Analysis of differential and pseudodifferential problems of mixed type

About the Project

Partial differential equations (PDEs) model a wide range of phenomena in physics, biology, and geoscience. Their classification into hyperbolic, parabolic, and elliptic types plays a central role in analysis. Many important problems, however, involve equations of mixed type, where different behaviours coexist; for example in flows transitioning from subsonic to supersonic regimes. Such equations are particularly challenging due to the interaction of opposing analytical properties.

This project studies mixed-type and degenerate equations within two classical frameworks: the kinetic formulation of degenerate parabolic equations and Friedrichs systems. Our aim is to obtain new results on fundamental questions including well-posedness, regularity, and boundary behaviour. By combining tools from microlocal and harmonic analysis with structural insights from these frameworks, we seek a systematic understanding of equations of mixed type.

Postdoctoral opportunities. The project welcomes expressions of interest from potential postdoctoral candidates interested in partial differential equations and related areas. Interested researchers are encouraged to contact the PI using the contact information provided below.
Funded by the Croatian Science Foundation (HRZZ), Grant No. UIP-2025-02-1337.
Project duration: 19/02/2026 – 18/02/2031 Croatian Science Foundation Logo

News

April 2026
Research visit by Darko Mitrović to Zagreb.
March 2026
Research visit by Ivana Vojnović to Zagreb.
February 2026
Project website launched.

Publications

Preprints

  1. M. Erceg, K. H. Karlsen, N. Konatar, D. Mitrović. Existence of strong initial traces for stochastic conservation laws, September 2026, 42 pp.
  2. M. Erceg, K. H. Karlsen, D. Mitrović. Regularity of velocity averages in kinetic equations with heterogeneity, April 2026, 39 pp.
  3. M. Erceg, K. H. Karlsen, D. Mitrović. Velocity averaging under minimal conditions for deterministic and stochastic kinetic equations with irregular drift, April 2026, 41 pp.

Dissemination

Talks at scientific events

  1. M. Grbac, Classical optimal designs for stationary diffusion with multiple phases, ApplMath26, 21–25 September 2026, Dubrovnik, Croatia
  2. T. Perić, Homogenisation of a heterogeneous Boltzmann equation in the Lp setting, GF2026, 23–27 August 2026, Ohrid, North Macedonia
  3. M. Erceg, Regularity of velocity averages in kinetic equations with heterogeneity, ICM, 23–30 July 2026, Philadelphia, USA
  4. M. Erceg, On homogenisation of linear nonlocal problems in fractional divergence form, GAMM Annual Meeting 2026, 16–20 March 2026, Stuttgart, Germany

Poster presentations at scientific events

  1. T. Perić, Regularity results for equations of ultra-parabolic type by velocity averaging, ApplMath26, 21–25 September 2026, Dubrovnik, Croatia
  2. I. Vojnović, Microlocal defect measures and wave-front sets, 4th Korean Croatian Summer Probability Camp, 29 June – 1 July 2026, Dubrovnik, Croatia

Team

Project Team Photo
Marko Erceg, University of Zagreb, Croatia – Principal Investigator
Matko Grbac, University of Zagreb, Croatia – Researcher
Tomislav Perić, University of Zagreb, Croatia – Researcher
Ivana Vojnović, University of Novi Sad, Serbia – Researcher

Contact

Email: marko.erceg (at) math.hr

Department of Mathematics, Faculty of Science, University of Zagreb, Croatia