Stefan Junk


I'm a postdoc in Probability Theory at Tsukuba University, where I am supported by JSPS as an International Research Fellow. I am hosted by David Croydon (Kyoto University) and Ryoki Fukushima (Tsukuba University).


I have written my PhD thesis about "random polymers in disastrous environments" with Nina Gantert at TU Munich. Between November 2019 and October 2020 I was a postdoc at RIMS, Kyoto University.

See here for a short CV.

Research interests

I mainly work on the following topics:
  • The directed polymer model, and first/last passage percolation.
  • (Branching) random walks in random environment.
  • Stochastic orders, in particular for the above processes.
  • Oriented percolation.
  • The random conductance model, and the Mott random walk in particular.
More broadly, I'm interested in the following areas:
  • Statistical mechanics.
  • Random matrices and integrable probability.
  • Large deviation theory.
  • Random walks on graphs and their resistane forms.

Paper and preprints

  • Directed polymers in the weak disorder phase – Hypercontractivity and new moment bounds. (Download).
  • Number of paths in oriented percolation as zero temperature limit of directed polymer, with Ryoki Fukushima. (arXiv).
  • Anomalous scaling regime for one-dimensional Mott variable-range hopping, with David Croydon and Ryoki Fukushima. (arXiv, short video summary).
  • On large deviation rate functions for a continuous-time directed polymer in weak disorder, with Ryoki Fukushima. Electronic Communications of Probability, 2021(Journal, arXiv).
  • Comparison of partition functions in a space-time random environment. Journal of Statistical Physics, 2020. (Journal, arXiv).
  • Zero temperature limit for the Brownian directed polymer among Poissonian disasters, with Ryoki Fukushima. Annals of Applied Probability, 2019. (Journal, arXiv)
  • A branching random walk among disasters, with Nina Gantert. Electronic Journal of Probability, 2017. (Journal, arXiv)
  • On the survival probability of a random walk in random environment with killing. ALEA Latin American Journal of Probability and Mathematical Statistics, 2014. (Journal, arXiv)

Teaching Experience

I have been TA for various courses as a PhD student in Munich, see here for a list.


Mail: Institute of Mathematics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571 Japan.