Graduate Proving the Equivalence of Local and Global Maxima for Concave Functions

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SUMMARY

The theorem discussed establishes that for a concave differentiable function ##f## and a concave function ##g##, a point ##y## is a local maximum of the sum ##f(x) + g(x)## if and only if it is also a global maximum. This equivalence highlights the unique property of concave functions where local maxima coincide with global maxima. The discussion suggests utilizing the Intermediate Value Theorem and the Mean Value Theorem as foundational tools for constructing a formal proof of this theorem.

PREREQUISITES
  • Understanding of concave functions and their properties
  • Familiarity with differentiable functions
  • Knowledge of the Intermediate Value Theorem
  • Knowledge of the Mean Value Theorem
NEXT STEPS
  • Research formal proofs involving concave functions
  • Study the application of the Intermediate Value Theorem in optimization
  • Explore the Mean Value Theorem and its implications in calculus
  • Investigate the relationship between local and global maxima in optimization problems
USEFUL FOR

Mathematicians, calculus students, and anyone interested in optimization theory, particularly those studying properties of concave functions.

pitaly
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TL;DR
Proof of theorem. Intuition: local maxima and global maxima coincide for concave functions
Consider the following theorem:

Theorem: Let ##f## be a concave differentiable function and let ##g## be a concave function. Then: ##y \in argmax_{x} {f(x)+g(x)}## if and only if ##y \in argmax_{x} {f(y)+f'(y)(x-y)+g(x)}.##

The intuition is that local maxima and global maxima coincide for concave functions. But can anyone help me with a formal proof? Thanks in advance!
 
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Very interesting. Suggests me Intermediate Value Theorem and Mean Value Theorem, and this picture:
20211027_091904.jpg
 

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