【正文】 On Holographic (stringy ) Baryons Imperial College August 09 work done with V. Kaplunovsky G. Harpaz ,N. Katz and Introduction Holography is a useful tool in discussing the physics of glueballs and mesons. Baryons can be described as a semiclassical stringy configurations. In large N baryons require a special treatment. This leads for instance to a description in terms of skyrmions. The holographic duals of baryons are instantons of a five dimensional flavor gauge theory. Relating SUGRA predictions to a stringy picture. Modern stringy baryons versus the “old” picture We will put emphasis on parison to data. Outline The Regge trajectories of mesons revisited Stringy holographic baryons Does the baryonic vertex have a trace in data The stability of stringy baryons, simulation Confining background the Sakai Sugimoto model Baryons as flavor gauge instantons Baryonic properties in a genrealized model Attraction between nucleons Summary Are we back in square one? Regge trajectories revisited Since excited baryons, as we will see later, have a shape of a single string, lets discuss first stringy mesons. On the probe branes there are only scalars and vectors so there are no candidates for higher spin mesons. Apart from special tayllored models SUGRA does not admit the linearity of M2 ~ n Mesons and baryons admit Regge behavior M2 ~ J and hence are described by semiclassical strings. Regge trajectories of baryons The holographic Regge mesons are described by semiclassical strings that end on the flavor probe branes in the ``confining background” We solve the the equations of motion associated with the NambuGoto action in a confining background. An approximate solution takes the form of |___| The same relations between the Mass and the angular momentum follow from a system of an open string with massive endpoints in flat spacetime. This is similar to old models of mesons that include a string with massive endpoints In the small mass limit wR 1 In the large mass limit wR 0 Quark masses We refer to the mass parameter as “string endpoint mass” Mmes~ Tst L + m1sep + m2sep msep is neither mQCD nor constituent mass GOR relation tells us that mp2~ mQCDqq/fp2 In the SS model mp =0 mQCD =0 In the generalized SS with u0 uL mp =0 mQCD =0 msep mQCD _ 0??? qq0_ ??? qqTo turn on a QCD mass or more generally an ( (nonlocal) operator that breaks explicitly chiral symmetry One can either introduce a ``tachyonic DBI” (Casero, Kiritsis and Paredes。 Bergman, Seki , Dhar Nag or introduce an open Wilson line (Aharony Kutasov) Both admit the GOR relation Semiclassical quantization So far we have described the classical string To quantize it we introduce quantum fluctuations Tseytlin Canonical quantization via the Virasoro constraints The frequencies wn=Kn are given by sym antisym A is given in terms of the endpoint velocities There is no exact expression of the quatization of the string with the massive endpoints. For the low mass case one can use the intercept of the massless case so that For high mass we find Fitting to experimental data Holography is valid in ceretain limits like large N and large l The confining backgrounds like SS is dual to a QCDlike theory. Nevertheless with some “Huzpa” and since we related the holographic model