to the spectrum of this
model, some of which in resonant topologies. We find this channel accessible
over the background at all LHC configurations after a dedicated cut-based
analysis. We finally compare the yield of the di-boson mode to that of
Drell-Yan processes and establish that they have complementary strengths, one
covering regions of parameter space precluded to the others and vice versa.Comment: 36 pages, 13 figures, 13 table
Electron heating in subpicosecond laser interaction with overdense and near-critical plasmas
n this work we investigate electron heating induced by intense laser interaction with micrometric flat solid
foils in the context of laser-driven ion acceleration. We propose a simple law to predict the electron temperature in
a wider range of laser parameters with respect to commonly used existing models. An extensive two-dimensional
(2D) and 3D numerical campaign shows that electron heating is due to the combined actions of j×B
and Brunel effect. Electron temperature can be well described with a simple function of pulse intensity and angle of incidence,
with parameters dependent on pulse polarization. We then combine our model for the electron temperature with
an existing model for laser-ion acceleration, using recent experimental results as a benchmark. We also discuss
an exploratory attempt to model electron temperature for multilayered foam-attached targets, which have been
proven recently to be an attractive target concept for laser-driven ion acceleration
How does a data strategy enable customer value? The case of FinTechs and traditional banks under the open finance framework
The coupling of data and digital innovation opens the way for new business in the financial services sector, where customers are placed at the centre of decisions and data can help to develop customer knowledge. To carry out our research, we adopted a multi-case study approach to explore how a data strategy is developed in the retail banking industry, together with its relationship with customer value, paying particular attention to the heterogeneity between traditional banks and financial technology companies (FinTechs). Two main points emerged from the study. Firstly, there are three possible approaches to Open Finance, which are mainly defined by their different corporate cultures, organisational configurations, technological architecture and data value. Secondly, it is not enough to be a FinTech to be best placed to exploit the market, as some traditional banks share the FinTechs' approach to Open Finance. Designing new tailored products, customising their prices and offering them over the right channels through targeted communication are all data-driven initiatives that stem from cross- or up-selling potential, core to the retail banking industry for turning a customer into a cash flow, thus enabling value to be created for customers. Our findings additionally revealed that there is a form of external information asymmetry between the customer and the bank, and that there is also an internal asymmetry between bank departments, as their visibility on information about the same customer may differ
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