# Multicritical Infection Spreading

## TL;DR

This paper investigates the multicritical behavior of the disordered contact process, revealing universal properties and activated dynamical scaling, and establishing its connection to the multicritical quantum Ising model.

## Contribution

It uncovers the universal multicritical behavior of the disordered contact process and links it to the quantum Ising model universality class.

## Key findings

- Universal multicritical behavior observed in 2D and 3D.
- Activated dynamical scaling with exponents matching strong disorder RG predictions.
- Connection established between classical multicritical contact process and quantum Ising model.

## Abstract

The contact process is a simple infection spreading model showcasing an out-of-equilibrium phase transition between a macroscopically active and an inactive phase. Such absorbing state phase transitions are often sensitive to the presence of quenched disorder. Traditionally, a phase transition in the disordered contact process is either triggered by dilution or by locally varying the infection rate. However, when both factors play an important role, a multicritical point emerges that remains poorly understood. Here, we study the multicritical contact process by large-scale Monte Carlo simulations in two and three dimensions. The multicritical behavior is found to be universal and exhibits ultra-slow, activated dynamical scaling, with exponents consistent with those predicted by the strong disorder renormalization group method. This finding indicates that the multicritical contact process belongs to the same universality class as the multicritical quantum Ising model, opening future directions to measure quantum entanglement properties via classical simulations.