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Part of higher category theory that for instance in Algebraic Topology enables us to capture finer homotopic distinctions. As in say Eilenberg-Maclane spaces.

3 votes
0 answers
177 views

Colimits in the idempotent completion (Proof of Theorem 5.5.1.1, HTT)

The following fact seems to be implicitly used in the proof of (4)$\implies$(5) of Theorem 5.5.1.1 of Lurie's Higher Tops Theory: Let $\kappa$ be a small regular cardinal, and let $\mathcal{C}$ be a …
Ken's user avatar
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6 votes
3 answers
562 views

Density Theorem for $\infty$-Categories (HTT, Lemma 5.1.5.3)

The density theorem in the ordinary category theory asserts that every presheaf on a small category is a colimit of representables in a canonical way. In Lemma 5.1.5.3 of Higher Topos Theory, Lurie pr …
Ken's user avatar
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4 votes
1 answer
225 views

The effect of straightening on morphisms

This is similar to another question on MO, but is different. Let $p:\mathcal{E}\to\mathcal{C}$ be a right fibration between $\infty$-categories. As explained in Lurie's HTT, $\S$2.1, we can consider $ …
Ken's user avatar
  • 2,292
6 votes
0 answers
117 views

Homotopy fibers in the Joyal model structure and the Kan–Quillen model structure

While playing around with $\infty$-categories, I ran into the following problem: Let $p:\mathcal{C}\to\mathcal{D}$ be a functor of $\infty$-categories. Does one of the following condition imply the o …
Ken's user avatar
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5 votes
1 answer
184 views

Localization and space of morphisms

I have a question regarding the proof of Proposition 2.19 of Factorization homology of topological manifolds by Ayala and Francis. In the final paragraph of the proof (more specifically, in the second …
Ken's user avatar
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7 votes
1 answer
222 views

$\operatorname{Fun}(\mathcal{C},\mathcal{D})^n$ is a subcategory of $\operatorname{Fun}(\mat...

Let $\mathcal{C}$ and $\mathcal{D}$ be $\infty$-categories (by which I mean quasicategories, though I suspect that it hardly matters), and let $n\geq 1$ be an integer. There is a functor $$\theta:\ope …
Ken's user avatar
  • 2,292
4 votes
0 answers
57 views

Equivalence of two definitions of relative limits

This is a question on seemingly equivalent definitions of relative limits, formulated in the language of quasi-categories. I will use notations from Higher Topos Theory. Let $p:\mathcal{C}\to\mathcal …
Ken's user avatar
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13 votes
0 answers
578 views

Higher Algebra, Theorem 2.4.3.18 and Remark 2.4.3.6

In his book Higher Algebra, Lurie introduces the notion of generalized $\infty$-operads ($\S$2.3.2). Roughly speaking, a generalized $\infty$-operad is a "family" of $\infty$-operads parametrized by a …
Ken's user avatar
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5 votes
1 answer
246 views

Cofinal maps from posets (HTT, 4.2.3.16)

I do not understand the proof of Variant 4.2.3.16 of Higher Topos Theory by Jacob Lurie, and I need help. Variant 4.2.3.16 asserts the following: ($\diamond$) Let $K$ be a finite simplicial set. The …
Ken's user avatar
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10 votes
2 answers
691 views

Effective epimorphisms and 0-truncations (HTT, 7.2.1.14)

In Proposition 7.2.1.14 of Higher Topos Theory, Lurie asserts the following: Let $\mathcal{X}$ be an $\infty$-topos and let $\tau_{\leq0}:\mathcal{X}\to\tau_{\leq0}\mathcal{X}$ denote a left adjoint …
Ken's user avatar
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7 votes
2 answers
385 views

HTT, Remark 4.2.4.5

In his book Higher Topos Theory, Lurie proves that in some favorable cases, functor categories of $\infty$-categories admits a rigid model. More precisely, he proves in Proposition 4.2.4.4 the followi …
Ken's user avatar
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8 votes
1 answer
470 views

Why does the tangent classifier classify the tangent (micro)bundle?

Let $\mathcal{M}\mathrm{fld}_n$ denote the $\infty$-category of topological manifolds (without boundary) and embeddings; more precisely, it is the homotopy coherent nerve of the simplicial category wh …
Ken's user avatar
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4 votes
0 answers
76 views

On coproducts of presentably symmetric monoidal $\infty$-categories

Let $\mathcal{A}$ and $\mathcal{B}$ be presentably symmetric monoidal $\infty$-categories, i.e., symmetric monoidal $\infty$-categories whose underlying $\infty$-category are presentable and whose ten …
Ken's user avatar
  • 2,292
6 votes
0 answers
302 views

Functorial identification of the mapping spaces of the arrow category of an $\infty$-category

Let $\mathcal{C}$ be a small $\infty$-category. Using the straightening-unstraightening construction, we can define a hom-functor of $\mathcal{C}$ as a functor $\mathcal{C}(-,-):\mathcal{C}^{\mathrm{o …
Ken's user avatar
  • 2,292
6 votes
0 answers
237 views

Higher Algebra, Propositions 2.3.4.5 and 2.3.4.9

I am reading the proof of Propositions 2.3.4.5 of Higher Algebra by Jacob Lurie. There is a part that I don't understand, and I need someone's help. In the book, Lurie introduces the notion of familie …
Ken's user avatar
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