QFT: Questions About Vector Field, Polarization Vectors & Space

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Discussion Overview

The discussion revolves around the concepts of vector fields, polarization vectors, and the nature of space within the context of Quantum Field Theory (QFT). Participants express confusion regarding these topics and seek clarification on the foundational aspects of QFT.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses confusion about the concept of vector fields and questions the reasoning behind the four polarization vectors in QFT.
  • Another participant provides a definition of vector fields, suggesting they are characterized by magnitude and direction at each point in space, using gravity as an example.
  • A different participant notes the importance of classical field theory in understanding QFT and mentions that vector fields are classical notions, citing electric and magnetic fields as examples.
  • There is a suggestion to review classical mechanics and classical fields before tackling QFT texts, with specific references to Goldstein and Jackson.
  • One participant emphasizes the necessity of studying nonrelativistic quantum mechanics before approaching QFT, recommending Sakurai's textbook.
  • There is a brief exchange regarding the acronym QFT, with one participant confirming it stands for Quantum Field Theory.

Areas of Agreement / Disagreement

Participants generally agree on the foundational importance of classical mechanics and field theory in understanding QFT, but there is no consensus on the clarity of the concepts being discussed, as several participants express confusion.

Contextual Notes

Some participants highlight the need for a solid understanding of classical theories before delving into QFT, indicating that assumptions about prior knowledge may affect the discussion.

Who May Find This Useful

This discussion may be useful for students and learners of Quantum Field Theory, particularly those struggling with foundational concepts in vector fields and polarization vectors.

alanzhu
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Hello everyone, I am now learning QFT, this theory is really abstract and daunting. I can't understand the concept of vector field. What is vector field at last? why there are four polarization vectors? I feel that the whole theory is somewhat lack of reasoning, the postulates and assumptions really confuse me. Could someone explain why there are 3 kinds of space and what is the most distinct difference between them.
 
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Could you explain what three kinds of space, please?

A vector field is a phenomenon that is characterised by a magnitude and a direction at each point of space - for example the gravity field near the Earth has an acceleration (a vector with magnitude and direction) at every point, and different values at different points. No?
 
I suspect it also necessary for you to realize that there is a lot of classical field theory in QFT. Vector fields are a perfectly classical notion. Electric and magnetic fields are examples. In relativistic field theories, you get 4-vectors (this tells you how they transform under Lorentz transformations). I suggest you start by reviewing classical mechanics (Goldstein), then move to classical fields (Jackson on electrodynamics); then, only then, pass to something like Peskin and Schroeder or Bjorken and Drell (QFT).
 
...and before those QFT texts, you also need to study a nonrelativistic QM book. Sakurai is the classic one.
 
I could not agree more! Sakurai is a text all physicists should read. The best on QM.
 
What is QFT an acronym for? Quantum...?
 
Qft

Quantum Field Theory. The quantised theory of fields.
 

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