# Self-supervised Learning with Physics-aware Neural Networks I: Galaxy Model Fitting

## TL;DR

This paper introduces a self-supervised hybrid neural network that integrates physical models to estimate parameters of galaxy light profiles without requiring true parameter labels, enabling physically interpretable unsupervised learning.

## Contribution

It presents a novel semantic autoencoder architecture combining neural networks with physical models for unsupervised parameter estimation in galaxy modeling.

## Key findings

- Successfully performs 2D galaxy light profile fitting
- Estimates physically meaningful parameters without supervision
- Maintains neural network robustness with explicit physical modeling

## Abstract

Estimating the parameters of a model describing a set of observations using a neural network is in general solved in a supervised way. In cases when we do not have access to the model's true parameters this approach can not be applied. Standard unsupervised learning techniques on the other hand, do not produce meaningful or semantic representations that can be associated to the model's parameters. Here we introduce a self-supervised hybrid network that combines traditional neural network elements with analytic or numerical models which represent a physical process to be learned by the system. Self-supervised learning is achieved by generating an internal representation equivalent to the parameters of the physical model. This semantic representation is used to evaluate the model and compare it to the input data during training. The Semantic Autoencoder architecture described here shares the robustness of neural networks while including an explicit model of the data, learns in an unsupervised way and estimates, by construction, parameters with direct physical interpretation. As an illustrative application we perform unsupervised learning for 2D model fitting of exponential light profiles.