Category Theory Study Group
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Resources for students, mathematicians, and scientists interested in category theory
Resources for students, mathematicians, and scientists interested in category theory

28 followers
Category Theory Study Group's posts
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Are we not doing meetings anymore ? I did not get invites for last week or this week.﻿
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Week Ten Meeting: §5.1 and §5.2 of David Spivak's Category Theory for the Sciences

Week 10 and we're finally getting into the meat of category theory!﻿
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Last week we made it through most of 5.1, so this week we'll finish it up and hopefully make it through 5.2. If time allows and people have had the time, we'll delve into 5.3.﻿
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The author is asking about Homomorphism of FLin. In section 4.4.4 he talks about morphism of orders. If s1 <= s2 then f(s1) <= f(s2). Also, order is reflexive (s <= s). So when we have a morphism from FLin[2] to FLin[3] we need to pick 3 elements in…﻿
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Apologies for the late notice, but I've been travelling for a chunk of the past week.

In this session, we'll cover problems/questions from week nine of the syllabus (http://cat.boffosocko.com/syllabus):

5.1 Categories and Functors
5.2

A hangout for those studying category theory via http://cat.boffosocko.com

Everyone will generally be expected to have read the appropriate section(s) and bring their questions/issues so the group can attempt to cover and clarify any issues anyone may be having. If you have an questions about previous material, feel free to bring those up too.

Feel free to use the Q&A function to post your questions in advance or during the hangout.  You can also always register at the groups main site and post up your questions there for everyone to work on/answer via the comments section.﻿
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In section 5.1.1 where category is defined the author says B. for every pair x, y ∈ Ob(C), a set HomC(x,y)∈Set; it is called the hom-set from x to y; its elements are called morphisms from x to y;2 Footnote 2 says The reason for the notation Hom and the…﻿
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In section 5.2.1.21 author talks about graph-indexing category(GrIn) and symmetric graph-indexing category(SGrIn). Ex. 5.2.1.26 asks How many functors are there of the form GrIn → SGrIn? I did not understand the answer and explanation given in the…﻿
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In the remark author says: A. there is a function U:Ob(Q)→Ob(C), B. for all a,b∈Ob(Q), we have an injection U:HomQ(a,b)↪HomC(U(a),U(b)), Why is the function and injection both called U ? Shouldn’t the injection be called something other than U ? This is…﻿
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(Sadly, it looks like  is stuck this evening and won't be able to "host" this week's meeting. He's gotten someone to start and keep the meeting going for those who want to join and chat however. He should  be back for next Monday.)

In this session, we'll cover problems/questions from week six of the (now modified) syllabus (http://cat.boffosocko.com/syllabus):

5.1 Categories and Functors

A hangout for those studying category theory via http://cat.boffosocko.com

Everyone will generally be expected to have read the appropriate section(s) and bring their questions/issues so the group can attempt to cover and clarify any issues anyone may be having. If you have an questions about previous material, feel free to bring those up too.

Feel free to use the Q&A function to post your questions in advance or during the hangout.  You can also always register at the groups main site and post up your questions there for everyone to work on/answer via the comments section.﻿
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Category Theory Week Seven Meeting: §4.4 and §4.5 #CTSG15

Week Seven This week’s Google Hangout (RSVP here) will cover problems/questions from week seven of the syllabus: 4.4 Orders 4.5 Databases: schemas and instances If you’re joining us in progress, please feel free to add in any questions you might have…﻿