In this work, we present a gravitational dual to a constriction Josephson junction constructed from the AdS/BCFT correspondence. On the gravity side, we consider a planar AdS-Schwarzschild black hole. Our junction is connected by the boundary Ω with tension Σ on the boundary CFT. This approach lead us to analytical solutions rather than usual numerical methods. Our computations on the gravity side reproduce the standard relation between the current across the junction and the phase difference of the condensate controlled by the tension Σ. We also study the maximum current’s dependence on the junction’s tension and size and reproduce familiar results.

Brazil

Fabiano Santos

Henrique Boschi-Filho

Geometric Josephson junction

In this work we consider anomalous and linear holographic hard wall (HW) models for light unflavored mesons inspired by the AdS/CFT correspondence. The anomalous dimensions depend on the logarithm of the spin <math><mi>S</mi></math> of the meson state and come from a semiclassical analysis of gauge/string duality. The anomalous HW model produces very good masses and good Regge trajectories for mesons compared with PDG data. Inspired by this anomalous HW model we also propose a phenomenological modification of the dimension of the boundary operators such that the model produces asymptotic linear Regge trajectories. Both anomalous HW models considered here present mass percentage deviations of less than 3%, when compared with PDG data.

Rafael A. Costa-Silva

Anomalous and linear holographic hard wall models for light unflavored mesons

In this work we propose improved holographic hard wall (HW) models by the inclusion of anomalous dimensions in the dual operators that describe glueballs inspired by the AdS/CFT correspondence. The anomalous dimensions come from well known semiclassical gauge/string duality analysis showing a dependence with the logarithm of spin <math><mrow><mi>S</mi></mrow></math> of the boundary states. We show that these logarithm anomalous dimensions of the high spin operators combined with the usual HW model allow us to match the pomeron trajectory and give glueball masses that are better than that of the original HW and soft wall models in comparison with lattice data. We also build up other anomalous HW models considering that the logarithm anomalous dimensions can be approximated by a truncated series of odd powers of the difference <math><msqrt><mi>S</mi></msqrt><mo>−</mo><mn>1</mn><mo>/</mo><msqrt><mi>S</mi></msqrt></math>. These models also fit the pomeron trajectory and produce good glueball masses. Then, we consider an anomalous dimension that is proportional to <math><msqrt><mi>S</mi></msqrt></math>, providing reasonable results. Finally, we propose an asymptotic linear anomalous HW model that effective dimensions for high spins operators are of the form <math><mi>Δ</mi><mo>=</mo><mi>a</mi><msqrt><mi>S</mi></msqrt><mo>+</mo><mi>b</mi></math>, where <math><mi>a</mi></math> and <math><mi>b</mi></math> are constants to be fixed by comparison with the soft pomeron trajectory. In this last model, the Regge trajectory is asymptotically linear even for very high spins (<math><mi>J</mi><mo>∼</mo><mn>100</mn></math>) matching the soft pomeron trajectory accurately and generates glueball masses with deviations with respect to the lattice data better than the original HW and soft wall models.

Anomalous and linear holographic hard wall models for glueballs and the pomeron

In this work, we consider Horndeski gravity deformed by a parameter in its kinetic terms embedded in asymptotically Lifshitz spacetimes. We obtain black brane solutions in this geometry and study their thermodynamical properties. We show that the <math><mi>κ</mi></math> deformation on the Horndeski kinetic terms allows for arbitrary values of the critical exponents characteristic of Lifshitz spacetimes. These solutions present local and global thermodynamical stabilities.

Fabiano F. Santos

Black branes in asymptotically Lifshitz spacetimes with arbitrary exponents in <math><mi>κ</mi></math>-Horndeski gravity

In this paper we investigate some general aspects of fluctuation and dissipation in the holographic scenario at zero and finite density. We model this situation with a probe string in a diagonal metric representing a black brane. The string stretches from the black brane to a probe brane, thus simulating a stochastic driven particle. In this scenario, we compute the admittance, the diffusion coefficient, the correlation functions, and the regularized mean square displacement, for bosons and fermions, all from the metric components. We check these calculations with the fluctuation-dissipation theorem. Further, we show that at finite temperature and density, the mean square displacement in the limit of short times reproduces the usual quadratic (ballistic) behavior, for bosons and fermions. For large times, we find ultraslow diffusive processes in various cases, except for bosons at the zero chemical potential. We apply this general analysis in two different models: hyperscaling violation at finite temperature and a charged dilatonic anti–de Sitter black hole, both for bosons and fermions. This is important because we found the fermionic diffusion in systems that allow the appearance of Fermi surfaces and Fermi liquids.

Nathan G. Caldeira

Carlos A. D. Zarro

Bosonic and fermionic holographic fluctuation and dissipation at finite temperature and density

We compare the holographic dressed soft wall and the exponentially deformed AdS models for spin <math><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math> fermions. We present the dressed soft wall model and its analytical solutions for the left and right modes, and the corresponding spectra, also including modifications considering hyperfine spin-spin and meson cloud interactions, as well as anomalous dimensions. Then, we discuss the deformed AdS model for spin <math><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math> fermions and present their effective Schrödinger equations for the left and right modes, for which only numerical solutions are available. Then, we consider a polynomial expansion of the effective potential of the deformed AdS model and show that in the quadratic approximation it leads to exact analytical solutions comparable with the dressed soft wall model and obtain the corresponding spectra for left and right modes. We show a numerical comparison of the mass spectra of spin <math><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math> baryons for the dressed soft wall and the deformed AdS models. We present a detailed relation between the quadratic approximation of the deformed AdS and the dressed soft wall models for their spectra, wave functions, and comments on the deep inelastic scattering on both models. We find that these two models are not equivalent even in the quadratic approximation, but it is possible to relate their left and right modes for particular choices of their parameters.

Ayrton da Cruz Pereira do Nascimento

Comparison between holographic deformed AdS and soft wall models for fermions

We propose a sequence of steps and a generic transformation for connecting common thermodynamic quantities considered in asymptotically anti-de Sitter black hole thermodynamics in the bulk and those that are appropriate for CFT thermodynamics in the boundary. We do this by constructing a “varying-G map”, where G is the gravitational constant, and demonstrate its usefulness by considering various examples.

Iarley P. Lobo

João Paulo Morais Graça

Eduardo Folco Capossoli

A varying gravitational constant map in asymptotically AdS black hole thermodynamics

In higher dimensions, we study degenerate-higher-order-scalar-tensor theories and we derive solutions that resemble the Schwarzschild anti–de Sitter black holes. We compute their thermodynamic quantities following the Wald formalism, satisfying the first law of thermodynamics and a higher dimensional Smarr relation. Constructing a Noether charge with a suitable choice of a spacelike Killing vector, we obtain the shear viscosity of the nongravitational dual field theory, where for a suitable choice of the couplings functions, the Kovtun-Son-Starinets bound is violated. These results are corroborated by the calculation of the Green’s functions following the Kubo formalism.

Chile

Moisés Bravo-Gaete

Shear viscosity from black holes in generalized scalar-tensor theories in arbitrary dimensions

We consider a bottom-up AdS/QCD model with a conformal exponential deformation <math><msup><mrow><mi>e</mi></mrow><mrow><msub><mrow><mi>k</mi></mrow><mrow><mi>I</mi></mrow></msub><mspace width="0.2em"></mspace><msup><mrow><mi>z</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></msup></math> on a Lorentz invariant AdS background, where <math><msub><mrow><mi>k</mi></mrow><mrow><mi>I</mi></mrow></msub></math> stands for the scale <math><msub><mrow><mi>k</mi></mrow><mrow><mi>π</mi></mrow></msub></math> that fixes confinement in the pion case and <math><msub><mrow><mi>k</mi></mrow><mrow><mi>γ</mi></mrow></msub></math> for the kinematical energy scale associated with the virtual photon. In this model we assume the conformal dimension associated with the operator that creates pions at the boundary as <math><mi>Δ</mi><mo>=</mo><mn>3</mn></math>, as in the original bottom-up AdS/QCD proposals. Regarding the geometric slope related to photon field <math><msub><mrow><mi>k</mi></mrow><mrow><mi>γ</mi></mrow></msub></math>, we analyze two cases: constant and depending on the transferred momentum q. In these two cases we computed the electromagnetic pion form factor as well as the pion radius. We compare our results with experimental data as well as other theoretical (holographic and non-holographic) models. In particular, for the momentum dependent scale, we find good agreement with the available experimental data as well as non-holographic models.

Miguel Angel Martín Contreras

China

Danning Li

Alfredo Vega

Pion form factor from an AdS deformed background

In this work, we consider a massive gauge boson field in <math><mrow><msub><mrow><mi>AdS</mi></mrow><mrow><mn>5</mn></mrow></msub></mrow></math> dual to odd glueball states with twist-5 operator in 4D Minkowski spacetime. Introducing an IR cutoff, we break the conformal symmetry of the boundary theory allowing us to calculate the glueball masses with odd spins using Dirichlet and Neumann boundary conditions. Then, from these masses, we construct the corresponding Regge trajectories associated with the odderon. Our results are compatible with the ones in the literature.