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Identify the underlying physics of inflation (inflaton field and potential)

Determine the physical mechanism responsible for the postulated inflationary epoch, including specifying the correct inflaton field and its potential V(φ), or an alternative microphysical account of accelerated early-universe expansion consistent with observations.

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Background

Inflation explains the flatness and horizon problems and successfully predicts features of the cosmic microwave background, yet many inequivalent inflation models exist. The observed data underdetermine the inflaton’s identity and potential.

The book stresses that this uncertainty may be in-principle persistent, leaving the microphysics driving inflation unknown.

References

But there is also bad news. The data we now have, and maybe all the data we will ever have, leave wide open which of the many possible mechanisms — which sort of field φ, and which potential V(φ) — actually occurred. ... we do not know — and we may never know — the underlying physics of inflation.

— The Multiverse: a Philosophical Introduction (2505.23639 - Butterfield, 29 May 2025) in Chapter 5, Section 3, item (3)