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Results tagged with quantum-field-theory
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user 4093
Quantum Field Theory (QFT) is the theoretical framework describing the quantisation of classical fields which allows a Lorentz-invariant formulation of quantum mechanics. QFT is used both in high energy physics as well as condensed matter physics and closely related to statistical field theory. Use this tag for many-body quantum-mechanical problems and the theory of particle physics. Don’t combine with the [quantum-mechanics] tag.
6
votes
1
answer
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views
Quantum Field Theory: why fields are equal to zero on the boundary?
One of the first assumptions, when introducing the Lagrangian and Hamiltonian in an undergraduate course on QFT is
$$
\phi(x)=0\,\text{on the boundary}
$$
and this is widely used in many situations (e …
8
votes
0
answers
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views
Gaussian Integrals : Functional determinant expressed as a trace
Be $A_{ij}$ a symmetric matrix. Then I can easily write
$$
\int \exp\left(-\frac{1}{2}\sum_{i,j}x_i A_{ij} x_j+\sum_{i} B_i x_i\right)\; d^nx=
\sqrt{(2\pi)^n}\exp\left\{-\frac{1}{2}\mathrm{Tr}\log A …