# Regensburg 2019 – wissenschaftliches Programm

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# DY: Fachverband Dynamik und Statistische Physik

## DY 51: Poster: Stat. Phys., Comp. Meth

### DY 51.1: Poster

### Donnerstag, 4. April 2019, 15:00–18:00, Poster B2

**Random Field Ising Model with spatially disorder strength gradient** — •Christoph Polle and Alexander K. Hartmann — Institut für Physik, University of Oldenburg, Germany

We study numerically [1] a three-dimensional Random Field Ising Model (RFIM) in which a spatially disorder strength gradient *h*(*x*) is introduced. The gradient was chosen so that *h*(*x*) is equal to the critical value *h*_{c} = 2.28 [2] at the half of the lattice in x-direction. The actual magnetic field acting on a spin *i* is defined as *h*_{i} = *h*(*x*)**n*_{i}, where *n*_{i} is a (0,1) quenched Gaussian number.

To investigate the system efficiently the RFIM was transformed to a network, then the maximum flow problem was solved to determine the ground state [3]. This is done for different system sizes and realizations. From the ground state the magnetization, a specific-heat like quantity and the susceptibility where calculated as a function of *x*. Also the system was analyzed in the spirit of gradient percolation problems[4].

[1] A.K. Hartmann, Big Practical Guide to Computer Simulations, World Scientific Publishing, Singapore 2015.

[2] A.K. Hartmann and A.P. Young, Physical Rewiew B **64**, 214419 (2001).

[3] J.-C. Picard and H.D. Ratliff, Networks **5**, 357 (1975).

[4] B. Sapoval, M. Rosso, J.-F. Gouyet, Journal de Physique Lettres **46** (4), pp.149-156 (1985).