Is compactness preserved under function mappings?

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Discussion Overview

The discussion revolves around the properties of compactness and connectedness under function mappings, specifically whether the image of a compact set under a function is also compact, and whether the image of a connected set is also connected. Additionally, there is a question regarding the closure of the inverse image of a closed set. The scope includes theoretical aspects of topology and function properties.

Discussion Character

  • Homework-related
  • Conceptual clarification

Main Points Raised

  • One participant asks if the function f is continuous, which is crucial for discussing the properties of compactness and connectedness.
  • Another participant questions the nature of the set A, asking if it is in R, R^n, or a general topological space, indicating the importance of the context in which these properties are evaluated.
  • A further assumption is made that A and B are subsets of some metric space, suggesting that the discussion may hinge on specific topological properties rather than general ones.
  • There is a suggestion that the original poster should move their question to the Homework Help section and provide prior attempts to solve the problems, as per forum guidelines.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the definitions and context of the sets and functions involved, indicating that multiple views remain on the assumptions necessary for the discussion.

Contextual Notes

There are limitations regarding the assumptions about the nature of the sets A and B, the continuity of the function f, and the specific topological space in which these properties are being considered.

Who May Find This Useful

Readers interested in topology, particularly those studying properties of functions and sets in metric spaces or general topological spaces, may find this discussion relevant.

deanslist1411
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1. If A is compact, show that f(A) is compact. Is the converse true?

2. If A is connected, show that f(A) is connected. Is the converse true?

3. If B is closed, show that B inverse is closed.

Any help with any or all of these three would be greatly appreciated.
 
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what is f? is f continuous?

There is a set of forums at the top of the page called Homework Help that is suited for these types of questions. You should start posting there as of now. Don't be surprised if you get a warning from a moderator and your thread is moved to the homework section.

Additionnally, Physicsforum guidelines require that you show us what you've tried before you are eligible to getting help.
 
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And what is A? is it in R? in R^n? Or in a general topological space?
 
I'm assuming that A and B are subsets of some metric space (if they were in a general topological space, then his #3 would be trivial since that would essentially be the definition of a continuous function)
 

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