Directional Goldstone waves in polariton condensates close to equilibrium oleh Dario Ballarini, Davide Caputo, Galbadrakh Dagvadorj, Richard Juggins, Milena De Giorgi, Lorenzo Dominici, Kenneth West, Loren N. Pfeiffer, Giuseppe Gigli, Marzena H. Szymańska, Daniele Sanvitto