Published online by Cambridge University Press: 11 August 2014
Let  $(X,{\it\sigma}_{X}),(Y,{\it\sigma}_{Y})$ be one-sided subshifts and
$(X,{\it\sigma}_{X}),(Y,{\it\sigma}_{Y})$ be one-sided subshifts and  ${\it\pi}:X\rightarrow Y$ a factor map. Suppose that
${\it\pi}:X\rightarrow Y$ a factor map. Suppose that  $X$ has the specification property. Let
$X$ has the specification property. Let  ${\it\mu}$ be a unique invariant Gibbs measure for a sequence of continuous functions
${\it\mu}$ be a unique invariant Gibbs measure for a sequence of continuous functions  ${\mathcal{F}}=\{\log f_{n}\}_{n=1}^{\infty }$ on
${\mathcal{F}}=\{\log f_{n}\}_{n=1}^{\infty }$ on  $X$, which is an almost additive potential with bounded variation. We show that
$X$, which is an almost additive potential with bounded variation. We show that  ${\it\pi}{\it\mu}$ is a unique invariant Gibbs measure for a sequence of continuous functions
${\it\pi}{\it\mu}$ is a unique invariant Gibbs measure for a sequence of continuous functions  ${\mathcal{G}}=\{\log g_{n}\}_{n=1}^{\infty }$ on
${\mathcal{G}}=\{\log g_{n}\}_{n=1}^{\infty }$ on  $Y$. When
$Y$. When  $(X,{\it\sigma}_{X})$ is a full shift, we characterize
$(X,{\it\sigma}_{X})$ is a full shift, we characterize  ${\mathcal{G}}$ and
${\mathcal{G}}$ and  ${\it\mu}$ by using relative pressure. This
${\it\mu}$ by using relative pressure. This  ${\mathcal{G}}$ is a generalization of a continuous function found by Pollicott and Kempton in their work on factors of Gibbs measures for continuous functions. We also consider the following question: given a unique invariant Gibbs measure
${\mathcal{G}}$ is a generalization of a continuous function found by Pollicott and Kempton in their work on factors of Gibbs measures for continuous functions. We also consider the following question: given a unique invariant Gibbs measure  ${\it\nu}$ for a sequence of continuous functions
${\it\nu}$ for a sequence of continuous functions  ${\mathcal{F}}_{2}$ on
${\mathcal{F}}_{2}$ on  $Y$, can we find an invariant Gibbs measure
$Y$, can we find an invariant Gibbs measure  ${\it\mu}$ for a sequence of continuous functions
${\it\mu}$ for a sequence of continuous functions  ${\mathcal{F}}_{1}$ on
${\mathcal{F}}_{1}$ on  $X$ such that
$X$ such that  ${\it\pi}{\it\mu}={\it\nu}$? We show that such a measure exists under a certain condition. In particular, if
${\it\pi}{\it\mu}={\it\nu}$? We show that such a measure exists under a certain condition. In particular, if  $(X,{\it\sigma}_{X})$ is a full shift and
$(X,{\it\sigma}_{X})$ is a full shift and  ${\it\nu}$ is a unique invariant Gibbs measure for a function in the Bowen class, then there exists a preimage
${\it\nu}$ is a unique invariant Gibbs measure for a function in the Bowen class, then there exists a preimage  ${\it\mu}$ of
${\it\mu}$ of  ${\it\nu}$ which is a unique invariant Gibbs measure for a function in the Bowen class.
${\it\nu}$ which is a unique invariant Gibbs measure for a function in the Bowen class.