# quantum field theory

### A Observable particles as asymptotic states...

I've read Arnold Neumaier's excellent Insight article on virtual particles, but I'm very confused about one thing: Observable particles are...
Thread by: asimov42, Sep 20, 2017 at 12:08 AM, 36 replies, in forum: Quantum Physics

### A Wick contraction for same indices (Zee, "QFT in a Nutshell")

Hey, I thought I understood Wick contractions but a formula in Zee's "Quantum Field Theory in a Nutshell" disproved me: In the section on...
Thread by: rob_dd, Sep 15, 2017, 1 replies, in forum: Quantum Physics

### Insights Introduction to Perturbative Quantum Field Theory - Comments

Urs Schreiber submitted a new PF Insights post Introduction to Perturbative Quantum Field Theory [ATTACH] Continue reading the Original PF...
Thread by: Urs Schreiber, Sep 12, 2017, 23 replies, in forum: Quantum Physics

### Functional Derivative with respect to Dirac Spinors

1. The problem statement, all variables and given/known data I am currently working on an exercise list where I need to calculate the second...
Thread by: ur22, Aug 17, 2017, 1 replies, in forum: Calculus and Beyond Homework

### Quantum QFT book recommendations except Peskin/Schroeder

Hello! Due to the textbook by Peskin and Schroeder being rather old, I was wondering what are other, more pedagogical textbooks on Quantum Field...
Thread by: Joker93, Aug 5, 2017, 2 replies, in forum: Science and Math Textbooks

### Quantum What are your thoughts on Manoukian's QFT textbooks?

Hello! Manoukian's two books on Quantum Field Theory seem pretty good to me, but before buying them I would like to know your thoughts about them!...
Thread by: Joker93, Aug 5, 2017, 1 replies, in forum: Science and Math Textbooks

### I 'Normalisation' of Fourier Transforms in QFT

Hi there - just a quick question about Fourier transforms: When learning about quantum mechanics, I found that the Fourier transform and inverse...
Thread by: tomdodd4598, Aug 1, 2017, 1 replies, in forum: Quantum Physics

### A Dyson's Formula from Tong's lecture notes

I am studying quantum field theory from [David Tong's lecture notes][1] and I am stuck at a particular place. In Page 52., under the heading...
Thread by: noir1993, Jul 10, 2017, 19 replies, in forum: Quantum Physics

### Dirac Lagrangian invariance under chiral transformation

Consider the Dirac Lagrangian, L =\overline{\psi}\left(i\gamma^{\mu}\partial_{\mu}-m\right)\psi, where...
Thread by: ppedro, Jun 22, 2017, 5 replies, in forum: Advanced Physics Homework

### Insights Entanglement Entropy – Part 2: Quantum Field Theory - Comments

ShayanJ submitted a new PF Insights post Entanglement Entropy – Part 2: Quantum Field Theory [ATTACH] Continue reading the Original PF Insights...
Thread by: ShayanJ, Jun 20, 2017, 3 replies, in forum: Quantum Physics

### A How are renormalizability and locality connected?

In his paper Quantum Field Theory: renormalization and the renormalization group Zinn-Justin states: Low energy physics does not depend on all...
Thread by: jakob1111, Jun 19, 2017, 1 replies, in forum: High Energy, Nuclear, Particle Physics

### A What does a CPT transformation do to particle properties?

If I have a particle with: Momentum: p Spin: s Energy: E Position: x Time coordinate: t Charge: q And I preform a CPT transformation on said...
Thread by: Mr. Chiappone, Jun 1, 2017, 14 replies, in forum: Quantum Physics

### Other Quantum Information and General Relativity

Last year I've finished the undergraduate course in Mathematical-Physics and Mathematics and this year I've started on graduate school on Physics...
Thread by: leo., May 25, 2017, 2 replies, in forum: Academic Guidance

### B How does string theory fit with QFT?

In string theory, particles is vibrating strings. However, QFT treats particles as excitations in a quantum field. Can both of these theories be...
Thread by: Bertel, May 23, 2017, 2 replies, in forum: Quantum Physics

### I Quantum "tunneling" of sorts and QFT...

Hi all, Another naive question related a previous post (where the topic diverged somewhat). I'm wondering about the following thought experiment:...
Thread by: asimov42, May 16, 2017, 16 replies, in forum: Quantum Physics

### Strings, Virasoro Operators&constraints, commutator algrebra

1. The problem statement, all variables and given/known data Question: (With the following definitions here: [ATTACH] ) - Consider $L_0|x>=0$...
Thread by: binbagsss, May 14, 2017, 1 replies, in forum: Advanced Physics Homework

### I Change in electron energy level and photon emission...

Hi all, This is likely a naive question, following up on something @vanhees71 posted some time ago in another thread: ... the emission of a...
Thread by: asimov42, May 8, 2017, 7 replies, in forum: Quantum Physics

### Decay rate of a particle into three particles

1. The problem statement, all variables and given/known data Consider the process of decay of a muon into one electron, one electron antineutrino...
Thread by: leo., Apr 30, 2017, 1 replies, in forum: Advanced Physics Homework

### B What exists between Strings in String Theory?

Hello, I am new to this. As I understand it, the difference between the quantum field theory and string theory is that in the former, physical...
Thread by: icantevenn, Apr 25, 2017, 5 replies, in forum: Beyond the Standard Model

### I Momentum and energy in QM and QFT

Hi all - apologies, I'm starting a new thread here for something buried at the end of another thread - but I think the topic of that thread had...
Thread by: asimov42, Apr 15, 2017, 9 replies, in forum: Quantum Physics

### I Common interaction vacuum for QED + QCD?

Hello, I know QED and QCD as isolated theorys but now I thought about particle interactions with QED and QCD processes (like fpr...
Thread by: Neutrinos02, Apr 15, 2017, 5 replies, in forum: Quantum Physics

### Hamiltonian in terms of creation/annihilation operators

1. The problem statement, all variables and given/known data Consider the free real scalar field \phi(x) satisfying the Klein-Gordon equation,...
Thread by: leo., Apr 12, 2017, 2 replies, in forum: Advanced Physics Homework

### I Understanding the scalar field quantization

I am getting started with QFT and I'm having a hard time to understand the quantization procedure for the simples field: the scalar, massless and...
Thread by: leo., Mar 22, 2017, 5 replies, in forum: Quantum Physics

### I Wave equation solution using Fourier Transform

I'm studying Quantum Field Theory and the first example being given in the textbook is the massless Klein Gordon field whose equation is just the...
Thread by: leo., Mar 13, 2017, 2 replies, in forum: Differential Equations

### A Deriving the Lagrangian from the Hamiltonian operator

In classical mechanics, the Hamiltonian and the Lagrangian are Legendre transforms of each other. By analogy, in quantum mechanics and quantum...
Thread by: redtree, Mar 7, 2017, 3 replies, in forum: Quantum Physics

### A Primaries, descendents and transformation properties in CFT

I want to clarify the relations between a few different sets of operators in a conformal field theory, namely primaries, descendants and operators...
Thread by: Kurret, Feb 27, 2017, 1 replies, in forum: High Energy, Nuclear, Particle Physics

### B Why is there a quantum field?

Are there thoughts as to why there is a quantum field. Does it arise from something more fundamental? Thanks for considering.
Thread by: Twodogs, Feb 24, 2017, 13 replies, in forum: Quantum Physics