Why use single head and do not use positional embedding in Attentive module

请问一下作者，您这里为什么在Attentive module只是用单头，而且没有使用位置编码。并且用于连接的FFN也设置隐藏层数目也设置成为了和词向量一样的维度。

另外就是还有一个问题在交叉注意力中，
Ui= AttentiveModule(U, R, R)，Rl = AttentiveModule(R，U, U)
这个公式的设计大概是一个怎样的想法

刚刚那个问题一不小心手误删掉了，表示尴尬。
麻烦作者解答一下谢谢啦。

No file or test is named. Start by locating the Attentive module and its FFN, then trace the cross-attention entry points represented by Ui = AttentiveModule(U, R, R) and Rl = AttentiveModule(R, U, U). Done means documenting the rationale for single-head attention, omitting positional embeddings, the FFN dimensions, and the cross-attention design.

Written by the indexing model from the issue text.