Corollary · fixed-depth obstruction

CRD-SAT-11c

No fixed seed depth determines this branching cost

Exact statement

Across unbounded clause width, no fixed finite unit-propagation seed depth determines the fixed-policy DPLL decision count: for any t≥1t\ge1, choosing r=t+2r=t+2 gives semantically equivalent databases with equal signatures through depth tt but different decision counts.

StatusProved from the arbitrary-width family
External reviewNo documented external or specialist review of this FPRD result is recorded.

Context

This is the negative half of the later exact completeness-radius result.

Hypotheses and scope

  • Clause width is allowed to grow with the requested observation depth.
  • The branching resource is the fixed-policy decision count of CRD-SAT-11b.

Proof or evidence

Given tt, take r=t+2r=t+2. CRD-SAT-11a gives semantic equivalence and signature equality through r−2=tr-2=t, while CRD-SAT-11b gives decision counts rr and r−1r-1.

Verification notes

The quantifier over seed depth and the dependence of width on that depth were made explicit; the result is not stated for fixed-width formulas.

Limitations

  • Unbounded width is essential to this construction.
  • At fixed maximum added-clause width, CRD-SAT-12a gives a finite complete radius.

Open work

Use CRD-SAT-12a for the complementary positive theorem at fixed added-clause width.