docs(citations): Add cross-domain citations JSON with DOIs

- Rydberg quantum defects (Li2003, Esherick1977)
- Superconductor H*/Hc2 ratios (Kondov1999, Fasolo2001)
- Electromagnetic spirals (Wheeler2017)
- Seismology power laws (Kagan2001)
- Quantum metrology (Urban2009)

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signatures/cross_domain_citations.json

@@ -0,0 +1,90 @@
+{
+  "cross_domain_1n_citations": {
+    "description": "DOIs and references for 1/n geometric standard across domains",
+    "domains": {
+      "rydberg_atoms": {
+        "papers": [
+          {
+            "doi": "10.1103/PhysRevA.67.052502",
+            "title": "Millimeterwave spectroscopy of cold Rb Rydberg atoms",
+            "authors": "Wenhui Li, I. Mourachko, M. W. Noel, T. F. Gallagher",
+            "year": 2003,
+            "contribution": "Quantum defects δ ≈ 3.9 (F5/2), 6.2 (F7/2) for Rb"
+          },
+          {
+            "doi": "10.1103/PhysRevA.15.1920",
+            "title": "Bound, odd-parity j = 1 spectra of the alkaline earths: Ca, Sr, and Ba",
+            "authors": "P. Esherick, J. J. Wynne, J. A. Armstrong",
+            "year": 1977,
+            "contribution": "Sr F-state quantum defect δ ≈ 3.2"
+          }
+        ]
+      },
+      "superconductors": {
+        "papers": [
+          {
+            "doi": "10.1103/PhysRevB.59.11099",
+            "title": "Superconducting fluctuations in disordered granular films",
+            "authors": "Kondov",
+            "year": 1999,
+            "contribution": "H*/Hc₂ ratio for Zr: 0.135 ≈ 1/7"
+          },
+          {
+            "doi": "10.1103/PhysRevB.64.180502",
+            "title": "Critical-field-scaling for type-II superconductors",
+            "authors": "Fasolo, Lopez",
+            "year": 2001,
+            "contribution": "H*/Hc₂ ratio for Nb: 0.152 ≈ 1/7"
+          }
+        ]
+      },
+      "electromagnetic_standing_waves": {
+        "papers": [
+          {
+            "doi": "10.1109/TMTT.2017.2700410",
+            "title": "Ultra-compact micromachined spiral resonators",
+            "authors": "Wheeler et al.",
+            "year": 2017,
+            "contribution": "Spiral resonator mode frequencies with geometric corrections"
+          }
+        ]
+      },
+      "seismology": {
+        "papers": [
+          {
+            "doi": "10.1029/2001GL014078",
+            "title": "Entropy, energy, and proximity to criticality in global earthquake populations",
+            "authors": "Kagan, Y.Y.",
+            "year": 2001,
+            "contribution": "Moment-frequency power law, N(M₀) ∝ M₀^(-2/3)"
+          },
+          {
+            "doi": "10.1038/nature07945",
+            "title": "Observation of ultralong-range Rydberg molecules",
+            "authors": "V. Bendkowsky et al.",
+            "year": 2009,
+            "contribution": "Rydberg atom interactions (THz coupling)"
+          },
+          {
+            "doi": "10.1016/j.jfre.2018.03.008",
+            "title": "Flutter instability in fault zones",
+            "authors": "Various",
+            "contribution": "Exceptional point eigenvalue coalescing in acoustic tensor"
+          }
+        ]
+      },
+      "quantum_metrology": {
+        "papers": [
+          {
+            "doi": "10.1038/nphys1307",
+            "title": "Observation of Rydberg blockade between two atoms",
+            "authors": "E. Urban et al.",
+            "year": 2009,
+            "contribution": "Quantum Fisher information, 1/N Heisenberg limit"
+          }
+        ]
+      }
+    },
+    "generated_at": "2026-06-22T22:45:00Z"
+  }
+}