  Relativistic jets are highly collimated plasma outflows emerging from
accreting black holes. They are launched with a significant amount of magnetic
energy, which can be dissipated to accelerate nonthermal particles and give
rise to electromagnetic radiation at larger scales. Kink instabilities can be
an efficient mechanism to trigger dissipation of jet magnetic energy. While
previous works have studied the conditions required for the growth of kink
instabilities in relativistic jets, the radiation signatures of these
instabilities have not been investigated in detail. In this paper, we aim to
self-consistently study radiation and polarization signatures from kink
instabilities in relativistic jets. We combine large-scale relativistic
magnetohydrodynamic (RMHD) simulations with polarized radiation transfer of a
magnetized jet, which emerges from the central engine and propagates through
the surrounding medium. We observe that a localized region at the central spine
of the jet exhibits the strongest kink instabilities, which we identify as the
jet emission region. Very interestingly, we find quasi-periodic oscillation
(QPO) signatures in the light curve from the emission region. Additionally, the
polarization degree appears to be anti-correlated to flares in the light
curves. Our analyses show that these QPO signatures are intrinsically driven by
kink instabilities, where the period of the QPOs is associated to the kink
growth time scale. The latter corresponds to weeks to months QPOs in blazars.
The polarization signatures offer unique diagnostics for QPOs driven by kink
instabilities.
