Tagged Questions
2
votes
0answers
51 views
Helicity for Zero Rest Mass Field Equations
I'm trying to reconcile the usual definition of the helicity operator, namely
$$ h = \hat{p}.S$$
with the definition of a massless helicity $n$ field as a symmetric spinor field $\phi^{A\dots B}$ ...
1
vote
1answer
131 views
A classically trivial quantum field theory of electromagnetism
Presumably there is a field theory of electromagnetism that classically gives trivial equations of motion, but when quantized shows interesting topological phenomena. I am talking about the Lagrangian ...
1
vote
1answer
169 views
What is the mathematical background needed for quantum physics? [duplicate]
I'm a computer scientist with a huge interest in mathematics. I have also recently started to develop some interest about quantum mechanics and quantum field theory. Assuming some knowledge in the ...
3
votes
1answer
213 views
Klein-Gordon inner product
Studying the scalar field and Klein-Gordon equation in quantum field theory I came across this definition for the inner product in the space of the solutions of the K.G. equation:
$\langle \Phi_1 | ...
1
vote
2answers
121 views
Stephen Hawking's theory of future backreaction
Several years ago, New Scientist featured an article on a new theory by Stephen Hawking that involved the future having some effect or "backreaction" on the present.
As it would be very tedious and ...
2
votes
3answers
330 views
Dirac equation as Hamiltonian system
Let us consider Dirac equation
$$(i\gamma^\mu\partial_\mu -m)\psi =0$$
as a classical field equation. Is it possible to introduce Poisson bracket on the space of spinors $\psi$ in such a way that ...
1
vote
0answers
70 views
Good introductory books on AdS/CFT correspondence [duplicate]
Possible Duplicate:
Introduction to AdS/CFT
Since my question in a similar topic was deleted, I'll ask away and hope ppl won't come here telling me: this was already asked! :\
I have a ...
3
votes
4answers
645 views
Lagrangian to Hamiltonian in Quantum Field Theory
While deriving Hamiltonian from Lagrangian density, we use the formula
$$\mathcal{H} ~=~ \pi \dot{\phi} - \mathcal{L}.$$
But since we are considering space and time as parameters, why the formula
...
0
votes
0answers
46 views
Books on the general notions of measurements, observables, states, etc.? [closed]
I am reading the intro chapter in Huzihiro Araki's Mathematical Theory of Quantum Fields, which discusses the general notions of states, measurements, and observables (e.g. the topology on the sets of ...
2
votes
1answer
68 views
How do we deal with Gribov ambiguities when calculating in quantum gauge theories?
How do we deal with Gribov ambiguities when actually calculating in quantum gauge theories? Any literature references?
4
votes
0answers
38 views
Experimental tests of Cluster Decmposition
How tight are experimental and astrophysical tests on whether Cluster Decomposition is satisfied at various space-like separations?
Is there a review paper or a standard reference on the question?
I ...
7
votes
2answers
471 views
Majorana zero mode in quantum field theory
Recently, Majorana zero mode becomes very hot in condensed matter physics.
I remember there was a lot of study of fermion zero mode
in quantum field theory, where advanced math, such as index ...
5
votes
1answer
93 views
Is there a review article that discusses the various suggestions for approaches to the Dirac spinor field?
I've come across many approaches to the Dirac spinor field over the years. A few have held more than passing interest but most of them are rather forgettable, so that I'd like to know of any reviews ...
4
votes
1answer
236 views
How do we measure $i[\hat\phi(x),\hat\phi(y)]$ in QFT?
What operational procedure is required to measure $i[\hat\phi(x),\hat\phi(y)]$ in an interacting (or non-interacting) QFT? [assume smearing by test-functions, or give an answer in Fourier space, for ...
3
votes
1answer
210 views
Conceptual quantum field theory
Often papers and books give some bold(deep physical insight) statements in quantum field theory which are not backed by mathematics, and seldom by citing papers. Being a student I don't grasp the real ...
1
vote
0answers
72 views
The Paper by Fateev and Zamolodchikov
I would like to read the following paper by Fateev and Zamolodchikov.
Operator Algebra and Correlation Functions in the Two-Dimensional Wess-Zumino SU(2) x SU(2) Chiral Model.
In addition to the ...
4
votes
1answer
131 views
The difference between projection operators and field operators in QFT?
Is there a good reference for the distinction between projection operators in QFT, with an eigenvalue spectrum of $\{1,0\}$, representing yes/no measurements, the prototype of which is the Vacuum ...
4
votes
3answers
377 views
Unitarity of S-matrix in QFT
I am a beginner in QFT, and my question is probably very basic.
As far as I understand, usually in QFT, in particular in QED, one postulates existence of IN and OUT states. Unitarity of the S-matrix ...
11
votes
2answers
72 views
Discussions of the axioms of AQFT
The most recent discussion of what axioms one might drop from the Wightman axioms to allow the construction of realistic models that I'm aware of is Streater, Rep. Prog. Phys. 1975 38 771-846, ...
6
votes
2answers
269 views
What is known about quantum electrodynamics at finite times?
I'm aware that we can describe the time evolution of states/operators (choose your favourite picture) of non interacting quantum fields and that perturbation theory is very effective in computing S ...
1
vote
0answers
78 views
Can we use only the observables of Fermion fields?
There are legion ways to consider fermionic Dirac spinor fields, but is it possible to consider the asymptotic free field only in terms of observables, which in the case of the Dirac spinor field must ...
8
votes
0answers
123 views
Intuitive sketch of the correspondence of a string theory to its limiting quantum field theory
I'm looking for an intuitive sketch of how one shows the correspondence of string theory to a certain QFT. My best guess is that one calculates the scattering amplitudes in the string theory as a ...
4
votes
0answers
49 views
functional representations of free quantum fields
The free real quantum field, satisfying $[\hat\phi(x),\hat\phi(y)]=\mathrm{i}\!\Delta(x-y)$, $\hat\phi(x)^\dagger=\hat\phi(x)$, with the conventional vacuum state, which has a moment generating ...
6
votes
1answer
51 views
References for phase-transitions in supersymmetric field theory
Apart from other reasons, recently my interest in this area got piqued when I heard an awesome lecture by Seiberg on the idea of meta-stable-supersymmetry-breaking.
I am looking for references on ...
6
votes
2answers
341 views
Wilson/Polyakov loops in Weinberg's QFT books
I wanted to know if the discussion on Wilson loops and Polyakov loops (and their relationship to confinement and asymptotic freedom) is present in the three volumes of Weinberg's QFT books but in some ...
9
votes
4answers
351 views
The Schwinger model
The Schwinger model is the 2d QED with massless fermions. An important result about it (which I would like to understand) is that this is a gauge invariant theory which contains a free massive vector ...
4
votes
0answers
78 views
Can the Lamb shift be expressed in more-or-less closed form in terms of the renormalized 2-, 3-,…,n-point VEVs of QED?
I see here that there are three contributions to the Lamb shift, from vacuum polarization (-27 MHz), from electron mass renormalization(+1017 MHz), and from the anomalous magnetic moment (+68 MHz).
...
12
votes
2answers
181 views
Possible research implications of proof of John Cardy's a-theorem in QFT
According to this recent article in Nature magazine, John Cardy's a-theorem may have found a proof.
Question:
What would the possible implications be in relation to further research in QFT?
...
3
votes
1answer
187 views
WKB approximation to loop diagrams
I'm a bit confused with the terminology here.
This paper claimed to use WKB method to calculate the usual loop diagrams. Notice that the vertex is approximated by expanding around the classical ...
4
votes
0answers
235 views
What is the 2-point correlation function of the electron field in QED?
The Feynman propagator for the free electron field is the Fourier transform w.r.t. $y$ of the time-ordered 2-point VEV $\left<0\right|\mathcal{T}[\hat\psi(x)\hat\psi(x+y)]\left|0\right>$, taking ...
2
votes
1answer
448 views
Hyperfine structure vs Lamb shift in the hydrogen atom
The hyperfine structure of the energy levels of the hydrogen atom refers to the shifts in the evergy levels due to the magnetic moments of the nucleus and of the electron. This is an effect of ...
5
votes
2answers
642 views
Recommendations for time-line and road map in graduate school towards specializing in Maldacena's conjecture
This question was asked on Theoretical Physics Stackexchange and was grossly misread and closed.
I am again posting the question here hoping to get some valuable insights.
Also some people were ...
16
votes
3answers
96 views
Paper listing known Seiberg-dual pairs of N=1 gauge theories
Is there a nice list of known Seiberg-dual pairs somewhere? There are so many papers from the middle 1990s but I do not find comprehensive review. Could you suggest a reference?
Seiberg's original ...
4
votes
4answers
387 views
References for conceptual issues in Quantum Field Theory
I realize this question is very broad but may be I will still get a helpful answers. References and textbooks for the development of the technical and mathematical aspects of QFT abound. However, I ...
11
votes
2answers
149 views
Gauge invariance for electromagnetic potential observables in test function form
This is a reference request for a relationship in quantum field theory between the electromagnetic potential and the electromagnetic field when they are presented in test function form. $U(1)$ gauge ...
3
votes
1answer
229 views
String matrix models with c>1
Question 1: What is the status of string random matrix models (~ triangulated random surfaces) with c>1?
In my limited search, I have just come across a few papers by Frank Ferrari (in 2000-2002) on ...
12
votes
1answer
103 views
6d Massive Gravity
Massive gravity (with a Fierz-Pauli mass) in 4 dimensions is very well-studied, involving exotic phenomena like the vDVZ discontinuity and the Vainshtein effect that all have an elegant and physically ...
14
votes
3answers
1k views
Good reading on the Keldysh formalism
I'd like some suggestions for good reading materials on the Keldysh formalism in a condmat context. I'm familiar with the imaginary time, coherent state, path integral formalism, but lately I've been ...
12
votes
1answer
396 views
A reading list to build up to the spin statistics theorem
Wikipedia's article on the spin-statistics theorem sums it up thusly:
In quantum mechanics, the spin-statistics theorem relates the spin of a particle to the particle statistics it obeys. The spin ...
2
votes
1answer
141 views
Relativistic equation with arbitrary spin
can anyone give me some good references on how to obtain the relativistic equation of particles with arbitrary spin?
3
votes
1answer
347 views
Online lecture videos on QCD? [duplicate]
I would like to know if there are any online collections of lecture videos on QCD or non-Abelian QFT at a graduate level (at the level of volume 2 of Weinberg's QFT books?)
For example:
In String ...
6
votes
1answer
188 views
How to quantize the free electro-magnetic field in 2d?
I am wondering how one can quantize the free electro-magnetic field
in the two dimensional space-time. The standard method of fixing the
Coulomb gauge in 4d does not seem to generalize immediately to ...
5
votes
0answers
195 views
1-form formulation of quantized electromagnetism
In a perpetual round of reformulations, I've put quantized electromagnetism into a 1-form notation. I'm looking for references that do anything similar, both to avoid reinventing the wheel and perhaps ...
6
votes
1answer
353 views
Is microcausality *necessary* for no-signaling?
There are proofs in the literature that QFT including microcausality is sufficient for it not to be possible to send signals by making quantum mechanical measurements associated with regions of ...
2
votes
1answer
235 views
A particular notation about fermions
I am not sure that this notation is specific to supersymmetry theories but I ran into this while studying that.
I see people talking of component fields of a chiral superfield as $\phi$ and ...
5
votes
7answers
771 views
Evolution in the interpretation of the Dirac equation
As I understand, Dirac equation was first interpreted as a wave equation following the ideas of non relativistic quantum mechanics, but this lead to different problems.
The equation was then ...
4
votes
2answers
471 views
Quantum Field Theory cross sections integrals
Where can I find some examples of cross sections calculations in QFT done step-by-step? Those integrals are a little horror. For example - a simple scalar+scalar -> scalar+scalar at the tree level in ...
