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PhyslibAlpha.AlgebraicFramework.Algebra.NuclearInvolution

Nuclear involutions

A star involution on an alternative algebra whose symmetric elements are nuclear (associate trivially with everything) — the coordinate-algebra interface a `*`-alternative division algebra like the octonions needs to support an exceptional Albert Jordan algebra of Hermitian matrices over it. Independent of Jordan order, norms, CFC, and JBW normality.

Key definitions and results

- `IsNuclear`, `IsNuclearInvolution` - `nuclear_slip_left`/`_mid`/`_last`/`_last_right` : a nuclear element slips through the associator. - `assoc_star_first`/`_mid`/`_last` : the associator is alternating in sign under `star`. - `nuclear_comm_associator` : a nuclear element commutes with any associator.

10 declarations

definition

Nuclearity of an element xx ([x,y,z]=[y,x,z]=[y,z,x]=0[x, y, z] = [y, x, z] = [y, z, x] = 0)

An element xx in an algebra DD is nuclear if it associates trivially in every slot. Specifically, for all y,z∈Dy, z \in D, the associator [a,b,c]=(ab)c−a(bc)[a, b, c] = (ab)c - a(bc) satisfies [x,y,z]=0[x, y, z] = 0, [y,x,z]=0[y, x, z] = 0, and [y,z,x]=0[y, z, x] = 0.

theorem

A nuclear element slips through the left of the associator: [nx,y,z]=n[x,y,z][nx, y, z] = n[x, y, z]

In an algebra DD, if n∈Dn \in D is a nuclear element—meaning that for all a,b∈Da, b \in D, the associator [a,b,c]=(ab)c−a(bc)[a, b, c] = (ab)c - a(bc) satisfies [n,a,b]=[a,n,b]=[a,b,n]=0[n, a, b] = [a, n, b] = [a, b, n] = 0—then for any elements x,y,z∈Dx, y, z \in D, the associator satisfies the identity [nx,y,z]=n[x,y,z][nx, y, z] = n[x, y, z].

theorem

[x,ny,z]=n[x,y,z][x, ny, z] = n[x, y, z] for nuclear nn

Let DD be an algebra. An element n∈Dn \in D is said to be nuclear if it associates trivially in every position, meaning that for all a,b∈Da, b \in D, the associator [x,y,z]=(xy)z−x(yz)[x, y, z] = (xy)z - x(yz) satisfies [n,a,b]=0[n, a, b] = 0, [a,n,b]=0[a, n, b] = 0, and [a,b,n]=0[a, b, n] = 0. For any such nuclear element nn and any elements x,y,z∈Dx, y, z \in D, the identity [x,ny,z]=n[x,y,z][x, ny, z] = n[x, y, z] holds.

theorem

[x,y,nz]=n[x,y,z][x, y, nz] = n[x, y, z] for nuclear nn

Let DD be an algebra. Suppose n∈Dn \in D is a nuclear element, meaning it associates trivially in every slot (i.e., [n,a,b]=[a,n,b]=[a,b,n]=0[n, a, b] = [a, n, b] = [a, b, n] = 0 for all a,b∈Da, b \in D). For any elements x,y,z∈Dx, y, z \in D, the associator satisfies the identity [x,y,nz]=n[x,y,z][x, y, n z] = n [x, y, z], where [x,y,z]=(xy)z−x(yz)[x, y, z] = (xy)z - x(yz).

theorem

[x,y,z⋅n]=[x,y,z]⋅n[x, y, z \cdot n] = [x, y, z] \cdot n for nuclear nn

Let DD be an algebra. If n∈Dn \in D is a nuclear element—meaning that for all a,b∈Da, b \in D, the associator [a,b,c]=(ab)c−a(bc)[a, b, c] = (ab)c - a(bc) satisfies [n,a,b]=[a,n,b]=[a,b,n]=0[n, a, b] = [a, n, b] = [a, b, n] = 0—then for any elements x,y,z∈Dx, y, z \in D, the associator satisfies the identity [x,y,z⋅n]=[x,y,z]⋅n[x, y, z \cdot n] = [x, y, z] \cdot n.

theorem

x+x∗x + x^* is Nuclear

Let DD be an alternative algebra equipped with a star involution denoted by x↦x∗x \mapsto x^*. For any element x∈Dx \in D, the sum x+x∗x + x^* is nuclear. An element n∈Dn \in D is defined as nuclear if it associates trivially with all elements y,z∈Dy, z \in D in the sense that the associator [a,b,c]=(ab)c−a(bc)[a, b, c] = (ab)c - a(bc) satisfies [n,y,z]=0[n, y, z] = 0, [y,n,z]=0[y, n, z] = 0, and [y,z,n]=0[y, z, n] = 0.

theorem

[x∗,y,z]=−[x,y,z][x^*, y, z] = -[x, y, z]

In an alternative algebra DD equipped with a star involution, let [x,y,z]=(xy)z−x(yz)[x, y, z] = (xy)z - x(yz) denote the associator of elements x,y,z∈Dx, y, z \in D. For any elements x,y,z∈Dx, y, z \in D, the associator of the star of xx with yy and zz is the negative of the associator of x,y,zx, y, z: [x∗,y,z]=−[x,y,z],[x^*, y, z] = -[x, y, z], where x∗x^* denotes the star involution applied to xx.

theorem

(x,y∗,z)=−(x,y,z)(x, y^*, z) = -(x, y, z)

Let DD be a ∗\ast-alternative algebra. For any elements x,y,z∈Dx, y, z \in D, the associator (x,y,z)=(xy)z−x(yz)(x, y, z) = (xy)z - x(yz) satisfies the identity (x,y∗,z)=−(x,y,z)(x, y^*, z) = -(x, y, z), where y∗y^* denotes the star involution of yy.

theorem

[x,y,z∗]=−[x,y,z][x, y, z^*] = -[x, y, z]

In an alternative algebra DD equipped with a star involution x↦x∗x \mapsto x^*, for any elements x,y,z∈Dx, y, z \in D, the associator [x,y,z]=(xy)z−x(yz)[x, y, z] = (xy)z - x(yz) satisfies the identity [x,y,z∗]=−[x,y,z][x, y, z^*] = -[x, y, z].

theorem

Nuclear Elements Commute with the Associator [x,y,z][x, y, z]

Let DD be an algebra and n∈Dn \in D be a nuclear element, meaning that for all y,z∈Dy, z \in D, the associator [a,b,c]=(ab)c−a(bc)[a, b, c] = (ab)c - a(bc) satisfies [n,y,z]=0[n, y, z] = 0, [y,n,z]=0[y, n, z] = 0, and [y,z,n]=0[y, z, n] = 0. Then for any x,y,z∈Dx, y, z \in D, the element nn commutes with the associator of x,y,zx, y, z, such that n⋅[x,y,z]=[x,y,z]⋅nn \cdot [x, y, z] = [x, y, z] \cdot n.