In mathematics and physics, Penrose graphical notation or tensor diagram notation is a (usually handwritten) visual depiction of multilinear functions or tensors proposed by Roger Penrose in 1971. A diagram in the notation consists of several shapes linked together by lines.
The notation widely appears in modern quantum theory, particularly in matrix product states and quantum circuits. In particular, Categorical quantum mechanics which includes ZX-calculus is a fully comprehensive reformulation of quantum theory in terms of Penrose diagrams, and is now widely used in quantum industry.
The notation has been studied extensively by Predrag Cvitanović, who used it, along with Feynman's diagrams and other related notations in developing "birdtracks", a group-theoretical diagram to classify the classical Lie groups. Penrose's notation has also been generalized using representation theory to spin networks in physics, and with the presence of matrix groups to trace diagrams in linear algebra.
In the language of multilinear algebra, each shape represents a multilinear function. The lines attached to shapes represent the inputs or outputs of a function, and attaching shapes together in some way is essentially the composition of functions.
In the language of tensor algebra, a particular tensor is associated with a particular shape with many lines projecting upwards and downwards, corresponding to abstract upper and lower indices of tensors respectively. Connecting lines between two shapes corresponds to contraction of indices. One advantage of this notation is that one does not have to invent new letters for new indices. This notation is also explicitly basis-independent.
Each shape represents a matrix, and tensor multiplication is done horizontally, and matrix multiplication is done vertically.
The metric tensor is represented by a U-shaped loop or an upside-down U-shaped loop, depending on the type of tensor that is used.
The Levi-Civita antisymmetric tensor is represented by a thick horizontal bar with sticks pointing downwards or upwards, depending on the type of tensor that is used.
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In mathematics, Ricci calculus constitutes the rules of index notation and manipulation for tensors and tensor fields on a differentiable manifold, with or without a metric tensor or connection. It is also the modern name for what used to be called the absolute differential calculus (the foundation of tensor calculus), developed by Gregorio Ricci-Curbastro in 1887–1896, and subsequently popularized in a paper written with his pupil Tullio Levi-Civita in 1900.
La notation en indice abstrait est un système de notation présentant des similarités avec la convention de sommation d'Einstein et destinée comme cette dernière à l'écriture du calcul tensoriel. Cette notation, due au mathématicien Roger Penrose, a pour but l'écriture pratique d'équations dans lesquelles interviennent des tenseurs ou des champs tensoriels. Il s'agit à la fois : de bénéficier de la simplicité d'écriture permise par la convention de sommation d'Einstein ; de ne pas dépendre contrairement à la convention d'Einstein d'un choix de base particulier (et donc arbitraire).
En mathématiques et physique théorique, un tenseur est antisymétrique pour les indices i et j si son signe est interchangé lorsqu'on inverse 2 indices : Un tenseur antisymétrique est un tenseur possédant 2 indices pour lesquels il est antisymétrique. Si un tenseur change de signe dès que 2 indices quelconques sont inversés, alors ce tenseur est dit complètement antisymétrique et est aussi nommé forme différentielle. Un tenseur A qui est antisymétrique pour les indices i et j possède la propriété que sa contraction avec un tenseur B, symétrique pour les indices i et j, est identiquement nulle.
Let A be a nonnegatively graded connected algebra over a noncommutative separable k-algebra K, and let M be a bounded below graded right A-module. If we denote by T the -coalgebra , we know that there exists an -comodule structure on over T. The structure ...
2019
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Humans exhibit outstanding learning, planning and adaptation capabilities while performing different types of industrial tasks. Given some knowledge about the task requirements, humans are able to plan their limbs motion in anticipation of the execution of ...
In this article we prove that the Tamarkin–Tsygan calculus of an Adams connected augmented dg algebra and of its Koszul dual are dual to each other. This uses the fact that the Hochschild cohomology and homology may be regarded as a twisted convolution dg ...