# The ground state-vector of the XY Heisenberg chain and the Gauss decomposition

## TL;DR

This paper derives an exact group-theoretical expression for the ground state-vector of the XY Heisenberg spin chain in fermion representation, facilitating advanced analysis of its correlation functions.

## Contribution

It provides a novel exact formula for the ground state-vector using group theory, enabling deeper study of correlation functions in the XY model.

## Key findings

- Exact expression for the ground state-vector derived
- Facilitates combinatorial analysis of correlation functions
- Enhances understanding of the XY Heisenberg chain

## Abstract

The XY Heisenberg spin 1/2 chain is considered in the fermion representation. The construction of the ground state-vector is based on the group-theoretical approach. The exact expression for the ground state-vector will allow to study the combinatorics of the correlation functions of the model.