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decide cartesian filtered colimits for Haus, Meas, Top, Top*
1 parent 094b22e commit 692a114

7 files changed

Lines changed: 9 additions & 18 deletions

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database/data/004_property-assignments/Haus.sql

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@@ -67,7 +67,7 @@ VALUES
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),
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(
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'Haus',
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'cartesian closed',
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'cartesian filtered colimits',
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FALSE,
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'It is shown in <a href="https://math.stackexchange.com/questions/1255678">MSE/1255678</a> that $\mathbb{Q} \times - : \mathbf{Top} \to \mathbf{Top}$ does not preserve sequential colimits (so that it cannot be a left adjoint). The same example also works in $\mathbf{Haus}$: Surely $\mathbb{Q}$ is Hausdorff, $X_n$ is Hausdorff, as is their colimit $X$, and the colimit (taken in $\mathbf{Top}$) of the $X_n \times \mathbb{Q}$ admits a bijective continuous map to a Hausdorff space, therefore is also Hausdorff, meaning it is also the colimit taken in $\mathbf{Haus}$.'
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),

database/data/004_property-assignments/Meas.sql

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@@ -67,13 +67,7 @@ VALUES
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),
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(
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'Meas',
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'cartesian closed',
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FALSE,
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'The functors $X \times -$ do not preserve filtered colimits by <a href="https://math.stackexchange.com/questions/5027218" target="_blank">MSE/5027218</a>, hence cannot be left adjoints.'
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),
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(
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'Meas',
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'exact filtered colimits',
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'cartesian filtered colimits',
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FALSE,
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'See <a href="https://math.stackexchange.com/questions/5027218" target="_blank">MSE/5027218</a>.'
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),

database/data/004_property-assignments/Top.sql

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@@ -73,9 +73,9 @@ VALUES
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),
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(
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'Top',
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'cartesian closed',
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'cartesian filtered colimits',
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FALSE,
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'The functor $\mathbb{Q} \times - : \mathbf{Top} \to \mathbf{Top}$ does not preserve colimits, hence has no right adjoint. See <a href="https://math.stackexchange.com/questions/2969372" target="_blank">MSE/2969372</a> for a proof.'
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'The functor $\mathbb{Q} \times - : \mathbf{Top} \to \mathbf{Top}$ does not preserve colimits, see <a href="https://math.stackexchange.com/questions/2969372" target="_blank">MSE/2969372</a>.'
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),
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(
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'Top',
@@ -95,12 +95,6 @@ VALUES
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FALSE,
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'If $X$ is a set, consider the discrete space $X_d$ on $X$ and the indiscrete space $X_i$ on $X$. The identity map $X \to X$ lifts to a continuous map $X_d \to X_i$, which is bijective and therefore both a mono- and an epimorphism, but it is not an isomorphism unless $X$ has at most one element.'
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),
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(
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'Top',
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'exact filtered colimits',
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FALSE,
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'See <a href="https://math.stackexchange.com/questions/1255678" target="_blank">MSE/1255678</a>.'
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),
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(
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'Top',
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'skeletal',

database/data/004_property-assignments/Top_pointed.sql

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@@ -103,9 +103,9 @@ VALUES
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),
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(
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'Top*',
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'exact filtered colimits',
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'cartesian filtered colimits',
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FALSE,
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'See <a href="https://math.stackexchange.com/questions/1255678" target="_blank">MSE/1255678</a> (the counterexample also works for pointed spaces).'
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'The functor $\mathbb{Q} \times - : \mathbf{Top}_* \to \mathbf{Top}_*$ does not preserve colimits, see <a href="https://math.stackexchange.com/questions/2969372" target="_blank">MSE/2969372</a>. The counterexample also works for pointed spaces.'
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),
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(
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'Top*',

scripts/expected-data/Ab.json

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@@ -23,6 +23,7 @@
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"epi-regular": true,
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"equalizers": true,
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"exact filtered colimits": true,
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"cartesian filtered colimits": true,
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"filtered colimits": true,
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"cofiltered limits": true,
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"directed limits": true,

scripts/expected-data/Set.json

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@@ -25,6 +25,7 @@
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"epi-regular": true,
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"equalizers": true,
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"exact filtered colimits": true,
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"cartesian filtered colimits": true,
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"filtered colimits": true,
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"cofiltered limits": true,
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"directed limits": true,

scripts/expected-data/Top.json

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@@ -78,6 +78,7 @@
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"essentially finite": false,
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"essentially small": false,
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"exact filtered colimits": false,
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"cartesian filtered colimits": false,
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"finitary algebraic": false,
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"finite": false,
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"Grothendieck abelian": false,

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