<p>Joint Theory Seminar Speaker: Albert Schwarz<br />mail: aschwarz@gmail.com<br />Title: Thermo-field dynamics and collisions of quasi-particles<br />Host: John Terning<br />Room: 432<br />Abstract:</p><p>The quantum theory can be formulated in the language of positive functionals on Weyl or Clifford algebra (L-functionals). It is shown that this language gives simple understanding of diagrams of Keldysh formalism (that coincide in our case with the diagrams of thermo-field dynamics). The matrix elements of the scattering matrix in the formalism of L-functionals are related to inclusive cross-sections, therefore we suggest the name "inclusive scattering matrix" for this notion.</p><p>The inclusive scattering matrix can be expressed in terms of on-shell values of generalized Green functions. This notion is necessary if we want to analyze collisions of quasiparticles.</p>
