Matter–Antimatter Asymmetry Hypothesis

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A Threshold-Breaking Structural Transition in the Early Universe

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The Matter–Antimatter Asymmetry as a Thresholded Retention Transition paper develops a falsifiable structural framework for comparing baryogenesis mechanisms across particle physics and cosmology.

The observed universe contains a small but decisive excess of matter over antimatter, conventionally summarized by the comoving baryon asymmetry YB=(nB−nBˉ)/sY_B=(n_B-n_{\bar B})/s, with an observed value of order 10−1010^{-10}. The origin of this asymmetry remains unresolved. Existing baryogenesis models must satisfy the broad Sakharov requirements of baryon-number violation, C and CP violation, and departure from thermal equilibrium, but different mechanisms realize those conditions through very different microscopic processes.

This paper does not propose a new baryogenesis particle, force, or completed quantum-field-theoretic mechanism. Instead, it asks whether successful baryogenesis histories share a common, measurable transition structure that can be tested across distinct mechanism classes.

The central representation begins with the generic transport relationdYBdt=SB(t)−ΓW(t)YB(t),\frac{dY_B}{dt}=S_B(t)-\Gamma_W(t)Y_B(t),

where SB(t)S_B(t) is the signed source of baryon or lepton asymmetry and ΓW(t)\Gamma_W(t) is the effective washout rate. From this, the paper defines a retention kernel,K(t,tf)=exp⁡[−∫ttfΓW(u) du],K(t,t_f)=\exp\left[-\int_t^{t_f}\Gamma_W(u)\,du\right],

which measures how much asymmetry generated at time tt survives to a final evaluation time tft_f.

The framework then tests a three-stage structural sequence:

Base → Bias/Contrast → Retention/Integration

The Base phase corresponds to an initially near-symmetric state with no durable net asymmetry. The Bias phase is the interval in which signed source activity drives the system away from symmetry while washout and conversion processes remain active. The Retention phase begins when washout becomes sufficiently ineffective and the generated asymmetry stabilizes near its surviving late-time value.

This sequence is treated as a quantitative, falsifiable hypothesis rather than a descriptive analogy. The paper defines dimensionless trajectory features based on washout relative to cosmic expansion, normalized asymmetry growth, asymmetry magnitude, source direction, retained-source opportunity, persistence, and post-generation sign reversals.

The primary test is cross-model prediction. A frozen structural classifier is trained on baryogenesis benchmark trajectories from two mechanism families and evaluated on a third without mechanism-specific retuning. Candidate families include electroweak baryogenesis, thermal leptogenesis, and an additional mechanism such as Affleck–Dine or low-scale baryogenesis.

Support requires the structural model to outperform conventional transport summaries, flexibility-matched controls, and temporally shuffled surrogate models on held-out data. The hypothesis is weakened or rejected if the proposed phase sequence is not enriched among successful baryogenesis histories, if performance does not transfer across mechanism families, if the classifier depends on arbitrary threshold tuning, or if standard transport variables perform equally well or better.

The paper therefore reframes the matter–antimatter asymmetry problem as a test of whether successful baryogenesis exhibits a transferable source–competition–retention geometry. A positive result would establish a useful higher-level diagnostic across baryogenesis models. A negative result would place a clear boundary on the structural hypothesis rather than forcing agreement with it.