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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Katz and Vafa's work on F-theory

I would like to know about the larger picture, current state and future prospects of the sequence of papers that were written by Sheldon Katz and Cumrun Vafa on F-theory. (Freddy Cachazo was also a ...
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497 views

Particle Lagrangians

As I learned in my string theory course, you can describe the quantum spin-0 particle by quantizing the arclength Lagrangian of a relativistic classical particle. My question is whether you can get a ...
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3answers
471 views

Horizon and Unruh radiation for a finite period of acceleration

It's a well known fact that an observer that accelerates at a constant rate from $-c$ at past infinity to $+c$ at future infinity sees a horizon in flat Minkowski spacetime. This is easy to see from a ...
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4answers
3k views

Chemical potential

This is something probably very basic but I was led back to this issue while listening to a recent seminar by Allan Adams on holographic superconductors. He seemed very worried to have a theory at ...
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3answers
1k views

No hair theorem for black holes and the baryon number

The no hair theorem says that a black hole can be characterized by a small number of parameters that are visible from distance - mass, angular momentum and electric charge. For me it is puzzling why ...
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3answers
867 views

Is contextuality required in quantum mechanics?

I still don't really understand what contextuality means in reference to quantum mechanics. If someone could give a clear definition that would be great. It sounds like it means you can't always ...
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1answer
452 views

Is there a rest frame for the Higgs boson?

If there is a non-zero expectation value for the Higgs boson even in "vacuum", since the Higgs boson has a mass unlike photons, then I would expect it to have a rest frame. So why doesn't a non-zero ...
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1answer
284 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 ...
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1answer
303 views

running of coupling constant as a function of distance?

There are many papers about the running of coupling strength as a function of momentum/energy scale, but are there any experimental papers about coupling strength as function of distance? Also, are ...
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2answers
222 views

Constructing the $\cal{N}=2$ supersymmetric non-Abelian Chern-Simon's theory

This is related to this earlier question I had asked. I am using the so called ``Majorana" representation of gamma matrices in $2+1$ dimensions in which everything is real. After doing the ...
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1answer
220 views

Density/distribution of Eigenvalues

In various articles (I am here talking about specially the ones related to string theory etc.) I have seen the discussion on density and distribution of eigenvalues. I want to know why do we use them ...
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1answer
1k views

What is Euler Density?

Can someone please explain to me what Euler Density is? I have encountered it in Weyl anomaly related issues in various articles. Most of them assumes that its familiar, but I couldn't find any ...
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1answer
876 views

dynamic casimir effect

A few years ago, when i studied the casimir effect interpretation as the filtering out of vacuum modes with appropiate boundary conditions, i had the following dilemma; supposedly the derivation of ...
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9answers
4k views

Rigor in quantum field theory

Quantum field theory is a broad subject and has the reputation of using methods which are mathematically desiring. For example working with and subtracting infinities or the use of path integrals, ...
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327 views

Construction of the $\cal{N}=3$ supersymmetric Yang-Mills Chern-Simons theory in $2+1$ dimensions

I am stuck with understanding the following construction. I am breaking it up into segments which I think can be separately answered. This is related to an earlier question of mine. Note that this ...
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3answers
653 views

Snell's law starting from qft? [duplicate]

Can one "interpret" Snell's law in terms of QED and the photon picture? How would one justifiy this interpretation with some degree of mathematical rigour? At the end I would like to have a direct ...
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1answer
288 views

Axion related questions

I have several question regarding axion. Could anyone give me some brief introduction to what is a axion string, axion field and how is this related to fermion zero mode and chiral zero mode?
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1answer
2k views

How does one prove Fierz identities?

Fierz identities are discussed in the wikipedia article: http://en.wikipedia.org/wiki/Fierz_identity but the article doesn't give any derivation. The article implies that they arise from the blade ...
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3answers
1k views

Why does dilation invariance often imply proper conformal invariance?

Why does a quantum field theory invariant under dilations almost always also have to be invariant under proper conformal transformations? To show your favorite dilatation invariant theory is also ...
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2answers
665 views

Higgs Boson Mass

The WIKI Higgs boson site has an interesting diagram illustrating likely Higgs mass intervals that experiments (LEP & Tevatron) or indirect measurements have determined with a 95% confidence ...
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0answers
382 views

An alternative, algebraic way to introduce interactions. Are there other ways out there?

An opening paragraph: The usual approach to introducing interactions in quantum field theory is to make the constraint on the amplitude of the field towards smaller values more forceful than ...
8
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2answers
488 views

Some Majorana fermion identities

I have been struggling with these Majorana fermion identities for quite sometime now. I would be grateful if someone can help me with them. Let $\lambda$,$\theta$ and $\psi$ be $4$-component ...
7
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2answers
226 views

Is there a meaning to the E,B analogues of other gauge fields?

From the gauge field $A_\mu$ and the QED lagrangian we can derive maxwell's equations in terms of electric and magnetic fields. Are there any situations where similar derivations using the other gauge ...
4
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1answer
721 views

Dimensional reduction from $3+1$ to $2+1$ for $\cal{N}=2$ vector superfield

Let the supersymmetry transformations for the chiral multiplet $(z_k,\psi_{kL},f_k)$ be, $\delta z_k = 2i \bar{\alpha} \psi_{kL}$ $\delta \psi_{kL} = D_\mu z_k \gamma ^\mu \alpha_R + f_k \alpha_L$ ...
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1answer
373 views

What is the spectral energy density of virtual photons around a unit charge at rest?

Given that my previous question, namely "What is the number density of virtual photons around a unit charge?" has no precise answer, here is a more precise wording: What is the virtual photon ...
7
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1answer
327 views

How do ideas of leading singularities and Grassmanian help in curing infrared divergences when calculating N=4 scattering amplitudes?

Broadly speaking how do ideas of leading singularities and Grassmanian help in curing infrared divergences when calculating N=4 scattering amplitudes? My understanding is that one gets infra red ...
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3answers
414 views

What is the density of virtual photons around a unit charge?

It seems that virtual photons also exist in vacuum. So the precise question is: What is the additional virtual photon density due to the electric field of a unit charge? Or: How many virtual photons ...
4
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1answer
147 views

Is the color gauge group spontaneously broken in QCD by the Savvidy vacuum?

One model for confinement in quantum chromodynamics is the Savvidy vacuum. This is a spontaneous symmetry breaking of color gauge symmetry by the gauge fields. The vacuum is divided into Savvidy ...
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527 views

Order Parameters for the Higgs Phase

Phase transitions are often detected by an order parameter - some quantity which is zero in the "disordered" phase, but becomes non-zero when order is established. For example, if the phase transition ...
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0answers
177 views

A particular supersymmetry transformation

While reading a paper I ran into this particular way of writing a $\cal{N}=3$ fields (in a theory with $N_f$ hypermultiplets) that I couldn't relate to anything I had seen before in the text-books ...
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3answers
585 views

Why are some solitons formed from bosonic fields fermionic?

Some topological solitons formed from bosonic fields have fermionic statistics. Why?
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1answer
571 views

There seems to be no definition of “stability” in axiomatic QFT. Is there? And, if not, is this a problem?

"stability" is invoked as the justification for the axiomatic requirement that the spectrum of the generators of the translation group must be confined to the forward light-cone. The spectrum ...
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1answer
580 views

The difference between free energy and perpetual motion [closed]

What is the difference between free energy (over unity) and perpetual motion? Please provide some examples, both real world and theoretical.
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2answers
564 views

Supersymmetry algebra

Let the $i=x,y,z$ components of the angular momentum have the commutation relations with the supersymmetry generators (also called supercharges?) $Q_a$ ($a = \pm \frac{1}{2}$) as, $[J_i , Q_a] = ...
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3answers
1k views

Spinning Tachyons

In all examples that I know, tachyons are described by scalar fields. I was wondering why you can't have a tachyon with spin 1. If this spinning tachyon were to condense to a vacuum, the vacuum ...
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4answers
500 views

What is the medium that allows magnetic fields *or any forcefield* to exist?

Magnetic fields are obvious distortions.. of.. something, but what exactly are they distortions of? Massive objects produce curvatures/gradients in space-time resulting in what we observe as ...
8
votes
1answer
662 views

Quantization of Gravitational Field: Quantization conditions

I'm begining to study Quantization of field with the second quantization formalism. I've studied phononic field, electromagnetic field in the vacuum and a generic relativistical scalar field. I ...
3
votes
1answer
402 views

If : V(Phi) : is nonlocal in space, does that mean interacting quantum field theory is nonlocal?

Free field theories are definitely local in . In the interaction picture, we can decompose the fields into creation operator modes and annihilation operator modes. The product of operators can be ...
8
votes
1answer
792 views

Dual conformal symmetry and spin networks in ABJM

In this question, I would love to hear some independent opinions on an issue I asked Juan Maldacena, Nathan Berkovits, Dan Jafferis, and others, but all the physicists may be missing something. The ...
4
votes
1answer
527 views

Supersymmetry breaking and Goldstino

I would be glad if someone can explain to me the argument as to why supersymmetry breaking is necessarily accompanied by appearance of a massless fermion, namely the goldstino. (and also why this is a ...
2
votes
3answers
795 views

What does the fine structure constant describe?

Feynman says in his book "QED" that the square root of the fine structure constant is the probability for a charged particle to emit a photon. But for which wavelength? Or is it an average over all ...
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1answer
511 views

Viscosity/Entropy ratio and unitary evolution in quantum gravity

Calculations of the shear viscosity of the quark-gluon plasma (QGP), observed in heavy ions collisions, are performed via the AdS/CFT correspondence [ref1]. One finds that the shear viscosity of the ...
2
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1answer
227 views

Is the exponential of the distribution $i\Delta^+(x)$, the 2-point function of a free quantized Klein-Gordon field theory, a distribution?

From answers to a previous question, a finite degree polynomial in the distribution $i\Delta^+(x)$, with Fourier transform $2\pi\delta(k^2-m^2)\theta(k_0)$, is a distribution, even though a product of ...
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3answers
948 views

Covariant Quantisation and the Time Operator in String Theory

Covariant quantisation in string theory is accomplished by giving the commutator relations $[X^\mu(\sigma,\tau),P^\nu(\sigma',\tau)] = i \eta^{\mu\nu} \delta(\sigma - \sigma')$. Although ...
4
votes
1answer
591 views

What is “localisation” of instantons?

I often encountered the term "localization" in the context of instantons, as for example in the work of Nekrasov on extensions of Seiberg-Witten theory to N=1 gauge theories. Could someone give a ...
8
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1answer
721 views

What is the status of applying numerical analysis to QM/QFT problems

This is something I don't ever seem to hear about, except regarding QCD ("lattice QCD"). What about QED? Is numerical integration always inferior to hand-calculating Feynman diagrams in perturbation ...
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2answers
407 views

Why do string theory and Hopf algebra renormalization seem to have no intersection?

Hopf algebra appears in recent papers that systematize renormalization of quantum field theory (QFT). For example see Connes' work and citing papers or a paper referenced here on PSE: R. E. ...
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3answers
1k views

What are the alternatives to the Higgs mechanism?

Can someone summarize, with references if possible, all of the alternatives to the simplest model (that requires only a single scalar Higgs field with the Mexican Hat potential) of spontaneous ...
6
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1answer
694 views

CFTs and formalizing quantum field theory

Moshe's recent questions on formalizing quantum field theory and lattices as a definition of field theory remind me of something I occasionally idly wonder about, and maybe this site can tell me the ...
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5answers
691 views

Is quantum field theory defined by its lattice regularization?

One statement I've heard many times is that QFT is "defined" by the lattice, or that the "only" definition of QFT is on the lattice (when such definition exists, e.g in pure Yang-Mills theory). I've ...