{ "items" : [
    { "id" : "http://dbpedia.org/resource/Roton"
      "properties" : {
        "http://www.w3.org/2000/01/rdf-schema#comment" : [ "In theoretical physics, a roton is an elementary excitation, or quasiparticle, in superfluid helium-4. The dispersion relation of elementary excitations in this superfluid shows a linear increase from the origin, but exhibits first a maximum and then a minimum in energy as the momentum increases. Excitations with momenta in the linear region are called phonons; those with momenta close to the minimum are called rotons."] } } }
