Quantum Field Theory (QFT) is the theoretical framework describing the quantisation of classical fields which allows a Lorentz-invariant formulation of quantum mechanics. QFT is used both in high energy physics as well as condensed matter physics and closely related to statistical field theory. Use ...
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1k views
Superfields and the Inconsistency of regularization by dimensional reduction
Question:
How can you show the inconsistency of regularization by dimensional reduction in the $\mathcal{N}=1$ superfield approach (without reducing to components)?
Background and some references:
...
17
votes
0answers
329 views
Sigma Models on Riemann Surfaces
I'm interested in knowing whether sigma models with an $n$-sheeted Riemann surface as the target space have been considered in the literature. To be explicit, these would have the action ...
15
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0answers
106 views
Systematic approach to deriving equations of collective field theory to any order
The collective field theory (see nLab for a list of main historical references) which came up as a generalization of the Bohm-Pines method in treating plasma oscillations are often used in the study ...
12
votes
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204 views
Anomalous target space diffeomorphisms for one-loop world-line integrals
The Schwinger effect can be calculated in the world-line formalism by coupling the particle to the target space potential $A$.
My question relates to how this calculation might extend to computing ...
10
votes
0answers
346 views
An unfamiliar way of writing supersymmetry transformations
This question is in relation to this recent paper.
I would like to know how the so called supersymmetry transformations at the start of page 27 or at the end of page35 (equation 8.4) or at the end ...
9
votes
0answers
89 views
infrared free QED and Higgsless standard model phenomenology
This is one of those "what if" fantasy world type questions. I like hard sci-fi so please no "well, you changed one thing about the world so now anything goes." :)
What if the Higgs had no vev?
That ...
8
votes
0answers
45 views
What is the reason why anyons escape spin-statistic theorem?
I'm wondering about the exact reason why anyons escape the spin-statistic theorem (SST), see e.g. http://en.wikipedia.org/wiki/Spin–statistics_theorem.
I've read somewhere (the wikipedia page is ...
8
votes
0answers
140 views
gauge invariant but not gauge covariant
I'm not sure if someone's already asked this before, but I was wondering, in field theory,
when we say that a certain field is gauge invariant but not gauge covariant, what does this mean? In ...
8
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0answers
121 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 ...
8
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0answers
438 views
Could this model have soliton solutions?
$\mathcal{L}=i\bar{\Psi}\gamma^\mu\partial_\mu\Psi-m\bar{\Psi}\Psi+\frac{1}{2}g(\bar{\Psi}\Psi)^2$
Field equation $(i\gamma^\mu\partial_\mu-m+g\bar{\Psi}\Psi)\Psi=0$
Could this model have soliton ...
7
votes
0answers
353 views
About defining “baryons” and “mesons”
I want to understand the proof of the claims (of the construction as well as of its uniqueness) of gauge singlet states given around equation 2.13 (page 10) of this paper.
Also does the listing of ...
7
votes
0answers
165 views
What is the precise definition or list of prerequisites for an anyonic system?
I have been reading some reviews and looked into books on anyons and topological quantum computation and I found it a little difficult to make out a short list of parameters and a clear and short list ...
7
votes
0answers
190 views
How to determine if an emergent gauge theory is deconfined or not?
2+1D lattice gauge theory can emerge in a spin system through fractionalization. Usually if the gauge structure is broken down to $\mathbb{Z}_N$, it is believed that the fractionalized spinons are ...
7
votes
0answers
306 views
Wick rotation and spinors
I am quite familiar with use of Wick rotations in QFT, but one thing annoys me: let's say we perform it for treating more conveniently (ie. making converge) a functional integral containing spinors; ...
6
votes
0answers
80 views
Dimensional regularization and IR divergences and scale invariance
I want to know if dimensional regularization has any issues if the theory has IR divergences or is scale invariant.
Does dimensional regularization see "all" kinds of divergences?
I mean - what ...
6
votes
0answers
150 views
Regulator-scheme-independence in QFT
Are there general conditions (preservation of symmetries for example) under which after regularization and renormalization in a given renormalizable QFT, results obtained for physical quantities are ...
6
votes
0answers
141 views
Does local physics depend on global topology?
Motivating Example
In standard treatments of AdS/CFT (MAGOO for example), one defines $\mathrm{AdS}_{p+2}$ as a particular embedded submanifold of $\mathbb R^{2,p+1}$ which gives it topology ...
6
votes
0answers
182 views
Renormalization group evolution equations and ill-posed problems
There is a class of observables in QFT (event shapes, parton density
functions, light-cone distribution amplitudes) whose the renormalization-group
(RG) evolution takes the form of an ...
6
votes
0answers
157 views
Reflection positivity in general
In the Euclidean QFT obtained by "Wick-rotating" a unitary QFT, the correlation functions satisfy a property called reflection positivity, see e.g. this Wikipedia article for the case of a scalar ...
6
votes
0answers
72 views
Instantons and Borel Resummation
As explained in Weinberg's The Quantum Theory of Fields, Volume 2, Chapter 20.7 Renormalons, instantons are a known source of poles in the Borel transform of the perturbative series. These poles are ...
5
votes
0answers
78 views
Setting of renormalization scale in field theory calculations
In dimensional regularization an arbitrary mass parameter $\mu$ must be introduced in going to $4-\epsilon$ dimensions. I am trying to understand to what extent this parameter can be eliminated from ...
5
votes
0answers
120 views
How does Haldane conjecture follow from the topological $\Theta$ term
The one dimensional SU(2) Heisenberg quantum spin chain is known to be described by the 1+1d O(3) nonlinear $\sigma$ model with a $\Theta$ term, following the action
...
5
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0answers
53 views
Does the Standard Model plasma develop a spontaneous magnetisation at finite temperature?
Reference: arXiv:1204.3604v1 [hep-ph] Long-range magnetic fields in the ground state of the Standard Model plasma.
Alexey Boyarsky, Oleg Ruchayskiy, Mikhail Shaposhnikov.
The authors of this paper ...
5
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0answers
119 views
Using $\frac{1}{A+i\epsilon} = PV\frac{1}{A}-i\pi\delta(A)$ in Feynman Integrals
Are the following operations O.K.? This is related to the Feynman parameter trick.
$$F:= \int_0^1 \mathrm{d}x\int_0^{1-x}\mathrm{d}y \frac{1}{f(x,y)+\mathrm{i}\epsilon}.$$ Now using
...
5
votes
0answers
113 views
Are QFT solitons expected to represent standard model particles? Or strings?
Is work on solitons in QFT's focused on finding solutions that could represent the fundamental particles of the Standard Model, or is the work focused on finding particles Beyond The Standard Model? ...
5
votes
0answers
82 views
Auxiliary fields in supersymmetry
I know that auxiliary fields can be used to close the supersymmetry algebra in case the bosonic and fermionic on-shell degrees of freedom do not match. Could somebody please elaborate on this concept ...
5
votes
0answers
137 views
An use of the Schwinger-Dyson equation
I was confused as to how the equation 10 on page 7 or equation 21 on page 8 of this paper http://arxiv.org/abs/1211.1866 was derived. Can someone explain from where does this come and what do the ...
5
votes
0answers
203 views
Gaussian Integrals : Functional determinant expressed as a trace
Be $A_{ij}$ a symmetric matrix. Then I can easily write
$$
\int \exp\left(-\frac{1}{2}\sum_{i,j}x_i A_{ij} x_j+\sum_{i} B_i x_i\right)\; d^nx=
\sqrt{(2\pi)^n}\exp\left\{-\frac{1}{2}\mathrm{Tr}\log ...
5
votes
0answers
68 views
R charge of the chiral multiplet in $2+1$ dimensions
These are two examples that I am puzzled by,
One can see in this paper on page 16 that for ${\cal N} =2$ theory on $2+1$ the R-charge of the $\phi$ and the $\psi$ is determined to be $\frac{1}{2}$ ...
5
votes
0answers
75 views
How do you simulate a quantum gauge theory in a gauge with negative norms on a quantum computer?
How do you simulate a quantum gauge theory in a gauge with negative norms on a quantum computer? There are some gauges with negative norms. It's true that if restricted to gauge invariant states, the ...
5
votes
0answers
143 views
Breaking of Lorentz invariance
Thinking about the concept of symmetry breaking led me to the following question:
Let's say that I have a theory described by a Lorentz invariant Lagrangian, and the true vacuum of the theory is not ...
5
votes
0answers
194 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 ...
4
votes
0answers
45 views
What goes wrong when one tries to quantize a scalar field with Fermi statistics?
At the end of section 9 on page 49 of Dirac's 1966 "Lectures on Quantum Field Theory" he says that if we quantize a real scalar field according to Fermi statistics, the quantum Hamiltonian is no ...
4
votes
0answers
55 views
No mixing in light cone perturbation theory
In hep-ph/0609090, Triumvirate of Running Couplings in Small-x Evolution, Kovchegov et. al. calculated the running coupling correction to the Jalilian-Marian, Iancu, McLerran, Weigert, Leonidov and ...
4
votes
0answers
71 views
Noether currents for the BRST tranformation of Yang-Mills fields
The Lagrangian of the Yang-Mills fields is given by
$$
\mathcal{L}=-\frac{1}{4}(F^a_{\mu\nu})^2+\bar{\psi}(i\gamma^{\mu}
D_{\mu}-m)\psi-\frac{1}{2\xi}(\partial\cdot A^a)^2+
...
4
votes
0answers
82 views
Computing functional determinant for Dirac fermions
In the path integral formulation for quantum field theory, one often encounters functional determinants of operators, for example for a free scalar field
$\log \det (\partial^2+m^2)$. For this ...
4
votes
0answers
36 views
axial and vector resonances in composite higgs models
Is there a reason to believe that the axial resonances be heavier than the vector resonances in the composite higgs models?
For instance, in http://arxiv.org/abs/0808.2071, to have zero tree level ...
4
votes
0answers
76 views
Is the search for a Simple-group-based Electro-Weak theory over?
Just wondering:
We know that, in its current form of the $SU(2)_L\times U(1)$, the electroweak theroy rides a wave of huge success. However, is it not possible that the correct simple group ...
4
votes
0answers
106 views
Non-covariance of the higher rank propagator (from Weinberg's QFT textbook)
In chapter 6.2 of Weinberg's QFT Vol1 , he gave the general form of Wick contractions of all possible fields(scalar, spinor, vector, etc.), he showed
...
4
votes
0answers
99 views
Does the Standard Model have a Landau pole?
I have seen the statement that the Standard Model has a Landau pole, or at least it its believed that it does at $\sim 10^{34}$ GeV. Has this actually been proven (at least in perturbation theory, as ...
4
votes
0answers
59 views
Dimensional transmutation in Gross-Neveu vs others
Firstly I don't know how generic is dimensional transmutation and if it has any general model independent definition.
Is dimensional transmutation in Gross-Neveau somehow fundamentally different ...
4
votes
0answers
103 views
Reference on Chern-Simons theory
I have recently been trying to refresh my memory on the Quantum Field Theory I learned 25 years ago while getting my Ph. D. At the time I did not study Chern-Simons modifications to QFT Lagrangians. ...
4
votes
0answers
121 views
Trace of stress tensor vanishes ==> Weyl invariant
You often see in textbooks the statement that ${T^\mu}_\mu = 0$ implies Weyl invariance or conformal invariance. The proof goes like
$\delta S \sim \int \sqrt{g} T^{\mu\nu} \delta g_{\mu\nu} \sim ...
4
votes
0answers
51 views
Are irrelevant terms in the Kahler potential always irrelevant, even at strong coupling?
I've been reading about the duality cascade in Strassler's TASI '03 lectures (hep-th/0505153). He reminds us of the non-renormalization theorem theorem for the superpotential so that the beta ...
4
votes
0answers
50 views
$f_{NL}$ non-Gaussianity in cosmology
In the context of cosmology, what is meant by "..arbitrary quadratic non-Gaussianity i.e non-Gaussianity that is described to leading order by a 3-point function.."? (.."quadratic non-Gaussianity" ...
4
votes
0answers
74 views
The asymptotic behavior of the propagator of a field
In Steven Weinberg's book "The Quantum Theory of Fields" vol. I, Section 12.1, page 500, it writes:
"We will write the asymptotic behavior of the propagator $\Delta_f(k)$ of a field of type $f$ in ...
4
votes
0answers
57 views
gravitational convergence of light
light has a non-zero energy-stress tensor, so a flux of radiation will slightly affect curvature of spacetime
Question: assume a flux of radiation in the $z$ direction, in flat Minkowski space it ...
4
votes
0answers
111 views
Relation among anomaly, unitarity bound and renormalizability
There is something I'm not sure about that has come up in a comment to other question:
Why do we not have spin greater than 2?
It's a good question--- the violation of renormalizability is linked
...
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 ...
4
votes
0answers
105 views
What is the rate of B violation expected in the standard model during high energy collisions?
In a recent question Can colliders detect B violation? I asked about detecting B violation in collisions. Here I am interested in the theory aspect. (I asked both questions originally in the same ...
