KYIV, Ukraine — In the vast central plaza known as Maidan, there’s a concert. The atmosphere is a curious mix of frontline army camp, new-age rock festival and solemn pilgrimage. Children line up to pose for photos with a wizened old Cossack complete with fur cap and upturned moustache. A woman in an embroidered peasant costume plays a flute; groups of teenage girls flirt with militia men. Silent groups form with bowed heads in front of the makeshift shrines to the fallen.