Exponential Rank Bounds for Random Matrices
Pith reviewed 2026-06-25 21:46 UTC · model grok-4.3
The pith
An n by n random matrix with independent entries each avoiding any fixed value with probability at least 1-b has probability at most exp(-c n k) of rank at most n-k.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Fix b ∈ (0,1), 1 ≤ k ≤ n, and let A be an n×n matrix with independent entries satisfying sup_x P(A_ij = x) ≤ b. There exists c > 0 such that P(rank A ≤ n - k) ≤ exp(-c n k).
What carries the argument
The uniform atom bound sup P(A_ij = x) ≤ b <1 on each independent entry, which limits the chance that rows or columns satisfy exact linear relations.
Load-bearing premise
The entries of the matrix are independent and each has probability at most b less than one of equaling any particular real number.
What would settle it
Generate many independent realizations of such a matrix for increasing n and fixed k, then check whether the empirical fraction with rank ≤ n-k decays at rate exp(-c n k) or slower.
read the original abstract
Fix $b\in(0,1)$, let $1\leq k\leq n$, and let $A=(A_{ij})$ be an $n\times n$ random matrix with independent real entries satisfying $$ \sup_{x\in\mathbb{R}}\mathbb{P}\{A_{ij}=x\}\leq b<1 \qquad (1\leq i,j\leq n). $$ We show that there exists $c>0$ such that $$ \mathbb{P}\{\operatorname{rank} A\leq n-k\}\leq \exp(-cnk), \qquad 1\leq k\leq n. $$
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript proves that if A is an n×n matrix with independent real entries satisfying sup_x P(A_ij = x) ≤ b < 1 for all i,j, then there exists c = c(b) > 0 such that P(rank A ≤ n−k) ≤ exp(−c n k) holds uniformly for all 1 ≤ k ≤ n.
Significance. The result supplies an exponential tail bound on the corank that scales with the product n k. It directly extends the classical exponential singularity bounds (recovered at k=1) to higher coranks while relying only on entrywise independence and the uniform atom condition; this is a clean, parameter-light strengthening of existing kernel-probability arguments.
Simulated Author's Rebuttal
We thank the referee for their positive report and recommendation to accept the manuscript. The summary accurately captures the main result, and we have no major comments to address.
Circularity Check
No significant circularity identified
full rationale
The derivation starts from the explicit assumptions of entrywise independence and the uniform atom bound sup P(A_ij = x) ≤ b < 1, then establishes the exponential tail bound on P(rank A ≤ n-k) via direct probabilistic control on the event that a fixed nonzero vector lies in the row space. No parameter is fitted to data and then relabeled as a prediction, no self-citation is invoked as a load-bearing uniqueness theorem, and the central inequality is not equivalent to its inputs by definition. The result for general k follows from the same atom-control mechanism used for the k=1 singularity case without circular reduction.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Matrix entries are independent
- domain assumption sup_x P(A_ij=x) ≤ b <1 for all i,j
Reference graph
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discussion (0)
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