What will be the form of the \$k^{th}\$ component of \$x^{(i)}\$?

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Discussion Overview

The discussion revolves around the form of the $k^{th}$ component of a sequence indexed by elements of $\mathbb{Z}_p$. Participants explore the implications of indexing and the nature of sequences in the context of p-adic numbers versus integers modulo p.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that each term of the sequence $x^{(i)}$ can be expressed as a sequence of its components, such as $x^{(1)} = (x^{(1)}_1, x^{(1)}_2, x^{(1)}_3, ..., x^{(1)}_k, ...)$.
  • Others question whether $\mathbb{Z}_p$ refers to p-adic numbers or integers modulo p, suggesting that if it refers to p-adic numbers, the sequence could be represented as $x^{(1)} = x^{(1)}_0 + x^{(1)}_1 p + x^{(1)}_2 p^2 + ...$.
  • A participant clarifies that any p-adic integer can be expressed in a series form, leading to the interpretation that the components $x^{(1)}_k$ correspond to the coefficients in this series.
  • There is a suggestion that the sequence of components could be intended, but it remains unclear whether the focus is on the sequence of coefficients or the terms of p-adic integers.
  • Another participant introduces a definition of $\mathbb{Z}_p$, raising questions about the properties of sequences within this context.

Areas of Agreement / Disagreement

Participants express differing views on the nature of $\mathbb{Z}_p$ and the interpretation of sequences, with no consensus reached on the exact form of the $k^{th}$ component or the implications of the definitions discussed.

Contextual Notes

There are unresolved questions regarding the assumptions about the nature of sequences in $\mathbb{Z}_p$, the indexing method, and the specific properties of the components involved.

evinda
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Hi! (Smile)

Suppose that we index the components of the elements of $\mathbb{Z}_p$ by subscripts.

Indexing the terms of the sequence by superscripts in parentheses$x^{(i)}$ is a term of the sequence, and $x^{(i)}_k$ its $k$-th component.
So, if we have a sequence in $\mathbb{Z}_p$, it will be like that, right?

$$x=(x^{(1)}, x^{(2)}, \dots, x^{(k)}, \dotsc)$$

What will be the form of the $k^{th}$ component of $x^{(i)}$ ? (Thinking)
 
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evinda said:
Hi! (Smile)

Suppose that we index the components of the elements of $\mathbb{Z}_p$ by subscripts.

Indexing the terms of the sequence by superscripts in parentheses$x^{(i)}$ is a term of the sequence, and $x^{(i)}_k$ its $k$-th component.
So, if we have a sequence in $\mathbb{Z}_p$, it will be like that, right?

$$x=(x^{(1)}, x^{(2)}, \dots, x^{(k)}, \dotsc)$$

What will be the form of the $k^{th}$ component of $x^{(i)}$ ? (Thinking)

Hey! :o

I think it will be like:
$$x^{(1)} = (x^{(1)}_1, x^{(1)}_2, x^{(1)}_3, ..., x^{(1)}_k, ...)$$
(Thinking)
 
I like Serena said:
Hey! :o
(Happy)

I like Serena said:
I think it will be like:
$$x^{(1)} = (x^{(1)}_1, x^{(1)}_2, x^{(1)}_3, ..., x^{(1)}_k, ...)$$
(Thinking)

So does this mean that each term of the sequence will be a sequence? (Thinking)
 
evinda said:
So does this mean that each term of the sequence will be a sequence? (Thinking)

What is $\mathbb Z_p$?

Are those p-adic numbers or integers modulo p? (Wondering)

If they are p-adic numbers, then the sequence is probably as you thought, and
$$x^{(1)} = x^{(1)}_0 + x^{(1)}_1 p + x^{(1)}_2 p^2 + ...$$
(Thinking)
 
I like Serena said:
What is $\mathbb Z_p$?

Are those p-adic numbers or integers modulo p? (Wondering)

It is the set of integer p-adics.. (Nod)

I like Serena said:
If they are p-adic numbers, then the sequence is probably as you thought, and
$$x^{(1)} = x^{(1)}_0 + x^{(1)}_1 p + x^{(1)}_2 p^2 + ...$$
(Thinking)

Could you explain me how we conclude that $x^{(1)} = x^{(1)}_0 + x^{(1)}_1 p + x^{(1)}_2 p^2 + ...$ ? (Thinking)
 
evinda said:
It is the set of integer p-adics.. (Nod)

Could you explain me how we conclude that $x^{(1)} = x^{(1)}_0 + x^{(1)}_1 p + x^{(1)}_2 p^2 + ...$ ? (Thinking)

Let's take a closer look at your statements. (Thinking)

evinda said:
Suppose that we index the components of the elements of $\mathbb{Z}_p$ by subscripts.

Any p-adic integer $r \in \mathbb{Z}_p$ can be written as:
$$r = \sum_{i=m}^\infty a_i p^i$$
where $m \in \mathbb Z$ and $a_i \in \{0, ..., p-1\}$.

I'm interpreting your statement as saying that those components are the $a_i$ values. (Thinking)

Indexing the terms of the sequence by superscripts in parentheses

Now it seems some kind of sequence is introduced.
However, it is not clear if:
  1. the sequence of $a_i$ is intended,
  2. or the sequence of terms $a_i p^i$,
  3. or if this is about some sequence of p-adic integers.

Can you clarify? (Wondering)
$x^{(i)}$ is a term of the sequence, and $x^{(i)}_k$ its $k$-th component.

From this statement it seems that a sequence of p-adic integers is intended.
If so, then that would mean that $x^{(i)} \in \mathbb Z_p$.

Then $x$ would be a sequence of elements in $\mathbb Z_p$, and your next statement would be correct. (Nod)

So, if we have a sequence in $\mathbb{Z}_p$, it will be like that, right?

$$x=(x^{(1)}, x^{(2)}, \dots, x^{(k)}, \dotsc)$$

What will be the form of the $k^{th}$ component of $x^{(i)}$ ? (Thinking)

Since $x^{(1)} \in \mathbb Z_p$, we can write it as:
$$x^{(1)} = \sum_{k=m}^\infty x^{(1)}_k p^k$$

So there!
If my assumptions are correct, the $k^{th}$ component of $x^{(i)}$ is the coefficient of the corresponding $p^k$. (Wasntme)
 
I like Serena said:
Let's take a closer look at your statements. (Thinking)
Any p-adic integer $r \in \mathbb{Z}_p$ can be written as:
$$r = \sum_{i=m}^\infty a_i p^i$$
where $m \in \mathbb Z$ and $a_i \in \{0, ..., p-1\}$.

I'm interpreting your statement as saying that those components are the $a_i$ values. (Thinking)
Now it seems some kind of sequence is introduced.
However, it is not clear if:
  1. the sequence of $a_i$ is intended,
  2. or the sequence of terms $a_i p^i$,
  3. or if this is about some sequence of p-adic integers.

Can you clarify? (Wondering)

From this statement it seems that a sequence of p-adic integers is intended.
If so, then that would mean that $x^{(i)} \in \mathbb Z_p$.

Then $x$ would be a sequence of elements in $\mathbb Z_p$, and your next statement would be correct. (Nod)Since $x^{(1)} \in \mathbb Z_p$, we can write it as:
$$x^{(1)} = \sum_{k=m}^\infty x^{(1)}_k p^k$$

So there!
If my assumptions are correct, the $k^{th}$ component of $x^{(i)}$ is the coefficient of the corresponding $p^k$. (Wasntme)

I think that the following definition of $\mathbb{Z}_p$ is used:

$$\mathbb{Z}_p=\{ (\overline{x_k}) \in \prod_{k=0}^{\infty} \mathbb{Z}/p^{k+1}\mathbb{Z}| x_{k+1} \equiv x_k \mod{p^{k+1}}\}$$

So, does this mean that if $x=(x^{(1)}, x^{(2)}, \dots, x^{(k)}, \dots)$ and $x \in \mathbb{Z}_p$, then $x$ is a sequence of element of $\mathbb{Z}_p$ and the elements of the sequence $\in \mathbb{Z}/p^{k+1}$ and satisfy the property $x_{k+1} \equiv x_k \mod{p^{k+1}}$ ? (Thinking)
 

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