Does Special Relativity Offer a Continuity Equation for Energy Conservation?

In summary, the conversation discusses the existence of an energy continuity equation, specifically one involving Pmu or the stress energy tensor. It is mentioned that in special relativity, the continuity equation expresses the conservation of energy and momentum locally in curved spacetime and globally in flat spacetime. However, the validity of this equation in special relativity is still debated and may depend on individual cases until the Einstein equation is applied.
  • #1
Phrak
4,267
6
Is there such an animal as an energy continuity equation, or one involving Pmu or the stress energy tensor?

It suddenly stuck me that if we are to be so inclined by theory as we are by empirical evidence that energy is a conserved quantity, then there should be an equation that describes it in four dimensions.

Rather than bring in general relativity all at once where energy is not well defined (I have reservations), the stress energy tensor is still a tensor in special relativity, and so special relativity might be the better place to start.
 
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  • #2
Yes, the continuity equation:
[tex]\nabla_{\nu}T^{\mu\nu}=0[/tex]

This expresses the conservation of energy and momentum locally in curved spacetime and globally in flat spacetime.
 
  • #3
DaleSpam said:
Yes, the continuity equation:
[tex]\nabla_{\nu}T^{\mu\nu}=0[/tex]

This expresses the conservation of energy and momentum locally in curved spacetime and globally in flat spacetime.

Thanks, I should have done some research sooner. It seems, at this point the validity of \nabla T = 0 in special relativity goes on a case by case basis, until the Einstein equation is invoked where the Bianchi identity is applied to the other side.
 

1. What is the energy continuity equation?

The energy continuity equation is a fundamental equation in physics that describes the conservation of energy in a system. It states that the total energy in a closed system remains constant over time, meaning that energy cannot be created or destroyed, only transferred or transformed.

2. What are the components of the energy continuity equation?

The energy continuity equation consists of three components: the energy input, the energy output, and the change in energy within the system. The input and output terms refer to the energy that enters and leaves the system, while the change in energy term represents any internal energy changes within the system.

3. How is the energy continuity equation used in practical applications?

The energy continuity equation is used in a variety of practical applications, such as in thermodynamics, fluid mechanics, and electrical circuits. It is a useful tool for analyzing and predicting the behavior of energy in a system, and is essential for understanding many natural phenomena and engineering processes.

4. What are some common misconceptions about the energy continuity equation?

One common misconception is that the energy continuity equation only applies to closed systems. In reality, it can also be applied to open systems where energy can enter or leave. Another misconception is that the equation only applies to certain types of energy, when in fact it applies to all forms of energy, including mechanical, thermal, electrical, and chemical energy.

5. How does the energy continuity equation relate to the first law of thermodynamics?

The energy continuity equation is essentially a mathematical representation of the first law of thermodynamics, which states that energy cannot be created or destroyed, only transferred or transformed. The energy continuity equation provides a way to quantify this conservation of energy in a system, making it a powerful tool for analyzing energy dynamics in various systems.

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