Where does ghost collide?

In quantum field theory a ghost is a mathematical field added to a calculation to keep it consistent, one that never shows up as a real particle anyone could detect. Faddeev and Popov's 1967 Feynman diagrams for the Yang-Mills field introduced these fields, now called Faddeev-Popov ghosts, so that the quantization of gauge theories, the framework behind the strong and electroweak forces, would yield sensible answers. The ghost cancels the contribution of unphysical parts of the gauge field and then drops out of every measurable result. The referent is a bookkeeping field inside an equation, not an emptied cell, an image made from light, or a lapse in human contact.[1]

Unit

A field variable in the equations, not an observable particle

Recovery means

Not applicable

Measured by

Never measured directly; its presence is inferred from the consistency of the calculated result

In optics ghost imaging is a method that reconstructs a picture of an object using light that never reaches the camera which forms the image. Pittman, Shih, Strekalov, and Sergienko's 1995 Optical imaging by means of two-photon quantum entanglement produced the first such image: pairs of entangled photons were split, one beam passing the object and a single detector, the other reaching a position-sensitive detector, and the picture appeared only when the two detectors' readings were correlated. The name comes from the image forming where no ordinary image should be. The referent is a real optical measurement built on correlations between two light paths, unlike a husk of a cell, a field in a gauge calculation, or a person who disappears from a conversation.[2]

Unit

A reconstructed image, built from coincidence counts between two detectors

Recovery means

Not applicable

Measured by

Formed by correlating a single-pixel detector in the object beam with a scanning detector in the reference beam

In social research ghosting is ending a relationship by suddenly stopping all communication and giving no explanation, whether with a dating partner, a friend, or a job applicant. Freedman, Powell, Le, and Williams's 2019 Ghosting and destiny: Implicit theories of relationships predict beliefs about ghosting studied who finds the practice acceptable, and LeFebvre and colleagues' 2019 Ghosting in emerging adults' romantic relationships described how people carry it out and how they later account for it. The referent is a human behavior, the deliberate withdrawal of contact, captured through surveys and personal accounts, and it bears no relation to an emptied cell, a field in a physics equation, or an image made from correlated photons.[3][4]

Unit

One instance of unilaterally ceasing contact without explanation

Recovery means

Not applicable

Measured by

Assessed through self-report surveys and retrospective accounts of ghosting or being ghosted