TY - JOUR T1 - A lemma and a conjecture on the cost of rearrangements JF - Rend. Sem. Mat. Univ. Padova 110 (2003) 97-102 Y1 - 2003 A1 - Alberto Bressan AB - Consider a stack of books, containing both white and black books. Suppose that we want to sort them out, putting the white books on the right, and the black books on the left (fig.~1). This will be done by a finite sequence of elementary transpositions. In other words, if we have a stack of all black books of length $a$ followed by a stack of all white books of length $b$, we are allowed to reverse their order at the cost of $a+b$. We are interested in a lower bound on the total cost of the rearrangement. PB - Università di Padova UR - http://hdl.handle.net/1963/2914 U1 - 1786 U2 - Mathematics U3 - Functional Analysis and Applications ER -