Young Functions: Properties & Relations

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Young functions, defined as convex functions \(\Phi: \mathbb{R} \rightarrow \overline{\mathbb{R}}^{+}\) that satisfy the conditions \(\Phi(-x) = \Phi(x)\), \(\Phi(0) = 0\), and \(\lim_{x \rightarrow \infty} \Phi(x) = +\infty\), exhibit significant properties when continuous. The discussion highlights that continuity of Young functions on open convex sets, such as \(\mathbb{R}\), is established through their convexity. Furthermore, the analysis of nontrivial properties and ordering relations of continuous Young functions is essential for deeper mathematical insights, as referenced in the paper by Leonard on Orlicz spaces.

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Mathematicians, researchers in functional analysis, and students studying convex analysis will benefit from this discussion, particularly those interested in the properties of Young functions and their applications in Orlicz spaces.

fderingoz
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"In his studies on Fourier Series, W.H.Young has analyzed certain convex functions \Phi:IR\rightarrow\bar{IR}^{+} which satisfy the conditions : \Phi(-x)=\Phi(x), \Phi(0)=0, and lim_{x\rightarrow\infty}\Phi(x)=+\infty. Then \Phi is called a Young function.

Several interesting nontrivial properties and ordering relations can be analyzed if a Young function \Phi:IR\rightarrowIR^{+} is continuous. "(rao-ren theory of orlicz spaces 1991)

I think we can say from the definition of young function : Young functions are convex functions on IR and IR is a open convex set and we know also that if a funtion is convex on an open convex set then this function is continuous on that open set, So young functions are continuous.

Why the authors needs to write second paragraph,i.e. -Several interesting nontrivial properties and ordering relations can be analyzed if a Young function \Phi:IR\rightarrowIR^{+} is continuous-?

What is it that i can not see ?
 
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