A controlled numerical laboratory for testing how entropy, quantum entanglement, and emergent gravity couple in a toy double-manifold system. This presentation explores a programmable testbed designed to probe the fundamental connections between information theory and gravitational physics—questions that have captivated physicists since the discovery of black hole thermodynamics.
Three interlinked mysteries remain at the heart of theoretical physics, challenging our understanding of how information, quantum mechanics, and gravity intertwine:
Where does information go when matter falls into a black hole? Does it vanish forever, violating quantum mechanics, or is it somehow preserved and eventually recovered through Hawking radiation?
How does a 3D bulk spacetime emerge from 2D boundary data? The holographic principle suggests that all the information in a volume can be encoded on its boundary surface.
Why is black hole entropy proportional to surface area rather than volume? This counterintuitive scaling, first discovered by Bekenstein and Hawking, hints at deep connections between gravity and thermodynamics.
Phylax provides a computational framework to test these ideas, building on decades of research establishing that entropy is encoded at the horizon.
The upper layer tracks entropy density S(x, y, t) and gravitational potential Φ(x, y, t). This manifold represents the emergent information structure and gravitational field that develops over time. It responds to the matter distribution below but doesn't directly "see" the quantum details.
The lower layer contains matter density ρ(x, y) serving as the gravitational source, plus a quantum field ϕq(x, y, t) representing entanglement structure. This is where the physical content lives—the "stuff" that creates gravity.


Each timestep applies a sequence of four operators that govern how the system evolves. This deterministic framework allows us to observe emergent behavior without imposing it by hand:
The potential evolves via Poisson relaxation: ∂Φ/∂t ∝ (4πGeff ρ − ∇²Φ). Entropy diffuses and grows: ∂S/∂t ∝ (∇²S + 0.1|∇Φ|² + 0.01 var(ϕq)), incorporating diffusion, geometric heating from potential gradients, and entanglement contributions.
The quantum field ϕq couples weakly to global entropy measures, creating feedback loops between local quantum correlations and the emergent gravitational structure. This captures how entanglement might influence spacetime geometry.
If total entropy S_total exceeds S_max (a boundary-area bound derived from holographic principles), the system rescales to enforce compliance. This ensures that the model respects information-theoretic constraints analogous to the Bekenstein bound.
At each step, we measure S_total, SH (horizon entropy), and AH (horizon area). These observables allow us to test whether area-law behavior emerges naturally from the dynamics.
This is a discrete, information-theoretic solver for emergent gravity—not a spacetime simulator in the traditional sense of numerical relativity.

We begin with a carefully chosen initial state that mimics the gravitational seed of a proto-black hole. The matter density follows a compact Gaussian distribution: ρ(x, y) ∝ exp(−r²/σ²), creating a localized gravitational source at the lattice center.
The quantum field ϕq starts with small random entanglement fluctuations—barely perceptible quantum noise that will later amplify through coupling to the gravitational field. Initially, entropy starts near zero across the entire lattice; the gravitational potential is then computed by solving Poisson's equation for this mass distribution.
The result is a small, isolated gravitational "seed" sitting in an otherwise empty lattice. Over time, this seed will develop a surrounding entropic halo as the coupled equations drive the system toward self-organization. This setup allows us to watch, step by step, how information structure emerges around a gravitational source.
As the Phylax system evolves, three remarkable phenomena emerge from the simple coupling rules. These observations suggest that the model captures essential features of how information and gravity interact:

At each timestep, we define a "horizon band" as the set of lattice cells where the gravitational potential exceeds a threshold: Φ ≥ α·Φmax. This operational definition allows us to track a surface analogous to a black hole's event horizon, even in our simplified 2D geometry.
Identify all cells where Φ ≥ α·Φmax (typically α = 0.5). This creates a contour that moves and deforms as the potential evolves.
Count the number of cells in the band. In 2D, this effectively measures the "circumference" of the horizon region.
Sum the entropy contained within all cells in the horizon band. This quantifies how much information is localized near the "surface."
When we plot SH versus AH over time, we observe transitions and plateaus. When the band coincides with the bright entropy ring, SH is high and varies slowly. When the band contracts into low-entropy regions, SH drops sharply. While not yet a clean linear relationship, this provides a controllable probe of how entropy localizes near an emergent horizon—a computational analog of the Bekenstein-Hawking area law.
This three-dimensional rendering captures the full geometric and information structure of the evolved Phylax system. The visualization reveals how entropy and gravitational potential create a layered, self-organized architecture.

The bright ring in warm tones (reds, oranges, yellows) shows where entropy has accumulated. Peak values exceed 40 per cell, concentrated in an annular region where the rate of entropy production ∂S/∂t is maximum.
The underlying gravitational potential Φ creates a "bowl" shape, shown in cool blues and purples. This field is nearly invisible compared to the bright entropy ring but defines the geometric structure that controls where the horizon band appears.
The cyan contour tracks the horizon band, marking where Φ ≥ 0.5·Φmax. This emergent surface arises naturally from the potential distribution and serves as our operational definition of the "event horizon."
The key message: information (entropy) self-organizes around the gravitational core in a ring-like structure rather than spreading uniformly. The horizon emerges naturally from the potential field, and entropy preferentially accumulates precisely at this location—just as black hole thermodynamics predicts.
How well does Phylax reproduce the fundamental properties of black hole thermodynamics and information theory? We can systematically compare theoretical predictions with model results:
Important caveat: This is a toy 2D model. Real black holes exist in 4D spacetime and involve Hawking radiation, information recovery through quantum extremal surfaces, and full general relativistic dynamics. However, the fundamental principle—that entropy and curvature co-evolve through local coupling rules—holds in Phylax and can be tested systematically.

Perhaps the most intriguing discovery from Phylax simulations is the monotone curve linking total entropy S_total to entanglement variance var(ϕq). This relationship, revealed by plotting one against the other across all timesteps, appears to be the model's first empirical "equation of state."
Physical interpretation: As the quantum field becomes more entangled -meaning its internal correlations strengthen the effective gravitational entropy must increase to maintain consistency with information-theoretic bounds. The system cannot become more entangled without also becoming more entropic.
Scaling behavior: The curve exhibits roughly polynomial growth (power-law-like behavior) rather than exponential scaling. This suggests a specific exponent relating information to geometry, potentially analogous to how entanglement entropy scales in conformal field theories.
The next critical step is to vary initial conditions, coupling strengths, lattice sizes, and other parameters to determine whether this relationship is universal a fundamental feature of how information and geometry couple or strongly dependent on model details.
Phylax runs in under one second on standard hardware. The fully deterministic evolution allows precise control over parameters and reproducible experiments—critical for systematic theory testing.
The model reveals how entropy and geometry can couple naturally without ad hoc tuning. The self-organized entropy ring and horizon band arise from simple local rules, not imposed structures.
Visual and numerical diagnostics provide detailed horizon-band analysis. We can track SH, AH, entanglement variance, potential gradients, and their correlations throughout evolution.
Every aspect can be modified: lattice size, coupling constants, initial conditions, operator ordering. This makes Phylax an ideal sandbox for testing theoretical ideas before attempting full simulations.
While Phylax offers valuable insights, it's essential to understand its limitations clearly. These constraints define the boundaries within which results should be interpreted:
The model operates in 2D spatial dimensions plus time, not the 3+1 dimensions of physical spacetime. There is no metric tensor, no proper geodesics, and no light cone structure. Curvature is represented indirectly through potential gradients.
The horizon band is defined by a threshold in the potential field (Φ ≥ α·Φmax), not by null surfaces or trapped surfaces as in general relativity. This is an approximation that captures some horizon-like behavior but lacks rigorous geometric meaning.
The model currently includes no mechanism for information recovery or black hole evaporation. Entropy only increases—there is no outgoing radiation that would begin to resolve the information paradox in the late-time evolution.
The 64×64 grid is small by computational standards. No continuum limit has been studied, so we cannot yet determine which behaviors are genuine physical effects versus numerical artifacts of discretization.
These limitations are not failures—they define Phylax as a toy model designed to isolate specific mechanisms. Understanding what the model omits is as important as understanding what it includes.
Implement frame-drag and tidal-force visualizations inspired by Thorne-Nichols work. This will reveal how the potential field creates spacetime curvature analogs that can be decomposed into physical components.
Seed gravitational wave analogs using Bessel functions and track how they propagate through and couple to the entropy ring. This tests how information responds to dynamic geometric perturbations.
Run simulations on larger lattices (128×128, 256×256) to investigate whether the area-law exponent and equation of state change with system size, approaching continuum predictions.
Explicitly enforce boundary-bulk entropy relationships from holographic duality. Test whether bulk entropy ≤ boundary entropy holds and how violations (if any) are corrected by the C operator.
For decades, theoretical and computational work has probed three interconnected frontiers:
These investigations have revealed profound connections but also persistent puzzles. The information paradox remains conceptually unresolved. The holographic principle suggests answers but lacks a complete dynamical framework. Full numerical relativity is powerful but computationally expensive and difficult to connect to quantum information theory.

Phylax offers a complementary angle: A fully deterministic, information-first laboratory where researchers can test whether area-law entropy emerges naturally from simple local rules, visualize how entanglement feeds into gravitational structure, and develop horizon-band diagnostics before applying them to full-scale simulations.
The vision is for Phylax to become both a teaching tool and a sandbox—much as earlier pedagogical work on Einstein's equations inspired decades of numerical relativity by making abstract concepts concrete and explorable.
Add geodesics, visualize light-cone-like structures around the horizon band, and implement proper null surface tracking to make the horizon definition more rigorous.
Conduct systematic parameter sweeps across coupling constants, lattice sizes, and initial conditions to identify which behaviors are universal versus model-dependent.
Explicitly encode AdS/CFT-inspired boundary-bulk entropy constraints and test whether the emergent dynamics naturally satisfy holographic bounds.
Engage with relativists, quantum information theorists, and numerical relativity groups to validate approaches, share techniques, and explore applications.
Phylax stands at the intersection of several research communities, each bringing essential expertise. Input from senior researchers can help refine the model and guide its evolution toward maximum physical relevance:
Are the evolution equations capturing the essential physics of entropy-geometry coupling? Do the operator definitions F, Q, C, and E map to meaningful physical processes, or are there conceptual gaps?
How would you extend Phylax toward a more realistic black hole model? What are the most important missing ingredients—metric dynamics, fermion fields, quantum corrections, causal structure?
What additional diagnostics would be most valuable? Should we focus on information-theoretic measures (mutual information, entanglement entropy), geometric quantities (Ricci scalar analogs), or thermodynamic properties (temperature, chemical potential)?
These questions are not rhetorical. Phylax is designed to be a collaborative platform—a tool that improves through dialogue between theory, computation, and phenomenology.
Phylax builds directly on decades of theoretical insights into black hole physics, quantum information, and spacetime geometry. Understanding these foundations clarifies what the model aims to test:
The proportionality of black hole entropy to horizon area, S = A/4G, established that gravity has thermodynamic properties. Phylax tests whether this area law can emerge from first principles in a coupled system.
Hawking radiation suggests information is lost, violating quantum mechanics. Phylax doesn't yet model radiation but sets the stage by showing how entropy localizes—a prerequisite for later information recovery mechanisms.
The idea that physics in a volume can be encoded on its boundary. Phylax's C operator enforces a holographic bound, testing whether dynamics naturally respect this constraint.
The deep connection between quantum entanglement and spacetime connectivity. Phylax's Q operator implements entanglement feedback, allowing us to observe how information structure influences emergent geometry.
Techniques for visualizing spacetime curvature through tidal and frame-drag fields. Future Phylax versions will adapt these methods to make the emergent "curvature" visible and intuitive.
Beyond research applications, Phylax is envisioned as an educational platform and collaborative sandbox that makes abstract ideas concrete. The model's strengths—speed, visualization, parameter control—make it ideal for several purposes:
Students can modify coupling constants, visualize entropy evolution in real-time, and test predictions from general relativity and quantum information theory without the overhead of full numerical relativity codes.
Researchers can prototype new ideas—different horizon definitions, alternative entanglement measures, novel coupling schemes—and see results within seconds, enabling fast iteration.
By providing a common computational framework, Phylax can facilitate conversations between relativists, quantum information theorists, and condensed matter physicists studying emergent spacetime.
The long-term goal is to build a community around information-theoretic models of gravity, where Phylax serves as both a research tool and a pedagogical resource—much as earlier simplified models helped establish intuition that later guided full simulations.
A 2D lattice model coupling entropy, gravitational potential, matter density, and quantum entanglement through four evolution operators: F (geometric), Q (entanglement), C (holographic control), and E (diagnostics).
Two layers—geometry/information above, matter/quantum fields below—interact through Poisson relaxation and entanglement feedback, allowing emergent behavior without explicit fine-tuning.
Entropy concentrates in a bright ring around the compact gravitational core, precisely where |∇Φ|² is maximum, demonstrating localization near an emergent horizon analog.
Operational definition (Φ ≥ α·Φmax) enables systematic testing of area-law behavior by tracking SH versus AH throughout evolution—preliminary but promising results.
The smooth, monotone relationship Stotal(var(ϕq)) reveals how entanglement and gravitational entropy couple, suggesting a fundamental connection that transcends model details.
Fast, deterministic, and fully controllable—Phylax provides a computational laboratory for exploring emergent gravity, testing holographic principles, and developing diagnostic tools before applying them to full-scale simulations.
Phylax builds on foundational work spanning general relativity, black hole thermodynamics, quantum information theory, and holography. Key references that inform the model's design and interpretation:
Complete simulation code, parameter files, visualization scripts, and documentation are available upon request. All simulations run in Python 3.9+ with NumPy, Matplotlib, and SciPy. The codebase is designed for easy modification and extension.
Contact for collaboration, questions, or access to code: Phylax is an open research project welcoming input from the broader physics community.