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Paper   IPM / P / 6773
School of Physics
  Title:   The ∆ (1232) Isobar Probability in Frozen and Hot Neutron, Nuclear ABD β-Stable Matter
1.  H.R. Moshfegh
2.  M. Modarres
  Status:   Published
  Journal: Prog. Theor. Phys.
  No.:  1
  Vol.:  107
  Year:  2002
  Pages:   139-150
  Supported by:  IPM
In this article we calculate the probabilty of having ∆(1232) resonance in frozen and hot neutron, nuclear and ?-stable matter. We use the temperature dependence correlation functions that are generated through a lowest order constrained variational calculation with the ∆−Reid potential. The NNN∆ transition is built in through a two-pion exchange interaction. The electrons and muons are treated relativistically in the total Hamiltonian at given temperature and density, in order to make the fluid electrically neutral and stable with respect to β−decay. We ignore the weak interaction. It is seen that the ∆ probability in neutron matter is much larger than in nuclear and β−stable matter at a given temperature and density. As we increase the temperature, the ∆ probability decreases in nuclear and neutron matter. However, this decrease is not significant in case of β−stable nuclear matter. There is overall agreement between our ∆ probability calculation and the recent experiments performed on 3He up to 208Pb nuclei. It is concluded that the isobar degrees of freedom could make the equation of state of neutron star matter harder at finite temperature and suppress the numbers of protons and leptons in the proto-neutron stars.

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