Quantum electrodynamics, or QED, describes how light interacts with charged particles — for example, electrons. It is one of the most precise theories in history: its predictions match experiment to the eleventh decimal place. But it has an unpleasant feature: when you try to calculate something more complex than a simple exchange of a single photon, the answers often blow up to infinity.
Usually, physicists resort to a procedure called 'renormalization': they manually subtract infinities, replacing them with measured values of mass and charge. This works but leaves the feeling of a patch on an elegant dress. The new work proposes to redesign the dress itself — to give all virtual particles a minimum possible lifetime.
The author builds a version of QED where every virtual history has a lower bound on proper time — a tiny interval associated with a very high energy Λ. This parameter is not removed at the end of calculations; it remains part of the theory. As a result, all amplitudes (quantities determining the probability of processes) become finite from the start. The familiar renormalization is replaced by 'finite fitting'—parameters are simply matched to experiment at some energy.
Most importantly, the theory passes a test on a process considered a benchmark: the production of two photons in a quark-antiquark collision. The final answer for this process does not change, despite all the reworking. It's as if the foundation of a building were replaced, and the upper floors remained exactly in place.
as written by the authors arXiv:2606.22666
We formulate a finite-proper-time version of QED defined by a gauge-covariant generating functional in which every complete internal virtual history carries a physical lower endpoint $$s_0=\Lambda^{-2}$$ that is not removed. Closed fermion loops are defined by the heat-kernel determinant, while open fermion lines, vertices, and contact terms are derived from the corresponding open-line kernel. Gauge covariance gives the Ward--Takahashi hierarchy and transversality of the photon functions, while a worldline bound establishes ultraviolet finiteness of connected Euclidean amplitudes at every fixed perturbative order and fixed infrared regulator. One-loop mass and charge renormalisation are replaced by finite matching, and the anomalous magnetic moment acquires a calculable $$O(m^2/\Lambda^2)$$ correction. The free propagators retain canonical unit pole residues and contain no additional poles. Lorentzian amplitudes are defined at fixed order by analytic continuation of the Euclidean correlators in the external invariants with $$s_0$$ held fixed. An amputation theorem removes the endpoint factor from real external particles and reduces the two-body virtual correction at two loops to photon-modified on-shell form factors. The Born-level $$q\bar q\to\gamma\gamma$$ hard amplitude is unchanged, providing a parameter-free null test.
If virtual particles could exist for arbitrarily long, empty space would possess infinite energy — fortunately, quantum laws limit their lifetime.
In Asimov's novel 'The End of Eternity,' eternity had a lower limit on intervention — similarly, here a minimum interval is introduced below which the laws of physics do not operate.