Inverses of asymptotic functions

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Discussion Overview

The discussion revolves around the asymptotic behavior of the inverses of monotone increasing functions that are asymptotic to each other. Participants explore whether the inverses of such functions maintain the asymptotic relationship as x approaches infinity.

Discussion Character

  • Exploratory, Debate/contested, Conceptual clarification

Main Points Raised

  • One participant proposes that if f(x) and g(x) are monotone increasing functions that are asymptotic, it raises the question of whether their inverses are also asymptotic.
  • Another participant suggests looking for counter-examples to explore this question further.
  • A different participant provides an example of log x and log 2x, indicating a need for clarification on the conditions under which the asymptotic relationship holds for inverses.
  • Another example mentioned is log x and 1 + log x, highlighting the importance of the growth rates of the functions involved and how small differences can impact the asymptotic behavior of their inverses.

Areas of Agreement / Disagreement

Participants do not reach a consensus, and multiple competing views remain regarding the conditions necessary for the inverses to be asymptotic.

Contextual Notes

The discussion hints at limitations related to the growth rates of the functions and the specific conditions under which the asymptotic behavior of inverses may or may not hold, but these aspects remain unresolved.

Palafox
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Suppose f(x) and g(x) are monotone increasing functions (continuous, and smooth if necessary) which are asymptotic -- that is, their quotient has limit 1 as x→∞. Are their inverses asymptotic?
 
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Hint: Look for counter-examples.
 
Right, mfb! For example, log x and log 2x. What I should have asked was, under what circumstances...
 
That is nearly the example I found (log x and 1 + log x). I think you need those slowly/quickly growing functions, where a small difference in one variable (vanishes in the limit) can lead to a large difference in the other one.
 

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