UV-Complete Theory for T2 CPT-Violating Background

Investigating UV-complete quantum field theories that yield temperature-dependent CPT violation b0(T) proportional to T2, producing mass asymmetries at BBN while vanishing at T=0.

Key Results

T2
Scaling (all 3 models, R2=1.0000)
3.99e-10
Max mass asymmetry at BBN
1.10e-29
Max |b0(T0)| [MeV]
4.37e-4
Fine-tuning measure
3
RG Fixed Points
0.045%
One-loop correction to cb

CPT Background vs Temperature

|b0(T)| vs Temperature

b0/T2 Ratio

Model Comparison

Three UV Completion Models

Model Scaling Power n R2 dm/me (BBN) |b0(T0)| [MeV] Present-Day Safe
Cubic Vector 2.0000 1.0000 3.32e-15 9.19e-35 Yes
Scalar-Vector 2.0000 1.0000 3.99e-10 1.10e-29 Yes
PT-Symmetric 2.0000 1.0000 1.99e-10 5.51e-30 Yes

RG Flow and Wilson Coefficients

Coupling Running

Wilson Coefficient cb Running

BBN Constraints

He-4 Mass Fraction Yp vs b0

BBN Observables

ObservableComputedObservedStatus
Yp (He-4) 0.2277 0.2449 +/- 0.0040 Consistent
D/H (x10-5) 2.55 2.547 +/- 0.025 Match
b0max (Yp) 0.0422 MeV From 2-sigma Yp constraint
b0max (D/H) 0.1812 MeV From 2-sigma D/H constraint

Radiative Stability

Fine-Tuning vs Coupling

Naturalness Analysis

ParameterValue
Fine-tuning measure4.37e-4
Technically naturalYes
Protected correction4.37e-8 MeV
Unprotected correction63.33 MeV
Hierarchy ratio106

gsFine-TuningNatural?
0.014.37e-6Yes
0.051.09e-4Yes
0.14.37e-4Yes
0.21.75e-3Yes
0.51.09e-2Yes

EFT Matching

Wilson Coefficients at UV Scale

CoefficientTree LevelOne-LoopCorrection
cb 1.00e-11 1.0005e-11 +0.045%
cd 1.00e-18 1.0005e-18 +0.048%
cH 6.33e-17 6.33e-17 +0.001%

Experimental Bounds

Present-Day Constraints on CPT Violation

ExperimentObservableBoundb0max [MeV]
Penning trap (e-/e+) |me- - me+|/me 8.0e-9 4.09e-12
H-Hbar spectroscopy |delta nu|/nu 2.0e-12 2.04e-17
Neutral kaon delta_K 3.0e-19 GeV 3.00e-16

Reference: Barenboim et al., "Temperature-Dependent CPT Violation: Constraints from Big Bang Nucleosynthesis", arXiv:2601.06259 (2026)