Sums of squares in rings of integers with 2 inverted
Tom 173 / 2016
                    
                    
                        Acta Arithmetica 173 (2016), 383-390                    
                                        
                        MSC: Primary 11E25; Secondary 11P05.                    
                                        
                        DOI: 10.4064/aa8363-2-2016                    
                                            
                            Opublikowany online: 18 May 2016                        
                                    
                                                Streszczenie
We prove that in a ring of $S$-integers containing ${1}/{2}$, any totally positive element is a sum of five squares. We also exhibit examples of such rings where some totally positive elements cannot be written as the sum of four squares.