Effective field theory Definition and 19 Threads

I had two rather long questions about the recent programe on searching for UV-completions of EFTs through positivity bounds (that is, UV completions that obey fundamental constraints given by QFTs: unitarity, locality, causality, analyticity and Lorentz invariance) Question #1: The EFT-hedron...

In a podcast episode, Sean Carroll discusses Wilson's renormalization group and effective field theories, arguing how Wilson showed that upper-level theories are not discoverable from effective field theories at low energy. Excerpt: In what sense is this true? Does that mean that no matter how...

Where does the ##m## in ##(3.2)## come from? It doesn’t seem to enter anywhere in Feynman rules for the given diagram

I had been studying this topic from various textbooks and review articles and I am confused about some terminologies and concepts. The question I have typed in this PDF. [Mentor Note -- Added screenshot of PDF contents]

Have a look at O5 & O6 in Eqtns(5.4) . Why is there a (V+A) ? (V+A) contains the projection operator which projects out the right Weyl from a Dirac spinor. As per the Feynman rules of electroweak theory, there is a (V-A) assigned to each (Dirac) spinor-W boson vertex because W only couple to...

I have included here the screen shot of the page I am referring to.I am unsure of how this non-local Lagrangian of Eqtn(32.68) has been constructed. Have they just integrated the interaction Lagrangian densities over two different sets of points (x & y) ? If so, then why is there no P_L in...

Assume that I have the Lagrangian $$\mathcal{L}_{UV} =\frac{1}{2}\left[\left(\partial_{\mu} \phi\right)^{2}-m_{L}^{2} \phi^{2}+\left(\partial_{\mu} H\right)^{2}-M^{2} H^{2}\right] -\frac{\lambda_{0}}{4 !} \phi^{4}-\frac{\lambda_{2}}{4} \phi^{2} H^{2},$$ where ##\phi## is a light scalar field...

My idea was to consider first the structure of the matrix element and to see if there are any possible constraints that we could use for parametrization. If I am not mistaken, we are dealing with the hadronic decay governed by QCD which conserves parity. Since we have a derivative operator...

I would like to know where one may operate with tensor quantities in quantum field theory: Minkowski tensors, spinors, effective lagrangians (for example sigma models or models with four quark interaction), gamma matrices, Grassmann algebra, Lie algebra, fermion determinants and et cetera. I...

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...

Years ago after reading Ch. 12 of Peskin and Schroeder (and the analogous discussion in Zee), I thought I fully understood the modern Wilsonian view of renormalization, and how it explains why non-renormalizable field theories still have meaning/predictive power at energies well below the...

I have a question about the use of trace in QFT in general - more specifically the use of trace in the lagrangian in the effective theory concerning chiral symmetry in QCD. I am slowly trying to get a hang of everything, and most things i am able to calculate, but i still have som very specific...

Hi everyone, I'm approaching the study of EFT but I'm facing some problems. While in QFT usually we want renormalizable theories, in EFT we don't want this costraint anymore and this opens up space for a lot more terms in the Lagrangian. My problem is that when we want to calculate amplitudes...

http://arxiv.org/abs/1409.0868 Holomorphy without Supersymmetry in the Standard Model Effective Field Theory Rodrigo Alonso, Elizabeth E. Jenkins, Aneesh V. Manohar (Submitted on 2 Sep 2014 (v1), last revised 6 Nov 2014 (this version, v2)) The anomalous dimensions of dimension-six operators in...

Arkani-Hamed, Dubovsky, Nicolis, Trincherini, and Villadoro argue in section 2.2 of A Measure of de Sitter Entropy and Eternal Inflation that the effective field theory description of black hole evaporation fails after a time t[SIZE="1"]ev, even though the curvatures are small. Almheiri...

What is an effective field theory?? Yeah, there is many information on Internet, but it is a complicated level, they speak about cut-off, top-down, series development without justify limit the coefficients of ignored terms in the development. Aren´t there a simple (but rigurous) explanation...

I have just read my first course on Quantum Field Theory (QFT) and have followed the book by Srednicki. I have peeked a bit in the books by Peskin & Schroeder and Ryder also but mostly Srednicki as this was the main course book. Now, I have to do a project in a topic not covered in the course...

Hi, could anyone explain to me why in effective field theory (as in ch29 srednicki), you look at diagrams with only k<\Lambda as external lines and k>\Lambda for your interal lines? why do these diagrams with say, 6 external legs of this type, equate to the constant c_6 say? In previous...

Can anyone tell me if this is the basic concept behind effective field theories: 1) You begin with your original Lagrangian, and you want to construct an effective Lagrangian out of it. 2) You redefine your coupling constants in your original Lagrangian so that they include the integral...