Nonsingular Bilinear Maps Research Articles

On nonsingular bilinear maps over different fields

The investigation of nonsingular bilinear forms originates from the classification of division algebras over the real number field. Building upon this foundation, researchers have delved into the study of nonsingular bilinear forms over real number fields, leading to significant results such as Hopfs theorem. However, the interest in understanding nonsingular bilinear forms extends beyond real number fields, prompting a desire to explore other fields as well. When it comes to algebraically closed fields, the theorem becomes well-understood, with essence captured by the Hopf-Smith theorem. Inspired by these established studies, we are motivated to further the comprehension of nonsingular bilinear forms over arbitrary fields. Given a field , we study in this article numerical constraints on for the existence of nonsingular bilinear maps for not only algebraically closed fields and the real number field but also the rational number field and finite fields. We reach the final conclusion mainly through algebro-geometric techniques and the use of determinantal varieties. We reprove a result of HopfSmith which states that the minimal possible value of is when is an algebraically closed field. When is the real number field, we prove that under a combinatorial condition, the minimal possible value of is still . We also show that when is the rational number field or a finite field, the minimal possible value of is .

On inscribed trapezoids and affinely 3-regular maps

We show that any embedding $\mathbb {R}^d \to \mathbb {R}^{2d+2^{\gamma (d)}-1}$ inscribes a trapezoid or maps three points to a line, where $2^{\gamma (d)}$ is the smallest power of $2$ satisfying $2^{\gamma (d)} \geq \rho (d)$ , and $\rho (d)$ denotes the Hurwitz–Radon function. The proof is elementary and includes a novel application of nonsingular bilinear maps. As an application, we recover recent results on the nonexistence of affinely $3$ -regular maps, for infinitely many dimensions $d$ , without resorting to sophisticated algebraic techniques.

Typical ranks for 3-tensors, nonsingular bilinear maps and determinantal ideals

Let m,n≥3, (m−1)(n−1)+2≤p≤mn, and u=mn−p. The set Ru×n×m of all real tensors with size u×n×m is one to one corresponding to the set of bilinear maps Rm×Rn→Ru. We show that Rm×n×p has plural typical ranks p and p+1 if and only if there exists a nonsingular bilinear map Rm×Rn→Ru. We show that there is a dense open subset O of Ru×n×m such that for any Y∈O, the ideal of maximal minors of a matrix defined by Y in a certain way is a prime ideal and the real radical of that is the irrelevant maximal ideal if that is not a real prime ideal. Further, we show that there is a dense open subset T of Rn×p×m and continuous surjective open maps ν:O→Ru×p and σ:T→Ru×p, where Ru×p is the set of u×p matrices with entries in R, such that if ν(Y)=σ(T), then rankT=p if and only if the ideal of maximal minors of the matrix defined by Y is a real prime ideal.

Division, Adjoints, and Dualities of Bilinear Maps

The distributive property can be studied through bilinear maps and various morphisms between these maps. The adjoint-morphisms between bilinear maps establish a complete abelian category with projectives and admits a duality. Thus the adjoint category is not a module category but nevertheless it is suitably familiar. The universal properties have geometric perspectives. For example, products are orthogonal sums. The nonsingular bilinear maps are the simple bimaps with respect to nondegenerate adjoint-morphisms. That formalizes the understanding that the atoms of linear geometries are algebraic objects with no zero-divisors. Adjoint-isomorphism coincides with principal isotopism; hence, semifields can be studied within this framework.

Bases of spaces of matrices satisfying rank conditions

Motivated by the problem concerning the existence of non-singular bilinear maps, vector spaces of matrices consisting of matrices with rank bounded below are investigated. It is shown that bases for such spaces of maximum dimension can be chosen in such a way to consist of matrices of the minimal rank. An estimate of the ranks of matrices in particular types of bases for maximal such spaces is also given. This extends previously known results which were valid only in the case of spaces consisting of matrices of rank not equal to one.

Totally skew embeddings of manifolds

We study a version of Whitney’s embedding problem in projective geometry: What is the smallest dimension of an affine space that can contain an n-dimensional submanifold without any pairs of parallel or intersecting tangent lines at distinct points? This problem is related to the generalized vector field problem, existence of non-singular bilinear maps, and the immersion problem for real projective spaces. We use these connections and other methods to obtain several specific and general bounds for the desired dimension.

A remark on constructions of certain normed and nonsingular bilinear maps

A remark on constructions of certain normed and nonsingular bilinear maps

Consequences of the kahn–priddy theorem in homotopy and geometry

Much recent attention has been given to geometric representation of elements of the stable homotopy groups of spheres, π* s A particular example concerns non-singular bilinear maps ℝ m +1 × ℝ n +1 → ℝ m+n +1− p ; on restriction and normalisation these become biskew maps S m × S n ℝ S m+n-p ;. Now the Hopf construction ℋ applied to any map f: S m × S n → S m+n-p yields

Non-singular bilinear maps which come from some positively filtered rings

Non-singular bilinear maps which come from some positively filtered rings

Non-singular bilinear maps and stable homotopy classes of spheres

A bilinear map ø Ra x Rb → Rc is non-singular if ø (x, y) = 0 implies x = 0 or y = 0. For background information on such maps see (4, 5, 6, 14). If we apply the ‘Hopf construction’ to ø, we get a mapdefined by 2ø(x, y)) for all x ∈ Ra, y ∈ Rb satisfying ∥x∥2 + ∥y∥2 = 1. Homotopically, Jø coincides with the map obtained by first restricting and normalizing ø to , and then applying the standard Hopf construction ((13), p. 112). In any case, one gets an element [Jø] in , which in turn determines a stable homotopy class of spheres {Jø} in the d-stem , where d = a + b − c −1. An element in which equals {Jø} for some non-singular bilinear map ø will be called bilinearly representable. The first purpose of this paper is to prove

Some interesting examples of nonsingular bilinear maps

Some interesting examples of nonsingular bilinear maps

Construction of nonsingular bilinear maps

Construction of nonsingular bilinear maps

Immersing Projective Spaces

THEOREM 2. (a) HPn immerses in R8 n-Ea(n)-3J. (b) For n even, CPn immerses in R4ln-a(n)-1]. (c) For n odd, CPn immerses in R4n-a(n). Here a(n) is the number of ones in the dyadic expansion of n, and k(n) is a non-negative function depending only on the mod (8) residue class of n with k(1) = 0, k(3) = k(5) = 1 and k(7) = 4. As a consequence, for every j>O there is some n so that RPn immerses in R2f-. From the techniques used to prove these theorems, we also obtain some results on the existence of non-singular bilinear maps.