Field theory Definition and 523 Threads

Summary:: What are the relevant mathematics/ mathematical physics courses for studying quantum field theory and statistical field theory? I'm a physics undergraduate currently in my junior(third) year, thanks.

Trying to better understand quantum field theory, I've read that particles are created when it becomes an exitation of its quantum field. Would it then be right to think of a particle as the manifested kinetic energy of its field?

I'm looking for a book that describes the quantum field theory without going deeply in the theory with formulas or complex description of the mathematics under the theory. I know that this theory is really complex and it needs a deep knowledge of quantum physics in order to be understood. But...

In particular I would like to have a resource for the relation between group theory, crystal field symmetries and breaking of degeneracies of orbitals. I've taken a graduate condensed matter course and graduate quantum mechanics courses. I have some basic knowledge of group theory but can learn...

Hi. Are these two books complementary, or do they have too much in common? https://www.amazon.com/dp/1107034264/?tag=pfamazon01-20 www.amazon.com/Quantum-Field-Theory-Standard-Model/dp/1107034736/ My problem is that I still don't quite understand the difference between university courses in...

I have a problem about Heisenberg model.When applying mean field approximation,why does the average of spin flip terms be zero(<S+>=<S-> = 0 )? Thanks

Summary: Does the "problem of time in quantum mechanics" go for Lorentz-invariant quantum mechanical theories like QED? Everything I read about "the problem of time in quantum mechanics," i.e. absolute time in QM clashing with relativity's relative time coordinate and relativity of...

hi, I'm currently taking a classical field theory class (electromagnetism in the language of tensors and actions and etc) and we have just encountered the gauge symmetry, that is for the 4 vector potential we can add a gradient of some smooth function and get the same physics (if we take Aμ →...

I have been browsing this book, and it seems a quite interesting one. The traditional Statistical Mechanics is quite traditionally treated (so only average) but then, the linking of Statistical Mechanics with QFT, and the exact solutions in Conformal Field Theory, are quite nice. But I do not...

Hi everyone! Sorry for the bad english! So, just a quick doubt... Does things collapse from a wave of probability into a quantum field or is the wave in the quantum field the probabilistic wave itself? An example to make it clearer: Suppose we have an atom, it enters an atom interferometer, it...

Hi. I'd like to ask what are the differences between Particle Physics, Quantum Field Theory and the Standard Model. I see these names of physics courses but I want to confirm if I understand the difference. My understanding is that when students learn particle physics in their undergraduate...

Hello everyone,Upon my comment on the insight "Applying for Physics Graduate School - Comments", Mr. Bill (bhobba) suggested that I need to write an individual post regarding my inquiry. I am looking for physics graduate programs (PhD). My senior project/thesis was on classical field theory and...

I am reading Carroll’s Spacetime and Geometry, and I have seen the word “coupled” used multiple times in seemingly different ways. I have gotten the sense that it means some sort of interaction between particles, but Carroll refers to coupling between matter fields and the curvature of...

It is my understanding that in both Classical Field Theory and QFT the Lagrangian must be Lorentz invariant in order for the fields to be considered relativistic. Buy what about the field itself (φ or ψ)? As complex-valued functions of space and time do they also have to be Lorentz invariant...

I studied the work of a nano generator in quantu mechanics. The generator uses the principle of triboelectrics. How does this work in quantum field theory? I think that the electron (wave packet in the field) is in the atom in a small volume because the nucleus inhibits the propagation of the...

This is a topic I've mentioned a few times before. Essentially the structure of matter in quantum gauge field theories is unclear to me. I have no clear question here, just some initial discussion points. So at the first level, it seems a particle based view of quantum field theory is difficult...

Hi , I need to enrich my knowledge in quantum field theory, please refer me to reference books in this branch. Thank's.

I have been reading some papers from G.F. Chew and S. C. Frautschi and they do not even bother to introduce the concept of "Field" when they describe hadron interactions. My impression is that they do not need to because interactions seem to be described by single Regge-trajectories. However...

What is the basic idea and purpose of the thermal field theory? I don't need a full in depth description of it, not at the moment at least. I am just trying to understand how it is relevant in the calculation of angular distribution of temperature of CMB(Comic Microwave Background) over the sky.

Homework Statement $$ L = -\frac{1}{2} (\partial_{\mu} A_v) (\partial^{\mu} A^v) + \frac{1}{2} (\partial_{\mu} A^v)^2$$ calculate $$\frac{\partial L}{\partial(\partial_{\mu} A_v)}$$ Homework Equations $$ A^{\mu} = \eta^{\mu v} A_v, \ and \ \partial^{\mu} = \eta^{\mu v} \partial_{v}$$ The...

How work AC/DC current in Quantum Field Theory

Art Hobson said that quanta propagate in space to infinity. (sorry can not give a link)

How work triboelectricity in QFT? Materialists exchange electrons as well as in classical theory?

The Klein-Gordon equation has the Schrodinger equation as a nonrelativistic limit, in the following sense: Start with the Klein-Gordon equation (for a complex function ##\phi##) ## \partial_\mu \partial^\mu \phi + m^2 \phi = 0## Now, define a new function ##\psi## via: ##\psi = e^{i m t}...

Homework Statement Hi, I am looking at the attached question, parts a) and b).Homework Equations The Attempt at a Solution so for part a) it vanishes because in the ##lim \epsilon \to 0 ## we have a complete derivative: ## \int d\phi \frac{d}{d\phi} (Z[J]) ## for part b) we attain part a)...

Hello all, Can you tell me what is the best book to study QFT when you are thinking to follow a PhD in cosmology (Dark energy, scalar fields, extension to GR, string theory).

Besides the Feynman lectures on gravitation, I'm looking for modern and complete treatments of the topic of classical gravitation as a field theory in flat space time. Any suggestion?

I'm self-studying field theory and trying to solidify my understanding of index manipulations. So I've been told that there is a general rule: " If the index is lowered on the 'denominator' then it's a raised index". My question is whether this is just a rule or something that can make sense...

Quantum mechanics replaces the classical concept of cause and effect with probabilities. The best explanation: it just is. While the Heisenberg Uncertainty Principles hold in quantum field theory does QFT offer a different interpretation to this concept? Or at least mitigate some of the...

[Moderator's note: This thread is spun off from another thread since it was dealing with a more technical point that is out of scope for the previous thread. The quote that starts this post is from the previous thread.] I feel the same about transformations of Dirac matrices and Dirac field...

The theory of electroweak temperature says that when you have a plasma of particles at energy above the electroweak phase transition (100 GeV). The Higgs field would turn from nonzero vev to zero and the electroweak forces would unite and the electroweak bosons would become massless. What...

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

Homework Statement Derive, using the canonical commutation relation of the position space representation of the fields φ(x) and π(y), the corresponding commutation relation in momentum space.Homework Equations [φ(x), π(y)] = iδ3(x-y) My Fourier transforms are defined by: $$ φ^*(\vec p)=\int...

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Interacting Quantum Fields Continue reading the Original PF Insights Post.

I am reading Polchinski's review on AdS/CFT https://arxiv.org/abs/1010.6134. I have a very simple question, and please help me out. Thanks in advanced. The question abou formula (3.19) The scalar effective bulk action is given by $$ S_0=\frac{\eta}{2}\epsilon^{1-D}\int d^Dx \phi_{\rm cl}...

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Free Quantum Fields Continue reading the Original PF Insights Post.

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

<< Mentor note -- posts broken off from an Insights comment thread >> [/color] Ok, this is where I show my ignorance, but all this is theoretical and why I get lost with these academia discussions. Time is just a mathmatical construct to measure the motion of two or more objects relative to...

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Gauge Fixing Continue reading the Original PF Insights Post.

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Reduced Phase Space Continue reading the Original PF Insights Post.

Quantum mechanics does a good job in describing the hydrogen atom. Are there any views either mathematically or conceptually in describing the hydrogen atom?

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...

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Gauge symmetries Continue reading the Original PF Insights Post.

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

Greg Bernhardt submitted a new PF Insights post Mathematical Quantum Field Theory - Phase Space Continue reading the Original PF Insights Post.

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

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

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

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

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