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geometric_algebra [2020/04/23 03:47]
pbk [Articles]
geometric_algebra [2020/04/23 04:09]
pbk [Articles]
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 Recently suggested scheme of quantum computing uses g-qubit states as circular polarizations from the solution of Maxwell equations in terms of geometric algebra, along with clear definition of a complex plane as bivector in three dimensions. Here all the details of receiving the solution, and its polarization transformations are analyzed. The results can particularly be applied to the problems of quantum computing and quantum cryptography. The suggested formalism replaces conventional quantum mechanics states as objects constructed in complex vector Hilbert space framework by geometrically feasible framework of multivectors. Recently suggested scheme of quantum computing uses g-qubit states as circular polarizations from the solution of Maxwell equations in terms of geometric algebra, along with clear definition of a complex plane as bivector in three dimensions. Here all the details of receiving the solution, and its polarization transformations are analyzed. The results can particularly be applied to the problems of quantum computing and quantum cryptography. The suggested formalism replaces conventional quantum mechanics states as objects constructed in complex vector Hilbert space framework by geometrically feasible framework of multivectors.
  
-  * [[https://​arxiv.org/​ftp/​arxiv/​papers/​1807/1807.08603.pdf|State/​observable interactions using basic geometric algebra solutions of the Maxwell equation]] (2018) - //Alexander Soiguine//+  * [[https://​arxiv.org/​pdf/​1807.08603|State/​observable interactions using basic geometric algebra solutions of the Maxwell equation]] (2018) - //Alexander Soiguine//
 Maxwell equation in geometric algebra formalism with equally weighted basic solutions is subjected to continuously acting Clifford translation. The received states, operators acting on observables,​ are analyzed with different values of the Clifford translation time factor and through the observable measurement results. Maxwell equation in geometric algebra formalism with equally weighted basic solutions is subjected to continuously acting Clifford translation. The received states, operators acting on observables,​ are analyzed with different values of the Clifford translation time factor and through the observable measurement results.
  
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   * [[https://​pastel.archives-ouvertes.fr/​tel-02085820/​document|Algorithmic structure for geometric algebra operators and application to quadric surfaces]] (2018) - //Stephane Breuils//   * [[https://​pastel.archives-ouvertes.fr/​tel-02085820/​document|Algorithmic structure for geometric algebra operators and application to quadric surfaces]] (2018) - //Stephane Breuils//
 Geometric Algebra is considered as a very intuitive tool to deal with geometric problems and it appears to be increasingly efficient and useful to deal with computer graphics problems. The Conformal Geometric Algebra includes circles, spheres, planes and lines as algebraic objects, and intersections between these objects are also algebraic objects. More complex objects such as conics, quadric surfaces can also be expressed and be manipulated using an extension of the conformal Geometric Algebra. However due to the high dimension of their representations in Geometric Algebra, implementations of Geometric Algebra that are currently available do not allow efficient realizations of these objects. In this thesis, we first present a Geometric Algebra implementation dedicated for both low and high dimensions. Geometric Algebra is considered as a very intuitive tool to deal with geometric problems and it appears to be increasingly efficient and useful to deal with computer graphics problems. The Conformal Geometric Algebra includes circles, spheres, planes and lines as algebraic objects, and intersections between these objects are also algebraic objects. More complex objects such as conics, quadric surfaces can also be expressed and be manipulated using an extension of the conformal Geometric Algebra. However due to the high dimension of their representations in Geometric Algebra, implementations of Geometric Algebra that are currently available do not allow efficient realizations of these objects. In this thesis, we first present a Geometric Algebra implementation dedicated for both low and high dimensions.
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 +  * [[https://​arxiv.org/​pdf/​1809.09706|Notes on Plucker'​s relations in Geometric Algebra]] (2018) - //Garret Sobczyk//
 +Grassmannians are of fundamental importance in projective geometry, algebraic geometry, and representation theory. A vast literature has grown up utilizing using many different languages of higher mathematics,​ such as multilinear and tensor algebra, matroid theory, and Lie groups and Lie algebras. Here we explore the basic idea of the Plucker relations in Clifford'​s geometric algebra. We discover that the Plucker Relations can be fully characterized in terms of the geometric product. ​
  
   * [[https://​arxiv.org/​pdf/​1908.08110.pdf|On the Clifford Algebraic Description of the Geometry of a 3D Euclidean Space]] (2019) - //Jaime Vaz, Stephen Mann//   * [[https://​arxiv.org/​pdf/​1908.08110.pdf|On the Clifford Algebraic Description of the Geometry of a 3D Euclidean Space]] (2019) - //Jaime Vaz, Stephen Mann//
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 In this paper, we address the stability of a broad class of discrete-time hypercomplex-valued Hopfield-type neural networks. To ensure the neural networks belonging to this class always settle down at a stationary state, we introduce novel hypercomplex number systems referred to as real-part associative hypercomplex number systems. Real-part associative hypercomplex number systems generalize the well-known Cayley-Dickson algebras and real Clifford algebras and include the systems of real numbers, complex numbers, dual numbers, hyperbolic numbers, quaternions,​ tessarines, and octonions as particular instances. Apart from the novel hypercomplex number systems, we introduce a family of hypercomplex-valued activation functions called B-projection functions. Broadly speaking, a B-projection function projects the activation potential onto the set of all possible states of a hypercomplex-valued neuron. Using the theory presented in this paper, we confirm the stability analysis of several discrete-time hypercomplex-valued Hopfield-type neural networks from the literature. Moreover, we introduce and provide the stability analysis of a general class of Hopfield-type neural networks on Cayley-Dickson algebras. In this paper, we address the stability of a broad class of discrete-time hypercomplex-valued Hopfield-type neural networks. To ensure the neural networks belonging to this class always settle down at a stationary state, we introduce novel hypercomplex number systems referred to as real-part associative hypercomplex number systems. Real-part associative hypercomplex number systems generalize the well-known Cayley-Dickson algebras and real Clifford algebras and include the systems of real numbers, complex numbers, dual numbers, hyperbolic numbers, quaternions,​ tessarines, and octonions as particular instances. Apart from the novel hypercomplex number systems, we introduce a family of hypercomplex-valued activation functions called B-projection functions. Broadly speaking, a B-projection function projects the activation potential onto the set of all possible states of a hypercomplex-valued neuron. Using the theory presented in this paper, we confirm the stability analysis of several discrete-time hypercomplex-valued Hopfield-type neural networks from the literature. Moreover, we introduce and provide the stability analysis of a general class of Hopfield-type neural networks on Cayley-Dickson algebras.
  
-   * [[https://​arxiv.org/​pdf/​1901.05873.pdf|Projective geometric algebra: A new framework for doing euclidean geometry]] (2019) - //Charles G. Gunn//+  * [[https://​arxiv.org/​pdf/​1903.02444|Efficient representation and manipulation of quadratic surfaces using Geometric Algebras]] (2019) - //Stéphane Breuils, Vincent Nozick, Laurent Fuchs, Akihiro Sugimoto//​ 
 +Quadratic surfaces gain more and more attention among the Geometric Algebra community and some frameworks were proposed in order to represent, transform, and intersect these quadratic surfaces. As far as the authors know, none of these frameworks support all the operations required to completely handle these surfaces. Some frameworks do not allow the construction of quadratic surfaces from control points when others do not allow to transform these quadratic surfaces. However , if we consider all the frameworks together, then all the required operations over quadratic are covered. This paper presents a unification of these frameworks that enables to represent any quadratic surfaces either using control points or from the coefficients of its implicit form. The proposed approach also allows to transform any quadratic surfaces and to compute their intersection and to easily extract some geometric properties.  
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 +  ​* [[https://​arxiv.org/​pdf/​1901.05873.pdf|Projective geometric algebra: A new framework for doing euclidean geometry]] (2019) - //Charles G. Gunn//
 A tutorial introduction to projective geometric algebra (PGA), a modern, coordinate-free framework for doing euclidean geometry. PGA features: uniform representation of points, lines, and planes; robust, parallel-safe join and meet operations; compact, polymorphic syntax for euclidean formulas and constructions;​ a single intuitive sandwich form for isometries; native support for automatic differentiation;​ and tight integration of kinematics and rigid body mechanics. Inclusion of vector, quaternion, dual quaternion, and exterior algebras as sub-algebras simplifies the learning curve and transition path for experienced practitioners. On the practical side, it can be efficiently implemented,​ while its rich syntax enhances programming productivity. A tutorial introduction to projective geometric algebra (PGA), a modern, coordinate-free framework for doing euclidean geometry. PGA features: uniform representation of points, lines, and planes; robust, parallel-safe join and meet operations; compact, polymorphic syntax for euclidean formulas and constructions;​ a single intuitive sandwich form for isometries; native support for automatic differentiation;​ and tight integration of kinematics and rigid body mechanics. Inclusion of vector, quaternion, dual quaternion, and exterior algebras as sub-algebras simplifies the learning curve and transition path for experienced practitioners. On the practical side, it can be efficiently implemented,​ while its rich syntax enhances programming productivity.
  
-  * [[https://​arxiv.org/​pdf/​1912.05960|Geometric ​Algebra, Gravity and Gravitational Waves]] (2019) - //Anthony N. Lasenby// +  * [[https://​arxiv.org/​pdf/​1909.02408|A Low-Memory Time-Efficient Implementation of Outermorphisms for Higher-Dimensional ​Geometric ​Algebras]] (2019) - //Ahmad Hosny Eid// 
-We discuss an approach to gravitational waves based on Geometric Algebra and Gauge Theory Gravity. After a brief introduction to Geometric Algebra ​(GA), we consider Gauge Theory Gravitywhich uses symmetries expressed within ​the GA of flat spacetime to derive gravitational forces as the gauge forces corresponding to making these symmetries local. We then consider solutions for black holes and plane gravitational waves in this approach, noting the simplicity ​that GA affords in both writing ​the solutions, and checking some of their properties. We then go on to show that a preferred gauge emerges for gravitational plane wavesin which a `memory effect'​ corresponding ​to non-zero velocities left after the passage ​of the waves becomes clear, ​and the physical nature of this effect is demonstrated. In a final section we present the mathematical details ​of the gravitational wave treatment in GA, and link it with other approaches ​to exact waves in the literature.+Many important mathematical formulations in GA can be expressed as outermorphisms such as versor products, linear projection operators, and mapping between related coordinate frames. (...) This work attempts to shed some light on the problem of optimizing software implementations of outermorphisms for practical prototyping applications using geometric algebra. The approach ​we propose here for implementing outermorphisms requires orders of magnitude less memory compared ​to other common approaches, while being comparable in time performance,​ especially for high-dimensional geometric algebras. 
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 +  * [[http://​downloads.hindawi.com/​journals/​cin/​2019/​9374802.pdf|Evaluating a Semi-Autonomous Brain-Computer Interface Based on Conformal ​Geometric Algebra and Artificial Vision]] ​(2019- //Mauricio Ramirez-MorenoDavid Gutiérrez//​ 
 +We evaluate a semi-autonomous brain-computer interface (BCI) for manipulation tasks. In such system, the user controls a robotic arm through motor imagery commands(...) We take a semi-autonomous ​approach ​based on a conformal geometric algebra model that solves ​the inverse kinematics ​of the robot on the flythen the user only has to decide on the start of the movement ​and the final position ​of the effector (goal-selection approach). Under these conditionswe implemented pick-and-place tasks with a disk as an item and two target areas placed on the table at arbitrary positions. 
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 +  * [[https://​arxiv.org/​pdf/​1912.11198|Geometric Obstructions on Gravity]] (2019) - //Yuri Martins, Rodney Biezuner//​ 
 +These are notes for a short course and some talks gave at Departament of Mathematics and at Departament of Physics of Federal University of Minas Gerais, based on the author'​s paper. (...) We present obstructions ​to realize gravity, modeled by the tetradic Einstein-Hilbert-Palatini (EHP) action functional, in a general geometric setting.
  
   * [[https://​vixra.org/​pdf/​1911.0127v1.pdf|Robust Quaternion Estimation with Geometric Algebra]] (2019) - //Mauricio C. Lopez//   * [[https://​vixra.org/​pdf/​1911.0127v1.pdf|Robust Quaternion Estimation with Geometric Algebra]] (2019) - //Mauricio C. Lopez//
geometric_algebra.txt · Last modified: 2020/06/20 00:46 by pbk