2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/18033We analyse the dynamical density fluctuation spectra for cuprates starting from the $t-J$ model in a slave-boson 1/N representation. The results obtained are consistent with diagonalization studies and show novel low-energy structure on the energy scale $J+δt$ due to the correlated motion of holes in a RVB spin liquid. The low-energy response implies an anomalous renormalization of several phonon modes. Here we discuss the renormalization of the highest breathing phonons in La$_{2-x}$Sr$_x$CuO$_4$.10 pages and 8 figures, talk given at NATO Advanced Research Workshop, Bled, Slovenia, 26-30 April 2000Strongly Correlated Electronstext