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Real-valued functions of real variable, analytic properties of functions and sequences, limits, continuity, smoothness of these.

3 votes

How can I measure the Morse index in infinite dimensions?

It seems that simply one can't measure it. Here below is briefly described an example of a nondegenerate indefinite inner product space having no cardinal-valued Morse index. Consider $(\ell^{2},<.,. …
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2 votes

Splitting a space into positive and negative parts

Statement 1. is generally not true when V is infinite-dimensional. For, let L be an infinite-dimensional real vector space, and let L* be its algebraic dual. Put V := L x L*, and define a: V x V --> …
Ady's user avatar
  • 4,060
21 votes

solving $f(f(x))=g(x)$

Q2) has a negative answer. Namely, if, e.g., $g(x)=-x$ for all $x\in\mathbb{R}$, then there is no continuous $f:\mathbb{R\rightarrow\mathbb{R}}$ such that $f\circ f=g$. As to Q3, see, e.g., Theor …
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