All Questions
Tagged with renormalization energy
10
questions
2
votes
1
answer
47
views
Why does integrating out microscopic degrees of freedom lead to the effective free energy rather than the effective energy?
In David Tong's lecture notes on statistical field theory, he considers the partition function of the Ising model and computes the effective free energy by integrating out the microscopic details of ...
- 23
3
votes
0
answers
41
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Calculation of a RG-transformed energy functional
Consider the Landau-Wilson energy functional in a constant magnetic field:
$$E[m] = \int d^dx \left[\frac{1}{2} \vec\partial m(x))^2+ \frac{1}{2} r_0 m^2(x) + u_0m^4(x) + hm(x)\right]$$
We will ...
0
votes
4
answers
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Does the vacuum really have infinite energy density?
I said: As far as I understand it quantum field theory says that the vacuum has an infinite energy density.
r/AskPhysics RedditorAbstractAlgebruh said: But wouldn't that be due to the way we do the ...
- 5,925
12
votes
1
answer
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Effective Field Theory vs Ostrogradsky
The low-energy effective description of a given QFT is an expansion of the form
$$
\mathcal L_\mathrm{IR}\sim\sum_{n,m} \lambda_{n,m}\phi^n\partial^ m\phi
$$
where we include all terms that are ...
0
votes
0
answers
105
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What do we take as the energy scale in the $\beta$ function/ running coupling?
So when we renormalise a qft we usually find that the renormalised parameters depend on some energy scale $\mu$.
What explicitly is this energy scale? Is it just the COM energy of that given ...
- 1,933
7
votes
1
answer
2k
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What is the difference between thermodynamic free energies and the Landau free energy?
How and why is the Landau free energy any different from thermodynamic free energies?
It is written on page 140 of Nigel Goldenfeld's book Lectures on Phase Transitions and The Renormalization Group ...
- 11.8k
0
votes
1
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Landau theory; irrelevence of the lattice strcture?
In Ginzburg-Landau theory the derivative terms in the free energy depend on the structure of the lattice1. That said when looking at e.g. the O(3)-model the only derivative term kept is
$$(\vec \nabla ...
1
vote
0
answers
55
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renormalization and relativity
So my issue is the seemingly paradoxical view in QFT that we renormalize energy with the argument that energy is relative and only a convenience introduced for calculations originally while relativity ...
- 637
14
votes
2
answers
2k
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What is precisely the energy scale of a process?
Coupling constants run with the energy scale $\mu$. But what is exactly this energy scale. My question is, if I have a physical process, how do I compute $\mu$?
- 6,067
8
votes
1
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What is energy in $z \neq 1 $ theories?
In a critical theory with dynamical critical exponent $z \neq 1 $, which amongst frequency, $\omega$, and dispersion, $E(\vec{k})$, may be referred to as ''energy''? I'm confused about this since in ...
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