By analyzing the solutions of the Friedmann equation for a maximally symmetric spacetime, researchers found out whether the quantum vacuum of scalar fields can cause inflation or today’s accelerated expansion. A field with conformal coupling (a type of interaction with gravity) and a mass around ten Planck masses fits two roles at once: it can serve as both inflaton and dark energy. A minimally coupled field, in contrast, is useless. Conclusion: perhaps both phenomena share a common origin—quantum fluctuations of the same field, like a chord that strikes both the opening and the finale of the cosmic symphony.
Right after the Big Bang, space swelled at an unimaginable speed — that's inflation. Now expansion has slowed, but galaxies are moving apart faster and faster. The culprit behind the acceleration has been named dark energy. Physicists propose: a single quantum field is responsible for both processes — like a compressed spring pervading the cosmos. The field interacts with gravity in a special way, so its energy does not wane as space expands.
To play this dual role, the field must be massive — about ten times heavier than the Planck mass. That's the mass of a speck of dust, yet for a quantum object it is enormous. This coincidence suggests: inflation and dark energy are not separate mysteries, but two sides of the same spring. The idea, proposed by Alan Guth for inflation and developed by Adam Riess for dark energy, is supported by new calculations.
🎯 The Planck mass — around 22 micrograms — is the weight of a grain of sand or a tiny droplet. For a quantum field, such a mass is huge, though to us it’s imperceptible.