Speaker
Mr
Atabak Jalali
(FZU)
Description
Ghosts frequently emerge in alternative theories of gravity. They are degrees of freedom with wrong-sign kinetic terms, and the common lore is that ghostly degrees of freedom lead to dynamical instabilities, so-called runaways. In quantum mechanics, ghosts are commonly believed to lack physically relevant quantum descriptions. However, ghosts can be benign both classically and quantum mechanically. This talk will briefly cover some recent advancements in stability of classical ghostly systems, and then present a fully physical quantum mechanical description of a ghost. In particular, we define the vacuum state and demonstrate the absence of quantum runaway behavior.