07 — Negative results (R13 contactless BP)

Productive failure: empirical / physics-based scrutiny of widely-claimed but un-validated CSI capabilities.

Scripts

Script	Thread	Verdict
r13_bp_physics_floor.py	R13	Don't ship contactless BP from CSI as a primary RuView feature. Four physics floors make it provably worse than a $20 arm cuff.

The four floors (R13)

Floor	Need	Have	Gap
PTT temporal resolution	0.5 ms (for 1 mmHg)	10 ms typical, 1 ms max ESP32	typical ESP32 deployment cannot do <20 mmHg
Spatial separation of two body sites	55 cm	40 cm Fresnel envelope at 5 m	sites NOT resolvable by single link
Pulse-contour SNR	+25 dB	+20 dB after bandpass	5 dB short (matches R6.1's 4.7 dB penalty)
Vs $20 arm cuff baseline	±2 mmHg	best published ±10 mmHg	5× worse + needs per-subject calibration

Why R13 is sensor-bound, not physics-bound-period

R20 (tick 37) + doc 17 + ADR-114 establish that the 5 dB shortfall is the multi-scatterer penalty (R6.1). It's sensor-bound: a different sensor (NV-diamond magnetometer at bedside) recovers what CSI cannot.

Sensor	Can detect HRV contour?	Can detect BP?
CSI alone (R13 NEGATIVE)	❌ 5 dB short	❌ same physics
NV-diamond at 1 m bedside (ADR-114)	✅ SDNN 119 ms	✅ via mm-PWV
Arm cuff (gold standard)	n/a	✅ ±2 mmHg

R13's value in the loop

Categorising R13 as a permanent physics-floor negative initially saved engineering effort. Then R20 + doc 17 + ADR-114 recategorised it as sensor-bound, recoverable. This is the research-loop pattern at its best: explicit failure modes that survive scrutiny but get reclassified when new tools arrive.

R20.1 (quantum-fusion demo) is the concrete demonstration that R13's recovery works.

Three niche scenarios where BP-from-CSI might close

1. Single-subject trend monitoring (relative not absolute)
2. Bed-instrumented controlled-still subject (25+ dB SNR achievable)
3. Multistatic PWV with 6+ anchors + per-installation calibration

The general "BP from a $9 ESP32 in the corner" claim does not close.

See also

• Research notes: docs/research/sota-2026-05-22/R13-contactless-bp-negative.md
• Recovery path: docs/research/sota-2026-05-22/R20-*.md, doc 17, ADR-114
• The other 2 negative result categories: R12 (missing-tool, revisitable) in 06-structure-detection/, R3.1 (architecture-error) in 05-cross-room-reid/