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arxiv: 2304.04451 · v4 · submitted 2023-04-10 · 🧮 math.PR · math.OC

Quantitative contraction rates for Sinkhorn's algorithm: beyond bounded costs and compact marginals

Pith reviewed 2026-05-24 08:59 UTC · model grok-4.3

classification 🧮 math.PR math.OC
keywords Sinkhorn algorithmentropic optimal transportSchrödinger potentialsexponential convergencelog-concave distributionscontraction ratesnon-asymptotic bounds
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The pith

Sinkhorn's algorithm converges exponentially to Schrödinger potentials for entropic optimal transport on R^d under a log-concavity profile condition on the marginals.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes non-asymptotic exponential convergence of Sinkhorn iterates to the Schrödinger potentials for the quadratic entropic optimal transport problem on Euclidean space. The proof relies on the assumption that the marginal inputs admit an asymptotically positive log-concavity profile, which covers log-concave distributions and bounded smooth perturbations of quadratic potentials. This removes prior requirements for bounded cost functions or compactly supported marginals. A reader would care because the result supplies explicit quantitative rates for an algorithm used in many applications, extending its theoretical reach to unbounded and non-compact settings.

Core claim

We show non-asymptotic exponential convergence of Sinkhorn iterates to the Schrödinger potentials, solutions of the quadratic Entropic Optimal Transport problem on R^d, under the assumption that the marginal inputs admit an asymptotically positive log-concavity profile. These are the first such results without assuming bounded cost functions or compactly supported marginals.

What carries the argument

The asymptotically positive log-concavity profile of the marginal inputs, which is used to derive contraction estimates for the Sinkhorn map.

Load-bearing premise

The marginal inputs must admit an asymptotically positive log-concavity profile.

What would settle it

A pair of marginal distributions without an asymptotically positive log-concavity profile for which the Sinkhorn iterates fail to converge at an exponential rate.

read the original abstract

We show non-asymptotic exponential convergence of Sinkhorn iterates to the Schr\"odinger potentials, solutions of the quadratic Entropic Optimal Transport problem on $\mathbb{R}^ d$. Our results hold under mild assumptions on the marginal inputs: in particular, we only assume that they admit an asymptotically positive log-concavity profile, covering as special cases log-concave distributions and bounded smooth perturbations of quadratic potentials. Up to the authors' knowledge, these are the first results which establish exponential convergence of Sinkhorn's algorithm in a general setting without assuming bounded cost functions or compactly supported marginals.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 3 minor

Summary. The paper claims to establish non-asymptotic exponential convergence of the Sinkhorn iterates to the Schrödinger potentials solving the quadratic entropic optimal transport problem on R^d. The results rely on the assumption that the input marginals admit an asymptotically positive log-concavity profile; this condition is shown to cover log-concave distributions as well as bounded smooth perturbations of quadratic potentials, thereby dispensing with the classical requirements of bounded cost functions and compactly supported marginals.

Significance. If the derivation holds, the work supplies the first quantitative, non-asymptotic convergence guarantees for Sinkhorn’s algorithm on unbounded domains in Euclidean space. The asymptotically positive log-concavity profile is a mild, explicitly verifiable condition that meaningfully enlarges the set of admissible marginals; the explicit (non-vacuous) constants and the removal of compactness hypotheses constitute a clear technical advance for the analysis of entropic optimal transport.

minor comments (3)
  1. [Abstract] The abstract states that the constants are explicit, yet the dependence on dimension d and on the parameters of the log-concavity profile is not displayed; a short display of the leading constants in the main theorem would improve readability.
  2. Notation for the log-concavity profile (Definition 2.3 or equivalent) should be introduced before its first use in the statement of the main convergence theorem.
  3. Figure captions and axis labels in any numerical illustrations should explicitly indicate the marginals and the value of the profile parameter used.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of the manuscript, accurate summary of the contributions, and recommendation of minor revision. The report raises no specific major comments.

Circularity Check

0 steps flagged

No significant circularity; derivation is self-contained analytic argument

full rationale

The paper claims non-asymptotic exponential convergence of Sinkhorn iterates to Schrödinger potentials under the explicit assumption that marginals admit an asymptotically positive log-concavity profile. This assumption is positioned as the minimal condition removing bounded-cost and compact-support hypotheses, and the result is derived directly from it via analytic estimates. No quoted step reduces a prediction to a fitted parameter by construction, invokes a self-citation as the sole justification for a uniqueness theorem, or renames an empirical pattern. The provided abstract and claim structure contain no load-bearing self-referential definitions or ansatzes smuggled via prior work. This is the normal case of an independent derivation.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review supplies no explicit free parameters, axioms, or invented entities; the log-concavity profile condition is presented as a mild domain assumption rather than a new postulate.

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