ACAT 2010

Session

Friday, 26 February - Methodology of Computations in Theoretical Physics

26 Feb 2010, 14:00

Jaipur, India

67. IR subtraction schemes

Dr Paolo Bolzoni (DESY)

26/02/2010, 14:00

Methodology of Computations in Theoretical Physics

Parallel Talk

To compute jet cross sections at higher orders in QCD efficiently one has to deal with infrared divergences. These divergences cancel out between virtual and real corrections once the phase space integrals are performed. To use standard numerical integration methods like Monte Carlo the divergences' cancellation must be performed explicitly. Usually this is done constructing appropriate...

76. Feynman Integral Evaluation by a Sector decomposiTion Approach (FIESTA)

Mikhail Tentyukov (Karlsruhe University)

26/02/2010, 14:30

Methodology of Computations in Theoretical Physics

Parallel Talk

Sector decomposition in its practical aspect is a constructive method used to evaluate Feynman integrals numerically. We present a new program performing the sector decomposition and integrating the expression afterwards. Also the program can be used in order to expand Feynman integrals automatically in limits of momenta and masses with the use of sector decompositions and Mellin--Barnes...

87. Sector decomposition via computational geometry

Dr Toshiaki KANEKO (KEK, Computing Research Center)

26/02/2010, 15:00

Methodology of Computations in Theoretical Physics

Parallel Talk

One of the powerful tools for evaluating multi-loop/leg integrals is sector decomposition, which can isolate infrared divergences from parametric representations of the integrals. The aim of this talk is to present a new method to replace iterated sector decomposition, in which the problems are converted into a set of problems in convex geometry, and then they can be solved by using...

90. Multiple Polylogarithms and Loop Integrals

Yoshimasa Kurihara (KEK)

26/02/2010, 16:00

Methodology of Computations in Theoretical Physics

Parallel Talk

An importance of the multiple-polylog function (MLP) for the calculation of loop integrals was pointed out by many authors. We give some general discussions between MLP and multi-loop integrals from view point of computer algebra.

107. Two-Loop Fermionic Integrals in Perturbation Theory on a Lattice

Dr Roman Rogalyov (IHEP)

26/02/2010, 16:30

Methodology of Computations in Theoretical Physics

Parallel Talk

A comprehensive number of one-loop integrals in a theory with Wilson fermions at $r=1$ is computed using the Burgio--Caracciolo--Pelissetto algorithm. With the use of these results, the fermionic propagator in the coordinate representation is evaluated, making it possible to extend the Luscher-Weisz procedure for two-loop integrals to the fermionic case. Computations are performed with FORM...

2. Unstable-particles pair production in modified perturbation theory in NNLO

Dr Maksim Nekrasov (Institute for High Energy Physics)

26/02/2010, 17:00

Methodology of Computations in Theoretical Physics

Parallel Talk

We consider pair production and decay of fundamental unstable particles in the framework of a modified perturbation theory (MPT) which treats resonant contributions of unstable particles in the sense of distributions. The cross-section of the process is calculated within the NNLO of the MPT in a model that admits exact solution. Universal massless-particles contributions are taken into...