pith:QVISCZET
Why DDIM Hallucinates More Than DDPM: A Theoretical Analysis of Reverse Dynamics
DDIM reverse trajectories can trap on the line between two modes after a critical time, while DDPM noise lets them escape and reach the true modes.
arxiv:2605.06831 v2 · 2026-05-07 · cs.LG · cs.AI
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Claims
We analyze the reverse ODE (DDIM) and SDE (DDPM) for a Gaussian mixture target, proving that after a critical time τ, (a) DDIM can become stuck on the segment connecting the two nearest modes and (b) DDPM *stochasticity* helps it become unstuck from this region, thus avoiding hallucination.
The theoretical results and empirical observations are derived for a low-dimensional Gaussian mixture target; the same trapping behavior and benefit of stochasticity may not occur or may be harder to characterize for high-dimensional, non-Gaussian data distributions used in practice.
DDIM gets stuck between modes in reverse diffusion on Gaussian mixtures after critical time τ, but DDPM stochasticity prevents this and lowers hallucination rates.
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Receipt and verification
| First computed | 2026-06-01T01:02:41.899643Z |
|---|---|
| Builder | pith-number-builder-2026-05-17-v1 |
| Signature | Pith Ed25519
(pith-v1-2026-05) · public key |
| Schema | pith-number/v1.0 |
Canonical hash
85512164935deff6a86f74bcdeef5603420cc74837beef9119d33065ed6598e6
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curl -sH 'Accept: application/ld+json' https://pith.science/pith/QVISCZETLXX7NKDPOS6N532WAN \
| jq -c '.canonical_record' \
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Canonical record JSON
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