The effects of SUSY on the emergent spacetime in the Lorentzian type IIB matrix model

TL;DR

This paper investigates how supersymmetry influences the emergence of spacetime in the Lorentzian type IIB matrix model, showing that fermionic effects may lead to a realistic 3+1-dimensional universe.

Contribution

It demonstrates that including fermionic contributions in the model can result in the emergence of a 3+1-dimensional spacetime, addressing artifacts seen when fermions are omitted.

Findings

Spontaneous symmetry breaking artifacts are eliminated with proper Lorentz frame choice.

Fermionic effects suggest the emergence of a smooth 3+1-dimensional spacetime.

A (1+1)-dimensional spacetime appears when fermions are omitted.

Abstract

The Lorentzian type IIB matrix model is a promising candidate for a nonperturbative formulation of superstring theory. Recently we performed complex Langevin simulations by adding a Lorentz invariant mass term as an IR regulator and found a (1+1)-dimensional expanding spacetime with a Lorentzian signature emerging dynamically at late times when the fermionic contribution is omitted. Here we find that this is merely an artifact of the Lorentz boosts by showing that the spontaneous breaking of rotational symmetry is eliminated if one chooses a Lorentz frame appropriately. On the other hand, when we include the fermionic contribution, we find some evidence suggesting the emergence of a smooth (3+1)-dimensional expanding Lorentzian spacetime.