The early Universe was like a tightly coiled spring. In the first moments, it expanded at an unimaginable rate — a phase called inflation. Usually, this is attributed to a special field, but there's another idea: spacetime itself twists like a spring, and this twisting (in physics, torsion) becomes the engine of expansion.

When inflation ends, the energy of torsion must be transferred to ordinary particles: this is how the Universe reheats. But how exactly? The authors calculated that the inflaton (the torsion particle) hardly produces fermion pairs directly. Instead, through quantum anomalies, it actively creates gauge bosons and triples of particles involving the Higgs boson. This process is like a compressed spring, as it uncoils, brushing against neighboring parts and transferring energy to them.

This unusual decay gives a natural lower limit on the reheating temperature. This is important: if the temperature is too low, the first stars cannot ignite. The calculations show that spacetime torsion leaves a noticeable imprint on the early Universe, and this imprint can be sought in observational data.

The spring uncoiled, transferring energy to particles. The Universe became hot, and then began to cool, forming galaxies and stars. The torsion that drove inflation has vanished, but its consequences are still visible in the cosmic microwave background.