text: A paper by Lutchyn, Sau and Das Sarma details how observing one of these events in a nanowire would prove the existence of Majorana fermions.
full_question: A paper by Lutchyn, Sau and Das Sarma details how observing one of these events in a nanowire would prove the existence of Majorana fermions. Properties of these events are described in Halperin-Lubensky-Ma theory. Widom scaling leads to the dependence of critical exponents that characterize these events. The dissociation of vortex-antivortex pairs occurs during one of these events named for Kosterlitz and Thouless. YBCO undergoes one of these events at an abnormally high temperature. For 10 points, name these transitions between different states of matter, such as freezing.
first_sentence: A paper by Lutchyn, Sau and Das Sarma details how observing one of these events in a nanowire would prove the existence of Majorana fermions.