Publishing type：Research paper (scientific journal)  

DOI： 10.1007/JHEP05(2024)274

arXiv

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Publishing type：Research paper (scientific journal)  

DOI： 10.1007/JHEP11(2023)128

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Publishing type：Research paper (scientific journal)  

DOI： 10.1007/JHEP03(2023)173

arXiv

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

We study critical phenomena at a tricritical point associated with a chiral phase transition which emerges in the D3/D7 model in the presence of a finite baryon number density and an external magnetic field. We numerically determine critical exponents related to the thermodynamic quantities and correlation functions. We find that the values of the critical exponents agree with the mean-field values. The scaling relations between the critical exponents are satisfied, implying that the scaling hypothesis for the free energy and the correlation functions hold. Our results indicate that the critical phenomena at the tricritical point in the D3/D7 model are well described by the conventional Landau theory.

DOI： 10.1007/jhep11(2022)107

arXiv

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Other Link： https://link.springer.com/article/10.1007/JHEP11(2022)107/fulltext.html

Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevD.106.106010

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Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevD.106.026006

arXiv

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media {LLC}  

<jats:title>A<jats:sc>bstract</jats:sc>
</jats:title><jats:p>In this study, we analyze the dynamical stability of the D3-D7 model dual to a holographic conductor with a constant current under an external electric field. We particularly focus on the stability around the parameter region where the multivalued relation between the external electric field and the current is shown due to nonlinear conductivity. The dynamical stability of the states can be analyzed by considering linear perturbations in the background states and computing the quasinormal modes. In the multivalued region, we find that the states in one branch with a low electric current can be dynamically unstable. The turning point in the <jats:italic>J</jats:italic>–<jats:italic>E</jats:italic> characteristic coincides with the stability switching. Further, we also find that the perturbations around the unstable states can become stable with finite wavenumber. In other words, the perturbations in the background states become static at a critical wavenumber, implying the existence of inhomogeneous steady states with current filaments.</jats:p>

DOI： 10.1007/jhep04(2022)173

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Publishing type：Research paper (scientific journal)  

DOI： 10.7566/JPSJ.90.113702

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Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevD.104.066007

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

We investigate dispersion relation of Nambu-Goldstone modes in a dissipative system realized by the AdS/CFT correspondence. We employ the D3/D7 model which represents $$ \mathcal{N} $$ = 4 supersymmetric Yang-Mills theory coupled to $$ \mathcal{N} $$ = 2 flavor fields. If we consider massless quarks in the presence of an external magnetic field, the system exhibits the phase transition associated with the spontaneous symmetry breaking of the chiral symmetry. We find that the Nambu-Goldstone modes show a diffusive behavior in the dispersion relation, which agrees with that found with the effective field theory approach. We also study a non-equilibrium steady state which has a constant current flow in the presence of an external electric field. In a non-equilibrium steady state, we find that the Nambu-Goldstone modes show a linear dispersion in the real part of the frequency in addition to the diffusive behavior. Moreover, we analyze the linear dispersion of the Nambu-Goldstone modes in the hydrodynamic approximation. As a result, we find that the linear dispersion can be written as the analytic functions of quantities in the dual field theory. Our results imply that such a linear dispersion is a characteristic behavior of Nambu-Goldstone modes in a non-equilibrium steady state.

DOI： 10.1007/jhep04(2021)040

arXiv

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Other Link： https://link.springer.com/article/10.1007/JHEP04(2021)040/fulltext.html

Publishing type：Research paper (scientific journal)   Publisher：American Physical Society ({APS})  

DOI： 10.1103/PhysRevLett.124.191603

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

The theory of superconductivity can be divided into two groups depending on whether it has multi-kink solutions. For example, the BCS theory and the Gross-Neveu model have metastable multi-kink solutions whereas the conventional Ginzburg-Landau theory without higher-derivative interactions does not have any multi-kink solutions. In this paper, we systematically examine the solutions of the holographic superconductor model to find out which group the model falls into. We show that the holographic superconductor model has metastable multi-kink solutions. In this sense, we find that the holographic superconductor model falls into the category of the BCS theory and the Gross- Neveu model. We also find that the holographic superconductor model has kink crystalline condensates which are well-fitted by the Jacobi elliptic functions.

DOI： 10.1007/jhep04(2020)022

arXiv

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Other Link： https://link.springer.com/article/10.1007/JHEP04(2020)022/fulltext.html

Publishing type：Research paper (scientific journal)  

We study critical phenomena of nonequilibrium phase transitions by using the AdS/CFT correspondence. Our system consists of charged particles interacting with a heat bath of neutral gauge particles. The system is in current-driven nonequilibrium steady state, and the nonequilibrium phase transition is associated with nonlinear electric conductivity. We define a susceptibility as a response of the system to the current variation. We further define a critical exponent from the power-law divergence of the susceptibility. We find that the critical exponent and the critical amplitude ratio of the susceptibility agree with those of the Landau theory of equilibrium phase transitions, if we identify the current as the external field in the Landau theory.

DOI： 10.1103/physrevd.98.106027

arXiv

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