1,721,454 research outputs found
Cosmological constraints on neutrino self-interactions with a light mediator
No full textIf active neutrinos undergo nonstandard ("secret") interactions (NSνIs), the cosmological evolution of the neutrino fluid might be altered, leaving an imprint in cosmological observables. We use the latest publicly available CMB data from Planck to constrain NSνIs inducing ν-ν scattering, under the assumption that the mediator φ of the secret interaction is very light. We find that the effective coupling constant of the interaction, geff4σv©Tν2, is constrained at <2.35×10-27 (95% Credible Interval), which strengthens to geff4<1.64×10-27 when Planck nonbaseline small-scale polarization is considered. Our findings imply that after decoupling at T≃1 MeV, cosmic neutrinos are free-streaming at redshifts z>3800, or z>2300 if small-scale polarization is included. These bounds are only marginally improved when data from geometrical expansion probes are included in the analysis to complement Planck. We also find that the tensions between CMB and low-redshift measurements of the expansion rate H0 and the amplitude of matter fluctuations σ8 are not significantly reduced. Our results are independent of the underlying particle physics model as long as φ is very light. Considering a model with Majorana neutrinos and a pseudoscalar mediator, we find that the coupling constant g of the secret interaction is constrained at 7×10-7. By further assuming that the pseudoscalar interaction comes from a dynamical realization of the seesaw mechanism, as in Majoron models, we can bound the scale of lepton number breaking vσ as (1.4×106)mν
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Lack-of-correlation anomaly in CMB large scale polarisation maps
No full textWe present an assessment of the large-scale CMB anomalies in polarisation using the two-point correlation function as a test case. We employ the state of the art of large scale polarisation datasets: the first based on a 2018 HFI 100 and 143 GHz cross-spectrum analysis, based on processing, and the second from a map-based approach derived through a joint treatment of 2018 LFI and -9yr. We consider the well-known S1/2 estimator, which measures the distance of the two-point correlation function from zero at angular scales larger than 60∘, and rely on realistic simulations for both datasets to assess confidence intervals. By focusing on the pure polarisation field described by either the Q and U Stokes parameters or by the local E-modes, we show that the first description is heavily influenced by the quadrupole (which is poorly constrained in both datasets) while the second one is more suited for an analysis containing higher multipoles up to l∼ 10, limit above which both datasets become markedly noise dominated. We find that both datasets exhibit a lack-of-correlation anomaly in local E-modes, similar to the one observed in temperature, which is better constrained by the less noisy data, where its significance lies at about 99.5%. We perform our analysis using realizations that are either constrained or non-constrained by the observed temperature field, and find similar results in the two cases
Planck constraints on cross-correlations between anisotropic cosmic birefringence and CMB polarization
Full text linkCosmic Birefringence (CB) is the in-vacuo rotation of the linear polarization direction of photons during propagation, caused by parity-violating extensions of Maxwell electromagnetism. We build low resolution CB angle maps using Planck Legacy and NPIPE products and provide for the first time estimates of the cross-correlation spectra CLαE and CLαB between the CB and the CMB polarization fields. We also provide updated CB auto-correlation spectra CLαα as well as the cross-correlation CLαT with the CMB temperature field. We report constraints by defining the scale-invariant amplitudes AαX ≡ L(L + 1)CLαX /2π, where X = α, T, E, B, finding no evidence of CB. In particular, we find AαE = (-7.8 ± 5.6) nK deg and AαB = (0.3 ± 4.0) nK deg at 68% C.L.
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Planck 2018 constraints on anisotropic birefringence and its cross-correlation with CMB anisotropy
No full textParity-violating extensions of standard electromagnetism produce cosmic birefringence, the in vacuo rotation of the linear polarisation direction of a photon during propagation. We employ Planck 2018 CMB polarised data to constrain anisotropic birefringence, modeled by its angular power spectrum Clα α, and the cross-correlation with CMB temperature maps, Clα T, at scales larger than ∼15 degrees. We present joint limits on the scale invariant quantity, Aα α ≡ l (l +1) Clα α / 2 π, and on the analogous amplitude for the cross-correlation, Aα T ≡ l (l +1) Clα T / 2 π. We find no evidence of birefringence within the error budget and obtain Aα α < 0.104 [deg^2] and Aα T=1.50+2.41-4.10 [muKcdotdeg] both at 95 % C.L.. The latter bound appears competitive in constraining a few early dark energy models recently proposed to alleviate the H0 tension. Slicing the joint likelihood at 0Aα T=, the bound on Aα α becomes tighter at Aα α < 0.085 [deg^2] at 95% C.L.. In addition we recast the constraints on Aα α as a bound on the amplitude of primordial magnetic fields responsible for Faraday rotation, finding B1 Mpc < 26.9 nG and B1 Mpc < 24.3 nG at 95% C.L. for the marginalised and sliced case respectively
Polarisation as a tracer of CMB anomalies: PLANCK results and future forecasts
No full textThe lack of power anomaly is an intriguing feature at the largest angular scales of the CMB anisotropy temperature pattern, whose statistical significance is not strong enough to claim any new physics beyond the standard cosmological model. We revisit the former statement by also considering polarisation data. We propose a new one-dimensional estimator which takes jointly into account the information contained in the TT, TE and EE CMB spectra. By employing this estimator on PLANCK 2015 low-l data, we find that a random ΛCDM realisation is statistically accepted at the level of 3.68%. Even though PLANCK polarisation contributes a mere 4% to the total information budget, its use pushes the lower-tail-probability down from the 7.22% obtained with only temperature data. Forecasts of future CMB polarised measurements, as e.g. the LiteBIRD satellite, can increase the polarisation contribution up to 6 times with respect to PLANCK at low-l. We argue that the large-scale E-mode polarisation may play an important role in analysing CMB temperature anomalies with future mission
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Is the lack of power anomaly in the CMB correlated with the orientation of the Galactic plane?
No full textThe lack of power at large angular scales in the CMB temperature anisotropy pattern is a feature known to depend on the size of the Galactic mask. Not only the large scale anisotropy power in the CMB is lower than the best-fit Lambda CDM model predicts, but most of the power seems to be localised close to the Galactic plane, making high-Galactic latitude regions more anomalous. We assess how likely the latter behaviour is in a Lambda CDM model by extracting simulations from the Planck 2018 fiducial model. By comparing the former to Planck data in different Galactic masks, we reproduce the anomaly found in previous works, at a statistical significance of similar to 3 sigma. This result suggests the existence of a bizzarre correlation between the particular orientation of the Galaxy and the lack of power anomaly. To test this hypothesis, we perform random rotations of the Planck 2018 data and compare these to similarly rotated Lambda CDM realisations. We find that, among all possible rotations, the lower-tail probability of the observed high-Galactic latitude data variance is still low at the level of 2.8 sigma. Furthermore, the lowering trend of the variance when moving from low- to high-Galactic latitude is anomalous in the data at similar to 3 sigma when comparing to Lambda CDM rotated realisations. This shows that the lack of power at high Galactic latitude is substantially stable against the "look elsewhere" effect induced by random rotations of the Galaxy orientation. Moreover, this analysis turns out to be substantially stable if we employ, in place of generic Lambda CDM simulations, a specific set whose variance is constrained to reproduce the observed data variance
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