The mental processes behind minimal group distinctions appear to be the same as many of those that underlie real group identities.
最小群体差异背后的心理过程似乎与构成真实群体身份的许多心理过程相同。
英语百科
Trivial group
In mathematics, a trivial group is a group consisting of a single element. All such groups are isomorphic, so one often speaks of the trivial group. The single element of the trivial group is the identity element and so it is usually denoted as such: 0, 1 or e depending on the context. If the group operation is denoted ∗ then it is defined by e ∗ e = e.