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Context. Forthcoming experiments will enable us to determine tomographic shear spectra at a high precision level. Most predictions about them have until now been based on algorithms yielding the expected linear and non-linear spectrum of density fluctuations. Even when simulations have been used, so-called Halofit predictions on fairly large scales have been needed. Aims. We wish to go beyond this limitation. Methods. We perform N-body and hydrodynamical simulations within a sufficiently large cosmological volume to allow a direct connection between simulations and linear spectra. While covering large length-scales, the simulation resolution is good enough to allow us to explore the high-ℓ harmonics of the cosmic shear (up to ℓ ∼ 50 000), well into the domain where baryon physics becomes important. We then compare shear spectra in the absence and in presence of various kinds of baryon physics, such as radiative cooling, star formation, and supernova feedback in the form of galactic winds. Results. We distinguish several typical properties of matter fluctuation spectra in the different simulations and test their impact on shear spectra. Conclusions. We compare our outputs with those obtainable using approximate expressions for non-linear spectra, and identify substantial discrepancies even between our results and those of purely N-body results. Our simulations and the treatment of their outputs however enable us, for the first time, to obtain shear results that are fully independent of any approximate expression, also in the high-ℓ range, where we need to incorporate a non-linear power spectrum of density perturbations and the effects of baryon physics. This will allow us to fully exploit the cosmological information contained in future high-sensitivity cosmic shear surveys, exploring the physics of cosmic shears via weak lensing measurements. [ABSTRACT FROM AUTHOR]

The next generation mass probes will obtain information on non-linear power spectra and their evolution, allowing us to investigate the nature of Dark Energy. To exploit such data we need high-precision simulations, extending at least up to scales of , where the effects of baryons can no longer be neglected. In this paper, we present a series of large scale hydrodynamical simulations for and dynamical Dark Energy (dDE) models, in which the equation of state parameter is dependent. The simulations include gas cooling, star formation and Supernovae feedback. They closely approximate the observed star formation rate and the observationally derived star/Dark Matter mass ratio in collapsed systems. Baryon dynamics cause spectral shifts exceeding 1 per cent at compared to pure N-body simulations in the simulations. This agrees with previous studies, although we find a smaller effect ( per cent) on the power spectrum amplitude at higher values. dDE exhibits similar behaviour, even though the dDE simulations produce per cent less stars than the analogous cosmologies. Finally, we show that the technique introduced in Casarini et al. to obtain spectra for any cosmology from constant- models at any redshift still holds when gas physics is taken into account. While this relieves the need to explore the entire functional space of DE state equations, we illustrate a severe risk that future data analysis could lead to misinterpretation of the DE state equation. [ABSTRACT FROM AUTHOR]

Dynamical dark energy (DE) is a viable alternative to the cosmological constant. Constructing tests to discriminate between Λ and dynamical DE models is difficult, however, because the differences are not large. In this paper we explore tests based on the galaxy mass function, the void probability function (VPF), and the number of galaxy clusters. At high z, the number density of clusters shows large differences between DE models, but geometrical factors reduce the differences substantially. We find that detecting a model dependence in the cluster redshift distribution is a significant challenge. We show that the galaxy redshift distribution is potentially a more sensitive characteristic. We do this by populating dark matter haloes in N-body simulations with galaxies using well-tested halo occupation distributions. We also estimate the VPF and find that samples with the same angular surface density of galaxies, in different models, exhibition almost model-independent VPF which therefore cannot be used as a test for DE. Once again, geometry and cosmic evolution compensate each other. By comparing VPFs for samples with fixed galaxy mass limits, we find measurable differences. [ABSTRACT FROM AUTHOR]

We compute cosmic background radiation (CBR) anisotropies in mixed models with different hot components, including neutrinos or volatile hot dark matter (HDM). The latter arises from heavier particles decaying well before matter--radiation equivalence (lifetime ∼ 10[sup 4]--10[sup 7] s). The CBR power spectra of these models exhibit a higher Doppler peak than cold dark matter (CDM), and the discrepancy is even stronger in volatile models, both because the decay also gives rise to a neutral scalar, and because they allow quite a late derelativization of HDM, even for large Ο[sub h]. CBR experiments, together with large-scale structure (LSS) data, are then used to constrain the space parameter of mixed models, when values of the primeval spectral index n > 1 are also considered. Even if n>1 is allowed, however, LSS alone prescribes that Ο[sub h]90.30. LSS can be fitted by taking simultaneously a low derelativization redshift z[sub der] (down to ≃600, as is allowed in volatile models) and a high n, while CBR data from balloon-borne experiments cause a severe selection on this part of the parameter space. In fact, late derelativization and n>1 have opposite effects on the fluctuation spectrum P(k), while, in contrast, they sum their action on the angular spectrum C[sub l]. Hence, unless we assume a suitable reionization, n01.3 seems excluded by balloon-borne experiment outputs, while a good fit of almost all CBR and LSS data is found for Ω[sub h] values between 0.11 and 0.16, n∼1.1 and z[sub der]∼2000--5000. A smaller n is allowed, but z[sub der] should never be smaller than ≃1200. [ABSTRACT FROM AUTHOR]

If neutrino masses are related by the see-saw relation and $$m_{\nu _\mu } $$ ~2-3 eV, the τ-neutrino must be allowed to decay. Taking into account recent measurements of the cosmic expansion, which yield h≳0.8, the relativistic products of the decay of ν can delay the equivalence as though it were h≌0.3, soproviding a transfer function easy to reconcile with LSS data. This result is obtainable also if the actual final contribution of ν to the present cosmic density is as low as 4% of the critical density. Still keeping the above neutrino mass scale and h∼0.8, alternative choices of physical parameters lead to an earlier equivalence and to a more significant hot component. Altogether, a whole class of models, with hot components characterized by 0.04 ≲ 0.2, can be devised, most of which can be expected to be in reasonable agreement with data. [ABSTRACT FROM AUTHOR]

Copyright of Il Nuovo Cimento: A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Il Nuovo Cimento: B is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Il Nuovo Cimento: B is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is shown that the temperature of the MW background radiation might be directly connected with the details of the quark-hadron phase transition. In fact at temperatures just above 10 GeV the Universe has no room to contain the present baryon number in hadron form. This temperature might be smaller even by a large factor, if a part of the present entropy originated at red-shift ∼ 10 ÷ 100. [ABSTRACT FROM AUTHOR]