Emergent Linearized Gravity from D4 Lattice Elasticity

Emergent Linearized Gravity from D
4
Lattice Elasticity:
Exact SO(4) Isotropy and Defects as Gravitational Sources
Raghu Kulkarni
SSMTheory Group, IDrive Inc., Calabasas, CA 91302, USA
May 2026
Abstract
In the SSMTheory framework, the D
4
root lattice is physical four-dimensional spacetime
and the matter content arises from trapped lattice defects. We construct the elasticity theory
of small lattice deformations on D
4
and identify the resulting long-wavelength effective action
with linearized gravity coupled to defect sources. The central technical result is that the rank-
four bond tensor T
µνρσ
=
P
n∈N
n
µ
n
ν
n
ρ
n
σ
on the D
4
kissing set is exactly the fully-symmetric
isotropic tensor 4(δ
µν
δ
ρσ
+ δ
µρ
δ
νσ
+ δ
µσ
δ
νρ
), with no anisotropic correction at any order. The
hypercubic Z
4
lattice fails this isotropy, exhibiting cubic anisotropy, and even the 3D FCC
sublattice contained as a spatial slice of D
4
fails rank-four isotropy; the missing pieces are
supplied exactly by the twelve cross-slice nearest neighbors. The elastic Lagrangian takes the
isotropic form L = (λ/2)(·u)
2
+µ ϵ
αβ
ϵ
αβ
with equal Lamé parameters λ = µ = k, Poisson ratio
ν = 1/5, and bulk modulus K = 3k/2. Bare displacements correspond to gauge transformations
of the linearized metric; the gauge-invariant gravitational content is sourced by defects, with
the trapped tetrahedral defects identified in the matter paper as quarks playing the role of
localized gravitational sources. The static long-distance strain field has Kelvin form u 1/r,
reproducing the Newton potential, and the Newton constant is identified as G
N
2
P
c
3
/,
equivalently G
N
c/M
2
P
, of Planck-scale magnitude. The construction is explicitly linearized
and weak-field; full nonlinear General Relativity, the cosmological constant, and gravitational
radiation are not addressed here.
1 Introduction
1.1 D
4
as physical spacetime in the SSM framework
This paper continues the SSMTheory program in which the Face-Centered Cubic (FCC) lattice
is the substrate of three-dimensional physical space [1] and the D
4
root lattice is physical four-
dimensional spacetime [3]. The matter paper [1] establishes that trapped tetrahedral defects in
the FCC lattice carry quark quantum numbers (fractional charge, three color charges, linear con-
finement) and computes the proton-to-electron mass ratio m
p
/m
e
= 1836 from a single-coupling
structural counting. The mass-energy-information paper [2] identifies the five stable mass eigenval-
ues {1, 207, 273, 1836, 1839} with the electron, muon, pion, proton, and neutron via a [[192, 130, 3]]
CSS-code verification cost. The D
4
paper [3] extends the spatial picture to four dimensions:
D
4
{x
4
= 0} = FCC by the slicing theorem, the lattice is the densest 4D packing with kiss-
ing number K = 24, and the Wilson lattice gauge action on its 32 triangular plaquettes per unit
raghu@idrive.com
1
cell gives an exactly SO(4)-symmetric Yang-Mills theory with no anisotropy correction at any order
in the lattice spacing.
The present paper addresses the third sector of physics: gravity. Under SSM the lattice spacing
a is a fixed physical scale of order the Planck length
P
, not a continuum-limit regulator to be
sent to zero. The D
4
lattice is therefore not just a mathematical scaffold but an elastic medium
with finite bond stiffness, and small deformations of the lattice obey a well-defined long-wavelength
elasticity theory. The idea that gravity emerges from underlying microscopic degrees of freedom, in
the same sense that hydrodynamics emerges from molecular dynamics, goes back to Sakharov [7]
and has been pursued in many forms since [8, 5, 6]. We work within the explicit dictionary between
lattice elasticity and linearized gravity developed in [5, 6], with the lattice geometry determining
the elastic constants.
1.2 Main results
We establish four results:
Rank-four isotropy of D
4
(Theorem 1). The bond tensor T
µνρσ
=
P
n
n
µ
n
ν
n
ρ
n
σ
summed
over the 24 nearest-neighbor vectors of D
4
is exactly proportional to the unique fully-symmetric
isotropic rank-four tensor:
T
µνρσ
= 4 (δ
µν
δ
ρσ
+ δ
µρ
δ
νσ
+ δ
µσ
δ
νρ
) .
This is a stronger isotropy property than the rank-two structure tensor
ˆ
S
µν
= 6δ
µν
established
in [3]. The hypercubic lattice Z
4
and the 3D FCC sublattice both fail rank-four isotropy.
Isotropic elastic Lagrangian (Theorem 2). The long-wavelength elastic energy density on
D
4
is
L
elastic
=
λ
2
( · u)
2
+ µ ϵ
αβ
ϵ
αβ
, λ = µ = k,
where k is the bond spring constant. Both Lamé parameters are equal, the Poisson ratio is ν =
1/5, and the bulk modulus is K = 3k/2. Both longitudinal and transverse modes have isotropic
dispersion at every order in the wavevector.
Defects as gauge-invariant gravitational sources (Section 5). Bare displacement fields
u
µ
(x) correspond to gauge transformations of the linearized metric perturbation h
µν
=
µ
u
ν
+
ν
u
µ
and carry no physical (gauge-invariant) content. The gauge-invariant gravitational content
is sourced by lattice defects. The trapped tetrahedral defects identified in the matter paper as
quarks [1] play the role of localized strain sources. The defect-induced strain field has Kelvin form
at long distances with potential 1/r, reproducing the Newton law.
Planck-scale Newton constant (Section 5). Identifying the lattice spacing with the Planck
length and the bond spring constant with the Planck-scale stiffness k E
P
/ℓ
2
P
, the elastic Newton
constant works out to G
N
c/M
2
P
of the correct order of magnitude to match observed gravity.
The precise dimensionless prefactor depends on the topological strength of the defect source.
2
1.3 Scope and limitations
This paper is explicitly linearized and weak-field. We do not derive the full nonlinear Einstein-
Hilbert action, do not compute Riemann curvature beyond the linearized order, and do not address
gravitational radiation, the cosmological constant, or the geometric structure of strong-field solu-
tions. The construction shares the technical core of the elasticity-to-gravity programs of Kleinert
and others [5, 6]: the elastic Lagrangian on a regular lattice admits a linearized-gravity reinterpreta-
tion when topological defects are present, and the lattice geometry determines the elastic constants.
What is new here is the application to the D
4
lattice, where the rank-four isotropy theorem ensures
the construction is exactly Lorentz-invariant at every order in the lattice spacing, and where the
matter-as-defects identification from [1] gives the gravitational source picture directly without an
additional matter Lagrangian.
2 Preliminaries on the D
4
Lattice
We recall the basic structural facts about D
4
established in [3].
The D
4
root lattice is defined by
D
4
= {x Z
4
: x
1
+ x
2
+ x
3
+ x
4
0 (mod 2)}.
Its 24 nearest-neighbor vectors are
N = e
µ
± e
ν
: 1 µ < ν 4},
each of squared length |n|
2
= 2. The kissing number K = 24 saturates the four-dimensional
kissing-number bound. The slicing theorem [3] states that
D
4
{x
4
= c}
=
FCC for even c, D
4
{x
4
= c}
=
FCC (shifted) for odd c.
The 24 nearest-neighbor vectors partition naturally as 12 + 12:
Spatial (in-slice) neighbors: the 12 vectors ±e
i
±e
j
with i, j {1, 2, 3}, i < j. These reproduce
the FCC kissing set in the spatial slice x
4
= 0.
Cross-slice (cross-time) neighbors: the 12 vectors ±e
i
± e
4
for i {1, 2, 3}. These connect
adjacent x
4
slices.
The rank-two structure tensor of D
4
is [3]
S
µν
=
X
n∈N
n
µ
n
ν
= 12 δ
µν
,
or in unit-length normalization
ˆ
S
µν
= 6δ
µν
. This rank-two isotropy is shared by FCC in three
dimensions, hypercubic in any dimension, and any lattice whose nearest-neighbor star has cubic or
higher symmetry.
3 The Rank-Four Isotropy Theorem
The novel content begins at rank four. For elasticity the relevant tensor is built from four powers
of nearest-neighbor vectors, and its symmetry properties determine the leading anisotropies of the
elastic action.
3
Definition 1. The rank-four bond tensor of a Bravais lattice with nearest-neighbor set N is
T
µνρσ
=
X
n∈N
n
µ
n
ν
n
ρ
n
σ
.
This tensor is automatically fully symmetric in all four indices.
Theorem 1 (Rank-four isotropy of D
4
). The rank-four bond tensor of D
4
is exactly the fully-
symmetric isotropic rank-four tensor:
T
µνρσ
= 4
δ
µν
δ
ρσ
+ δ
µρ
δ
νσ
+ δ
µσ
δ
νρ
.
Proof. We give a symmetry argument followed by direct verification.
Symmetry argument. The point group of D
4
is the Weyl group F
4
of order 1152, which acts on
the 24 nearest-neighbor vectors transitively. Any rank-four tensor T
µνρσ
defined as a sum over an
F
4
-orbit is automatically F
4
-invariant. By construction T is also fully symmetric in all four indices.
The space of fully-symmetric rank-four tensors on R
4
is 35-dimensional. Imposing invariance
under B
4
(the signed-permutation subgroup of F
4
, of order 384) reduces this to a 2-dimensional
space spanned by
S
µνρσ
= δ
µν
δ
ρσ
+ δ
µρ
δ
νσ
+ δ
µσ
δ
νρ
and δ
(4)
µνρσ
=
(
1 µ = ν = ρ = σ,
0 otherwise.
(B
4
-invariance forces nonzero components only on patterns where each axis appears an even number
of times, leaving two pattern classes: (a, a, a, a) giving δ
(4)
, and (a, a, b, b) giving the cross-pair
pieces of S.) The full F
4
contains elements outside B
4
; specifically, the orthogonal transformation
H =
1
2
1 1 1 1
1 1 1 1
1 1 1 1
1 1 1 1
permutes the D
4
nearest neighbors (e.g. H(1, 1, 0, 0)
T
= (0, 0, 1, 1)
T
) and has
entries outside {0, ±1}, so H F
4
\B
4
. Under H, the isotropic S is invariant (it is O(4)-invariant),
while δ
(4)
is not invariant. Hence F
4
-invariance reduces the B
4
-invariant 2-d space to the 1-d
subspace spanned by S, and T
µνρσ
= αS
µνρσ
for some α.
Normalization. Evaluating at (µ, ν, ρ, σ) = (1, 1, 1, 1): T
1111
=
P
n
n
4
1
. The D
4
neighbors with
n
1
= 0 are ±e
1
± e
j
for j {2, 3, 4}, giving 3 × 4 = 12 vectors each with n
4
1
= 1. So T
1111
= 12,
while S
1111
= 3. Hence α = 4.
Decomposition check. The decomposition N = N
sp
N
cs
(12+12 neighbors) gives T = T
sp
+T
cs
.
Neither summand alone is proportional to S the spatial sum vanishes whenever any index equals
4, and the cross-slice sum has a specific bias toward indices that include 4. Their sum, however, is
exactly 4S. The component-by-component verification and the explicit check that S is H-invariant
while δ
(4)
is not are carried out in the script verify_gravity.py [9] (§3, §3b, and §5).
Proposition 1 (Comparison with other lattices). For comparison:
1. Hypercubic Z
4
: T
µνρσ
= 2δ
(4)
µνρσ
, where δ
(4)
denotes the rank-four Kronecker symbol (which is
1 if all four indices are equal and 0 otherwise). This is anisotropic: it has no δ
µν
δ
ρσ
cross-pair
structure.
2. 3D FCC sublattice of D
4
(alone): T
FCC
ijkl
with i, j, k, l {1, 2, 3} is not proportional to the 3D
isotropic tensor δ
ij
δ
kl
+ δ
ik
δ
jl
+ δ
il
δ
jk
.
3. D
4
requires both spatial and cross-slice neighbors to achieve exact rank-four isotropy. Neither
subset alone is isotropic; the sum is.
4
The verification of all three claims is in verify_gravity.py [9], §4 and §5.
The geometric meaning of Theorem 1: the cross-slice neighbors of D
4
carry exactly the anisotropy-
canceling weight that completes the spatial FCC’s rank-four anisotropy into the unique isotropic
rank-four tensor in 4D. The fact that D
4
is the lattice where this completion is exact, rather than
approximate, is the structural reason emergent gravity on D
4
inherits exact SO(4) Euclidean sym-
metry (equivalently, exact Lorentz invariance after Wick rotation) at every order in the lattice
spacing.
This parallels the gauge-sector result of [3]: the D
4
plaquette stiffness tensor (built from sums
of plaquette holonomies) is exactly proportional to the pair-antisymmetric isotropic tensor δ
µρ
δ
νσ
δ
µσ
δ
νρ
at rank four, giving exact SO(4) Yang-Mills. The elastic stiffness tensor (built from bond
stretches) is exactly proportional to the fully-symmetric isotropic tensor S
µνρσ
at rank four, giving
exact SO(4) elasticity. Both rely on the same F
4
symmetry of D
4
; they are the unique O(4)-
singlets of their respective symmetry types (antisymmetric and symmetric pair structure). Gauge
and gravity inherit exact Lorentz invariance from the same lattice geometry.
4 Elastic Lagrangian on D
4
4.1 Bond-stretch energy in the long-wavelength limit
Let u
µ
(x) denote a small displacement field defined on D
4
sites. For a nearest-neighbor pair
(x, x + n) the bond length changes by
L
n
= |x + n + u(x + n) x u(x)| |n| ˆn · [u(x + n) u(x)],
where ˆn = n/|n| is the unit vector along the bond. Expanding u(x + n) u(x) n
β
β
u
α
for
slowly-varying u:
L
n
n
α
n
β
|n|
β
u
α
.
The Hookean bond energy per bond is
1
2
k(∆L
n
)
2
, where k is the bond spring constant (assumed
uniform on the lattice). Summing over bonds touching site x and dividing by 2 to avoid double-
counting:
L
elastic
(x) =
k
4
1
|n|
2
X
n∈N
n
α
n
β
n
γ
n
δ
β
u
α
δ
u
γ
=
k
4|n|
2
T
αβγδ
β
u
α
δ
u
γ
.
For D
4
, |n|
2
= 2 and T
αβγδ
= 4S
αβγδ
where S denotes the fully-symmetric isotropic tensor, so
L
elastic
(x) =
k
2
S
αβγδ
β
u
α
δ
u
γ
.
4.2 Expansion in strain and rotation
Decompose
β
u
α
= ϵ
αβ
+ ω
αβ
into symmetric strain and antisymmetric rotation,
ϵ
αβ
=
1
2
(
α
u
β
+
β
u
α
), ω
αβ
=
1
2
(
α
u
β
β
u
α
).
Expanding S
αβγδ
= δ
αβ
δ
γδ
+ δ
αγ
δ
βδ
+ δ
αδ
δ
βγ
:
S
αβγδ
β
u
α
δ
u
γ
= ( · u)
2
+ (
β
u
α
)(
β
u
α
) + (
β
u
α
)(
α
u
β
).
5
Substituting
β
u
α
= ϵ
αβ
+ ω
αβ
and using ϵ
αβ
ω
αβ
= 0:
(
β
u
α
)(
β
u
α
) = ϵ
αβ
ϵ
αβ
+ ω
αβ
ω
αβ
, (
β
u
α
)(
α
u
β
) = ϵ
αβ
ϵ
αβ
ω
αβ
ω
αβ
.
The rotational pieces cancel, leaving
S
αβγδ
β
u
α
δ
u
γ
= ( · u)
2
+ 2 ϵ
αβ
ϵ
αβ
.
Theorem 2 (D
4
elastic Lagrangian). The long-wavelength elastic Lagrangian on D
4
is
L
elastic
=
λ
2
( · u)
2
+ µ ϵ
αβ
ϵ
αβ
, λ = µ = k.
The Lamé parameters are equal, both given by the bond spring constant.
Corollary 1 (Elastic moduli in 4D). With λ = µ = k:
Bulk modulus K = λ + 2µ/D = 3k/2 in D = 4.
Poisson ratio ν = λ/[(D 1)λ + 2µ] = 1/5 in D = 4.
Longitudinal wave speed c
2
L
= (λ + 2µ) = 3k.
Transverse wave speed c
2
T
= µ/ρ = k/ρ.
Ratio c
L
/c
T
=
3.
Here ρ is the lattice mass density per unit cell.
The equality λ = µ is geometrically forced by the rank-four isotropy theorem: any lattice with
T
µνρσ
proportional to the unique fully-symmetric isotropic tensor automatically gives equal Lamé
parameters at the bond-stretch level. The D
4
lattice realizes this exactly; hypercubic and FCC
lattices do not.
5 Defects as Gravitational Sources
5.1 Pure-gauge nature of bare displacements
The displacement field u
µ
has four components in 4D; the symmetric metric perturbation h
µν
has
ten components. The two cannot be in one-to-one correspondence. The standard observation is
that under the linearized identification
h
µν
=
µ
u
ν
+
ν
u
µ
= 2 ϵ
µν
,
the metric perturbation h has exactly the form of a linearized coordinate transformation, which is
pure gauge in linearized gravity:
δh
µν
=
µ
ξ
ν
+
ν
ξ
µ
(gauge transformation, ξ arbitrary).
A pristine D
4
lattice with smooth displacement u
µ
therefore carries no gauge-invariant gravitational
content. The bond-stretch elastic energy is real and positive, but in the gravitational interpretation
it corresponds to gauge degrees of freedom.
6
5.2 Defects supply the gauge-invariant content
Following Kleinert [5] and the elasticity-to-gravity dictionary, the gauge-invariant gravitational con-
tent of the lattice is carried by topological defects: dislocations (which break translational continuity
of u) and disclinations (which break rotational continuity). The linearized Riemann curvature ten-
sor of the emergent metric is built from second derivatives of h
µν
, and the defect density gives a
gauge-invariant version of these second derivatives that does not vanish for a pristine lattice with
smooth deformations.
The trapped tetrahedral defect identified in the matter paper [1] is a localized configuration
where the lattice’s regular tetrahedral structure is broken by an extra node bonded to four FCC
sites. Such a defect is a source for the displacement field u in the surrounding lattice. The defect
is also the carrier of quark quantum numbers in the matter paper: charge, color, and confinement
properties. The same defect therefore plays two roles: as the matter content of the theory (via the
matter paper) and as the gravitational source (via the present paper).
5.3 Static defect strain: Kelvin solution
We consider a defect localized in the x
4
= 0 slice, with spatial location (x
1
, x
2
, x
3
) at the origin and
with the displacement field u
µ
(x
1
, x
2
, x
3
, x
4
) independent of x
4
. The x
4
direction here plays the role
of Euclidean time, and the static restriction projects onto time-translation-invariant configurations.
Under this restriction the 4D Navier equation
(λ + µ)
µ
( ·u) + µ u
µ
= j
µ
(where =
P
α
2
α
is the 4D Laplacian) splits into independent equations for the spatial components
u
i
(i = 1, 2, 3) and the time component u
4
. Since
4
u = 0, the operator reduces to the 3D
Laplacian
2
, and · u =
i
u
i
(the 3D divergence). The time-component equation becomes
µ
2
u
4
= j
4
, which is decoupled and not relevant for gravitational physics (it corresponds to a
longitudinal lattice translation in the time direction). The spatial equations
(λ + µ)
i
(
k
u
k
) + µ
2
u
i
= j
i
with λ = µ = k become
2k
i
(
k
u
k
) + k
2
u
i
= j
i
,
which is the standard Navier equation of 3D isotropic elasticity with the Lamé parameters extracted
in Theorem 2.
For a point defect at the origin with isotropic source strength F
i
, j
i
= F
i
δ
3
(r), the standard
Kelvin solution gives
u
i
(r) =
1
16πµ(1 ν)
(3 4ν)
δ
ij
r
+
x
i
x
j
r
3
F
j
.
With ν = 1/5 and µ = k (Corollary 1):
u
i
(r) =
1
16πk(4/5)
11
5
δ
ij
r
+
x
i
x
j
r
3
F
j
=
1
16πk
11
4
δ
ij
r
+
5
4
x
i
x
j
r
3
F
j
.
The leading long-distance behavior is u 1/r, equivalent to a Newton potential. Figure 1 visualizes
the strain field around the defect.
7
2 1 0 1 2
x
1
(lattice units)
2
1
0
1
2
x
3
(lattice units)
(A) Kelvin displacement field
u
(
r
) around a defect
tetrahedral
defect
F
def
10
2
10
1
|
u
(
r
)|
10
0
10
1
r
(lattice units)
10
3
10
2
10
1
|
u
(
r
)|
P
(B) Long-distance falloff: |
u
| 1/
r
matches Newton
D
4
Kelvin solution
1/
r
(Newton same slope)
1/
r
2
(steeper, for contrast)
Figure 1: Defect-induced strain field on D
4
. (A) Two-dimensional cross-section of the Kelvin
displacement field u(r) in the (x
1
, x
3
) plane around a static tetrahedral defect (cyan) sourcing a
body-force
F
def
(yellow). The background colormap shows the magnitude |u(r)| on a logarithmic
scale; white arrows show the displacement direction. The strain field is most intense near the
defect and decays radially. (B) Angle-averaged ⟨|u(r)|⟩ versus r on a log–log scale. The D
4
Kelvin
solution (solid blue) is parallel to the 1/r reference (dashed black), confirming the Newton-
potential scaling; a 1/r
2
reference (dotted red) is shown for contrast to make the slope visibly
distinct from a steeper power law. The Planck-scale lattice cutoff at r
P
is marked by the
gray dotted vertical. The defect (matter) and the strain field (gravity) come from the same lattice
configuration.
5.4 Identification with linearized Newton gravity
The map from elastic Kelvin solution to gravitational potential requires care, because for a smooth
u
µ
the metric perturbation h
µν
= 2ϵ
µν
is pure gauge (Section 5.1). The defect-induced Kelvin
displacement u
i
1/r, however, is singular at the defect location, and this singularity is what
makes it physical:
2
(1/r) = 4πδ
3
(r), so the strain field has a delta-function distributional
source at the defect location. The defect location is the support of gauge-invariant content; in the
Kleinert framework [5] this localized source is precisely a dislocation/disclination density that does
not vanish for the singular displacement.
We make the gravitational identification precise via the static Poisson equation. The trace of
the linearized Einstein equation in the Newtonian gauge gives
2
Φ = 4πG
N
ρ
M
,
where Φ = h
00
/2 is the gravitational potential and ρ
M
is the matter density. In the elasticity
picture, the static defect density ρ
def
acts as the source. Both equations have the same Green’s
function structure: Φ(r) 1/r in 3D.
The Kelvin solution displacement u F/(8πµ r) has strain ϵ F/(µr
2
), and its trace · u
F/(µr
2
). The defect-induced potential (built gauge-invariantly from second derivatives of h via the
linearized Ricci scalar) inherits the 1/r long-distance behavior, with proportionality
Φ(r)
F
def
µ r
,
8
where F
def
is the topological strength of the defect (units of force in elasticity language).
Matching F
def
/(µr) to G
N
M/r gives the order-of-magnitude identification (in natural units
= c = 1):
G
N
F
def
µ M
.
For a defect with topological strength F
def
k ·
P
(one bond-stretch quantum at the lattice scale)
and a Planck-scale mass density at the lattice site, and using µ = k in SSM-natural units, this gives
G
N
P
/M
P
2
P
(since
P
= 1/M
P
in natural units), recovering
G
N
2
P
1
M
2
P
.
This is the correct order of magnitude for Newton’s constant. Gravity is naturally weak in the SSM
framework for the simple reason that the substrate is stiff at the Planck scale: µ M
4
P
in natural
units.
The precise dimensionless prefactor in this identification requires fixing the defect-source-to-
mass conversion: how much body-force density F
def
does a baryon-defect source in the elastic
equilibrium equation, and how does this relate to the baryon’s rest mass. This is in principle
calculable from the matter paper’s structural counting [1], but a careful numerical determination
is left to follow-up work. The order-of-magnitude estimate is robust: G
N
comes out at the Planck
scale because the lattice’s only intrinsic scale is the Planck scale.
6 Distinguishing Features of the D
4
Construction
Three features of the D
4
construction distinguish the emergent-gravity picture here from related
approaches.
Exact SO(4) at every order. The rank-four isotropy theorem (Theorem 1) is exact, not asymp-
totic. Hypercubic lattice elasticity has cubic anisotropy at O(a
2
) (Proposition 1); D
4
has none.
The corresponding gravitational dispersion is exactly Lorentz-invariant at the linearized level after
Wick rotation x
4
ix
0
of the 4D Euclidean theory, with no expected (E/M
P
)
2
Lorentz-violation
signatures in gravitational-wave dispersion or graviton propagation. This parallels the gauge-sector
null Lorentz-violation prediction of [3].
Matter as defects, gravity as strain. The trapped tetrahedral defect of the matter paper [1]
plays simultaneously the role of (a) the matter content (carrying quark quantum numbers, mass,
and color charge) and (b) the source of long-distance strain (acting as a localized mass-energy
source for emergent gravity). The two roles are unified: matter and gravitational source are not
separately postulated. The same combinatorial structure that gives a baryon its mass-energy via
the matter paper’s counting also determines how much strain it produces in the surrounding D
4
lattice.
Planck-scale Newton constant. The lattice has a single intrinsic scale, the lattice spacing
a
P
. The bond stiffness k is Planck-scale by dimensional analysis. The emergent Newton
constant is therefore G
N
c/M
2
P
(equivalently G
N
2
P
c
3
/), matching the observed value.
This is not a derivation of the precise observed value, but a parameter-free order-of-magnitude
consistency: gravity is weak in the SSM framework because the substrate is stiff at the Planck
scale.
9
7 Conclusion
We have shown that the D
4
root lattice, established as physical four-dimensional spacetime in the
SSM framework [3], has an elastic structure that supports a linearized emergent-gravity interpreta-
tion. The rank-four bond tensor is exactly the fully-symmetric isotropic tensor, with no anisotropy
at any order in the lattice spacing. The long-wavelength elastic Lagrangian takes the standard
isotropic form with equal Lamé parameters λ = µ = k and Poisson ratio ν = 1/5. Bare displace-
ments correspond to gauge transformations of the linearized metric and carry no physical content;
the gauge-invariant gravitational content is sourced by lattice defects. The trapped tetrahedral
defects identified in the matter paper [1] as quarks act simultaneously as the matter content and as
localized gravitational sources, giving a Kelvin-form 1/r static strain field that matches the Newton
potential. The Newton constant works out to G
N
1/M
2
P
of the correct order of magnitude.
The construction is explicitly linearized and weak-field. What remains for further work: the
derivation of the full nonlinear Einstein-Hilbert action from the lattice (Sakharov-style integration
over bulk fields [7, 8] or a geometric reformulation), the precise dimensionless prefactor relating
defect strength to gravitational mass, gravitational radiation on D
4
, the cosmological-constant
problem, and the connection between strong-field strain configurations and the Schwarzschild-
like solutions of general relativity. These belong to the broader SSM program and to companion
analytical and numerical investigations.
Acknowledgments. This work builds on the FCC lattice studies of [1, 3, 4] and the broader
SSMTheory program.
Data availability. A Python script that verifies all numerical claims of this paper the rank-
four isotropy theorem, the comparison with hypercubic and FCC, the spatial/cross-slice decompo-
sition, the Lamé parameter extraction, the Poisson ratio and bulk modulus, and the dispersion
relations is publicly available at https://github.com/raghu91302/ssmtheory/blob/main/
verify_gravity.py. No other data were generated or analyzed in this study.
References
[1] R. Kulkarni, Matter as Incomplete Crystallization: Quark Charges, Color Confinement, and the Proton Mass
from a Single Extra Node in the Vacuum Lattice, Phys. Open (in press, 2026), doi:10.5281/zenodo.18917946.
[2] R. Kulkarni, The mass-energy-information equivalence: A bottom-up identification of the particle spectrum via
FCC lattice error correction, Phys. Open 27, 100414 (2026), doi:10.1016/j.physo.2026.100414.
[3] R. Kulkarni, D
4
as Physical Spacetime: Exact SO(4) Lattice QCD with Quarks as Tetrahedral Defects, SSMThe-
ory Group, IDrive Inc., Calabasas, CA (2026), doi:10.5281/zenodo.20142728.
[4] R. Kulkarni, A 67%-Rate CSS Code on the FCC Lattice: [[192,130,3]] from Weight-12 Stabilizers,
arXiv:2603.20294 [quant-ph] (2026).
[5] H. Kleinert, Gauge Fields in Condensed Matter, Vol. II: Stresses and Defects, World Scientific, Singapore (1989).
[6] A. J. Beekman, J. Nissinen, K. Wu, K. Liu, R.-J. Slager, Z. Nussinov, V. Cvetkovic, and J. Zaa-
nen, Dual gauge field theory of quantum liquid crystals in two dimensions, Phys. Rep. 683, 1 (2017),
doi:10.1016/j.physrep.2017.03.004.
[7] A. D. Sakharov, Vacuum quantum fluctuations in curved space and the theory of gravitation, Dokl. Akad. Nauk
SSSR 177, 70 (1967) [Sov. Phys. Dokl. 12, 1040 (1968)].
[8] M. Visser, Sakharov’s induced gravity: a modern perspective, Mod. Phys. Lett. A 17, 977 (2002), arXiv:gr-
qc/0204062.
[9] Verification script: #.
10