Petri Laarne

• Doctoral researcher (2022–) in mathematics at University of Helsinki.
• Occasional software developer.
• Yleistajuista matikkaa suomeksi: Nollakohta.fi.

Contact details:

• Languages: suomi, English, français, svenska, Deutsch (in rough order of fluency).
• Office: Exactum B315.
• Email: [email protected].
• Mastodon: @[email protected].

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.

Preprints as of 14 October 2025:

• Laarne: Metastable transition times of the 1D dynamical sine-Gordon model (arXiv).
• Barashkov and Laarne: Eyring–Kramers law for the hyperbolic φ⁴ model (arXiv).
• Barashkov and Laarne: Invariance of φ⁴ measure under nonlinear wave and Schrödinger equations on the plane (arXiv).

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, MDPI)
• Laarne, Zaidan, Nieminen: ennemi: Non-linear correlation detection with mutual information (2021, SoftwareX, Elsevier)

MSc thesis Periodic nonlinear Schrödinger equation (2021).

Software

• ennemi: a Python package to explore non-linear correlations across variables. Developed as part of my work at INAR, now cited by some 20 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.