Is the Electromagnetic Field a Classical or Quantum Field?

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Discussion Overview

The discussion centers on the nature of the electromagnetic field, specifically whether it is classified as a classical field or a quantum field. Participants explore concepts from quantum field theory (QFT), classical field theory, and the implications of second quantization.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions how to differentiate between classical and quantum fields, expressing dissatisfaction with existing explanations.
  • Another participant states that in quantum field theory, fields are represented as operators that follow specific commutation relations.
  • Several participants inquire about the classification of the electromagnetic field, noting that in quantum discussions, it is often described in terms of photons.
  • One participant elaborates that applying canonical quantization to the Lagrangian of the electromagnetic field leads to a quantum field theory, specifically Quantum Electrodynamics, and mentions that second quantization corresponds to this quantum framework where excitations are photons.

Areas of Agreement / Disagreement

There is no consensus on whether the electromagnetic field is strictly classical or quantum, as participants present differing viewpoints and explore the implications of both frameworks.

Contextual Notes

Participants reference the Lagrangian formulation and the transition from classical to quantum descriptions, but the discussion does not resolve the underlying assumptions or definitions that may influence these classifications.

dilna
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how we can differentiate classical and quantum fields?i searched everywher..but i did not get a satisfactory answer
 
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In QFT the fields are operators that obey a commutation relation.
 
electromagnetic field is a classical field or quantum field?in quantum we speak in erms of photons...if we go for second quantisation to electromagnetic field what we will get??
 
dilna said:
electromagnetic field is a classical field or quantum field?in quantum we speak in erms of photons...if we go for second quantisation to electromagnetic field what we will get??

Um... there is a Lagrangian that gives the electromagnetic field, working with this field classically one obtains a classical field theory (Maxwell's equations, etc.), if one instead applies canonical quantization to this Lagrangian one gets a quantum field theory (Quantum Electrodynamics). Second quantization IS quantum field theory, the excitations in this case are photons.
 

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