A simplification in the proof of the non-isomorphism between $H^1(\delta )$ and $H^1(\delta ^2)$
Volume 150 / 2002
                    
                    
                        Studia Mathematica 150 (2002), 13-16                    
                                        
                        MSC: 30D55, 46B03, 60G46.                    
                                        
                        DOI: 10.4064/sm150-1-2                    
                                    
                                                Abstract
The proof that $H^1(\delta )$ and $H^1(\delta ^2)$ are not isomorphic is simplified. This is done by giving a new and simple proof to a martingale inequality of J. Bourgain.
 
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            