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Accueil > Recherche > Physique Théorique et Phénoménologie

Publications

(more recent)

[in2p3-01301864] Neutron star radii and crusts: uncertainties and unified equations of state

6 octobre 2016

The uncertainties in neutron star (NS) radii and crust properties due to our limited knowledge of the equation of state (EOS) are quantitatively analysed. We first demonstrate the importance of a unified microscopic description for the different baryonic densities of the star. If the pressure (...)

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[in2p3-01348905] A constrained-path quantum Monte-Carlo approach for the nuclear shell model

30 juillet 2016

A new QMC approach for the shell model yielding nearly exact spectroscopy of nuclei is presented. The originality of the formalism lies in the use of a variational symmetry-restored wave function to ‘steer’ the Brownian motion, and to control the sign/phase problem that generally makes the (...)

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[in2p3-01340233] Clustering effects in fusion evaporation reactions with light even-even N=Z nuclei. The 24 Mg and 28 Si cases

2 juillet 2016

In the recent years, cluster structures have been evidenced in many ground and excited states of light nuclei [1, 2]. The decay of highly excited states of 24 Mg is studied in fusion evaporation events completely detected in charge in the reactions 12 C+ 12 C and 14 N+ 10 B at 95 and 80 MeV (...)

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[in2p3-01340539] Impact of pairing on thermodynamical properties of stellar matter

2 juillet 2016

Superfluidity in the crust is a key ingredient for the cooling properties of proto-neutron stars. Investigations on crust superfluidity carried out so far typically assumed that the cluster component was given by a single representative nucleus and did not consider the fact that at finite (...)

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[in2p3-01334165] Constrained-path quantum Monte Carlo approach for non-yrast states within the shell model

21 juin 2016

The present paper intends to present an extension of the constrained-path quantum Monte Carlo approach allowing to reconstruct non-yrast states in order to reach the complete spectroscopy of nuclei within the interacting shell model. As in the yrast case studied in a previous work, the (...)

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[in2p3-01269560] Hyperons in neutron stars and supernova cores

21 avril 2016

The properties of compact stars and their formation processes depend on many physical ingredients. The composition and the thermodynamics of the involved matter is one of them. We will investigate here uniform strongly interacting matter at densities and temperatures, where potentially other (...)

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[in2p3-01293418] The 12C* Hoyle state in the inelastic 12C + 12C reaction and in 24Mg* decay

26 mars 2016

The reaction 12C + 12C at 95 MeV has been studied at the Legnaro Laboratories of INFN with the GARFIELD + RCo apparatus. Data have been analyzed in order to investigate the decay of the Hoyle state of 12C*. Two different data selections have been made. The first one corresponds to peripheral (...)

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[in2p3-01275770] Analytical mass formula and nuclear surface properties in the ETF approximation. Part I: symmetric nuclei

19 février 2016

The problem of the determination of the nuclear surface and surface symmetry energy is addressed in the framework of the Extended Thomas Fermi (ETF) approximation using Skyrme functionals. We propose an analytical model for the density profiles with variationally determined diffuseness (...)

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[in2p3-01213940] Liquid-gas phase transition in strange hadronic matter with relativistic models

16 février 2016

Background: The advent of new dedicated experimental programs on hyperon physics is rapidly boosting the field, and the possibility of synthetizing multiple strange hypernuclei requires the addition of the strangeness degree of freedom to the models dedicated to nuclear structure and nuclear (...)

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[in2p3-01226400] Modification of magicity toward the dripline and its impact on electron-capture rates for stellar core collapse

16 février 2016

The importance of microphysical inputs from laboratory nuclear experiments and theoretical nuclear structure calculations in the understanding of the core collapse dynamics, and the subsequent supernova explosion, is largely recognized in the recent literature. In this work, we analyze the (...)

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[in2p3-01243596] Finite-size effects on the phase diagram of the thermodynamical cluster model

16 décembre 2015

The thermodynamical cluster model is known to present a first-order liquid-gas phase transition in the idealized case of an uncharged, infinitely extended medium. However, in most practical applications of this model, the system is finite and charged. In this paper we study how the phase (...)

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[in2p3-01244049] Hyperons in neutron star matter within relativistic mean-field models

16 décembre 2015

Since the discovery of neutron stars with masses around 2M ⊙ the composition of matter in the central part of these massive stars has been intensively discussed. Within this paper we will (re)investigate the question of the appearance of hyperons. To that end we will perform parameter study (...)

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[in2p3-01232713] Impact of pairing effects on thermodynamical properties and clusterization of stellar matter

25 novembre 2015

Superfluidity in the crust is a key ingredient for the cooling properties of proto-neutron stars. Investigations on crust superfluidity carried out so far typically assumed that the cluster component was given by a single representative nucleus and did not consider the fact that at finite (...)

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[in2p3-01163153] Unified treatment of subsaturation stellar matter at zero and finite temperature

24 novembre 2015

The standard variational derivation of stellar matter structure in the Wigner-Seitz approximation is generalized to the finite temperature situation where a wide distribution of different nuclear species can coexist in the same density and proton fraction condition, possibly out of (...)

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[in2p3-01226404] Heat capacity of the neutron star inner crust within an extended nuclear statistical equilibrium model

24 novembre 2015

Background: Superfluidity in the crust is a key ingredient for the cooling properties of proto-neutron stars. Present theoretical calculations employ the quasiparticle mean-field Hartree-Fock-Bogoliubov theory with temperature-dependent occupation numbers for the quasiparticle states. Purpose: (...)

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[in2p3-01226419] Clustering effects in fusion evaporation reactions with light even-even N = Z nuclei. The 24Mg and 28Si cases

10 novembre 2015

In the recent years, cluster structures have been evidenced in many ground and excited states of light nuclei [1, 2]. Within the currently ongoing experimental campaign by the NUCL-EX collaboration we have measured the 12C+12C and 14N+10B reactions at 95 MeV and 80 MeV respectively, and (...)

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[in2p3-01226192] Intertwined orders from symmetry projected wavefunctions of repulsively interacting Fermi gases in optical lattices

10 novembre 2015

Unconventional strongly correlated phases of the repulsive Fermi-Hubbard model, which could be emulated by ultracold vapors loaded in optical lattices, are investigated by means of energy minimizations with quantum number projection before variation and without any assumed order parameter. In a (...)

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[in2p3-01158954] Microscopic evaluation of the hypernuclear chart with $\Lambda$ hyperons

28 octobre 2015

We calculate the comprehensive hypernuclear chart for even-even hypernuclei with magic numbers of $\Lambda$'s (for Z $\leq$ 120 and $\Lambda \leq$70) and estimate the number of bound systems, considering the present uncertainties in the $\Lambda-$nucleon and $\Lambda-\Lambda$ interactions. We (...)

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[in2p3-01188824] Cluster correlation effects in $^{12}C$+$^{12}C$ and $^{14}N$+$^{10}B$ fusion-evaporation reactions

1er septembre 2015

The decay of highly excited states of 24Mg is studied in fusion evaporation events completely detected in charge in the reactions 12C+12C and 14N+10B at 95 and 80 MeV incident energy respectively. The comparison of light charged particles measured spectra with statistical model predictions (...)

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[in2p3-01102611] Hyperons in neutron star matter within relativistic mean-field models

22 juillet 2015

Since the discovery of neutron stars with masses around 2 solar masses the composition of matter in the central part of these massive stars has been intensively discussed. Within this paper we will (re)investigate the question of the appearance of hyperons. To that end we will perform an (...)

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[in2p3-01171365] From Light to Heavy Nuclear Systems, Production and Decay of Fragments Studied with Powerful Arrays

4 juillet 2015

Reactions between heavy-ions at various energy regimes produce many nuclear fragments which can be populated in highly excited states. The study of these fragments, detected at the end of their particle decay, is important to investigate nuclear forces and structure effects. In recent years (...)

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[in2p3-01133570] Thermal properties of light nuclei from $^{12}$C+$^{12}$C fusion-evaporation reactions

2 juillet 2015

The $^12$C+$^12$C reaction at 95 MeV has been studied through the complete charge identification of its products by means of the GARFIELD+RCo experimental set-up at INFN Laboratori Nazionali di Legnaro (LNL). In this paper, the first of a series of two, a comparison to a dedicated (...)

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[in2p3-01089721] Equations of state and phase transitions in stellar matter

1er juillet 2015

Realistic description of core-collapsing supernovae evolution and structure of proto-neutron stars chiefly depends on microphysics input in terms of equations of state, chemical composition and weak interaction rates. At sub-saturation densities the main uncertainty comes from the symmetry (...)

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[in2p3-00839915] Equivalence between fractional exclusion statistics and Fermi liquid theory in interacting particle systems

1er juillet 2015

We explore the connections between the description of interacting particles systems in terms of fractional exclusion statistics (FES) and other many-body methods used for the same purpose. We consider a system of particles with generic, particle-particle interaction in the quasi-classical limit (...)

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[in2p3-00805497] Exotic spin, charge and pairing correlations of the two-dimensional doped Hubbard model: a symmetry entangled mean-field approach

1er juillet 2015

Intertwining of spin, charge and pairing correlations in the repulsive two-dimensional Hubbard model is shown through unrestricted variational calculations, with projected wavefunctions free of symmetry breaking. A crossover from incommensurate antiferromagnetism to stripe order naturally (...)

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[in2p3-00674988] Ensemble inequivalence in supernova matter within a simple model

1er juillet 2015

A simple, exactly solvable statistical model is presented for the description of baryonic matter in the thermodynamic conditions associated to the evolution of core-collapsing supernova. It is shown that the model presents a first-order phase transition in the grand-canonical ensemble which is (...)

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[in2p3-00606217] Reaction mechanisms and staggering in S+Ni collisions

1er juillet 2015

The reactions 32S + 58Ni and 32S + 64Ni are studied at 14.5 A MeV. After a selection of the collision mechanism, we show that important even-odd effects are present in the isotopic fragment distributions when the excitation energy is small. Close to the multifragmentation threshold this (...)

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[in2p3-00492917] Phase diagram of the charged lattice-gas model with two types of particles

1er juillet 2015

A lattice-gas model with two types of particles, a particle-dependent short-range coupling and a long-range repulsive Coulombic interaction, is introduced. The phase diagram of an isolated finite system of 129 particles is constructed using the bimodality properties of the observables' (...)

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[in2p3-00857483] Probing the statistical decay and alpha-clustering effects in 12c+12c and 14n+10b reactions

1er juillet 2015

An experimental campaign has been undertaken at INFN Laboratori Nazionali di Legnaro, Italy, in order to progress in our understanding of the statistical properties of light nuclei at excitation energies above particle emission threshold, by measuring exclusive data from fusion-evaporation (...)

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[in2p3-00730949] Fragmentation and clustering in star matter

1er juillet 2015

The specificity of the crust-core phase transition in neutron star at zero and finite temperature will be discussed. It will be shown that, as a consequence of the presence of long range Coulomb interactions, the equivalence of statistical ensembles is violated and a clusterised phase is (...)

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[in2p3-00730980] Statistical (?) decay of light hot nuclei

1er juillet 2015

The reaction 12C+12C at 95 MeV beam energy has been measured using the GARFIELD+RCo apparatuses at Laboratori Nazionali di Legnaro LNL - INFN, Italy, in the framework of an experimental campaign proposed by the NUCL-EX collaboration. The aim is to progress in the understanding of statistical (...)

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[in2p3-00730939] An interpretation of staggering effects by correlation observables

1er juillet 2015

The reactions 32S+58,64Ni are studied at 14.5 A MeV. Evidence is found for odd-even effects in isotopic observables of the decay of a projectile-like source. The influence of secondary decays on the staggering is studied with a correlation function technique, showing that odd-even effects are (...)

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[in2p3-00805495] A Constrained-Path Quantum Monte-Carlo Approach for the Nuclear Shell Model

1er juillet 2015

A new Quantum Monte-Carlo (QMC) approach is proposed to investigate low-lying states of nuclei within the shell model. The formalism relies on a variational symmetry-restored wave-function to guide the underlying Brownian motion. Sign/phase problems that usually plague QMC fermionic simulations (...)

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[in2p3-00782412] Neutron-rich nuclei and the equation of state of stellar matter

1er juillet 2015

In this contribution we will review our present understanding of the matter equation of state in the density and temperature conditions where it can be described by nucleonic degrees of freedom. At zero temperature, all the information is contained in the nuclear energy functional in its (...)

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[in2p3-00848371] A phase-free quantum Monte Carlo method for the nuclear shell model

1er juillet 2015

The shell model provides a powerful framework for nuclear structure calculations. The nucleons beyond an inert magic core are confined in a valence shell and interact through an effective two-body potential generally determined from the G-matrix method. However, the applicability of the shell (...)

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[in2p3-00691845] Towards an understanding of staggering effects in dissipative binary collisions

1er juillet 2015

The reactions S32+58,64Ni are studied at 14.5 A MeV. Evidence is found for important odd-even effects in isotopic observables of selected peripheral collisions corresponding to the decay of a projectile-like source. The influence of secondary decays on the staggering is studied with a (...)

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[in2p3-01073837] Strongly correlated electron systems

1er juillet 2015

The quantum phase diagram of the two-dimensional Hubbard model is investigated through the mixing of unrestricted Hartree-Fock and BCS wave-functions with symmetry restoration before variation. The spin, charge, and superconducting orders entailed in such correlated states will be discussed as (...)

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[in2p3-01023922] Sub-saturation matter in compact stars: Nuclear modelling in the framework of the extended Thomas-Fermi theory

1er juillet 2015

A recently introduced analytical model for the nuclear density profile [1] is implemented in the Extended ThomasFermi (ETF) energy density functional. This allows to (i) shed a new light on the issue of the sign of surface symmetry energy in nuclear mass formulas, as well as to (ii) show the (...)

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[in2p3-01163166] Strangeness driven phase transitions in compressed baryonic matter and their relevance for neutron stars and core collapsing supernovae

1er juillet 2015

We discuss the thermodynamics of compressed baryonic matter with strangeness within non-relativistic mean-field models with effective interactions. The phase diagram of the full baryonic octet under strangeness equilibrium is built and discussed in connection with its relevance for (...)

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[in2p3-00824193] Densities and energies of nuclei in dilute matter at zero temperature

1er juillet 2015

We explore the ground-state properties of nuclear clusters embedded in a gas of nucleons with the help of Skyrme-Hartree-Fock microscopic calculations. Two alternative representations of clusters are introduced, namely coordinate-space and energy-space clusters. We parameterize their density (...)

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[in2p3-00539882] Statistical description of complex nuclear phases in supernovae and proto-neutron stars

1er juillet 2015

We develop a phenomenological statistical model for dilute star matter at finite temperature, in which free nucleons are treated within a mean-field approximation and nuclei are considered to form a loosely interacting cluster gas. Its domain of applicability, that is baryonic densities ranging (...)

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[in2p3-00789040] Some aspects of the phase diagram of nuclear matter relevant to compact stars

1er juillet 2015

Dense matter as it can be found in core-collapse supernovae and neutron stars is expected to exhibit different phase transitions which impact the matter composition and the equation of state, with important consequences on the dynamics of core-collapse supernova explosion and on the structure (...)

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[in2p3-00785506] Phase transition towards strange matter

1er juillet 2015

The phase diagram of a system constituted of neutrons and $\Lambda$-hyperons in thermal equilibrium is evaluated in the mean-field approximation. It is shown that this simple system exhibits a complex phase diagram with first and second order phase transitions. Due to the generic presence of (...)

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[in2p3-00762455] Phase diagram of neutron-rich nuclear matter and its impact on astrophysics

1er juillet 2015

Dense matter as it can be found in core-collapse supernovae and neutron stars is expected to exhibit different phase transitions which impact the matter composition and equation of state, with important consequences on the dynamics of core-collapse supernova explosion and on the structure of (...)

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[hal-00461755] Advancement in the understanding of multifragmentation and phase transition for hot nuclei

1er juillet 2015

Recent advancement on the knowledge of multifragmentation and phase transition for hot nuclei is reported. It concerns i) the influence of radial collective energy on fragment partitions and the derivation of general properties of partitions in presence of such a collective energy, ii) a better (...)

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[in2p3-01109338] Exact ground state of strongly correlated electron systems from symmetry-entangled wave-functions

1er juillet 2015

The four-site Hubbard model is considered from the exact diagonalisation and variational method points of view. It is shown that the exact ground-state can be recovered by a symmetry projected Slater determinant, irrespective of the interaction strength. This is in contrast to the Gutzwiller (...)

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[in2p3-00785502] alpha-clustering effects in dissipative 12C+12C reactions at 95 MeV

1er juillet 2015

Dissipative 12C+12C reactions at 95 MeV are fully detected in charge with the GARFIELD and RCo apparatuses at LNL. A comparison to a dedicated Hauser-Feshbach calculation allows to select events which correspond, to a large extent, to the statistical evaporation of highly excited 24Mg, as well (...)

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[in2p3-00825301] Transformation between statistical ensembles in the modelling of nuclear fragmentation

1er juillet 2015

We explore the conditions under which the particle number conservation constraint deforms the predictions of fragmentation observables as calculated in the grand canonical ensemble. We derive an analytical formula allowing to extract canonical results from a grand canonical calculation and vice (...)

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[hal-00628137] Boundary conditions for star matter and other periodic fermionic systems

1er juillet 2015

Bulk fermionic matter, as it can be notably found in supernova matter and neutrons stars, is subject to correlations of infinite range due to the antisymmetrisation of the N-body wave function, which cannot be explicitly accounted for in a practical simulation. This problem is usually addressed (...)

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[in2p3-00623348] EOS and phase transition: Nuclei to stars

1er juillet 2015

In these lectures we review the present status of knowledge of the nuclear thermal as well as quantum phase transitions. Examples in nuclear physics concern in particular shape transitions, vanishing of pairing correlations at high excitation, nuclear multifragmentation as well as deconfinement (...)

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[in2p3-00730983] Staggering in S+Ni collisions

1er juillet 2015

Odd-even effects in fragment production have been studied since a long time and never quantitatively understood. The odd-even anomaly was reported in the literature [1,2] to be more pronounced in reactions involving Ni projectile and targets, in particular in n-poor systems. In some experiments (...)

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[in2p3-00454242] Probing the nuclear equation of state in heavy-ion collisions at Fermi energy in isospin-sensitive exclusive experiments

1er juillet 2015

In order to guide the study of the form of the density dependence of the symmetry energy in the nuclear equation of state, robust observables are searched within the Stochastic Mean Field model coupled to a secondary decay treatment. We propose a few selected experimental approaches to show (...)

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[hal-00974520] Non-statistical decay and $\alpha$-correlations in the $^{12}$C+$^{12}$C fusion-evaporation reaction at 95 MeV

1er juillet 2015

Multiple alpha coincidence and correlations are studied in the reaction $^12$C+$^12$C at 95 MeV for fusion-evaporation events completely detected in charge. Two specific channels with Carbon and Oxygen residues in coincidence with $\alpha$-particles are addressed, which are associated with (...)

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[in2p3-00857485] Clusterized nuclear matter in the (proto-)neutron star crust and the symmetry energy

1er juillet 2015

Though generally agreed that the symmetry energy plays a dramatic role in determining the structure of neutron stars and the evolution of core-collapsing supernovae, little is known in what concerns its value away from normal nuclear matter density and, even more important, the correct (...)

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[in2p3-00978296] In-medium nuclear cluster energies within the Extended Thomas-Fermi approach

1er juillet 2015

A recently introduced analytical model for the nuclear density profile[1] is implemented in the Extended Thomas-Fermi (ETF) energy density functional. This allows to (i) shed a new light on the issue of the sign of surface symmetry energy in nuclear mass formulas, which is strongly related to (...)

Lire la suite

[in2p3-00776595] Strangeness-driven phase transition in star matter

1er juillet 2015

The phase diagram of a system constituted of neutrons, protons, $\Lambda$-hyperons and electrons is evaluated in the mean-field approximation in the complete three-dimensional space given by the baryon, lepton and strange charge. It is shown that the phase diagram at sub-saturation densities is (...)

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[in2p3-00512379] Monopole oscillations in light nuclei with a molecular dynamics approach

1er juillet 2015

Collective monopole vibrations are studied in the framework of antisymmetrized version of molecular dynamics as a function of the vibration amplitude. The giant monopole resonance energy in $^40Ca$ is sensitive to the incompressibility of the effective interaction, in good agreement with (...)

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