Exponential sums and congruences

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    Exponential Sums
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Discussion Overview

The discussion revolves around the properties of exponential sums related to congruences, specifically focusing on the conjecture that relates the real part of an exponential sum to the number of solutions of a polynomial congruence. The scope includes mathematical reasoning and exploration of the implications of the conjecture.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents a conjecture that the real part of the exponential sum \( S = \sum_{n=1}^{N} e\left(\frac{f(n)}{p}\right) \) equals the number of solutions to the congruence \( f(x) \equiv 0 \mod(p) \) within the interval (1, N).
  • Another participant seeks clarification on the variable \( p \), questioning whether it refers to a prime number or something else.
  • A participant confirms that \( p \) is any prime number, but expresses confusion regarding the summation and requests further clarification.
  • A later reply corrects the earlier notation, clarifying that the sum is taken over \( n \) and explains that if \( p \) divides \( f(n) \), the exponential term equals 1.
  • Another participant reformulates the expression for \( S \) and discusses the implications of \( f(n) \) being a multiple of \( p \), raising questions about the contributions of other values of \( f(n) \) that do not satisfy this condition and suggesting the need for bounds on the theorem.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and seek clarification on specific aspects of the conjecture and the summation. There is no consensus on the implications or bounds related to the conjecture, indicating ongoing debate and exploration.

Contextual Notes

Some assumptions about the behavior of the exponential sum and the properties of the polynomial function \( f(n) \ remain unresolved. The discussion highlights the complexity of the relationships involved and the need for further exploration of bounds and conditions.

mhill
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let be the exponential sum

[tex]S= \sum_{n=1}^{N}e( \frac{f(x)}{p})[/tex]

[tex]e(x)= exp( 2i \pi x)[/tex]

my conjecture is that since the complex exponential takes its maximum value '1' when x is equal to an integer then

[tex]Re(S)= \Pi (f,N)[/tex] with [tex]\Pi (f,N)[/tex] is the number of solutions on the interval (1,N) of the congruence

[tex]f(x) =0 mod(p)[/tex] and f(x) is a Polynomial.
 
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Forgive me if this is a stupid question- but what's [itex]p[/tex]? Or did you mean [itex]n[/tex] instead or [itex]p[/tex] as the number of prime factors of [itex]n[/tex] or something?[/itex][/itex][/itex][/itex]
 
any prime
 
soandos said:
any prime
I still don't get over what exactly that summation for [itex]S[/tex] is done. A clarification please?[/itex]
 
o sorry.. i should have written


[tex]S= \sum_{n=1}^{N}e( \frac{f(n)}{p})[/tex]


the sum is taken over 'n' but if the prime 'p' divides f(n) then the complex exponential is equal to '1'
 
Okay then [itex]p[/tex] is a prime of one's choosing.<br /> <br /> We have,<br /> <br /> [tex]S = \sum_{n = 1}^{N} \exp{\left(\frac{2\pi i}{p}f(n)\right)}[/tex]<br /> <br /> Then,<br /> [tex]\Re(S) = \sum_{n = 1}^{N} \cos{\left(\frac{2\pi}{p}f(n)\right)}[/tex]<br /> <br /> If [itex]f(n)[/tex] is a multiple of [itex]p[/tex], then the the real part of [itex]S[/tex] will 'count' each solution of that congruence, but what about certain [itex]f(n)[/tex] values that don't and hence give rise to non-zero real and imaginary components? They won't be 1 in a single go, but they can possibly accumulate to values greater than 1 I think. So some bounds for such a theorem also become necessary if I haven't missed anything.[/itex][/itex][/itex][/itex][/itex]
 
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