Spin(7) orientifolds and 2d $$ \mathcal{N} $$ = (0, 1) triality

We present a new, geometric perspective on the recently proposed triality of 2d $$ \mathcal{N} $$ N = (0, 1) gauge theories, based on its engineering in terms of D1-branes probing Spin(7) orientifolds. In this context, triality translates into the fact that multiple gauge theories correspond to the same underlying orientifold. We show how Spin(7) orientifolds based on a particular involution, which we call the universal involution, give rise to precisely the original version of $$ \mathcal{N} $$ N = (0, 1) triality. Interestingly, our work also shows that the space of possibilities is significantly richer. Indeed, general Spin(7) orientifolds extend triality to theories that can be regarded as consisting of coupled $$ \mathcal{N} $$ N = (0, 2) and (0, 1) sectors. The geometric construction of 2d gauge theories in terms of D1-branes at singularities therefore leads to extensions of triality that interpolate between the pure $$ \mathcal{N} $$ N = (0, 2) and (0, 1) cases.

Planar Compliance Realization with Two 3-Joint Serial Manipulators Connected in Parallel

In this paper, the realization of any specified planar compliance with two 3R serial elastic mechanisms is addressed. Using the concepts of dual elastic mechanisms, it is shown that the realization of a compliant behavior with 2 serial mechanisms connected in parallel is equivalent to its realization with a 6-spring fully parallel mechanism. Since the spring axes of a 6-spring parallel mechanism indicate the geometry of a dual 3R serial mechanism, a new synthesis procedure for the realization of a stiffness matrix with a 6-spring parallel mechanism is first developed. Then, this result is extended to a geometric construction-based synthesis procedure for two 3-joint serial mechanisms.

Compiler for physical and geometric construction of sets

This article is devoted to the geometric representation of sets. The paper presents an implementation that allows using operations on sets to build any images. For this algorithm, the equations of first-and second-order lines on the plane and first-and second-order surfaces in space are used. Restrictions are introduced by setting segments on the coordinate axes, indicating whether lines or surfaces belong to these segments. Inequalities are used to create the shaded area of the drawings. In the course of research on this topic, a software tool was developed that allows you to model drawings using the entered formulas, build images based on a set of operations on given sets of points, which allows you to have an analytical description of the drawings. This software tool can be used both in the educational process to test the correctness of the assimilation of the material, and to create flat geometric shapes and three-dimensional bodies for the purpose of engineering the optimal forms of structures and various parts. This application allows the user, performing operations with mathematical expressions and inequalities, to get a graphical display of the result with a mathematical description of any part of the figure.

A plane trigonometric proof for the case n = 4 of Fermat’s Last Theorem

We present a plane trigonometric proof for the case n = 4 of Fermat’s Last Theorem. We first show that every triplet of positive real numbers (a, b, c) satisfying a4 + b4 = c4 forms the sides of an acute triangle. The subsequent proof is founded upon the observation that the Pythagorean description of every such triangle expressed through the law of cosines must exactly equal the description of the triangle from the Fermat equation. On the basis of a geometric construction motivated by this observation, we derive a class of polynomials, the roots of which are the sides of these triangles. We show that the polynomials for a given triangle cannot all have rational roots. To the best of our knowledge, the approach offers new geometric and algebraic insight into the irrationality of the roots.

On the Geometric Approach to the Boundary Problem in Supergravity

We review the geometric superspace approach to the boundary problem in supergravity, retracing the geometric construction of four-dimensional supergravity Lagrangians in the presence of a non-trivial boundary of spacetime. We first focus on pure N=1 and N=2 theories with negative cosmological constant. Here, the supersymmetry invariance of the action requires the addition of topological (boundary) contributions which generalize at the supersymmetric level the Euler-Gauss-Bonnet term. Moreover, one finds that the boundary values of the super field-strengths are dynamically fixed to constant values, corresponding to the vanishing of the OSp(N|4)-covariant supercurvatures at the boundary. We then consider the case of vanishing cosmological constant where, in the presence of a non-trivial boundary, the inclusion of boundary terms involving additional fields, which behave as auxiliary fields for the bulk theory, allows to restore supersymmetry. In all the cases listed above, the full, supersymmetric Lagrangian can be recast in a MacDowell-Mansouri(-like) form. We then report on the application of the results to specific problems regarding cases where the boundary is located asymptotically, relevant for a holographic analysis.

Geometrization of Trigonometric Solutions of the Associative and Classical Yang–Baxter Equations

We describe a geometric construction of all nondegenerate trigonometric solutions of the associative and classical Yang–Baxter equations. In the associative case, the solutions come from symmetric spherical orders over the irreducible nodal curve of arithmetic genus $1$, while in the Lie case they come from spherical sheaves of Lie algebras over the same curve.

Construction with ruler and compass, van Hiele model for geometry thinking and Project-based learning

We describe how problems of geometric construction using straightedge and compass can be introduced to students through project-based learning. We discuss how these problems can be extended to the upper half-plane model. Furthermore, we discuss the use of these problems to assess advanced levels in van Hiele model for geometry thinking.

Serial Chain of Rigid Origami That Extends, Bends and Turns

This paper presents a family of serial chain mechanisms with three degrees of freedom (DOF) by concatenating rigid origami modules. This chained mechanism forms a circular arc shape and can continuously extend, bend, and turn. The mechanism keeps three-DOF regardless of the number of connected modules, and the whole motion can be controlled by determining the configuration of one module at the end. We first describe the geometric construction of the mechanism and its implementation as a rigid origami fabricated from a flat sheet. We then analyze the kinematics of the system to illustrate the configuration space and how the shapes change by manipulating the input parameters. We also synthesize the motions by numerically solving inverse kinematics of the system. We also propose novel torus mechanism with two DOF.