Characterising minors of diagonal matrices












4












$begingroup$


Let $k,d$ be positive integers, $1<k<d$. Let $lambda_I=lambda_{i_1,ldots,i_k}$ be real numbers, indexed by multi-indices $I=(i_1,ldots,i_k)$, where $1le i_1<ldots<i_k le d$.



Are there necessary and sufficient conditions on $lambda_{i_1,ldots,i_k}$ which are equivalent to the existence of $sigma_1,ldots,sigma_d in mathbb{R}$ such that $lambda_{i_1,ldots,i_k}=sigma_{i_1}cdot ldotscdotsigma_{i_k}$ holds for every multi-index $I$?




In other words, I am asking whether we can characterise which sequences of real numbers can arise as the $k$-minors of diagonal $d times d$ matrices?




I am interested mainly in the case where all the $lambda_{i_1,ldots,i_k}$ are non-zero.



I have heard that the general problem of recognizing $k$-minors of arbitrary square matrices is open, but I am hoping that for diagonal matrices, the situation maybe better understood.



I guess this should be easier by starting over $mathbb{C}$. What is known about that case?



Commnet: If I understand correctly, the Plucker relations only describe the minors of top-degree of a non-square matrix. Here I am talking about the minors of degree $k$, when $1<k<d$, i.e. non-top minors of a square matrix.










share|cite|improve this question











$endgroup$












  • $begingroup$
    I guess you mean $lambda_{i_1, dots, i_k} = sigma_{i_1} cdot ... cdot sigma_{i_k}$?
    $endgroup$
    – Severin Schraven
    Jan 27 at 12:51












  • $begingroup$
    Yes, thank you! corrected now.
    $endgroup$
    – Asaf Shachar
    Jan 27 at 13:03
















4












$begingroup$


Let $k,d$ be positive integers, $1<k<d$. Let $lambda_I=lambda_{i_1,ldots,i_k}$ be real numbers, indexed by multi-indices $I=(i_1,ldots,i_k)$, where $1le i_1<ldots<i_k le d$.



Are there necessary and sufficient conditions on $lambda_{i_1,ldots,i_k}$ which are equivalent to the existence of $sigma_1,ldots,sigma_d in mathbb{R}$ such that $lambda_{i_1,ldots,i_k}=sigma_{i_1}cdot ldotscdotsigma_{i_k}$ holds for every multi-index $I$?




In other words, I am asking whether we can characterise which sequences of real numbers can arise as the $k$-minors of diagonal $d times d$ matrices?




I am interested mainly in the case where all the $lambda_{i_1,ldots,i_k}$ are non-zero.



I have heard that the general problem of recognizing $k$-minors of arbitrary square matrices is open, but I am hoping that for diagonal matrices, the situation maybe better understood.



I guess this should be easier by starting over $mathbb{C}$. What is known about that case?



Commnet: If I understand correctly, the Plucker relations only describe the minors of top-degree of a non-square matrix. Here I am talking about the minors of degree $k$, when $1<k<d$, i.e. non-top minors of a square matrix.










share|cite|improve this question











$endgroup$












  • $begingroup$
    I guess you mean $lambda_{i_1, dots, i_k} = sigma_{i_1} cdot ... cdot sigma_{i_k}$?
    $endgroup$
    – Severin Schraven
    Jan 27 at 12:51












  • $begingroup$
    Yes, thank you! corrected now.
    $endgroup$
    – Asaf Shachar
    Jan 27 at 13:03














4












4








4


1



$begingroup$


Let $k,d$ be positive integers, $1<k<d$. Let $lambda_I=lambda_{i_1,ldots,i_k}$ be real numbers, indexed by multi-indices $I=(i_1,ldots,i_k)$, where $1le i_1<ldots<i_k le d$.



Are there necessary and sufficient conditions on $lambda_{i_1,ldots,i_k}$ which are equivalent to the existence of $sigma_1,ldots,sigma_d in mathbb{R}$ such that $lambda_{i_1,ldots,i_k}=sigma_{i_1}cdot ldotscdotsigma_{i_k}$ holds for every multi-index $I$?




In other words, I am asking whether we can characterise which sequences of real numbers can arise as the $k$-minors of diagonal $d times d$ matrices?




I am interested mainly in the case where all the $lambda_{i_1,ldots,i_k}$ are non-zero.



I have heard that the general problem of recognizing $k$-minors of arbitrary square matrices is open, but I am hoping that for diagonal matrices, the situation maybe better understood.



I guess this should be easier by starting over $mathbb{C}$. What is known about that case?



Commnet: If I understand correctly, the Plucker relations only describe the minors of top-degree of a non-square matrix. Here I am talking about the minors of degree $k$, when $1<k<d$, i.e. non-top minors of a square matrix.










share|cite|improve this question











$endgroup$




Let $k,d$ be positive integers, $1<k<d$. Let $lambda_I=lambda_{i_1,ldots,i_k}$ be real numbers, indexed by multi-indices $I=(i_1,ldots,i_k)$, where $1le i_1<ldots<i_k le d$.



Are there necessary and sufficient conditions on $lambda_{i_1,ldots,i_k}$ which are equivalent to the existence of $sigma_1,ldots,sigma_d in mathbb{R}$ such that $lambda_{i_1,ldots,i_k}=sigma_{i_1}cdot ldotscdotsigma_{i_k}$ holds for every multi-index $I$?




In other words, I am asking whether we can characterise which sequences of real numbers can arise as the $k$-minors of diagonal $d times d$ matrices?




I am interested mainly in the case where all the $lambda_{i_1,ldots,i_k}$ are non-zero.



I have heard that the general problem of recognizing $k$-minors of arbitrary square matrices is open, but I am hoping that for diagonal matrices, the situation maybe better understood.



I guess this should be easier by starting over $mathbb{C}$. What is known about that case?



Commnet: If I understand correctly, the Plucker relations only describe the minors of top-degree of a non-square matrix. Here I am talking about the minors of degree $k$, when $1<k<d$, i.e. non-top minors of a square matrix.







algebraic-geometry polynomials determinant exterior-algebra real-algebraic-geometry






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 27 at 13:03







Asaf Shachar

















asked Jan 27 at 12:36









Asaf ShacharAsaf Shachar

5,78431145




5,78431145












  • $begingroup$
    I guess you mean $lambda_{i_1, dots, i_k} = sigma_{i_1} cdot ... cdot sigma_{i_k}$?
    $endgroup$
    – Severin Schraven
    Jan 27 at 12:51












  • $begingroup$
    Yes, thank you! corrected now.
    $endgroup$
    – Asaf Shachar
    Jan 27 at 13:03


















  • $begingroup$
    I guess you mean $lambda_{i_1, dots, i_k} = sigma_{i_1} cdot ... cdot sigma_{i_k}$?
    $endgroup$
    – Severin Schraven
    Jan 27 at 12:51












  • $begingroup$
    Yes, thank you! corrected now.
    $endgroup$
    – Asaf Shachar
    Jan 27 at 13:03
















$begingroup$
I guess you mean $lambda_{i_1, dots, i_k} = sigma_{i_1} cdot ... cdot sigma_{i_k}$?
$endgroup$
– Severin Schraven
Jan 27 at 12:51






$begingroup$
I guess you mean $lambda_{i_1, dots, i_k} = sigma_{i_1} cdot ... cdot sigma_{i_k}$?
$endgroup$
– Severin Schraven
Jan 27 at 12:51














$begingroup$
Yes, thank you! corrected now.
$endgroup$
– Asaf Shachar
Jan 27 at 13:03




$begingroup$
Yes, thank you! corrected now.
$endgroup$
– Asaf Shachar
Jan 27 at 13:03










1 Answer
1






active

oldest

votes


















2












$begingroup$

Let me give an answer over complex numbers.
The conditions are the following: for each pair $i ne j$ and for each pair of subsets $I,J subset {1,dots,d} setminus {i,j}$ of cardinality $k - 1$ one has a relation
$$
lambda_{I sqcup {i}} cdot lambda_{J sqcup {j}} =
lambda_{I sqcup {j}} cdot lambda_{J sqcup {i}}.
$$

Clearly these relations are necessary.



Let us also show that they are sufficient. In fact, let me just explain how $sigma_i$ can be reconstructed. Take any set $J subset {1,dots,d-1}$ of cardinality $k$. Then set
$$
sigma_d = sqrt[k]{frac{prod_{j in J} lambda_{J setminus {j} sqcup {d}}}{lambda_J^{k-1}}}.
$$

After that for each $i in {1,dots,d-1}$ choose $J subset {1,dots,d-1} setminus {i}$ of cardinality $k-1$ and set
$$
sigma_i = frac{prod_{j in J} lambda_{J setminus {j} sqcup {i,d}}}{lambda_{J sqcup {i}}^{k-2}sigma_d^{k-1}}.
$$

One can check that this solves the required equations.



Over real numbers the only extra problem is the existence of the root.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    I think we have $k$ fixed.
    $endgroup$
    – Severin Schraven
    Jan 27 at 13:06










  • $begingroup$
    @SeverinSchraven: You are right, I will change the answer.
    $endgroup$
    – Sasha
    Jan 27 at 13:50










  • $begingroup$
    @AsafShachar: Thanks for correction!
    $endgroup$
    – Sasha
    Jan 27 at 14:53










  • $begingroup$
    If $k$ is even, don't we have to be careful with the choice of the sign of $sigma_d$? How do you know that you can pick the positive? Respectively, that you can take the kth root of the expression?
    $endgroup$
    – Severin Schraven
    Jan 27 at 14:57






  • 1




    $begingroup$
    @SeverinSchraven I will just note that when you work over the complex numbers, you don't really have a problem: Instead of possible non-existence of roots (in the real case), you now have too many of them. However, it does not matter "which one you choose", since choosing a different $k$-th root only amounts to multiplying all the $sigma_i$ by some specific $k$-th root of unity, which is the only ambiguity we have here. (This was to be expected in advance, as I will elaborate in the question).
    $endgroup$
    – Asaf Shachar
    Jan 27 at 15:08













Your Answer





StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














draft saved

draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3089508%2fcharacterising-minors-of-diagonal-matrices%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown

























1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









2












$begingroup$

Let me give an answer over complex numbers.
The conditions are the following: for each pair $i ne j$ and for each pair of subsets $I,J subset {1,dots,d} setminus {i,j}$ of cardinality $k - 1$ one has a relation
$$
lambda_{I sqcup {i}} cdot lambda_{J sqcup {j}} =
lambda_{I sqcup {j}} cdot lambda_{J sqcup {i}}.
$$

Clearly these relations are necessary.



Let us also show that they are sufficient. In fact, let me just explain how $sigma_i$ can be reconstructed. Take any set $J subset {1,dots,d-1}$ of cardinality $k$. Then set
$$
sigma_d = sqrt[k]{frac{prod_{j in J} lambda_{J setminus {j} sqcup {d}}}{lambda_J^{k-1}}}.
$$

After that for each $i in {1,dots,d-1}$ choose $J subset {1,dots,d-1} setminus {i}$ of cardinality $k-1$ and set
$$
sigma_i = frac{prod_{j in J} lambda_{J setminus {j} sqcup {i,d}}}{lambda_{J sqcup {i}}^{k-2}sigma_d^{k-1}}.
$$

One can check that this solves the required equations.



Over real numbers the only extra problem is the existence of the root.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    I think we have $k$ fixed.
    $endgroup$
    – Severin Schraven
    Jan 27 at 13:06










  • $begingroup$
    @SeverinSchraven: You are right, I will change the answer.
    $endgroup$
    – Sasha
    Jan 27 at 13:50










  • $begingroup$
    @AsafShachar: Thanks for correction!
    $endgroup$
    – Sasha
    Jan 27 at 14:53










  • $begingroup$
    If $k$ is even, don't we have to be careful with the choice of the sign of $sigma_d$? How do you know that you can pick the positive? Respectively, that you can take the kth root of the expression?
    $endgroup$
    – Severin Schraven
    Jan 27 at 14:57






  • 1




    $begingroup$
    @SeverinSchraven I will just note that when you work over the complex numbers, you don't really have a problem: Instead of possible non-existence of roots (in the real case), you now have too many of them. However, it does not matter "which one you choose", since choosing a different $k$-th root only amounts to multiplying all the $sigma_i$ by some specific $k$-th root of unity, which is the only ambiguity we have here. (This was to be expected in advance, as I will elaborate in the question).
    $endgroup$
    – Asaf Shachar
    Jan 27 at 15:08


















2












$begingroup$

Let me give an answer over complex numbers.
The conditions are the following: for each pair $i ne j$ and for each pair of subsets $I,J subset {1,dots,d} setminus {i,j}$ of cardinality $k - 1$ one has a relation
$$
lambda_{I sqcup {i}} cdot lambda_{J sqcup {j}} =
lambda_{I sqcup {j}} cdot lambda_{J sqcup {i}}.
$$

Clearly these relations are necessary.



Let us also show that they are sufficient. In fact, let me just explain how $sigma_i$ can be reconstructed. Take any set $J subset {1,dots,d-1}$ of cardinality $k$. Then set
$$
sigma_d = sqrt[k]{frac{prod_{j in J} lambda_{J setminus {j} sqcup {d}}}{lambda_J^{k-1}}}.
$$

After that for each $i in {1,dots,d-1}$ choose $J subset {1,dots,d-1} setminus {i}$ of cardinality $k-1$ and set
$$
sigma_i = frac{prod_{j in J} lambda_{J setminus {j} sqcup {i,d}}}{lambda_{J sqcup {i}}^{k-2}sigma_d^{k-1}}.
$$

One can check that this solves the required equations.



Over real numbers the only extra problem is the existence of the root.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    I think we have $k$ fixed.
    $endgroup$
    – Severin Schraven
    Jan 27 at 13:06










  • $begingroup$
    @SeverinSchraven: You are right, I will change the answer.
    $endgroup$
    – Sasha
    Jan 27 at 13:50










  • $begingroup$
    @AsafShachar: Thanks for correction!
    $endgroup$
    – Sasha
    Jan 27 at 14:53










  • $begingroup$
    If $k$ is even, don't we have to be careful with the choice of the sign of $sigma_d$? How do you know that you can pick the positive? Respectively, that you can take the kth root of the expression?
    $endgroup$
    – Severin Schraven
    Jan 27 at 14:57






  • 1




    $begingroup$
    @SeverinSchraven I will just note that when you work over the complex numbers, you don't really have a problem: Instead of possible non-existence of roots (in the real case), you now have too many of them. However, it does not matter "which one you choose", since choosing a different $k$-th root only amounts to multiplying all the $sigma_i$ by some specific $k$-th root of unity, which is the only ambiguity we have here. (This was to be expected in advance, as I will elaborate in the question).
    $endgroup$
    – Asaf Shachar
    Jan 27 at 15:08
















2












2








2





$begingroup$

Let me give an answer over complex numbers.
The conditions are the following: for each pair $i ne j$ and for each pair of subsets $I,J subset {1,dots,d} setminus {i,j}$ of cardinality $k - 1$ one has a relation
$$
lambda_{I sqcup {i}} cdot lambda_{J sqcup {j}} =
lambda_{I sqcup {j}} cdot lambda_{J sqcup {i}}.
$$

Clearly these relations are necessary.



Let us also show that they are sufficient. In fact, let me just explain how $sigma_i$ can be reconstructed. Take any set $J subset {1,dots,d-1}$ of cardinality $k$. Then set
$$
sigma_d = sqrt[k]{frac{prod_{j in J} lambda_{J setminus {j} sqcup {d}}}{lambda_J^{k-1}}}.
$$

After that for each $i in {1,dots,d-1}$ choose $J subset {1,dots,d-1} setminus {i}$ of cardinality $k-1$ and set
$$
sigma_i = frac{prod_{j in J} lambda_{J setminus {j} sqcup {i,d}}}{lambda_{J sqcup {i}}^{k-2}sigma_d^{k-1}}.
$$

One can check that this solves the required equations.



Over real numbers the only extra problem is the existence of the root.






share|cite|improve this answer











$endgroup$



Let me give an answer over complex numbers.
The conditions are the following: for each pair $i ne j$ and for each pair of subsets $I,J subset {1,dots,d} setminus {i,j}$ of cardinality $k - 1$ one has a relation
$$
lambda_{I sqcup {i}} cdot lambda_{J sqcup {j}} =
lambda_{I sqcup {j}} cdot lambda_{J sqcup {i}}.
$$

Clearly these relations are necessary.



Let us also show that they are sufficient. In fact, let me just explain how $sigma_i$ can be reconstructed. Take any set $J subset {1,dots,d-1}$ of cardinality $k$. Then set
$$
sigma_d = sqrt[k]{frac{prod_{j in J} lambda_{J setminus {j} sqcup {d}}}{lambda_J^{k-1}}}.
$$

After that for each $i in {1,dots,d-1}$ choose $J subset {1,dots,d-1} setminus {i}$ of cardinality $k-1$ and set
$$
sigma_i = frac{prod_{j in J} lambda_{J setminus {j} sqcup {i,d}}}{lambda_{J sqcup {i}}^{k-2}sigma_d^{k-1}}.
$$

One can check that this solves the required equations.



Over real numbers the only extra problem is the existence of the root.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Jan 27 at 14:53

























answered Jan 27 at 13:05









SashaSasha

5,178139




5,178139












  • $begingroup$
    I think we have $k$ fixed.
    $endgroup$
    – Severin Schraven
    Jan 27 at 13:06










  • $begingroup$
    @SeverinSchraven: You are right, I will change the answer.
    $endgroup$
    – Sasha
    Jan 27 at 13:50










  • $begingroup$
    @AsafShachar: Thanks for correction!
    $endgroup$
    – Sasha
    Jan 27 at 14:53










  • $begingroup$
    If $k$ is even, don't we have to be careful with the choice of the sign of $sigma_d$? How do you know that you can pick the positive? Respectively, that you can take the kth root of the expression?
    $endgroup$
    – Severin Schraven
    Jan 27 at 14:57






  • 1




    $begingroup$
    @SeverinSchraven I will just note that when you work over the complex numbers, you don't really have a problem: Instead of possible non-existence of roots (in the real case), you now have too many of them. However, it does not matter "which one you choose", since choosing a different $k$-th root only amounts to multiplying all the $sigma_i$ by some specific $k$-th root of unity, which is the only ambiguity we have here. (This was to be expected in advance, as I will elaborate in the question).
    $endgroup$
    – Asaf Shachar
    Jan 27 at 15:08




















  • $begingroup$
    I think we have $k$ fixed.
    $endgroup$
    – Severin Schraven
    Jan 27 at 13:06










  • $begingroup$
    @SeverinSchraven: You are right, I will change the answer.
    $endgroup$
    – Sasha
    Jan 27 at 13:50










  • $begingroup$
    @AsafShachar: Thanks for correction!
    $endgroup$
    – Sasha
    Jan 27 at 14:53










  • $begingroup$
    If $k$ is even, don't we have to be careful with the choice of the sign of $sigma_d$? How do you know that you can pick the positive? Respectively, that you can take the kth root of the expression?
    $endgroup$
    – Severin Schraven
    Jan 27 at 14:57






  • 1




    $begingroup$
    @SeverinSchraven I will just note that when you work over the complex numbers, you don't really have a problem: Instead of possible non-existence of roots (in the real case), you now have too many of them. However, it does not matter "which one you choose", since choosing a different $k$-th root only amounts to multiplying all the $sigma_i$ by some specific $k$-th root of unity, which is the only ambiguity we have here. (This was to be expected in advance, as I will elaborate in the question).
    $endgroup$
    – Asaf Shachar
    Jan 27 at 15:08


















$begingroup$
I think we have $k$ fixed.
$endgroup$
– Severin Schraven
Jan 27 at 13:06




$begingroup$
I think we have $k$ fixed.
$endgroup$
– Severin Schraven
Jan 27 at 13:06












$begingroup$
@SeverinSchraven: You are right, I will change the answer.
$endgroup$
– Sasha
Jan 27 at 13:50




$begingroup$
@SeverinSchraven: You are right, I will change the answer.
$endgroup$
– Sasha
Jan 27 at 13:50












$begingroup$
@AsafShachar: Thanks for correction!
$endgroup$
– Sasha
Jan 27 at 14:53




$begingroup$
@AsafShachar: Thanks for correction!
$endgroup$
– Sasha
Jan 27 at 14:53












$begingroup$
If $k$ is even, don't we have to be careful with the choice of the sign of $sigma_d$? How do you know that you can pick the positive? Respectively, that you can take the kth root of the expression?
$endgroup$
– Severin Schraven
Jan 27 at 14:57




$begingroup$
If $k$ is even, don't we have to be careful with the choice of the sign of $sigma_d$? How do you know that you can pick the positive? Respectively, that you can take the kth root of the expression?
$endgroup$
– Severin Schraven
Jan 27 at 14:57




1




1




$begingroup$
@SeverinSchraven I will just note that when you work over the complex numbers, you don't really have a problem: Instead of possible non-existence of roots (in the real case), you now have too many of them. However, it does not matter "which one you choose", since choosing a different $k$-th root only amounts to multiplying all the $sigma_i$ by some specific $k$-th root of unity, which is the only ambiguity we have here. (This was to be expected in advance, as I will elaborate in the question).
$endgroup$
– Asaf Shachar
Jan 27 at 15:08






$begingroup$
@SeverinSchraven I will just note that when you work over the complex numbers, you don't really have a problem: Instead of possible non-existence of roots (in the real case), you now have too many of them. However, it does not matter "which one you choose", since choosing a different $k$-th root only amounts to multiplying all the $sigma_i$ by some specific $k$-th root of unity, which is the only ambiguity we have here. (This was to be expected in advance, as I will elaborate in the question).
$endgroup$
– Asaf Shachar
Jan 27 at 15:08




















draft saved

draft discarded




















































Thanks for contributing an answer to Mathematics Stack Exchange!


  • Please be sure to answer the question. Provide details and share your research!

But avoid



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


Use MathJax to format equations. MathJax reference.


To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3089508%2fcharacterising-minors-of-diagonal-matrices%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

MongoDB - Not Authorized To Execute Command

in spring boot 2.1 many test slices are not allowed anymore due to multiple @BootstrapWith

How to fix TextFormField cause rebuild widget in Flutter