Kevin Zhou

Biography

I’m a postdoctoral researcher at UC Berkeley and LBNL, working at the Berkeley Center for Theoretical Physics. I am primarily interested in accelerating the discovery of physics beyond the Standard Model through new kinds of precision experiments. Many of these ideas focus on detecting ultralight dark matter, though I’ve also thought about more radical possibilities, such as modifications of long-range forces due to continuous spin. A complete CV is available here.

Previously, I earned my PhD degree at Stanford in 2024, and Master’s degrees at Cambridge and Oxford. During that period I spent a lot of energy on physics education and outreach, and I’m still always interested in hearing a good physics puzzle. For research-related inquiries, you can reach me at kzhou7@berkeley.edu, and for everything else, try kzhou7@gmail.com.

Recent Papers

A. Berlin, A. Millar, T. Trickle, K. Zhou

December 2023 JHEP

Physical Signatures of Fermion-Coupled Axion Dark Matter

The axion-fermion coupling induces spin-dependent forces and torques, which can lead to macroscopic currents. “Magnetized multilayer” setups can use these currents to probe orders of magnitude beyond existing bounds.

arXiv JHEP Talk slides

P. Schuster, N. Toro, K. Zhou

March 2023 JHEP

Interactions of Particles with "Continuous Spin" Fields

Observed long-range forces are traditionally assumed to be mediated by fields with exactly zero spin scale. We present the first theory of matter particles interacting with “continuous spin” fields with arbitrary $\rho$, and show that there are calculable, universal, observable $\rho$-dependent modifications from familiar gauge theories.

arXiv JHEP Talk slides

A. Berlin, K. Zhou

September 2022 Phys. Rev. D

Discovering QCD-Coupled Axion Dark Matter with Polarization Haloscopes

QCD axion dark matter induces oscillating EDMs, yielding physical currents that can be amplified in a microwave cavity. This setup has the unique ability to test whether a cavity haloscope signal arises from the QCD axion.

arXiv Phys. Rev. D Talk slides

P. Schuster, N. Toro, K. Zhou

December 2021 Phys. Rev. D

Probing Invisible Vector Meson Decays with NA64 and LDMX

Electron beam fixed target experiments such as NA64 and LDMX can improve constraints on invisible light vector meson decays by $5$ orders of magnitude, enhancing their sensitivity to dark matter of mass $m_\chi \gtrsim 0.1 \ \mathrm{GeV}$.

arXiv Phys. Rev. D Talk slides

See all publications

Teaching

Quantum Field Theory I (Physics 330)

In Autumn 2022, I was the TA for Stanford’s introductory quantum field theory class, taught by Prof. Bernhard Mistlberger. We overhauled the course and produced new problem sets, which we believe strike a good balance between traditional particle physics applications, and connections to other fields. I also taught weekly sections which laid out the big picture and showed tricks for doing the problems efficiently.

Problem sets: 1, 2, 3, 4, 5, 6, 7, 8, 9 | Solutions: 1, 2, 3, 4, 5, 6, 7, 8, 9
Very rough section notes: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
Final exam | Solutions

Physics Olympiad Handouts

From 2021 to 2024, I coached the US Physics Team and wrote a good chunk of its exam questions, while developing a comprehensive set of training material. These handouts are the result. They contain full explanations of all the problem solving techniques used in the USAPhO and IPhO, hundreds of illustrative examples, and about 1,000 tough questions, with solutions. For more details, see the syllabus and FAQ. Usually, students take a year to work through the handouts; to see if you’re ready, try the preliminary problems (answers here).

Core Curriculum

Problem Solving I (Sol), Problem Solving II (Sol)
Mech I (Sol), Mech II (Sol), Mech III (Sol), Mech IV (Sol)
Elec I (Sol), Elec II (Sol), Elec III (Sol), Elec IV (Sol)
Mech V (Sol), Mech VI (Sol), Mech VII (Sol)
Thermo I (Sol), Thermo II (Sol), Thermo III (Sol)
Elec V (Sol), Elec VI (Sol), Elec VII (Sol)
Relativity I (Sol), Relativity II (Sol)
Waves I (Sol), Waves II (Sol), Modern I (Sol)

Supplemental Topics, Review, and Practice Olympiads

Mech VIII (Sol), Elec VIII (Sol), Relativity III (Sol)
Waves III (Sol), Modern II (Sol), Modern III (Sol)
Mech Review (Sol), Elec Review (Sol), Other Review (Sol)
USAPhO-M (Sol), USAPhO-E (Sol), USAPhO-X (Sol)
USAPhO-A (Sol), USAPhO-B (Sol), USAPhO-C (Sol), USAPhO-D (Sol)
Expt (Sol), Final (Sol)

Personal Notes

These are the notes I’ve taken while learning physics. I use them for reference, but they’re quite terse, and not a good resource to learn from. They weigh in at 1,900 pages and 750,000 words.

Undergraduate

These notes cover what I learned at MIT, through courses, lecture notes, and books.

Graduate

These notes follow courses taught at Cambridge’s Part III and Oxford’s MMathPhys.

If you like the style, you can download a TeX template here.

Writing

Advice

Learning Introductory Physics. A FAQ for high school students who want to start learning physics or taking part in physics competitions, such as the USAPhO.
After Introductory Physics. Some tips for self-taught students on what to do after mastering the basics, including book recommendations and online resources.
Physics Activities. Some places you can apply your physics knowledge in high school.
The Theoretical Minimum. A short list of canonical books you could self-study, to go from the level of introductory physics to PhD candidacy.
The Stanford Physics Qualifying Exam. A transcript of my PhD qualifying exam, and advice.

Expository

The Surprising Subtlety of Electrostatic Field Lines. A fun puzzle in electrostatics and its resolution with differential geometry; coauthored with Tomas Brauner.
Novel Searches for Physics Beyond the Standard Model. My Stanford PhD dissertation, covering several new types of experimental searches, and their motivation.
Cosmological Relaxation. My Oxford MSc dissertation, reviewing models that “relax” the Higgs boson’s mass, and motivations for model building.
The Meaning of Nothing. The New College Demuth prize essay, on how theoretical stories map onto reality, and why a physicist’s philosophical flexibility is a useful tool. Published in the New College Record with a wonderful illustration by Audrey Effenberger.

Links

Here are some memorable articles about science and everything else.
Here are some fun videos for a rainy day.
My 1,000 answers on Physics StackExchange have 2.5 million views; here’s a sample.