Perturbative Results without Diagrams
نویسنده
چکیده
Higher-order perturbative calculations in Quantum (Field) Theory suffer from the factorial increase of the number of individual diagrams. Here I describe an approach which evaluates the total contribution numerically for finite temperature from the cumulant expansion of the corresponding observable followed by an extrapolation to zero temperature. This method (originally proposed by Bogolyubov and Plechko) is applied to the calculation of higher-order terms for the ground-state energy of the polaron. Using state-of-the-art multidimensional integration routines 2 new coefficients are obtained corresponding to a 4and 5-loop calculation.
منابع مشابه
A Perturbative Window into Non-Perturbative Physics
We argue that for a large class of N = 1 supersymmetric gauge theories the effective superpotential as a function of the glueball chiral superfield is exactly given by a summation of planar diagrams of the same gauge theory. This perturbative computation reduces to a matrix model whose action is the tree-level superpotential. For all models that can be embedded in string theory we give a proof ...
متن کاملResummation of Cactus Diagrams in the Clover Improved Lattice Formulation of QCD
We extend to the clover improved lattice formulation of QCD the resummation of cactus diagrams, i.e. a certain class of tadpole-like gauge invariant diagrams. Cactus resummation yields an improved perturbative expansion. We apply it to the lattice renormalization of some two-fermion operators improving their one-loop perturbative estimates.
متن کاملProof of perturbative gauge invariance for tree diagrams to all orders
It is proved that classical BRS-invariance of the Lagrangian implies perturbative gauge invariance for tree diagrams to all orders. The proof applies in particular to the Einstein Hilbert Largrangian of gravity.
متن کاملPerturbative Corrections for Staggered Four-fermion Operators
We present results for one-loop matching coefficients between continuum fourfermion operators, defined in the Naive Dimensional Regularization scheme, and staggered fermion operators of various types. We calculate diagrams involving gluon exchange between quark lines, and “penguin” diagrams containing quark loops. For the former we use Landau gauge operators, with and without O(a) improvement, ...
متن کاملPerturbation theory without diagrams: the polaron case.
Higher-order perturbative calculations in quantum (field) theory suffer from the factorial increase of the number of individual diagrams. Here I describe an approach which evaluates the total contribution numerically for finite temperature from the cumulant expansion of the corresponding observable followed by an extrapolation to zero temperature. This method (originally proposed by Bogolyubov ...
متن کامل