# Questions tagged [path-integral]

Path integral formulation (Due to Feynman) is a major formulation of Quantum Mechanics along with Matrix mechanics (Due to Heisenberg and Pauli), Wave Mechanics (Due to Schrodinger), and Variational Mechanics (Due to Dirac). DO NOT USE THIS TAG for line/contour integrals.

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### $i\epsilon$ prescription for finite systems [closed]

What is physical interpretation of path integral for finite time and finite epsilon (i.e without taking limits time->+-inf, epsilon->0)? Does it mean you are doing some finite temperature qft ...
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### Derivation of Schrödinger equation in Feynman-Hibbs

I am going through the derivation in chapter 4-1 of "Quantum Mechanics and Path Integrals. Emended Edition" by Feynman and Hibbs. The chapter starts with a proof of the equivalence of the ...
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### Path integral at large time

From the path integral of a QFT: $$Z=\int D\phi e^{-S[\phi]}$$ What is a nice argument to say that when we study the theory at large time $T$, this behaves as: $$Z \to e^{-TE_0}$$ where $E_0$ is the ...
1 vote
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### 2PI Effective Action from Double Legendre Transformation

This answer (https://physics.stackexchange.com/q/348673) provides good intuition for why Legendre transformation induces 1-particle irreducible graphs: It mainly tries to convey the idea that the ...
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### Question about Path Integrals and Exchange Statistics in Steve Simon's "Topological Quantum"

In the introduction to the path integral approach leading to exchange statistics for many particles, Steve Simon breaks up the sum of paths into two types: paths where particles do not exchange (type ...
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### physical interpratation of partition function in Quantym field theory

Partition function in Statistical mechanics is given by $$Z = \sum_ne^{-\beta E_n}$$ For QFT, it is defined in terms of a path integral: $$Z = \int D\phi e^{-S[\phi]}$$ How can we see the relation ...
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### How important are purely imaginary finite action solutions for first-order instanton contributions?

I am working on a physics problem where I have to calculate instanton contributions for a non-relativistic Hamiltonian $$H=-\frac{1}{2}\frac{d^2}{dx^2}+\frac{1}{2}x^2+\frac{1}{6}g^2x^6 \tag 1$$ for ...
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### Fermionic propagator [closed]

Given the fermionic generating functional $$Z[\eta]=\ det^{\frac{1}{2}}(K_{ij})e^{-\frac{i}{2}\eta_{i}G^{ij}\eta_{j}},\tag{1}$$ where $$G^{ij}=K^{-1}_{ij}$$ is the Green function of our theory, then ...
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