# Tagged Questions

Renormalization is an ensemble of techniques which serves to treat the infinities which appear in quantum field theory or statistical mechanics.

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### Renormalization Group in Condensed Matter [on hold]

Are RG calculations done only in the vicinity of a phase transitions in cond-matt?
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### How to estimate the phase diagrams ($d=2$) using the renormalization method (Migdal-Kadanoff)? [on hold]

How can I establish the phase diagrams using the Renormalization group method (Migdal-Kadanoff)?
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### Renormalization group equation: physical meaning of energy scale [duplicate]

I'd like to understand the physical meaning of the energy scale $\mu$ that emerges in the renormalization group equation (RGE). In particular I don't understand in what way a running coupling constant ...
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### The relation between critical surface and the (renormalization) fixed point

In the book, I read some remarks about the criticality: Iterations of the renormalization (group) map generate a sequence of points in the space of couplings, which we call a renormalization ...
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### Running of $\alpha$ and scattering amplitudes

Consider a QED scattering process $e^-+e^-\rightarrow e^-+e^-$. The scattering crosssection at the tree-level depends on the square of the fine-structure constant $\alpha$ (apart from the electron ...
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### Simple analytic examples of MERA

I want to understand Multi-scale Entanglement Renormalization Ansatz (MERA) with very elementary examples. So far I could find references which are mostly based on numerics. It would be a great help ...
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### Renormalisation group equation for Green's functions

The renormalization group equations for the $n$-point Green’s function $$\Gamma(n) = \langle \psi_{x_1} \dots \psi_{x_n}\rangle$$ in a four-dimensional massless field theory are \mu \frac{d}{d \mu}...
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### Mass of an imaginative stable top quark at low energies? [duplicate]

Masses are not fixed quantities, but change with energy because of the renormalization group running. These can be calculated in a given renormalization scheme, for example, the MS scheme: Imagine ...
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### Top quark mass $m_t$ at energy scales $\mu < m_t$?

Edit - Maybe formulated differently: Does it make sense to talk about the top mass at energies below $m_t$, although in all processes the corresponding energy scale is above $m_t$, because of the rest ...