# Tagged Questions

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 ...

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### Closed form expression for the partial decay widths of Higgs boson in massive vector bosons

Can anybody help me obtain a closed form expression for the Higgs partial decay width into massive vector bosons (off shell decays)? I am writing code for the partial decay widths of the Higgs and ...
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### Feynman diagram elementary vertex with 4 lines?

Are there processes that require vertices with 4 lines in a Feynman diagram? (And cannot be written as composition of 3-line vertices?) If not, is it matter of models we use (where there are no ...
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### Which inverse of $-(\partial^2 + m^2)$ should be used in the path integral?

The partition functional for free scalar field is $$Z=\int D\varphi e^{i\int d^4x[-\frac{1}{2}\varphi (\partial^2+m^2)\varphi+J\varphi]}.\tag{1}$$ To evaluate this functional integral, we usually ...
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### An integral in mass renormalization in Peskin and Schroeder

I cannot figure out an integral (which involves certain approximations) in the textbook Quantum Field Theory by Peskin and Schroeder. On P.220 Eq.(7.28-29), it is mentioned that the integral (7.28) ...
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### Construction of vector bundles of relativistic fields by Mackey's method of induced representation

I recently stumbled on Sternberg's book on group theory and physics. The ideas expressed in the book are really great, but the detailed reasoning is very hard to follow, I find. I am kind of stuck ...
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### What is the matrix representation of the momentum operator (generator of translations) that is used in the commutators of the Poincaré Group?

So the commutators of the Poincareé group are given by \begin{eqnarray} [J_{i},P_{j}]=i\epsilon_{ijk}P_{k}, \quad [J_{i},J_{j}]=i\epsilon_{ijk}J_{k}, \quad [J_{i},K_{j}]=i\epsilon_{ijk}K_{k}, \quad [...
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### Is the reduction of tensor loop integrals to scalar integrals using Passarino Veltman Functions, theory dependent?

While reducing the tensor integrals to scalar integrals all that we use are Lorentz covariance and the physical interpretation of the result. Thus I think that the Pa Ve Reduction of Tensor integrals ...
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### Why must the Vacuum Manifold contain the quotient group?

For a symmetry breaking pattern $G \rightarrow H$, the vacuum manifold must contain the quotient space $G/H$. In most cases, we take the vacuum manifold to be the quotient space. My question is, Is ...
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### Interpretation of the mass of the field

Before QFT I had never thought if a field should or should not have any mass. Now it turns out that either case is possible. It might be naive to think this way, but I picture the mass of the field in ...