University of Minnesota
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Alex Kamenev

“Classification of phase transitions in reaction-diffusion models”
Vlad Elgart and Alex Kamenev , Phys. Rev. E 74, 041101 (2006)

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Equilibrium phase transitions are associated with rearrangements of minima of a (Lagrangian) potential. Treatment of nonequilibrium systems requires doubling of degrees of freedom, which may be often interpreted as a transition from the ?coordinate?- to the ?phase?-space representation. As a result, one has to deal with the Hamiltonian formulation of the field theory instead of the Lagrangian one. We suggest a classification scheme of phase transitions in reaction-diffusion models based on the topology of the phase portraits of corresponding Hamiltonians. In models with an absorbing state such a topology is fully determined by intersecting curves of zero ?energy.? We identify four families of topologically distinct classes of phase portraits stable upon renormalization group transformations.