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On Quantum Field Theory and Observers

V. P. Nair

Abstract

A generalization of the coadjoint orbit action describes the dynamics of an observer (or instrument). We consider how this fits in with the view of observables in field theory being correlations of read-outs of instruments and show how one recovers the usual $S$-matrix formulae. A simple resolution of the Fermi paradox is also pointed out.

On Quantum Field Theory and Observers

Abstract

A generalization of the coadjoint orbit action describes the dynamics of an observer (or instrument). We consider how this fits in with the view of observables in field theory being correlations of read-outs of instruments and show how one recovers the usual -matrix formulae. A simple resolution of the Fermi paradox is also pointed out.

Paper Structure

This paper contains 7 sections, 39 equations, 2 figures.

Table of Contents

  1. Introduction
  2. What is observed
  3. Dynamics of the observer
  4. Density matrix for the observer
  5. $S$-matrix for a scalar field
  6. The Fermi problem
  7. Discussion

Figures (2)

  • Figure 1: The SK$_4$ contour. The inner two branches are for ${\cal A}$, the outer two branches (3 and 4) are for ${\cal A}^*$. The time-intervals are from $t_0$ to $t$; the contours are extended slightly with arcs attached for clarity of the picture.
  • Figure 2: The world lines for the two instruments $A$ and $B$. The figure on the left applies to $v_2^0 > w_2^0$, the one on the right to $w_2^0 > v_2^0$. All time-labels for the left figure are $< v_2^0$, and $< w_2^0$ for the right one; arcs are added only to show continuity of the contours.