  Coupled systems in mesoscopic regime are of interest as charge fluctuation
between the sub-systems will depend on electron-electron interactions and will
play a dominant role in determining their thermodynamic properties. We study
some simple systems like a stub or a bubble strongly coupled to a ring. We show
that for strong electron-electron interaction, there are some regimes where
these charge fluctuations are quenched and charge is individually conserved in
the two subsystems. This feature does not depend on choice of parameters or
charge distribution.
