Mixing of axino and goldstino, and axino mass
  Axino, related to the SUSY transformation of axion, can mix with goldstino in
principle. This case is realized when some superfields carrying nonvanishing
Peccei-Quinn charges develop both scalar VEVs and F-terms. In this case, we
present a proper definition of axion and axino. With this definition, we
present the QCD axino mass in the most general framework, including non-minimal
K\"ahler potential. The axino mass is known to have a hierarchical mass
structure depending on accidental symmetries. With only one axino, if $G_A=0$
where $G=K+\ln|W|^2$, we obtain $m_{\tilde a}=m_{3/2}$. For $G_A\ne 0$, the
axino mass depends on the details of the K\"ahler potential. In the gauge
mediation scenario, the gaugino mass is the dominant axino mass parameter.
Therefore, we can take the theoretical QCD axino mass as a free parameter in
the study of its cosmological effects, ranging from eV to multi-TeV scales,
without a present knowledge on its ultraviolet completion.
