  The revolutionary power of future Rubin-LSST observations will allow us to
significantly improve the physics of pulsating stars, including RR Lyrae. In
this context, an updated theoretical scenario predicting all the relevant
pulsation observables in the corresponding photometric filters is mandatory.
The bolometric light curves based on a recently computed extensive set of
nonlinear convective pulsation models for RR Lyrae stars, covering a broad
range in metal content and transformed into the Rubin-LSST photometric system.
Predicted Rubin-LSST mean magnitudes and pulsation amplitudes have been adopted
to built the Bailey diagrams (luminosity amplitude vs period) and the
color-color diagrams in these bands. The current findings indicate that the
gLSST-rLSST, rLSST-iLSST colors obey to a well defined linear relation with the
metal content. Moreover, the Period Luminosity relations display in the reddest
filters (rLSST,iLSST,zLSST,yLSST) a significant dependence on the assumed metal
abundance. In particular, more metal-rich RR Lyrae are predicted to be fainter
at fixed period. Metal-dependent Period-Wesenheit relations for different
combinations of optical and NIR filters are also provided. These represent
powerful tools to infer individual distances independently of reddening
uncertainties, once the metal abundance is known and no relevant deviations
from the adopted extinction law occur. Finally, we also derived new linear and
quadratic absolute magnitude metallicity relations (gLSST vs [Fe/H]) and the
metallicity coefficient is consistent with previous findings concerning the B
and the V band.
