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We discuss the recent progress made in using bottom-up holographic QCD models in calculating hadronic contributions to the anomalous magnetic moment of the muon, in particular the hadronic light-bylight scattering contribution, where holographic QCD naturally satisfies the Melnikov-Vainshtein constraint by an infinite series of axial vector meson contributions. [ABSTRACT FROM AUTHOR]

Description of nuclear matter in the core of neutron stars eludes the main tools of investigation of QCD, such as perturbation theory and the lattice formulation of the theory. Recently, the application of the holographic paradigm (both via top-down and bottom-up models) to this task has led to many encouraging results, both qualitatively and quantitatively. We present our approach to the description of neutron star cores, relying on a simple model of the (double) hard-wall type: we discuss results concerning the nature of homogeneous nuclear matter at high density emerging from the model including a quarkyonic phase, the mass-radius relation for neutron stars, as well as the rather stiff equation of state we have found. We show how, despite the very simple model employed, for an appropriate calibration we are able to obtain neutron stars that only slightly fall short of the observational bounds on radius and tidal deformability. [ABSTRACT FROM AUTHOR]

A brief review of the Witten-Sakai-Sugimoto model is given, which is a top-down holographic model of low-energy QCD with chiral quarks derived from type-IIA superstring theory. The main predictions of the model, in particular concerning meson spectra, the gluon condensate, the QCD string tension, the mass of the η' and of baryons are discussed and compared quantitatively with available experimental and/or lattice results. Then some recent results of potential interest to the physics program at the future FAIR facility are presented: The spectrum of glueballs and their decay rates into pions, and the phase diagram of QCD at finite temperature, density, and magnetic field strength. [ABSTRACT FROM AUTHOR]

In the presence of a chemical potential, the effect of a magnetic field on chiral symmetry breaking goes beyond the well-known magnetic catalysis. Due to a subtle interplay with the chemical potential, themagnetic field maywork not only in favor but also against the chirally broken phase. At sufficiently large coupling, themagnetic field favors the broken phase only for field strengths beyond any conceivable value in nature. Therefore, in the interior of magnetars, a possible transition from chirally broken hadronic matter to chirally symmetric quark matter might occur at smaller densities than previously thought. [ABSTRACT FROM AUTHOR]