Thursday, 19 February 2015

quantum field theory - Canonical second quantization vs canonical quantization with multisymplectic form in AQFT



First of all, I'm a mathematician that knows less than the basics of QFT, so forgive me if this question is trivial. Please, keep in my mind that my background in physics is very poor.


1) The usual process of quantization of a free scalar field on Q is by using Weyl operators W(f) for each fSL2(TQ) (where S is a space of solutions) such that W(f)W(g)=exp(iσ(f,g))W(f+g)

for some (pre-)symplectic form σ.


This process is explained for the Klein-Gordon equation here The most general procedure for quantization


2) On the other side, in http://arxiv.org/abs/physics/9801019 and http://arxiv.org/abs/math-ph/0408008, given a configuration bundle FX

with X a globally hyperbolic Lorentzian manifold of dimension n+1 and a Lagrangian density L:J1FΛn+1TX
such that L=Ldx. Let (J1(F))=Hom(J1F,Λn+1TX),
FL:J1F(J1F)
be the Legendre transform, ω=dθ and θ is the canonical form on (J1F). Then ωL=FLω=dθL
for θL=FLθ is a a multisymplectic form of degree n+2.


Given Cauchy surface ΣX, it's possible to produce a (pre-)symplectic form ΩΣ=ΣωL

on the off-shell (the space of all sections).


Locally on coordinates θL=Lvaμduadx0^dxμdxn+(LLvaμvaμ)dx


3) Analogously in http://arxiv.org/1402.1282 and http://ncatlab.org/nlab/show/multisymplectic+geometry, one can consider the first variation δL=a(ELL)aδua+dθL

, where (ELL)a is the Euler-Lagrange equation and (xμ,ua,vaμ) are the local coordinates of J1F. In this context ωL=ELL+δθL
is a n+2-form which is (pre-) multisymplectic.


In a lot of references, it's said that the variational principle 3) coincides with 2). It's said too that θL in 3) coincides with the usual boundary condition a,μLvaμδua

(which seems impossible). I would like an answer to these two questions. These are two minor questions that are probably because of a miscalculation of my part or the authors.


Now my main question is : How can one relate 1) to 3)?


More precisely, are the symplectic forms the same in these two approaches? If not, do canonical quantization of 3) (via Weyl CCR or non-exponeniated CCR) produce an equivalent QFT?





EDIT


The second of my minor question is obviously true, because of the Stokes formula. The boundary condition can be written as Va,μLvaμδuavolV=Va,μd(Lvaμδua)dx

for some suitable region VX.


Anyway the first minor question remains. In other words, is θL=Lvaμδuadx in 3) equals to Lvaμduadx0^dxμdxn+(LLvaμvaμ)dx (θL in 2))?


All the terms except Ldx seems reasonable to appear in θL of 3).




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