Nuclear structure in the DiracHartreeFockBogoliubov approximation and the struc...
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Author(s): 
Total Authors: 3

Affiliation:  ^{[1]} Univ Fed Rio Grande do Norte, Escola Ciencias & Tecnol, BR59078970 Natal, RN  Brazil
^{[2]} Ctr Tecn Aeroesp, Inst Technol Aeronaut, Dept Fis, BR12228900 Sao Jose Dos Campos, SP  Brazil
Total Affiliations: 2

Document type:  Journal article 
Source:  Physical Review C; v. 93, n. 2 FEB 25 2016. 
Web of Science Citations:  11 
Abstract  
Background: Unbound singleparticle states become important in determining the properties of a hot nucleus as its temperature increases. We present relativistic mean field (RMF) for hot nuclei considering not only the selfconsistent temperature and density dependence of the selfconsistent relativistic mean fields but also the vapor phase that takes into account the unbound nucleon states. Purpose: The temperature dependence of the pairing gaps, nuclear deformation, radii, binding energies, entropy, and caloric curves of spherical and deformed nuclei are obtained in selfconsistent RMF calculations up to the limit of existence of the nucleus. Method: We perform DiracHartreeBogoliubov (DHB) calculations for hot nuclei using a zerorange approximation to the relativistic pairing interaction to calculate protonproton and neutronneutron pairing energies and gaps. A vapor subtraction procedure is used to account for unbound states and to remove long range Coulomb repulsion between the hot nucleus and the gas as well as the contribution of the external nucleon gas. Results: We show that pp and nn pairing gaps in the S1(0) channel vanish for low critical temperatures in the range Tcp approximate to 0.61.1 MeV for spherical nuclei such as Zr90, Sn124, and Ce140 and for both deformed nuclei Sm150 and Er168. We found that superconducting phase transition occurs at Tcp = 1.03 Delta(pp) (0) for Zr90, Tcp = 1.16 Delta(pp) (0) for Ce140, Tcp = 0.92 Delta(pp) (0) for Sm150, and Tcp = 0.97 Delta(pp) (0) for Er168. The superfluidity phase transition occurs at Tcp = 0.72 Delta(nn) (0) for Sn124, Tcp = 1.22 Delta(nn) (0) for Sm150, and Tcp = 1.13 Delta(nn) (0) for Er168. Thus, the nuclear superfluidity phaseat least for this channelcan only survive at very low nuclear temperatures and this phase transition (when the neutron gap vanishes) always occurs before the superconducting one, where the proton gap is zero. For deformed nuclei the nuclear deformation disappear at temperatures of about Tcs = 2.04.0 MeV, well above the critical temperatures for pairing, Tcp. If we associate the melting of hot nuclei into the surrounding vapor with the liquidgas phase transition our results indicate that it occurs at temperatures around T = 8.010.0 MeV, somewhat higher than observed in many experimental results. Conclusions: The change of the pairing fields with the temperature is important and must be taken into account in order to define the superfluidity and superconducting phase transitions. We obtain a Hamiltonian form of the pairing field calibrated by an overall constant c(pair) to compensate for deficiencies of the interaction parameters and of the numerical calculation. When the pairing is not zero, the states close to the Fermi energy make the principal contribution to the anomalous density that appears in the pairing field. By including temperature through the use of the Matsubara formalism, the normal and anomalous densities are multiplied by a Fermi occupation factor. This leads to a reduction in the anomalous density and in the pairing as the temperature increases. When the temperature increases (T >= 4 MeV), the effects of the vapor phase that take into account the unbound nucleon states become important, allowing the study of nuclear properties of finite nuclei from zero to high temperatures. (AU)  
FAPESP's process:  13/262584  Superdense matter in the universe 
Grantee:  Manuel Máximo Bastos Malheiro de Oliveira 
Support type:  Research Projects  Thematic Grants 
FAPESP's process:  09/000695  Fewbody aspects of manybody physics 
Grantee:  Tobias Frederico 
Support type:  Research Projects  Thematic Grants 