Alphabeta Math

Finite Probability and the Probabilistic Method

About this page
How statement and proof provenance work

The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.

  • Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
  • AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
  • AI-generated: a genuinely novel statement formulated by AI, with no source for the claim itself.

These labels describe origin, not correctness: citations and verification chips remain separate evidence.

✓ 20 results · all verified · 11 also independently AI-judged
Every result on this page is machine-checked by a proof checker and read in full and owner-audited; the judge is an additional, independent cross-model AI review of the proofs. The 9 not AI-judged were verified by owner audit (typically over a confirmed judge false positive), not failures.
1 · Prerequisites
Abstract Algebra
Combinatorics
Linear Algebra
Measure Theory
Number Theory
Real Analysis
Set Theory
Topology
2 · Logical flowchart

3 · Items

Theorem

An event of positive probability in a finite probability space is nonempty

Theorem

The first-moment method for avoiding or forcing a finite count of bad events

Proposition

The deletion-alteration method converts an expected defect count into a deterministic lower bound

Lemma

1+x≤exp(x) for every real x, hence (1-p)ᵐ≤exp(-mp)

Definition

The Erdős-Rényi finite random graph G(n,p)

Lemma

A prescribed set of present and absent edges in G(n,p) has product probability

Definition

The moment generating function M_X(t)=E[e^tX] on a finite probability space

Lemma

For a uniform random sign ε, E[e^tε]≤ e^t²/2

Theorem

For n≥1 independent random signs, ℙ(|S|≥ t)≤2 exp(-t²/(2n)) for t>0

Definition

Dependency digraphs for a finite family of bad events

Lemma

The conditional-probability induction underlying the Lovász Local Lemma

Theorem

The asymmetric Lovász Local Lemma for finitely many events

Corollary

The symmetric Lovász Local Lemma under ep(d+1)≤1

Theorem

Every k-uniform hypergraph with fewer than 2ᵏ⁻¹ edges is 2-colourable

Theorem

A k-uniform hypergraph is 2-colourable when every edge meets at most d other edges and e(d+1)≤2ᵏ⁻¹

Theorem

Every finite graph with m edges has a cut containing at least m/2 edges

Theorem

Szele's bound: for every n≥1, some n-vertex tournament has at least n!/2ⁿ⁻¹ Hamilton paths

Definition

Tournament property Sₖ: every set of at most k vertices is dominated by one vertex

Theorem

If k≥1 and n≥3k² 2ᵏ, an n-vertex tournament with property Sₖ exists

Definition

Dominating sets in a finite graph

Theorem

An n-vertex graph of minimum degree δ>1 has a dominating set of size at most n(log(δ+1)+1)/(δ+1)

Definition

Sum-free subsets of the integers

Lemma

There are arbitrarily large primes congruent to 2 modulo 3

Theorem

Every nonempty finite set of n nonzero integers has a sum-free subset of size greater than n/3

Lemma

The expected number of cycles of length at most ℓ in G(n,p)

Lemma

ℙ(α(G(n,p))≥ s)leC(n, s)(1-p)^C(s, 2)≤ nˢ exp(-pC(s, 2)) for s≤ n

Theorem

For all positive k,ℓ, some finite graph has girth greater than ℓ and chromatic number greater than k

Sources