Ramified and Unramified Motivic Multiple $t$-, $T$- and $S$-Values

In this paper, we consider several variants of motivic multiple zeta values of level two by restricting the summation indices to fixed parity patterns.

These variants include Hoffman's multiple $t$-values, Kaneko and Tsumura's multiple $T$-values, and the multiple $S$-values previously studied by the authors.

By applying the descent theory of Brown and Glanois to the motivic versions of these values, we derive criteria for determining when they are ramified or unramified.

Assuming Grothendieck's period conjecture, our results partially confirm a conjecture by Kaneko and Tsumura regarding the unramified nature of multiple $T$-values of depth less than four.

We obtain similar results for motivic multiple $S$-values.

Furthermore, we generalize a result of Charlton to broader families of unramified multiple $t$-values with unit components.

Finally, we propose several open problems for future research.