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2-category 2-category-theory abelian-categories adjoint algebra algebraic algebraic-geometry algebraic-topology analysis analytic-geometry arithmetic arithmetic-geometry beauty bundles calculus categorical categories category category-theory chern-weil-theory cohesion cohesive-homotopy-theory cohesive-homotopy-type-theory cohomology colimits combinatorics complex complex-geometry computable-mathematics computer-science constructive cosmology deformation-theory descent diagrams differential differential-cohomology differential-equations differential-geometry digraphs duality elliptic-cohomology enriched fibration foundation foundations functional-analysis functor galois-theory gauge-theory gebra geometric-quantization geometry graph graphs gravity grothendieck group group-theory harmonic-analysis higher higher-algebra higher-category-theory higher-differential-geometry higher-geometry higher-lie-theory higher-topos-theory homological homological-algebra homotopy homotopy-theory homotopy-type-theory index-theory integration integration-theory k-theory lie lie-theory limits linear linear-algebra locale localization logic mathematics measure-theory modal modal-logic model model-category-theory monad monads monoidal monoidal-category-theory morphism motives motivic-cohomology nlab noncommutative noncommutative-geometry number-theory of operads operator operator-algebra order-theory pages pasting philosophy physics pro-object probability probability-theory quantization quantum quantum-field quantum-field-theory quantum-mechanics quantum-physics quantum-theory question representation representation-theory riemannian-geometry scheme schemes set set-theory sheaf sheaves simplicial space spin-geometry stable-homotopy-theory string string-theory superalgebra supergeometry svg symplectic-geometry synthetic-differential-geometry terminology theory topology topos topos-theory type type-theory universal variational-calculus

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- Discussion Type
- discussion topicVojta's conjecture
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by zskoda
- Last Active Sep 20th 2012

- Discussion Type
- discussion topiclooping combinator
- Category Latest Changes
- Started by Mike Shulman
- Comments 6
- Last comment by Mike Shulman
- Last Active Sep 20th 2012

Created looping combinator.

- Discussion Type
- discussion topicinfinity-module
- Category Latest Changes
- Started by Urs
- Comments 5
- Last comment by Urs
- Last Active Sep 20th 2012

I noticed that in

the

*∞-module*was kind of missing (we had module over an algebra over an (∞,1)-operad). So I created something stubby.

- Discussion Type
- discussion topicterm
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 20th 2012

When making

*inhabitant*redirect to*term*a few minutes back I also found the entry*term*to be in an unfortunate state. I tried to improve it a bit by giving it more of an Idea section, and at least a vague indication of the formal definition.

- Discussion Type
- discussion topicsalamander lemma
- Category Latest Changes
- Started by Urs
- Comments 9
- Last comment by Urs
- Last Active Sep 20th 2012

I am starting

*salamander lemma*

- Discussion Type
- discussion topicimplication
- Category Latest Changes
- Started by Urs
- Comments 4
- Last comment by Urs
- Last Active Sep 20th 2012

at

*implication*there is currently the statement$q \to r \vdash (p \to q) \to (q \to r)$,

That’s a typo, right?

- Discussion Type
- discussion topicreal coalgebra
- Category Latest Changes
- Started by Todd_Trimble
- Comments 10
- Last comment by Todd_Trimble
- Last Active Sep 19th 2012

I hope to be adding bits and pieces to an article real coalgebra, which I’ve started. (In some sense it might fit better on my web, but for some reason I’m placing it on the main nLab.)

- Discussion Type
- discussion topicextension of scalars
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 19th 2012

I ended up spending some time with expanding

*extension of scalars*. Towards the end I had more plans, but I’ll stop now, need to do something else.

- Discussion Type
- discussion topicindex of a subgroup
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 19th 2012

created

*index of a subgroup*

- Discussion Type
- discussion topicfour lemma
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 18th 2012

created

*four lemma*(should still state the dual version, will do so later)

- Discussion Type
- discussion topicequality and equivalence - contents
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active Sep 18th 2012

and now I even ended up creating a new floating table of contents:

*equality and equivalence - contents*(all I wanted to originally was to create an elementary entry

*linear equation*…)

- Discussion Type
- discussion topicequation
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 17th 2012

I really just wanted to start an entry

*linear equation*but I ended up putting some content into*equation*.

- Discussion Type
- discussion topicLascar group and first order theories
- Category Latest Changes
- Started by Tim_Porter
- Comments 1
- Last comment by Tim_Porter
- Last Active Sep 17th 2012

I have added some links to preprint on the entry Lascar group. I do not understand the model theory, but its link with Galois theory may be of use to someone looking at model theory and type theory elsewhere on the Lab, so I hope it is useful.

- Discussion Type
- discussion topicinternal set
- Category Latest Changes
- Started by Urs
- Comments 29
- Last comment by TobyBartels
- Last Active Sep 17th 2012

I see we have

*internal set*, while I was just about to make that term redirect to*Bishop set*.That would have read more systematically in the list at

*internal infinity-categories contents*.

- Discussion Type
- discussion topicformal logic
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 15th 2012

I keep feeling the need to point to an entry named

*formal logic*. None of the existing entries seems to quite deserve to be where this link should be redirecting to. So I created a page*formal logic*with just some pointers to pages that the reader*might*expect behind this term.Just so that I can use that link for the time being.

- Discussion Type
- discussion topicDrinfeld associators
- Category Latest Changes
- Started by adrienBrochier
- Comments 4
- Last comment by adrienBrochier
- Last Active Sep 15th 2012

- I created and filled a bit a page about Drinfeld associators.

- Discussion Type
- discussion topicHamiltonian form
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 15th 2012

have split off

*Hamiltonian form*from n-plectic geometry (because I needed to be able to point to it)

- Discussion Type
- discussion topicDrinfeld-Kohno Lie algebra
- Category Latest Changes
- Started by adrienBrochier
- Comments 3
- Last comment by adrienBrochier
- Last Active Sep 14th 2012

- Expanded a bit Drinfeld-Kohno Lie algebra

- Discussion Type
- discussion topicSimple functions
- Category Latest Changes
- Started by TobyBartels
- Comments 1
- Last comment by TobyBartels
- Last Active Sep 14th 2012

I took simple function out of measure space, putting there abstract definitions up through the integral on $L^1$.

- Discussion Type
- discussion topicconnecting homomorphism
- Category Latest Changes
- Started by Urs
- Comments 4
- Last comment by Urs
- Last Active Sep 12th 2012

creatd connecting homomorphism with (just) the pedestrian description.

(Relation to snake lemma and more generally to fiber sequences not there yet…)

- Discussion Type
- discussion topicuniverse - contents
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 11th 2012

As I said in another thread, I would like to see the $n$Lab entries related to universes be somehow better, more organized, more comprehensive.

In order to get a handle on it I decided, as so often, to tabulate what we have and what we should have, so I am creating:

and will include it as a “floating table of contents” into the relevant entries

- Discussion Type
- discussion topicinductive reasoning
- Category Latest Changes
- Started by Urs
- Comments 8
- Last comment by TobyBartels
- Last Active Sep 11th 2012

at

*inductive reasoning*it saysInduction here is not to be confused with

*mathematical induction*.We should point out that, however, there is a close relation:

one can see this still in the German tem for, “induction over the natural numbers” which is not

*Induktion*, but*vollständige Induktion*: meaning ”*complete*induction” !I guess the reasoning is clear, mathematical induction (at least that over the natural numbers)

*is*a special case of inductive reasoning, namely that where we can be sure that we are inducing from a*complete*set of instances of the general rule.Does anyone feel like touching the entry accordingly to clarify this?

- Discussion Type
- discussion topicMod
- Category Latest Changes
- Started by Urs
- Comments 7
- Last comment by Urs
- Last Active Sep 11th 2012

created Mod

- Discussion Type
- discussion topicquotient module
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 11th 2012

created

*quotient module*

- Discussion Type
- discussion topicsubmodule
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 11th 2012

created

*submodule*

- Discussion Type
- discussion topicquotient group
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 11th 2012

turns out plenty of entries were asking for

*quotient group*. I created something. But am running a bit out of steam for tonight.

- Discussion Type
- discussion topiccokernel
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active Sep 11th 2012

I have touched

*cokernel*, briefly adding some basics. More needs to be done here.

- Discussion Type
- discussion topicstructure
- Category Latest Changes
- Started by Urs
- Comments 17
- Last comment by Mike Shulman
- Last Active Sep 10th 2012

After discussion here I have changed the organization of the entry

*structure*and then expanded a bit by adding an Idea-section and a bit more here and there.(The previous organization of the entry instead made it look like

*structure in model theory*is a concept on par with that discussed at*stuff, structure, property*. But instead, the latter axiomatizes the general notion of “structure on something” as such, whereas the former is an*example*of a structure on something (namely an “$L$-structure on a set”). The new version aims to reflect this properly.)

- Discussion Type
- discussion topicNew SVGs for knot pages
- Category Latest Changes
- Started by Andrew Stacey
- Comments 21
- Last comment by Andrew Stacey
- Last Active Sep 10th 2012

Using the LaTeX macro package TikZ, I’ve redrawn most of the SVGs on the knots and links pages. I hope that I haven’t trodden on any toes in so doing! I may have missed a few diagrams as well.

I’ve shifted the actual SVGs to pages of their own. This makes it easier to edit the pages with them on - TikZ’s SVG export isn’t as compact as the inbuilt SVG editor - and easier to include on other pages. For example, I can imagine that the trefoil knot is going to appear again and again!

(Incidentally, are the two trefoils distinct? If so, which have I drawn at trefoil knot - SVG).

I’ve named the pages with

`- SVG`

in their name, though for the moment I’ve also put in redirects to the name without the SVG. When actually including the diagram, one should always use the*canonical*name (ie*with*the`- SVG`

) since it may be that we actually write a page about the trefoil knot one day. But I thought that for the moment, a nice aspect of hyperlinks is that if we mention the trefoil knot in a page then we can put in a link to an actual picture.Diagrams done so far:

- trefoil knot - SVG
- trefoil knot (2 bridge) - SVG
- Hopf link - SVG
- Whitehead link - SVG
- Borromean link - SVG (also redirects from Borromean rings)
- Reidemeister move 1 - SVG (it’s amazing how many ways it is possible to misspell Reidemeister)
- Reidemeister move 2 - SVG
- Reidemeister move 3 - SVG
- figure 8 knot - SVG

Pages with includes include: link, Reidemeister move, colorability, bridge number.

What would be fantastic here is if the “source” link took one to the actual LaTeX/TikZ source! I do intend to put that up on the nLab, but I need to clean it up a little as it depends on some customised style files that have a lot of crud in them.

- Discussion Type
- discussion topicAlexander, Dehn, et al
- Category Latest Changes
- Started by Tim_Porter
- Comments 1
- Last comment by Tim_Porter
- Last Active Sep 10th 2012

I have been attacking some of the grey links in knot theory and the related pages. If someone has the time (and the patience) adding a few more links would be a good thing. I have added Crowell, Fox, Dehn, Alexander, Louis Kauffman, plus some non-people pages such as Alexander polynomial. That needs some diagrams if it is to do what it ’should’ and my svg skills are too slight to attempt that today. :-)

- Discussion Type
- discussion topicfree monoid
- Category Latest Changes
- Started by Todd_Trimble
- Comments 6
- Last comment by TobyBartels
- Last Active Sep 10th 2012

I added to the “abstract nonsense” section in free monoid a helpful general observation on how to construct free monoids. “Adjoint functor theorem” is overkill for free monoids over $Set$.

- Discussion Type
- discussion topiccontext
- Category Latest Changes
- Started by Urs
- Comments 29
- Last comment by Urs
- Last Active Sep 8th 2012

[ forwarding old discussion that used to be at context ]

The following discussion was initiated by a previous version of the above entry which referred to “cartesian multicategories” rather than finitely complete categories.

+–{: .query} Mike: What is a cartesian multicategory, and how do I interpret the theory of groups in one? I can guess what it would mean for a multicategory to have finite products. But if I interpret the multiplication as a morphism $G\times G\to G$, then I’m not using the multicategory structure, so we might as well just be in a category with finite products. And if I interpret the multiplication as a multimap $(G;G)\to G$, then I don’t know how to interpret the axiom of inverses, since there is no ’diagonal’ $G\to (G;G)$ or ’projection’ $G\to ()$.

*Toby*: I'm not sure why I generalised to cartesian multicategories, but it is a nontrivial generalisation. (Perhaps I was planning to show, as an example, how the category of contexts of the canonical language of a multicategory becomes a monoidal category or something, but that doesn't seem very useful. Maybe I was just doing unnecessary generality, but of course it's not the absolutely most general situation either.)Anyway … you make a multicategory cartesian much as you might make a monoidal category cartesian by equipping it with appropriate diagonal and projection maps. The problem is that, while $G \to G \otimes G$ and $G \to 1$ make sense in a monoidal category, they don't make sense in a multicategory. But you fix this by filtering through Yoneda.

So a

**cartesian multicategory**is a multicategory equipped with, for each object $G$ and object $X$, a function $\check{G}^*_X\colon hom(G;X) \leftarrow hom(G,G;X)$ and a function $\hat{G}^*_X\colon hom(G;X) \leftarrow hom(;X)$. (H'm, my commas and semicolons are the opposite of yours; no matter.) Then these are subject to various coherence requirements that should be obvious.Mike: Okay, I see. Though I’m guessing you wanted those natural transformations to go the other way. Are there any naturally occurring examples of cartesian multicategories that are not cartesian monoidal categories? Even if there are, I’m inclined to regard the concept as esoteric enough that it would be clearer to just say “category with finite products” in this introductory article.

*Toby*: Ah, the curse of contravariance! Going over the whole introduction again, I think that I understand why I mentioned multicategories, which is that a context like $a\colon G, b\colon G$ is more naturally interpreted as a list $(G, G)$ of objects than as a single object $G \times G$. But if we were really to go in that direction, then we'd also want the context $a\colon G, b\colon G, (a b)^2 = a^2 b^2$ to be interpreted as a list in its own right rather than an actual subobject of $G \times G$, and that's going a bit far … farther than I understand clearly, in any case. So in fact I let the category be finitely complete so that we could form that subobject (referred to only via the link to internal logic, of course).Mike: True. Is a one-object cartesian multicategory the same as a Lawvere theory, aka an operad relative to the theory of categories with finite products? If so, then perhaps the relevant place to work is a multicategory relative to the theory of lex categories? Can that be generalized to stronger logics?

*Toby*: Yes, that seems to be right, that Lawvere theories are equivalent to one-object cartesian multicategories (cartesian multimonoids? cartesian operads?). So this should work.Of course, one thing that contexts do is to form an honest category even if you start with a multicategory. So here we're trying to go backwards and see what bare-bones starting point could lead to the same category of contexts of the equational theory of a group. =–

- Discussion Type
- discussion topicphysics
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 8th 2012

I finally gave the poor entry

*physics*a bit of text.

- Discussion Type
- discussion topicinternal sheaf
- Category Latest Changes
- Started by Urs
- Comments 9
- Last comment by Urs
- Last Active Sep 8th 2012

created

*internal sheaf*Mainly it was bugging me that I didn’t find a piece of literature that said it quite explicitly the way I do there, so I wanted to have that written down. To be expanded, eventually.

- Discussion Type
- discussion topiclogic and inductive inference
- Category Latest Changes
- Started by David_Corfield
- Comments 32
- Last comment by TobyBartels
- Last Active Sep 8th 2012

Made some changes at logic and started inductive inference and George Polya.

There are still things to change at logic

As a discipline, logic is the study of methods of reasoning. While in the past (and often today in philosophical circles), this discipline was prescriptive (describing how one should reason), it is increasingly (and usually in mathematical circles) descriptive (describing how one does reason).

Could whoever wrote it explain what they meant? Seems odd to me.

Also I don’t think that category-theoretic logic should be there. Should it not appear in mathematical logic, or be a new page?

- Discussion Type
- discussion topic*-countable spaces
- Category Latest Changes
- Started by TobyBartels
- Comments 1
- Last comment by TobyBartels
- Last Active Sep 8th 2012

Expanded second-countable space and started first-countable space.

- Discussion Type
- discussion topicarity class
- Category Latest Changes
- Started by Mike Shulman
- Comments 8
- Last comment by Todd_Trimble
- Last Active Sep 7th 2012

Created arity class. Added links from a few places, but there are probably others I didn’t think of.

- Discussion Type
- discussion topicJohn Power
- Category Latest Changes
- Started by Tim_Porter
- Comments 1
- Last comment by Tim_Porter
- Last Active Sep 7th 2012

I fixed a strange link at John Power.

- Discussion Type
- discussion topicfoundational axiom
- Category Latest Changes
- Started by Urs
- Comments 56
- Last comment by Mike Shulman
- Last Active Sep 6th 2012

To Toby, mainly, of course also to anyone interested:

We have a page-“category”

*foundational axiom*, but we have no entry of that name. We should start one!*foundational axiom*.(We do have

*axiom of foundation*. A bit of a different thing.)

- Discussion Type
- discussion topicsecond order arithmetic
- Category Latest Changes
- Started by Todd_Trimble
- Comments 4
- Last comment by TobyBartels
- Last Active Sep 6th 2012

I’ve been editing second order arithmetic (I usually write “second-order arithmetic”, with a hyphen). I would appreciate someone taking a look and making corrections if necessary. There are probably some hyperlinks which could be added.

- Discussion Type
- discussion topicκ-ary site
- Category Latest Changes
- Started by Mike Shulman
- Comments 1
- Last comment by Mike Shulman
- Last Active Sep 6th 2012

Created κ-ary site.

- Discussion Type
- discussion topick-ary exact category
- Category Latest Changes
- Started by Mike Shulman
- Comments 2
- Last comment by Urs
- Last Active Sep 5th 2012

I renamed familial regularity and exactness to k-ary exact category (with redirects from k-ary regular category), and updated some of the statements to match my exact completions paper a bit better.

I’m planning to create k-ary site as well, and add a statement of the main theorem of the paper somewhere on the nLab. But I’m undecided as to where that statement should go and how it should interact with the existing pages regular and exact completions and pretopos completion. Opinions are welcome.

- Discussion Type
- discussion topicChan-Paton bundle
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 5th 2012

expanded at

*Chan-Paton bundle*the Idea-section and added two pointers to lecture notes. Also expanded at*Freed-Witten anomaly*a little.

- Discussion Type
- discussion topictype theory - contents
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 4th 2012

I ended up polishing

*type theory - contents*(which is included as a floating table of contents in the relevant entries):expanded and re-arranged the list under “syntax”, created stubs for the missing items

*definition*and*program*expanded the (logic/type theory)-table to a (logic/category theory/type theory)-table and subsumed some of the items into it that were floating around elsewhere.

- Discussion Type
- discussion topicaxiom of choice in type theory
- Category Latest Changes
- Started by Urs
- Comments 8
- Last comment by Urs
- Last Active Sep 4th 2012

at

*axiom of choice*into the section*In dependent type theory*I have moved the explicit statement taken from the entry of dependent type theory (see there for what I am talking about in the following).One technical question: do we need the

`: true`

at the very end of the formal statement of the theorem?

One conceptual question: I feel inclined to add the following Remark to that, on how to think about the fact that the axiom of choice is always true in this sense in type theory. But please let me know what you think:

Heuristically, the reason that the axiom of choice is always true when formulated internally this way in dependent type theory is due to the fact that its

*assumption*thereby is stated in*constructive mathematics*:Stated in informal but internal logic, the axiom of choice says:

*If $B \to A$ is a map all whose fibers are inhabited, then there is a section.*But now if we interpret the assumption clause

*a map all whose fibers are inhabited*constructively, we have to provide a

*constructive proof*that indeed the fibers are inhabited. But such a constructive proof*is*a choice of section.So constructively and internally the axiom is reduced to “If there is a section then there is a section.” And so indeed this is always true.

Would you agree that this captures the state of affairs?

- Discussion Type
- discussion topicpseudocircle
- Category Latest Changes
- Started by Urs
- Comments 7
- Last comment by Urs
- Last Active Sep 4th 2012

stub for

*pseudocircle*(a finite topological space)

- Discussion Type
- discussion topicfundamental group
- Category Latest Changes
- Started by Stephan A Spahn
- Comments 8
- Last comment by Tim_Porter
- Last Active Sep 3rd 2012

- I added a sentence to fundamental group which contains a link to an example for a fundamental group of an affine scheme.

- Discussion Type
- discussion topictotal complex
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by Urs
- Last Active Sep 3rd 2012

split off

*total complex*from*double complex*. Let the Definition-section stubby, as it was, but added a brief remark on exactness and on relation to total simplicial sets, under Dold-Kan and Eilenberg-Zilber. More to be done.

- Discussion Type
- discussion topicinterval object in chain complexes
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Tim_Porter
- Last Active Sep 3rd 2012

- Discussion Type
- discussion topicStructural rules.
- Category Latest Changes
- Started by TobyBartels
- Comments 9
- Last comment by Mike Shulman
- Last Active Sep 3rd 2012

Stubs for structural rule, weakening rule, contraction rule, and exchange rule.

- Discussion Type
- discussion topicdichotomy
- Category Latest Changes
- Started by Todd_Trimble
- Comments 2
- Last comment by Urs
- Last Active Sep 2nd 2012

Speaking of philosophy, I added a little to dichotomy between nice objects and nice categories.

- Discussion Type
- discussion topicAn Introduction to Homological Algebra
- Category Latest Changes
- Started by Urs
- Comments 6
- Last comment by Urs
- Last Active Sep 2nd 2012

- Discussion Type
- discussion topictruncation of a chain complex
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 2nd 2012

it seems that a few days back I had created a note

*truncation of a chain complex*

- Discussion Type
- discussion topicsuspension of a chain complex
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 2nd 2012

I felt like having a simple stand-alone entry

*suspension of a chain complex*, so I created one.

- Discussion Type
- discussion topicDedekind completion of quasiorders
- Category Latest Changes
- Started by TobyBartels
- Comments 2
- Last comment by TobyBartels
- Last Active Sep 2nd 2012

Dedekind completions of quasiorders (not just linear orders) may now be found at Dedekind completion. Example: the lower Dedekind completion of the quasiorder of continuous functions is the quasiorder of lower semicontinuous functions.

- Discussion Type
- discussion topicBinary functions
- Category Latest Changes
- Started by TobyBartels
- Comments 3
- Last comment by TobyBartels
- Last Active Sep 2nd 2012

I put a bunch of stuff there that might be of interest to the logicians and foundationalists among us, although it’s still pretty trivial.

- Discussion Type
- discussion topicReal number object
- Category Latest Changes
- Started by SridharRamesh
- Comments 6
- Last comment by TobyBartels
- Last Active Sep 2nd 2012

- Am I correct in supposing that the first definition of Dedekind cuts at real numbers object is missing an openness condition (as given in the later, power object-using definition on the same page)?

- Discussion Type
- discussion topicchain map
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Sep 1st 2012

some trivial additions to

*chain map*.

- Discussion Type
- discussion topiccoefficient
- Category Latest Changes
- Started by Urs
- Comments 6
- Last comment by Urs
- Last Active Sep 1st 2012

created an entry

*coefficient*and linked it withas well as with

- Discussion Type
- discussion topicMod
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Aug 31st 2012

at

*Mod*I started a new subsection*RMod is an abelian category*, spelling out some of the details of this statement.