In the microcosm, long-range forces, gravity or electricity, do not switch off even at enormous distances. Therefore, any particle drags behind it a trail of soft (i.e., very low-energy) photons or gravitons. This trail is called the "dress"; without it, calculations fall apart and infinities appear.
Previously, it was thought that because of this dress, two dressed particles could not be described as two independent entities. They are stuck together like two balls of yarn whose threads have become tangled. But the authors of the paper found new variables — special zero modes of radiation. They act like a comb: they separate the shared threads into two distinct balls. In these variables, the many-particle state honestly factorizes into a product of single-particle states.
In essence, the physicists changed the perspective. What looked like a fundamental non-factorizability turned out to be an artifact of old coordinates. In the new reference frame, the world is again assembled from simple building blocks, like a children's construction set where each piece lives its own life, but when assembled, it does not create extra glue.
as written by the authors arXiv:2606.15988
Four-dimensional gauge and gravitational theories exhibit long-range interactions that require asymptotic particles to be dressed by clouds of soft photons and gravitons. Faddeev-Kulish dressings render scattering amplitudes infrared-finite, but the resulting multi-particle states do not factorise into tensor products of dressed one-particle states. We show that this loss of Fock-space factorisation is not fundamental, but reflects an inappropriate choice of infrared variables. The real soft divergence is reproduced by the Goldstone modes of asymptotic symmetries, while the Coulomb phase is reproduced by new zero modes of the radiative fields that we introduce here. In these variables, infrared-finite dressed multi-particle states admit the usual Fock-space factorisation into single-particle dressed states.
The problem of the particle "dress" has been known since the 1960s. The famous construction by Faddeev and Kulish was the first attempt to solve it, but it was precisely that construction that led to the non-factorizability of states. The new work removes this defect.
In Greg Egan's novel "Distress," physicists struggle with a similar problem: how to separate a particle from its field in order to teleport consciousness. The solution comes through redefining what counts as "the particle itself."