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Causal order and local propagation: SMM/DTT and Emergent and entropic gravity

Can a source without spatial position generate a stable notion of neighborhood and a finite speed of influence between completed records? This article compares the source-based construction with Emergent and entropic gravity, identifies their strongest point of contact, and works through a concrete example that separates a valid mathematical result from the further physical relation needed to explain observations.

In this article
  1. The question that matters
  2. The SMM/DTT contribution
  3. How Emergent and entropic gravity frames the problem
  4. Where the mechanisms agree and differ
  5. Worked example: assumptions, calculation and result
  6. An independent operational check
  7. What follows from the comparison
Key ideas · Continue on SMONAD

01The question that matters

Causal order and spatial proximity encode different information. A causal relation states which events can influence which others. A spatial distance compares records on an appropriate common slice or through a relational protocol. A graph can have a finite propagation speed relative to its edges while still being physically nonlocal if those edges join arbitrarily distant readouts.

Locality therefore has two stages: the interaction structure must be generated, and the dynamics must respect that structure. An inequality bounding propagation on an already chosen graph addresses the second stage. It does not explain why that graph resembles three-dimensional space. This separation makes the challenge sharper and gives partial achievements a clear place in the overall reconstruction. [1] [2]

02The SMM/DTT contribution

The Single Monad is nonspatial, so its alleged unity cannot be represented as a point that sends ordinary signals from a hidden location. In DTT, locality would belong to the relations among completed records. The six inner levels could produce and retain a neighborhood structure; outer time would order observable influence through that structure.

A single controller is not enough to explain locality if it is allowed to update any record pair independently. A stronger rule lets the same retained relations restrict both record formation and later transport. Then memory is physically important: it preserves which comparisons count as nearby, rather than being an inert log appended after spatial interactions have already been assumed.

Geometry, clocks and propagation as independent readouts
Geometry, clocks and propagation as independent readouts. A single source model should explain the relation between separately defined measurements. Sharing a diagram does not impose that relation. View full size ↗

03How Emergent and entropic gravity frames the problem

Thermodynamic and entropic approaches ask whether gravitational equations describe collective information or entropy response. Jacobson's local-horizon argument and Verlinde's entropic-force proposal are distinct constructions, with different assumptions and scopes. Their common lesson is that a familiar gravitational equation can emerge conditionally from nongeometric-looking inputs.

For DTT this creates an attractive bridge from retained histories to macroscopic geometry. However, an entropy count, a temperature and an energy normalization are physical ingredients that need justification. The comparison is strongest when a temporal model explains one of those ingredients and weakest when it simply imports all of them under the name of completion. [3] [4]

04Where the mechanisms agree and differ

An entropy gradient can define a force in a model without specifying how influences propagate between spatially separated systems. This is the central limitation when comparing entropic gravity with DTT locality. A static relation may be reproduced even if the underlying dynamics has no acceptable causal cone. Temporal generation is potentially helpful because it places the production and ordering of records at the center of the model.

To realize that advantage, the source must derive a neighborhood structure and restrict influence through it. A global entropy maximization performed instantaneously across arbitrary records would not explain local propagation, even if its equilibrium states resemble gravity. The six nested inner levels could instead implement bounded local operations and retain their relational dependencies. The circuit and Hamiltonian examples below illustrate the difference between an exact update cone and an exponentially suppressed influence tail. Either can be a useful effective description, but its physical length and clock units must be derived. The strongest bridge would combine an entropic equilibrium law with source-generated causal dynamics, so that the same model explains both the static gravitational response and how changes in that response travel. [3] [4]

05Worked example: assumptions, calculation and result

On a chain with nearest-neighbor updates, suppose a disturbance can cross at most one edge of length a during each completed interval δτ. A record N edges away cannot respond before Nδτ, giving an exact circuit cone with v=a/δτ. This uses a bounded-depth update with strictly local gates.

Continuous-time Hamiltonians generally give a different result: a Lieb–Robinson estimate bounds a distant commutator by a constant times exp[−μ(d−vt)]. The tail is small rather than exactly zero outside the effective cone. If d−vt=10/μ, the exponential factor is about 4.54×10⁻⁵. Neither result determines a physical speed until the edge length and the clock interval are independently identified. Nor does either prove that the source generated the chain. [1] [2]

Tₘᵢₙ=Nδτ; d=Na; v=a/δτ. A Hamiltonian bound has the form ‖[A(t),B]‖≤C e^(−μ(d−vt)).

d and a are physical distances only after readout calibration; μ has inverse-distance units. C depends on observables and interaction assumptions.

06An independent operational check

A neighborhood rule can also fail through rare long links. Suppose almost all edges connect nearby records but a small fraction join distant regions. A short graph path may then connect points that appear far apart in the geometric readout. The propagation bound remains valid in graph distance while failing to express the intended physical locality. A source law must therefore constrain the relation between graph distance and measured distance, not merely the number of edges crossed per update. This gives a precise role to retained memory: it can preserve compatible neighborhood relations and prevent later operations from introducing unaccounted shortcuts.

07What follows from the comparison

This comparison suggests a strong attainable result: a joint theorem for neighborhood retention and propagation under one autonomous update. It would explain why a spatially organized record persists and why perturbations remain confined to its effective cone. That is more informative than postulating all-to-all generation followed by a local outer description, because it identifies the actual mechanism suppressing observable nonlocal shortcuts.

THE SAME QUESTION, DIFFERENT STARTING POINTS

The comparison at a glance

QuestionSMM/DTTEmergent and entropic gravity
Starting physical structureOne nonspatial source; six nested inner functional levels produce records accessible through outer completion.Collective entropy and information variables in a specified thermodynamic construction.
The central mechanism in this topicLocal operations and retained dependencies should generate the propagation law.An entropy-force relation needs additional dynamics to determine causal response.
How the claim is made operationalA source-to-record map must define geometry, material response and physical clocks with shared inputs.Entropy-response laws, energy/temperature assignments and effective gravitational relations.
Meaning of agreementAgreement is a compatibility result; a source-selected relation or fixed residual would add explanatory content.The stated framework provides a benchmark within its own assumptions and established domain.

KEEP THE CONNECTION

Key ideas

  • A causal dynamical completion is the main contribution DTT could add to a static entropic construction.
  • The worked example establishes only the result stated under its explicit assumptions.
  • Six nested inner levels describe one generative organization; outer time orders accessible completion.

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Sources and further reading

References support the comparator and the specific mathematical or interpretive claims indicated. SMM/DTT connections are developed in the analysis above.

  1. Bruno Nachtergaele and Robert Sims, Lieb-Robinson Bounds and the Exponential Clustering Theorem (2006) ↗Peer-reviewed mathematical bounds for local quantum interactions on metric sets; locality assumptions precede the bound.
  2. Sumati Surya, The causal set approach to quantum gravity (2019) ↗Peer-reviewed Living Reviews article: locally finite partial orders, Lorentz-invariant sprinkling, dimension and continuum reconstruction.
  3. Ted Jacobson, Thermodynamics of Spacetime: The Einstein Equation of State (1995) ↗Peer-reviewed derivation conditional on local horizon thermodynamics, area entropy and the Clausius relation.
  4. Erik Verlinde, On the Origin of Gravity and the Laws of Newton (2010/2011) ↗Published entropic-gravity proposal; entropy, temperature and screen assumptions are separate physical inputs.

How these comparisons distinguish premises, results and physical claims

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