Abstract
Holographic QCD at finite baryon number density and zero temperature is studied within the five-dimensional Sakai-Sugimoto model. We introduce a new approximation that models a smeared crystal of solitonic baryons by assuming spatial homogeneity to obtain an effective kink theory in the holographic direction. The kink theory correctly reproduces a first order phase transition to lightly bound nuclear matter. As the density is further increased the kink splits into a pair of half-kink constituents, providing a concrete realization of the previously suggested dyonic salt phase, where the bulk soliton splits into constituents at high density. The kink model also captures the phenomenon of baryonic popcorn, in which a first order phase transition generates an additional soliton layer in the holographic direction. We find that this popcorn transition takes place at a density below the dyonic salt phase, making the latter energetically unfavourable. However, the kink model predicts only one pop, rather than the sequence of pops suggested by previous approximations. In the kink model the two layers produced by the single pop form the surface of a soliton bag that increases in size as the baryon chemical potential is increased. The interior of the bag is filled with abelian electric potential and the instanton charge density is localized on the surface of the bag. The soliton bag may provide a holographic description of a quarkyonic phase.
Highlights
As baryon number density is increased it is natural to expect that the bulk soliton explores more of the holographic direction and this has been interpreted [8] as a holographic realization of the quarkyonic phase [10], where there is a quark Fermi sea with a baryonic Fermi surface
We find that our effective kink model provides an explicit realization of the dyonic salt phase, as the kink splits into a pair of half-kink constituents as the density is increased
As the holographic coordinate corresponds to an energy scale in the boundary theory, understanding this aspect is likely to be the key to a holographic description of the baryonic Fermi surface of a quarkyonic phase
Summary
In our study of the Sakai-Sugimoto model we choose to work with the Yang-Mills theory that results from the non-abelian Dirac-Born-Infeld action at leading order in α. Applying the standard holographic dictionary, in the grand canonical ensemble a baryon chemical potential corresponds to a non-zero boundary value for. The second potential term has an explicit spatial dependence that grows like z−2, which decays fast enough that finite energy considerations impose no conditions on the boundary values of ψ(z) from this term. As this term has a coefficient of β6 at high density it is, at least locally, of more relevance than the first potential term, which has a coefficient of only β4. We examine this possibility by constructing a double layer configuration and calculating its energy as a function of baryon number density
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
