Email: callem “at” sas “dot” upenn “dot” edu

Office: 4C1

Pronouns: she/her/hers


I am a second year graduate student and NSF graduate fellow at the University of Pennsylvania, advised by Mona Merling. I’m generally interested in algebraic topology and homotopy theory, and I also have an interest in mathematical visualization and communication. I believe that math can be accessible and enjoyable for everyone.


  • My name is pronounced “mack-SEEN eh-LEH-na CAH-shay.” I grew up in San Diego, CA, and I attended the Waldorf School of San Diego. My high school education inspired me to do a lot of art, music, and performance. (You can check out some of my art and stuff here.)
  • I got a B.A. in math in 2020 from Reed College in Portland, OR. I started out as a Philosophy major, but switched to Math at the end of my second year. I worked closely with Kyle Ormsby and Angélica Osorno, and they both got me into algebraic topology. I also worked with Paul Hovda in the Philosophy department, thinking about stuff like mathematical structuralism. I was featured on What is a Reedie? where I talk a bit about myself, my undergraduate thesis, and my Reed College experience. Read my full responses here.
  • My REU experience with Corey Dunn convinced me to go to math graduate school. I started my Ph.D. at the University of Pennsylvania in the Fall of 2020.


I run a math blog with Thomas Brazelton, Julian Gould, and Andres Mejia. I also have a running list of fun activities related to topology and geometry.

This year, I’m co-organizing the Pizza Seminar with Krishan Canzius, as well as the GeMs in Math group with Ellen Urheim and Marielle Ong.

I’ve adopted a polyhedron, called the Xinegon, which you can see here. The Xinegon has 631 siblings, with f-vector (9, 17, 10). I like that she has some triangular faces, some quadrilateral faces, and some pentagonal faces.

Upcoming Travel and Conferences

Past Travel and Conferences

  • October 2021: Math PATCH Seminar; Bryn Mawr College, PA.
  • July 2021: PCMI’s “Illustrating Mathematics” Graduate Summer School; online.
  • Summer 2021: Algebraic Topology Bridge Summer Workshop; online.
  • April 2021: Underrepresented Students in Algebra and Topology Research Symposium (USTARS); online.
  • April 2021: Graduate Student Topology and Geometry Conference (GSTGC); online.
  • November 2020: Binghamton University Graduate Conference in Algebra and Topology (BUGCAT); online.
  • September 2020: Cascade Topology seminar; online.
  • Summer 2020: Algebraic Topology Bridge Summer Workshop; online.
  • Summer 2020: Graduates Reminisce Online on Topology seminar (GROOT); online.
  • January 2020: Nebraska Conference for Undergraduate Women in Mathematics (NCUWM); University of Nebraska-Lincoln, NE.
  • May 2019: Women and Mathematics (WAM); Institute for Advanced Study, NJ.
  • Summer 2019: Collaborative Mathematics Research Group (CMRG); Reed College,  OR.
  • January 2019: Joint Mathematics Meetings (JMM); Baltimore, MD.
  • November 2018: Undergraduate Mathematics Symposium (UMS); University of Illinois at Chicago, IL.
  • November 2018: Northwest Undergraduate Mathematics Symposium (NUMS); Willamette University, OR.
  • Summer 2018: NSF REU program; California State University, San Bernardino, CA.