Meaning of "c number equations"?

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In summary, the term "c-number" is used in quantum optics to refer to classical or commuting numbers, as opposed to operators, which were once referred to as "q-numbers." This term is used in various contexts and is not related to the speed of light.
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TheCanadian
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I keep reading authors refer to "c number equations" in different texts on quantum optics. Perhaps I am missing something very obvious, but what exactly does this mean? Does it mean complex-valued equations? Does it have to do with the speed of light? Does c describe the number of equations being evaluated?

Here are a couple examples:

1st paragraph of page 190

Section 6.2 in this text

I've just seen the term used in different contexts yet never had its meaning clarified. Maybe it's so blatantly obvious that it does not require explanation. But nevertheless, I am looking for one.
 
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The term "c-number" refers to so-called 'classical' or 'commuting' numbers i.e. they are just ordinary numbers and not operators (there was a time when operators were referred to as "q-numbers" - the "q" ostensibly meaning "quantum").
 
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Fightfish said:
The term "c-number" refers to so-called 'classical' or 'commuting' numbers i.e. they are just ordinary numbers and not operators (there was a time when operators were referred to as "q-numbers" - the "q" ostensibly meaning "quantum").

Interesting! Thank you for the help.
 

FAQ: Meaning of "c number equations"?

1. What is the significance of "c" in c number equations?

In physics, "c" typically represents the speed of light. In c number equations, it refers to the speed of light in a vacuum, which is approximately 299 792 458 meters per second.

2. How are c number equations used in physics?

C number equations are used in various areas of physics, including quantum mechanics, electromagnetism, and relativity. They help describe the behavior and interactions of particles and fields at the microscopic level.

3. Can you give an example of a c number equation?

One example of a c number equation is the famous equation E=mc², which relates energy (E) to mass (m) and the speed of light squared (c²).

4. Are c number equations only applicable to light?

No, while the "c" in c number equations is often associated with the speed of light, it can also refer to the speed of any massless particle or wave, such as a photon or a gravitational wave.

5. Why are c number equations important in understanding the universe?

C number equations are crucial in understanding the fundamental laws and principles that govern the behavior of matter and energy in the universe. They help explain phenomena such as the behavior of particles at high speeds, the interaction of electromagnetic fields, and the curvature of space-time.

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