R-lines for ordinary rings

Example 10.4.3. For an ordinary commutative ring \(k\), the group \(\Aut _{Hk}(Hk)\) is the discrete group \(k^\times \). In particular, \[ \Line _{H\F _2} \simeq * \qquadtext {and} \Line _{H\Z } \simeq \bB C_2. \]