Lineability within Peano Curves, Martingales, and Integral Theory

Abstract EN

This paper is devoted to give several improvements of some known facts in lineability approach.

In particular, we prove that (i) the set of continuous mappings from the unit interval onto the unit square contains a closed, c-semigroupable convex subset, (ii) the set of pointwise convergent martingales (Xn)n∈N with EXn→∞ is c-lineable, (iii) the set of martingales converging in measure but not almost surely is c-lineable, (iv) the set of sequences (Xn)n∈N of independent random variables, with EXn=0, ∑n=1∞var Xn=∞, and the property that (X1+⋯+Xn)n∈N is almost surely convergent, is c-lineable, (v) the set of bounded functions f:[0,1]×[0,1]→R for which the assertion of Fubini’s Theorem does not hold is consistent with ZFC 1-lineable (it is not 2-lineable), (vi) the set of unbounded functions f:[0,1]×[0,1]→R for which the assertion of Fubini’s Theorem does not hold (with infinite integral allowed) is c-lineable but not c+-lineable.