Field theory Definition and 523 Threads

Hi, I am studying Peskin's An Introduction To Quantum Field Theory. On the beginning of page 284, the authors say We can turn the field \phi_S(x_1)|\phi_1\rangle=\phi_1(x_1)|\phi_1\rangle. I tried hard to prove this relation but still can't get it right. Could anyone give me some hints? Thanks.

I am trying to understand the proof of Theorem 6 in Chapter 13 of Dummit and Foote. Theorem 6 states the following: (see attachment) ===================================================================================== Theorem 6. Let F be a field and let p(x) \in F[x] be an irreducible...

Hey all, I'm not sure if this belonged in the physics or engineering forum, but here's the question: has quantum field theory been applied to any engineering disciplines yet? I know quantum mechanics has been used extensively in electrical engineering and materials science/engineering. I also...

Hey, I am looking for a book / paper / pdf which covers things like -maxwell EM field theory -gravitational field theory -variational calculus / principle of least action -lagrangian mechanics -basic scalar fields / wave equations -field equations out of lagrangians -maybe some basic...

hi i read some text about causality and determinism, but i can't exactly distinguish between them. what's really difference between them? does not quantum mechanics respect one of them? i read this phrase in article of S.Carlip about quantum gravity "Quantum field theory includes...

Author: Robert D. Klauber Title: Student Friendly Quantum Field Theory Amazon Link: https://www.amazon.com/dp/0984513922/?tag=pfamazon01-20 (submitted by elfmotat)

Hello All, I am quiet new to the subject, so if anybody can help me. The four fundamental forces of nature, gravity, strong, weak,electromagnetism. Through weak force, all the electrons, protons and neutrons interact with each other. An attempt was made late in the 20th.century to unify...

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...

Hey everyone, I've got a question. I've been doing a lot of reading about Quantum Field Theories lately, and watching a lot of lectures about field theories in general, and I'm wondering, is Special Relativity a field theory? For instance, in this article and the lecture accompanying...

The notion field of Quantum Field Theory is deduced from the combination of Quantum Mechanics and Special Relativity.The local characteristic of field is led from Cluster Decomposition Principle. String Theory is also a combination between Quantum Mechanics and Relativity Theory.Then I wonder...

When expanding a function (for example the determinant of the space-time metric g) as a functional of a perturbation from the flat metric ##h_{\mu \nu}##, i.e. ##g_{\mu \nu} = \eta_{\mu \nu} + h_{\mu \nu} ## i would think that the thing to do is to recognize that ##g_{\mu \nu}## and thus also...

Gravitation is described on one hand as curvature of space in the presence of matter. It is also described as a field acting through gravitons on matter. How can the two views be reconciled?

The 'partition function' in QFT is written as Z=\langle 0 | e^{-i\hat H T} |0\rangle, but I'm having a difficult time really understanding this. I'm assuming that |0\rangle represents the vacuum state with no particles present. If that's the case, and the Hamiltonian acting on such a state would...

We usually talk about good books, but we rarely talk about bad books. And that is good. But sometimes, we find that some book is so bad, so really bad, that we strongly want to tell this to the others. So I open this thread to inform others about science books which you find so bad that it...

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've been introduced to ligand-field theory lately and was then wondering what roles f orbitals play in the magnetic properties of elements and alloys. Apparently f orbitals behave oddly in that they hybridize in weird ways because they're so large and that the crystal field actually affects the...

So yet we have the Standard Model which tries to explain and unify the 4 fundamental forces or atleast 3 for now since the gravity is not quite well understood in particle physics.So people search for a theory of everything which unifies all forces and yet we didn't found any good theory as...

In special relativity we have the relation that for a free particle E^2 = \vec p^2 + m_0^2 and that also hold in relativistic free field theories (free Klein-Gordon etc) where one can show that we have a completeness relation 1 = \int \frac{d^3 \vec p}{(2\pi)^3} \frac{1}{2E_{\vec...

Hi! I'm trying to follow the video lectures of the course 'Quantum Field Theory II' by Francois David given at the Perimeter Institute PSI programme, but it would be nice to have some notes or a book which were similar to the lectures. I am especially interested in the part on Wilsonian...

"Mysticism in Quantum Mechanics": the forgotten controversy by Juan Miguel Marin, Harvard, Eur. J. Phys. 30 (2009) 807 - 822. How's that Mr. Mentor? Or are you going to censor this post also? Small-minded world physicists, like the 'flatlander-earth-centric' astronomers of old better take...

Is there a discussion on this board of the possibility that consciousness is the missing link in a true unified field theory? Or is this considered heresy, not mainstream, a homework question, too out of the box or just a confounding question as everyone with an open mind here knows that it's...

Hi! I'm in a master course in theoretical physics and enjoying a lot to learn about Quantum Field Theory (QFT)! So I was thinking doing a PhD related do QFT. What are the best places to work on QFT? Thanks a lot!

A circularly polarized electromagnetic wave can be thought of proper combinations of orthogonal linear polarized waves, and a linear polarized wave can be thought of proper combinations of left and right circularly polarized waves. It seems one type of wave is no more fundamental then the other...

First of all sorry for my off-topic question here. I'm a computer science student, who has a high interest in mathematics (especially algebraic geometry), and physics (especially quantum mechanics, quantum field theory). For this semester I'm supposed to create to applications, from which one of...

Author: Robert E. Collin Title: Field Theory of Guided Waves (IEEE Press Series on Electromagnetic Wave Theory) Amazon Link: https://www.amazon.com/dp/0879422378/?tag=pfamazon01-20 Prerequisities: Calculus/Engineering Mathematics (introductory complex analysis and linear analysis)...

Author: Michele Maggiore Title: A Modern Introduction to Quantum Field Theory Amazon Link: https://www.amazon.com/dp/0198520743/?tag=pfamazon01-20

Author: A. Zee Title: Quantum Field Theory in a Nutshell Amazon Link: https://www.amazon.com/dp/0691140340/?tag=pfamazon01-20

A question I'm sure I've seen asked here and/or elsewhere is why there doesn't seem to be any classical force corresponding to the weak interaction. I came up with the following, and am wondering whether this seems correct and satisfying to others. Basically, being able to write down a...

Author: Bo Thide Title: Electromagnetic Field Theory Download Link: http://www.plasma.uu.se/CED/Book/ Prerequisities: Contents:

Author: Michael E. Peskin (Author), Dan V. Schroeder (Author) Title: An Introduction to Quantum Field Theory Amazon Link: https://www.amazon.com/dp/0201503972/?tag=pfamazon01-20 Prerequisities: Contents:

I need to derive the euler-lagrange equations for the following non-local lagrangian density for a complex scalar field ψ \mathcal{L} = \partial_{\mu}\psi^* \partial_{\mu}\psi - \lambda \int dy\, f(x,y) \psi^*(y) \psi(y) where λ is the coupling constant, f is a certain real-positive valued...

I haven't taken a course in qft yet, just looking ahead to see what's to come, and so far things are not looking good, I read the firet few chapters of qft in a nutshell, and jesus christ what is this stuff, where are the postulates? The equations of motion? How do I even do these crazy path...

Can you suggest any source available on internet which may be particularly helpful for those studying/brushing up knowledge of classical or quantum field theory without help of any teacher or friend? Some calculations are at first not so straightforward and there are many types of calculations...

Dear Forum, I would like to understand what the origin of spin 1/2 is. I read in Feynman's lectures that the origin is related to quantum field theory. I know nothing about quantum field theory. Is there an easy explanation? Thanks Cabrera

Hey everyone, I would like to first point out I am not a biology major in any way...I am a physics major, with a ever increasing interest in neuroscience. I am trying my best right now to find ways that I can incorporate my physics knowledge to the brain. Right now I am trying to...

Hi, I'm a masters student trying to apply DMFT to problems involving transport in strongly correlated systems. I have a cursory understanding of the physics behind the Hubbard model, which is to say, I have spent some time with it in a quantum many body theory course. However, I now want to...

Hi! I'm used to integrating over infinite spaces when working with QFT so far, but in an exercise I stumbled across a statement that \int_V d^3x e^{-i \vec x \cdot (\vec p - \vec p')} = V \delta_{\vec p \vec p'} It is clear that this is okay when p = p', but it does not seem to make sense...

Is Magnetic field conservative or non-conservative in nature, I have searched online regarding this, it seems to be a divided house, MIT professor Walter Lewin demonstrated that it is non-conservative using an experiment, but still many arent convinced with the way experiment was conducted...

I'm a computer science and engineering student, who has recently developed interest about quantum computers. I can understand that quantum computers are totally linked with quantum mechanics. But I would like to learn whether there is any relation between quantum computing and quantum field...

I plan to study from Peskin and Schroeders book if it helps, I just need to know what topics I need to study and it would be greatly appreciated if someone could tell me what books are good on the subject, I have a limited budget however and if I could get a single or only 2 or 3 books covering...

We would like both 4-momentum and angular momentum to be conserved in a field theory such as QED. My understanding is that in the case of 4-momentum, there are two different descriptions of the same theory. (1) We can impose conservation of 4-momentum p at each vertex, which requires that...

In field theory: [H,P]=0 So shouldn't that mean there can be no scattering? If you have momentum state |p1p2> then it is an eigenvalue of P with eigenvalue p1+p2. But it should be a simultaneous eigenstate of H too, so e^(-iHt)|p1p2>= |p1p2> up to a phase factor. But in general...

Hello, I have to give a presentation on an application of electromagnetic field theory of my choosing, and I was wondering if anyone had any suggestions that might be more interesting than the ones that have been suggested. It's for a 2nd year university level physics (E&M) course, so the...

The weak force was not discovered until 1953 or thereabouts so that pretty much made Einstein's attempt to unify all forces an impossible task. Does anyone know how much time he wasted on trying to find a unified field theory? Other than write a paper on gravitational lensing and the EPR paradox...

If some one could please explain what a field is in as much detail as possible please. don't be shy I love a challenge. My understanding is that a field is a precise area surrounding its source. depending on the field you get different effects. For example with the higgs field, the higgs...

Recently i am reading A.Zee's Quantum Field Theory in a Nutshell 2nd Edition. there is a equation that i can not derive by myself. I suspect its correctness. <k1k2|exp(-iHT)|k3k4>=<k1k2|exp(i∫dxL(x))|k3k4>, where the L(x) on the RHS is an operator function of space-time. This equation...

Hello Everyone! I have a problem I am solving through a self study project from Lowell Brown's book entitled: Quantum Field Theory". It is a math question (basically) on recursion relations. Homework Statement The variational definition gives us the relation: det[1-λK] = exp{tr...

Personally, I am interested in Topological Quantum Field Theory. And now I am battling against Quantum Field Theory. I am not sure how much Quantum Field Theory is needed to do Topological Quantum Field Theory. And I am not sure what should be the mathematical pre-requisites of Topological...

Ginsparg "Applied Conformal Field Theory" I have some questions concerning the first two chapters of Ginsparg's text on CFT, which can be found here 1. In equation (2.1) primary fields of conformal weight (h,\overline{h}) are introduced as fields that transform the following way...

Now, I must preface this by saying that my understanding of QFT is limited, and my understanding of GR is even more so. Nevertheless, I was reading about the No Hair Theorem, and it seemed to me to be suggestive of the indiscernibility of Quantum Particles. Obviously, for a macroscopic black...