This paper resolves a question proposed in Kardaras and Robertson [Ann. Appl.
Probab. 22 (2012) 1576-1610]: how to invest in a robust growth-optimal way in a
market where precise knowledge of the covariance structure of the underlying
assets is unavailable. Among an appropriate class of admissible covariance
structures, we characterize the optimal trading strategy in terms of a
generalized version of the principal eigenvalue of a fully nonlinear elliptic
operator and its associated eigenfunction, by slightly restricting the
collection of nondominated probability measures.Comment: Published in at http://dx.doi.org/10.1214/12-AAP887 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org