Shastry-Sutherland square 4x4, J = 0.7, Jd = 1

Exact energy and best values (rules §6)

exact	-0.3968907	ED 10.1143/JPSJ.73.340, · the instance is solved

Energies as E/N (S.S). Classes are different claims and are not ranked against each other.

The Hamiltonian

H = J ∑_⟨ij⟩ σ_i·σ_j + J_d ∑_dimers σ_i·σ_j

Shastry-Sutherland lattice: a square lattice of bonds J with one diagonal bond J_d in every second plaquette, the orthogonal dimers. J = 0.7, J_d = 1, the couplings of the spin-1/2 form with S = σ/2, normalised to J_d = 1 (RULES.md 2.1); written here with Pauli matrices, so E/N in S units is E/(4N).

lattice: square
sites: 16
boundary: periodic
J: 0.7
Jd: 1
energies: 1

Stored as a total energy; quoted here as E/N (S.S), which is what the papers report (how the conversion works).

Every published energy

Grouped by what the number is. The exact energy comes first where there is one; in every other group the lowest unflagged energy is its best value, and each row's distance is to that best (rules §6).

Numerically exact (1)

Exact diagonalization, an exact solution, or sign-problem-free QMC where that is established. An exact energy is shown first, before the best of each other class. QMC is exact only within its error bar, which it must state, and reads exact (stochastic); an exact diagonalization outranks it. For a diagonalization resolved by symmetry sector only the ground state's sector is listed; the lowest energies of the other sectors are the instance's spectrum, in its JSON, and are not shown as the exact energy.

E/N (S.S)	distance to class best	σ	Var(E)	V-score	method	source	code	year	comment
-0.3968907exact	0	n/a	n/a	n/a	ED peer reviewed	10.1143/JPSJ.73.340,		2004

How these numbers were read

Where each number below was read, and how it was checked.

-0.3968907, ED

Checked 2026-10-20 · source text of arXiv:cond-mat/0309368 read locally (arXiv HTML or pypdf layout text); value copied from the harvested cell and the text, no LLM transcription of numbers; first reading and an adversarial second reading (2026-10-20)

Reported as. -0.63502 ×10^1

Sec. 3, the exact ground-state energy of the 4 x 4 cluster at J'/J = 0.7, printed '-0.63502 ×10^1' (layout text); the two stochastic estimates of the same state are not rows; version read: arXiv text (sources/cond-mat-0309368.txt); the journal version was not reached from this session, to be read on the verification pass (RULES.md 8) | Sec. 3: H = (1/4) J sum h (dimer bonds) + (1/4) J' sum h (square bonds), h = sigma.sigma, so S.S sums; J = 1, J'/J = 0.7; total energy of the 16-site cluster. QMBL's Lanczos diagonalization of the 4 x 4 torus gives -6.35025196 (SWEEP.md, 2026-10-20).

Coverage

Newest published number here: 2004.

This instance as data

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