Field theory Definition and 523 Threads

Hi all, I'm a bit confused about ferromagnetism (and I've come to realize that I'm not the only one)! I'm currently studying electrodynamics and field theory in general to solidify my understanding of such, but permanent magnets and ferromagnetic materials seem to be often ignored in the...

Non Commutative Cross-Section hello, this is my first post here, i have searched the web but i didnt find what i am looking for,so i hope i find it here. i am looking for the formula of the cross section of compton scattring in the non commutative space-time .

I have just started reading up on mean field theory. Any book you could refer??

I am to produce a research presentation for a class of Masters' physics students on the casimir force, going via a detailed treatment of the vacuum effects in conducting cavities, going on to explain some real phenomena and applications. What I am after is a good introductory text on quantum...

Homework Statement A. Zee Quantum Field theory in a nutshell, p. 31. There is painfully little explanation on this page. I'm okay with the action: S(A) = \int d^4 x \mathcal{L} = \int d^4 x\{ \frac{1}{2}A_\mu [(\partial^2 +m^2)g^{\mu \nu}-\partial^\mu\partial^\nu]A_\nu + A_\mu J^\mu \}...

Quantum field theory or particle physics what first? Hi at present I am confused whether i should try obtining a firm conceptual understanding of QFT before jumping to particle physics or whether aa very brief overview of QFT is enough ?

Since I'm very interested in General Relativity and Quantum field theory, I'd like to start a doctoral program abroad after my master study (I'm studying in Switzerland and will get my master degree in approximately 1.5 years). I was surfing around in the internet and found for example the...

I was wondering what to read for quantum field theory and in what order if applicable: I have "qft in a nutshell" by zee, "intro to qft" by peskin, "qft" by rydern, and "advanced qft" by sakurai.

What does it mean to say to say that the electroweak interaction is described by a gauge field theory based on the SU(2)_{L}\timesU(1)_Y symmetry group? I know that SU(2) is a group of unitary matrices and U(1) is the circle group but I don't really see what the sentence means. I haven't taken...

I have recently been studying Gregory Chaitin's "algorithmic information theory" for a school project. It describes the complexity of mathematical objects by the size of the smallest Turing machine program capable of computing them (in bits). It also defines a "random" object as one with an...

Hi, I am curious about the following and I aim these questions to the people who do general relativity and uantum field theory over there. What is the difference between field theory of general relativity and field theory of quantum field theory? Is the former only for study of gravitation...

I was wondering if anybody knew any good books that give an easy to understand quantum field theory. I am talking from a view point of a person who has read the third volume of the feynman lectures and quantum mechanics demystified. if this is not enough to even start a easy to understand...

I know that the vacuum in Quantum Field theory is not empty, but sometimes I find some people say that the particles are created from nothing because they are created from the vacuum , are those people expression a misleading?

I'm currently trying to pre-familiarise myself with the course on lagrangian dynamics I'll be taking in the upcoming year, by reading the course notes supplied. I'm somewhat getting the hang of it, but I could really do with some more indepth discussion about the whys and wherefores. Could...

On this forum, quantum field theory (QFT) is a part of this subforum (Quantum Physics), while particle physics is a subject of another forum. These two topics - QFT and particle physics - are clearly separated. On the other hand, most textbooks on QFT are also textbooks on particle physics...

I have noticed that questions about this subject get either ignored or receive some confusing answers. So I decided to write a "brief" but self-contained introduction to the subject. I'm sure you will find it useful. It is going to take about 13 or 14 post to complete the work. Be patient with...

In my recent paper http://xxx.lanl.gov/abs/0705.3542 entitled "Is quantum field theory a genuine quantum theory? Foundational insights on particles and strings" I argue the following: Practically measurable quantities resulting from quantum field theory are not described by hermitian...

Homework Statement I'm trying to find a commutative ring, not a field, who's only ideals are {0} and itself. Homework Equations Definition: A subset of a ring R is an ideal if it is a subring of R and is closed under multiplication by elements of R. The Attempt at a Solution I...

Does anyone here know of a good site explaining d_{xy}, d_{x^{2}-y^{2}}, etc. orbitals?

http://sites.google.com/site/winitzki/" a draft of an introductory textbook on quantum field theory in curved spacetime - free quantum fields in expanding universe, Unruh effect, Hawking radiation, also Casimir effect and some basic stuff on path integrals and effective action. The book is not...

I don't understand how Peskin & Schroeder can evaluate the integral on page 27 by having the real axis wrapping around branch cuts just like that. The picture of the contours are on page 28.

hi everyone, There are so many books about QFT, but what is in your oppinion the best book to learn quantum field theory?

Hi all. I'm running a thread in the Philosophy section about rules of the universe etc but I'm stuck on a fundamental question which probably only a current quantum mechanics expert can answer. In essence do the most current iterations of QF theory maintain that the ultimate and irreducible...

Homework Statement Show Q(\sqrt{p},\sqrt{q}) = Q(\sqrt{p} + \sqrt{q}) Homework Equations p and q are two different prime numbers The Attempt at a Solution I can show \sqrt{p} + \sqrt{q} \in Q(\sqrt{p},\sqrt{p}) I have trouble with the other direction though, i.e...

Can anybody explain this thing that is "spin" to me? I basically came across it whilst researching how we know about the deep earth. Mineralogists and crystallographers talk about this thing called spin, quantum physicists also talk about spin; yet as far as I am aware they are they are not...

Hi,there! I want to study Quantum Field Theory but I don't know what book to use! I have a rather good background in quantum mechanics and electrodynamics, and I probably can gain access on the following books: Brown L.S. : "Quantum Field Theory" Peskin and Schroeder : "Introduction to Quantum...

Hi, I`m a noob at physics, but I have a question. does the Unified Field Theory state that when found, it`ll be able to predict the future? Therefore everything in the universe is predetermined, and so you can't change anything. Is it true? Thanks

I'm interested in teaching myself QFT. My BSc is in Mathematics and Physics, so I probably have a stronger mathematical background than the average physics graduate. However, I'm assuming it's almost certainly not good enough. What I am looking for is a way of sensibly teaching myself the...

U = e^{\frac{1}{2} B} = \cos(\frac{1}{2} \theta) + b \sin(\frac{1}{2} \theta) we can then write: U = e^{\frac{1}{2} \theta b} = \cos(\frac{1}{2} \theta) + b \sin(\frac{1}{2} \theta) And if we rely on Joe's expression, r=\frac{\theta}{2} (rotor angle is always half the rotation): U = e^{br}...

Let be the nuclear reaction: ee \rightarrow e+e+ (if not possible a similar one) Of course we have 2 states |A> with 2 electrons and |B> with two "positrons"..if we wished to compute the transition probability we should know: <B|S|A> where "S" is the S-Matrix..my question is..is...

Here is a set of 100-some slides for a talk Daniele Oriti gave in September 2005 called The Group Field Theory Approach to Quantum Gravity http://www.phy.olemiss.edu/GR/qg05/talks/oriti.pdf The talk was given at this conference in Sardinia: http://www.phy.olemiss.edu/GR/qg05/ This is the...

Field theory papers---Hossenfelder Konopka Magueijo Recently I noticed several papers exploring what QFT or quantum physics of some related sort might be like with a small invariant length scale. these are by young researchers: a postdoc, a PhD grad student, a young faculty. I can't...

Questions on Freidel's "Group Field Theory (hep-th/050516)" In Laurent Freidel's general description of group field theory, http://arxiv.org/abs/hep-th/0505016" , which I am studying as preparation for the paper on getting quantum dynamics out of kinematics which was recommended by Helge Rose'...

As I read in my quantum mechanics book the delta function is sometimes called the sampling function because it samples the value of the function at one point. \int {\delta (x - x')} f(x')dx' = f(x) But then I opened a quantum field book and I found equations like that: \phi (x) =...

if we know that the divergent series in perturbation theory of quantum field theory goes in the form: \sum_{n=0}^{\infty}a(n)g^{n}\epsilon^{-n} with \epsilon\rightarrow{0} then ..how would we apply the renormalization procedure to eliminate the divergences and obtain finite...

Hi, I'm a little confused about the nature of fields in quantum field theory. I sometimes see people make reference to an "electron field" or other matter field of some sort, and in my understanding, in quantum field theory, ALL the different fundamental particles can be represented as...

I see this term a lot. I know its something to do with a group but I'm not too sure what it is. Also - how does a representation (mathematical concept) translate into particle physics concept.

Can anybody recommend some good quantum field theory books for introduction to the subject? I am already familiar with some of the techniques from applications to statistical mechanics, but I would like to see them in a different context.

Greetings, I stumbled across two question that I have no idea on how to answer them. 1) The interaction term in a scalar field theory is -\frac{\lambda}{4!} \phi^4 Why should lambda be positive? (they say look at the energy of the ground state...) 2) Write down the Feynman rules for...

Why do theories of superconductivity need to be quantum field theories with 2nd quantisation? Isn't first quantisation enough?

Mar 29 (from my journal site) "What we know. The force of gravity is much greater here on the face of the Earth opposed to the far upper atmosphere of our planet. Yet it is around a planet that we typically observe and associate with the bending of light. Here on the face of the Earth it...

Greetings--I have a few questions from An Introduction to Quantum Field Theory by Peskin and Schroeder. Note: I'm not sure how to construct the contraction symbol using \LaTeX, so instead I will use the following cumbersome convention: \overbrace{\psi(x)\overline{\psi(y)}}=S_F(x-y), they...

I know that Einstein dedicated the end of his life working on this topic. Do anybody knows what exactly did his theory was about, and if it is connected somehow with modern unified therories? Thanks.

At my physics faculty there is this magazine that comes out once every three months. I wrote an article about GR for it. Introducing not only the concepts but also some mathematics. I explained the field equations and derived some implications of the Schwarzschild metric. I could do this because...

I need some suggestions and/or corrections if I understand this correct? My questions are based on the book by Mandl and Shaw. Conserved currents are based on Noethers theorem and directly connected to spacetime and field transformations (rotations, translations, phase, ...). One can...

Unified field theory who try to unify the nuclear forces, with gravity and electromagnetic forces; this are low level energies and forces related to matter. Energies knowing in Yoga are missing. More about energies on my website: http://knowledge.shorturl.com

What are the flaws with this theory? http://www.gravitywarpdrive.com/NGFT_Chapter_8.htm :eek: :eek: :eek:

Hello All, Hendrik van Hees just started a qft course. Here's his announcement: We just started an online qft theory course, reading along Zee's textbook. Soon, it will be provided as a an online course at the supersymmetry web page: http://www.superstringtheory.com/ Since the...

One question has disturbed me long time, I don't know the distinction between quantum electrodynamics and quantum field theory. By the way, which quantum field theory or quantum electrodynamics textbook is prefer?

In short, the question is, how is the position operator related to the position-parameters of a quantum field ψ(x)? For instance, consider a quantum-mechanical state of two particles |Ψ>. This can be expanded in terms of the position eigenstates |x1,x2> to give the position representation...