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Out-of-equilibrium scaling of the energy density along the critical relaxational flow after a quench of the temperature
Haralambos Panagopoulos and Ettore Vicari
Phys. Rev. E 109, 064107 – Published 3 June 2024
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Abstract
We study the out-of-equilibrium behavior of statistical systems along critical relaxational flows arising from instantaneous quenches of the temperature to the critical point , starting from equilibrium conditions at time . In the case of soft quenches, i.e., when the initial temperature is assumed sufficiently close to (to keep the system within the critical regime), the critical modes develop an out-of-equilibrium finite-size-scaling (FSS) behavior in terms of the rescaled time variable , where is the time interval after quenching, is the size of the system, and is the dynamic exponent associated with the dynamics. However, the realization of this picture is less clear when considering the energy density, whose equilibrium scaling behavior (corresponding to the starting point of the relaxational flow) is generally dominated by a temperature-dependent regular background term or mixing with the identity operator. These issues are investigated by numerical analyses within the three-dimensional lattice -vector models, for and 4, which provide examples of critical behaviors with negative values of the specific-heat critical exponent , implying that also the critical behavior of the specific heat gets hidden by the background term. The results show that, after subtraction of its asymptotic critical value at , the energy density develops an asymptotic out-of-equilibrium FSS in terms of as well, whose scaling function appears singular in the small- limit.
- Received 20 March 2024
- Accepted 9 May 2024
DOI:https://doi.org/10.1103/PhysRevE.109.064107
©2024 American Physical Society
Physics Subject Headings (PhySH)
- Research Areas
Critical phenomenaNonequilibrium statistical mechanicsRenormalization groupStatistical field theory
- Physical Systems
Lattice models in statistical physics
- Techniques
Finite-size scalingScaling methods
Statistical Physics & ThermodynamicsParticles & FieldsCondensed Matter, Materials & Applied Physics
Authors & Affiliations
Haralambos Panagopoulos1 and Ettore Vicari2
- 1Department of Physics, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
- 2Dipartimento di Fisica dell' Università di Pisa, Largo Pontecorvo 3, I-56127 Pisa, Italy
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Vol. 109, Iss. 6 — June 2024
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Figure 1
The ratio along the critical relaxational flow vs for , at fixed (bottom) and (top). The statistical errors are very small, and practically invisible in the plots. The insets show the large- convergence for some fixed values of , plotting the corresponding data vs , which is the expected behavior of the scaling corrections.
Figure 2
The ratio along the critical relaxational flow vs for , at fixed (bottom) and (top). The inset of the bottom figureshows the large- convergence for some fixed values of vs their expected leading suppression. The inset of the top figureshows the data up to a relatively large value , for lattice sizes up to , demonstrating the large-time convergence to the corresponding equilibrium value at the critical point, which, in turn, converges to the critical value [55] in the large- limit (indicated by the dashed line).
Figure 3
Out-of-equilibrium FSS of the subtracted energy density along the critical relaxational flow for , at fixed (bottom) and (top). The insets show the large- convergence for some fixed values of , indicating that the scaling corrections are small, and consistent with . The statistical errors are very small, and practically invisible in the plots. Note that the data at do not scale; see Fig.5.
Figure 4
Out-of-equilibrium FSS of the subtracted energy density along the critical relaxational flow, at fixed (bottom) and (top). The inset of the bottom figureshows the large- convergence for some fixed values of . The inset of the top figureshows the data up to a relatively large value of , i.e., , at fixed and for lattice sizes up to , demonstrating the large time convergence to the corresponding equilibrium value at the critical point. Note that the data at do not scale, like the cases.
Figure 5
The subtracted energy at for and some values of (the errors of the data are practically invisible in the plot). To make evident the expected equilibrium behavior reported in Eqs.(16) and (17), we plot vs with , which is the relative power law of the scaling term with respect to the background contribution at equilibrium. The data show the behavior reported in Eq.(29). The lines show linear fits of the data for the larger lattices, which have acceptable . We stress that this scaling behavior does not match that observed at fixed . Analogous power-law behaviors are observed for .
Figure 6
Log-log plot of data of the subtracted energy density, highlighting the behavior at small , for (top) and (bottom), at . The dashed lines show linear fits of the data of at small , i.e., , to the asymptotic behavior with . Analogous results are obtained for other values of , such as for and for .