A translator gets distracted by every rustle in the hall, and a one-hour meeting stretches into two. Gluons, the particles that carry the strong force inside protons, behave much the same way. Usually, they dart back and forth, holding quarks together. But in collisions at enormous speeds, like those in cosmic accelerators, gluons can clump into a dense blob — a gluon condensate. Then the production of new particles sharply increases, and the radiation spectrum gains a characteristic break.
The authors of the new study applied this idea for the first time to three objects that emit both gamma rays and neutrinos: two active galaxies (TXS 0506+056 and NGC 1068) and a supernova remnant G54.1+0.3. Using real data from gamma-ray telescopes, they fitted a curve with a break predicted by the gluon condensate model. Then they calculated how many neutrinos should be produced along the way.
For both galaxies, the picture matched: the gamma-ray spectrum fits the model perfectly, and the predicted neutrino flux falls within the range detected by the Antarctic IceCube observatory. Moreover, the brighter the source in gamma rays, the more neutrinos are expected from it — a simple and beautiful connection. But the supernova remnant G54.1+0.3 behaved differently: after the break, its spectrum continued to harden, meaning particles became increasingly energetic, which does not fit the gluon condensate scenario. Apparently, a different acceleration mechanism is at work there.
Gluons not only glue quarks together but also carry color charge themselves, so they can interact with each other — unlike photons, which pass through each other without noticing.
In Peter Watts's novel Blindsight, alien ships use fields reminiscent of a gluon condensate to control radiation.