# Contents

## Idea

In quantum field theory a quantum state is called quasi-free if

1. its n-point functions are non-vanishing only for even $n$;

2. its 2-point function determines all its $n$-point functions.

This reflects the structure of the Wick algebra of quantum observables for the free field.

## References

• Marek Radzikowski, p. 4 of Micro-local approach to the Hadamard condition in quantum field theory on curved space-time, Commun. Math. Phys. 179 (1996), 529–553 (Euclid)

• Igor Khavkine, Valter Moretti, section 2.4 of Algebraic QFT in Curved Spacetime and quasifree Hadamard states: an introduction, Chapter 5 in Romeo Brunetti et al. (eds.) Advances in Algebraic Quantum Field Theory, Springer, 2015 (arXiv:1412.5945)

Last revised on August 5, 2017 at 11:02:24. See the history of this page for a list of all contributions to it.