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The INFN-CNAF data centre hosts the Italian Tier~1 site for the Worldwide LHC Computing Grid (WLCG), while also serving several other research and technological transfer programs. The challenges posed by the upcoming runs of LHC, together with the opportunity of moving the data centre itself to a bigger site, require a thorough redesign of its monitoring system. The large but heterogeneous amount of logging data and metrics produced daily are fundamental for monitoring activities and, once harmonised, can also be used to build Predictive Maintenance models based on Big Data techniques. In this work we describe the Big Data Platform, a new monitoring infrastructure under development at CNAF. The Big Data Platform relies on a modular, highly scalable architecture based on open source technologies and able to exploit modern frameworks such as containerisation and cloud support. It is capable of collecting data from heterogeneous data sources, clean and harmonise them, and store them as JSON files on different solutions, based on the needs of the end user. Data can then be visualised using Kibana, or analysed through a platform based on Jupyter Notebooks.

We exploit the many-body self-consistent Green's function method to analyze finite-temperature properties of infinite nuclear matter and to explore the behavior of the thermal index used to simulate thermal effects in equations of state for astrophysical applications. We show how the thermal index is both density and temperature dependent, unlike often considered, and we provide an error estimate based on our ${\it ab~initio}$ calculations. The inclusion of many-body forces is found to be critical for the density dependence of the thermal index. We also compare our results to a parametrization in terms of the density dependence of the nucleon effective mass. Our study questions the validity of predictions made for the gravitational-wave signal from neutron-star merger simulations with a constant thermal index., 11 pages, 7 figures, added references

We study if commonly used nucleon-nucleon effective interactions, obtained from fitting the properties of cold nuclear matter and of finite nuclei, can properly describe the hot dense nuclear matter produced in intermediate-energy heavy-ion collisions. We use two representative effective interactions, i.e., an improved isospin- and momentum-dependent interaction with its isovector part calibrated by the results from the \emph{ab initio} non-perturbative self-consistent Green's function (SCGF) approach with chiral forces, and a Skyme-type interaction fitted to the equation of state of cold nuclear matter from chiral effective many-body perturbation theory and the binding energy of finite nuclei. In the mean-field approximation, we evaluate the equation of state and the single-nucleon potential for nuclear matter at finite temperatures and compare them to those from the SCGF approach. We find that the improved isospin- and momentum-dependent interaction reproduces reasonably well the SCGF results due to its weaker momentum dependence of the mean-field potential than in the Skyrme-type interaction. Our study thus indicates that effective interactions with the correct momentum dependence of the mean-filed potential can properly describe the properties of hot dense nuclear matter and are thus suitable for use in transport models to study heavy-ion collisions at intermediate energies., 10 pages, 7 figures

We present an error band on neutron matter properties at finite temperature (finite-T) which comprehends uncertainties on the nuclear interaction, the many-body method convergence, and the thermodynamical consistency of the approach. This study provides nonperturbative predictions for finite-T neutron matter employing chiral interactions which are selected on the basis of their performance in both finite nuclei and infinite matter at zero temperature. Since proper theoretical uncertainties at finite-T are still generally lacking, the band provided here represents a first step towards setting first-principles constraints on thermal aspects of the nuclear matter equation of state., Comment: 7 pages, 4 figures; article reorganized in sections, added paragraphs and references

We present first-principle predictions for the liquid-gas phase transition in symmetric nuclear matter employing both two- and three-nucleon chiral interactions. Our discussion focuses on the sources of systematic errors in microscopic quantum many body predictions. On the one hand, we test uncertainties of our results arising from changes in the construction of chiral Hamiltonians. We use five different chiral forces with consistently derived three-nucleon interactions. On the other hand, we compare the ladder resummation in the self-consistent Green's functions approach to finite temperature Brueckner--Hartree--Fock calculations. We find that systematics due to Hamiltonians dominate over many-body uncertainties. Based on this wide pool of calculations, we estimate that the critical temperature is $T_c=16 \pm 2$ MeV, in reasonable agreement with experimental results. We also find that there is a strong correlation between the critical temperature and the saturation energy in microscopic many-body simulations., Comment: 14 pages, 7 figures

We present the fundamental techniques and working equations of many-body Green's function theory for calculating ground state properties and the spectral strength. Green's function methods closely relate to other polynomial scaling approaches discussed in chapters 8 and 10. However, here we aim directly at a global view of the many-fermion structure. We derive the working equations for calculating many-body propagators, using both the Algebraic Diagrammatic Construction technique and the self-consistent formalism at finite temperature. Their implementation is discussed, as well as the inclusion of three-nucleon interactions. The self-consistency feature is essential to guarantee thermodynamic consistency. The pairing and neutron matter models introduced in previous chapters are solved and compared with the other methods in this book.

We analyze microscopic many-body calculations of the nuclear symmetry energy and its density dependence. The calculations are performed in the framework of the Brueckner-Hartree-Fock and the Self-Consistent Green's Functions methods. Within Brueckner-Hartree-Fock, the Hellmann-Feynman theorem gives access to the kinetic energy contribution as well as the contributions of the different components of the nucleon-nucleon interaction. The tensor component gives the largest contribution to the symmetry energy. The decomposition of the symmetry energy in a kinetic part and a potential energy part provides physical insight on the correlated nature of the system, indicating that neutron matter is less correlated than symmetric nuclear matter. Within the Self-Consistent Green's Function approach, we compute the momentum distributions and we identify the effects of the high momentum components in the symmetry energy. The results are obtained for the realistic interaction Argonne V18 potential, supplemented by the Urbana IX three-body force in the Brueckner-Hartree-Fock calculations., Comment: 14 pages, 6 figures. Minor changes, accepted in EPJA special volume on Nuclear Symmetry Energy

[cat] El problema quàntic de molts cossos ha estat sempre un repte de la física teòrica. L'objectiu al qual s'intenta arribar es la descripció, des d'un punt de vista quàntic, dels observables d'un sistema de moltes partícules en interacció. En el camp específic dels sistemes nuclears, dels més petits com els nuclis als més grans com la matèria nuclear infinita dins de les estrelles, el problema nuclear de molts cossos s'ha intentat resoldre amb la construcció de diferents formalismes. L'objectiu ha sigut descriure aproximadament el comportament de molts nucleons, obtenen resultats els més propers als experimentals i empírics. En la present tesis ens hem centrat sobre l'estudi de la matèria nuclear infinita. En particular sobre els dos sistemes infinits que es situen en els extrems en termes d'asimetria d'isospín: la matèria nuclear simètrica (SNM), el sistema format d'un igual nombre de protons i nucleons, i la matèria purament neutrónica (PNM), el sistema format solament de neutrons. Per dur a terme aquests càlculs hem expandit, de manera consistent, el formalisme de funcions de Green auto-consistents per incloure forces a tres cossos. Hem treballat amb un potencial basat en la teoria efectiva de baixes energies aplicada a la Cromodinàmica Quàntica (QCD), i.e. la teoria efectiva quiral. En aquesta teoria, les 2NFs i 3NFs apareixen consistentment. La inclusió de les forces a tres cossos en els càlculs s'ha demostrat ser fonamental per obtenir el mecanisme de saturació en SNM al voltant de valors acceptables d'energia/densitat i per proporcionar una equació d'estat més rígida per al sistema de PNM. Això demostra, un cop més, la necessitat de considerar les forces de molts cossos per fel càlculs teòrics consistents amb els resultats empírics i experimentals., [eng] The quantum many-body problem is an everlasting challenge for theoretical physics. The aim sought is to analyze, at the quantum level, the observables arising from a group formed by a certain number of interacting particles N. In the specific case of nuclear physics, the study and interpretation of interacting nuclear systems has spanned from the finite nuclei to the infinite nuclear matter case. In order to characterize such systems, the forces with which nucleons interact in their interior need to be sorted out. Once the Hamiltonian is chosen, the many-body problem for the group of interacting fermions, the nucleons, has to be solved. In the present thesis we focus our study on infinite nuclear matter, analyzing the properties of the two systems which stand at the extremes in terms of isospin asymmetry: symmetric nuclear matter (SNM), with an equal number on neutrons and protons, and pure neutron matter (PNM), with only neutrons. We base our approach in terms of realistic microscopic potentials, hence we need to choose a many-body technique in order to treat the potential. We choose to perform our calculations exploiting the formalism provided by the self-consistent Green's function's (SCGF) theory. This approach is based on a diagrammatic expansion of the single-particle (SP) Green's function, or propagator. This method was devised to treat the correlated, i.e. beyond mean-field, behavior of strongly interacting systems, such as nuclear matter. Unfortunately, it is a well established fact that whatever microscopic two-nucleon forces (2NFs) are used in the many-body calculation, empirical saturation properties of nuclear matter fail to be reproduced. Saturation densities appear at high values, presenting energies which are inconsistently too attractive, overbinding nuclear matter. This inconsistency bears some similarities to the case of light nuclei where, on the contrary, the 2NF-only based theory underbinds experimental data. The inclusion of three-nucleon forces (3NFs) has been the indispensable factor to cure this deficiency. Hence, microscopic 3NFs have been mostly devised to provide attraction in light finite systems, small densities, and repulsion in infinite systems, high densities. However, in modeling these 3NFs, the inclusion of phenomenological ingredients has often been the way followed. To bypass the need to adjust the potential with ad hoc contributions, an alternative has been provided by chiral effective field theory (EFT). Featuring the consistent Hamiltonian at the 2N and 3N level provided by EFT, in this thesis we present calculations including both chiral 2NFs and 3NFs. This is dealt within an extended SCGF formalism, specifically formulated to include consistently 3B forces by means of effective interactions. We observe the striking effect of the inclusion of 3N forces for the total energy of the many-body ground state. Exploiting the extended SCGF approach presented in this thesis, we see how the modifications induced by the 3B force are larger as the density increases. This increasing with density is what provides the saturation mechanism for nuclear matter. In pure neutron matter, 3NFs are the main cause for the stiffening of the equation of state. In view of astrophysical studies for neutron star masses, this stiffening is a major ingredient for the achievement of theoretical results which can better match recent astrophysical observations. The idea, on which the development of this thesis was based, has been all the way the quest to introduce consistently three-body forces in the formalism of the SCGF theory. While the main motivation of this study has been nuclear systems, the extended SCGF formalism can be easily applied to other many-body systems, of either atomic or molecular nature.

We extend the self-consistent Green's functions formalism to take into account three-body interactions. We analyze the perturbative expansion in terms of Feynman diagrams and define effective one- and two-body interactions, which allows for a substantial reduction of the number of diagrams. The procedure can be taken as a generalization of the normal ordering of the Hamiltonian to fully correlated density matrices. We give examples up to third order in perturbation theory. To define nonperturbative approximations, we extend the equation of motion method in the presence of three-body interactions. We propose schemes that can provide nonperturbative resummation of three-body interactions. We also discuss two different extensions of the Koltun sum rule to compute the ground state of a many-body system., Comment: 26 pages, 19 figures

We present calculations for symmetric nuclear matter using chiral nuclear interactions within the Self-Consistent Green's Functions approach in the ladder approximation. Three-body forces are included via effective one-body and two-body interactions, computed from an uncorrelated average over a third particle. We discuss the effect of the three-body forces on the total energy, computed with an extended Galitskii-Migdal-Koltun sum-rule, as well as on single-particle properties. Saturation properties are substantially improved when three-body forces are included, but there is still some underlying dependence on the SRG evolution scale., Comment: 12 pages, 12 figures

The liquid-gas phase transition in nuclear systems is a unique phenomenon, at the frontier of nuclear, many-body and statistical physics. We study this phase transition theoretically at the Hartree-Fock level and explore the available parameter space for the critical point by using several mean-field parametrizations. We find the latent heat of the transition and describe its temperature dependence from first principles. Using tools from many-body physics, we also describe the phase transition beyond the mean-field approximation and find a marked dependence on both the microscopic interaction and the many-body approximation scheme.

The short-range and tensor correlations associated to realistic nucleon-nucleon interactions induce a population of high-momentum components in the many-body nuclear wave function. We study the impact of such high-momentum components on bulk observables associated to isospin asymmetric matter. The kinetic part of the symmetry energy is strongly reduced by correlations when compared to the non-interacting case. The origin of this behavior is elucidated using realistic interactions with different short-range and tensor structures., Comment: 15 pages

We study the latent heat of the liquid-gas phase transition in symmetric nuclear matter using self-consistent mean-field calculations with a few Skyrme forces. The temperature dependence of the latent heat is rather independent of the mean-field parametrization and can be characterized by a few parameters. At low temperatures, the latent heat tends to the saturation energy. Near the critical point, the latent heat goes to zero with a well-determined mean-field critical exponent. A maximum value of the latent heat in the range l ~ 25-30 MeV is found at intermediate temperatures, which might have experimental relevance. All these features can be explained from very basic principles., 25 pages, 7 figures

Viscosity plays a critical role in determining the stability of rotating neutron stars. We report the results of a calculation of the shear viscosity of $\beta$~-~stable matter, carried out using an effective interaction based on a state-of-the-art nucleon-nucleon potential and the formalism of correlated basis functions. Within our approach the equation of state, determining the proton fraction, and the nucleon-nucleon scattering probability are consistently obtained from the same dynamical model. The results show that, while the neutron contribution to the viscosity is always dominant, above nuclear saturation density the electron contribution becomes appreciable.

The transport properties of matter in the interior of rotating neutron stars play a critical role in determining the evolution of these compact objects. In this brief report we discuss a study of the shear viscosity of stellar matter composed by neutrons, protons and electrons in equilibrium with respect to β decay and electronic capture. The aim of this work is calculate in a fully consistent manner the equation of state and the transport properties of nuclear matter, in particular the shear viscosity coefficient, using the same dynamical model.

The liquid gas phase transition in nuclear systems is a unique phenomenon, at the frontier of nuclear, many-body and statistical physics. We use self-consistent mean-field calculations to quantify the properties of the transition in symmetric nuclear matter. We explore the available parameter space of critical properties by analyzing the mean-field dependence of the phase transition. The latent heat of the transition is computed and we find that it exhibits a model independent temperature dependence due to basic physical principles.