Tagged Questions
1
vote
1answer
26 views
Must string models that describe 4d effective field theories always have D-branes that extend in the 4 non-compact spacetime dimensions?
In string theory the D-branes give those directions that the strings are allowed to move along. The string excitations give the fields that we detect. Is it correct to think of a particle propagating ...
3
votes
1answer
111 views
What does it mean to renormalize an effective field theory?
This is in reference to slide 19 here http://cosmology.lbl.gov/talks/Pajer_13.pdf
"As always in Effective Field Theory, the theory becomes predictive when there are more observables than parameters"
...
6
votes
1answer
124 views
Open strings from closed strings
This issue comes up in Shiraz's lecture here on 29th October 2008.
I understand that he is saying that one can think of closed string theory as having two minima and that the ground state in the ...
3
votes
1answer
65 views
Emergence of $SU(2)\times SU(2)$ at the self-dual point in bosonic string theory
I want to understand the derivation of the equations 8.3.11 in Polchinski Vol 1.
I can understand that at the self-dual point the Kaluza-Klein momentum index $n$, the winding number $w$, and the ...
4
votes
0answers
43 views
Relations between diffeomorphism symmetry theories and invariant $SU(N), N \rightarrow \infty$ theories
Is it possible to have, an exhaustive panorama (as much as possible), about the relations between theories having a diffeomorphism symmetry, and theories having a $SU(N), N\rightarrow\infty$ ...
2
votes
0answers
33 views
Why isn't there a Heterotic string theory which tensors the fermionic state with the Type II state?
The Heterotic (HO and HE) string is found by tensoring the left movers of the bosonic string theory state and the right movers of the Type II string theory state:
...
4
votes
1answer
68 views
Proof of S-duality between Type IIB, IIB and Type HO, I string theories
About every source on string theory I've read which do mention S-duality state that:
$$\begin{array}{l}
\operatorname S:\operatorname{IIB} \leftrightarrow \operatorname{IIB}\\
\operatorname ...
5
votes
1answer
90 views
T-Duality between Type HE String theory and Type HO string theory
My question is regarding T-Duality between the 2 Type H string theories.
I know that the Type II String theories are T-dual to each other because T-Duality changes the sign of the Gamma Matrix so
...
2
votes
2answers
89 views
Question on the Hagedorn tower in Type I string theory
In a previous question (Mass spectrum of Type I string theory), I had asked about the mass spectrum of Type I string theory. I got a response saying that it is a Hagedorn tower. However, my source ...
4
votes
1answer
91 views
Flavour diagonal SUSY breaking
Because there is a single Yukawa matrix for the SM leptons, the lepton mass and flavour states can be aligned, by diagonalization, even if the Yukawa matrix had off-diagonal elements.
SUSY breaking, ...
2
votes
0answers
55 views
About deriving the multi-trace index in terms of the single-trace index
This question is in reference to this paper
Combining their equations 5.2, 5.3, 5.6 and 5.7 one seems to be looking at the integral/partition function,
$Z(x) = \prod_{n=1}^{n =\infty}\left [ \int ...
3
votes
1answer
72 views
Spectra of the Type II String theories
The spectrum of the Type II string theory (both IIA and IIB) is given by:
\begin{array}{*{20}{c}}
\hline
& {{\text{Sector}}}& & {{\text{Spectrum}}}& & {{\text{Massless Fields}}} ...
3
votes
0answers
31 views
``integrated vertex operators" in 1-loop open/closed bosonic string amplitude
This question is in reference to the first ~15 minutes of this String Theory lecture by Prof.Shiraz Minwalla,
http://theory.tifr.res.in/Videos/strings28_24sep08.mp4
Can one give a reference ...
2
votes
0answers
52 views
Standard Quantum Mechanics representation as a constrained 2 + 1 space-time (membrane) theory?
Could a particular Standard Quantum Mechanics representation be a constrained 2 + 1 space-time theory (membrane theory) ?
(i) This question is motivated by a possible (approximative) analogy with ...
3
votes
1answer
99 views
Supersymmetry and non-compact $R$-symmetry group?
The $R$-symmetry for $N$ supercharges is $U(N)$. Is it possible to generalize $R$-symmetry [let's take $U(4)$) to be something like $U(2,2)$ (maybe analogous to Wick rotation of $SO(3,1)$ to ...
7
votes
1answer
213 views
Introductory examples of AdS/CFT duality
I would like to know, what are the simplest/starting/basic examples that are typically used to introduce students to how AdS/CFT really works? (not the MAGOO paper, as I am not sure it has concrete ...
2
votes
1answer
94 views
Symmetries in Wilsonian RG (2)
This question is related to the paper http://arxiv.org/abs/1204.5221 and is a continuation of the previous question Symmetries in Wilsonian RG
In the liked paper why do the equalities in equation ...
9
votes
1answer
272 views
Symmetries in Wilsonian RG
I wanted to know if there is a theorem that in writing a Lagrangian if one missed out a term which preserves the (Lie?) symmetry of the other terms and is also marginal then that will necessarily be ...
7
votes
1answer
155 views
topological twisting by introducing bosonized operator
In this paper http://arxiv.org/abs/hep-th/9309140 on page 125, the authors claim that one can twist the $N=2$ theory by introducing a term in the action
$\frac{1}{2}\int R \phi$,
where $\phi$ is the ...
0
votes
4answers
343 views
Could all strings be one single string which weaves the fabric of the universe?
This question popped out of another discussion, about if the photon needs a receiver to exist. Can a photon get emitted without a receiver? A universe containing only one electron was hypothetically ...
3
votes
1answer
230 views
Deriving the reduced Green's functions in Polchinski's volume 1
In equation 6.2.7, Polchinski defines his reduced Green's functions $G'$ on the 2-manifold to satisfy the equation,
$$ \frac{-1}{2\pi \alpha '}\nabla ^2 G'(\sigma_1, \sigma_2) = ...
3
votes
0answers
219 views
Mathematics and Physics prerequisites for mirror symmetry [closed]
I am a physics undergrad interested in Mathematical Physics. I am more interested in the mathematical side of things, and interested to solve problems in mathematics using Physics. My current ...
1
vote
0answers
162 views
Starting string theory studies in grad school
How is it possible for a grad student to do research in any modern area of string theory like AdS/CFT or ABJM if they need to start grad school by having to learn QFT from scratch?
Is there a ...
4
votes
1answer
78 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
1answer
175 views
Defining a CFT using beta-functions
Won't it be correct to define a CFT as a QFT such that the beta-function of all the couplings vanish?
But couldn't it be possible that the beta-function of a dimensionful coupling vanishes but it ...
7
votes
0answers
357 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 ...
5
votes
0answers
117 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? ...
14
votes
0answers
227 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 ...
3
votes
0answers
264 views
What are the mathematical prerequisites to understand this paper? [closed]
What are the mathematical prerequisites to understand this paper?
Blumenhagen et al. Four-dimensional String Compactifications with D-Branes, Orientifolds and Fluxes. Phys. Rept. 445 no. 1-6, pp. ...
5
votes
0answers
146 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 ...
1
vote
1answer
97 views
What are all the approaches that have been tried for a theory of quantum gravity? [closed]
I am aware that that the most researched approach is that of string theory. I have also heard about quantum loop gravity. What other approaches are there to unify gravity and QFT? Also, please include ...
2
votes
1answer
143 views
Tachyon vertex operator (Polchinski's book)
I would like to know how does Polchinski in his book "derive" what is the "tachyon vertex operator" (..as say stated in equation 3.6.25, 6.2.11..) I can't locate a "derivation" of the fact that ...
13
votes
1answer
414 views
Multi-loop beta function of gauge theory (*without* Feynman diagrams)
I would like to point to the beautiful section 4.3 (page 42) of these lecture notes. I think this is the most educative exposition I have ever seen anywhere about Yang-Mill's beta function. What I ...
8
votes
2answers
454 views
What is the physical interpretation of the S-matrix in QFT?
A few closely related questions regarding the physical interpretation of the S-matrix in QFT: I am interested in both heuristic and mathematically precise answers.
Given a quantum field theory when ...
4
votes
1answer
130 views
Why Must Conserved Currents of Lorentz Symmetry Satisfy the Lorentz Algebra
I've seen it written many times that the commutation relation
$[M^{I-},M^{J-}]=0$
is required for Lorentz invariance in the light cone gauge quantisation of the bosonic string. This follows ...
1
vote
0answers
107 views
Extending General Relativity with Kahler Manifolds?
Standard general relativity is based on Riemannian manifolds.
However, the simplest extension of Riemannian manifolds seems to be Kahler manifolds, which have a complex (hermitian) structure, a ...
0
votes
0answers
88 views
Naive Uncertainty principle for string theory
Is it possible, in some sense, that a naive uncertainly principle for string theory could be expressed as :
$$ \Delta x_i \Delta p_j \Delta \sigma ~=~ \delta_{ij} \hbar \ell_s$$
where $\ell_s$ is ...
0
votes
1answer
170 views
Which theory is closest to Theory of Everything? [closed]
To present, Which theory is closest to Theory of Everything? In the future, it probably including into Theory of Everything.
Can you describe more detail or attach links that I can reading after?
2
votes
1answer
190 views
't Hooft limit of coupling fundamental fermions to Chern-Simons theory
This question is in reference to this paper: arXiv:1110.4386 [hep-th].
I would like to know what is the derivation or a reference to the proof of their crucial equation 2.3 (page 12).
In their ...
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
1answer
97 views
Is matrix picture of quantum mechnics further used in QFT and superstring theories?
Just curious: is matrix picture of quantum mechnaics further used in QFT and superstring theories? It seems like not....
4
votes
1answer
283 views
What is the essence of BCFW recursion techniques?
I have recently briefly read about new methods as the Britto-Cachazo-Feng-Witten (BCFW) on-shell recursion method.
Can anybody please tell me about the essence of it?
What does it mean for the ...
7
votes
1answer
209 views
Does string theory provide a physical regulator for Standard Model divergencies?
In other question, Ron Maimon says that he thinks string theory is the physical regulator. I did not know that string theory regularize divergencies.
So, Q1: How does string theory regularize the ...
6
votes
1answer
254 views
Mathematical concept of supersymmetry
I wish to study supersymmetry in field theory(sometime in december). However, I am quite not sure what is needed for its study. In supersymmetry, I just want to get the mathematical idea, such as its ...
1
vote
0answers
79 views
Some questions about flavour and R-symmetry in $2+1$ ${\cal N}=3$ theory
I have heard this fact that for ${\cal N}=3$ theories in $2+1$ with $N_f$ ${\cal N}=3$ matter fields the flavour symmetry group is $USp(N_f)$, $U(N_f)$ or $SO(2N_f)$ depending on whether the gauge ...
4
votes
1answer
267 views
Wilson loops and gauge invariant operators (Part 2)
These questions are sort of a continuation of this previous question.
I would like to know of the proof/reference to the fact that in a pure gauge theory Wilson loops are all the possible gauge ...
1
vote
1answer
98 views
Hypothetical very massive particles
I'm looking for a table or compilation of hypothetical very massive ($m\gtrsim 1$ TeV) particles and their expected masses (or bounds on them or relation with other scales). All I know is (please, ...
2
votes
1answer
157 views
Pedagogic reference for calculation of 2-loop anomalous dimension (supersymmetric)
I want to know of pedagogic references which teach how to compute anomalous dimensions (..wave-function renormalization..) at lets say 2-loops. I guess there might be specialized techniques for ...
3
votes
0answers
118 views
Dual Resonance Model: Fermions
I am going through Ramond's 1971 paper Dual Theory for Free Fermions Phys Rev D3 10, 2415 where he first attempts to introduce fermions into the conventional dual resonance model.
I get the 'gist' of ...
1
vote
2answers
92 views
What is unification, unified interactions, or dualities between interactions?
Scientists succeeded in unifying EM with the weak force, then with the strong force to achieve the standard model. They then studied supersymmetry and GUTs that showed improved gauge coupling ...
