Let $R$ be a Noetherian, commutative ring and $M,N$ be finitely generated $R$-modules.

Question: Do the sets of minimal primes of $\text{Ext}^i_R(M,N)$ (for a fixed pair of $M,N$) become periodic for $i\gg 0$?

Background/Motivation: In this part I will assume $R$ local (I don't think it's significant for the question, but some statements will be awkward in general). I was motivated to ask after this recent question.

It is known that the asymptotic behavior of these $\text{Ext}$ is governed by the singularity of $R$. For instance, if $R$ is regular, then $\text{Ext}^i_R(M,N)=0$ for $i>\dim R$ because $R$ has finite global dimension equals to $\dim R$.

If $R$ is a hypersurface, then it follows from Eisenbud's original paper on matrix factorization that the minimal resolution of $M$ becomes eventually periodic of period $2$ after $\dim R$ spots, so the answer in this case is also affirmative.

With a little bit more work, one can show that the supports of $\text{Ext}^i_R(M,N)$ (in fact, the annihilators) become eventually periodic of period $2$ when $R$ is a local complete intersection.

EDIT: As Karl's comment indicated, perhaps a more realistic question is:

Question 2: Is the union of all minimal primes of $\text{Ext}^i_R(M,N)$ for $i>0$ a finite set?

One situation when the answer is trivially yes is when $\text{Spec}R$ has an isolated singularity.

I think the answer is no (even for question 2) in general, but not sure how to construct an example.

Let $R$ be a Noetherian, commutative ring and $M,N$ be finitely generated $R$-modules.

Question: Do the sets of minimal primes of $\text{Ext}^i_R(M,N)$ (for a fixed pair of $M,N$) become periodic for $i\gg 0$?

Background/Motivation: In this part I will assume $R$ local (I don't think it's significant for the question, but some statements will be awkward in general). I was motivated to ask after this recent question.

It is known that the asymptotic behavior of these $\text{Ext}$ is governed by the singularity of $R$. For instance, if $R$ is regular, then $\text{Ext}^i_R(M,N)=0$ for $i>\dim R$ because $R$ has finite global dimension equals to $\dim R$.

If $R$ is a hypersurface, then it follows from Eisenbud's original paper on matrix factorization that the minimal resolution of $M$ becomes eventually periodic of period $2$ after $\dim R$ spots, so the answer in this case is also affirmative.

With a little bit more work, one can show that the supports of $\text{Ext}^i_R(M,N)$ (in fact, the annihilators) become eventually periodic of period $2$ when $R$ is a local complete intersection.

EDIT: As Karl's comment indicated, perhaps a more realistic question is:

Question 2: Is the union of all minimal primes of $\text{Ext}^i_R(M,N)$ for $i>0$ a finite set?

One situation when the answer is trivially yes is when $\text{Spec}R$ has an isolated singularity.

I think the answer is no (even for question 2) in general, but not sure how to construct an example.

Let $R$ be a Noetherian, commutative ring and $M,N$ be finitely generated $R$-modules.

Question: Are the sets of minimal primes of $\text{Ext}^i_R(M,N)$ becomes periodic for $i\gg 0$?

Background/Motivation: In this part I will assume $R$ local (I don't think it's significant for the question, but some statements will be awkward in general). I was motivated to ask after this recent question.

It is known that the asymptotic behavior of these $\text{Ext}$ is governed by the singularity of $R$. For instance, if $R$ is regular, then $\text{Ext}^i_R(M,N)=0$ for $i>\dim R$ because $R$ has finite global dimension equals to $\dim R$.

If $R$ is a hypersurface, then it follows from Eisenbud's original paper on matrix factorization that the minimal resolution of $M$ becomes eventually periodic of period $2$ after $\dim R$ spots, so the answer in this case is also affirmative.

With a little bit more work, one can show that the supports of $\text{Ext}^i_R(M,N)$ (in fact, the annihilators) become eventually periodic of period $2$ when $R$ is a local complete intersection.

One more situation when the answer is yes is when $\text{Spec}R$ has an isolated singularity. Then the support will eventually be just the maximal ideal.

I think the answer is no in general, but not sure how to construct an example.

Let $R$ be a Noetherian, commutative ring and $M,N$ be finitely generated $R$-modules.

Question: Do the sets of minimal primes of $\text{Ext}^i_R(M,N)$ (for a fixed pair of $M,N$) become periodic for $i\gg 0$?

Background/Motivation: In this part I will assume $R$ local (I don't think it's significant for the question, but some statements will be awkward in general). I was motivated to ask after this recent question.

It is known that the asymptotic behavior of these $\text{Ext}$ is governed by the singularity of $R$. For instance, if $R$ is regular, then $\text{Ext}^i_R(M,N)=0$ for $i>\dim R$ because $R$ has finite global dimension equals to $\dim R$.

If $R$ is a hypersurface, then it follows from Eisenbud's original paper on matrix factorization that the minimal resolution of $M$ becomes eventually periodic of period $2$ after $\dim R$ spots, so the answer in this case is also affirmative.

With a little bit more work, one can show that the supports of $\text{Ext}^i_R(M,N)$ (in fact, the annihilators) become eventually periodic of period $2$ when $R$ is a local complete intersection.

EDIT: As Karl's comment indicated, perhaps a more realistic question is:

Question 2: Is the union of all minimal primes of $\text{Ext}^i_R(M,N)$ for $i>0$ a finite set?

One situation when the answer is trivially yes is when $\text{Spec}R$ has an isolated singularity.

I think the answer is no (even for question 2) in general, but not sure how to construct an example.