We revisit some aspects of the stringy approach to dipole-dipole interactions, scattering and entanglement in QCD, using the Nambu-Goto (NG) string, without recourse to holography. We first show that the potential between two static dipoles exchanging closed NG strings is attractive at all separations. Underlining the exchange there is an emergent entropy, that is dominated by the tachyon at large separation, and vanishes at short separation, a measure of the confinement-deconfinement transition. The same tachyon is dominant in the scattering amplitude, as a correlator of two Wilson loops for two fixed dipole-like hadrons separated at large rapidity gap, where the contribution of the worldsheet fermions is included. While the tachyon causes the mean string bit density to grow exponentially with the rapidity, the total scattering cross section still satisfies the Froissart bound by quantum shadowing. The stringy scattering exchange also carries an entanglement entropy, that saturates when the bound is reached. For hadrons with varying dipole sizes, the tachyon exchange takes place in hyperbolic space in the conformal limit. The result for the full S-matrix is reminiscent of the one from Mueller$^\prime$s evolved dipole wavefunction, for the total dipole-dipole cross section in perturbative QCD.
Testing Nambu-Goto approximation of cosmic string by lattice field simulations
International Centre for Theoretical Physics Asia-Pacific (ICTP-AP)（国际理论物理中心亚太地区）；University of Chinese Academy of Sciences (UCAS)（中国科学院大学）；Taiji Laboratory for Gravitational Wave Universe（太极引力波宇宙实验室）；Chongqing University（重庆大学）；Peking University（北京大学）；Beijing Laser Acceleration Innovation Center（北京激光加速创新中心）
The Abdus Salam ICTP（阿卜杜斯·萨拉姆国际理论物理中心）；Institute for Fundamental Physics of the Universe（基础物理宇宙研究所）；Department of Applied Mathematics and Theoretical Physics, University of Cambridge（剑桥大学应用数学与理论物理系）；Center for Theoretical Physics of the Universe, Institute for Basic Science (IBS)（韩国基础科学研究所宇宙理论物理中心）；CAPA & Departamento de Física Teórica, Universidad de Zaragoza（萨拉戈萨大学理论物理部及CAPA）
