Derivation of Minkowski norm of the four-momentum

In summary, the conversation discusses the derivation of the Minkowski norm of the four-momentum and how it relates to the concept of mass. The writer is unsure of how the quantity ## -m^2 c^2 ## is derived from ## -\frac {E^2}{c^2} + p^2## and asks for clarification. Another person suggests that mass is defined as the norm of the four momentum and that many physical quantities are related to time, such as acceleration, velocity, and power. The conversation concludes with a student seeking help understanding the basics.
  • #1
TheCanadian
367
13
I have attached a derivation of the Minkowski norm of the four-momentum but just don't quite see how the writer arrived at ## -m^2 c^2 ## from what was given. How exactly does this quantity follow from ## -\frac {E^2}{c^2} + p^2##? I feel like it might be very obvious, so any explanation would be great!
 

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  • #2
I would say that it is a definition rather than a derivation. We use the norm of the four momentum often enough that it deserves a name, so we define the name "mass" to refer to it.
 
  • #3
Guys ...is it so that every physical quantity is related to time?
like ...acceleration is rate of change in the velocity of an object over time...similar is for velocity n power...but what abt other...

cuz simply p=mv ...i don't get it...but ...by equating ...p=mv n F=ma...we can get F=p/t...n can't get this as well...

please sombody helppppp...m a 11th class student n can't go further if i can't get the basics clearly...pleasezz
 

FAQ: Derivation of Minkowski norm of the four-momentum

What is the Minkowski norm of the four-momentum?

The Minkowski norm of the four-momentum is a mathematical quantity that is used in special relativity to measure the energy and momentum of a system. It is a combination of the energy and momentum components in a four-dimensional space-time, and is represented by the equation:
||p|| = sqrt(E^2 - (pc)^2), where E is the energy, p is the momentum, and c is the speed of light.

Why is the Minkowski norm used in special relativity?

The Minkowski norm is used in special relativity because it takes into account the effects of time dilation and length contraction, which are fundamental principles of the theory. It provides a way to measure the energy and momentum of a system in a frame of reference that is moving at a different velocity.

How is the Minkowski norm derived?

The Minkowski norm is derived using the Minkowski metric, which is a mathematical tool that describes the distance between two points in a four-dimensional space-time. By applying this metric to the energy and momentum components, the Minkowski norm is obtained as a way to measure the magnitude of the four-momentum vector.

What is the significance of the Minkowski norm in special relativity?

The Minkowski norm is significant in special relativity because it is an invariant quantity, meaning it has the same value in all frames of reference. This allows for consistent measurements of energy and momentum, regardless of the observer's perspective. It also helps to unify space and time into a single four-dimensional entity, known as space-time.

Can the Minkowski norm be applied to other physical systems?

Yes, the Minkowski norm can be applied to other physical systems, such as particles with mass or particles with zero rest mass (like photons). In these cases, the energy and momentum components would be represented by different equations, but the concept of using the Minkowski norm to measure the four-momentum remains the same. It is a useful tool in understanding the behavior of particles in both special relativity and quantum mechanics.

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