Upper bound of the charge diffusion constant in holography

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Hauptverfasser: Huh, Kyoung-Bum, Jeong, Hyun-Sik, Kim, Keun-Young, Sun, Ya-Wen
Format: Preprint
Veröffentlicht: 2021
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author Huh, Kyoung-Bum
Jeong, Hyun-Sik
Kim, Keun-Young
Sun, Ya-Wen
author_facet Huh, Kyoung-Bum
Jeong, Hyun-Sik
Kim, Keun-Young
Sun, Ya-Wen
contents We investigate the upper bound of charge diffusion constant in holography. For this purpose, we apply the conjectured upper bound proposal related to the equilibration scales ($ω_{\text{eq}}, k_{\text{eq}}$) to the Einstein-Maxwell-Axion model. ($ω_{\text{eq}}, k_{\text{eq}}$) is defined as the collision point between the diffusive hydrodynamic mode and the first non-hydrodynamic mode, giving rise to the upper bound of the diffusion constant $D$ at low temperature $T$ as $D = ω_{\text{eq}}/k_{\text{eq}}^2$. We show that the upper bound proposal also works for the charge diffusion and ($ω_{\text{eq}}, k_{\text{eq}}$), at low $T$, is determined by $D$ and the scaling dimension $Δ(0)$ of an infra-red operator as $(ω_{\text{eq}}, \, k_{\text{eq}}^2) \,=\, (2 πT Δ(0) \,, ω_{\text{eq}}/D)$, as for other diffusion constants. However, for the charge diffusion, we find that the collision occurs at real $k_{\text{eq}}$, while it is complex for other diffusions. In order to examine the universality of the conjectured upper bound, we also introduce a higher derivative coupling to the Einstein-Maxwell-Axion model. This coupling is particularly interesting since it leads to the violation of the \textit{lower} bound of the charge diffusion constant so the correction may also have effects on the \textit{upper} bound of the charge diffusion. We find that the higher derivative coupling does not affect the upper bound so that the conjectured upper bound would not be easily violated.
format Preprint
id arxiv_https___arxiv_org_abs_2111_07515
institution arXiv
publishDate 2021
record_format arxiv
spellingShingle Upper bound of the charge diffusion constant in holography
Huh, Kyoung-Bum
Jeong, Hyun-Sik
Kim, Keun-Young
Sun, Ya-Wen
High Energy Physics - Theory
We investigate the upper bound of charge diffusion constant in holography. For this purpose, we apply the conjectured upper bound proposal related to the equilibration scales ($ω_{\text{eq}}, k_{\text{eq}}$) to the Einstein-Maxwell-Axion model. ($ω_{\text{eq}}, k_{\text{eq}}$) is defined as the collision point between the diffusive hydrodynamic mode and the first non-hydrodynamic mode, giving rise to the upper bound of the diffusion constant $D$ at low temperature $T$ as $D = ω_{\text{eq}}/k_{\text{eq}}^2$. We show that the upper bound proposal also works for the charge diffusion and ($ω_{\text{eq}}, k_{\text{eq}}$), at low $T$, is determined by $D$ and the scaling dimension $Δ(0)$ of an infra-red operator as $(ω_{\text{eq}}, \, k_{\text{eq}}^2) \,=\, (2 πT Δ(0) \,, ω_{\text{eq}}/D)$, as for other diffusion constants. However, for the charge diffusion, we find that the collision occurs at real $k_{\text{eq}}$, while it is complex for other diffusions. In order to examine the universality of the conjectured upper bound, we also introduce a higher derivative coupling to the Einstein-Maxwell-Axion model. This coupling is particularly interesting since it leads to the violation of the \textit{lower} bound of the charge diffusion constant so the correction may also have effects on the \textit{upper} bound of the charge diffusion. We find that the higher derivative coupling does not affect the upper bound so that the conjectured upper bound would not be easily violated.
title Upper bound of the charge diffusion constant in holography
topic High Energy Physics - Theory
url https://arxiv.org/abs/2111.07515