7,263 research outputs found
Nested (inverse) binomial sums and new iterated integrals for massive Feynman diagrams
Nested sums containing binomial coefficients occur in the computation of
massive operator matrix elements. Their associated iterated integrals lead to
alphabets including radicals, for which we determined a suitable basis. We
discuss algorithms for converting between sum and integral representations,
mainly relying on the Mellin transform. To aid the conversion we worked out
dedicated rewrite rules, based on which also some general patterns emerging in
the process can be obtained.Comment: 13 pages LATEX, one style file, Proceedings of Loops and Legs in
Quantum Field Theory -- LL2014,27 April 2014 -- 02 May 2014 Weimar, German
Cauchy Type Integrals of Algebraic Functions
We consider Cauchy type integrals with an algebraic function. The main goal is to give
constructive (at least, in principle) conditions for to be an algebraic
function, a rational function, and ultimately an identical zero near infinity.
This is done by relating the Monodromy group of the algebraic function , the
geometry of the integration curve , and the analytic properties of the
Cauchy type integrals. The motivation for the study of these conditions is
provided by the fact that certain Cauchy type integrals of algebraic functions
appear in the infinitesimal versions of two classical open questions in
Analytic Theory of Differential Equations: the Poincar\'e Center-Focus problem
and the second part of the Hilbert 16-th problem.Comment: 58 pages, 19 figure
Iterated Binomial Sums and their Associated Iterated Integrals
We consider finite iterated generalized harmonic sums weighted by the
binomial in numerators and denominators. A large class of these
functions emerges in the calculation of massive Feynman diagrams with local
operator insertions starting at 3-loop order in the coupling constant and
extends the classes of the nested harmonic, generalized harmonic and cyclotomic
sums. The binomially weighted sums are associated by the Mellin transform to
iterated integrals over square-root valued alphabets. The values of the sums
for and the iterated integrals at lead to new
constants, extending the set of special numbers given by the multiple zeta
values, the cyclotomic zeta values and special constants which emerge in the
limit of generalized harmonic sums. We develop
algorithms to obtain the Mellin representations of these sums in a systematic
way. They are of importance for the derivation of the asymptotic expansion of
these sums and their analytic continuation to . The
associated convolution relations are derived for real parameters and can
therefore be used in a wider context, as e.g. for multi-scale processes. We
also derive algorithms to transform iterated integrals over root-valued
alphabets into binomial sums. Using generating functions we study a few aspects
of infinite (inverse) binomial sums.Comment: 62 pages Latex, 1 style fil
Iterated Elliptic and Hypergeometric Integrals for Feynman Diagrams
We calculate 3-loop master integrals for heavy quark correlators and the
3-loop QCD corrections to the -parameter. They obey non-factorizing
differential equations of second order with more than three singularities,
which cannot be factorized in Mellin- space either. The solution of the
homogeneous equations is possible in terms of convergent close integer power
series as Gau\ss{} hypergeometric functions at rational argument. In
some cases, integrals of this type can be mapped to complete elliptic integrals
at rational argument. This class of functions appears to be the next one
arising in the calculation of more complicated Feynman integrals following the
harmonic polylogarithms, generalized polylogarithms, cyclotomic harmonic
polylogarithms, square-root valued iterated integrals, and combinations
thereof, which appear in simpler cases. The inhomogeneous solution of the
corresponding differential equations can be given in terms of iterative
integrals, where the new innermost letter itself is not an iterative integral.
A new class of iterative integrals is introduced containing letters in which
(multiple) definite integrals appear as factors. For the elliptic case, we also
derive the solution in terms of integrals over modular functions and also
modular forms, using -product and series representations implied by Jacobi's
functions and Dedekind's -function. The corresponding
representations can be traced back to polynomials out of Lambert--Eisenstein
series, having representations also as elliptic polylogarithms, a -factorial
, logarithms and polylogarithms of and their -integrals.
Due to the specific form of the physical variable for different
processes, different representations do usually appear. Numerical results are
also presented.Comment: 68 pages LATEX, 10 Figure
The evaluation of Tornheim double sums. Part 1
We provide an explicit formula for the Tornheim double series in terms of
integrals involving the Hurwitz zeta function. We also study the limit when the
parameters of the Tornheim sum become natural numbers, and show that in that
case it can be expressed in terms of definite integrals of triple products of
Bernoulli polynomials and the Bernoulli function .Comment: 23 pages, AMS-LaTex, to appear in Journal of Number Theor
The formal path integral and quantum mechanics
Given an arbitrary Lagrangian function on \RR^d and a choice of classical
path, one can try to define Feynman's path integral supported near the
classical path as a formal power series parameterized by "Feynman diagrams,"
although these diagrams may diverge. We compute this expansion and show that it
is (formally, if there are ultraviolet divergences) invariant under
volume-preserving changes of coordinates. We prove that if the ultraviolet
divergences cancel at each order, then our formal path integral satisfies a
"Fubini theorem" expressing the standard composition law for the time evolution
operator in quantum mechanics. Moreover, we show that when the Lagrangian is
inhomogeneous-quadratic in velocity such that its homogeneous-quadratic part is
given by a matrix with constant determinant, then the divergences cancel at
each order. Thus, by "cutting and pasting" and choosing volume-compatible local
coordinates, our construction defines a Feynman-diagrammatic "formal path
integral" for the nonrelativistic quantum mechanics of a charged particle
moving in a Riemannian manifold with an external electromagnetic field.Comment: 33 pages, many TikZ diagrams, submitted to _Journal of Mathematical
Physics
Large scale analytic calculations in quantum field theories
We present a survey on the mathematical structure of zero- and single scale
quantities and the associated calculation methods and function spaces in higher
order perturbative calculations in relativistic renormalizable quantum field
theories.Comment: 25 pages Latex, 1 style fil
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