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

AI Thread Summary
The discussion centers on proving that local and global maxima coincide for concave functions, specifically through the theorem stating that a point is a maximum of the sum of two concave functions if and only if it is a maximum of a specific linear approximation of one of those functions. Participants suggest using the Intermediate Value Theorem and the Mean Value Theorem as potential tools for the proof. The conversation emphasizes the importance of formalizing the intuitive understanding of concave functions in relation to maxima. The request for assistance indicates a collaborative effort to clarify this mathematical concept. Overall, the thread highlights the relationship between local and global maxima in the context of concave functions.
pitaly
Messages
6
Reaction score
1
TL;DR Summary
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!
 
Mathematics news on Phys.org
Very interesting. Suggests me Intermediate Value Theorem and Mean Value Theorem, and this picture:
20211027_091904.jpg
 
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
Fermat's Last Theorem has long been one of the most famous mathematical problems, and is now one of the most famous theorems. It simply states that the equation $$ a^n+b^n=c^n $$ has no solutions with positive integers if ##n>2.## It was named after Pierre de Fermat (1607-1665). The problem itself stems from the book Arithmetica by Diophantus of Alexandria. It gained popularity because Fermat noted in his copy "Cubum autem in duos cubos, aut quadratoquadratum in duos quadratoquadratos, et...
Thread 'Imaginary Pythagorus'
I posted this in the Lame Math thread, but it's got me thinking. Is there any validity to this? Or is it really just a mathematical trick? Naively, I see that i2 + plus 12 does equal zero2. But does this have a meaning? I know one can treat the imaginary number line as just another axis like the reals, but does that mean this does represent a triangle in the complex plane with a hypotenuse of length zero? Ibix offered a rendering of the diagram using what I assume is matrix* notation...
Back
Top