Stress energy tensor general relativity

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Discussion Overview

The discussion revolves around the interpretation of the scalar field \phi as presented by Leonard Susskind in the context of the stress-energy tensor in general relativity. Participants are exploring the nature and implications of this scalar field, particularly in relation to its physical meaning and properties.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant seeks clarification on the meaning of \phi in Susskind's presentation, specifically its role in the energy tensor equation.
  • Another participant suggests that \phi represents a scalar field, described as the simplest type of field, which assigns a numerical value at every point in spacetime.
  • A third participant notes that Susskind refers to it as a "wave field," but reiterates that it is fundamentally a scalar field.
  • A further participant questions the specific type of scalar field \phi represents, asking if it corresponds to any known physical quantity such as temperature or energy.
  • One participant responds that \phi can be considered any scalar field and emphasizes that Susskind is discussing the general properties of the stress-energy tensor for scalar fields without focusing on a specific physical interpretation.
  • This participant also mentions that the only necessary assumption is that the scalar field has units of energy density.

Areas of Agreement / Disagreement

Participants generally agree that \phi is a scalar field, but there is no consensus on the specific type or physical interpretation of this scalar field. The discussion remains unresolved regarding its exact meaning and implications.

Contextual Notes

There are limitations in the discussion regarding the assumptions about the scalar field's properties and its physical significance, which remain unspecified.

Who May Find This Useful

This discussion may be useful for individuals interested in general relativity, scalar fields, and the stress-energy tensor, particularly those looking to understand the nuances of field interpretations in theoretical physics.

mertcan
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Hi, I would like say that in this link ( ) and starting from 56.28 Suskind tries to find the energy tensor equation using \phi, afterwards he finds a equation similar to wave equation in terms of \phi. My question is: For what does \phi stand ? I could not capture the meaning of \phi. Could you explain it ?
 
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mertcan said:
For what does \phi stand

I believe it stands for a scalar field, which is the simplest kind of field (it's just a number at every point of spacetime).
 
He calls it a "wave field" around 53:50, but as Peter says it's just a scalar field.
 
Well, I am aware that it is a scalar field, but What kind of a scalar field does it stands for ? This scalar field does not have any name ? For instance is it a temperature, energy... ?
 
mertcan said:
What kind of a scalar field does it stands for

Any scalar field. AFAICT, Susskind is just explaining the general way that the stress-energy tensor of a scalar field works. He is not trying to explain the physics of any particular scalar field. The only property that would have to be assumed is that the field has units of energy density.
 

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