Big Steve and the State of the Universe

Abstract

I share some reminiscences of the late Steven Weinberg. Then I discuss a topic in quantum field theory which he taught me: the role of state wave functionals in deriving the $i\epsilon$ term of the Feynman propagator when using the functional formalism. This is perhaps a curiosity for in-out scattering amplitudes on flat space backgrounds, but it is has much greater significance for the in-in amplitudes of the Schwinger-Keldysh formalism in cosmology. It also touches on the fate, about which Weinberg wondered, of the large logarithms one sometimes finds in quantum corrections from inflationary particle production.

arXiv comment19 pages, uses LaTeX2e, written for a special issue of Symmetry Commemorating Steven Weinberg. Version 2 slightly revised for publication

References in corpus (42)

• Quantum Contributions to Cosmological Correlations
• Equilibrium State of a Massless Self-Interacting Scalar Field in the De Sitter Background
• Quantum effects can render w<-1 on cosmological scales
• Super-Acceleration from Massless, Minimally Coupled ${\varphi }^4$
• The Quantum Gravitational Back-Reaction On Inflation
• Quantum Contributions to Cosmological Correlations II: Can These Corrections Become Large?
• Stochastic Quantum Gravitational Inflation
• On Loops in Inflation
• Stochastic Inflationary Scalar Electrodynamics
• Goldstone Bosons as Fractional Cosmic Neutrinos
• Tetraquark Mesons in Large $N$ Quantum Chromodynamics
• Leading Log Solution for Inflationary Yukawa
• Reply to `Can infrared gravitons screen $\Lambda$?'
• Gravitons Enhance Fermions during Inflation
• Can infrared gravitons screen $\Lambda$?
• The Zeta-Zeta Correlator Is Time Dependent
• A Completely Regular Quantum Stress Tensor with $w<-1$
• de Sitter invariance of the dS graviton vacuum
• A Simple Operator Check of the Effective Fermion Mode Function during Inflation
• Gravitational Waves in Cold Dark Matter
• Quantum Mechanics Without State Vectors
• Infrared resummation for derivative interactions in de Sitter space
• Excitation of Photons by Inflationary Gravitons
• Electrodynamic Effects of Inflationary Gravitons
• Models of Lepton and Quark Masses
• Non-linear sigma model in de Sitter space
• Gauging away Physics
• A Gravitational Mechanism for Cosmological Screening
• Infra-red effects of Non-linear sigma model in de Sitter space
• Quantum Scalar Corrections to the Gravitational Potentials on de Sitter Background
• Summing Inflationary Logarithms in Nonlinear Sigma Models
• Lindblad Decoherence in Atomic Clocks
• On the Development of Effective Field Theory
• What Happens in a Measurement?
• Large Logarithms from Quantum Gravitational Corrections to a Massless, Minimally Coupled Scalar on de Sitter
• Deducing Cosmological Observables from the S-matrix
• Absorption of Gravitational Waves from Distant Sources
• Massless Particles in Higher Dimensions
• How Inflationary Gravitons Affect the Force of Gravity
• Soft Bremsstrahlung
• How Inflationary Gravitons Affect Gravitational Radiation
• Unfinished Business in A Nonlinear Sigma Model on de Sitter Background

Cited by in corpus (3)

• Observations in Quantum Cosmology
• Initial value formulation of a quantum damped harmonic oscillator
• Vacuum zero point energy of self-interacting quantum fields in dS background