Principia Metaphysica

The Einstein-Hilbert Term

The effective 13D gravitational action (from the 26D two-time framework) that reduces to Einstein gravity in 4D upon compactification.

M*11R

The gravitational sector of the effective 13D bulk action (26D → 13D via Sp(2,R) gauge fixing)

Sgravity = M*11 ∫ d13x √|G| R13
Derived from GR
S = &frac{1}{16πG} ∫ d4x √|g| R
4D Einstein-Hilbert Action
The standard gravitational action from General Relativity.
Established 1915
R
Ricci Scalar
R = gμνRμν, the trace of the Ricci tensor measuring curvature.
Riemannian Geometry
√|G|
Metric Determinant
Ensures the volume element is coordinate-invariant.
Diff. Geometry
M*11
13D Coupling
Dimensional analysis requires mass11 in 13D for correct units.
PM Extension
Derivation Path to Established Physics
Riemannian Geometry (Riemann, 1854) Mathematics
Kaluza-Klein Theory (1921) Established
Higher-Dimensional GR (String Theory, 1970s) Established

26D Origin

In the full 26D theory with signature (24,2), the gravitational action includes contributions from both time dimensions. The Sp(2,R) gauge symmetry reduces the two-time structure to an effective 13D shadow:

S = ∫ d26x √|G| [F(R,T,τ) + ℒPneuma + ℒSM + ℒhidden] Full 26D action with signature (24,2)

The F(R,T,τ) Function

The gravitational sector is governed by a modified gravity function that depends on the Ricci scalar R, the stress-energy trace T, and the torsion scalar τ:

F(R,T,τ) = R + αT + βT² + γτ + δτ² Modified gravity function with torsion coupling

Here α, β, γ, δ are coupling constants determined by the underlying 26D geometry. The torsion terms (γτ + δτ²) arise naturally from the Pneuma spinor condensates.

After imposing the Sp(2,R) constraints (X² = 0, X·P = 0, P² + M² = 0), the orthogonal time dimension is gauge-fixed, leaving an effective 13D description. The Z₂ mirror structure creates two copies of this 13D shadow, related by time-reversal symmetry.

Component Breakdown

The effective Einstein-Hilbert term is the standard gravitational action in the gauge-fixed 13D shadow. It couples the fundamental mass scale to the curvature of the effective bulk spacetime.

M*

Fundamental Mass Scale

The single fundamental mass scale of the theory in 13D. All other scales (Planck mass, GUT scale, etc.) emerge from M* through dimensional reduction.

M*11

Correct Dimensions

The power 11 ensures correct mass dimension: in 13D, [R] = mass2, and the action must be dimensionless, so we need mass11 to compensate for d13x.

R

Ricci Scalar

The effective 13D Ricci scalar R = GMNRMN, encoding the curvature of the gauge-fixed spacetime including both 4D and internal directions.

RMN

Ricci Tensor

The contraction of the Riemann tensor: RMN = RPMPN. Contains second derivatives of the 13D metric GMN.

Effective 13D Gravitational Action

After Sp(2,R) gauge fixing, the complete effective 13D gravitational action is:

Sgravity = M*11 ∫ d13x √|G| R Effective 13D Einstein-Hilbert action (gauge-fixed from 26D)

Components of the Metric

For Kaluza-Klein reduction, the 13D metric GMN decomposes as:

ds213 = gμν(x)dxμdxν + hab(x,y)dyadyb Metric ansatz for KK reduction

Where gμν is the 4D metric, hab is the metric on KPneuma, and we have omitted off-diagonal terms (gauge fields) for clarity.

4D Effective Gravity

Upon compactification over the 8-dimensional internal manifold KPneuma, the 13D action reduces to 4D Einstein gravity:

S4D = MPl2 ∫ d4x √|g| R4 + ... 4D effective gravitational action

The Planck Mass Relation

The 4D Planck mass emerges from the fundamental scale and internal volume:

MPl2 = M*11 ⋅ V8 Planck mass from extra dimensions

Where V8 = ∫KPneuma d8y √|h| is the volume of the internal manifold. This explains why MPl ~ 1018 GeV can emerge from a more fundamental scale M* that could be much lower.

Key Relation

With M* ~ 1016 GeV (GUT scale) and V8 ~ (M*-1)8, one can recover MPl ~ 1018 GeV. The internal manifold size is thus naturally tied to the GUT scale.

F(R,T,τ) Modifications

The framework naturally includes modifications to Einstein gravity through the F(R,T,τ) formalism, where T is the trace of the stress-energy tensor and τ is the torsion scalar:

F(R,T,τ) = R + αT + βT² + γτ + δτ² Modified gravity function (canonical form)

Modified Einstein Equations

Varying the action with respect to the metric yields the modified Einstein field equations:

Gμν + Λeffgμν = 8πGeff Tμν + α(Tμν + Θμν) + 2βT Tμν + Sμν(τ) Modified Einstein equations from F(R,T,τ) variation

Here Θμν contains matter-geometry coupling terms, and Sμν(τ) encodes torsion contributions from the Pneuma spinor condensates.

Effective Cosmological Constant

The torsion terms generate an effective cosmological constant:

Λeff = (γτ + δτ²)/2 Effective cosmological constant from torsion

This provides a dynamical origin for dark energy: the effective cosmological constant arises from torsion contributions rather than being a fixed parameter. As the universe evolves, τ varies, yielding a dynamical dark energy component.

These modifications arise from:

This provides a natural framework for cosmic acceleration without a bare cosmological constant, with the equation of state w → -1 as a late-time attractor.

Connection to the Pneuma Field

While the Einstein-Hilbert term appears as a separate contribution to the action, it is fundamentally sourced by the Pneuma field. The metric GMN itself is determined by Pneuma condensates:

GMN ~ ⟨ΨPΓ(MN)ΨPMetric from Pneuma bilinears (schematic)

This is the deep meaning of the fermionic geometry hypothesis: even the gravitational degrees of freedom ultimately trace back to the fundamental Pneuma field.