Thermalization and prethermalization in the soft-wall AdS/QCD model

Pseudo-Goldstone modes appear in many physical systems and display robust universal features. First, their mass m obeys the so-called Gell-Mann-Oakes-Renner (GMOR) relation f2m2 = $$ H\overline{\sigma} $$ H σ ¯ , with f the Goldstone stiffness, H the explicit breaking scale and $$ \overline{\sigma} $$ σ ¯ the spontaneous condensate. More recently, it has been shown that their damping Ω is constrained to follow the relation Ω = m2Dφ, where Dφ is the Goldstone diffusivity in the purely spontaneous phase. Pions are the most paradigmatic example of pseudo-Goldstone modes and they are related to chiral symmetry breaking in QCD. In this work, we consider a bottom-up soft-wall AdS-QCD model with broken SU(2)L × SU(2)R symmetry and we study the nature of the associated pseudo-Goldstone modes — the pions. In particular, we perform a detailed investigation of their dispersion relation in presence of dissipation, of the role of the explicit breaking induced by the quark masses and of the dynamics near the critical point. Taking advantage of the microscopic information provided by the holographic model, we give quantitative predictions for all the coefficients appearing in the effective description. In particular, we estimate the finite temperature behavior of the kinetic parameter $$ \mathfrak{r} $$ r 2 defined as the ratio between the Goldstone diffusivity Dφ and the pion attenuation constant DA. Interestingly, we observe important deviations from the value $$ \mathfrak{r} $$ r 2 = 3/4 computed in chiral perturbation theory in the limit of zero temperature.

Section: Jhep12(2022)113supporting

confidence: 84%

“…Finally, it would be fruitful to extend our analysis to the time dependent dynamics and analyze the thermalization properties of this system near the critical point as done in the chiral limit in [91].…”

Section: Jhep12(2022)113mentioning

confidence: 99%

Pion dynamics in a soft-wall AdS-QCD model

Cao

Baggioli

Liu

et al. 2022

“…( 6.3). We find numerically that: and also with the holographic results for superfluids in [75] and the analysis of [84] (see also [100,101]).…”

Section: The "Higgs" Mode and Its Masssupporting

confidence: 73%

“…• Quenches in our holographic superconductor model could be useful tools to explore the collective dynamics beyond linear approximation. In particular, one might think of extending the analysis of [100,101] to this case and use GL theory to interpret the numerical results. Nonlinear response is expected to be an excellent probe for the dynamics of the Higgs mode which is usually undetectable in the linear response regime [115].…”

Section: Discussionmentioning

confidence: 99%

“…order parameter to the conserved charge density [93]. For superfluids, this procedure will automatically end up in the so-called model F in the Hoenberg-Halperin classification [99] (see also [87] for a holographic derivation of this dynamics in the holographic superfluid model, [100,101] for a study of the nonlinear dynamics and [102] for an analysis of the universality class of holographic superconductors). It would be interesting to extend the model F in order to account for a dynamical gauge field and the coupling between the different modes.…”

Section: Jhep03(2023)206mentioning

confidence: 99%

See 1 more Smart Citation

Collective dynamics and the Anderson-Higgs mechanism in a bona fide holographic superconductor

Jeong

Baggioli

Kim

et al. 2023

The holographic superconductor is one of the most popular models in the context of applied holography. Despite what its name suggests, it does not describe a superconductor. On the contrary, the low temperature phase of its dual field theory is a superfluid with a spontaneously broken U(1) global symmetry. As already observed in the previous literature, a bona fide holographic superconductor can be constructed using mixed boundary conditions for the bulk gauge field. By exploiting this prescription, we study the near-equilibrium collective dynamics in the Higgs phase and reveal the characteristic features of the Anderson-Higgs mechanism. We show that second sound disappears from the spectrum and the gauge field acquires a finite energy gap of the order of the plasma frequency. We observe an overdamped to underdamped crossover for the Higgs mode which acquires a finite energy gap below ≈ Tc/2, with Tc the superconducting critical temperature. Interestingly, the energy gap of the Higgs mode at low temperature is significantly smaller than 2∆, with ∆ the superconducting energy gap. Finally, we interpret our results using Ginzburg-Landau theory and we confirm the validity of previously derived perturbative analytic expressions.

Dynamical stability from quasi normal modes in 2nd, 1st and 0th order holographic superfluid phase transitions

Zhao

Zhang

Nie

2023

We study a simple extension of the original Hartnoll, Herzog and Horowitz (HHH) holographic superfluid model with two nonlinear scalar self-interaction terms λ|ψ|4 and τ|ψ|6 in the probe limit. Depending on the value of λ and τ, this setup allows us to realize a large spectrum of holographic phase transitions which are 2nd, 1st and 0th order as well as the “cave of wind” phase transition. We speculate the landscape pictures and explore the near equilibrium dynamics of the lowest quasinormal modes (QNMs) across the whole phase diagram at both zero and finite wave-vector. We find that the zero wave-vector results of QNMs correctly present the stability of the system under homogeneous perturbations and perfectly agree with the landscape analysis of homogeneous configurations in canonical ensemble. The zero wave-vector results also show that a 0th order phase transition cannot occur since it always corresponds to a global instability of the whole system. The finite wave-vector results show that under inhomogeneous perturbations, the unstable region is larger than that under only homogeneous perturbations, and the new boundary of instability match with the turning point of condensate curve in grand canonical ensemble, indicating a new explanation from the subsystem point of view. The additional unstable section also perfectly match the section with negative value of charge susceptibility.