scholarly journals Cosmic Dark Radiation and Neutrinos

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Maria Archidiacono ◽  
Elena Giusarma ◽  
Steen Hannestad ◽  
Olga Mena
Keyword(s):  
Degrees Of Freedom ◽  
Hubble Constant ◽  
Point Of View ◽  
Data Sets ◽  
Beyond The Standard Model ◽  
Microwave Background ◽  
Dark Radiation ◽  
Cosmological Observations ◽  
Local Measurements ◽  
The Moment

New measurements of the cosmic microwave background (CMB) by the Planck mission have greatly increased our knowledge about the universe. Dark radiation, a weakly interacting component of radiation, is one of the important ingredients in our cosmological model which is testable by Planck and other observational probes. At the moment, the possible existence of dark radiation is an unsolved question. For instance, the discrepancy between the value of the Hubble constant,H0, inferred from the Planck data and local measurements ofH0can to some extent be alleviated by enlarging the minimalΛCDM model to include additional relativistic degrees of freedom. From a fundamental physics point of view, dark radiation is no less interesting. Indeed, it could well be one of the most accessible windows to physics beyond the standard model, for example, sterile neutrinos. Here, we review the most recent cosmological results including a complete investigation of the dark radiation sector in order to provide an overview of models that are still compatible with new cosmological observations. Furthermore, we update the cosmological constraints on neutrino physics and dark radiation properties focusing on tensions between data sets and degeneracies among parameters that can degrade our information or mimic the existence of extra species.

A determination of the Ω0mh2 cosmological parameter without tension

2021 ◽  
pp. 2150157
Author(s):  
E. Benedetto ◽  
A. Feoli ◽  
A. L. Iannella
Keyword(s):  
Experimental Data ◽  
Scientific Community ◽  
Hubble Constant ◽  
Point Of View ◽  
Cosmological Parameter ◽  
Theoretical Point ◽  
Microwave Background ◽  
Local Measurements ◽  
The Universe

Measurements for the expansion rate of the universe disagree. Indeed, local measurements suggest a higher value of the Hubble constant than those performed through the cosmic microwave background. This fact led to a very interesting debate within the scientific community. The paper is not devoted to give solutions to the problem of “Hubble tension”. The aim of this paper is, on the contrary, to deduce the [Formula: see text] cosmological parameter from a theoretical point of view, using only two experimental data: the temperature of CMB today and the temperature of photons near the decoupling time.

scholarly journals Distant foreground and the Planck-derived Hubble constant

2020 ◽  
Vol 492 (4) ◽  
pp. 5052-5056 ◽  
Author(s):  
V N Yershov ◽  
A A Raikov ◽  
N Yu Lovyagin ◽  
N P M Kuin ◽  
E A Popova
Keyword(s):  
Hubble Constant ◽  
Temperature Fluctuations ◽  
Coarse Grain ◽  
Model Parameters ◽  
Local Measurement ◽  
Microwave Background ◽  
Random Samples ◽  
Local Measurements ◽  
Grain Dust ◽  
Cmb Temperature

ABSTRACT It is possible to reduce the discrepancy between the local measurement of the cosmological parameter H0 and the value derived from the Planck measurements of the cosmic microwave background (CMB) by considering contamination of the CMB by emission from some medium around distant extragalactic sources, such as extremely cold coarse-grain dust. Though being distant, such a medium would still be in the foreground with respect to the CMB, and, as any other foreground, it would alter the CMB power spectrum. This could contribute to the dispersion of CMB temperature fluctuations. By generating a few random samples of CMB with different dispersions, we have checked that the increased dispersion leads to a smaller estimated value of H0, the rest of the cosmological model parameters remaining fixed. This might explain the reduced value of the Planck-derived parameter H0 with respect to the local measurements. The signature of the distant foreground in the CMB traced by supernovae (SNe) was previously reported by the authors of this paper – we found a correlation between the SN redshifts, zSN, and CMB temperature fluctuations at the SNe locations, TSN. Here we have used the slopes of the regression lines $T_{\rm SN}\, /\, z_{\rm SN}$ corresponding to different Planck wavebands in order to estimate the possible temperature of the distant extragalactic medium, which turns out to be very low, about 5 K. The most likely ingredient of this medium is coarse-grain (grey) dust, which is known to be almost undetectable, except for the effect of dimming remote extragalactic sources.

scholarly journals Measuring Gravity at Cosmological Scales

Universe ◽  
2020 ◽  
Vol 6 (2) ◽  
pp. 20 ◽  
Author(s):  
Luca Amendola ◽  
Dario Bettoni ◽  
Ana Marta Pinho ◽  
Santiago Casas
Keyword(s):  
Degrees Of Freedom ◽  
Large Scale ◽  
Early Years ◽  
Microwave Background ◽  
Four Dimensions ◽  
Tensor Theory ◽  
Cosmological Observations ◽  
Local Gravity ◽  
Model Independent ◽  
Models Of Gravity

This review is a pedagogical introduction to models of gravity and how they are constrained through cosmological observations. We focus on the Horndeski scalar-tensor theory and on the quantities that can be measured with a minimum of assumptions. Alternatives or extensions of general relativity have been proposed ever since its early years. Because of the Lovelock theorem, modifying gravity in four dimensions typically means adding new degrees of freedom. The simplest way is to include a scalar field coupled to the curvature tensor terms. The most general way of doing so without incurring in the Ostrogradski instability is the Horndeski Lagrangian and its extensions. Testing gravity means therefore, in its simplest term, testing the Horndeski Lagrangian. Since local gravity experiments can always be evaded by assuming some screening mechanism or that baryons are decoupled, or even that the effects of modified gravity are visible only at early times, we need to test gravity with cosmological observations in the late universe (large-scale structure) and in the early universe (cosmic microwave background). In this work, we review the basic tools to test gravity at cosmological scales, focusing on model-independent measurements.

scholarly journals Features and new physical scales in primordial observables: Theory and observation

2015 ◽  
Vol 24 (10) ◽  
pp. 1530023 ◽  
Author(s):  
Jens Chluba ◽  
Jan Hamann ◽  
Subodh P. Patil
Keyword(s):  
Correlation Functions ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Initial Conditions ◽  
Linear Response Theory ◽  
Microwave Background ◽  
Scale Invariant ◽  
Cosmological Observations ◽  
Background Models ◽  
Characteristic Scales

All cosmological observations to date are consistent with adiabatic, Gaussian and nearly scale invariant initial conditions. These findings provide strong evidence for a particular symmetry breaking pattern in the very early universe (with a close to vanishing order parameter, ϵ), widely accepted as conforming to the predictions of the simplest realizations of the inflationary paradigm. However, given that our observations are only privy to perturbations, in inferring something about the background that gave rise to them, it should be clear that many different underlying constructions project onto the same set of cosmological observables. Features in the primordial correlation functions, if present, would offer a unique and discriminating window onto the parent theory in which the mechanism that generated the initial conditions is embedded. In certain contexts, simple linear response theory allows us to infer new characteristic scales from the presence of features that can break the aforementioned degeneracies among different background models, and in some cases can even offer a limited spectroscopy of the heavier degrees of freedom that couple to the inflaton. In this review, we offer a pedagogical survey of the diverse, theoretically well-grounded mechanisms which can imprint features into primordial correlation functions in addition to reviewing the techniques one can employ to probe observations. These observations include cosmic microwave background (CMB) anisotropies and spectral distortions as well as the matter two and three point functions as inferred from large-scale structure (LSS) and potentially, 21 cm surveys.

scholarly journals Dark Energy with Phantom Crossing and the H0 Tension

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 404
Author(s):  
Eleonora Di Valentino ◽  
Ankan Mukherjee ◽  
Anjan A. Sen
Keyword(s):  
Dark Energy ◽  
Confidence Level ◽  
Hubble Constant ◽  
Acoustic Oscillation ◽  
Energy Sector ◽  
Local Measurement ◽  
Microwave Background ◽  
Perfect Agreement ◽  
Cosmological Observations ◽  
Phantom Crossing

We investigate the possibility of phantom crossing in the dark energy sector and the solution for the Hubble tension between early and late universe observations. We use robust combinations of different cosmological observations, namely the Cosmic Microwave Background (CMB), local measurement of Hubble constant (H0), Baryon Acoustic Oscillation (BAO) and SnIa for this purpose. For a combination of CMB+BAO data that is related to early universe physics, phantom crossing in the dark energy sector was confirmed at a 95% confidence level and we obtained the constraint H0=71.0−3.8+2.9 km/s/Mpc at a 68% confidence level, which is in perfect agreement with the local measurement by Riess et al. We show that constraints from different combinations of data are consistent with each other and all of them are consistent with phantom crossing in the dark energy sector. For the combination of all data considered, we obtained the constraint H0=70.25±0.78 km/s/Mpc at a 68% confidence level and the phantom crossing happening at the scale factor am=0.851−0.031+0.048 at a 68% confidence level.

scholarly journals Phantom Braneworld and the Hubble Tension

2021 ◽  
Vol 923 (2) ◽  
pp. 212
Author(s):  
Satadru Bag ◽  
Varun Sahni ◽  
Arman Shafieloo ◽  
Yuri Shtanov
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Cosmic Microwave Background ◽  
Data Sets ◽  
Microwave Background ◽  
Effective Equation ◽  
Induced Gravity ◽  
Cosmic Evolution ◽  
Local Measurements ◽  
Braneworld Model

Abstract Braneworld models with induced gravity exhibit phantom-like behavior of the effective equation of state of dark energy. They can, therefore, naturally accommodate higher values of H 0, preferred by recent local measurements while satisfying the cosmic microwave background constraints. We test the background evolution in such phantom braneworld scenarios with the current observational data sets. We find that the phantom braneworld prefers a higher value of H 0 even without the R19 prior, thereby providing a much better fit to the local measurements. Although this braneworld model cannot fully satisfy all combinations of cosmological observables, among existing dark energy candidates the phantom brane provides one of the most compelling explanations of cosmic evolution.

scholarly journals Determining the Hubble constant without the sound horizon scale: measurements from CMB lensing

2020 ◽  
Vol 501 (2) ◽  
pp. 1823-1835
Author(s):  
Eric J Baxter ◽  
Blake D Sherwin
Keyword(s):  
Power Spectrum ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Hubble Constant ◽  
New Physics ◽  
Data Sets ◽  
Density Parameter ◽  
Acoustic Oscillations ◽  
The Galaxy ◽  
Local Measurements

ABSTRACT Measurements of the Hubble constant, H0, from the cosmic distance ladder are currently in tension with the value inferred from Planck observations of the cosmic microwave background (CMB) and other high-redshift data sets if a flat Λ cold dark matter (ΛCDM) cosmological model is assumed. One of the few promising theoretical resolutions of this tension is to invoke new physics that changes the sound horizon scale in the early Universe; this can bring CMB and baryon acoustic oscillations (BAO) constraints on H0 into better agreement with local measurements. In this paper, we discuss how a measurement of the Hubble constant can be made from the CMB without using information from the sound horizon scale, rs. In particular, we show how measurements of the CMB lensing power spectrum can place interesting constraints on H0 when combined with measurements of either supernovae or galaxy weak lensing, which constrain the matter density parameter. The constraints arise from the sensitivity of the CMB lensing power spectrum to the horizon scale at matter–radiation equality (in projection); this scale could have a different dependence on new physics than the sound horizon. From an analysis of current CMB lensing data from Planck and Pantheon supernovae with conservative external priors, we derive an rs-independent constraint of $H_0 = 73.5\pm 5.3\, {\rm km}\,{\rm s}^{-1}\,{\rm Mpc}^{-1}$. Forecasts for future CMB surveys indicate that improving constraints beyond an error of $\sigma (H_0) = 3\, {\rm km}\,{\rm s}^{-1}\,{\rm Mpc}^{-1}$ will be difficult with CMB lensing, although applying similar methods to the galaxy power spectrum may allow for further improvements.

Confidentiality of Statistical Records: A Threat-Monitoring Scheme for On Line Dialogue

1976 ◽  
Vol 15 (01) ◽  
pp. 36-42 ◽  
Author(s):  
J. Schlörer
Keyword(s):  
Statistical Data ◽  
Cost Benefit ◽  
Data Bank ◽  
High Ratio ◽  
Point Of View ◽  
Data Sets ◽  
Monitoring Scheme ◽  
Access Controls ◽  
On Line ◽  
Bona Fide

From a statistical data bank containing only anonymous records, the records sometimes may be identified and then retrieved, as personal records, by on line dialogue. The risk mainly applies to statistical data sets representing populations, or samples with a high ratio n/N. On the other hand, access controls are unsatisfactory as a general means of protection for statistical data banks, which should be open to large user communities. A threat monitoring scheme is proposed, which will largely block the techniques for retrieval of complete records. If combined with additional measures (e.g., slight modifications of output), it may be expected to render, from a cost-benefit point of view, intrusion attempts by dialogue valueless, if not absolutely impossible. The bona fide user has to pay by some loss of information, but considerable flexibility in evaluation is retained. The proposal of controlled classification included in the scheme may also be useful for off line dialogue systems.

Chelovek.RU/Человек.RU

Chelovek RU ◽  
2020 ◽  
pp. 18-53
Author(s):  
Sergei Avanesov ◽  
Keyword(s):  
Family History ◽  
Great Distance ◽  
Point Of View ◽  
The Past ◽  
Russian Philosopher ◽  
True Meaning ◽  
The Future ◽  
Pavel Florensky ◽  
The Moment

Abstract. The article analyzes the autobiography of the famous Russian philosopher, theologian and scientist Pavel Florensky, as well as those of his texts that retain traces of memories. According to Florensky, the personal biography is based on family history and continues in children. He addresses his own biography to his children. Memories based on diary entries are designed as a memory diary, that is, as material for future memories. The past becomes actual in autobiography, turns into a kind of present. The past, from the point of view of its realization in the present, gains meaning and significance. The au-thor is active in relation to his own past, transforming it from a collection of disparate facts into a se-quence of events. A person can only see the true meaning of such events from a great distance. Therefore, the philosopher remembers not so much the circumstances of his life as the inner impressions of the en-counter with reality. The most powerful personality-forming experiences are associated with childhood. Even the moment of birth can decisively affect the character of a person and the range of his interests. The foundations of a person's worldview are laid precisely in childhood. Florensky not only writes mem-oirs about himself, but also tries to analyze the problems of time and memory. A person is immersed in time, but he is able to move into the past through memory and into the future through faith. An autobi-ography can never be written to the end because its author lives on. However, reaching the depths of life, he is able to build his path in such a way that at the end of this path he will unite with the fullness of time, with eternity.

The Revolutionizing of the Revolution

2017 ◽  
Author(s):  
R. R. Palmer
Keyword(s):  
French Revolution ◽  
Point Of View ◽  
Strict Sense ◽  
French Government ◽  
Thing In Itself ◽  
Set Up ◽  
The Moment ◽  
The French Revolution ◽  
The Revolution

In 1792, the French Revolution became a thing in itself, an uncontrollable force that might eventually spend itself but which no one could direct or guide. The governments set up in Paris in the following years all faced the problem of holding together against forces more revolutionary than themselves. This chapter distinguishes two such forces for analytical purposes. There was a popular upheaval, an upsurge from below, sans-culottisme, which occurred only in France. Second, there was the “international” revolutionary agitation, which was not international in any strict sense, but only concurrent within the boundaries of various states as then organized. From the French point of view these were the “foreign” revolutionaries or sympathizers. The most radical of the “foreign” revolutionaries were seldom more than advanced political democrats. Repeatedly, however, from 1792 to 1799, these two forces tended to converge into one force in opposition to the French government of the moment.

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