Representations of the Fundamental Group

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SUMMARY

The discussion centers on the relationship between locally constant sheaves of vector spaces and representations of the fundamental group of a topological space X. The user proposes that given a locally constant sheaf F on X, the associated topological space |F| acts as a covering space for X, allowing the construction of a monodromy action of the fundamental group π(X, x) on the fiber F_x. However, the user expresses uncertainty regarding the linearity of the map defined by the action of the fundamental group on the vector space structure of F_x. The key insight is the necessity of recognizing that F is a sheaf of vector spaces, which is crucial for establishing the linearity of the action.

PREREQUISITES
  • Understanding of locally constant sheaves in topology
  • Familiarity with fundamental groups and covering spaces
  • Knowledge of vector space structures
  • Basic concepts of monodromy in algebraic topology
NEXT STEPS
  • Study the properties of locally constant sheaves in algebraic topology
  • Explore the concept of monodromy actions in detail
  • Learn about the relationship between covering spaces and fundamental groups
  • Investigate linear representations of groups in the context of vector spaces
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Mathematicians, topologists, and graduate students interested in algebraic topology, particularly those studying the interplay between sheaf theory and fundamental groups.

olliemath
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This is not important, but it's been bugging me for a while.
I'm struggling to see how the locally constant sheaves of vector spaces on X give rise to representations of the fundamental group of X.

The approach I've been thinking of is the following. Given a locally constant sheaf F on X, the associated topological space |F| is a covering space for X. Thus, given a loop \gamma in X with base point x and a point y in F_x we can lift to a uniqe curve \gamma' in |F| with initial point y. Setting \gamma\cdot y=\gamma'(1) we obtain an action of \pi(X,x) on F_x which is called the monodromy action. F_x is a vector space, but I don't see how we know that the map y\mapsto\gamma\cdot y is linear.
Or possibly this is not the right approach?

Any help is greatly appreciated - O
 
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You have to use the fact that you're working in a sheaf of vector spaces, not just a sheaf of sets where you've put a vector space structure on one of the fibers.
 

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