Let $T : [0, 1]\times [0, 1] \rightarrow [0, 1]$. A $t$-norm is a function $T$ with properties:
$ T (x, 1) = x$
If $y\leq z$ then $T(x,y)\leq T(x,z)$
$T (x, y) = T (y, x) $
$T (x, T (y, z)) = T (T (x, y), z) $
Related to this question, Prove (or disprove) $T(a,b)T(c,d)\leq T(ac,bd)$? the inequality $T(a,b)T(c,d)\leq T(ac,bd)$ not always hold. It can be $T(a,b)T(c,d)\geq T(ac,bd)$.
My question:
Is there any condition such that this inequality holds? $$T(a,b)T(c,d)\geq T(ac,bd)$$