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- Joachim Mathiesen, Mogens H Jensen, Jan Oystein Haavig Bakke
- Physical review. E, Statistical, nonlinear, and…
- 2008

We study the growth of fractal clusters in the dielectric breakdown model (DBM) by means of iterated conformal mappings. In particular we investigate the fractal dimension and the maximal growth site (measured by the Hoelder exponent alpha_{min} ) as a function of the growth exponent eta of the DBM model. We do not find evidence for a phase transition from… (More)

- Joachim Mathiesen, Namiko Mitarai, Kim Sneppen, Ala Trusina
- Physical review letters
- 2011

Ecological systems comprise an astonishing diversity of species that cooperate or compete with each other forming complex mutual dependencies. The minimum requirements to maintain a large species diversity on long time scales are in general unknown. Using lichen communities as an example, we propose a model for the evolution of mutually excluding organisms… (More)

- Namiko Mitarai, Joachim Mathiesen, Kim Sneppen
- Physical review. E, Statistical, nonlinear, and…
- 2012

The biological requirements for an ecosystem to develop and maintain species diversity are in general unknown. Here we consider a model ecosystem of sessile and mutually excluding organisms competing for space [Mathiesen et al. Phys. Rev. Lett. 107, 188101 (2011)]. Competition is controlled by an interaction network with fixed links chosen by a Bernoulli… (More)

- Dirk Helbing, Anders Johansson, Joachim Mathiesen, Mogens H Jensen, Alex Hansen
- Physical review letters
- 2006

We propose a many-particle-inspired theory for granular outflows from a hopper and for the escape dynamics through a bottleneck based on a continuity equation in polar coordinates. If the inflow is below the maximum outflow, we find an asymptotic stationary solution. If the inflow is above this value, we observe queue formation, which can be described by a… (More)

- Maria Thomsen, Anier Hernandez-Garcia, +4 authors Robert Feidenhans'l
- PloS one
- 2014

In this study we estimate the subcutaneous tissue counter pressure during drug infusion from a series of injections of insulin in type 2 diabetic patients using a non-invasive method. We construct a model for the pressure evolution in subcutaneous tissue based on mass continuity and the flow laws of a porous medium. For equivalent injection forces we… (More)

- Jeppe Juul, Kim Sneppen, Joachim Mathiesen
- Physical review. E, Statistical, nonlinear, and…
- 2013

The spatial rock-paper-scissors ecosystem, where three species interact cyclically, is a model example of how spatial structure can maintain biodiversity. We here consider such a system for a broad range of interaction rates. When one species grows very slowly, this species and its prey dominate the system by self-organizing into a labyrinthine… (More)

- Joachim Mathiesen, Luiza Angheluta, Peter T. H. Ahlgren, Mogens H. Jensen
- Proceedings of the National Academy of Sciences…
- 2013

Using empirical data from a social media site (Twitter) and on trading volumes of financial securities, we analyze the correlated human activity in massive social organizations. The activity, typically excited by real-world events and measured by the occurrence rate of international brand names and trading volumes, is characterized by intermittent… (More)

- Jeppe Juul, Kim Sneppen, Joachim Mathiesen
- Physical review. E, Statistical, nonlinear, and…
- 2012

The rock-paper-scissors game is a model example of the ongoing cyclic turnover typical of many ecosystems, ranging from the terrestrial and aquatic to the microbial. Here we explore the evolution of a rock-paper-scissors system where three species compete for space. The species are allowed to mutate and change the speed by which they invade one another. In… (More)

- Eran Bouchbinder, Joachim Mathiesen, Itamar Procaccia
- Physical review. E, Statistical, nonlinear, and…
- 2005

We propose a theoretical model for branching instabilities in 2-dimensional fracture, offering predictions for when crack branching occurs, how multiple cracks develop, and what is the geometry of multiple branches. The model is based on equations of motion for crack tips which depend only on the time dependent stress intensity factors. The latter are… (More)

- Jan O. Haerter, Bjorn Jamtveit, Joachim Mathiesen
- Physical review letters
- 2012

In communication networks, structure and dynamics are tightly coupled. The structure controls the flow of information and is itself shaped by the dynamical process of information exchanged between nodes. In order to reconcile structure and dynamics, a generic model, based on the local interaction between nodes, is considered for the communication in large… (More)