Torelli's theorem states that:
(Torelli's Theorem). Let $R$, $R'$ be compact
Riemann surfaces of genus $g$, $J(R)$, $J(R')$ their Jacobian varieties, $\Theta$, $\Theta'$ their respective theta divisors. The Riemann surfaces $R$ and $R'$ are isomorphic if and only if $(J(R), \Theta)$ and $(J(R'), \Theta')$ are isomorphic as principally polarized abelian varieties.
Let $R$, $R'$ be compact Riemann surfaces of genus $g$, $J(R)$, $J(R')$ their Jacobian varieties, $\Theta$, $\Theta'$ their respective theta divisors. The Riemann surfaces $R$ and $R'$ are isomorphic if and only if $(J(R), \Theta)$ and $(J(R'), \Theta')$ are isomorphic as principally polarized Abelian varieties.
In this theorem, $J(R)$, and $J(R')$ are required to be
isomorphic isomorphic not only as abelianAbelian varieties but also as principally polarized abelianAbelian varieties.
It turns out that the condition for $J(R)$ and $J(R')$
to be isomorphic as abelianAbelian varieties alone need not imply that $R$ and
$R'$ are isomorphic.
Does anyone know where IWhere can I find an example that shows that being $ J (R) $$J(R)$ and $ J (R ') $$J(R')$ being isomorphic just as Abelian varietyvarieties, does not imply that $ R $$R$ and $ R' $$R'$ are isomorphic?