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YCor
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YCor
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Consider$\newcommand{\Grp}{\mathrm{Grp}}$Consider the category of groups $Grp$$\Grp$, and within it we have the solvable groups $S$. Then any group $G$ determines the functor from solvable groups: $$h_G:=\text{hom}_{Grp}(\_,G):S^{op}\rightarrow \text{Set}$$$$h_G:=\text{hom}_{\Grp}(\_,G):S^{\mathrm{op}}\rightarrow \text{Set}$$

Does this functor determine the group $G$? More concretely, if we have a natural bijection $$\text{hom}_{Grp}(A,G)\cong \text{hom}_{Grp}(A,G')$$$$\text{hom}_{\Grp}(A,G)\cong \text{hom}_{\Grp}(A,G')$$ for all solvable groups $A$, must this be induced by an isomorphism $G\rightarrow G'$?

Are there any circumstances/more restrictive hypotheses where the answer to this is known to be affirmative, for conceptual reasons?

By other circumstance, I mean imposing finiteness conditions, or other "well behavednessbehavior conditions", or looking at group objects in a more exotic category, etc. I mean conceptual reasons in the sense of being independent of a classification result of all the objects involved, it wouldn't surprise me if this result were true for finite groups, but only verifiable by induction/case checking for the simple groups. Though interesting, I am more interested in any setting where we have a well understood reason for this to hold, or counterexamples/obstacles to its potential truth.

Consider the category of groups $Grp$, and within it we have the solvable groups $S$. Then any group $G$ determines the functor from solvable groups: $$h_G:=\text{hom}_{Grp}(\_,G):S^{op}\rightarrow \text{Set}$$

Does this functor determine the group $G$? More concretely, if we have a natural bijection $$\text{hom}_{Grp}(A,G)\cong \text{hom}_{Grp}(A,G')$$ for all solvable groups $A$, must this be induced by an isomorphism $G\rightarrow G'$?

Are there any circumstances/more restrictive hypotheses where the answer to this is known to be affirmative, for conceptual reasons?

By other circumstance, I mean imposing finiteness conditions, or other "well behavedness conditions", or looking at group objects in a more exotic category, etc. I mean conceptual reasons in the sense of being independent of a classification result of all the objects involved, it wouldn't surprise me if this result were true for finite groups, but only verifiable by induction/case checking for the simple groups. Though interesting, I am more interested in any setting where we have a well understood reason for this to hold, or counterexamples/obstacles to its potential truth.

$\newcommand{\Grp}{\mathrm{Grp}}$Consider the category of groups $\Grp$, and within it we have the solvable groups $S$. Then any group $G$ determines the functor from solvable groups: $$h_G:=\text{hom}_{\Grp}(\_,G):S^{\mathrm{op}}\rightarrow \text{Set}$$

Does this functor determine the group $G$? More concretely, if we have a natural bijection $$\text{hom}_{\Grp}(A,G)\cong \text{hom}_{\Grp}(A,G')$$ for all solvable groups $A$, must this be induced by an isomorphism $G\rightarrow G'$?

Are there any circumstances/more restrictive hypotheses where the answer to this is known to be affirmative, for conceptual reasons?

By other circumstance, I mean imposing finiteness conditions, or other "well behavior conditions", or looking at group objects in a more exotic category, etc. I mean conceptual reasons in the sense of being independent of a classification result of all the objects involved, it wouldn't surprise me if this result were true for finite groups, but only verifiable by induction/case checking for the simple groups. Though interesting, I am more interested in any setting where we have a well understood reason for this to hold, or counterexamples/obstacles to its potential truth.

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Chris H
Chris H
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Are groups determined by their morphisms from solvable groups?

Consider the category of groups $Grp$, and within it we have the solvable groups $S$. Then any group $G$ determines the functor from solvable groups: $$h_G:=\text{hom}_{Grp}(\_,G):S^{op}\rightarrow \text{Set}$$

Does this functor determine the group $G$? More concretely, if we have a natural bijection $$\text{hom}_{Grp}(A,G)\cong \text{hom}_{Grp}(A,G')$$ for all solvable groups $A$, must this be induced by an isomorphism $G\rightarrow G'$?

Are there any circumstances/more restrictive hypotheses where the answer to this is known to be affirmative, for conceptual reasons?

By other circumstance, I mean imposing finiteness conditions, or other "well behavedness conditions", or looking at group objects in a more exotic category, etc. I mean conceptual reasons in the sense of being independent of a classification result of all the objects involved, it wouldn't surprise me if this result were true for finite groups, but only verifiable by induction/case checking for the simple groups. Though interesting, I am more interested in any setting where we have a well understood reason for this to hold, or counterexamples/obstacles to its potential truth.