Constraining Dark Matter properties with the Inter-Galactic Medium and other probes

According to the standard cosmological (ΛCDM) model, the universe today is mainly composed by a cosmological constant, denoted by Λ, and by Cold Dark Matter (CDM). Whereas this standard paradigm is tremendous agreement with Cosmic Microwave Background (CMB) and Large-Scale Structure (LSS) data, some discrepancies exist, on the cosmological and local determination of the Hubble parameter H 0 , and on the measurement of the amplitude of the matter fluctuations, σ 8 . Additionally, assuming the ΛCDM model, cosmological N -body simulations predict too many dwarf galaxies and too much (C)DM in the innermost regions of galaxies, with respect to observations. Moreover, the dynamical properties of the most massive Milky Way satellites are not reproduced in simulations. The inclusion of baryon feedback is crucial to give a realistic picture of the aforementioned problems, and it shows that baryons can indeed mitigate this CDM “small-scale crisis”. Nevertheless, in the absence of a solution within the ΛCDM framework, and driven by the fact that the fundamental nature of the dark sector is still unrevealed, alternative DM scenarios emerged as a possible way to explain the tensions. In fact, many non-cold (nCDM) candidates have been proposed in order to provide a better description of the structure formation and distribution at small scales, with respect to the ΛCDM model. The effect of the existence of a nCDM particle is a suppression of the matter power spectrum P (k) on small scales, induced, e.g., by its small mass or some non- standard interaction. The suppression in the power spectrum can be described by the so-called transfer function T (k), namely the square root of the ratio of the matter power spectrum in the presence of nCDM with respect to that in the presence of CDM only. Most of the constraints from structure formation data obtained so far, refer to a specific shape of the power suppression, corresponding to the case of thermal Warm DM (WDM), i.e., candidates with a Fermi-Dirac/Bose-Einstein momentum distribution. However, most of the viable particle DM candidates do not feature a thermal momentum distribution, making the oversimplified notion of thermal WDM incapable to describe the shape of their transfer functions. Besides particle DM scenarios, another intriguing possibility that can be tested against small-scale observations is the case where a significant fraction of DM is made by Primordial Black Holes (PBHs), given that Poisson fluctuations in the PBH number density induce a small-scale power enhancement departing from the standard CDM prediction. In this thesis, we firstly introduce a new analytic parametrisation for the transfer function, simple yet versatile enough to describe the gravitational clustering signal of large classes of non-thermal nCDM models, such as sterile neutrinos, ultra-light scalar DM, mixed DM fluids, and interacting DM. The goal is to systematically test these models against the most constraining data set for small-scale deviations with respect to ΛCDM, i.e., high-resolution and high-redshift measurements of the Lyman-α forest, the absorption line pattern produced by intervening inter-galactic neutral hydrogen in the spectra of distant quasars. We thus illustrate how to exploit such observable to constrain practically any non-standard DM scenarios without the need to run any specific numerical simulations, due to the novel parametrisation proposed, to a large suite of pre-computed hydrodynamic simulations, and to an advanced scheme efficiently interpolating across different cosmological models. We demonstrate that the shape of the linear matter power spectrum for thermal WDM models is in mild tension (∼ 2σ C.L.) with data, compared to non-thermal scenarios, and we probe for the first time the small-scale shape of the DM power spectrum for a large set of nCDM models, through extensive Monte Carlo Markov Chain (MCMC) analyses. We then use the Lyman-α data to update current constraints on ultra-light scalar DM models, and we further investigate the cosmological implications at high and low redshifts. For scalar DM constituting more than 30% of the whole of the DM, we obtain a lower limit m & 10 −21 eV for the scalar DM mass, which implies an upper limit on the initial field displacement of φ . 10 16 GeV. We derive limits on the energy scale of cosmic inflation and determine an upper bound on the tensor-to-scalar ratio of r < 10 −3 , in the presence of scalar DM. We also find that there is very little room for scalar DM to solve the CDM small-scale crisis without hitting the Lyman-α bounds. We then focus on quantifying the impact of the Quantum Potential (QP) during the non-linear evolution explored by our hydrodynamic simulations. We improve upon the nearly universally adopted approximation to encode the non-standard nature of the DM candidate in the transfer function used to produce the initial conditions for the simulation, by accurately following the scalar DM evolution in a N -body set-up without approximating its dynamics. Since the new constraints do not depart significantly from the previous ones, this represents the first direct validation of the approximations generally adopted in the literature. Furthermore, we perform a thorough characterisation of the DM halo properties, determining the typical mass scale below which the QP has a significant impact. We then focus on interacting DM scenarios, specifically on models where the dark sector is composed by two types of relic particles, possibly interacting with each other: non-relativistic DM, and relativistic Dark Radiation (DR). Based on the general parametri- sation previously discussed, we introduce a new Lyman-α likelihood, applicable to a wide range of non-standard cosmological models, with complementary scale and redshift coverage with respect to CMB and Baryon Acoustic Oscillation (BAO) data. In fact, for two of the considered interacting scenarios, we find that Lyman-α data strengthen the CMB+BAO bounds on the DM-DR interaction rate by many orders of magnitude. However, models solving the missing satellite problem are still compatible with the new bounds. For the third class of models, Lyman-α data bring no stronger constraints on the interaction rate than CMB+BAO data, except for extremely small values of the DR density. Using a theory-motivated prior on the minimal density of DR, we also find that in this framework the H 0 tension can be reduced from 4.1σ to 2.7σ, while simultaneously accommodating smaller values for σ 8 , as hinted by cosmic shear data. Finally, we present Lyman-α constraints on the PBH mass and abundance, by means of a new grid of high-resolution hydrodynamic simulations. We obtain a marginalised upper limit on the product of the PBH mass and fraction of f PBH M PBH ∼ 60 M at 2σ C.L., when a Gaussian prior on the reionisation redshift is imposed, preventing its posterior distribution to peak on very high values, which are in disagreement with various recent independent measurements. Such constraint weakens to f PBH M PBH ∼ 170 M , when a more conservative flat prior is instead assumed. Both limits improves previous bounds from the same observable by roughly 2 orders of magnitude. We also extend our predictions to non-monochromatic PBH mass distributions, ruling out large parts of the parameter space for two of the most accredited PBH extended mass functions

Constraining Nonthermal Dark Matter's Impact on the Matter Power Spectrum

The inclusion of a period of (effective) matter domination following inflation and prior to the onset of radiation domination has interesting and observable consequences for structure growth. During this early matter-dominated era (EMDE), the Universe was dominated by massive particles, or an oscillating scalar field, that decayed into Standard Model particles, thus reheating the Universe. This decay process could also be the primary source of dark matter. In the absence of fine-tuning between the masses of the parent and daughter particles, both dark matter particles and Standard Model particles would be produced with relativistic velocities. We investigate the effects of the nonthermal production of dark matter particles with relativistic velocities on the matter power spectrum by determining the resulting velocity distribution function for the dark matter. We find that the vast majority of dark matter particles produced during the EMDE are still relativistic at reheating, so their free streaming erases the perturbations that grow during the EMDE. The free streaming of the dark matter particles can also prevent the formation of satellite galaxies around the Milky Way and the structures observed in the Lyman-$\alpha$ forest. For a given reheat temperature, these observations put an upper limit on the velocity of the dark matter particles at their creation. For example, for a reheat temperature of 10 MeV, dark matter must be produced with a Lorentz factor $\gamma \lesssim 550$.Comment: To be submitted to PRD; 14 pages, 13 figures; Updated to match published versio

Novel constraints on noncold, nonthermal dark matter from Lyman-alpha forest data

In this paper, we present an efficient method for constraining both thermal and nonthermal dark matter (DM) scenarios with the Lyman-\u3b1 forest based on a simple and flexible parametrization capable of reproducing the small-scale clustering signal of a large set of noncold DM (NCDM) models. We extract new limits on the fundamental DM properties through an extensive analysis of the high resolution, high redshift data obtained by the MIKE/HIRES spectrographs. By using a large suite of hydrodynamical simulations, we determine constraints on both astrophysical, cosmological, and NCDM parameters by performing a full Monte Carlo Markov chain analysis. We obtain a marginalized upper limit on the largest possible scale at which a power suppression induced by nearly any NCDM scenario can occur, i.e., \u3b1<0.03 Mpc/h (2\u3c3 C.L.). We explicitly describe how to test several of the most viable NCDM scenarios without the need to run any specific numerical simulations due to the novel parametrization proposed and due to a new scheme that interpolates between the cosmological models explored. The shape of the linear matter power spectrum for standard thermal warm DM models appears to be in mild tension ( 3c2\u3c3 C.L.) with the data compared to nonthermal scenarios. We show that a DM fluid composed by both a warm (thermal) and a cold component is also in tension with the Lyman-\u3b1 forest, at least for large \u3b1 values. This is the first study that allows us to probe the linear small-scale shape of the DM power spectrum for a large set of NCDM models

Non-linear damping of superimposed primordial oscillations on the matter power spectrum in galaxy surveys

Galaxy surveys are an important probe for superimposed oscillations on the primordial power spectrum of curvature perturbations, which are predicted in several theoretical models of inflation and its alternatives. In order to exploit the full cosmological information in galaxy surveys it is necessary to study the matter power spectrum to fully non-linear scales. We therefore study the non-linear clustering in models with superimposed linear and logarithmic oscillations to the primordial power spectrum by running high-resolution dark-matter-only N-body simulations. We fit a Gaussian envelope for the non-linear damping of superimposed oscillations in the matter power spectrum to the results of the N-body simulations for k less than or similar to 0.6 h/Mpc at 0 &lt;= z &lt;= 5 with an accuracy below the percent. We finally use this fitting formula to forecast the capabilities of future galaxy surveys, such as Euclid and Subaru, to probe primordial oscillation down to non-linear scales alone and in combination with the information contained in CMB anisotropies

AQUAGRID: an extensible platform for collaborative problem solving in groundwater protection

AQUAGRID is the subsurface hydrology computational service of the Sardinian GRIDA3 infrastructure, designed to deliver complex environmental applications via a user-friendly Web portal. The service aims to provide to water professionals integrated modeling tools to solve water resources management problems and aid decision making for contaminated soil and groundwater. In this paper, the AQUAGRID application concept and enabling technologies are illustrated. At the heart of the service are the computational models to simulate complex and large groundwater flow and contaminant transport problems and geochemical speciation. AQUAGRID is built on top of compute-Grid technologies by means of the EnginFrame Grid framework. Distributed data management is provided by the Storage Resource Broker data-Grid middleware. The resulting environment allows end-users to perform groundwater simulations and to visualize and interact with their results, using graphs, 3D images and annotated maps. The problem solving capability of the platform is demonstrated using the results of two case studies deployed

conceptual design and control strategy of a robotic cell for precision assembly in radar antenna systems

Abstract Dip-Brazing is a metal-joining process in which two or more metal items are joined together using a low-temperature melting element as filler. In telecommunication field, this process is used to fabricate radar antenna systems. The process begins with the assembly of the parts constituting the antenna and the thin filler sheet used to join the parts. The mechanical deformations of the micro-pins of the parts allow to obtain a more compact mechanical assembly, before than the antenna system is subjected to an immersion cycle used for adjoining the parts. In this work, we present the design of the robotic cell to automate the assembly procedure in the aluminum dip-brazing of antenna in MBDA missile systems. In particular, we propose a robotic cell using two stations: i) assembly, using a SCARA manipulator; ii) riveting, using a three-axis cartesian robot designed for positioning a radial riveting unit. Motion control of the robots and scheduling of the operations is presented. Experiments simulated in a virtual environment show an almost perfect tracking of the designed trajectories. The standardization of the procedure as well as the reduction of its execution time is thus achieved for the industrial scenario

Hyperplasia vs hypertrophy in tissue regeneration after extensive liver resection

AIM To address to what extent hypertrophy and hyperplasia contribute to liver mass restoration after major tissue loss. METHODS The ability of the liver to regenerate is remarkable on both clinical and biological grounds. Basic mechanisms underlying this process have been intensively investigated. However, it is still debated to what extent hypertrophy and hyperplasia contribute to liver mass restoration after major tissue loss. We addressed this issue using a genetically tagged system. We were able to follow the fate of single transplanted hepatocytes during the regenerative response elicited by 2/3 partial surgical hepatectomy (PH) in rats. Clusters of transplanted cells were 3D reconstructed and their size distribution was evaluated over time after PH. RESULTS Liver size and liver DNA content were largely recovered 10 d post-PH, as expected (e.g. , total DNA/liver/100 g b.w. was 6.37 ± 0.21 before PH and returned to 6.10 ± 0.36 10 d after PH). Data indicated that about 2/3 of the original residual hepatocytes entered S-phase in response to PH. Analysis of cluster size distribution at 24, 48, 96 h and 10 d after PH revealed that about half of the remnant hepatocytes completed at least 2 cell cycles. Average size of hepatocytes increased at 24 h (248.50 μm2 ± 7.82 μm2, P = 0.0015), but returned to control values throughout the regenerative process (up to 10 d post-PH, 197.9 μm2 ± 6.44 μm2, P = 0.11). A sizeable fraction of the remnant hepatocyte population does not participate actively in tissue mass restoration. CONCLUSION Hyperplasia stands as the major mechanism contributing to liver mass restoration after PH, with hypertrophy playing a transient role in the process

Lyman- \u3b1 Forest Constraints on Primordial Black Holes as Dark Matter

The renewed interest in the possibility that primordial black holes (PBHs) may constitute a significant part of dark matter has provided motivation for revisiting old observational constraints, as well as developing new ones. We present new limits on the PBH abundance, from a comprehensive analysis of high-resolution high-redshift Lyman-\u3b1 forest data. Poisson fluctuations in the PBH number density induce a small-scale power enhancement which departs from the standard cold dark matter prediction. Using a grid of hydrodynamic simulations exploring different values of astrophysical parameters, we obtain a marginalized upper limit on the PBH mass of fPBHMPBH 3c60M at 2\u3c3, when a Gaussian prior on the reionization redshift is imposed, preventing its posterior distribution from peaking on very high values, which are disfavored by the most recent estimates obtained both through cosmic microwave background and intergalactic medium observations. Such a bound weakens to fPBHMPBH 3c170M when a conservative flat prior is instead assumed. Both limits significantly improve on previous constraints from the same physical observable. We also extend our predictions to nonmonochromatic PBH mass distributions, ruling out large regions of the parameter space for some of the most viable PBH extended mass functions

Surfactant-assisted distal pulmonary distribution of Budesonide revealed by mass spectrometry imaging

13openInternationalBothDirect lung administration of budesonide in combination with surfactant reduces the incidence of bronchopulmonary dysplasia. Although the therapy is currently undergoing clinical development, the lung distribution of budesonide throughout the premature neonatal lung has not yet been investigated. Here, we applied mass spectrometry imaging (MSI) to investigate the surfactant-assisted distal lung distribution of budesonide. Unlabeled budesonide was either delivered using saline as a vehicle (n = 5) or in combination with a standard dose of the porcine surfactant Poractant alfa (n = 5). These lambs were ventilated for one minute, and then the lungs were extracted for MSI analysis. Another group of lambs (n = 5) received the combination of budesonide and Poractant alfa, followed by two hours of mechanical ventilation. MSI enabled the label-free detection and visualization of both budesonide and the essential constituent of Poractant alfa, the porcine surfactant protein C (SP-C). 2D ion intensity images revealed a non-uniform distribution of budesonide with saline, which appeared clustered in clumps. In contrast, the combination therapy showed a more homogeneous distribution of budesonide throughout the sample, with more budesonide distributed towards the lung periphery. We found similar distribution patterns for the SP-C and budesonide in consecutive lung tissue sections, indicating that budesonide was transported across the lungs associated with the exogenous surfactant. After two hours of mechanical ventilation, the budesonide intensity signal in the 2D ion intensity maps dropped dramatically, suggesting a rapid lung clearance and highlighting the relevance of achieving a uniform surfactant-assisted lung distribution of budesonide early after delivery to maximize the anti-inflammatory and maturational effects throughout the lungopenZecchi, Riccardo; Franceschi, Pietro; Tigli, Laura; Pioselli, Barbara; Mileo, Valentina; Murgia, Xabier; Salomone, Fabrizio; Pieraccini, Giuseppe; Usada, Haruo; Schmidt, Augusto F; Hillman, Noah H.; Kemp, Matthew W.; Jobe, Alan H.Zecchi, R.; Franceschi, P.; Tigli, L.; Pioselli, B.; Mileo, V.; Murgia, X.; Salomone, F.; Pieraccini, G.; Usada, H.; Schmidt, A.F.; Hillman, N.H.; Kemp, M.W.; Jobe, A.H