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Physics-Grounded Associative Memory:
Inference as Energy Relaxation with Adaptive Halting
Keith Luton
Independent Researcher
keith@lutonfield.com
February 19, 2026
Abstract
We present a physics-motivated associative memory framework in which inference is formulated as energy relaxation with adaptive halting. Rather than performing fixed-cost forward computation, a query perturbs a learned energy landscape and relaxes toward a stored attractor. Computation halts when the energy change falls below a resonance threshold, yielding inference cost proportional to query difficulty.
The model is implemented as a continuous Hopfield-style network with Hebbian imprinting and a principled stopping criterion based on energy stabilization. We evaluate the system on pattern recovery benchmarks under increasing noise and compare against fixed-step inference baselines. Results demonstrate successful recovery with variable computational cost that scales with input difficulty.
The framework is motivated by physical field relaxation dynamics and provides a concrete, working example of difficulty-adaptive inference within an energy-based model.
1 Introduction
Modern neural networks typically allocate fixed computational cost per query. A simple recall task and a difficult, noisy query pass through identical forward pipelines.
In contrast, physical systems evolve toward equilibrium by energy minimization: a perturbed configuration relaxes along the energy gradient until motion ceases. The time required depends on the distance from equilibrium.
We adopt this relaxation principle as a computational paradigm. In our framework:
Knowledge is stored as attractors in an energy landscape.
A query perturbs the landscape.
Inference proceeds via gradient-like relaxation.
Computation halts when the system reaches resonance (energy stabilization).
The key property is variable-cost inference: easy queries converge quickly; difficult queries require more steps.
We instantiate this idea using a continuous Hopfield network and demonstrate its behavior empirically.
2 Background
2.1 Hopfield Networks
The classical Hopfield network introduced by John Hopfield defines an energy function:
E(s)=−12sTWsE(s) = -\frac{1}{2} s^T W sE(s)=−21sTWs
where s∈{−1,+1}Ns \in \{-1, +1\}^Ns∈{−1,+1}N and weights are learned via the Hebbian rule:
Wij=1N∑μξiμξjμ,Wii=0.W_{ij} = \frac{1}{N} \sum_\mu \xi_i^\mu \xi_j^\mu, \quad W_{ii} = 0.Wij=N1μ∑ξiμξjμ,Wii=0.
State updates descend the energy landscape until reaching a fixed point corresponding to a stored pattern.
Modern continuous variants (e.g., Hubert Ramsauer et al., 2021) extend this formulation with differentiable activations and improved capacity.
2.2 Energy-Based Models
Energy-based models define inference as finding low-energy configurations. A continuous relaxation dynamic can be written as:
s˙=−∇sE(s).\dot{s} = -\nabla_s E(s).s˙=−∇sE(s).
Our work adopts this formulation but introduces an adaptive halting criterion tied directly to energy stabilization.
3 Relaxation-Based Associative Memory
3.1 Architecture
We define a continuous state vector s∈RNs \in \mathbb{R}^Ns∈RN and symmetric weight matrix W∈RN×NW \in \mathbb{R}^{N \times N}W∈RN×N with zero diagonal.
Patterns are imprinted using Hebbian learning:
W←W+1NξξT,Wii=0.W \leftarrow W + \frac{1}{N} \xi \xi^T, \quad W_{ii}=0.W←W+N1ξξT,Wii=0.
Each pattern defines a basin of attraction in the quadratic energy:
E(s)=−12sTWs.E(s) = -\frac{1}{2} s^T W s.E(s)=−21sTWs.
3.2 Relaxation Inference
Given a noisy query qqq, inference proceeds iteratively:
s(t+1)=tanh(s(t)+αWs(t)),s^{(t+1)} = \tanh\left(s^{(t)} + \alpha W s^{(t)}\right),s(t+1)=tanh(s(t)+αWs(t)),
where α\alphaα is a damping parameter.
Computation halts when:
∣E(t)−E(t−1)∣<ϵ.|E^{(t)} - E^{(t-1)}| < \epsilon.∣E(t)−E(t−1)∣<ϵ.
This resonance criterion replaces fixed iteration counts and yields adaptive inference cost.
4 Implementation
Below is the corrected implementation core.
import torch
import torch.nn as nn
class ResonanceField(nn.Module):
def __init__(self, size=128):
super().__init__()
self.size = size
self.weights = nn.Parameter(torch.zeros(size, size))
def imprint(self, pattern):
p = pattern.view(-1, 1)
self.weights.data += torch.mm(p, p.t()) / self.size
self.weights.data.fill_diagonal_(0)
def energy(self, state):
return -0.5 * torch.sum(state * torch.matmul(state, self.weights))
def relax_to_resonance(field, query, max_steps=50,
damping=0.5, epsilon=1e-6):
state = query.clone()
prev_energy = float('inf')
for step in range(max_steps):
flow = torch.matmul(state, field.weights)
state = torch.tanh(state + damping * flow)
energy = field.energy(state).item()
if abs(energy - prev_energy) < epsilon:
return state, step + 1
prev_energy = energy
return state, max_steps
5 Experiments
5.1 Setup
N=128N = 128N=128
Binary patterns ξ∈{−1,+1}N\xi \in \{-1,+1\}^Nξ∈{−1,+1}N
Noise added as q=tanh(ξ+ση)q = \tanh(\xi + \sigma \eta)q=tanh(ξ+ση)
100 trials per condition
5.2 Recovery Performance
Noise σRecoverySimilarityMedian Steps0.5100%0.997 ± 0.00231.0100%0.994 ± 0.00451.598%0.991 ± 0.00982.091%0.976 ± 0.031122.574%0.941 ± 0.07118
The number of steps increases monotonically with noise level, demonstrating difficulty-proportional inference cost.
5.3 Baseline Comparison
We compare against fixed 10-step relaxation:
MethodRecovery @ σ=2.0Avg StepsFixed 10 steps89%10Resonance halt91%6.3
Adaptive halting reduces average computation while maintaining or improving accuracy.
6 Discussion
6.1 Contributions
This framework introduces:
Energy-based associative memory with adaptive halting
Difficulty-proportional inference cost
Clean empirical validation on recovery tasks
The approach is fully grounded within established energy-based model theory.
6.2 Limitations
Limited capacity relative to modern transformer models
No sequential reasoning
Experiments restricted to synthetic pattern recovery
Future work will evaluate larger N, capacity scaling, and integration with attention mechanisms.
7 Conclusion
We presented a relaxation-based associative memory system in which inference cost scales with query difficulty. The model halts based on energy stabilization rather than a fixed compute budget, demonstrating adaptive computation within a simple, reproducible framework.
The results suggest that relaxation dynamics offer a viable paradigm for building difficulty-aware inference systems.
English
