I'm reading a paper which has given the index symmetries in terms of a Young Tableau which I'm having trouble understanding e.g. one is of the form
$[\mu][\nu]$
$[\rho][\sigma]$
I understand that if it was fully horizontal (vertical) then it would correspond to a totally (anti)symmetric tensor in all its indices. In this example I'm given to believe it is actually ambiguous in that it could correspond to a tensor which is either symmetric in exchange of $\mu\nu$ and $\rho\sigma$ i.e. in the bracket notation then it'd be $T^{\mu\nu\rho\sigma}$ = $T^{(\mu\nu)(\rho\sigma)}$, but also in fact could be used to represent a tensor which is antisymmetric in $\mu\rho$ and $\nu\sigma$ i.e. $T^{\mu\rho\nu\sigma}$ = $T^{[\mu\rho][\nu\sigma]}$. Is this the case or have I misunderstood?
Also in a slightly more complicated case, say
$[\mu][\nu][\lambda]$
$[\rho][\sigma]$
Can this be read as a tensor symmetric in $\mu\nu\lambda$ and $\rho \sigma$, or a tensor which is antisymmetric in $\mu\rho$, $\nu\sigma$, and $\lambda$ does not obey any symmetries?