Marcello Baldo

Bio: Marcello Baldo is an academic researcher from Istituto Nazionale di Fisica Nucleare. The author has contributed to research in topics: Nuclear matter & Neutron star. The author has an hindex of 37, co-authored 263 publications receiving 5366 citations. Previous affiliations of Marcello Baldo include Centra & University of Catania.

Hyperon stars in the Brueckner-Bethe-Goldstone theory

Abstract: In the framework of the Brueckner-Bethe-Goldstone theory, we determine a fully microscopic equation of state for asymmetric and $\ensuremath{\beta}$-stable nuclear matter containing ${\ensuremath{\Sigma}}^{\ensuremath{-}}$ and $\ensuremath{\Lambda}$ hyperons. We use the Paris and the new Argonne ${\mathrm{Av}}_{18}$ two-body nucleon interaction, whereas the nucleon-hyperon interaction is described by the Njimegen soft-core model. We stress the role played by the three-body nucleon interaction, which produces a strong repulsion at high densities. This enhances enormously the hyperon population, and produces a strong softening of the equation of state, which turns out almost independent on the nucleon-nucleon interaction. We use the new equation of state in order to calculate the structure of static neutron stars. We obtain a maximum mass configuration with ${M}_{\mathrm{max}}=1.26$ (1.22) when the Paris ${(Av}_{18})$ nucleon potential is adopted. Central densities are about 10 times normal nuclear matter density. Stellar rotations, treated within a perturbative approach, increase the value of the limiting mass by about 12%.

Microscopic nuclear equation of state with three-body forces and neutron star structure

Abstract: We calculate static properties of non-rotating neu- tronstars(NS's)usingamicroscopicequationofstate(EOS)for asymmetric nuclear matter, derived from the Brueckner-Bethe- Goldstone many-body theory with explicit three-body forces WeusetheArgonneAV14andtheParistwo-bodynuclearforce, implemented by the Urbana model for the three-body force We obtain a maximum mass conguration with Mmax =1 : 8 M ( Mmax =1 :94M) when the AV14 (Paris) interaction is used They are both consistent with the observed range of NS masses The onset of direct Urca processes occurs at densities n 0:65 fm 3 for the AV14 potential and n 0:54 fm 3 for the Paris potential Therefore, NS's with masses above M Urca =1 : 4 Mfor the AV14 and M Urca =1 :24M for the Paris potential can undergo very rapid cooling, depending on the strength of superfluidity in the interior of the NS The comparison with other microscopic models for the EOS shows noticeable differences

Bethe-Brueckner-Goldstone Expansion in Nuclear Matter

Abstract: The equation of state of symmetric nuclear matter at zero temperature is calculated up to the three hole-line level of approximation in the Bethe-Brueckner-Goldstone expansion. Both the standard and the continuous choices for the single particle auxiliary potential are considered. The resulting equation of state shows independence from the choice of the auxiliary potential to a high degree of accuracy. This result gives strong evidence for the convergence of the expansion and establishes the nuclear matter saturation curve for the adopted nucleon-nucleon interaction, the Argonne ${v}_{14}$ potential.

Hadron-quark phase transition in dense matter and neutron stars

Abstract: We study the hadron-quark phase transition in the interior of neutron stars (NS's). We calculate the equation of state (EOS) of hadronic matter using the Brueckner-Bethe-Goldstone formalism with realistic two-body and three-body forces, as well as a relativistic mean field model. For quark matter we employ the MIT bag model constraining the bag constant by using the indications coming from the recent experimental results obtained at the CERN SPS on the formation of a quark-gluon plasma. We find it necessary to introduce a density-dependent bag parameter and the corresponding consistent thermodynamical formalism. We calculate the structure of NS interiors with the EOS comprising both phases, and we find that the NS maximum masses fall in a relatively narrow interval, $1.4{M}_{\ensuremath{\bigodot}}l~{M}_{\mathrm{max}}l~{1.7M}_{\ensuremath{\bigodot}}.$ The precise value of the maximum mass turns out to be only weakly correlated with the value of the energy density at the assumed transition point in nearly symmetric nuclear matter.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

The Observation of Gravitational Waves from a Binary Black Hole Merger

Abstract: On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160) Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

On the theory of superconductivity

Abstract: IN two previous notes1, Prof. Max Born and I have shown that one can obtain a theory of superconductivity by taking account of the fact that the interaction of the electrons with the ionic lattice is appreciable only near the boundaries of Brillouin zones, and particularly strong near the corners of these. This leads to the criterion that the metal should be superconductive if a set of corners of a Brillouin zone is lying very near the Fermi surface, considered as a sphere, which limits the region in the momentum space completely filled with electrons.

Electronic structure calculations with dynamical mean-field theory

Abstract: We present a review of the basic ideas and techniques of the spectral density functional theory which are currently used in electronic structure calculations of strongly{correlated materials where the one{electron description breaks down. We illustrate the method with several examples where interactions play a dominant role: systems near metal{insulator transition, systems near volume collapse transition, and systems with local moments.

GW170817: Measurements of Neutron Star Radii and Equation of State.

Abstract: On 17 August 2017, the LIGO and Virgo observatories made the first direct detection of gravitational waves from the coalescence of a neutron star binary system. The detection of this gravitational-wave signal, GW170817, offers a novel opportunity to directly probe the properties of matter at the extreme conditions found in the interior of these stars. The initial, minimal-assumption analysis of the LIGO and Virgo data placed constraints on the tidal effects of the coalescing bodies, which were then translated to constraints on neutron star radii. Here, we expand upon previous analyses by working under the hypothesis that both bodies were neutron stars that are described by the same equation of state and have spins within the range observed in Galactic binary neutron stars. Our analysis employs two methods: the use of equation-of-state-insensitive relations between various macroscopic properties of the neutron stars and the use of an efficient parametrization of the defining function pðρÞ of the equation of state itself. From the LIGO and Virgo data alone and the first method, we measure the two neutron star radii as R1 ¼ 10.8 þ2.0 −1.7 km for the heavier star and R2 ¼ 10.7 þ2.1 −1.5 km for the lighter star at the 90% credible level. If we additionally require that the equation of state supports neutron stars with masses larger than 1.97 M⊙ as required from electromagnetic observations and employ the equation-of-state parametrization, we further constrain R1 ¼ 11.9 þ1.4 −1.4 km and R2 ¼ 11.9 þ1.4 −1.4 km at the 90% credible level. Finally, we obtain constraints on pðρÞ at supranuclear densities, with pressure at twice nuclear saturation density measured at 3.5 þ2.7 −1.7 × 1034 dyn cm−2 at the 90% level.