We initiate the study of bound state scattering in AdS space at level Witten diagrams. For concreteness, we focus on case with only scalar fields and analyze several basic diagrams which more general reduce to. obtain closed form expressions for their Mellin amplitudes arbitrary conformal dimensions, exhibit interesting behavior. In particular, observe that certain tree-level have same structur...

An approach is elaborated for calculation of “all loop” contributions to the non-singlet evolution kernels from the diagrams with renormalon chain insertions. Closed expressions are obtained for sums of contributions to kernels P (z) for the DGLAP equation and V (x, y) for the “nonforward” ER-BL equation from these diagrams that dominate for a large value of b0, the first β-function coefficient...

We study the pair production of charged Higgs bosons at the CERN Large Hadron Collider in the context of the minimal supersymmetric extension of the standard model. We compare the contributions due to qq̄ annihilation at the tree level and gg fusion, which proceeds at one loop. At small or large values of tanβ, H+H− production proceeds dominantly via bb̄ annihilation, due to Feynman diagrams invo...

Two types of issues were raised by Galperin, Nitzan, and Ratner (GRN). (1) The correct formal diagrammatic definition of the stimulated light emission (SLE) signal in terms of molecular correlation functions and the identification of the sub-set of diagrams that contribute to the Raman signal. (2) What approximations are used to actually compute these correlation functions in the presence of el...

Starting from tree and one-loop tachyon amplitudes of open string theory in the presence of a constant B-field, we explore two problems. First we show that in the noncommutative field theory limit the amplitudes reduce to tree and one-loop diagrams of the noncommutative Φ theory. Next, we check factorization of the one-loop amplitudes in the long cylinder limit. PACS : 11.25.-w, 11.25.Db

We present the two-loop pure gauge contribution to the gluon-gluon scattering amplitude with maximal helicity violation. Our construction of the amplitude does not rely directly on Feynman diagrams, but instead uses its analytic properties in 4 − 2 dimensions. We evaluate the loop integrals appearing in the amplitude through O( ) in terms of polylogarithms.

A full analytic calculation of the two-loop diagrams contributing to the static potential in QCD is presented in detail. Using a renormal-ization group improvement, the \three-loop" potential in momentum space is thus derived and the third coeecient of the-function for the V-scheme is given. The Fourier transformation to position space is then performed, and the result is brieey discussed.

Hard spin-independent three-loop radiative contributions to energy levels in positronium generated by the two-photon-exchange diagrams with one-loop insertions fermion lines and exchanged photons are calculated. This is a next step calculations of all corrections order mα7 inspired new generation precise 1S−2S 2S−2P measurements positronium.

The soft and collinear singularities of general scalar and tensor one-loop N -point integrals are worked out explicitly. As a result a simple explicit formula is given that expresses the singular part in terms of 3-point integrals. Apart from predicting the singularities, this result can be used to transfer singular one-loop integrals from one regularization scheme to another or to subtract sof...