Research

 

My interest in research unknowingly began in WPI’s recreational mathematics course, where I was handed a preprint of a paper written by the instructor’s colleague. The paper described a method for directly evaluating terms in the Calkin-Wilf sequence, a list which includes each reduced rational number exactly once. I read the paper and was fascinated by its ideas. A year later, I returned to the paper and found that the author left an open question: given a reduced fraction, how does one determine its position in the sequence? This question asks the converse of what the paper achieved, which was to determine the reduced fraction at a given position in the sequence. Shortly after, I developed a solution using continued fractions. But notably, the method was reversible and solved the original problem as well! With encouragement from the paper’s author and with direction from my advisors, I refined the method and wrote a paper. My original research is now proudly published in the peer-reviewed Pi Mu Epsilon Journal.

I fell in love with my research and developed new results. By establishing the connection between the Calkin-Wilf tree and continued fractions, I studied irrational numbers, particularly those with periodic continued fractions, using the properties of the Calkin-Wilf tree. The link also explains some mysterious results, for example, why the continued fractions of square root numbers have coefficients that form palindromes. Soon after, a correspondence is revealed between periodic continued fractions and matrices in the special linear group. All this was very exciting!

I am honored to share that the Mathematical Sciences Department at WPI recognized my research and granted my project the Provost's MQP Award. For a full writeup of my research results, please visit the project on Digital WPI.

The Calkin-Wilf Tree - Theme and Variations.pdf

Documenting my Research on YouTube

To make my research accessible, I have been working to organize the content into short animated videos that are published on YouTube. Over time, I plan to produce more mathematical content in this style and upload it to this channel. Below are the first three videos in the series "Listing the Rationals using Continued Fractions."

Listing the Rationals using Continued Fractions Part 1

This video motivates the series with a prompt: "Can you make a list of the rationals, where each number appears exactly once?" The Calkin-Wilf tree offers a surprisingly methodical way to make such a list. We learn that the rationals in the tree are organized by the Euclidean algorithm, which corresponds with the process of generating continued fractions. This connection produces a two-way algorithm for computing and locating terms in the rational list. Then, we find a natural way to extend the Calkin-Wilf tree to include all of the rational numbers— positive, negative, and zero. This has consequences for the listing algorithm. Finally, we make a connection to the Fibonacci numbers and the golden ratio.

Listing the Rationals using Continued Fractions Part 2

This video provides rigor to the ideas from the first video. We verify the essential properties of the Calkin-Wilf tree, as well as its correspondence with continued fractions. Applications to irrational numbers are explored, including the golden ratio and the square root of 2, which become running examples in the series. Finally, we revisit an important case of the Euclidean algorithm relating to certain paths in the tree.

Listing the Rationals using Continued Fractions Part 3

In this video, we extend the Calkin-Wilf tree as fully as possible, and we study the properties of this new tree. For the third time, we improve our understanding of the golden ratio and the square root of 2  with a more sensible treatment of periodic paths. These paths have shocking consequences in the extended tree; we discover ordinary continued fractions for complex numbers, including the imaginary constant i. We also find a simple explanation for a mysterious result: the continued fractions of irrational square root numbers have coefficients which form a palindrome. The video ends by asking if we can classify the numbers which have periodic continued fractions.