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Pre-Big Bang (Gasperini-Veneziano) vs Conformal Cyclic Cosmology (CCC)

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Cyclic & Bouncing Cosmologies· within family

	Pre-Big Bang (Gasperini-Veneziano) Speculative	Conformal Cyclic Cosmology (CCC) Speculative
Proposed	1993	2005
Key figures	Maurizio Gasperini, Gabriele Veneziano	Roger Penrose
In one sentence	In string cosmology, a weakly-coupled contracting phase preceded the Big Bang, driven by the dilaton field.	A previous "aeon" existed. Its conformally smooth heat-death geometry became our Big Bang.
Predictions	Specific tilted spectrum of gravitational waves (blue tilt) Before the Bang, a quiet low-energy state described by string theory, where all the forces were very weak (a weakly-coupled string vacuum) Universe is asymmetric across the Bang	Concentric CMB rings (Hawking points) Smooth conformal transition, no [[singularity]] Massless [[dark matter]] required at aeon boundary
Where it breaks	Pre-Bang gravity-wave spectrum not yet detected Mechanism of the bounce remains incompletely understood Less developed than LQC bounce	Independent analyses find rings consistent with noise Requires massless dark matter, not established Community consensus is largely skeptical Bodnia et al. (2024) find no statistically significant low-variance circles or Hawking points in Planck/WMAP data using a ResNet18 ML pipeline, contradicting earlier Gurzadyan-Penrose claims.
Key unresolved problem	The breakdown at the bounce: at the moment of greatest curvature the low-energy string equations stop working, and no one has an accepted replacement, so the switch from shrinking to expanding is not fully described.	The missing fingerprint: other teams cannot find the predicted Hawking-point rings, faint circles in the cosmic microwave background, leaving CCC's one big observational claim statistically unsupported.
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Pre-Big Bang (Gasperini-Veneziano)

1993 · Speculative

Conformal Cyclic Cosmology (CCC)

2005 · Speculative

Proposed

1993

2005

Key figures

Maurizio Gasperini, Gabriele Veneziano

Roger Penrose

In one sentence

In string cosmology, a weakly-coupled contracting phase preceded the Big Bang, driven by the dilaton field.

A previous "aeon" existed. Its conformally smooth heat-death geometry became our Big Bang.

Predictions

Specific tilted spectrum of gravitational waves (blue tilt)
Before the Bang, a quiet low-energy state described by string theory, where all the forces were very weak (a weakly-coupled string vacuum)
Universe is asymmetric across the Bang

Concentric CMB rings (Hawking points)
Smooth conformal transition, no [[singularity]]
Massless [[dark matter]] required at aeon boundary

Where it breaks

Pre-Bang gravity-wave spectrum not yet detected
Mechanism of the bounce remains incompletely understood
Less developed than LQC bounce

Independent analyses find rings consistent with noise
Requires massless dark matter, not established
Community consensus is largely skeptical
Bodnia et al. (2024) find no statistically significant low-variance circles or Hawking points in Planck/WMAP data using a ResNet18 ML pipeline, contradicting earlier Gurzadyan-Penrose claims.

Key unresolved problem

The breakdown at the bounce: at the moment of greatest curvature the low-energy string equations stop working, and no one has an accepted replacement, so the switch from shrinking to expanding is not fully described.

The missing fingerprint: other teams cannot find the predicted Hawking-point rings, faint circles in the cosmic microwave background, leaving CCC's one big observational claim statistically unsupported.

Reader vote

No votes yet