Empedocle e la bonifica di Selinunte: un breve riesame

Alcune considerazioni intorno a un passo di Diogene Laerzio, secondo il quale il filosofo Empedocle avrebbe attuato un'operazione di bonifica a Selinunte, e sulla possibilità di trovare riscontri in proposito

Hadron production at the LHC: Any indication of new phenomena

We confront soft Pomeron and gluon saturation models with the first LHC data on inclusive hadron production. We claim that while the first type of models are not able to describe some part of the LHC data, the Colour-Glass-Condensate (gluon saturation) approach gives an adequate description of the data. Here, we compare our published predictions with the recently available 7 TeV data. We firmly believe that if further experimental measurements confirm that the gluon saturation works, it will be a major discovery.Comment: 8 pages, 12 figure, Based on two talks given by authors at Diffraction 2010, Otranto (Lecce), Italy, September 10-15, 201

AdS black disk model for small-x DIS

Using the approximate conformal invariance of QCD at high energies we consider a simple AdS black disk model to describe saturation in DIS. Deep inside saturation the structure functions have the same power law scaling, F_T ~ F_L ~ 1/x^w, where w is related to the expansion rate of the black disk with energy. Furthermore, the ratio F_L /F_T is given by the universal value (1+w)/(3+w), independently of the target. For virtual photon-photon scattering at high energies we obtain explicit expressions and ratios for the total cross sections of transverse and longitudinal photons in terms of the single parameter w.Comment: 5 pages. Minor correction

Empedocle e la bonifica di Selinunte: un breve riesame

Alcune considerazioni intorno a un passo di Diogene Laerzio, secondo il quale il filosofo Empedocle avrebbe attuato un'operazione di bonifica a Selinunte, e sulla possibilit\ue0 di trovare riscontri in proposito

MHV amplitude for 3->3 gluon scattering in Regge limit

We calculate corrections to the BDS formula for the six-particle planar MHV amplitude for the gluon transition 3->3 in the multi-Regge kinematics for the physical region, in which the Regge pole ansatz is not valid. The remainder function at two loops is obtained by an analytic continuation of the expression derived by Goncharov, Spradlin, Vergu and Volovich to the kinematic region described by the Mandelstam singularity exchange in the crossing channel. It contains both the imaginary and real contributions being in agreement with the BFKL predictions. The real part of the three loop expression is found from a dispersion-like all-loop formula for the remainder function in the multi-Regge kinematics derived by one of the authors. We also make a prediction for the all-loop real part of the remainder function multiplied by the BDS phase, which can be accessible through calculations in the regime of the strong coupling constant.Comment: 6 pages, 4 figure

High Energy Behavior of a Six-Point R-Current Correlator in N=4 Supersymmetric Yang-Mills Theory

We study the high energy limit of a six-point R-current correlator in N=4 supersymmetric Yang-Mills theory for finite N_c. We make use of the framework of perturbative resummation of large logarithms of the energy. More specifically, we apply the (extended) generalized leading logarithmic approximation. We find that the same conformally invariant two-to-four gluon vertex occurs as in non-supersymmetric Yang-Mills theory. As a new feature we find a direct coupling of the four-gluon t-channel state to the R-current impact factor.Comment: 47 page

Vector meson production at low x from gauge/gravity duality

We use gauge/gravity duality to study vector meson (J/?, ? 0 , ?, ?) production in electron-proton scattering, in the limit of high center of mass energy at fixed momentum transfer, corresponding to the limit of low Bjorken x, where the process is dominated by pomeron exchange. Our approach considers the pomeron at strong coupling, described by the graviton Regge trajectory in AdS space with a hard-wall to mimic confinement effects. Both the proton and vector mesons are described by simple holographic wave functions in AdS. This model agrees with HERA H1 data with a ? 2 per degree of freedom below one on total cross-sections, and below two on differential cross-sections, confirming the success of previous studies that model low x DIS and DVCS using gauge/gravity duality

Soft photon anomaly and gauge/string duality

Motivated by the recent DELPHI report on the anomalous photon production in e^+e^- annihilation, we exactly calculate the inclusive cross section of soft photons in the strong coupling limit of N=4 super Yang-Mills. We find that the energy distribution is that of the Bremsstrahlung, while the angular distribution is spherical. Our result elucidates a new non-perturbative source of soft photons not associated with the final state hadronic Bremsstrahlung.Comment: 22 page