Physical law and the quest for mathematical understanding

The theoretical physics of the first quarter of the twentieth century —centering around relativity theory and nonrelativistic quantum mechanics—has had a broad influence mathematically. The main achievement of theoretical physics in the following half-century was the development of quantum field theory or QFT. Yet the mathematical influence of QFT still belongs largely to the <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="21 Superscript s t"> <mml:semantics> <mml:msup> <mml:mn>21</mml:mn> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi>s</mml:mi> <mml:mi>t</mml:mi> </mml:mrow> </mml:msup> <mml:annotation encoding="application/x-tex">21^{st}</mml:annotation> </mml:semantics> </mml:math> </inline-formula> century, because its mathematical foundations are still not well-understood.