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
Problem of why there is anything at all may necessarily exist. Particles can emerge from underlying quantum fields under the effects of quantum physics and possibly under other physical laws that may have existed at the start of the Big Bang. Problem of why there is anything at all The question "Why is there anything at all?", or, "Why is there something rather than nothing?" has been raised or commented on by philosophers including Gottfried Wilhelm Leibniz, Martin Heidegger − who called it the fundamental question of metaphysics − and Ludwig Wittgenstein. The question is general, rather than concerning the existence of anything specific such as the universe