Holographic Fluid Research Articles

Holographic fluids from 5D dilaton gravity

We study a solvable class of five-dimensional dilaton gravity models that continuously interpolate between anti-de Sitter (AdS5), linear dilaton (LD5) and positively curved spacetimes as a function of a continuous parameter ν. The dilaton vacuum expectation value is set by a potential localized on a flat brane. We chart the elementary properties of these backgrounds for any admissible ν, and determine stability conditions of the brane-dilaton system. We find that the spectrum of metric fluctuations can be either continuous or discrete. It features a massless graviton mode confined between the brane and the curvature singularity, and a massive radion mode tied to brane-dilaton stability. We show that, in the presence of a bulk black hole, the holographic theory living on the brane features a perfect fluid. The equation of state of the holographic fluid interpolates between radiation, pressureless matter and vacuum energy as a function of ν. This extends earlier findings on holographic fluids. Our results suggest that the thermodynamics of the fluid mirrors precisely the thermodynamics of the bulk black hole.

Holographic turbulence from a random gravitational potential

We study the turbulent dynamics of a relativistic (2 + 1)-dimensional fluid placed in a stochastic gravitational potential. We demonstrate that the dynamics of the fluid can be obtained using a dual holographic description realized by an asymptotically Anti-de Sitter black brane driven by a random boundary metric. Using the holographic duality we study the energy power spectrum of a fluid with an inverse energy cascade and show that it is compatible with that of a compressible fluid flow. We calculate the local energy dissipation and the local fluid velocity distribution which provide other measures of the holographic fluid turbulence.

Implementation of cosmological bounce inflation with Nojiri–Odintsov generalized holographic dark fluid

This work reports a study on bounce cosmology with a highly generalized holographic dark fluid inspired by Nojiri and Odintsov [Eur. Phys. J. C 77 (2017) 1–8]. The holographic dark fluid that is mostly used for late-time acceleration has been implemented to reconstruct toward realization of cosmological bounce. We first used the most generalized Nojiri–Odintsov (NO) cutoff to implement the holographic dark fluid. Accordingly, we have reconstructed this dark fluid via some solutions of scale factors. With those solutions, we have explored the evolution of different cosmological parameters. We have examined the effects of each reconstructed parameter in the context of the realization of the cosmic bounce. Next, we use the analytical inferences of the scalar spectral index, tensor-to-scalar ratio, and slow-roll characteristics of the model to study a bounce inflationary scenario. Since inflation is usually associated with the existence of scalar fields, we looked at a possible relationship between NO generalized holographic dark energy and scalar field models. Plotting the evolution of the potential results from the scalar fields against time. Finally, we investigated the GSL of thermodynamics in the pre- and post-bounce scenarios.

Cosmology of Barrow holographic QCD ghost dark energy and a look into the thermodynamics

The present study endeavours to study the cosmology of QCD ghost dark energy based on Barrow holographic fluid, a particular example of Nojiri-Odintsov holographic dark energy (2006, General Relativity and Gravitation, 38, 1285–1304); (2017, The European Physical Journal C, 77, 1–8). The Hubble parameter is reconstructed and according the equation of state parameter is reconstructed for the Barrow holographic QCD ghost dark energy. It is observed that the effective equation of state parameter has a transition from quintessence to phantom and for the current universe the equation of state parameter is very close to −1. The deceleration parameter is computed based on the reconstructed Hubble parameter and it is observed that the model can have a transition from decelerated to accelerated universe. The statefinder trajectories are plotted and an interpolation between dust and ΛCDM phases is observed. Finally, the thermodynamics is studied considering apparent horizon as the enveloping horizon of the Universe.

Holography of linear dilaton spacetimes from the bottom up

The linear dilaton (LD) background is the keystone of a string-derived holographic correspondence beyond AdSd+1/CFTd. This motivates an exploration of the (d+1)-dimensional linear dilaton spacetime (LDd+1) and its holographic properties from the low-energy viewpoint. We first notice that the LDd+1 space has simple conformal symmetries, that we use to shape an effective field theory (EFT) on the LD background. We then place a brane in the background to study holography at the level of quantum fields and gravity. We find that the holographic correlators from the EFT feature a pattern of singularities at certain kinematic thresholds. We argue that such singularities can be used to bootstrap the putative d-dimensional dual theory using techniques analogous to those of the cosmological bootstrap program. Turning on finite temperature, we study the holographic fluid emerging on the brane in the presence of a bulk black hole. We find that the holographic fluid is pressureless for any d due to a cancellation between Weyl curvature and dilaton stress tensor, and verify consistency with the time evolution of the theory. From the fluid thermodynamics, we find a universal temperature and Hagedorn behavior for any d. This matches the properties of a CFT2 with large TT¯ deformation, and of little string theory for d=6. We also find that the holographic fluid entropy exactly matches the bulk black hole Bekenstein-Hawking entropy. Both the fluid equation of state and the spectrum of quantum fluctuations suggest that the d-dimensional dual theory arising from LDd+1 is generically gapped. Published by the American Physical Society 2024

Intermediate inflation through Nojiri–Odintsov holographic dark fluid with the cosmological settings of Kaniadakis

This study is inspired by the generalized holographic cut-off proposed by Nojiri and Odintsov (S. I. Nojiri and S. D. Odintsov, Unifying phantom inflation with late-time acceleration: Scalar phantom–non-phantom transition model and generalized holographic dark energy, Gen. Relativ. Gravit. 38 (2006) 1285–1304) as it aims to have an understanding of the Kaniadakis holographic dark fluid, a particular representative of Nojiri–Odintsov holographic dark energy. To realize inflation and late time acceleration of the universe, we have considered this generalized form of holographic fluid as the fluid for realization of inflationary scenario. Here, inflation has a holographic origin, namely that its source is the Kaniadakis holographic energy density. The inflationary cosmology of Kaniadakis holographic dark fluid has been have explored by assuming that the scale factor is an intermediate scale factor. Several constraints have been derived throughout the study in relation to late time acceleration and early inflation. To study the warm inflation with this holographic origin, we have computed tensor-to-scalar ratio for different values of the number of e-fold and warm inflation has been realized in a high dissipative regime.

Probing the cosmology of f(Q,T) gravity with holographic background fluid

In this work, we have investigated the cosmology of holographic origin within modified [Formula: see text] gravity framework by employing different forms of the scale factor viz. power law, intermediate, emergent, and logamediate forms. The reconstruction of [Formula: see text] gravity is done by assuming the generalized Holographic Dark Energy as the background fluid where the IR cut-off is considered [Formula: see text]. We consider two cosmological models corresponding to the intermediate and emergent scale factors. By choosing a linear combination of Q and T in each case, we analyze the equation of state (EoS) parameter. Considering the intermediate and logamediate scale factors, the reconstruction of [Formula: see text] gravity is achieved using the holographic fluid as background fluid without any functional form assumption for f. In some cases, it is observed that the EoS parameter could cross phantom boundary in later stages and thus indicate the possibility of avoidance of big rip.

Generalized cutoff for late time acceleration and inflation: The cosmology of holographic fluid

Motivated by the work of Nojiri et al. [Phys. Lett. B 797 (2019) 134829], we utilize the holographic principle in the early universe to realize the holographic origin through inflation. A similar argument can be made for its well-researched late-time application, and the early-time horizon contraction naturally boosts holographic energy density at inflationary scales. After accounting for the IR cutoff adjustment and using holographic Ricci dark energy as the inflationary fluid, we have shown the significance of [Formula: see text] in the inflation realization. For holographic Ricci dark fluid’s potential to realize inflation, several restrictions were derived. The e-folding number was used to discuss inflationary observables and determine the slow-roll parameters. The study covered the effects of reconstructing the IR cutoff and the potential for inflation to be realized after taking into account holographic Ricci dark energy as a special instance of the most generalized Nojiri–Odintsov holographic dark energy [S. Nojiri and S. D. Odintsov, Gen. Relativ. Gravit. 38 (2006) 1285–1304]. Additionally, some time intervals for the potential of inflation have been calculated, and the behavior of the equation of state parameter has also been discussed.

Holographic description of the dissipative unified dark fluid model with axion field

In this paper, we extend an axion [Formula: see text] gravity model, and apply the holographic principle to describe in a unifying manner the early and the late-time universe when the general equation-of-state (EoS) contains a bulk viscosity. We assume a spatially flat Friedmann–Robertson–Walker (FRW) universe model. We use a description based on the generalized infrared-cutoff holographic dark energy proposed by Nojiri and Odintsov [Eur. Phys. J. C 77 (2017) 528; Gen. Relativ. Gravit. 38 (2006) 1285], and explore the evolution of the universe when the EoS describes the asymptotic behavior between the dust in the early universe and the late universe. We explore various forms of the bulk viscosity, and calculate analytical expressions for the infrared cutoffs in terms of the particle horizon. In this way, we obtain a unifying description of the early and the late-time universe in the presence of axion matter, via a viscous holographic fluid model.

A truncated scale factor to realize cosmological bounce under the purview of modified gravity

AbstractThe present paper reports a study on bounce realization with a truncated scale factor and the holographic fluid taken in the form of holographic Ricci Dark Energy, which is a particular case of holographic Nojiri–Odintsov model (Nojiri & Odintsov, 2006, Gen. Relativ. Gravit., 38(8), 1285). We have investigated the realization of bounce due to the application of a holographic fluid in the early scenario of the universe. We started with a de‐Sitter scale factor in our study and derived two modified forms using Taylor's series expansion. After studying the behavior of the resulting Hubble parameter, we identified as the suitable form of the scale factor to realize the bounce. It satisfied the conditions , , and before, at, and after the turn‐around point. We have also observed that the resulting equation of state (EoS) parameter violates the null energy condition required by the bounce realization. We have studied the bounce scenario in a modified gravity framework and derived the slow roll parameters. We have studied the behavior of the potential along with the slow‐roll parameters in this bouncing scenario.

Holographic fluids: A thermodynamic road to quantum physics

Quantum mechanics, superfluids, and capillary fluids are closely related: It is thermodynamics that links them. In this paper, the Liu procedure is used to analyze the thermodynamic requirements. A comparison with the traditional method of divergence separation highlights the role of spacetime. It is shown that perfect Korteweg fluids are holographic. The conditions under which a complex field can represent the density and velocity fields of the fluid, and where the complex scalar field becomes a wave function of quantum mechanics, are explored. The bridge between the field and particle representations of a physical system is holography, and the key to holography is the Second Law of Thermodynamics.

Holographic dissipation from the symplectic current

We develop analytic techniques to construct the leading dissipative terms in a derivative expansion of holographic fluids. Our basic ingredient is the Crnkovic-Witten symplectic current of classical gravity which we use to extract the dissipative transport coefficients of holographic fluids, assuming knowledge of the thermodynamics and the near horizon geometries of the bulk black hole geometries. We apply our techniques to non-conformal neutral fluids to reproduce previous results on the shear viscosity and generalise a known expression for the bulk viscosity.

Micro- and Nanoscale Imaging of Fluids in Water Using Refractive-Index-Matched Materials.

Three-dimensional (3D) visualization in water is a technique that, in addition to macroscale visualization, enables micro- and nanoscale visualization via a microfabrication technique, which is particularly important in the study of biological systems. This review paper introduces micro- and nanoscale 3D fluid visualization methods. First, we introduce a specific holographic fluid measurement method that can visualize three-dimensional fluid phenomena; we introduce the basic principles and survey both the initial and latest related research. We also present a method of combining this technique with refractive-index-matched materials. Second, we outline the TIRF method, which is a method for nanoscale fluid measurements, and introduce measurement examples in combination with imprinted materials. In particular, refractive-index-matched materials are unaffected by diffraction at the nanoscale, but the key is to create nanoscale shapes. The two visualization methods reviewed here can also be used for other fluid measurements; however, because these methods can used in combination with refractive-index-matched materials in water, they are expected to be applied to experimental measurements of biological systems.

Holographic representation of the unified early and late universe via a viscous dark fluid

In this paper, we apply the holographic principle for describing in a unifying way the early and the late-time universe, when the general equation of state contains a bulk viscosity. We use the idea of a generalized cut-off holographic dark energy introduced by Nojiri and Odintsov (2006, 2017), and study the evolution of the universe when the equation of state has two power-law asymptotes. Analytical expressions for the infrared cut-offs in terms of the particle horizon are obtained. The energy conservation laws as derived from the holographic point of view, are given for various forms of the thermodynamic parameters and for various forms of the bulk viscosity. As a result, we obtain a unifying description of the early and the late-time universe in the presence of a viscous holographic fluid.

Hydrodynamization times of a holographic fluid far from equilibrium

We investigate several hydrodynamization times for an ensemble of different far-from-equilibrium solutions of the strongly coupled $\mathcal{N}=4$ supersymmetric Yang-Mills plasma undergoing Bjorken flow. For the ensemble of initial data analyzed in the present work, we find that, with typical tolerances between 3% to 5%, the average hydrodynamization time associated with the late time convergence of the pressure anisotropy to the corresponding Borel resummed hydrodynamic attractor is approximately equal to the average hydrodynamization time associated with the Navier-Stokes result, while both are shorter than the average hydrodynamization time associated with second-order hydrodynamics. On the other hand, we find that the entropy density of the different solutions coalesces to second-order hydrodynamics long before entering in the Navier-Stokes regime. A clear hierarchy between the different average hydrodynamization times of the Bjorken expanding fluid is established for the set of analyzed initial data, comprising also some solutions which, whilst satisfying the dominant and the weak energy conditions at the initial time, evolve such as to transiently violate one or both conditions when the fluid is still far from equilibrium. In particular, solutions violating the weak energy condition are generally found to take a longer time to enter in the hydrodynamic regime than the other solutions.

Inflationary Dynamics of Tsallis Holographic Scalar Field Models in Chern-Simons Modified Gravity

The present study report reconstruction schemes for tachyon scalar field model of Dark Energy through Tsallis holographic dark fluid under the framework of Chern-Simons modified gravity. Emergent scale factor has been assumed. Reproducing the conservation equation for a coupled model with interaction term we have reconstructed the scalar field and the corresponding potential. The reconstructed energy density have been plotted for the case. Evolutionary behaviour of potential for the case have been pictorially presented.

Linearized dispersion relations in viscous relativistic hydrodynamics

We compute the dispersion relations for scalar, vector and tensor modes of a viscous relativistic fluid, linearized around an equilibrium solution, for a divergence type theory (which, in the linearized theory, includes Israel-Stewart theory and anisotropic hydrodynamics as particular cases) and contrast them to the corresponding results derived from kinetic theory under the relaxation time approximation, and from causal first order theories. We conclude that all approaches give similar dynamics for the scalar and vector modes, while the particular divergence type theory presented here also contains propagating damped tensor waves, in agreement with kinetic theory. Nonhydrodynamic tensor modes are also a feature of holographic fluids. These results support the application of hydrodynamics in problems involving the interaction between fluids and gravitational waves.

Analysis of different scenarios with new Tsallis holographic dark energies and bulk viscous fluid in the framework of Chern–Simons modified gravity

In this work, we have studied various cosmological parameters in the presence of viscous new Tsallis holographic dark energies for interacting scenarios in the framework of Chern–Simons modified gravity. The bulk viscosity has been considered with the bulk viscous pressure chosen in the form [Formula: see text]. Hubble parameter [Formula: see text] has been obtained from the above choice of scale factor and in this viscous scenario, the effective pressure has been obtained in Chern–Simons framework whose field equation, cosmological consequences have been investigated. It has been observed that for the interaction scenario in the presence of bulk viscosity the EoS parameter is staying above [Formula: see text], which indicates quintessence behavior. Hence, for the universe filled with a bulk viscous fluid can have the possibility of avoidance of big-rip, although the earlier transition from quintessence to phantom is not avoidable.

Aspects of holography of Taub-NUT- AdS4 spacetimes

In this paper we consider aspects of the holographic interpretation of Taub-NUT-${\mathrm{AdS}}_{4}$. We review our earlier results which show that ${\mathrm{TNAdS}}_{4}$ gives rise to a holographic three-dimensional conformal fluid having constant vorticity. We then study the holographic relevance of the Misner string by considering bulk scalar fluctuations. The scalar fluctuations organize naturally into representations of the $SU(2)\ifmmode\times\else\texttimes\fi{}\mathbb{R}$ isometry algebra. If we require the string's invisibility we obtain a Dirac-like quantization relating the frequency of the scalar field modes to the NUT charge. As the latter quantity determines the total vorticity flux of the boundary fluid, we argue that such an assumption allows for a holographic interpretation of ${\mathrm{TNAdS}}_{4}$ as a nondissipative superfluid whose excitations are quantized vortices. Alternatively, if we regard the Misner string as a physical object, as has recently been advocated for thermodynamically, the aforementioned quantization conditions are removed, and we find that ${\mathrm{TNAdS}}_{4}$ corresponds to a holographic fluid whose dissipative properties are probed as usual by the complex quasinormal modes of the bulk fluctuations. We show that such quasinormal modes are, perhaps surprisingly, organized into infinite-dimensional nonunitary representations of the isometry algebra.

Observational constraints on the cosmology with holographic dark fluid

We consider the holographic Friedman–Robertson–Walker (hFRW) universe on the 4-dimensional membrane embedded in the 5-dimensional bulk spacetime and fit the parameters with the observational data. In order to fully account for the phenomenology of this scenario, we consider the models with the brane cosmological constant and the negative bulk cosmological constant. The contribution from the bulk is represented as the holographic dark fluid on the membrane. We derive the universal modified Friedmann equation by including all of these effects in both braneworld and holographic cutoff approaches. For three specific models, namely, the pure hFRW model, the one with the brane cosmological constant, and the one with the negative bulk cosmological constant, we compare the model predictions with the observations. The parameters in the considered hFRW models are constrained with observational data. In particular, it is shown that the model with the brane cosmological constant can fit data as well as the standard ΛCDM universe. We also find that the σ8 tension observed in different large-structure experiments can be effectively relaxed in this holographic scenario.