Created as an analogy for Quantum Electrodynamics (QED) — which describes
the interactions due to the electromagnetic force carried by
photons — Quantum Chromodynamics (QCD) is the theory of physics that
explains the interactions mediated by the strong force — one of the four
fundamental forces of nature.

A new collection of papers published in The European Physical Journal
Special Topics and edited by Diogo Boito, Instituto de Fisica de Sao Carlos,
Universidade de Sao Paulo, Brazil, and Irinel Caprini, Horia Hulubei
National Institute for Physics and Nuclear Engineering, Bucharest, Romania,
brings together recent developments in the investigation of QCD.

The editors explain in a special introduction to the collection that due to
a much stronger coupling in the strong force — carried by gluons between
quarks, forming the fundamental building blocks of matter — described by
QCD, than the electromagnetic force, the divergence of perturbation
expansions in the mathematical descriptions of a system can have important
physical consequences. The editors point out that this has become
increasingly relevant with recent high-precision calculations in QCD, due to
advances in the so-called higher-order loop computations.

"The fact that the perturbative expansions in QCD are divergent strongly
affects the renormalization scheme and scale dependence of the truncated
expansions, which represents a major source of uncertainty in the
theoretical predictions of the standard model," Boito and Caprini, write.
"Understanding and taming this behavior is, therefore, one of the main
challenges for precision QCD to match the requirements of future accelerator
facilities."

In the special edition, this and other topics relating to QCD such as the
mathematical theory of resurgence and the existence of infrared (IR) and
ultraviolet (UV) renormalons are addressed by a cadre of experts in the
field.

These problems are tackled from a variety of angles and in the context of
related quantum field theories from what the editors say is a more
fundamental viewpoint or a phenomenological approach.

## Reference:

Diogo Boito et al, Renormalons and hyperasymptotics in QCD, The European
Physical Journal Special Topics (2021).
DOI: 10.1140/epjs/s11734-021-00276-w

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