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6 Make into community wiki; [made Community Wiki]

When introducing dual spaces for the first time, most linear algebra textbooks proceed in what seems to me a rather backwards fashion: the annihilator $\{f\in V^*: f(u)=0\quad \forall u\in U\}$ of a subset/space $U$ of a vector space $V$ is introduced before the dual concept of the "joint kernel"(?) $\{v\in V: f(v)=0\quad \forall f\in W\}$ of a subset/space $W$ of the dual space $V^*$. The latter notion, despite corresponding to the intuitive idea of the solution space of a homogeneous linear system of equations, is then introduced indirectly by mapping $V$ into $V^{**}$ and considering the annihilator of the system of equations $W$ of $V^*$, which is $\{\phi\in V^{**}: \phi(f)=0\quad \forall f\in W\}$. This seems a pity as many students find the isomorphism of a finite dimensional vector space with its double dual difficult to grasp!

Worse, as the "(?)" above suggests, there appears to be no common terminology or notation for the concept dual to annihilator. Possibilities include "(joint) kernel, null/zero space, pre-annihilator, solution space". I'd be grateful for any pointers to textbooks which introduce the concept directly, or any suggestions for terminology and notation.

Update: Many thanks for the suggestions so far. I am still rather surprised and disappointed by the lack of references to elementary linear algebra text books which discuss solution spaces (aka null spaces, joint kernels) before or on the same footing as annihilators. I am unconvinced by the arguments that have so far been made for this omission.

Instead it seems to me that the current situation is the result of inertia. The "annihilator" is a term that caught on, and has been carried forward in the absence of a cool name for the dual concept. In this respect I like the invention of the "vanquished".

The question is not moot as I am currently lecturing this material. I am going to stick to "solution/null space" and "joint kernel". I will then discuss duality and row rank = column rank without ever mentioning the double dual (the double dual will come later in the course).

In preparing this, I noticed the fact that solution spaces and annihilators provide a Galois connection between the posets of subsets/subspaces of a vector space and its dual (that is, solution spaces and annihilators are contravariant adjoint functors between these posets). I've seen discussion of this in the context of annihilators in ring theory, but it seems to me to be at the heart of the concept of duality for vector spaces. I hope this rings some bells among MO readers.

Such categorical thinking leads to a fairly clean analysis of solution spaces and annihilators, which I will lecture this week. After that, I'll make this question into a community wikihas in turn simplified some results subsequently.

5 Reword and update, mentioning link with Galois connections

Update: Many thanks for the suggestions so far. I am still rather shocked surprised and disappointed by the lack of references to elementary linear algebra text books which discuss solution spaces (aka null spaces, joint kernels) before or on the same footing as annihilators. I don't accept am unconvinced by the arguments that have so far been made for this prejudiceomission.

Instead it seems to me that the current situation is the result of inertia. The "annihilator" is a term that caught on, and has been followed slavishly carried forward in the absence of a cool name for the dual concept. In this respect I like the invention of the "vanquished".

The question is not moot as I am currently lecturing this material. I am going to stick to "solution/null space" and "joint kernel" for now, unless further suggestions are made very soon!kernel". I will then discuss duality and row rank = column rank without ever mentioning the double dual (don't worry, the double dual will come later in the course).

In preparing this, I discovered noticed the fact that solution spaces and annihilators provide a Galois connection between the posets of subsets/subspaces of a vector space and its dual (that is, solution spaces and annihilators are contravariant adjoint functors (with between these posets). I've seen discussion of this in the unit and counit being isomorphisms context of annihilators in ring theory, but it seems to me to be at the finite dimensional case)heart of the concept of duality for vector spaces. I will not say hope this rings some bells among MO readers.

Such categorical thinking leads to my class, a fairly clean analysis of coursesolution spaces and annihilators, but I strongly believe that 20-21st century mathematics should inform our teaching of 19-20th century mathematics.which I will lecture this material in the next week. Wish me luckAfter that, I'll make this question into a community wiki.

4 Question now urgent as I will teach the material this week!

Update: Many thanks for the suggestions so far. I am still rather shocked and disappointed by the lack of references to elementary linear algebra text books which discuss solution spaces (aka null spaces, joint kernels) before or on the same footing as annihilators. I don't accept the arguments that have so far been made for this prejudice.

Instead it seems to me that the current situation is the result of inertia. The "annihilator" is a term that caught on, and has been followed slavishly in the absence of a cool name for the dual concept. In this respect I like the invention of the "vanquished".

The question is not moot as I am currently lecturing this material. I am going to stick to "solution/null space" and "joint kernel" for now, unless further suggestions are made very soon!

I will then discuss duality and row rank = column rank without ever mentioning the doubledual (don't worry, the double dual will come later in the course). In preparing this, I discovered that solution spaces and annihilators are contravariant adjoint functors (with the unit and counit being isomorphisms in the finite dimensional case). I will not say this to my class, of course, but I strongly believe that 20-21st century mathematics should inform our teaching of 19-20th century mathematics.

I will lecture this material in the next week. Wish me luck.

3 Clarify further the distinction between the annihilator of W and the joint kernel of W
2 Added precise definitions in response to comment
1