1. G

    A Is renormalization the ideal solution?

    Quantum gravity theories and GUTs are nonrenormalizable theories, but does this actually mean that these theories must be flawed, or does it mean that renormalization must be a flawed concept, or is this not actually a problem? If it is impossible to produce a renormalizable quantum gravity...
  2. R

    I Young physicist in seek of guidance

    Is there anyone on here who could help me fill in my gaps in quantum field theory up to renormalization? I know how to canonically quantize a theory and how to use scalars (spin 0), vectors (spin 1) and spinors (spin 1/2) but lack more advanced knowledge like renormalization which I could...
  3. M

    Beta-function for the Gross-Neveu model

    In the Peskin & Schroeder textbook, the ##\beta## function for the Gross-Neveu model is discussed in problem 12.2. After computing it, I have tried checking my results with some solutions found online. My problem is that they all disagree among each other (something quite recurrent for this book...
  4. A

    A Renormalization (Electron self energy)

    Hello everybody! I have a big question about the renormalization: I do not understand why the "renormalization condition" is to impose the tree level result. Now I will explain it better. Let's take, for example, the electron self energy. The tree-level contribution is the simple fermionic...
  5. A

    On-shell renormalization scheme

    Homework Statement Show that, after considering all 1 particle irreducible diagrams, the bare scalar propagator becomes: $$D_F (p)=\frac{i}{p^2-m^2-\Sigma (p^2)}$$ And that the residue of the pole is shifted to a new value, and beomes...
  6. Angel Kld

    A On non-perturbative renormalization and gravity

    If we were to find some way to make the graviton self-interaction easily calculable, would applying non-perturbative renormalization on it seem any promising?
  7. A

    I What is the point of regularization?

    Take for example dimensional regularization. Is it correct to say that the main point of the dimensional regularization of divergent momentum integrals in QFT is to express the divergence of these integrals in such a way that they can be absorbed into the counterterms? Can someone tell me what...
  8. Ken Gallock

    A QED: redshifting light and infrared divergence

    I am looking for some resources describing the following content: A light with wavelength ##\lambda## is propagating in flat spacetime. The light redshifts as its wavelength gets larger and larger. In quantum field theory, this causes an infrared divergence of the field. What I want to know...
  9. ohwilleke

    I Is there new LHC data on coupling constant running?

    Question Has the LHC released any papers or reports on the observed running of any of the three Standard Model coupling constants with energy scale from either Run-1 or Run-2 data (or both data sets)? Last time I looked I couldn't find any data As of January 2014, I had not locate any papers...
  10. ohwilleke

    I Proton Decay At The Highest Possible Energies

    Proton decay has not been observed and has been constrained to be extremely rare in ordinary low temperature situations, if it happens at all (the Standard Model says it doesn't happen at all, because there are no lighter decay products that would not violate conservation of baryon number)...
  11. D

    A Renormalisation: what are the physical observables?

    I'm trying to understand renormalisation properly, however, I've run into a few stumbling blocks. To set the scene, I've been reading Matthew Schwartz's "Quantum Field Theory & the Standard Model", in particular the section on mass renormalisation in QED. As I understand it, in order to tame the...
  12. Urs Schreiber

    Insights Mathematical Quantum Field Theory - Renormalization - Comments

    Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Renormalization Continue reading the Original PF Insights Post.
  13. hilbert2

    A Coupling constants with fractional dimensions

    Most QFT texts, such as Peskin&Schroeder and D. Tong's lecture notes, contain a mention that the renormalizability of an interacting theory requires the coupling constants to have correct dimensions, making scalar fields with ##\phi^5 , \phi^6, \dots## interactions uninteresting. Maybe there are...
  14. A

    I IR divergences and total energies...

    I've done some recent reading on IR divergences (propagators becoming singular, etc.). I believe I understand collinear divergences (to some extent)... but I'm not sure about total energies for (primarily) soft photons. In all scattering experiments, total energy should be conserved - but if...
  15. T

    A Quantum Gravity: Renormalization vs. Effective Field Theory

    In quantum gravity, I get 'mixed signals' as regards renormalizability. My state of confusion is being caused, I suspect, by an incomplete understanding of what is covered under t'Hooft's 1972 proof that non-Abelian gauge theories are renormalizable. ( = Nobel Prize 1999). Specifically, some...
  16. J

    A How are renormalizability and locality connected?

    In his paper Quantum Field Theory: renormalization and the renormalization group Zinn-Justin states: Low energy physics does not depend on all the details of the microscopic model because some RG has an IR fixed point or at least a low dimension fixed surface. Of course at this stage the next...
  17. J

    A Why do we need to renormalize in QFT, really?

    There are several reasons given in the literature, why UV infinities arise in QFT in the first place. My problem is putting them together, i.e. understand how they are related to each other. So... UV divergences arise and thus we need to renormalize, because: We have infinite number of...
  18. ohwilleke

    I Pole Masses of Light Quarks

    The pole masses of the heavy quarks (c, b and t) are relatively well defined in QCD (i.e. the solution of m²(p²) = p² extrapolated using the beta function and the available data from other values of µ usually obtained based upon model dependent decompositions of hadron masses that include these...
  19. Kfir Dolev

    A Renormalization Scheme Dependence of Vevs

    Is the one-loop corrected vacuum expectation value of a field renormalization scheme independent?
  20. I

    Scalar QCD renormalization

    Hello all, I hope you can give me a hand with a QFT homework I'm working on. We are to compute the beta equation of a Non-abelian SU(N) theory with: Complex scalars (massless), bosons, ghosts. My question is referring to the Boson self-energy scalar loop correction. 1. Homework Statement We...
  21. T

    A Is Rest Mass a subjective quantity?

    The Electron Rest Mass is considered as a fundamental constant of nature. In relativistic Quantum Field Theory, in contrast, divergences arise. In order to deal with these divergences, one uses renormalization. According to this renormalization, the 'macroscopic' parameters of the lagrangian...
  22. unknown1111

    A Computing the pole mass from a given MS mass?

    Given a Yukawa coupling as a function of scale and a vev, how can I compute the corresponding pole mas? Understandably most paper explain how from a measured pole mass one can compute the running mass, for example, Eq. 19 here. However I want to compute the pole mass from the running mass. In...
  23. unknown1111

    Top quark mass mt at energy scales μ<mt?

    Does it make sense to talk about the top mass at energies below mt, although in all processes the corresponding energy scale is above mt because of the rest mass energy of the top quark? Using an effective field theory approach, the top quark decouples at energies below the top quark mass and...
  24. O

    Renormalization of Bound States in QFT

    Hi, I am about to work on the problem of trying to find a renormalization program for bound states in QFT. Any suggestions/advice on where to start would be much appreciated.
  25. M

    Asymptotic freedom requires perturbative renormalizability?

    I have read many times that a theory (such as gravity) that contains couplings with negative mass dimensions cannot be asymptotically free. Does anyone have a reference that proves that that's the case? The argument is usually just that the coupling grows with energy, as seen in the...
  26. Giuseppe Lacagnina

    Inverse fields?

    Possibly very silly question in QFT. Consider the Lagrangian for a scalar field theory. A term like g/φ^2 should be renormalizable on power counting arguments. The mass dimension of g should be 2 (D-1) where D is the number of space-time dimensions.Does this make sense?
  27. H

    Error in Srednicki renormalization?

    On page 164-165 of srednicki's printed version (chapter 27) on other renormalization schemes, he arrives at the equation $$m_{ph}^{2} = m^2 \left [1 \left ( +\frac{5}{12}\alpha(ln \frac{\mu^2}{m^2}) +c' \right ) + O(\alpha^2)\right]$$ But after taking a log and dividing by 2 he arrives at...
  28. H

    ##\overline{MS}## in scalar theory references

    Does anyone know any good references for discussion of ##\overline{MS}## theory in phi^4 theory?
  29. P

    Counterterms in self-energy diagram

    I guess my question is pretty basic, and following a procedure in the textbook by Lahiri and Pal. You can see the relevant pages at On eqs. (12.84)-(12.86). I don't see how to get from (12.85) to...
  30. M

    Qualitative explanation of scale dependence

    Hi all -- can anyone offer a qualitative explanation of why it is that couplings run with the energy in *relativistic* quantum theory, and not in non-relativistic? Some insight here would be much appreciated. Thanks.