Sir Anthony James Leggett (26 March 1938 – 8 March 2026) was a British–American theoretical physicist and professor at the University of Illinois Urbana-Champaign (UIUC).<a href="https://en.wikipedia.org/wiki/Anthony_Leggett#cite_note-:0-4"><span>[</span>4<span>]</span></a> Leggett was widely recognised as a world leader in the theory of low-temperature physics, and his pioneering work on superfluidity was recognised by the 2003 Nobel Prize in Physics.<a href="https://en.wikipedia.org/wiki/Anthony_Leggett#cite_note-nobelprize-5"><span>[</span>5<span>]</span></a> He shaped the theoretical understanding of normal and superfluid helium liquids and strongly coupled superfluids.<a href="https://en.wikipedia.org/wiki/Anthony_Leggett#cite_note-6"><span>[</span>6<span>]</span></a> He set directions for research in the quantum physics of macroscopic dissipative systems and use of condensed systems to test the foundations of quantum mechanics.<a href="https://en.wikipedia.org/wiki/Anthony_Leggett#cite_note-7"><span>[</span>7<span>]</span></a><a href="https://en.wikipedia.org/wiki/Anthony_Leggett#cite_note-8"><span>[</span>8<span>]</span></a>