Replicated theoretical attempts of relativistic approaches to the pionself-energy in nuclear matter yield unphysical pion spectra. We demonstrate thecrucial dependence of the calculated pion spectra on the correct relativisticaccounting for the short-range correlation effects on the pion self-energy inthe medium. To do this, we simulate the short-range interactions byphenomenological contact terms in the relativistic Lagrangian density, andderive the pion self-energy by carefully taking into account the relativistickinematics. The obtained spectrum for the pion-like excitations in cold nuclearmatter shows physically meaningful branches, in contrast to those obtainedbefore by different authors by the use of simplified relativistic approaches tothe short-range correlations.
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