Appendix A: basic postulates of quantum mechanics, valid for isolated systems and perfect measurements, and direct implications, such as superposition principle and time reversibility.

This chapter provides a self-contained introduction to the basic aspects of Quantum Mechanics, focusing on what is must for Quantum Field Theory. The notions of state space, unitary operators, self-adjoint operators, and projective representation are covered as well as Heisenberg’s uncertainty principle. A complete proof of Stone’s theorem is given, but the spectral theory is covered only at the heuristic level. We provide an introduction to Dirac’s formalism, which is almost universally used in physics literature. The time-evolution is described in both the Schrödinger and the Heisenberg picture. A complete treatment of the harmonic oscillator, providing an introduction to the fundamental idea of creation and annihilation operators concludes the chapter.

We assemble a novel dataset in order to test theoretical propositions we develop on how states intervene in the elections of others. We start off with a random or representative sample of about 10 per cent of all elections since the end of World War II. Each of these is a case for us. We add a set of potential interveners, powers and organizations that may have a stake in intervening. We scour primary and secondary sources to extract information on how the government and opposition in the target state view relations with the potential interveners. We also extract information on whether and how the intervener acted in support of processes, or of candidates. This chapter is a codebook of how we constructed these novel, theory relevant variables. In addition, we supply extensive case-study notes. In those notes, we connect each of our coding decision to specific strings of text in the sources we used. The resulting database allows us to test the key propositions we develop.