Infinite-Randomness Critical Point in the Two-Dimensional Disordered Contact Process
Department
Physics
Major
Physics
Research Advisor
Vojta, Thomas
Advisor's Department
Physics
Funding Source
NSF
Abstract
We study the nonequilibrium phase transition in the two-dimensional contact process on a randomly diluted lattice by means of large-scale Monte Carlo simulations for times up to 1010 and system sizes up to 8000×8000 sites. Our data provide strong evidence for the transition being controlled by an exotic infinite-randomness critical point with activated (exponential) dynamical scaling. We calculate the critical exponents of the transition and find them to be universal, i.e., independent of disorder strength. The Griffiths region between the clean and the dirty critical points exhibits power-law dynamical scaling with continuously varying exponents. We discuss the generality of our findings and relate them to a broader theory of rare region effects at phase transitions with quenched disorder. Our results are of importance beyond absorbing state transitions because, according to a strong-disorder renormalization group analysis, our transition belongs to the universality class of the two-dimensional random transverse-field Ising model.
Biography
Jason Mast is a fourth year physics student who is looking for graduate school. He worked for Dr. Vojta in the two-dimensional contract process; he was responsible for designing, implementing, and testing the correlation program. He was on the Missouri S&T Solar Car Team last year, and was responsible for writing software for the motor controller. Currently he works at Cloud and Aerosol Sciences testing and calibrating equipment.
Research Category
Sciences
Presentation Type
Poster Presentation
Document Type
Poster
Award
Sciences poster session, Second place
Location
Upper Atrium/Hallway
Presentation Date
08 Apr 2009, 9:00 am - 11:45 am
Infinite-Randomness Critical Point in the Two-Dimensional Disordered Contact Process
Upper Atrium/Hallway
We study the nonequilibrium phase transition in the two-dimensional contact process on a randomly diluted lattice by means of large-scale Monte Carlo simulations for times up to 1010 and system sizes up to 8000×8000 sites. Our data provide strong evidence for the transition being controlled by an exotic infinite-randomness critical point with activated (exponential) dynamical scaling. We calculate the critical exponents of the transition and find them to be universal, i.e., independent of disorder strength. The Griffiths region between the clean and the dirty critical points exhibits power-law dynamical scaling with continuously varying exponents. We discuss the generality of our findings and relate them to a broader theory of rare region effects at phase transitions with quenched disorder. Our results are of importance beyond absorbing state transitions because, according to a strong-disorder renormalization group analysis, our transition belongs to the universality class of the two-dimensional random transverse-field Ising model.
Comments
Joint project with Adam Farquhar