F. Gulminelli

Publications (112)62.82 Total impact

• Article: Densities and energies of nuclei in dilute matter

  P. Papakonstantinou, J. Margueron, F. Gulminelli, Ad. R. Raduta
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  ABSTRACT: 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 profiles in spherical symmetry in terms of basic properties of the energy density functionals used and propose an analytical, Woods-Saxon density profile whose parameters depend, not only on the composition of the cluster, but also of the nucleon gas. We study the clusters' energies with the help of the local-density approximation, validated through our microscopic results. We find that the volume energies of coordinate-space clusters are determined by the saturation properties of matter, while the surface energies are strongly affected by the presence of the gas. We conclude that both the density profiles and the cluster energies are strongly affected by the gas and discuss implications for the nuclear EoS and related perspectives. Our study provides a simple, but microscopically motivated modeling of the energetics of clusterized matter at subsaturation densities, for direct use in consequential applications of astrophysical interest.
  05/2013;
• Article: Some aspects of the phase diagram of nuclear matter relevant to compact stars

  F. Gulminelli, Ad-R. Raduta, J. Margueron, P. Papakonstantinou, M. Oertel
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  ABSTRACT: 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 of neutron stars. In this paper we will address the specific phenomenology of two of such transitions, namely the crust-core solid-liquid transition at sub-saturation density, and the possible strange transition at super-saturation density in the presence of hyperonic degrees of freedom. Concerning the neutron star crust-core phase transition at zero and finite temperature, it will be shown that, as a consequence of the presence of long-range Coulomb interactions, a clusterized phase is expected which is not accessible in the grand-canonical ensemble. A specific quasi-particle model will be introduced and some quantitative results relevant for the supernova dynamics will be shown. The opening of hyperonic degrees of freedom at higher densities corresponding to the neutron stars core also modifies the equation of state. The general characteristics and order of phase transitions in this regime will be analyzed in the framework of a self-consistent mean-field approach.
  02/2013;
• Article: \alpha-clustering effects in dissipative 12C+12C reactions at 95 MeV

  G. Baiocco, L. Morelli, F. Gulminelli, M. D'Agostino, M. Bruno, U. Abbondanno, S. Barlini, M. Bini, S. Carboni, G. Casini, M. Cinausero, M. Degerlier F. Gramegna, V. L. Kravchuk, T. Marchi, A. Olmi, G. Pasquali, S. Piantelli, Ad. R. Raduta
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  ABSTRACT: 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 as to extract information on the isotopic distribution of the evaporation residues in coincidence with their complete evaporation chain. Residual deviations from a statistical behaviour are observed in \alpha yields and attributed to the persistence of cluster correlations well above the 24Mg threshold for 6 \alpha's decay.
  01/2013;
• Article: Strangeness-driven phase transition in (proto)- neutron star matter

  F. Gulminelli, Ad. R. Raduta, M. Oertel, J. Margueron
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  ABSTRACT: 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 strongly affected by the electromagnetic interaction, while it is almost independent of the electric charge at supra-saturation density. As a consequence, stellar matter under the condition of strangeness equilibrium is expected to experience a first as well as a second-order strangeness-driven phase transition at high density, while the liquid-gas phase transition is expected to be quenched. An RPA calculation indicates that the presence of this critical point might have sizable implications for the neutrino propagation in core-collapse supernovae.
  01/2013;
• Article: Phase diagram of neutron-rich nuclear matter and its impact on astrophysics

  F. Gulminelli, Ad. R. Raduta, J. Margueron, P. Papakonstantinou, M. Oertel
  [show abstract] [hide abstract]
  ABSTRACT: 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 neutron stars. In this paper we will address the specific phenomenology of two of such transitions, namely the crust-core solid-liquid transition at sub-saturation density, and the possible strange transition at super-saturation density in the presence of hyperonic degrees of freedom. Concerning the neutron star crust-core phase transition at zero and finite temperature, 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 clusterized phase is expected which is not accessible in the grand-canonical ensemble. A specific quasi-particle model will be introduced to illustrate this anomalous thermodynamics and some quantitative results relevant for the supernova dynamics will be shown. The opening of hyperonic degrees of freedom at higher densities corresponding to the neutron stars core modifies the equation of state. The general characteristics and order of phase transitions in this regime will be analyzed in the framework of a self-consistent mean-field approach.
  09/2012;
• Article: Phase transition toward strange matter

  F. Gulminelli, Ad. R. Raduta, M. Oertel
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  ABSTRACT: The phase diagram of a system constituted of neutrons and Λ 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 attractive and repulsive couplings, the existence of phase transitions involving strangeness appears independent of the specific interaction model. In addition we will show under which conditions a phase transition towards strange matter at high density exists, which is expected to persist even within a complete treatment including all the different strange and nonstrange baryon states. The impact of this transition on the composition of matter in the inner core of neutron stars is discussed.
  Phys. Rev. C. 08/2012; 86(2).
• Article: Phase transition towards strange matter

  F. Gulminelli, Ad. R. Raduta, M. Oertel
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  ABSTRACT: 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 attractive and repulsive couplings, the existence of phase transitions involving strangeness appears independent of the specific interaction model. In addition we will show under which conditions a phase transition towards strange matter at high density exists, which is expected to persist even within a complete treatment including all the different strange and non- strange baryon states. The impact of this transition on the composition of matter in the inner core of neutron stars is discussed.
  06/2012;
• Article: Ensemble inequivalence in supernova matter within a simple model

  F. Gulminelli, Ad. R. Raduta
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  ABSTRACT: 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 not observed in the canonical ensemble. Similarly to other model systems studied in condensed matter physics, this ensemble inequivalence is accompanied by negative susceptibility and discontinuities in the intensive observables conjugated to the order parameter. This peculiar behavior originates from the fact that baryonic matter is subject to attractive short-range strong forces as well as repulsive long-range electromagnetic interactions, partially screened by a background of electrons. As such, it is expected in any theoretical treatment of nuclear matter in the stellar environment. Consequences for the phenomenology of supernova dynamics are drawn.
  Phys. Rev. C. 02/2012; 85(2).
• Source

  Available from: ArXiv

  Article: Ensemble in-equivalence in supernova matter within a simple model

  F. Gulminelli, Ad. R. Raduta
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  ABSTRACT: 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 grandcanonical ensemble which is not observed in the canonical ensemble. Similar to other model systems studied in condensed matter physics, this ensemble in-equivalence is accompanied by negative susceptibility and discontinuities in the intensive observables conjugated to the order parameter. This peculiar behavior originates from the fact that baryonic matter is subject to attractive short range strong forces as well as repulsive long range electromagnetic interactions, partially screened by a background of electrons. As such, it is expected in any theoretical treatment of nuclear matter in the stellar environment. Consequences for the phenomenology of supernova dynamics are drawn.
  10/2011;
• Source

  Available from: ArXiv

  Article: Statistical description of complex nuclear phases in supernovae and proto-neutron stars

  Ad. R. Raduta, F. Gulminelli
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  ABSTRACT: 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 from about $\rho>10^8$ g $\cdot$ cm$^{-3}$ to normal nuclear density, temperatures between 1 and 20 MeV and proton fractions between 0.5 and 0, make it suitable for the description of baryonic matter produced in supernovae explosions and proto-neutron stars. The first finding is that, contrary to the common belief, the crust-core transition is not first order, and for all subsaturation densities matter can be viewed as a continuous fluid mixture between free nucleons and massive nuclei. As a consequence, the equations of state and the associated observables do not present any discontinuity over the whole thermodynamic range. We further investigate the nuclear matter composition over a wide range of densities and temperatures. At high density and temperature our model accounts for a much larger mass fraction bound in medium nuclei with respect to traditional approaches as Lattimer-Swesty, with sizeable consequences on the thermodynamic quantities. The equations of state agree well with the presently used EOS only at low temperatures and in the homogeneous matter phase, while important differences are present in the crust-core transition region. The correlation among the composition of baryonic matter and neutrino opacity is finally discussed, and we show that the two problems can be effectively decoupled. Comment: 36 pages, 21 figures
  09/2010;
• Source

  Available from: ArXiv

  Article: Monopole oscillations in light nuclei with a molecular dynamics approach

  T. Furuta, K. H. O. Hasnaoui, F. Gulminelli, C. Leclercq, A. Ono
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  ABSTRACT: Collective monopole vibrations are studied in the framework of an antisymmetrized version of molecular dynamics as a function of the vibration amplitude. The giant monopole resonance energy in ${}^{40}Ca$ is sensitive to the incompressibility of the effective interaction, in good agreement with complete time-dependent Hartree-Fock calculations. The collective response of ${}^{12}C$, ${}^{16}O$ and ${}^{24}Mg$ is also studied. For these lighter nuclei that have an important contribution of an $\alpha$-clustered component, different frequencies are observed, corresponding to two different types of vibrations associated with breathing and moving of the underlying clusters. Possible connections with direct breakup into $\alpha$ clusters at high excitation energy are discussed. Comment: 10 pages, 8 figures
  06/2010;
• Source

  Available from: Abdou Chbihi

  Article: The prominent role of the heaviest fragment in multifragmentation and phase transition for hot nuclei

  Bernard Borderie, E. Bonnet, N. Le Neindre, S. Piantelli, Ad. R. Raduta, M. F. Rivet, E. Galichet, F. Gulminelli, D. Mercier, B. Tamain, [......], A. Chbihi, J. P. Wieleczko, D. Guinet, P. Lautesse, F. Gagnon-Moisan, R Roy, M. Vigilante, E. Rosato, R. Dayras, J. Lukasik
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  ABSTRACT: The role played by the heaviest fragment in partitions of multifragmenting hot nuclei is emphasized. Its size/charge distribution (mean value, fluctuations and shape) gives information on properties of fragmenting nuclei and on the associated phase transition.
  03/2010;
• Source

  Available from: Abdou Chbihi

  Article: Multifragmentation and phase transition for hot nuclei

  Bernard Borderie, E. Bonnet, F. Gulminelli, N. Le Neindre, D. Mercier, S. Piantelli, M. F. Rivet, R. Bougault, A. Chbihi, J. D. Frankland, [......], E. Galichet, D. Guinet, P. Lautesse, J. Lukasik, M. Parlog, E. Rosato, R Roy, B. Tamain, M. Vigilante, J. P. Wieleczko
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  ABSTRACT: Recent important progress on the knowledge of multifragmentation and phase transition for hot nuclei, thanks to the high detection quality of the INDRA array, is reported. It concerns i) the radial collective energies involved in hot fragmenting nuclei/sources produced in central and semi- peripheral collisions and their influence on the observed fragment partitions, ii) a better knowledge of freeze-out properties obtained by means of a simulation based on all the available experimental information and iii) the quantitative study of the bimodal behaviour of the heaviest fragment distribution for fragmenting hot heavy quasi-projectiles which allows the extraction, for the first time, of an estimate of the latent heat of the phase transition. Comment: 5 pages, Proceedings of NN2009, August 17-21, Beijing (China)
  03/2010;
• Source

  Available from: ArXiv

  Article: Advancement in the understanding of multifragmentation and phase transition for hot nuclei

  Bernard Borderie, E. Bonnet, F. Gulminelli, N. Le Neindre, D. Mercier, S. Piantelli, Ad. R. Raduta, M. F. Rivet
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  ABSTRACT: 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 knowledge of freeze-out properties obtained by means of a simulation based on all the available experimental information and iii) the quantitative study of the bimodal behaviour of the heaviest fragment charge distribution for fragmenting hot heavy quasi-projectiles which allows, for the first time, to estimate the latent heat of the phase transition. Comment: 9 pages, Proceedings of IWM09, November 4-7, Catania (Italy)
  03/2010;
• Article: Multifragmentation and phase transition for hot nuclei: recent progress

  B. Borderie, E. Bonnet, F. Gulminelli, N. Le Neindre, D. Mercier, S. Piantelli, Ad.R. Raduta, M.F. Rivet, B. Tamain, R. Bougault, [......], E. Galichet, F. Gagnon-Moisan, D. Guinet, P. Lautesse, J. Lukasik, M. Pârlog, E. Rosato, R. Roy, M. Vigilante, J.P. Wieleczko
  Nuclear Physics A 03/2010; 834:535. · 1.54 Impact Factor
• Source

  Available from: Paolo Napolitani

  Article: Probing the nuclear equation of state in heavy-ion collisions at Fermi energy in isospin-sensitive exclusive experiments

  P. Napolitani, M Colonna, F. Gulminelli, E. Galichet, S. Piantelli, G. Verde, E. Vient
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  ABSTRACT: We propose a few selected experimental approaches to show that new-generation instruments can give a direct access to significant observables on the density dependence of the symmetry energy in the nuclear equation of state. The form of such dependence is investigated within the Stochastic Mean Field model, coupled to a secondary-decay treatment. Comment: 12 pages, 11 figures
  12/2009;
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  Available from: J. Lukasik

  Article: Bimodal behavior of the heaviest fragment distribution in projectile fragmentation.

  E Bonnet, D Mercier, B Borderie, F Gulminelli, M F Rivet, B Tamain, R Bougault, A Chbihi, R Dayras, J D Frankland, [......], D Guinet, P Lautesse, J Lukasik, N Le Neindre, M Pârlog, E Rosato, R Roy, M Vigilante, J P Wieleczko, B Zwieglinski
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  ABSTRACT: The charge distribution of the heaviest fragment detected in the decay of quasiprojectiles produced in intermediate energy heavy-ion collisions has been observed to be bimodal. This feature is expected as a generic signal of phase transition in nonextensive systems. In this Letter, we present new analyses of experimental data from Au on Au collisions at 60, 80, and 100 MeV/nucleon showing that bimodality is largely independent of the data selection procedure and of entrance channel effects. An estimate of the latent heat of the transition is extracted.
  Physical Review Letters 08/2009; 103(7):072701. · 7.37 Impact Factor
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  Available from: ArXiv

  Article: Thermodynamics of clusterized matter

  Ad. R. Raduta, F. Gulminelli
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  ABSTRACT: Thermodynamics of clusterized matter is studied in the framework of statistical models with non-interacting cluster degrees of freedom. At variance with the analytical Fisher model, exact Metropolis simulation results indicate that the transition from homogeneous to clusterized matter lies along the $\rho=\rho_0$ axis at all temperatures and the limiting point of the phase diagram is not a critical point even if the surface energy vanishes at this point. Sensitivity of the inferred phase diagram to the employed statistical framework in the case of finite systems is discussed by considering the grand-canonical and constant-pressure canonical ensembles. A Wigner-Seitz formalism in which the fragment charge is neutralized by an uniform electron distribution allows to build the phase diagram of neutron star matter. Comment: 18 pages, 9 figures
  02/2009;
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  Available from: ArXiv

  Article: Fermionic Molecular Dynamics for nuclear dynamics and thermodynamics

  K. H. O. Hasnaoui, Ph. Chomaz, F. Gulminelli
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  ABSTRACT: A new Fermionic Molecular Dynamics (FMD) model based on a Skyrme functional is proposed in this paper. After introducing the basic formalism, some first applications to nuclear structure and nuclear thermodynamics are presented Comment: 5 pages, Proceedings of the French-Japanese Symposium, September 2008. To be published in Int. J. of Mod. Phys. E
  12/2008;
• Article: Expansion dynamics of Lennard-Jones systems.

  M J Ison, F Gulminelli, C O Dorso
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  ABSTRACT: The dynamics of the expansion of a Lennard-Jones system, initially confined at high density and subsequently expanding freely in a vacuum, is compared with an expanding statistical ensemble derived in the diluted quasi-ideal Boltzmann approximation. The description proves to be fairly accurate at predicting average one-body global observables, but important deviations are observed in the configuration-space structure of the events. Possible implications for finite expanding physical systems are outlined.
  Physical Review E 04/2008; 77(3 Pt 1):031109. · 2.26 Impact Factor