Inflationary Big Bang, two variants comparedCompare two Inflationary Big Bang variants

A brief epoch of exponential expansion prepended to the hot Big Bang, solving horizon, flatness, and monopole problems.

Strongly supported

Basis: indirect

The CMB spectrum and flat space match what inflation predicts, but the field and potential that drove it are unknown.

	Left Strongly supported Open the variant page	Right Strongly supported Open the variant page
Proposed	1980 Alexei Starobinsky	1995 and 2020 Arjun Berera, Ian Moss, Rudnei Ramos, Mar Bastero-Gil
In one line	Starobinsky 1980, the foundational paper. An R-squared term drives early-universe inflation.	Inflation that never goes cold. The field sheds heat as it rolls, so there is nothing left to reheat.
The claim	The original higher-curvature gravity proposal: an R-squared term in the action drives a phase of cosmic inflation in the very early universe. Starobinsky 1980 is the foundational work that originated the higher-curvature gravity research program.	Inflation where the inflaton keeps shedding energy into a thermal radiation bath, so the universe stays warm throughout and needs no separate reheating phase.
What would test it	4 predictions, first shown An R-squared term in the gravitational action produces a phase of slow-roll inflation in the very early universe with specific perturbation spectra All 4	4 predictions, first shown A radiation bath persists throughout inflation, so the handover to the hot Big Bang is smooth, with no separate reheating phase. All 4
Where it breaks	4 objections, first shown Current data constrains the Starobinsky parameter range tightly; the model is testable rather than free, and next-generation B-mode measurements will either confirm or restrict it sharply All 4	3 objections, first shown Deriving the dissipation strength from first-principles quantum field theory is hard: the inflaton must couple strongly enough to thermalize a bath, yet not so strongly that radiative corrections spoil the potential's flatness. All 3
Shared by both	3 shared objections, first shown The initial conditions for inflation itself remain unexplained, raising the question of whether inflation solves the original Big Bang fine-tuning or just relocates it. All 3
Key unresolved problem	The unexplained-scale problem: the size of the R-squared term sets how powerful early-universe inflation was, but that number has to be put in by hand, with no deeper quantum-gravity theory yet explaining where it comes from.	The dissipation coefficient problem: it is hard to calculate the friction from basic quantum field theory, because coupling the field strongly enough to heat up a radiation bath tends to wrinkle the flat potential the model relies on.
Sources	2, all established No INSPIRE citation counts	5, all established 1,910 INSPIRE citations, across all 5 sources
Readers	No votes yet	No votes yet

In one line

Starobinsky 1980, the foundational paper. An R-squared term drives early-universe inflation.

Inflation that never goes cold. The field sheds heat as it rolls, so there is nothing left to reheat.

The claim

The original higher-curvature gravity proposal: an R-squared term in the action drives a phase of cosmic inflation in the very early universe. Starobinsky 1980 is the foundational work that originated the higher-curvature gravity research program.

Inflation where the inflaton keeps shedding energy into a thermal radiation bath, so the universe stays warm throughout and needs no separate reheating phase.

What would test it

4 predictions, first shown

An R-squared term in the gravitational action produces a phase of slow-roll inflation in the very early universe with specific perturbation spectra

All 4

4 predictions, first shown

A radiation bath persists throughout inflation, so the handover to the hot Big Bang is smooth, with no separate reheating phase.

All 4

Where it breaks

4 objections, first shown

Current data constrains the Starobinsky parameter range tightly; the model is testable rather than free, and next-generation B-mode measurements will either confirm or restrict it sharply

All 4

3 objections, first shown

Deriving the dissipation strength from first-principles quantum field theory is hard: the inflaton must couple strongly enough to thermalize a bath, yet not so strongly that radiative corrections spoil the potential's flatness.

All 3

Shared by both

3 shared objections, first shown

The initial conditions for inflation itself remain unexplained, raising the question of whether inflation solves the original Big Bang fine-tuning or just relocates it.

All 3

Key unresolved problem

The unexplained-scale problem: the size of the R-squared term sets how powerful early-universe inflation was, but that number has to be put in by hand, with no deeper quantum-gravity theory yet explaining where it comes from.

The dissipation coefficient problem: it is hard to calculate the friction from basic quantum field theory, because coupling the field strongly enough to heat up a radiation bath tends to wrinkle the flat potential the model relies on.

Proposed

1980

Alexei Starobinsky

1995 and 2020

Arjun Berera, Ian Moss, Rudnei Ramos, Mar Bastero-Gil

Sources

2, all established

No INSPIRE citation counts

5, all established

1,910 INSPIRE citations, across all 5 sources

Readers

No votes yet