# Course talk:MATH600D 17/18-II

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Thread title | Replies | Last modified |
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exercise 1/25/2018 | 0 | 18:02, 30 January 2018 |

Presentation 2 | 0 | 01:31, 30 January 2018 |

Lectures for math 600 | 1 | 08:05, 17 January 2018 |

hi regarding the exercise last time : $\bigvee \sigma (P) + \bigvee \sigma(P') = B$, where P, P' are defined as maximal ideals of the integral closure of B. $\sigma$ is the automorphism of $B$.

by prop1.11(b) of atiyah mcdonald , $\bigvee \sigma (P)$ and $\bigvee \sigma(P') $ are maxima ideals. by assumption in notes that P and P' are in different orbits, it follows that sum of 2 different maximal ideals is the whole ring $B$