Scrutinizing the pion condensed phase

Understand

When the isospin chemical potential exceeds the pion mass, charged pions condense in the zero-momentum state forming a superfluid.

• Chiral perturbation theory provides a very powerful tool for studying this phase.
• However, the formalism that is usually employed in this context does not clarify various aspects of the condensation mechanism and makes the identification of the soft modes problematic.
• We re-examine the pion condensed phase using different approaches within the chiral perturbation theory framework.