D4 brane probes in gauge/gravity duality

Abstract

We propose a DBI vertex brane + $N_c$ fundamental strings configuration for a probe baryon in the finite-temperature thermal gauge field via AdS/CFT correspondence. In particular, we investigate properties of this configuration in QCD_4 and warped AdS_6\times S^4. We find that, in D4-D8 system, a holographic probe baryon can be described as N_c fundamental strings connecting through a vertex D4 brane wrapped on S^4. In QCD_4 background, a closed vertex can exist in confined phase and can not exist in deconfined phase. In the low temperature region, screening effect still exist in confined phase like meson and the vertex D4 brane dominates the baryon mass. The lower energy state corresponds to vertex brane closer to the radial cut off position (r=r_c) and the higher energy state corresponds to vertex brane a little far away from the cut off position. The high energy limit of this configuration is just like the unclosed vertex brane configuration in a higher temperature deconfined phase. In warped AdS_6\times S^4 background, a closed vertex can exist in deconfined phase and the vertex contains a spike, while fundamental strings are relatively short. Screening length should be defined through the distance between top position of the vertex spike and the boundary.