Clarifying Boundary Conditions and Scalar Field Quantization in QFT

[vaibhavtewari]

This commmunity has so many nice people, so helpful, I am learning QFT from Srednicki

I would be glad if some one can clarify, all the books talk about boundary conditions which are finite at spatial infinity and give the general solution for canonical quantization of scalar field,

1) how can we apply any particular boundary condition ?

2) when we write $$\phi(x)$$ in terms of creation and annihilation operator what do we mean by $$\phi(x)|0\rangle$$, I mean what do we get ? $$\phi(x)$$ which is lorentz invariant scalar field and not an operator field, but then how can we get a scalar field by creating and Annihilation particles.

3) what is the value for $$x|0\rangle$$, we can do that for quantum harmonic oscillator can we do it similarly for scalar field ?

Please help me clarify these doubts

 

[ansgar]

1) "classical limit"

2) psi on vacuum gives a linear combination of particle and antiparticle state, psi = a + a^dagger (in principle)

3) x is not a quantum field operator... recall that we go from x to psi, we don't have position as an operator anymore but just as label... read your srednicki again, first chapter :) :) :)

 

[vaibhavtewari]

Thankyou for explaining, after getting up from 2 week of illness I understood most of it :)