Why Are Primes Used in the Electromagnetic Signals Equation in Cosmology?

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Homework Help Overview

The discussion revolves around the use of primes in the context of integrals related to electromagnetic signals in cosmology. The original poster seeks clarification on the significance of the prime notation in the equations presented.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster questions the necessity of using prime notation in the integrals, seeking to understand its significance. Some participants suggest that the prime is used to avoid confusion between the variable and the bounds of integration.

Discussion Status

The discussion is exploring the reasoning behind the notation used in the integrals. Some participants have provided insights regarding the use of primes, indicating that it is primarily for clarity in the mathematical expression. There is an ongoing exchange of ideas without a definitive conclusion.

Contextual Notes

Participants are discussing the notation within the constraints of the mathematical expressions provided, focusing on the implications of variable naming in the context of integration.

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Homework Statement



Title should be: ELectromagnetic signals in cosmology.

[itex] \int\frac{d\rho}{\sqrt{1-k\rho^2}}>=-\int\frac{dt'}{a(t')}[/itex]

The integrals being from r1 to r and t1 to t respectively.

I can't understand the need for the prime here. Could someone explain to me the significance of the prime?

Homework Equations



The Attempt at a Solution

 
Last edited:
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It's just because they don't want to have the same variable in the integrand and the bounds of integration. Nothing special.
 
Ok so I could just as well write dt, and a(t), i.e. without the prime, as long as I had t1 to t2 or other such in the bounds of the integration?
 
yes.
 

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