arXiv subjects

Samuel Wainer

Publications and source records attributed to Samuel Wainer.

3 recordsLinked to original sources

arXiv2026

Weitzenb\"{o}ck Remainder Spectrum on Rational Homogeneous Varieties

In this paper, we precisely describe the spectrum of closed invariant $(1,1)$-forms viewed as an operator acting on complex spinor bundles over rational homogeneous varieties. Using this result, we describe the spectrum of the Weitzenb\"{o}ck remainder of ${\rm{Spin}}^{c}$ Dirac operators on rational homogeneous varieties. In particular, we present an explicit formula for their smallest eigenvalue. As a byproduct, we obtain a new lower bound for the eigenvalues of the ${\rm{Spin}}^{c}$ Dirac operator, expressed in terms of Lie-theoretic data. Additionally, combining the Atiyah-Singer index theorem with the Borel-Weil-Bott theorem, we provide a complete classification of ${\rm{Spin}}^{c}$ structures on rational homogeneous varieties which admit harmonic spinors. In this last setting, we present an explicit formula for the index of the associated ${\rm{Spin}}^{c}$ Dirac operator in terms of Lie theory.

math.DG↗

arXiv2019

Immersion in Rn by Complex irreducible Spinors

The first time that the connection between isometric immersion of surfaces and solutions of the Dirac equation appeared in the literature was in the seminal paper of Thomas Friedrich in 1998. In consequence of that, several authors contributed to this topic hereafter, by obtaining the spinorial representation of Spin manifolds with arbitrary dimension and also by presenting a generalization of the Weierstrass representation map, for example. All these results assume that the manifolds and bundles involved carry a Spin structure, however this hypothesis is somehow restrictive, as for instance, if we consider complex manifolds, it is more natural to consider SpinC structures. There exist an alternative to adapt this result to SpinC manifolds, where the idea is to use the left regular representation of a Clifford algebra in itself to build the spinor bundles, but unlike the original works of Friedrich and Morel, this representation is not irreducible. Thus, this paper aims to present the spinorial representation of SpinC manifolds into Euclidian space with arbitrary dimensions using spinors that came from an irreducible representation of a complex Clifford algebra.

math.DG↗

arXiv2014

A Clifford Bundle Approach to the Differential Geometry of Branes

The Clifford bundle formalism (CBF) of differential forms and the theory of extensors acting on $\mathcal{C\ell}(M,g)$ is first used for a fomulation of the intrinsic geometry of a differential manifold $M$ equipped with a metric field $\boldsymbol{g}$ of signature $(p,q)$ and an arbitrary metric compatible connection $\nabla$ introducing the torsion (2-1)-extensor field $τ$, the curvature $(2-2)$ extensor field $\mathfrak{R}$ and (once fixing a gauge) the connection $(1-2)$-extensor $ω$ and the Ricci operator $\boldsymbol{\partial}\wedge\boldsymbol{\partial}$ (where $\boldsymbol{\partial}$ is the Dirac operator acting on sections of $\mathcal{C\ell}(M,g)$) which plays an important role in this paper. Next, using the CBF we give a thoughtful presentation the Riemann or the Lorentzian geometry of an orientable submanifold $M$ ($\dim M=m$) living in a manifold $\mathring{M}$ (such that $\mathring{M}\simeq\mathbb{R}^{n}$ is equipped with a semi-Riemannian metric $\boldsymbol{\mathring{g}}$ with signature $(\mathring{p},\mathring{q})$ and \ $\mathring{p}+\mathring{q}=n$ and its Levi-Civita connection $\mathring{D}$) and where there is defined a metric $\boldsymbol{g=i}^{\ast}\mathring{g}$, where $\boldsymbol{i}:$ $M\rightarrow \mathring{M}$ is the inclusion map. We prove several equivalent forms for the curvature operator $\mathfrak{R}$ of $M$. It is shown that the Ricci operator of $M$ is the (negative) square of the shape operator $\mathbf{S}$ of $M$. Also we disclose the relationship between the connection (1-2%)-extensor $ω$ and the shape biform $\mathcal{S}$ (an object related to $\mathbf{S}$). We hope that our presentation will be useful for differential geometers and theoretical physists interested, e.g, in string and brane theories and relativity theory.

math-ph↗