A hypothetical scalar inflaton field with fine-tuned potential,
Initial conditions that themselves seem unlikely (e.g., low entropy, smoothness),
An ad hoc reheating mechanism without a fully embedded quantum gravity framework.
These challenges have led many to question the fundamental completeness of the inflationary paradigm.
2. Tunneling as an Origin Mechanism
In the framework proposed here, we replace both the singularity and inflation with a quantum tunneling event emerging from a pre-geometric quantum substrate:
The universe nucleates as a quantum bubble via structured tunneling through a metastable pre-cosmic vacuum.
The tunneling is not uniform or isotropic; instead, it carries phase and density fluctuations, leading to an initial fractal topology.
Each "layer" that emerges from the tunneling event corresponds to a quasi-stable vacuum slice with distinct curvature and energy density.
Mathematically, the nucleation can be modeled using a multi-field extension of the Coleman-De Luccia tunneling formalism, with phase-space anisotropies:
Aexp(SE[i,g,i]),\Gamma \sim A \exp\left(-\frac{S_E[\phi_i, g_{\mu\nu}, \theta_i]}{\hbar}\right),
where i\theta_i are initial tunneling phases that define each layer's configuration, and SES_E is the Euclidean action with interlayer coupling.
3. Emergence of Structure Without Inflation
This structured tunneling approach naturally seeds inhomogeneities, removing the need for:
A post hoc inflaton field,
An extra phase transition for reheating,
Initial isotropy or ad hoc curvature suppression.
Structure arises dynamically from:
Quantum decoherence of tunneling layers,
Phase interference among emerging regions,
Holographic boundary entanglement, which seeds long-range correlations (as a substitute for super-horizon modes in inflation).
The fractal scaling of initial density perturbations,
(r)rDH3,\rho(r) \sim r^{D_H - 3},
