Quantum Monte Carlo Studies of Relativistic Effects in Light Nuclei

por Ana Arriaga (Universidade de Lisboa)

jueves 22 nov. 2001 12:30 → 13:30 Europe/Madrid

Sala Seminarios (Dpto. de Física Teórica (UVEG))

Relativistic effects in 3H and 4He have been studied in the context of the Relativistic Hamiltonian Dynamics. Relativistic invariance is achieved through the Poincaré group algebra, meaning that the Hamiltonian is, in leading order, a generator of this group. This condition introduces a boost interaction term, defining the first relativistic effect considered. The second one consists in the nonlocalities associated with the relativistic kinetic energy operator and with the relativistic one-pion exchange potential (OPEP). The Schrödinger equation has been solved by variational Monte Carlo methods, and results for the binding energies and the contributions of the different pieces of the Hamiltonian have been obtained. The conclusions may be summarized as: i) the nonlocalities associated with the kinetic energy and OPEP tend to cancel, being the total effect on the binding energy attractive and very small, of the order of 1%; ii) the dominant relativistic effect is, consequently, the boost interaction, whose contribution is repulsive and of the order of 5%; iii) the repulsive term of the nonrelativistic 3-body interaction has to be reduced by 37% so that the experimental triton binding energy is obtained; therefore around 1/3 of the phenomenological term of this nonrelativistic interaction accounts for relativistic effects; iv) the changes induced on the wave functions of nuclei by these relativistic effects are very small and short ranged; v) although the nonlocalities of OPEP, resulting in a reduction of ~15%, are cancelled by other relativistic contributions, they may have significant effects on pion exchange currents in nuclei.