Erwin Rudolf Josef Alexander Schrödinger (UK: /ˈʃrɜːdɪŋər/, US: /ˈʃroʊ-/; German: [ˈɛɐ̯vɪn ˈʃʁøːdɪŋɐ]; 12 August 1887 – 4 January 1961), sometimes written as Erwin Schroedinger or Erwin Schrodinger, was a Nobel Prize-winning Austrian physicist with Irish citizenship who developed a number of fundamental results in quantum theory: the Schrödinger equation provides a way to calculate the wave function of a system and how it changes dynamically in time.