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Turnu Măgurele, Romania

Gulminelli F.,French National Center for Scientific Research | Gulminelli F.,National Engineering School of Caen | Raduta A.R.,IFIN HH | Oertel M.,University Paris Diderot
Physical Review C - Nuclear Physics | Year: 2012

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. © 2012 American Physical Society.


Cozma M.D.,IFIN HH | Leifels Y.,Helmholtz Center for Heavy Ion Research | Trautmann W.,Helmholtz Center for Heavy Ion Research | Li Q.,Huzhou Teachers College | Russotto P.,National Institute of Nuclear Physics, Italy
Physical Review C - Nuclear Physics | Year: 2013

Neutron-proton elliptic flow difference and ratio have been shown to be promising observables in the attempt to constrain the density dependence of the symmetry energy above the saturation point from heavy-ion collision data. Their dependence on model parameters such as microscopic nucleon-nucleon cross sections, compressibility of nuclear matter, optical potential, and symmetry energy parametrization is thoroughly studied. By using a parametrization of the symmetry energy derived from the momentum-dependent Gogny force in conjunction with the Tübingen quantum molecular dynamics (QMD) model and comparing the results with the experimental FOPI-LAND data for 197Au +197Au collisions at 400 MeV/nucleon, a moderately stiff (Lsym=122±57 MeV and K sym=229±363 MeV) symmetry energy is extracted, a result that agrees with that of a similar study that employed the UrQMD transport model and a power-law parametrization of the symmetry energy. This contrasts with diverging results extracted from the FOPI π-/π+ ratio available in the literature. © 2013 American Physical Society.


Barsan V.,IFIN HH
Philosophical Magazine | Year: 2014

The eigenvalue equations for the energy of bound states of a particle in a square well are solved, and the exact solutions are obtained, as power series. Accurate analytical approximate solutions are also given. The application of these results in the physics of quantum wells are discussed, especially for ultra-thin metallic films, but also in the case of resonant cavities, heterojunction lasers, revivals and super-revivals. © 2013 Taylor & Francis.


The statistical mechanics of one- and two-dimensional Ginzburg-Landau systems is evaluated analytically, via the transfer matrix method, using an expression of the ground state energy of the quartic anharmonic oscillator in an external field. In the two-dimensional case, the critical temperature of the order-disorder phase transition is expressed as a Lambert function of the inverse inter-chain coupling constant. © 2010 2011 Taylor & Francis.


Cozma M.D.,IFIN HH
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

We employ an isospin dependent version of the QMD transport model to study the influence of the isospin dependent part of the nuclear matter equation of state and in-medium nucleon-nucleon cross-sections on the dynamics of heavy-ion collisions at intermediate energies. We find that the extraction of useful information on the isospin-dependent part of the equation of state of nuclear matter from proton or neutron elliptic flows is obstructed by their sensitivity to model parameters and in-medium values of nucleon-nucleon cross-sections. Opposite to that, neutron-proton elliptic flow difference shows little dependence on those variables while its dependence on the isospin asymmetric EoS is enhanced, making it more suitable for a model independent constraining of the high-density behaviour of asy-EoS. Comparison with existing experimental FOPI-LAND neutron-hydrogen data can be used to set an upper limit to the softness of asy-EoS. Successful constraining of the asy-EoS via neutron-proton elliptic flow difference will require experimental data of higher accuracy than presently available. © 2011 Elsevier B.V.

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