  Although Casimir forces are inseparable from their fluctuations, little is
known about these fluctuations in soft matter systems. We use the membrane
stress tensor to study the fluctuations of the membrane-mediated Casimir-like
force. This method enables us to recover the Casimir force between two
inclusions and to calculate its variance. We show that the Casimir force is
dominated by its fluctuations. Furthermore, when the distance d between the
inclusions is decreased from infinity, the variance of the Casimir force
decreases as -1/d^2. This distance dependence shares a common physical origin
with the Casimir force itself.
