【導(dǎo)讀】OnHolographic(stringy). Baryons. G.Harpaz,N.Katzand. Introduction. configurations.Outline. spinmesons.M2~J. background”。time.Quarkmasses. endpointmass”。Mmes~TstL+m1sep+m2sep. mp2~mQCD<qq>/fp2. IntheSSmodelmp=0mQCD=0. mp=0mQCD=0. msepmQCD. _0???qq. 0_???qq. symmetry. (Casero,KiritsisandParedes;Bergman,Seki,DharNag. Tseytlin. Thefrequencieswn=Knaregivenby. sym. anti-sym. Forhighmasswefind. andlargel. QCD-liketheory.Neverthelesswit

　　

【正文】 z1. This may signal that the Sakai Sugimoto picture of baryons has to be modified ( Baryon backreaction, DBI expansion, coupling to scalars) One flavor baryons Both from the point of view of QCD and of the stringy configuration there is no reason why there should not be also baryons for Nf =1. However, there is no nontrivial instanton in the abelian gauge theory of Nf =1. This is presumably the analog of no Skyrme model for one flavor. Holographic Nuclear force Hashimoto Sakai and Sugimoto showed that there is a hard core repulsive potential between two baryons ( instantons) due to the abelian interaction of the form VU(1) ~ 1/r2 In nuclear physics one believes that there is repulsion between nucleons due to exchange of isoscalar mesons: a vector particle ( omega) and an attraction due to exchange of an scalar ( sigma) The various regions of the nuclear interaction. We expect to find a holographic attraction due to the interaction of the instanton with the fluctuation of the embedding which is the dual of the scalar fields. The attraction term should have the form Lattr ~fTr[F2] In the antipodal case ( the SS model) there is a symmetry under dx4 dx4 and since asymptotically x4 is the transverse direction f~dx4 such an interaction term does not exist. Indeed the 5d effective action for AM and f is For instantons F=*F so there is a petition between repulsion attraction A TrF2 fTr F2 Thus there is also an attraction potential Vscalar ~ 1/r2 The ratio of the attraction to repulsive potential Since the instanton is small u~ u0 The ration of the scalar to u(1) potentials The ratio between the attraction and repulsion in the intermediate zone is Nuclear potential in the far zone We have seen the repulsive hard core and attraction in the intermediate zone. To have stable nuclei the attractive potential has to dominate in the far zone. In holography this should follow from the fact that the isoscalar scalar is lighter that the corresponding vector meson. In SS model this is not the case. Maybe the dominance of the attraction associates with two meson exchange( sigma?). Summary and conclusions We have discussed properties of baryons that follow from the holographic SUGRA picture as well as their stringy description. Unfortunately to bridge the SUGRA and stringy pictures requires t? Hooft parameter ( and hence curvature ) of order 1. ( This may hint for noncritical strings) The modern stringy picture is not so different than the old one. The stringy picture for a baryon with high spin seems to be that of a single string with a quark and a diquark Baryons as instantons lead to a picture that is similar to the Skyrme model. From the results for baryons made out of quarks with string end point masses we deduce that the na239。ve instanton picture should be improved. We showed that on top of the repulsive hard core due to the abelian field there is an attraction potential due the scalar interaction. 1. Holographic mesons Steps needed to create holographic mesons: Allocate a gravity dual of confining gauge dynamics in particular pure YM theory. Add flavor probe branes to incorporate fundamental quarks. Identify the modes on the flavor branes that correspond to the various types of mesons Compute the spectrum and examine its dependence on the excitation number the string endpoint mass, Parity and Charge conjugation . Regge trajectories of mesons ?Rotating bosinic string admits Regge behavior D8 D8 L Nc N