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								Ragnar Freij
							
              						
 
											- 
							
								Matthias Henze
							
              						
 
											- 
							
								Moritz W. Schmitt
							
              						
 
											- 
							
								Günter M. Ziegler
							
              						
 
									
			
																												
							
									
				
										Keywords:
				
				
																		Hansen polytopes, 													3^d conjecture, 													Hanner polytopes, 													split graphs, 													threshold graphs															
			
			
										
					
Abstract
					We analyze a remarkable class of centrally symmetric polytopes, the Hansen polytopes of split graphs. We confirm Kalai's $3^d$ conjecture for such polytopes (they all have at least $3^d$ nonempty faces) and show that the Hanner polytopes among them (which have exactly $3^d$ nonempty faces) correspond to threshold graphs. Our study produces a new family of Hansen polytopes that have only $3^d+16$ nonempty faces.