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In my limited understanding of particle, particles are viewed as perturbation on a field.

In the standard model, where and what is the energy? For instance, classically, the energy of a particle is speed squared times a constant plus the potential to have more speed. If now all of a sudden, particles are fields what the heck is energy?

I realized this question is slightly philosophical, so if there is no answer feel free to tell me that as well. If that is the case can you tell me (as best as one can) how the quantity of energy is calculated in particle physics

Qmechanic
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EEH
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    Quantum fields have an associated energy-momentum-stress tensor $T^{\mu\nu}$ describing how the density and flow of energy and momentum are distributed in the field. This is what appears on the right side of the Einstein field equations in General Relativity. – Ghoster Nov 02 '22 at 04:07
  • Related: https://physics.stackexchange.com/q/119838/2451 and links therein. – Qmechanic Nov 30 '22 at 05:32
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    Rather than jumping from classical mechanics to quantum field theory and wondering “where energy is”, I suggest that you first detour through classical field theory, such as for electromagnetism. From Maxwell’s equations one can show that energy, momentum, and angular momentum can all reside, and flow, in the field, in addition to being carried by particles. Unless one includes the field contributions, these quantities are not conserved. There are explicit formulas for the density and flow of electromagnetic energy, momentum, and angular momentum. – Ghoster Nov 30 '22 at 05:59
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    When the EM field is quantized, these field quantities become operators, in a similar way that other classical quantities become operators in, say, non-relativistic quantum mechanics. – Ghoster Nov 30 '22 at 06:03
  • @Ghoster will do. I will have a look at Landau (unless you have better rec) over break and return to this question afterward. – EEH Dec 01 '22 at 02:43

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