# Composite Structure and Causality

## TL;DR

This paper investigates whether composite particle structures can cause observable non-locality and causality violations at high energies, using a model-independent approach based on Bogoliubov-Shirkov causality formulation.

## Contribution

It introduces a causal consistency condition for derived theories of composite particles and analyzes scenarios that satisfy or violate this condition.

## Key findings

- Identifies conditions under which causality is preserved or violated in composite models.
- Provides a framework to analyze causality in theories with elementary constituents.
- Discusses how causality-violating amplitudes can emerge in such theories.

## Abstract

We study the question of whether a composite structure of elementary particles, with a length scale $1/\Lambda$, can leave observable effects of non-locality and causality violation at higher energies (but $\lesssim \Lambda$). We formulate a model-independent approach based on Bogoliubov-Shirkov formulation of causality. We analyze the relation between the fundamental theory (of finer constituents) and the derived theory (of composite particles). We assume that the fundamental theory is causal and formulate a condition which must be fulfilled for the derived theory to be causal. We analyze the condition and exhibit possibilities which fulfil and which violate the condition. We make comments on how causality violating amplitudes can arise.