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String theory predicts an infinite tower of massive excitations, which are crucial for its self-consistency. In this work we propose studying massive string resonances using classical fields, and show that states of the first massive level appear as ghosts in a gravitational theory. Despite this apparent drawback, our "haunted" theory offers insights into ordinary string dynamics. While an extension to higher mass levels remains a challenge, our approach bridges string theory and quantum field theory in a promising way.
Description
The infinite tower of massive resonances in string theory may be described level-by-level using a simplified "stringy" model and a dual field-theory realization.