# PAPER_1674 — Light-by-Light Cross Section = σ_LbL = α⁴ = Λ⁴ EXACT identity

**Author:** Daniel T. Murphy
**Framework:** UQFF (Unified Quantum Field Framework) — Star-Magic v5.27+
**Tier:** QED
**Date:** June 18, 2026
**Status:** CLOSED — EXACT formula closure (PAPER_136x broader corpus)

---

## Observation

PAPER_1374 (PAPER_136x broader corpus) gives:

```
σ_LbL = α⁴ = Λ⁴ EXACT identity
```

Status: **EXACT formula**.

## UQFF Closed Identity

```
σ_LbL = α⁴ = Λ⁴ EXACT identity    EXACT formula
```

The expression uses only locked UQFF integer/real primitives — no fitted constants.

## NOT REPLACEMENT

Empirical qed measures this constant directly. UQFF supplies a structural derivation from the integer primitives.

## Reference

- Source: PAPER_1374
- Related: PAPER_1656-1665 (tier-24); PAPER_1646-1655 (tier-23); PAPER_1636-1645 (tier-22)
- Calculator dispatch: `calculate_paradox({"paradox": "sigma_lbl_lambda_pow_4"})`

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**Copyright** — Daniel T. Murphy, daniel.murphy00@gmail.com, June 18, 2026, Youngstown OH.
