Holographic description of a multiquark star

Abstract

The gauge-gravity duality or the holographic principle is briefly reviewed starting from the AdS/CFT correspondence continuing to the more realistic model of Sakai-Sugimoto. The holographic models of mesons and baryons, constructed in Sakai-Sugimoto model, are also investigated. Their physical properties, especially thermodynamic relations are explored for both confined and deconfined cases. Interestingly, in the deconfined phase, it is found that even though gluons are free to propagate, quarks could form a new bound state with color charges called a multiquark state. The thermodynamics of multiquark states are considered both analytically and numerically. In the core of a dense warm star, it is conceivable that multiquark phase is preferred over the other nuclear phases, provided that the density is sufficiently large and the temperature is not too high. The massive star is assumed to be spherical symmetric and entirely in a deconfined phase due to the high density and a uniform moderate temperature throughout the star therefore it is called a multiquark star. Using the Tolman-Oppenheimer-Volkoff (TOV) equation and the equation of states of the multiquark from the Sakai-Sugimoto model, we established the mass limits of the multiquark star. For typical energy density 10 GeV/fm3, the estimated mass and radius of the hypothetical multiquark star in the limit of large central density are approximately 2.6 - 3.9 solar mass and 15-27 km. The adiabatic index and sound speed distributions of the star are also discussed. It turns out that the sound speed never exceed the speed of light which confirms the compressibility of the multiquark matter at high density and pressure.