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Nominal thermodynamic temperature in nonequilibrium kinetic Ising models.
Francisco Sastre1, Ivan Dornic, Hugues Chaté
1Instituto de Física de la Universidad de Guanajuato, AP E-143, CP 37150, León, Gto., México.
Physical Review Letters
|February 3, 2004
Summary
A nominal temperature is defined for nonequilibrium kinetic Ising models. At critical points, the fluctuation-dissipation ratio is a universal amplitude ratio, specifically X(infinity) ≈ 0.33(1) for Ising and X(infinity) = 1/2 for voter universality classes.
Area of Science:
- Statistical mechanics
- Condensed matter physics
- Complex systems
Background:
- Nonequilibrium systems lack a universally defined temperature.
- The fluctuation-dissipation theorem relates equilibrium fluctuations to response functions.
- Kinetic Ising spin models are fundamental for studying phase transitions.
Purpose of the Study:
- To define a consistent nominal temperature in nonequilibrium kinetic Ising models.
- To investigate the nature of the fluctuation-dissipation ratio at critical points.
- To determine the universality class of the fluctuation-dissipation ratio.
Main Methods:
- Analysis of large classes of nonequilibrium kinetic Ising spin models.
- Calculation of the large-time fluctuation-dissipation ratio, X(infinity).
- Identification of universal amplitude ratios at critical points.
Main Results:
- A nominal temperature is uniquely defined across the phase diagram.
- The fluctuation-dissipation ratio X(infinity) is confirmed as a universal amplitude ratio.
- Specific values X(infinity) ≈ 0.33(1) and X(infinity) = 1/2 are found for Ising and voter universality classes, respectively.
Conclusions:
- The concept of temperature can be extended to a broad range of nonequilibrium systems.
- The fluctuation-dissipation ratio provides a universal characteristic at critical points.
- This work unifies understanding of critical phenomena in different universality classes.