  We report an observation of charge conservation breaking in a model study of
electronic current noise of transport through a dissipative double quantum dot
within generalized master equation formalism. We study the current noise
through a double quantum dot coupled to two electronic leads in the high bias
limit and a dissipative heat bath in the weak coupling limit. Our calculations
are based on the solution of a Markovian generalized master equation.
Zero-frequency component of the current noise calculated within the system,
i.e., between the two dots, via the quantum regression theorem exhibits
unphysical negative values. On the other hand, current noise calculated for
currents between the dots and the leads by the counting variable approach shows
no anomalies and seems physically plausible. We inquire into the origin of this
discrepancy between two nominally equivalent approaches and show that it stems
from the simultaneous presence of the two types of baths, i.e., the electronic
leads and the dissipative bosonic bath. This finding raises interesting
questions concerning conceptual foundations of the theory describing
multiple-baths open quantum systems widely encountered in nanoscience.
