Stiff phases in strongly coupled gauge theories with holographic duals

• DOI: 10.1007/jhep11(2017)031
• Publication Date: 2017-11-09T10:49:47Z
• Authors: Christian Ecker; Carlos Hoyos; Niko Jokela; David Rodríguez F...; Aleksi Vuorinen
• Keywords: High Energy Physics - Theory; High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory; FOS: Physical sciences; QC770-798; 01 natural sciences; Gauge-gravity correspondence; Physical sciences; Nuclear Theory (nucl-th); High Energy Physics - Theory (hep-th); Nuclear and particle physics. Atomic energy. Radioactivity; 0103 physical sciences; Holography and quark-gluon plasmas; Astrophysics - High Energy Astrophysical Phenomena

Abstract

According to common lore, Equations of State of field theories with gravity duals tend to be soft, with speeds of sound either below or around the conformal value of

$$ {\upupsilon}_s=1/\sqrt{3} $$

υ s

= 1 /

3

. This has important consequences in particular for the physics of compact stars, where the detection of two solar mass neutron stars has been shown to require very stiff equations of state. In this paper, we show that no speed limit exists for holographic models at finite density, explicitly constructing examples where the speed of sound becomes arbitrarily close to that of light. This opens up the possibility of building hybrid stars that contain quark matter obeying a holographic equation of state in their cores.