C^1-Classification of gapped parent Hamiltonians of quantum spin chains with local symmetry

TL;DR

This paper classifies gapped quantum spin chain Hamiltonians with local symmetry by showing that $C^1$-equivalence corresponds to unitary equivalence of their projective symmetry representations.

Contribution

It establishes a $C^1$-classification scheme for gapped Hamiltonians based on the unitary equivalence of their associated projective symmetry representations.

Findings

Hamiltonians are $C^1$-equivalent iff their projective representations are unitarily equivalent.

Provides a classification framework for gapped Hamiltonians with local symmetry.

Connects topological properties of Hamiltonians to symmetry representation theory.

Abstract

We consider the family of gapped Hamiltonians introduced in [FNW] on the quantum spin chains $\bigotimes_{\mathbb Z}\mathop{\mathrm{M}}\nolimits_n$, with local symmetry given by a group $G$. The $G$-symmetric gapped Hamiltonians are given by triples $(k,u,V)$, where $u$ is a projective unitary representation of $G$ on a finite dimensional space ${\mathbb C}^k$, and $V$ is an isometry from ${\mathbb C}^k$ to ${\mathbb C}^n\otimes {\mathbb C}^k$. We show that Hamiltonians $H_0,H_1$, given by the triples $(k^{(0)}, u^{(0)}, V^{(0)})$ and $(k^{(1)}, u^{(1)}, V^{(1)})$ are $C^1$-equivalent if the projective representations $u^{(0)}$ and $u^{(1)}$ are unitary equivalent.