What theory is De Witt Lee Sumners known for his research? Use the text attached to give me the answer.

De Witt Lee Sumners is an American mathematician, having been the Robert O. Lawton Distinguished Professor at Florida State University.[1][2] He is known for his research in knot theory, topological fluid dynamics, and their application to DNA.[3]

Sumners earned his Ph.D. in 1967 from the University of Cambridge under the supervision of John F. P. Hudson.[4] He retired in 2007, and became a professor emeritus. In 2012, he was named as one of the inaugural Fellows of the American Mathematical Society.[5]
system
apane shodh ke liye de vit lee samars kis siddhant ko janaa jaataa he?mujhe jawaab dene ke liye sanlagn paath kaa upyog karen.

di vit lee.vah gaanth siddhant, topological drav gatishiltaa or diene ke liye unke aavedan main apane shodh ke liye jane jate hai. [3]

Sumners ne apni piech.di.1967 main jon epa. pi. hadsan kii dekharekh main cambridge vishvavidhyalay se. [4]vah 2007 main sevanivrutt hue, or professor ameritas ban gaye.2012 main, unhen america ganitiya samaaj ke udghaatan adhyetaon main se ek ke rup main namit kiya gaya tha. [5]
user
di vit le shamars ko gaanth siddhant or topological fluid dianemics or diene ke liye unke aavedan par shodh karne ke liye janaa jaataa he.
assistant
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</s>
<|user|>
apane shodh ke liye de vit lee samars kis siddhant ko janaa jaataa he?mujhe jawaab dene ke liye sanlagn paath kaa upyog karen.

di vit lee.vah gaanth siddhant, topological drav gatishiltaa or diene ke liye unke aavedan main apane shodh ke liye jane jate hai. [3]

Sumners ne apni piech.di.1967 main jon epa. pi. hadsan kii dekharekh main cambridge vishvavidhyalay se. [4]vah 2007 main sevanivrutt hue, or professor ameritas ban gaye.2012 main, unhen america ganitiya samaaj ke udghaatan adhyetaon main se ek ke rup main namit kiya gaya tha. [5]</s>
<|assistant|>
di vit le shamars ko gaanth siddhant or topological fluid dianemics or diene ke liye unke aavedan par shodh karne ke liye janaa jaataa he.</s>
