Klein gordon field Definition and 13 Threads

For the solution of the equation of motion, we take a plane wave ##\phi(x) = e^{ik_\mu x^\mu}##. Plugged in, we obtain $$ -(k_0)^2 + (\vec{k})^2 = 2c_2 \Rightarrow k_\mu k^\mu = 2c_2 $$ One can then find the group velocity (using ##(k_0)^2 = \omega^2##) to be $$ \vec{v}_g =...

As $$\hat{P_i} = \int d^3x T^0_i,$$ and $$T_i^0=\frac{\partial\mathcal{L}}{\partial(\partial_0 \phi)}\partial_i\phi-\delta_i^0\mathcal{L}=\frac{\partial\mathcal{L}}{\partial(\partial_0 \phi)}\partial_i\phi=\pi\partial_i\phi.$$ Therefore, $$\hat{P_i} = \int d^3x \pi\partial_i\phi.$$ However...

From Wikipedia: Which should be conceptually similar of what happen in the non-relativistic limit of the Dirac equations when you see that the solutions decouple. Do you have any reference that I can look up where the derivation for the KG field is performed? Thanks in advance!

The correct answer is: #P = \int \frac{dp^3}{(2\pi)^3}\frac{1}{2E_{\vec{p}} \big(a a^{\dagger} + a^{\dagger}a\big)# But I get terms which are proportional to ##aa## and ##a^{\dagger}a^{\dagger}## I hereunder display the procedure I followed: First: ##\phi = \int...

Starting with the action for a free scalar field $$S[\phi]=\frac{1}{2}\int\;d^{4}x\left(\partial_{\mu}\phi(x)\partial^{\mu}\phi(x)-m^{2}\phi^{2}(x)\right)=\int\;d^{4}x\mathcal{L}$$ Naively, if I expand this to second-order, I get $$S[\phi+\delta\phi]=S[\phi]+\int\;d^{4}x\frac{\delta...

Homework Statement Consider the free real scalar field \phi(x) satisfying the Klein-Gordon equation, write the Hamiltonian in terms of the creation/annihilation operators. Homework Equations Possibly the definition of the free real scalar field in terms of creation/annihilation operators...

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 real Klein-Gordon field. The approach I'm currently studying is that by Matthew Schwartz. In his QFT book he first solves the classical KG equation...

Homework Statement Consider the quantum mechanical Hamiltonian ##H##. Using the commutation relations of the fields and conjugate momenta , show that if ##F## is a polynomial of the fields##\Phi## and ##\Pi## then ##[H,F]-i \partial_0 F## Homework Equations For KG we have: ##H=\frac{1}{2} \int...

Homework Statement a)Show that the yukawa potential is a valid static-field euation b)Show this solution also works Homework EquationsThe Attempt at a Solution Part (a) Using the relation given, I got LHS = \frac{e^{-\mu r}}{r} \left[ (m^2 - \mu^2) - \frac{2\mu}{r} - \frac{2}{r^2}...

Note: I'm posting this in the Quantum Physics forum since it doesn't really apply to HEP or particle physics (just scalar QFT). Hopefully this is the right forum. In Peskin and Schroeder, one reaches the following equation for the spacetime Klein-Gordon field: $$\phi(x,t)=\int...

Hi everyone! Im' a new member and I'm studying Quantum Field Theory. I read this: "The interpretation of the real scalar field is that it creates a particle (boson) with momentum p at the point x." and : \phi\left(x\right) \left|0\right\rangle = \int \frac{d^3p}{(2\pi)^3(2\varpi_p)}...

Hi everyone The Hamiltonian of the Klein Gordon field can be written as H = \frac{1}{2}\int d^{3}E_p \left[a^{\dagger}(p)a(p) + a(p)a^{\dagger}(p)\right] and we have [H,a(p')] = -E_{p'}a(p') [H,a(p')] = +E_{p'}a^{\dagger}(p') The book I'm reading states that What does this mean? Thanks.

Hi I've been reading through the book "Quantum Field Theory: A Tourist Guide for Mathematicians" by George B. Folland. On page 101, he describes the construction of a scalar field "in a box" \mathbb{B}: \left[-\frac{1}{2}L,\frac{1}{2}L\right]^3 in \mathbb{R}^3. Here \bf{p} lies in the...