Definable Hamel bases and ${\sf AC}_\omega ({\mathbb R})$
Volume 253 / 2021
                    
                    
                        Fundamenta Mathematicae 253 (2021), 239-256                    
                                        
                        MSC: Primary 03E15; Secondary 03E35.                    
                                        
                        DOI: 10.4064/fm909-6-2020                    
                                            
                            Published online: 17 December 2020                        
                                    
                                                Abstract
There is a model of ${\sf ZF}$ with a lightface $\Delta ^1_3$ definable Hamel bases in which ${\sf AC}_\omega ({\mathbb R})$ fails.
 
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            