What does coupling mean in physics?

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Discussion Overview

The discussion revolves around the term "coupling" in physics, exploring its various meanings and contexts as encountered in literature, particularly in Carroll’s "Spacetime and Geometry." Participants examine coupling in relation to particles, fields, spacetime curvature, and other phenomena, seeking a rigorous definition.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that "coupled" seems to indicate some form of interaction between particles, but highlights the complexity of its use in different contexts, such as matter fields and spacetime curvature.
  • Another participant references Wikipedia's discussion on coupling, specifically mentioning coupled harmonic oscillators where each oscillator influences the others.
  • A participant explains that two fields are considered coupled when they appear multiplied together in the action, affecting each other's equations of motion, while decoupled fields do not interact.
  • One participant expresses uncertainty about the term "coupled," suggesting it may be used poetically in contexts like entanglement.
  • Another participant proposes that two or more variables are coupled if they are described by simultaneous equations.
  • A different perspective suggests that any two objects with a correlation, regardless of category, can be considered coupled, though this is presented as a personal interpretation rather than a formal definition.

Areas of Agreement / Disagreement

Participants express various interpretations of the term "coupling," indicating that there is no consensus on a single rigorous definition. Multiple competing views on its meaning and application remain present in the discussion.

Contextual Notes

Participants acknowledge the complexity and variability of the term "coupling" across different contexts, including its relationship to entanglement and the mathematical formulation of physical theories.

luke m
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I am reading Carroll’s Spacetime and Geometry, and I have seen the word “coupled” used multiple times in seemingly different ways. I have gotten the sense that it means some sort of interaction between particles, but Carroll refers to coupling between matter fields and the curvature of spacetime. Furthermore, these are said to to not be directly coupled, even though they are related by Einstein’s equation. I have also seen “coupled” used in the context of coupling constants, entanglement, and forces in the early universe. Is there a rigorous definition for this word?
 
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Two fields are coupled when, in the action, they appear multiplied to each-other in some way. The equations of motion then indicate that the EOM of field A also involves field B.

The other way around: if fields are decoupled, they live "along each other without noticing each-other".
 
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luke m said:
I am reading Carroll’s Spacetime and Geometry, and I have seen the word “coupled” used multiple times in seemingly different ways. I have gotten the sense that it means some sort of interaction between particles, but Carroll refers to coupling between matter fields and the curvature of spacetime. Furthermore, these are said to to not be directly coupled, even though they are related by Einstein’s equation. I have also seen “coupled” used in the context of coupling constants, entanglement, and forces in the early universe. Is there a rigorous definition for this word?

haushofer said:
Two fields are coupled when, in the action, they appear multiplied to each-other in some way. The equations of motion then indicate that the EOM of field A also involves field B.

The other way around: if fields are decoupled, they live "along each other without noticing each-other".
I thought the "common denominator" was lightlike or closer stuff. But apparently "coupled" was used in the context of "entanglement". I think "coupled" much like entanglement, is used poetically in said contexts.
 
As i understand it two or more variables are considered to be coupled whenever they are described by simultaneous equations.
 
luke m said:
Is there a rigorous definition for this word?

Say any two objects (particles, fields, quantum states, etc.) of the same caterory or other, have a correlation, they are coupled. Please take care it is just my interpretation, not the definition of the term.
 

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