326 research outputs found
CMB Anomalies from Relic Anisotropy
Most of the analysis of the Cosmic Microwave Background relies on the
assumption of statistical isotropy. However, given some recent evidence
pointing against isotropy, as for instance the observed alignment of different
multipoles on large scales, it is worth testing this assumption against the
increasing amount of available data. As a pivot model, we assume that the
spectrum of the primordial perturbations depends also on their directionality
(rather than just on the magnitude of their momentum, as in the standard case).
We explicitly compute the correlation matrix for the temperature anisotropies
in the simpler case in which there is a residual isotropy between two spatial
directions. As a concrete example, we consider a different initial expansion
rate along one direction, and the following isotropization which takes place
during inflation. Depending on the amount of inflation, this can lead to broken
statistical isotropy on the largest observable scales.Comment: 6 pages, 2 .ps figure
Generating non-Gaussian maps with a given power spectrum and bispectrum
We propose two methods for generating non-Gaussian maps with fixed power
spectrum and bispectrum. The first makes use of a recently proposed rigorous,
non-perturbative, Bayesian framework for generating non-Gaussian distributions.
The second uses a simple superposition of Gaussian distributions. The former is
best suited for generating mildly non-Gaussian maps, and we discuss in detail
the limitations of this method. The latter is better suited for the opposite
situation, i.e. generating strongly non-Gaussian maps. The ensembles produced
are isotropic and the power spectrum can be jointly fixed; however we cannot
set to zero all other higher order cumulants (an unavoidable mathematical
obstruction). We briefly quantify the leakage into higher order moments present
in our method. We finally present an implementation of our code within the
HEALPIX packageComment: 22 pages submitted to PRD, astro-ph version only includes low
resolution map
Cosmic microwave background snapshots: pre-WMAP and post-WMAP
Abbreviated: We highlight the remarkable evolution in the CMB power spectrum
over the past few years, and in the cosmological parameters for minimal
inflation models derived from it. Grand unified spectra (GUS) show pre-WMAP
optimal bandpowers are in good agreement with each other and with the one-year
WMAP results, which now dominate the L < 600 bands. GUS are used to determine
calibrations, peak/dip locations and heights, and damping parameters. These CMB
experiments significantly increased the case for accelerated expansion in the
early universe (the inflationary paradigm) and at the current epoch (dark
energy dominance) when they were combined with `prior' probabilities on the
parameters. A minimal inflation parameter set is applied in the same way to the
evolving data. Grid-based and and Monte Carlo Markov Chain methods are shown to
give similar values, highly stable over time and for different prior choices,
with the increasing precision best characterized by decreasing errors on
uncorrelated parameter eigenmodes. After marginalizing over the other cosmic
and experimental variables for a weak+LSS prior, the pre-WMAP data of Jan03 cf.
the post-WMAP data of Mar03 give Omega_{tot} =1.03^{+0.05}_{-0.04} cf.
1.02^{+0.04}_{-0.03}. Adding the flat prior, n_s =0.95^{+0.07}_{-0.04} cf.
0.97^{+0.02}_{-0.02}, with < 2\sigma evidence for a log variation of n_s. The
densities have concordance values. The dark energy pressure-to-density ratio is
not well constrained by our weak+LSS prior, but adding SN1 gives w_Q < -0.7. We
find \sigma_8 = 0.89^{+0.06}_{-0.07} cf. 0.86^{+0.04}_{-0.04}, implying a
sizable SZ effect; the high L power suggest \sigma_8 \sim 0.94^{+0.08}_{-0.16}
is needed to be SZ-compatible.Comment: 36 pages, 5 figures, 5 tables, Jan 2003 Roy Soc Discussion Meeting on
`The search for dark matter and dark energy in the Universe', published PDF
(Oct 15 2003) is http://www.cita.utoronto.ca/~bond/roysoc03/03TA2435.pd
On the evolution of tachyonic perturbations at super-Hubble scales
In the slow-roll inflationary scenario, the amplitude of the curvature
perturbations approaches a constant value soon after the modes leave the Hubble
radius. However, relatively recently, it was shown that the amplitude of the
curvature perturbations induced by the canonical scalar field can grow at
super-Hubble scales if there is either a transition to fast roll inflation or
if inflation is interrupted for some period of time. In this work, we extend
the earlier analysis to the case of a non-canonical scalar field described by
the Dirac-Born-Infeld action. With the help of a specific example, we show that
the amplitude of the tachyonic perturbations can be enhanced or suppressed at
super-Hubble scales if there is a transition from slow roll to fast roll
inflation. We also illustrate as to how the growth of the entropy perturbations
during the fast roll regime proves to be responsible for the change in the
amplitude of the curvature perturbations at super-Hubble scales. Furthermore,
following the earlier analysis for the canonical scalar field, we show that the
power spectrum evaluated in the long wavelength approximation matches the exact
power spectrum obtained numerically very well. Finally, we briefly comment on
an application of this phenomenon.Comment: v1: 15 pages, 4 figures; v2: 16 pages, 5 figures, power spectrum
included, discussion in section 5 enlarged, references added; v3: 17 pages, 5
figures, enhancement AS WELL AS suppression of modes at super-Hubble scales
pointed out, title changed, discussions enlarged, references added, to appear
in JCA
Polarization Diffusion from Spacetime Uncertainty
A model of Lorentz invariant random fluctuations in photon polarization is
presented. The effects are frequency dependent and affect the polarization of
photons as they propagate through space. We test for this effect by confronting
the model with the latest measurements of polarization of Cosmic Microwave
Background (CMB) photons.Comment: 4 pages, 1 figur
Presentazione
Questo volume raccoglie le relazioni, rielaborate dagli autori, svolte al convegno organizzato dal Centro di documentazione europea (CDE) maceratese nell'ambito del Progetto di rete dei CDE italiani per il 2018: \uabPopoli, culture e tradizioni: un patrimonio comune per l'Europa del futuro\ubb, promosso dalla Rappresentanza in Italia della Commissione europea. L'occasione offerta dall'\uabAnno europeo del patrimio culturale\ubb \ue8 parsa particolarmente opportuna per promuovere una riflessione sulla disciplina adottata dall'Unione europea in materia di protezione del patrimonio culturale, vista, necessariamente, sullo sfondo della disciplina contenuta negli strumenti internazionali pertinenti.
Alcuni dei contributi raccolti nel volume sono dedicati pi\uf9 specificamente alla politica dell'Unione europea in materia, della quale ripercorrono l'evoluzione ed esaminano i principali atti normativi adottati al suo interno. Tra questi, particolare attenzione \ue8 dedicata alla direttiva 2014/60 sulla restituzione dei beni culturali illecitamente esportati e al suo recepimento nell'ordinamento italiano. Altri contributi esaminano il pi\uf9 ampio quadro giuridico internazionale pertinente, con particolare riferimento alla Convenzione UNESCO del 1972 sulla tutela del patrimonio mondiale culturale e naturale. Un'attenzione specifica \ue8 rivolta alla tutela del patrimonio culturale subacqueo e del patrimonio culturale immateriale, nonch\ue9 alle problematiche internazionalprivatistiche poste dal commercio di beni culturali
Chaplygin gas with non-adiabatic pressure perturbations
Perturbations in a Chaplygin gas, characterized by an equation of state , may acquire non-adiabatic contributions if spatial variations of the
parameter are admitted. This feature is shown to be related to a specific
internal structure of the Chaplygin gas. We investigate how perturbations of
this type modify the adiabatic sound speed and influence the time dependence of
the gravitational potential which gives rise to the Integrated Sachs-Wolfe
effect in the anisotropy spectrum of the cosmic microwave background.Comment: 16 pages, comments and references added, accepted for publication in
Class.Quantum Gra
Gravity Waves Signatures from Anisotropic pre-Inflation
We show that expanding or contracting Kasner universes are unstable due to
the amplification of gravitational waves (GW). As an application of this
general relativity effect, we consider a pre-inflationary anisotropic geometry
characterized by a Kasner-like expansion, which is driven dynamically towards
inflation by a scalar field. We investigate the evolution of linear metric
fluctuations around this background, and calculate the amplification of the
long-wavelength GW of a certain polarization during the anisotropic expansion
(this effect is absent for another GW polarization, and for scalar
fluctuations). These GW are superimposed to the usual tensor modes of quantum
origin from inflation, and are potentially observable if the total number of
inflationary e-folds exceeds the minimum required to homogenize the observable
universe only by a small margin. Their contribution to the temperature
anisotropy angular power spectrum decreases with the multipole l as l^(-p),
where p depends on the slope of the initial GW power-spectrum. Constraints on
the long-wavelength GW can be translated into limits on the total duration of
inflation and the initial GW amplitude. The instability of classical GW (and
zero-vacuum fluctuations of gravitons) during Kasner-like expansion (or
contraction) may have other interesting applications. In particular, if GW
become non-linear, they can significantly alter the geometry before the onset
of inflation
Instability of the ACW model, and problems with massive vectors during inflation
We prove that the anisotropic inflationary background of the
Ackerman-Carroll-Wise model, characterized by a fixed-norm vector field, is
unstable. We found the instability by explicitly solving the linearized
equations for the most general set of perturbations around this background, and
by noticing that the solutions diverge close to horizon crossing. This happens
because one perturbation becomes a ghost at that moment. A simplified
computation, with only the perturbations of the vector field included, shows
the same instability, clarifying the origin of the problem. We then discuss
several other models, with a particular emphasis on the case of a nonminimal
coupling to the curvature, in which vector fields are used either to support an
anisotropic expansion, or to generate cosmological perturbations on an
isotropic background. In many cases, the mass term of the vector needs to have
the ``wrong'' sign; we show that, as a consequence, the longitudinal vector
mode is a ghost (a field with negative kinetic term, and negative energy; not
simply a tachyon). We comment on problems that arise at the quantum level. In
particular, the presence of a ghost can be a serious difficulty for the UV
completion that such models require in the sub-horizon regime.Comment: 22 pages, 4 figure
Multiplex Matrix Metalloproteinases Analysis in the Cerebrospinal Fluid Reveals Potential Specific Patterns in Multiple Sclerosis Patients.
Background: Matrix metalloproteinases (MMPs) are pleiotropic enzymes involved in extracellular protein degradation and turnover. MMPs are implicated in the pathogenesis of many neurological diseases, including multiple sclerosis (MS). Objective: To search the level of MMPs in the cerebrospinal fluid (CSF) of MS patients and detect possible disease-specific patterns. Methods: CSF samples from 32 MS patients and, from 15 control subjects with other inflammatory neurological diseases (OIND) were analyzed. The Bio-Plex Pro Human MMP 9-Plex Panel (Bio-Rad) was used for the quantification of MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-10, MMP-12, and MMP-13. Results: CSF MMP-1 and MMP-12 levels were significantly reduced in MS as compared with OIND. In MS patients' CSF: (i) MMP-1 levels were significantly higher in women vs. men; (ii) MMP-10 concentrations were higher in patients with CSF-restricted IgG oligoclonal bands, and (iii) MMP-7 levels were increased in patients with longer disease duration. In the OIND group MMP-7 and MMP-12 levels significantly and directly correlated with age. Conclusions: Our study contributes to investigating the role of MMPs in MS, with regard to CSF immunological features and disease duration. Sex-specific differences were also detected in MMPs CSF levels
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