Petri Laarne, PhD

• Postdoctoral researcher in mathematics at University of Helsinki.
• Occasional software developer.
• Yleistajuista matikkaa suomeksi: Nollakohta.fi.
• Mastodon: @[email protected].

Contact

You can email me at [email protected]. For best results I recommend English or Finnish, but you may also try French, German, or Swedish.

Note: I am on full-time parental leave until September 2026. I am happy to discuss by email, but may not be able to commit to time-consuming activities before October.

Research

I am interested in stochastic analysis: partial differential equations with a dash of randomness. Generally speaking, I like when stuff has a random component in it. Keywords:

• Stochastic PDE
• Nonlinear wave equations
• Metastable dynamics
• Stochastic quantization

As part of my civilian service, I worked as research assistant at the Institute for Atmospheric and Earth System Research at University of Helsinki. My research was on statistical methods to explore many-variable data sets.

Other past activities:

• Secretary of the Finnish Mathematical Society (2023–2025).
• Co-organizer of the Path Integrals and Friends conference (2024).

Publications

• Publications on ORCiD: 0000-0002-9044-8583.
• Preprints on arXiv.
• Published papers also archived on University of Helsinki research portal.

PhD thesis On stochastic quantization and metastable dynamics (2026).

Articles as of 2 May 2026:

• Barashkov and Laarne: Transition state theory for the hyperbolic φ⁴ model (2026, Electronic Journal of Probability).
• Laarne: Metastable transition times of the 1D dynamical sine-Gordon model (arXiv preprint).
• Barashkov and Laarne: Invariance of φ⁴ measure under nonlinear wave and Schrödinger equations on the plane (arXiv preprint).

Atmospheric data analysis papers from my civilian service:

• Laarne, Amnell, Zaidan, Mikkonen, Nieminen: Exploring Non-Linear Dependencies in Atmospheric Data with Mutual Information (2022, Atmosphere)
• Laarne, Zaidan, Nieminen: ennemi: Non-linear correlation detection with mutual information (2021, SoftwareX)

Software

• ennemi: a Python package to explore non-linear correlations across variables. Developed as part of my work at INAR, now cited by some 30 papers across many research fields.

Teaching

As responsible teacher at University of Helsinki:

• Advanced LaTeX, a PhD-level course in mathematical typesetting, May 2025.
  • Lecture notes: A second course in LaTeX (GitHub)
  • Course page
• Advanced LaTeX, May 2024.
  • Course page

As teaching assistant at University of Helsinki:

• Functional analysis II (Autumn 2025), weekly guidance sessions.
• Todennäköisyyslaskenta II (Autumn 2023), development of STACK exercises.
• Todennäköisyyslaskenta II (Autumn 2022), weekly guidance sessions.
• Lukiomatematiikan kertaus (2021), development of self-study STACK exercises.
• Todennäköisyyslaskenta II (Autumn 2019), weekly exercise sessions.