Tune shift with amplitude of the system. When the tune reaches resonant values, it can be unstable, and thus a tune-shift with amplitude can limit the stability region, or dynamic aperture. In classical mechanics, a simple example of a system with tune shift with amplitude is a pendulum. In accelerator physics, both the transverse and the longitudinal dynamics show tune shift with amplitude. A simple model of the transverse dynamics is of an oscillator with a single sextupole, it is referred to as the Hénon map. Another model for this case is the Standard Map. An important example is the typical case of distributed
Cassandra (metaphor) Cassandra (metaphor) The Cassandra metaphor (variously labelled the Cassandra "syndrome", "complex", "phenomenon", "predicament", "dilemma", or "curse") occurs when valid warnings or concerns are dismissed or disbelieved. The term originates in Greek mythology. Cassandra was a daughter of Priam, the King of Troy. Struck by her beauty, Apollo provided her with the gift of prophecy, but when Cassandra refused Apollo's romantic advances, he placed a curse ensuring that nobody would believe her warnings. Cassandra was left with the knowledge of future events, but could neither alter these events nor convince others of the validity of her predictions. The metaphor has been