Abstract We employ the perturbative fieldtheoretic renormalization group method to investigate the universal critical behavior near the continuous non-equilibrium phase transition in the complex Ginzburg–Landau equation with additive white noise. This stochastic partial differential describes a remarkably wide range of physical systems: coupled nonlinear oscillators subject to external noise near a Hopf bifurcation instability; spontaneous structure formation in non-equilibrium systems, e.g., in cyclically competing populations; and driven-dissipative Bose–Einstein condensation, realized in open systems on the interface of quantum optics and many-body physics, such as cold atomic gases and exciton-polaritons in pumped semiconductor quantum wells in optical cavities. Our starting point is a noisy, dissipative Gross–Pitaevski or nonlinear Schrödinger equation, or equivalently purely relaxational kinetics originating from a complex-valued Landau–Ginzburg functional, which generalizes the standard equilibrium model A critical dynamics of a non-conserved complex order parameter field. We study the universal critical behavior of this system in the early stages of its relaxation from a Gaussian-weighted fully randomized initial state. In this critical aging regime, time translation invariance is broken, and the dynamics is characterized by the stationary static and dynamic critical exponents, as well as an independent ‘initial-slip’ exponent. We show that to first order in the dimensional expansion about the upper critical dimension, this initial-slip exponent in the complex Ginzburg–Landau equation is identical to its equilibrium model A counterpart. We furthermore employ the renormalization group flow equations as well as construct a suitable complex spherical model extension to argue that this conclusion likely remains true to all orders in the perturbation expansion.Abstract We employ the perturbative fieldtheoretic renormalization group method to investigate the universal critical behavior near the continuous non-equilibrium phase transition in the complex Ginzburg–Landau equation with additive white noise. This stochastic partial differential describes a remarkably wide range of physical systems: coupled nonlinear oscillators subject to external noise near a Hopf bifurcation instability; spontaneous structure formation in non-equilibrium systems, e.g., in cyclically competing populations; and driven-dissipative Bose–Einstein condensation, realized in open systems on the interface of quantum optics and many-body physics, such as cold atomic gases and exciton-polaritons in pumped semiconductor quantum wells in optical cavities. Our starting point is a noisy, dissipative Gross–Pitaevski or nonlinear Schrödinger equation, or equivalently purely relaxational kinetics originating from a complex-valued Landau–Ginzburg functional, which generalizes the standard equilibrium model A critical dynamics of a non-conserved complex order parameter field. We study the universal critical behavior of this system in the early stages of its relaxation from a Gaussian-weighted fully randomized initial state. In this critical aging regime, time translation invariance is broken, and the dynamics is characterized by the stationary static and dynamic critical exponents, as well as an independent ‘initial-slip’ exponent. We show that to first order in the dimensional expansion about the upper critical dimension, this initial-slip exponent in the complex Ginzburg–Landau equation is identical to its equilibrium model A counterpart. We furthermore employ the renormalization group flow equations as well as construct a suitable complex spherical model extension to argue that this conclusion likely remains true to all orders in the perturbation expansion.

arXiv:1606.08263Journal of Physics A Mathematical and TheoreticalOct 3, 20167 citations

Quantum criticality: beyond the Landau-Ginzburg-Wilson paradigm

Subir Sachdev A

APSMar 1, 20040 citations

Dynamic scaling

Uwe Claus Täuber

In the preceding chapter, we have introduced several levels for the mathematical description of stochastic dynamics. We now use the kinetic Ising models introduced in Section 2.3.3 to formulate the dynamic scaling hypothesis which appropriately generalizes the homogeneity property of the static correlation function in the vicinity of a critical point, as established in Chapter 1. The dynamic critical exponent z is defined to characterize both the critical dispersion and the basic phenomenon of critical slowing-down. As a next step, and building on the results of Section 2.4, a continuum effective theory for the mesoscopic order parameter density, basically the dynamical analog to the Ginzburg–Landau approach, is constructed in terms of a non-linear Langevin equation. The distinction between dissipative and diffusive dynamics for the purely relaxational kinetics of either a non-conserved or conserved order parameter field, respectively, defines the universality classes A and B. Following the analysis of these models in the Gaussian approximation, they also serve to outline the construction of a dynamical perturbation theory for non-linear stochastic differential equations through direct iteration. In general, however, the order parameter alone does not suffice to fully capture the critical dynamics near a second-order phase transition. Additional hydrodynamic modes originating from conservation laws need to be accounted for as well. The simplest such situation is entailed in the relaxational models C and D, which encompass the static coupling of the order parameter to the energy density. Further scenarios emerge through reversible non-linear mode couplings in the Langevin equations of motion.In the preceding chapter, we have introduced several levels for the mathematical description of stochastic dynamics. We now use the kinetic Ising models introduced in Section 2.3.3 to formulate the dynamic scaling hypothesis which appropriately generalizes the homogeneity property of the static correlation function in the vicinity of a critical point, as established in Chapter 1. The dynamic critical exponent z is defined to characterize both the critical dispersion and the basic phenomenon of critical slowing-down. As a next step, and building on the results of Section 2.4, a continuum effective theory for the mesoscopic order parameter density, basically the dynamical analog to the Ginzburg–Landau approach, is constructed in terms of a non-linear Langevin equation. The distinction between dissipative and diffusive dynamics for the purely relaxational kinetics of either a non-conserved or conserved order parameter field, respectively, defines the universality classes A and B. Following the analysis of these models in the Gaussian approximation, they also serve to outline the construction of a dynamical perturbation theory for non-linear stochastic differential equations through direct iteration. In general, however, the order parameter alone does not suffice to fully capture the critical dynamics near a second-order phase transition. Additional hydrodynamic modes originating from conservation laws need to be accounted for as well. The simplest such situation is entailed in the relaxational models C and D, which encompass the static coupling of the order parameter to the energy density. Further scenarios emerge through reversible non-linear mode couplings in the Langevin equations of motion.

Cambridge University Press eBooksMar 6, 20140 citations

Quantum critical dynamics of the boson system in the Ginzburg–Landau model

Mikhail Gennag'evich Vasin

Physica A Statistical Mechanics and its ApplicationsAug 19, 20144 citations

Nonlinear relaxation near the critical point: Molecular-field and scaling theory

Zoltàn Ràcz

We examine the critical-point singularity of the nonlinear relaxation of purely dissipative systems. Applying the molecular-field approximation to the time-dependent Ginzburg-Landau model, it is shown that the critical exponent of the nonlinear relaxation time (${\ensuremath{\Delta}}^{(\mathrm{nl})}$) can be different from that of the linear one (${\ensuremath{\Delta}}^{(l)}$) even in ergodic systems. From the assumptions that scaling applies and that only the near-equilibrium fluctuations significantly affect the relaxation time, a scaling law ${\ensuremath{\Delta}}^{(\mathrm{nl})}={\ensuremath{\Delta}}^{(l)}\ensuremath{-}\ensuremath{\beta}$ is derived ($\ensuremath{\beta}$ is the critical exponent of the order). On the base of this scaling law we reanalyze the available Monte Carlo calculations, high-temperature series, and the critical-slowing-down experiment on ${\mathrm{Ni}}_{3}$ Mn.We examine the critical-point singularity of the nonlinear relaxation of purely dissipative systems. Applying the molecular-field approximation to the time-dependent Ginzburg-Landau model, it is shown that the critical exponent of the nonlinear relaxation time (${\ensuremath{\Delta}}^{(\mathrm{nl})}$) can be different from that of the linear one (${\ensuremath{\Delta}}^{(l)}$) even in ergodic systems. From the assumptions that scaling applies and that only the near-equilibrium fluctuations significantly affect the relaxation time, a scaling law ${\ensuremath{\Delta}}^{(\mathrm{nl})}={\ensuremath{\Delta}}^{(l)}\ensuremath{-}\ensuremath{\beta}$ is derived ($\ensuremath{\beta}$ is the critical exponent of the order). On the base of this scaling law we reanalyze the available Monte Carlo calculations, high-temperature series, and the critical-slowing-down experiment on ${\mathrm{Ni}}_{3}$Mn.

Physical review. B, Solid stateJan 1, 197656 citations

{\mathrm{Ni}}_{3}

Mn.