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We present an optimization scheme for the focal plane of a multi-frequency CMB B-modes experiment with a fixed number of detectors and apply it to the specific case of LSPE experiment. Optimal focal planes are identified on the ground of different figures of merit defined in terms of the forecasted uncertainty $\sigma_r$ on the tensor--to-scalar ratio $r$ and the expected map variance from foreground and instrumental noise residuals. We then perform a forecast analysis in order to assess the precision achievable in B-modes measurements., Comment: 20 pages, 10 figures

Strongly Coupled Dark Energy plus Warm dark matter (SCDEW) cosmologies admit the stationary presence of $\sim 1\, \%$ of coupled-DM and DE, since inflationary reheating. Coupled-DM fluctuations therefore grow up to non-linearity even in the early radiative expansion. Such early non-linear stages are modelized here through the evolution of a top-hat density enhancement, reaching an early virial balance when the coupled-DM density contrast is just 25-26 and DM density enhancement is $ \sim 10\, \%$ of total density. During the time needed to settle in virial equilibium, the virial balance conditions however continue to modify, so that "virialized" lumps undergo a complete evaporation. Here we outline that DM particles processed by overdentities preserve a fraction of their virial momentum. Although fully non-relativistic, the resulting velocities (moderately) affect the fluctuation dynamics over greater scales, entering the horizon later on., Comment: 20 pages, 7 figures; updated to match the published version

Strongly Coupled Dark Energy plus Warm dark matter (SCDEW) cosmologies are based on the finding of a conformally invariant (CI) attractor solution during the early radiative expansion, requiring then the stationary presence of $\sim 1\, \%$ of coupled-DM and DE, since inflationary reheating. In these models, coupled-DM fluctuations, even in the early radiative expansion, grow up to non-linearity, as shown in a previous associated paper. Such early non-linear stages are modelized here through the evolution of a top-hat density enhancement. As expected, its radius $R$ increases up to a maximum and then starts to decrease. Virial balance is reached when the coupled-DM density contrast is just 25-26 and DM density enhancement is $\cal O$$(10\, \%)$ of total density. Moreover, we find that this is not an equilibrium configuration as, afterwards, coupling causes DM particle velocities to increase, so that the fluctuation gradually dissolves. We estimate the duration of the whole process, from horizon crossing to dissolution, and find $z_{horizon}/z_{erasing} \sim 3 \times 10^4$. Therefore, only fluctuations entering the horizon at $z \lesssim 10^9$-$10^{10}$ are able to accrete WDM with mass $\sim 100\, $eV -as soon as it becomes non-relativistic- so avoiding full disruption. Accordingly, SCDEW cosmologies, whose WDM has mass $\sim 100\, $eV, can preserve primeval fluctuations down to stellar mass scale., Comment: 18 pages, 9 figures, updated to match the published version

Cosmologies including strongly Coupled (SC) Dark Energy (DE) and Warm dark matter (SCDEW) are based on a conformally invariant (CI) attractor solution modifying the early radiative expansion. Then, aside of radiation, a kinetic field $\Phi$ and a DM component account for a stationary fraction, $\sim 1\, \%$, of the total energy. Most SCDEW predictions are hardly distinguishable from LCDM, while SCDEW alleviates quite a few LCDM conceptual problems, as well as its difficulties to meet data below the average galaxy scale. The CI expansion begins at the inflation end, when $\Phi$ (future DE) possibly plays a role in reheating, and ends at the Higgs' scale. Afterwards, a number of viable options is open, allowing for the transition from the CI expansion to the present Universe. In this paper: (i) We show how the attractor is recovered when the spin degrees of freedom decreases. (ii) We perform a detailed comparison of CMB anisotropy and polarization spectra for SCDEW and LCDM, including tensor components, finding negligible discrepancies. (iii) Linear spectra exhibit a greater parameter dependence at large $k$'s, but are still consistent with data for suitable parameter choices. (iv) We also compare previous simulation results with fresh data on galaxy concentration. Finally, (v) we outline numerical difficulties at high $k$. This motivates a second related paper, where such problems are treated in a quantitative way., Comment: 23 pages, 10 figures, accepted for publication in JCAP. Updated to match the published version

In the early Universe, strongly interacting matter was a quark-gluon plasma. Both lattice computations and heavy ion collision experiments however tell us that, in the absence of chemical potentials, no plasma survives at $T <\sim 150$ MeV. The cosmological Quark-Hadron transition, however, seems to have been a crossover; cosmological consequences envisaged when it was believed to be a phase transition no longer hold. In this paper we discuss whether even a crossover transition can leave an imprint that cosmological observations can seek or, viceversa, there are questions cosmology should address to QCD specialists. In particular, we argue that it is still unclear how baryons (not hadrons) could form at the cosmological transition. A critical role should be played by diquark states, whose abundance in the early plasma needs to be accurately evaluated. We estimate that, if the number of quarks belonging to a diquark state, at the beginning of the cosmological transition, is $<\sim 1:10^6$, its dynamics could be modified by the process of B-transfer from plasma to hadrons. In turn, by assuming B-transfer to cause just mild perturbations and, in particular, no entropy input, we study the deviations from the tracking regime, in the frame of SCDEW models. We find that, in some cases, residual deviations could propagate down to primeval nuclesynthesis., Comment: 16 pages, 8 figures; published in Universe

In this first paper we discuss the linear theory and the background evolution of a new class of models we dub SCDEW: Strongly Coupled DE, plus WDM. In these models, WDM dominates today's matter density; like baryons, WDM is uncoupled. Dark Energy is a scalar field $\Phi$; its coupling to ancillary CDM, whose today's density is $\ll 1\, \%$, is an essential model feature. Such coupling, in fact, allows the formation of cosmic structures, in spite of very low WDM particle masses ($\sim 100$ eV). SCDEW models yields Cosmic Microwave Background and linear Large Scale features substantially undistinguishable from $\Lambda$CDM, but thanks to the very low WDM masses they strongly alleviate $\Lambda$CDM issues on small scales, as confirmed via numerical simulations in the II associated paper. Moreover SCDEW cosmologies significantly ease the coincidence and fine tuning problems of $\Lambda$CDM and, by using a field theory approach, we also outline possible links with inflationary models. We also discuss a possible fading of the coupling at low redshifts which prevents non linearities on the CDM component to cause computational problems. The (possible) low-$z$ coupling suppression, its mechanism, and its consequences are however still open questions -not necessarily problems- for SCDEW models. The coupling intensity and the WDM particle mass, although being extra parameters in respect to $\Lambda$CDM, are found to be substantially constrained a priori so that, if SCDEW is the underlying cosmology, we expect most data to fit also $\Lambda$CDM predictions., Comment: 11 pages, 9 figures , accepted for publication on MNRAS; updated to match the published version; the companion paper can be found here http://arxiv.org/abs/1503.07867

In this second paper we present the first Nbody cosmological simulations of strongly coupled Dark Energy models (SCDEW), a class of models that alleviates theoretical issues related to the nature of dark energy. SCDEW models assume a strong coupling between Dark Energy (DE) and an ancillary Cold Dark Matter (CDM) component together with the presence of an uncoupled Warm Dark Matter component. The strong coupling between CDM and DE allows us to preserve small scale fluctuations even if the warm particle is quite light ($\approx 100$ eV). Our large scale simulations show that, for $10^{11}

Halo masses and concentrations have been studied extensively, by means of N-body simulations as well as observationally, during the last decade. Nevertheless, the exact form of the mass-concentration relation is still widely debated. One of the most promising method to estimate masses and concentrations relies on gravitational lensing from massive halos. Here we investigate the impact of the mass-concentration relation on halo peak abundance in weak lensing shear maps relying on the aperture mass method for peak detections. After providing a prescription to take into account the concentration dispersion (always neglected in previous works) in peak number counts predictions, we assess their power to constrain the mass-concentration relation by means of Fisher matrix technique. We find that, when combined with different cosmological probes, peak statistics information from near-future weak lensing surveys provides an interesting and complementary alternative method to lessen the long standing controversy about the mass-concentration relation., Comment: 32 pages, 15 figures, 4 tables; some points clarified, improved section on fisher matrix analysis and discussion. Published version

In the early Universe, a dual component made of coupled CDM and a scalar field $\Phi$, if their coupling $\beta > \sqrt{3}/2$, owns an attractor solution, making them a stationary fraction of cosmic energy during the radiation dominated era. Along the attractor, both such components expand $\propto a^{-4}$ and have early density parameters $\Omega_{d} = 1/ (4\beta^2)$ and $\Omega_c= 2, \Omega_d$ (field and CDM, respectively). In a previous paper it was shown that, if a further component, expanding $\propto a^{-3}$, breaks such stationary expansion at $z \sim 3$--$5 \times 10^3$, cosmic components gradually acquire densities consistent with observations. This paper, first of all, considers the case that this component is warm. However, its main topic is the analysis of fluctuation evolution: out of horizon modes are then determined; their entry into horizon is numerically evaluated as well as the dependence of Meszaros effect on the coupling $\beta$; finally, we compute: (i) transfer function and linear spectral function; (ii) CMB $C_l$ spectra. Both are close to standard $\Lambda$CDM models; in particular, the former one can be so down to a scale smaller than Milky Way, in spite of its main DM component being made of particles of mass $<1$ keV. The previously coupled CDM component, whose present density parameter is $\cal O$$(10^{-3})$, exhibits wider fluctuations $\delta \rho/\rho$, but approximately $\beta$-independent $\delta \rho$ values. We discuss how lower scale features of these cosmologies might ease quite a few problems that $\Lambda$CDM does not easily solve., Comment: 25 pages, 7 figures, accepted for publication on JCAP; updated to match the published version

We provide an exhaustive analysis of the Integrated Sach-Wolfe effect (ISW) in the context of coupled Dark Energy cosmologies where a component of massive neutrinos is also present. We focus on the effects of both the coupling between Dark Matter and Dark Energy and of the neutrino mass on the cross-correlation between galaxy/quasar distributions and ISW effect. We provide a simple expression to appropriately rescale the galaxy bias when comparing different cosmologies. Theoretical predictions of the cross-correlation function are then compared with observational data. We find that, while it is not possible to distinguish among the models at low redshifts, discrepancies between coupled models and $\Lambda$CDM increase with $z$. In spite of this, current data alone seems not able to distinguish between coupled models and $\Lambda$CDM. However, we show that upcoming galaxy surveys will permit tomographic analysis which allow to better discriminate among the models. We discuss the effects on cross-correlation measurements of ignoring galaxy bias evolution, b(z), and magnification bias correction and provide fitting formulae for b(z) for the cosmologies considered. We compare three different tomographic schemes and investigate how the expected signal to noise ratio, snr, of the ISW-LSS cross-correlation changes when increasing the number of tomographic bins. The dependence of snr on the area of the survey and the survey shot noise is also discussed., Comment: 18 pages, 23 figures. Several major extensions. New sections and figures was added. ApJ in print

We investigate the clustering properties of dynamical Dark Energy even in association of a possible coupling between Dark Energy and Dark Matter. We find that within matter inhomogeneities, Dark Energy migth form voids as well as overdensity depending on how its background energy density evolves. Consequently and contrarily to what expected, Dark Energy fluctuations are found to be slightly suppressed if a coupling with Dark Matter is permitted. When considering density contrasts and scales typical of superclusters, voids and supervoids, perturbations amplitudes range from $|\delta_\phi|\sim {\cal O} (10^{-6})$ to $|\delta_\phi|\sim {\cal O} (10^{-4})$ indicating an almost homogeneous Dark Energy component., Comment: 21 pages, 12 figures, submitted to JCAP

The properties of dynamical Dark Energy (DE) and, in particular, the possibility that it can form or contribute to stable inhomogeneities, have been widely debated in recent literature, also in association to a possible coupling between DE and Dark Matter (DM). In order to clarify this issue, in this paper we present a general framework for the study of the nonlinear phases of structure formation, showing the equivalence between two possible descriptions of DE: a scalar field \phi self-interacting through a potential V(\phi) and a perfect fluid with an assigned negative equation of state w(a). This enables us to show that, in the presence of coupling, the mass of DE quanta may increase where large DM condensations are present, so that also DE may partake to the clustering process., Comment: 16 pages, accepted for publication in JCAP

A phaenomenological DM-DE coupling could indicate their common origin. Various constraint however exist to such coupling; here we outline that it can suppress Meszaros' effect, yielding transfered spectra with a softer bending above k_{hor,eq}. It could be therefore hard to reconcile these models with both CMB and deep sample data, using a constant spectral index., Comment: 4 pages, 4 figures, proceedings of PASCOS 2007, 2-7 July, London

DM--DE coupling can be a phenomenological indication of a common origin of the dark cosmic components. In this work we outline a new constraint to coupled--DE models: the coupling can partially or totally suppress the Meszaros effect, yielding transfered spectra with quite a soft bending above $k_{hor,eq}$. Models affected by this anomaly do not show major variation in the CMB anisotropy spectrum and it is herefore hard to reconcile them with both CMB and deep sample data, through the same value of the primeval spectral index., Comment: 20 pages, 13 figures, abstract revised, some points clarified, 2 figures added. Accepted for publication in JCAP

We compare a large set of cosmologies with WMAP data, performing a fit based on a MCMC algorithm. Besides of LCDM models, we take dynamical DE models, where DE and DM are uncoupled or coupled, both in the case of constant coupling and in the case when coupling varies with suitable laws. DE however arises from a scalar field self-interacting through a SUGRA potential. We find that the best fitting model is SUGRA dynamical DE, almost indipendently from the exponent alpha in the self-interaction potential. The main target of this work are however coupled DE models, for which we find limits on the DE-DM coupling strength. In the case of variable coupling, we also find that greater values of the Hubble constant are preferred., Comment: 21 pages, 10 figures

The strong CP problem was solved by Peccei & Quinn by introducing axions, a viable candidate for Dark Matter (DM). Here the PQ approach is modified so to yield also Dark Energy (DE). DM and DE arise, in fai proportions, from a single scalar field, without tuning any extra parameter. In the present epoch, they are weakly coupled. Fluctuations have a fair evolution. The model is also fitted to the WMAP1 release, using a Markov Chain Monte Carlo technique, and performs as well as $\Lambda$CDM, coupled or uncoupled DE. Best--fit cosmological parameters for different models are mostly within 2--$\sigma$ level. Here, the main peculiarity of the model is to favor high values of the Hubble parameter., Comment: Proceeding of the workshop dsu2006, "The Dark Side of th Universe", Madrid, June 20-24, 2006

We evaluate the mass function of virialized halos, by using Press & Schechter (PS) and/or Steth & Tormen (ST) expressions, for cosmologies where Dark Energy (DE) is due to a scalar self-interacting field, coupled with Dark Matter (DM). We keep to coupled DE (cDE) models known to fit linear observables. To implement the PS-ST approach, we start from reviewing and extending the results of a previous work on the growth of a spherical top-hat fluctuation in cDE models, confirming their most intriguing astrophysical feature, i.e. a significant baryon-DM segregation, occurring well before the onset of any hydrodynamical effect. Accordingly, the predicted mass function depends on how halo masses are measured. For any option, however, the coupling causes a distortion of the mass function, still at z=0. Furthermore, the z-dependence of cDE mass functions is mostly displaced, in respect to LambdaCDM, in the opposite way of uncoupled dynamical DE. This is an aspect of the basic underlying result, that even a little DM-DE coupling induces relevant modifications in the non-linear evolution. Therefore, without causing great shifts in linear astrophysical observables, the DM-baryon segregation induced by the coupling can have an impact on a number of cosmological problems, it e.g., galaxy satellite abundance, spiral disk formation, apparent baryon shortage, entropy input in clusters, etc.., Comment: 27 pages, 14 figures. PS replaced with ST. New figures added. Pages 14-15 rewritten

The growth and virialization of spherical top-hat fluctuations, in coupled Dark Energy models, causes segregation between Dark Matter (DM) and baryons, as the gravitational infall into the potential well proceeds more slowly for the baryons than for DM. As a consequence, after attaining their turn-around and before full virialization, halos have outer layers rich of baryons. Accordingly, a natural ambiguity exists on the definition of the virial density contrast. In fact, when the outer baryon layers infall onto the DM-richer core, they carry with them DM materials outside the original fluctuation; hence, no time exists when all materials originally belonging to the fluctuation -and only them- have virialized. Baryon-DM segregation can have various astrophysical consequences on different length-scales. The smallest halos may loose up to 50% of the original baryonic contents and become hardly visible. Subhalos in cluster-size halos may loose much baryonic materials, which could then be observed as intra-cluster light. Isolated halos, in general, can be expected to have a baryon component richer than the cosmological proportions, due to the cosmic enrichement of baryons lost in small halo encounters., Comment: 22 pages, 9 figures, accepted version: comparison with a different potential provided, new figures and references added

The strong CP problem was solved by Peccei & Quinn by introducing axions, which are a viable candidate for DM. Here the PQ approach is modified so to yield also Dark Energy (DE), which arises in fair proportions, without tuning any extra parameter. DM and DE arise from a single scalar field and, in the present ecpoch, are weakly coupled. Fluctuations have a fair evolution. The model is also fitted to WMAP release, using a MCMC technique, and performs as well as LCDM, coupled or uncoupled Dynamical DE. Best-fit cosmological parameters for different models are mostly within 2-$\sigma$ level. The main peculiarity of the model is to favor high values of the Hubble parameter., Comment: Poster presented at the XXII Texas Symposium on Relativistic Astrophysics, Stanford University, December 2004, (TSRA04, PSN1105) 5 pages, 6 figures

Axions are likely to be the Dark Matter (DM) that cosmological data require. They arise in the Peccei Quinn solution of the strong CP problem. In a previous work we showed that their model has a simple and natural generalization which yields also Dark Energy (DE), in fair proportions, without tuning any parameter: DM and DE arise from a single scalar field and are weakly coupled in the present era. In this paper we extend the analysis of this dual-axion cosmology and fit it to WMAP data, by using a Markov chain technique. We find that LCDM, dynamical DE with a SUGRA potential, DE with a SUGRA potential and a constant DE-DM coupling, as well as the dual-axion model with a SUGRA potential, fit data with a similar accuracy. The best-fit parameters are however fairly different, although consistency is mostly recovered at the 2-sigma level. A peculiarity of the dual-axion model with SUGRA potential is to cause more stringent constraints on most parameters and to favor high values of the Hubble parameter., Comment: 34 pages, 15 figures, replaced with accepted version

The Peccei Quinn (PQ) solution of the strong CP problem requires the existence of axions, which are a viable candidate for Dark Matter. Here we show that, if the Nambu Goldstone potential of the PQ model is replaced by a potential V(|\Phi|) admitting a tracker solution, the scalar field |\Phi| can account for Dark Energy, while the phase of \Phi yields axion Dark Matter. Such Dark Matter and Dark Energy turn out to be weakly coupled. If V is a SUGRA potential, the model essentially depends on a single parameter, the energy scale \Lambda. Once we set \Lambda \simeq 10^{10} GeV, at the quark--hadron transition, |\Phi| naturally passes through values suitable to solve the strong CP problem, later growing to values providing fair amounts of Dark Matter and Dark Energy. In this model, the linear growth factor, from recombination to now, is quite close to \LambdaCDM. The selected \Lambda value can be an indication of the scale where the soft breaking of SUSY occurred., Comment: 10 pages, 5 figures Revised abstract and added new section on fluctuation evolution. Phys Rev Lett (in press)

We present the results of a series of N-body simulations in cosmologies where dark matter (DM) is coupled to dark energy (DE), so easing the cosmic coincidence problem. The dark-dark coupling introduces two novel effects in N-body dynamics: (i) DM particle masses vary with time; (ii) gravity between DM particles is ruled by a constant $G^{*}$, greater than Newton's constant $G$, holding in other 2-body interactions. As a consequence, baryons and DM particle distributions develop a large scale bias. Here we investigate DE models with Ratra-Peebles (RP) potentials; the dark-dark coupling is set in a parametric range compatible with observations, for as concern background and linear perturbation properties. We study the halo mass function, the halo density profile and the behavior of the non-linear bias. We find that non-linear dynamics puts additional constraints to the coupling parameter. They mostly arise from density profiles, that we find to yield higher concentrations, in coupled RP models, with respect to (uncoupled) dynamical DE cosmologies. Such enhancement, although being a strong effect in some coupling parameter range, is just a minor change for smaller but significant values of the coupling parameter. With these further restrictions, coupled DE models with RP potential are consistent with non-linear observables., Comment: 12 pages, 10 figures, v2, added some references, submitted to Phys.Rev.D