##  [Inertia Group](/inertia-group) 

  ##  [Inertia Group](https://puremath.quantumdictionary.io/inertia-group-0) 

  

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- Mathematics & Logic -

**Pure Mathematics Dictionary**

 







 

 

 

 



 

 

 

 

Definition

The subgroup of a decomposition group at a chosen prime consisting of automorphisms that act trivially on the residue field; equivalently the kernel of the projection from the decomposition group to the Galois group of the residue field, measuring the ramification at that prime.