scholarly journals Decomposition of Feynman integrals by multivariate intersection numbers

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Hjalte Frellesvig ◽  
Federico Gasparotto ◽  
Stefano Laporta ◽  
Manoj K. Mandal ◽  
Pierpaolo Mastrolia ◽  
...  
Keyword(s):  
Differential Equations ◽  
Recursive Algorithm ◽  
Intersection Theory ◽  
Direct Decomposition ◽  
Intersection Numbers ◽  
Top Down ◽  
Feynman Integrals ◽  
Direct Derivation ◽  
Potential Applications ◽  
Recent Idea

AbstractWe present a detailed description of the recent idea for a direct decomposition of Feynman integrals onto a basis of master integrals by projections, as well as a direct derivation of the differential equations satisfied by the master integrals, employing multivariate intersection numbers. We discuss a recursive algorithm for the computation of multivariate intersection numbers, and provide three different approaches for a direct decomposition of Feynman integrals, which we dub thestraight decomposition, thebottom-up decomposition, and thetop-down decomposition. These algorithms exploit the unitarity structure of Feynman integrals by computing intersection numbers supported on cuts, in various orders, thus showing the synthesis of the intersection-theory concepts with unitarity-based methods and integrand decomposition. We perform explicit computations to exemplify all of these approaches applied to Feynman integrals, paving a way towards potential applications to generic multi-loop integrals.

A method for constructing solutions of homogeneous partial differential equations: localized waves

1992 ◽  
Vol 437 (1901) ◽  
pp. 673-692 ◽  
Keyword(s):  
Wave Equation ◽  
Partial Differential Equations ◽  
Differential Equations ◽  
Gordon Equation ◽  
Partial Differential ◽  
Wave Solutions ◽  
Propagation Axis ◽  
Potential Applications ◽  
Klein Gordon ◽  
Localized Waves

We introduce a method for constructing solutions of homogeneous partial differential equations. This method can be used to construct the usual, well-known, separable solutions of the wave equation, but it also easily gives the non-separable localized wave solutions. These solutions exhibit a degree of focusing about the propagation axis that is dependent on a free parameter, and have many important potential applications. The method is based on constructing the space-time Fourier transform of a function so that it satisfies the transformed partial differential equation. We also apply the method to construct localized wave solutions of the wave equation in a lossy infinite medium, and of the Klein-Gordon equation. The localized wave solutions of these three equations differ somewhat, and we discuss these differences. A discussion of the properties of the localized waves, and of experiments to launch them, is included in the Appendix.

scholarly journals The diagrammatic coaction beyond one loop

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Samuel Abreu ◽  
Ruth Britto ◽  
Claude Duhr ◽  
Einan Gardi ◽  
James Matthew
Keyword(s):  
Differential Equations ◽  
Hypergeometric Functions ◽  
Differential Forms ◽  
Feynman Graph ◽  
Loop Order ◽  
Feynman Integrals ◽  
Mathematical Properties ◽  
Multiple Polylogarithms ◽  
Complete Set ◽  
General Tool

Abstract The diagrammatic coaction maps any given Feynman graph into pairs of graphs and cut graphs such that, conjecturally, when these graphs are replaced by the corresponding Feynman integrals one obtains a coaction on the respective functions. The coaction on the functions is constructed by pairing a basis of differential forms, corresponding to master integrals, with a basis of integration contours, corresponding to independent cut integrals. At one loop, a general diagrammatic coaction was established using dimensional regularisation, which may be realised in terms of a global coaction on hypergeometric functions, or equivalently, order by order in the ϵ expansion, via a local coaction on multiple polylogarithms. The present paper takes the first steps in generalising the diagrammatic coaction beyond one loop. We first establish general properties that govern the diagrammatic coaction at any loop order. We then focus on examples of two-loop topologies for which all integrals expand into polylogarithms. In each case we determine bases of master integrals and cuts in terms of hypergeometric functions, and then use the global coaction to establish the diagrammatic coaction of all master integrals in the topology. The diagrammatic coaction encodes the complete set of discontinuities of Feynman integrals, as well as the differential equations they satisfy, providing a general tool to understand their physical and mathematical properties.

scholarly journals Feynman integrals and intersection theory

2019 ◽  
Vol 2019 (2) ◽  
Author(s):  
Pierpaolo Mastrolia ◽  
Sebastian Mizera
Keyword(s):  
Intersection Theory ◽  
Feynman Integrals

INTERSECTION THEORY AND TWO-DIMENSIONAL GRAVITY AT GENUS 3 AND 4

1990 ◽  
Vol 05 (26) ◽  
pp. 2127-2134 ◽  
Author(s):  
JAMES H. HORNE
Keyword(s):  
Moduli Space ◽  
Intersection Theory ◽  
Gravity Theory ◽  
Two Dimensional ◽  
Intersection Numbers ◽  
Dimensional Gravity

We show that the k = 1 two-dimensional gravity amplitudes at genus 3 agree precisely with the results from intersection theory on moduli space. Predictions for the genus 4 intersection numbers follow easily from the two-dimensional gravity theory.

scholarly journals FEYNMAN DIAGRAMS AND DIFFERENTIAL EQUATIONS

2007 ◽  
Vol 22 (24) ◽  
pp. 4375-4436 ◽  
Author(s):  
MARIO ARGERI ◽  
PIERPAOLO MASTROLIA
Keyword(s):  
Differential Equations ◽  
Boundary Conditions ◽  
Difference Equations ◽  
Vacuum Polarization ◽  
Feynman Diagrams ◽  
Polarization Tensor ◽  
Photon Propagator ◽  
Feynman Integrals ◽  
Technical Aspects ◽  
Vacuum Polarization Tensor

We review in a pedagogical way the method of differential equations for the evaluation of D-dimensionally regulated Feynman integrals. After dealing with the general features of the technique, we discuss its application in the context of one- and two-loop corrections to the photon propagator in QED, by computing the Vacuum Polarization tensor exactly in D. Finally, we treat two cases of less trivial differential equations, respectively associated to a two-loop three-point, and a four-loop two-point integral. These two examples are the playgrounds for showing more technical aspects about: Laurent expansion of the differential equations in D (around D = 4); the choice of the boundary conditions; and the link among differential and difference equations for Feynman integrals.

scholarly journals Decomposition of Feynman Integrals on the Maximal Cut by Intersection Numbers

2019 ◽  
Author(s):  
Manoj Kumar Mandal ◽  
Hjalte Axel Frellesvig ◽  
Federico Gasparotto ◽  
Stefano Laporta ◽  
Pierpaolo Mastrolia ◽  
...  
Keyword(s):  
Intersection Numbers ◽  
Feynman Integrals

scholarly journals Reduction of Feynman integrals in the parametric representation III: integrals with cuts

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Wen Chen
Keyword(s):  
Phase Space ◽  
Differential Equations ◽  
Momentum Space ◽  
Theta Functions ◽  
Parametric Representation ◽  
Systematic Method ◽  
Integration By Parts ◽  
Feynman Integrals

AbstractPhase space cuts are implemented by inserting Heaviside theta functions in the integrands of momentum-space Feynman integrals. By directly parametrizing theta functions and constructing integration-by-parts (IBP) identities in the parametric representation, we provide a systematic method to reduce integrals with cuts. Since the IBP method is available, it becomes possible to evaluate integrals with cuts by constructing and solving differential equations.

scholarly journals Nanoporous Metallic Films

2021 ◽  
Author(s):  
Swastic ◽  
Jegatha Nambi Krishnan
Keyword(s):  
Thermal Conductivity ◽  
High Surface ◽  
Volume Ratio ◽  
Metallic Films ◽  
Top Down ◽  
Drug Delivery Vehicles ◽  
Energy Applications ◽  
Potential Applications ◽  
Current Scenario ◽  
Delivery Vehicles

Nanoporous metallic films are known to have high surface to volume ratio due to the presence of pores. The presence of pores and ligaments make them suitable for various critical applications like sensing, catalysis, electrodes for energy applications etc. Additionally, they also combine properties of metals like good electrical and thermal conductivity and ductility. They can be fabricated using top-down or bottom-up approaches also known as dealloying and templating which give the fabricator room to tailor properties according to need. In addition, they could find potential applications in many relevant fields in current scenario like drug delivery vehicles. However, there is a long way to go to extract its whole potential.

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