Spinors from pure spinors

Fuente: arXiv
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Main Authors: Bhoja, Niren, Krasnov, Kirill
Format: Preprint
Published: 2023
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author Bhoja, Niren
Krasnov, Kirill
author_facet Bhoja, Niren
Krasnov, Kirill
contents We propose and develop a new method to classify orbits of the spin group ${\rm Spin}(2d)$ in the space of its semi-spinors. The idea is to consider spinors as being built as a linear combination of their pure constituents, imposing the constraint that no pair of pure spinor constituents sums up to a pure spinor. We show that this leads to a simple combinatorial problem that has a finite number of solutions in dimensions up to and including fourteen. We call each distinct solution a combinatorial type of an impure spinor. We represent each combinatorial type graphically by a simplex, with vertices corresponding to the pure constituents of a spinor, and edges being labelled by the dimension of the totally null space that is the intersection of the annihilator subspaces of the pure spinors living at the vertices. We call the number of vertices in a simplex the impurity of an impure spinor. In dimensions eight and ten the maximal impurity is two. Dimension twelve is the first dimension where one gets an impurity three spinor, represented by a triangle. In dimension fourteen the generic orbit has impurity four, while the maximal impurity is five. We show that each of our combinatorial types uniquely corresponds to one of the known spinor orbits, thus reproducing the classification of spinors in dimensions up to and including fourteen from simple combinatorics. Our methods continue to work in dimensions sixteen and higher, but the number of the possible distinct combinatorial types grows rather rapidly with the dimension.
format Preprint
id arxiv_https___arxiv_org_abs_2312_13690
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Spinors from pure spinors
Bhoja, Niren
Krasnov, Kirill
Combinatorics
High Energy Physics - Theory
Differential Geometry
Representation Theory
We propose and develop a new method to classify orbits of the spin group ${\rm Spin}(2d)$ in the space of its semi-spinors. The idea is to consider spinors as being built as a linear combination of their pure constituents, imposing the constraint that no pair of pure spinor constituents sums up to a pure spinor. We show that this leads to a simple combinatorial problem that has a finite number of solutions in dimensions up to and including fourteen. We call each distinct solution a combinatorial type of an impure spinor. We represent each combinatorial type graphically by a simplex, with vertices corresponding to the pure constituents of a spinor, and edges being labelled by the dimension of the totally null space that is the intersection of the annihilator subspaces of the pure spinors living at the vertices. We call the number of vertices in a simplex the impurity of an impure spinor. In dimensions eight and ten the maximal impurity is two. Dimension twelve is the first dimension where one gets an impurity three spinor, represented by a triangle. In dimension fourteen the generic orbit has impurity four, while the maximal impurity is five. We show that each of our combinatorial types uniquely corresponds to one of the known spinor orbits, thus reproducing the classification of spinors in dimensions up to and including fourteen from simple combinatorics. Our methods continue to work in dimensions sixteen and higher, but the number of the possible distinct combinatorial types grows rather rapidly with the dimension.
title Spinors from pure spinors
topic Combinatorics
High Energy Physics - Theory
Differential Geometry
Representation Theory
url https://arxiv.org/abs/2312.13690