unknown sequences with sum of $e$ [closed]
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Starting with an transcendental number like $e$, it is known that we can write it as a sum of infinitely many rational numbers of the form :
$e= sum limits _{n=0}^{infty }{dfrac {1}{n!}}={frac {1}{1}}+{frac {1}{1}}+{frac {1}{1cdot 2}}+{frac {1}{1cdot 2cdot 3}}+cdots $
we can see in this form each element here is defined and is related to other elements by a known order.
a question comes to mind here about existance of a sequence of positive rational numbers ${omega _n}subsetmathbb{Q}^+$ satisfying conditions below:
- $ e= sum limits _{n=1}^{infty }omega_n$
- each element $omega_i$ is not predefined (means it is unknown to us, we just know it is positive rational number).
- there be no known order or trend (except the well ordering assortment) between elements of the sequence ${omega _n}$ (means there is no defined relation like $sim$ between elements of any subset of ${omega _n}$).
there be no defined algorithm by which ${omega _n}$ be constructed from ${dfrac {1}{n!}}$ or any other known sequence with sum of $e$.
note: here conditions 3 and 4 may correlate eachother but I mentioned both for more accurate explanation.
It seems that we should investigate first whether this question is undecidable or not under the ZFC axiomatic system but I don't know how?
the question can be extended and ask about the cardinality of such those sequences as subsets of $mathbb{Q}$ if there exist some of it. also what can we say about other irrational numbers except e?
sequences-and-series transcendental-numbers
closed as unclear what you're asking by Winther, Andrés E. Caicedo, Shailesh, user10354138, Parcly Taxel Nov 18 at 2:54
Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
add a comment |
up vote
-2
down vote
favorite
Starting with an transcendental number like $e$, it is known that we can write it as a sum of infinitely many rational numbers of the form :
$e= sum limits _{n=0}^{infty }{dfrac {1}{n!}}={frac {1}{1}}+{frac {1}{1}}+{frac {1}{1cdot 2}}+{frac {1}{1cdot 2cdot 3}}+cdots $
we can see in this form each element here is defined and is related to other elements by a known order.
a question comes to mind here about existance of a sequence of positive rational numbers ${omega _n}subsetmathbb{Q}^+$ satisfying conditions below:
- $ e= sum limits _{n=1}^{infty }omega_n$
- each element $omega_i$ is not predefined (means it is unknown to us, we just know it is positive rational number).
- there be no known order or trend (except the well ordering assortment) between elements of the sequence ${omega _n}$ (means there is no defined relation like $sim$ between elements of any subset of ${omega _n}$).
there be no defined algorithm by which ${omega _n}$ be constructed from ${dfrac {1}{n!}}$ or any other known sequence with sum of $e$.
note: here conditions 3 and 4 may correlate eachother but I mentioned both for more accurate explanation.
It seems that we should investigate first whether this question is undecidable or not under the ZFC axiomatic system but I don't know how?
the question can be extended and ask about the cardinality of such those sequences as subsets of $mathbb{Q}$ if there exist some of it. also what can we say about other irrational numbers except e?
sequences-and-series transcendental-numbers
closed as unclear what you're asking by Winther, Andrés E. Caicedo, Shailesh, user10354138, Parcly Taxel Nov 18 at 2:54
Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
1
Weird question. There are infinitely many ways of writing any positive number as a sum of positive rationals. You seem to be asking if there is some "hidden" way to do this that we cannot know anything about?
– Winther
Nov 17 at 13:40
@Winther yeap it's strange. It specifically search for a transparent border of what is known to us and what is hidden
– MasM
Nov 17 at 13:58
Ok, but the question as phrased just don't make much sense to me.
– Winther
Nov 17 at 14:30
@Winther so you're free to suggest an edit and rephrase the question in order to make it sense and not to be closed.
– MasM
Nov 23 at 1:33
1
I don't know how to suggest an edit as I don't understand what you mean. What precisely does "is not predefined / unknown to us" mean here? "there be no known order or trend" What does trend mean here? Note that there will always be the case that $omega_nto 0$ (to have a convergent series). Does this count as a 'trend'? What does "no defined algorithm" mean? Why couldn't I take $omega_n$ adding $1/n!$ and subtracting $omega_n$? (yes it's silly, but this is just to illustrate a point) Everything is just so fuzzy here.
– Winther
Nov 23 at 1:48
add a comment |
up vote
-2
down vote
favorite
up vote
-2
down vote
favorite
Starting with an transcendental number like $e$, it is known that we can write it as a sum of infinitely many rational numbers of the form :
$e= sum limits _{n=0}^{infty }{dfrac {1}{n!}}={frac {1}{1}}+{frac {1}{1}}+{frac {1}{1cdot 2}}+{frac {1}{1cdot 2cdot 3}}+cdots $
we can see in this form each element here is defined and is related to other elements by a known order.
a question comes to mind here about existance of a sequence of positive rational numbers ${omega _n}subsetmathbb{Q}^+$ satisfying conditions below:
- $ e= sum limits _{n=1}^{infty }omega_n$
- each element $omega_i$ is not predefined (means it is unknown to us, we just know it is positive rational number).
- there be no known order or trend (except the well ordering assortment) between elements of the sequence ${omega _n}$ (means there is no defined relation like $sim$ between elements of any subset of ${omega _n}$).
there be no defined algorithm by which ${omega _n}$ be constructed from ${dfrac {1}{n!}}$ or any other known sequence with sum of $e$.
note: here conditions 3 and 4 may correlate eachother but I mentioned both for more accurate explanation.
It seems that we should investigate first whether this question is undecidable or not under the ZFC axiomatic system but I don't know how?
the question can be extended and ask about the cardinality of such those sequences as subsets of $mathbb{Q}$ if there exist some of it. also what can we say about other irrational numbers except e?
sequences-and-series transcendental-numbers
Starting with an transcendental number like $e$, it is known that we can write it as a sum of infinitely many rational numbers of the form :
$e= sum limits _{n=0}^{infty }{dfrac {1}{n!}}={frac {1}{1}}+{frac {1}{1}}+{frac {1}{1cdot 2}}+{frac {1}{1cdot 2cdot 3}}+cdots $
we can see in this form each element here is defined and is related to other elements by a known order.
a question comes to mind here about existance of a sequence of positive rational numbers ${omega _n}subsetmathbb{Q}^+$ satisfying conditions below:
- $ e= sum limits _{n=1}^{infty }omega_n$
- each element $omega_i$ is not predefined (means it is unknown to us, we just know it is positive rational number).
- there be no known order or trend (except the well ordering assortment) between elements of the sequence ${omega _n}$ (means there is no defined relation like $sim$ between elements of any subset of ${omega _n}$).
there be no defined algorithm by which ${omega _n}$ be constructed from ${dfrac {1}{n!}}$ or any other known sequence with sum of $e$.
note: here conditions 3 and 4 may correlate eachother but I mentioned both for more accurate explanation.
It seems that we should investigate first whether this question is undecidable or not under the ZFC axiomatic system but I don't know how?
the question can be extended and ask about the cardinality of such those sequences as subsets of $mathbb{Q}$ if there exist some of it. also what can we say about other irrational numbers except e?
sequences-and-series transcendental-numbers
sequences-and-series transcendental-numbers
edited Nov 17 at 21:54
Andrés E. Caicedo
64.3k8157244
64.3k8157244
asked Nov 17 at 12:45
MasM
8411
8411
closed as unclear what you're asking by Winther, Andrés E. Caicedo, Shailesh, user10354138, Parcly Taxel Nov 18 at 2:54
Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
closed as unclear what you're asking by Winther, Andrés E. Caicedo, Shailesh, user10354138, Parcly Taxel Nov 18 at 2:54
Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
1
Weird question. There are infinitely many ways of writing any positive number as a sum of positive rationals. You seem to be asking if there is some "hidden" way to do this that we cannot know anything about?
– Winther
Nov 17 at 13:40
@Winther yeap it's strange. It specifically search for a transparent border of what is known to us and what is hidden
– MasM
Nov 17 at 13:58
Ok, but the question as phrased just don't make much sense to me.
– Winther
Nov 17 at 14:30
@Winther so you're free to suggest an edit and rephrase the question in order to make it sense and not to be closed.
– MasM
Nov 23 at 1:33
1
I don't know how to suggest an edit as I don't understand what you mean. What precisely does "is not predefined / unknown to us" mean here? "there be no known order or trend" What does trend mean here? Note that there will always be the case that $omega_nto 0$ (to have a convergent series). Does this count as a 'trend'? What does "no defined algorithm" mean? Why couldn't I take $omega_n$ adding $1/n!$ and subtracting $omega_n$? (yes it's silly, but this is just to illustrate a point) Everything is just so fuzzy here.
– Winther
Nov 23 at 1:48
add a comment |
1
Weird question. There are infinitely many ways of writing any positive number as a sum of positive rationals. You seem to be asking if there is some "hidden" way to do this that we cannot know anything about?
– Winther
Nov 17 at 13:40
@Winther yeap it's strange. It specifically search for a transparent border of what is known to us and what is hidden
– MasM
Nov 17 at 13:58
Ok, but the question as phrased just don't make much sense to me.
– Winther
Nov 17 at 14:30
@Winther so you're free to suggest an edit and rephrase the question in order to make it sense and not to be closed.
– MasM
Nov 23 at 1:33
1
I don't know how to suggest an edit as I don't understand what you mean. What precisely does "is not predefined / unknown to us" mean here? "there be no known order or trend" What does trend mean here? Note that there will always be the case that $omega_nto 0$ (to have a convergent series). Does this count as a 'trend'? What does "no defined algorithm" mean? Why couldn't I take $omega_n$ adding $1/n!$ and subtracting $omega_n$? (yes it's silly, but this is just to illustrate a point) Everything is just so fuzzy here.
– Winther
Nov 23 at 1:48
1
1
Weird question. There are infinitely many ways of writing any positive number as a sum of positive rationals. You seem to be asking if there is some "hidden" way to do this that we cannot know anything about?
– Winther
Nov 17 at 13:40
Weird question. There are infinitely many ways of writing any positive number as a sum of positive rationals. You seem to be asking if there is some "hidden" way to do this that we cannot know anything about?
– Winther
Nov 17 at 13:40
@Winther yeap it's strange. It specifically search for a transparent border of what is known to us and what is hidden
– MasM
Nov 17 at 13:58
@Winther yeap it's strange. It specifically search for a transparent border of what is known to us and what is hidden
– MasM
Nov 17 at 13:58
Ok, but the question as phrased just don't make much sense to me.
– Winther
Nov 17 at 14:30
Ok, but the question as phrased just don't make much sense to me.
– Winther
Nov 17 at 14:30
@Winther so you're free to suggest an edit and rephrase the question in order to make it sense and not to be closed.
– MasM
Nov 23 at 1:33
@Winther so you're free to suggest an edit and rephrase the question in order to make it sense and not to be closed.
– MasM
Nov 23 at 1:33
1
1
I don't know how to suggest an edit as I don't understand what you mean. What precisely does "is not predefined / unknown to us" mean here? "there be no known order or trend" What does trend mean here? Note that there will always be the case that $omega_nto 0$ (to have a convergent series). Does this count as a 'trend'? What does "no defined algorithm" mean? Why couldn't I take $omega_n$ adding $1/n!$ and subtracting $omega_n$? (yes it's silly, but this is just to illustrate a point) Everything is just so fuzzy here.
– Winther
Nov 23 at 1:48
I don't know how to suggest an edit as I don't understand what you mean. What precisely does "is not predefined / unknown to us" mean here? "there be no known order or trend" What does trend mean here? Note that there will always be the case that $omega_nto 0$ (to have a convergent series). Does this count as a 'trend'? What does "no defined algorithm" mean? Why couldn't I take $omega_n$ adding $1/n!$ and subtracting $omega_n$? (yes it's silly, but this is just to illustrate a point) Everything is just so fuzzy here.
– Winther
Nov 23 at 1:48
add a comment |
2 Answers
2
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1
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Edit: The question has been edited since I posted this answer to remove any reference to cardinality. Hopefully this answer is still of some use and/or interest.
What it looks like you're asking for is simply the cardinality of the set of sequences ${ omega_n }_{n in mathbb{N}} subseteq mathbb{Q}^+$ such that $sum_{n in mathbb{N}} omega_n = e$. Your conditions (2), (3) and (4) are wrapped up in this since we haven't specified any additional information about the sequences ${ omega_n }_{n in mathbb{N}}$ other than that they sum to $e$.
This set has cardinality $2^{aleph_0}$. To see this, note that there are $2^{aleph_0}$-many real numbers $a$ such that $0<a<e$. The numbers $a$ and $e-a$ both have sequences of positive rationals whose sum converges to them—say ${alpha_n}_{n in mathbb{N}} subseteq mathbb{Q}^+$ and ${beta_n}_{n in mathbb{N}} subseteq mathbb{Q}^+$ satisfy $sum_n alpha_n = a$ and $sum_n beta_n = e-a$. (For example, you could take $alpha_n$ to be the truncation of the decimal expansion of $a$ after its $n^{text{th}}$ digit, and likewise for $beta_n$.)
The sequence ${omega_n}_{n in mathbb{N}}$ defined by $omega_{2n}=alpha_n$ and $omega_{2n+1} = beta_n$ then satisfies $sum_n omega_n = e$, and the function $a mapsto {omega_n}_{n in mathbb{N}}$ is injective, so that your set has cardinality $ge 2^{aleph_0}$. It also has cardinality $le 2^{aleph_0}$ since it is a set of subsets of $mathbb{Q}$, which has cardinality $aleph_0$.
This argument applies just as well with $e$ replaced by any positive real number, transcendental or otherwise.
I have some serious problem with this answer specially about using$alpha ,beta$ in defining $omega_n$ ,it negates the condition 3 clearly
– MasM
Nov 17 at 13:53
I had a hunch you'd say that, in which case I don't think I can be of any help—your condition (3) is not mathematically precise, meaning you can't reason about it using mathematics. In order to make it precise, you need to specify (mathematically) what you mean by 'there is no known order or trend'—if you do that, then I might be able to help you more.
– Clive Newstead
Nov 17 at 14:31
To clarify a point: given an arbitrary sequence ${ omega_n }$ in your set (i.e. we know nothing about it other than that it is a sequence of positive rationals converging to $e$), we can't say anything about the 'order or trend' of the elements $omega_n$. But this is different from saying that for every sequence ${ omega_n }$ in your set that we can't reason about the order or trend of its elements. There seems to be confusion between reasoning about an arbitrary ('generic') element of a set, versus reasoning about a particular element of a set.
– Clive Newstead
Nov 17 at 14:33
I've explained the condition 3:"means there is no defined relation between elements of any subset of {ωn}" , if we find some of sequence satisfying the condition by your viewpoint we deduce if we choose an arbitrary one from them then it would be the same as we pick a particular one if we can define that particular
– MasM
Nov 17 at 19:21
2
What does 'no defined relation' mean? Every set has relations on it. You seem to not understand the difference between 'arbitrary' and 'particular'. I'm sorry, but your question just doesn't make mathematical sense, so I can't answer it. (I suspect this is why so many people have down-voted it, but I thought I'd at least explain why it can't be answered.)
– Clive Newstead
Nov 17 at 19:29
|
show 1 more comment
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0
down vote
Just an idea. For $n = 0, 1, 2, ldots$ define $e_n = 1/0! + 1/1! + cdots + 1/n!$. Define $s_0 = 0$. For $n = 1, 2, ldots$ choose randomly a rational $s_n$ such that $e_{n-1} < s_n < e_n$, and then define
$omega_n = s_n - s_{n - 1}$. Then $omega_1 + omega_2 + cdots = e$. We could get a computer to choose the $s_n$ without telling us what they are. Not sure if this is the sort of thing you had in mind. Of course, making infinitely many random choices is a bit problematic.
Nice argument but same as previous answer it also negates the condition 3 as we have a knowledge that $omega_n = s_n -s_{n-1 }<e_n-e_{n-2} ={1/n!}+{1/(n-1)! }$
– MasM
Nov 17 at 19:00
add a comment |
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
1
down vote
Edit: The question has been edited since I posted this answer to remove any reference to cardinality. Hopefully this answer is still of some use and/or interest.
What it looks like you're asking for is simply the cardinality of the set of sequences ${ omega_n }_{n in mathbb{N}} subseteq mathbb{Q}^+$ such that $sum_{n in mathbb{N}} omega_n = e$. Your conditions (2), (3) and (4) are wrapped up in this since we haven't specified any additional information about the sequences ${ omega_n }_{n in mathbb{N}}$ other than that they sum to $e$.
This set has cardinality $2^{aleph_0}$. To see this, note that there are $2^{aleph_0}$-many real numbers $a$ such that $0<a<e$. The numbers $a$ and $e-a$ both have sequences of positive rationals whose sum converges to them—say ${alpha_n}_{n in mathbb{N}} subseteq mathbb{Q}^+$ and ${beta_n}_{n in mathbb{N}} subseteq mathbb{Q}^+$ satisfy $sum_n alpha_n = a$ and $sum_n beta_n = e-a$. (For example, you could take $alpha_n$ to be the truncation of the decimal expansion of $a$ after its $n^{text{th}}$ digit, and likewise for $beta_n$.)
The sequence ${omega_n}_{n in mathbb{N}}$ defined by $omega_{2n}=alpha_n$ and $omega_{2n+1} = beta_n$ then satisfies $sum_n omega_n = e$, and the function $a mapsto {omega_n}_{n in mathbb{N}}$ is injective, so that your set has cardinality $ge 2^{aleph_0}$. It also has cardinality $le 2^{aleph_0}$ since it is a set of subsets of $mathbb{Q}$, which has cardinality $aleph_0$.
This argument applies just as well with $e$ replaced by any positive real number, transcendental or otherwise.
I have some serious problem with this answer specially about using$alpha ,beta$ in defining $omega_n$ ,it negates the condition 3 clearly
– MasM
Nov 17 at 13:53
I had a hunch you'd say that, in which case I don't think I can be of any help—your condition (3) is not mathematically precise, meaning you can't reason about it using mathematics. In order to make it precise, you need to specify (mathematically) what you mean by 'there is no known order or trend'—if you do that, then I might be able to help you more.
– Clive Newstead
Nov 17 at 14:31
To clarify a point: given an arbitrary sequence ${ omega_n }$ in your set (i.e. we know nothing about it other than that it is a sequence of positive rationals converging to $e$), we can't say anything about the 'order or trend' of the elements $omega_n$. But this is different from saying that for every sequence ${ omega_n }$ in your set that we can't reason about the order or trend of its elements. There seems to be confusion between reasoning about an arbitrary ('generic') element of a set, versus reasoning about a particular element of a set.
– Clive Newstead
Nov 17 at 14:33
I've explained the condition 3:"means there is no defined relation between elements of any subset of {ωn}" , if we find some of sequence satisfying the condition by your viewpoint we deduce if we choose an arbitrary one from them then it would be the same as we pick a particular one if we can define that particular
– MasM
Nov 17 at 19:21
2
What does 'no defined relation' mean? Every set has relations on it. You seem to not understand the difference between 'arbitrary' and 'particular'. I'm sorry, but your question just doesn't make mathematical sense, so I can't answer it. (I suspect this is why so many people have down-voted it, but I thought I'd at least explain why it can't be answered.)
– Clive Newstead
Nov 17 at 19:29
|
show 1 more comment
up vote
1
down vote
Edit: The question has been edited since I posted this answer to remove any reference to cardinality. Hopefully this answer is still of some use and/or interest.
What it looks like you're asking for is simply the cardinality of the set of sequences ${ omega_n }_{n in mathbb{N}} subseteq mathbb{Q}^+$ such that $sum_{n in mathbb{N}} omega_n = e$. Your conditions (2), (3) and (4) are wrapped up in this since we haven't specified any additional information about the sequences ${ omega_n }_{n in mathbb{N}}$ other than that they sum to $e$.
This set has cardinality $2^{aleph_0}$. To see this, note that there are $2^{aleph_0}$-many real numbers $a$ such that $0<a<e$. The numbers $a$ and $e-a$ both have sequences of positive rationals whose sum converges to them—say ${alpha_n}_{n in mathbb{N}} subseteq mathbb{Q}^+$ and ${beta_n}_{n in mathbb{N}} subseteq mathbb{Q}^+$ satisfy $sum_n alpha_n = a$ and $sum_n beta_n = e-a$. (For example, you could take $alpha_n$ to be the truncation of the decimal expansion of $a$ after its $n^{text{th}}$ digit, and likewise for $beta_n$.)
The sequence ${omega_n}_{n in mathbb{N}}$ defined by $omega_{2n}=alpha_n$ and $omega_{2n+1} = beta_n$ then satisfies $sum_n omega_n = e$, and the function $a mapsto {omega_n}_{n in mathbb{N}}$ is injective, so that your set has cardinality $ge 2^{aleph_0}$. It also has cardinality $le 2^{aleph_0}$ since it is a set of subsets of $mathbb{Q}$, which has cardinality $aleph_0$.
This argument applies just as well with $e$ replaced by any positive real number, transcendental or otherwise.
I have some serious problem with this answer specially about using$alpha ,beta$ in defining $omega_n$ ,it negates the condition 3 clearly
– MasM
Nov 17 at 13:53
I had a hunch you'd say that, in which case I don't think I can be of any help—your condition (3) is not mathematically precise, meaning you can't reason about it using mathematics. In order to make it precise, you need to specify (mathematically) what you mean by 'there is no known order or trend'—if you do that, then I might be able to help you more.
– Clive Newstead
Nov 17 at 14:31
To clarify a point: given an arbitrary sequence ${ omega_n }$ in your set (i.e. we know nothing about it other than that it is a sequence of positive rationals converging to $e$), we can't say anything about the 'order or trend' of the elements $omega_n$. But this is different from saying that for every sequence ${ omega_n }$ in your set that we can't reason about the order or trend of its elements. There seems to be confusion between reasoning about an arbitrary ('generic') element of a set, versus reasoning about a particular element of a set.
– Clive Newstead
Nov 17 at 14:33
I've explained the condition 3:"means there is no defined relation between elements of any subset of {ωn}" , if we find some of sequence satisfying the condition by your viewpoint we deduce if we choose an arbitrary one from them then it would be the same as we pick a particular one if we can define that particular
– MasM
Nov 17 at 19:21
2
What does 'no defined relation' mean? Every set has relations on it. You seem to not understand the difference between 'arbitrary' and 'particular'. I'm sorry, but your question just doesn't make mathematical sense, so I can't answer it. (I suspect this is why so many people have down-voted it, but I thought I'd at least explain why it can't be answered.)
– Clive Newstead
Nov 17 at 19:29
|
show 1 more comment
up vote
1
down vote
up vote
1
down vote
Edit: The question has been edited since I posted this answer to remove any reference to cardinality. Hopefully this answer is still of some use and/or interest.
What it looks like you're asking for is simply the cardinality of the set of sequences ${ omega_n }_{n in mathbb{N}} subseteq mathbb{Q}^+$ such that $sum_{n in mathbb{N}} omega_n = e$. Your conditions (2), (3) and (4) are wrapped up in this since we haven't specified any additional information about the sequences ${ omega_n }_{n in mathbb{N}}$ other than that they sum to $e$.
This set has cardinality $2^{aleph_0}$. To see this, note that there are $2^{aleph_0}$-many real numbers $a$ such that $0<a<e$. The numbers $a$ and $e-a$ both have sequences of positive rationals whose sum converges to them—say ${alpha_n}_{n in mathbb{N}} subseteq mathbb{Q}^+$ and ${beta_n}_{n in mathbb{N}} subseteq mathbb{Q}^+$ satisfy $sum_n alpha_n = a$ and $sum_n beta_n = e-a$. (For example, you could take $alpha_n$ to be the truncation of the decimal expansion of $a$ after its $n^{text{th}}$ digit, and likewise for $beta_n$.)
The sequence ${omega_n}_{n in mathbb{N}}$ defined by $omega_{2n}=alpha_n$ and $omega_{2n+1} = beta_n$ then satisfies $sum_n omega_n = e$, and the function $a mapsto {omega_n}_{n in mathbb{N}}$ is injective, so that your set has cardinality $ge 2^{aleph_0}$. It also has cardinality $le 2^{aleph_0}$ since it is a set of subsets of $mathbb{Q}$, which has cardinality $aleph_0$.
This argument applies just as well with $e$ replaced by any positive real number, transcendental or otherwise.
Edit: The question has been edited since I posted this answer to remove any reference to cardinality. Hopefully this answer is still of some use and/or interest.
What it looks like you're asking for is simply the cardinality of the set of sequences ${ omega_n }_{n in mathbb{N}} subseteq mathbb{Q}^+$ such that $sum_{n in mathbb{N}} omega_n = e$. Your conditions (2), (3) and (4) are wrapped up in this since we haven't specified any additional information about the sequences ${ omega_n }_{n in mathbb{N}}$ other than that they sum to $e$.
This set has cardinality $2^{aleph_0}$. To see this, note that there are $2^{aleph_0}$-many real numbers $a$ such that $0<a<e$. The numbers $a$ and $e-a$ both have sequences of positive rationals whose sum converges to them—say ${alpha_n}_{n in mathbb{N}} subseteq mathbb{Q}^+$ and ${beta_n}_{n in mathbb{N}} subseteq mathbb{Q}^+$ satisfy $sum_n alpha_n = a$ and $sum_n beta_n = e-a$. (For example, you could take $alpha_n$ to be the truncation of the decimal expansion of $a$ after its $n^{text{th}}$ digit, and likewise for $beta_n$.)
The sequence ${omega_n}_{n in mathbb{N}}$ defined by $omega_{2n}=alpha_n$ and $omega_{2n+1} = beta_n$ then satisfies $sum_n omega_n = e$, and the function $a mapsto {omega_n}_{n in mathbb{N}}$ is injective, so that your set has cardinality $ge 2^{aleph_0}$. It also has cardinality $le 2^{aleph_0}$ since it is a set of subsets of $mathbb{Q}$, which has cardinality $aleph_0$.
This argument applies just as well with $e$ replaced by any positive real number, transcendental or otherwise.
answered Nov 17 at 13:38
Clive Newstead
49.5k472132
49.5k472132
I have some serious problem with this answer specially about using$alpha ,beta$ in defining $omega_n$ ,it negates the condition 3 clearly
– MasM
Nov 17 at 13:53
I had a hunch you'd say that, in which case I don't think I can be of any help—your condition (3) is not mathematically precise, meaning you can't reason about it using mathematics. In order to make it precise, you need to specify (mathematically) what you mean by 'there is no known order or trend'—if you do that, then I might be able to help you more.
– Clive Newstead
Nov 17 at 14:31
To clarify a point: given an arbitrary sequence ${ omega_n }$ in your set (i.e. we know nothing about it other than that it is a sequence of positive rationals converging to $e$), we can't say anything about the 'order or trend' of the elements $omega_n$. But this is different from saying that for every sequence ${ omega_n }$ in your set that we can't reason about the order or trend of its elements. There seems to be confusion between reasoning about an arbitrary ('generic') element of a set, versus reasoning about a particular element of a set.
– Clive Newstead
Nov 17 at 14:33
I've explained the condition 3:"means there is no defined relation between elements of any subset of {ωn}" , if we find some of sequence satisfying the condition by your viewpoint we deduce if we choose an arbitrary one from them then it would be the same as we pick a particular one if we can define that particular
– MasM
Nov 17 at 19:21
2
What does 'no defined relation' mean? Every set has relations on it. You seem to not understand the difference between 'arbitrary' and 'particular'. I'm sorry, but your question just doesn't make mathematical sense, so I can't answer it. (I suspect this is why so many people have down-voted it, but I thought I'd at least explain why it can't be answered.)
– Clive Newstead
Nov 17 at 19:29
|
show 1 more comment
I have some serious problem with this answer specially about using$alpha ,beta$ in defining $omega_n$ ,it negates the condition 3 clearly
– MasM
Nov 17 at 13:53
I had a hunch you'd say that, in which case I don't think I can be of any help—your condition (3) is not mathematically precise, meaning you can't reason about it using mathematics. In order to make it precise, you need to specify (mathematically) what you mean by 'there is no known order or trend'—if you do that, then I might be able to help you more.
– Clive Newstead
Nov 17 at 14:31
To clarify a point: given an arbitrary sequence ${ omega_n }$ in your set (i.e. we know nothing about it other than that it is a sequence of positive rationals converging to $e$), we can't say anything about the 'order or trend' of the elements $omega_n$. But this is different from saying that for every sequence ${ omega_n }$ in your set that we can't reason about the order or trend of its elements. There seems to be confusion between reasoning about an arbitrary ('generic') element of a set, versus reasoning about a particular element of a set.
– Clive Newstead
Nov 17 at 14:33
I've explained the condition 3:"means there is no defined relation between elements of any subset of {ωn}" , if we find some of sequence satisfying the condition by your viewpoint we deduce if we choose an arbitrary one from them then it would be the same as we pick a particular one if we can define that particular
– MasM
Nov 17 at 19:21
2
What does 'no defined relation' mean? Every set has relations on it. You seem to not understand the difference between 'arbitrary' and 'particular'. I'm sorry, but your question just doesn't make mathematical sense, so I can't answer it. (I suspect this is why so many people have down-voted it, but I thought I'd at least explain why it can't be answered.)
– Clive Newstead
Nov 17 at 19:29
I have some serious problem with this answer specially about using$alpha ,beta$ in defining $omega_n$ ,it negates the condition 3 clearly
– MasM
Nov 17 at 13:53
I have some serious problem with this answer specially about using$alpha ,beta$ in defining $omega_n$ ,it negates the condition 3 clearly
– MasM
Nov 17 at 13:53
I had a hunch you'd say that, in which case I don't think I can be of any help—your condition (3) is not mathematically precise, meaning you can't reason about it using mathematics. In order to make it precise, you need to specify (mathematically) what you mean by 'there is no known order or trend'—if you do that, then I might be able to help you more.
– Clive Newstead
Nov 17 at 14:31
I had a hunch you'd say that, in which case I don't think I can be of any help—your condition (3) is not mathematically precise, meaning you can't reason about it using mathematics. In order to make it precise, you need to specify (mathematically) what you mean by 'there is no known order or trend'—if you do that, then I might be able to help you more.
– Clive Newstead
Nov 17 at 14:31
To clarify a point: given an arbitrary sequence ${ omega_n }$ in your set (i.e. we know nothing about it other than that it is a sequence of positive rationals converging to $e$), we can't say anything about the 'order or trend' of the elements $omega_n$. But this is different from saying that for every sequence ${ omega_n }$ in your set that we can't reason about the order or trend of its elements. There seems to be confusion between reasoning about an arbitrary ('generic') element of a set, versus reasoning about a particular element of a set.
– Clive Newstead
Nov 17 at 14:33
To clarify a point: given an arbitrary sequence ${ omega_n }$ in your set (i.e. we know nothing about it other than that it is a sequence of positive rationals converging to $e$), we can't say anything about the 'order or trend' of the elements $omega_n$. But this is different from saying that for every sequence ${ omega_n }$ in your set that we can't reason about the order or trend of its elements. There seems to be confusion between reasoning about an arbitrary ('generic') element of a set, versus reasoning about a particular element of a set.
– Clive Newstead
Nov 17 at 14:33
I've explained the condition 3:"means there is no defined relation between elements of any subset of {ωn}" , if we find some of sequence satisfying the condition by your viewpoint we deduce if we choose an arbitrary one from them then it would be the same as we pick a particular one if we can define that particular
– MasM
Nov 17 at 19:21
I've explained the condition 3:"means there is no defined relation between elements of any subset of {ωn}" , if we find some of sequence satisfying the condition by your viewpoint we deduce if we choose an arbitrary one from them then it would be the same as we pick a particular one if we can define that particular
– MasM
Nov 17 at 19:21
2
2
What does 'no defined relation' mean? Every set has relations on it. You seem to not understand the difference between 'arbitrary' and 'particular'. I'm sorry, but your question just doesn't make mathematical sense, so I can't answer it. (I suspect this is why so many people have down-voted it, but I thought I'd at least explain why it can't be answered.)
– Clive Newstead
Nov 17 at 19:29
What does 'no defined relation' mean? Every set has relations on it. You seem to not understand the difference between 'arbitrary' and 'particular'. I'm sorry, but your question just doesn't make mathematical sense, so I can't answer it. (I suspect this is why so many people have down-voted it, but I thought I'd at least explain why it can't be answered.)
– Clive Newstead
Nov 17 at 19:29
|
show 1 more comment
up vote
0
down vote
Just an idea. For $n = 0, 1, 2, ldots$ define $e_n = 1/0! + 1/1! + cdots + 1/n!$. Define $s_0 = 0$. For $n = 1, 2, ldots$ choose randomly a rational $s_n$ such that $e_{n-1} < s_n < e_n$, and then define
$omega_n = s_n - s_{n - 1}$. Then $omega_1 + omega_2 + cdots = e$. We could get a computer to choose the $s_n$ without telling us what they are. Not sure if this is the sort of thing you had in mind. Of course, making infinitely many random choices is a bit problematic.
Nice argument but same as previous answer it also negates the condition 3 as we have a knowledge that $omega_n = s_n -s_{n-1 }<e_n-e_{n-2} ={1/n!}+{1/(n-1)! }$
– MasM
Nov 17 at 19:00
add a comment |
up vote
0
down vote
Just an idea. For $n = 0, 1, 2, ldots$ define $e_n = 1/0! + 1/1! + cdots + 1/n!$. Define $s_0 = 0$. For $n = 1, 2, ldots$ choose randomly a rational $s_n$ such that $e_{n-1} < s_n < e_n$, and then define
$omega_n = s_n - s_{n - 1}$. Then $omega_1 + omega_2 + cdots = e$. We could get a computer to choose the $s_n$ without telling us what they are. Not sure if this is the sort of thing you had in mind. Of course, making infinitely many random choices is a bit problematic.
Nice argument but same as previous answer it also negates the condition 3 as we have a knowledge that $omega_n = s_n -s_{n-1 }<e_n-e_{n-2} ={1/n!}+{1/(n-1)! }$
– MasM
Nov 17 at 19:00
add a comment |
up vote
0
down vote
up vote
0
down vote
Just an idea. For $n = 0, 1, 2, ldots$ define $e_n = 1/0! + 1/1! + cdots + 1/n!$. Define $s_0 = 0$. For $n = 1, 2, ldots$ choose randomly a rational $s_n$ such that $e_{n-1} < s_n < e_n$, and then define
$omega_n = s_n - s_{n - 1}$. Then $omega_1 + omega_2 + cdots = e$. We could get a computer to choose the $s_n$ without telling us what they are. Not sure if this is the sort of thing you had in mind. Of course, making infinitely many random choices is a bit problematic.
Just an idea. For $n = 0, 1, 2, ldots$ define $e_n = 1/0! + 1/1! + cdots + 1/n!$. Define $s_0 = 0$. For $n = 1, 2, ldots$ choose randomly a rational $s_n$ such that $e_{n-1} < s_n < e_n$, and then define
$omega_n = s_n - s_{n - 1}$. Then $omega_1 + omega_2 + cdots = e$. We could get a computer to choose the $s_n$ without telling us what they are. Not sure if this is the sort of thing you had in mind. Of course, making infinitely many random choices is a bit problematic.
answered Nov 17 at 17:10
Michael Behrend
1,03736
1,03736
Nice argument but same as previous answer it also negates the condition 3 as we have a knowledge that $omega_n = s_n -s_{n-1 }<e_n-e_{n-2} ={1/n!}+{1/(n-1)! }$
– MasM
Nov 17 at 19:00
add a comment |
Nice argument but same as previous answer it also negates the condition 3 as we have a knowledge that $omega_n = s_n -s_{n-1 }<e_n-e_{n-2} ={1/n!}+{1/(n-1)! }$
– MasM
Nov 17 at 19:00
Nice argument but same as previous answer it also negates the condition 3 as we have a knowledge that $omega_n = s_n -s_{n-1 }<e_n-e_{n-2} ={1/n!}+{1/(n-1)! }$
– MasM
Nov 17 at 19:00
Nice argument but same as previous answer it also negates the condition 3 as we have a knowledge that $omega_n = s_n -s_{n-1 }<e_n-e_{n-2} ={1/n!}+{1/(n-1)! }$
– MasM
Nov 17 at 19:00
add a comment |
1
Weird question. There are infinitely many ways of writing any positive number as a sum of positive rationals. You seem to be asking if there is some "hidden" way to do this that we cannot know anything about?
– Winther
Nov 17 at 13:40
@Winther yeap it's strange. It specifically search for a transparent border of what is known to us and what is hidden
– MasM
Nov 17 at 13:58
Ok, but the question as phrased just don't make much sense to me.
– Winther
Nov 17 at 14:30
@Winther so you're free to suggest an edit and rephrase the question in order to make it sense and not to be closed.
– MasM
Nov 23 at 1:33
1
I don't know how to suggest an edit as I don't understand what you mean. What precisely does "is not predefined / unknown to us" mean here? "there be no known order or trend" What does trend mean here? Note that there will always be the case that $omega_nto 0$ (to have a convergent series). Does this count as a 'trend'? What does "no defined algorithm" mean? Why couldn't I take $omega_n$ adding $1/n!$ and subtracting $omega_n$? (yes it's silly, but this is just to illustrate a point) Everything is just so fuzzy here.
– Winther
Nov 23 at 1:48