My questions are about worldline path integrals from the book Gauge Fields and Strings of Polyakov.
On page 153, chapter 9, he says
>Let us begin with the following path integral
H(x,y)[h(τ)]=∫yxDx(τ)δ(⋅x2(τ)−h(τ))=∫Dλ(τ)exp(i∫10dτλ(τ)h(τ))∫yxDx(τ)exp(−i∫10dτλ(τ)˙x2(τ))
where h(τ) is the worldline metric tensor.
>The action in (9.8) is invariant under reparametrizations, if we transform:
x(τ)→x(f(τ))h(τ)→(dfdτ)2h(f(τ))λ(τ)→(dfdτ)−1λ(f(τ))
Polyakov continued with the following statement.
>It is convenient to introduce instead of the worldline vector λ(τ), the worldline scalar Lagrange multiplier α(τ):
λ(τ)≡α(τ)h(τ)−1/2α(τ)→α(f(τ))
So that:
H(x,y)[h(τ)]=∫Dα(τ)ei∫10dτα(τ)√h(τ)∫yxDx(τ)exp(−i∫10dτα(τ)˙x2(τ)√h(τ))
My first question is about equation (9.12). What Polyakov did there is boldly replace the integral measure Dλ by Dα. Didn't he miss the Jacobian factor?
Dλ=Dαdet(δλδα)
My second question is the following.
He introduced another parameter t, called proper time, defined as
>t≡∫τ0√h(s)ds;T≡t(1)
and so
H(x,y)[h(τ)]≡H(x,y;T)=∫Dαexpi∫T0α(t)dt∫yxDxexp−i∫T0α(t)˙x2(t)dt
Can anybody tell me how he derived the equation (9.14) via using the "proper time" parameter t?
I also posted my question here here.