A class of theories that attempt to explain all existing particles (including force carriers) as vibrational modes of one-dimensional objects.
5
votes
0answers
51 views
paper about black branes and implications to 4d black holes
This paper makes a case for piezoelectric response (electric dipole moment under mechanical oscillations) of black branes. This paper does not make an implication of their results for 4D black holes ...
5
votes
1answer
276 views
Reference for mathematics of string theory [closed]
I have a great interest in the area of string theory, but since I am more focused on mathematics, I was wondering if there is any book out there that covers mathematical aspects of string theory. I ...
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
149 views
Why Brown York stress tensor == dual field theory's energy momentum tensor?
From the AdS/CFT dictionary, how to argue that the Brown York stress tensor for a gravity
system near the boundary is exactly the same as the energy momentum tensor of the dual field theory?
In the ...
5
votes
0answers
41 views
Why Are Even and Odd Regge Trajectories Degenerate?
The Gribov-Froissart projection treats even angular momentum differently from odd angular momentum.
But in QCD, I believe that the odd trajectories interpolate the even trajectories--- the two ...
5
votes
0answers
140 views
Chiral fermions from torsion flux in M-theory?
Witten's 1981 paper "Search for a realistic Kaluza-Klein theory" is frequently cited for its observation that, in a compactification of d=11 supergravity on a manifold with SU(3) x SU(2) x U(1) ...
4
votes
5answers
1k views
What differs string theory from philosophy or religion? [duplicate]
Possible Duplicate:
What experiment would disprove string theory?
A hypothesis without hard evidence sounds very much like philosophy or religion to me. All of them tries to establish a ...
4
votes
5answers
584 views
Regarding string theory: how to refute the argument “if it cannot be tested experimentally then it is not science”? [duplicate]
Possible Duplicate:
What differs string theory from philosophy or religion?
I find a lot of people disbelieve in string theory, saying that since it cannot be tested experimentally then it ...
4
votes
3answers
729 views
Give a description of M-theory your grandmother can understand
Inspired by this question, let me ask a similar question. Is it possible to do the same (give a description of M-theory your grandmother could understand)for M theory? While I know even experts don't ...
4
votes
2answers
314 views
Why do we have so many dualities in string theory?
Why do we have so many dualities in string theory? Is there a reason for that?
4
votes
2answers
249 views
What happens when two strings collide?
I have a question, that perhaps someone with a much better understanding of physics can help me answer.
Please correct me if I'm wrong. From what I understand, a string in string theory is basically ...
4
votes
4answers
856 views
Is spacetime discrete or continuous?
Is the spacetime continuous or discrete?
Or better, is the 4-dimensional spacetime of general-relativity discrete or continuous? What if we consider additional dimensions like string theory ...
4
votes
1answer
941 views
Gabriele Veneziano, strong nuclear force and beta-function
Background to the question:
From The History of String Theory:
Gabriele Veneziano, a research fellow at CERN (a European particle accelerator lab) in 1968, observed a strange coincidence - many ...
4
votes
1answer
358 views
Why is E6 favored over E8 for GUT building?
What is the simplest explanation on why is E6 gauge group more favored as a group for Grand unified theory builders, while E8 is not? What about other exceptional groups? Which of them originate from ...
4
votes
2answers
308 views
Sparticles: Relationship to supersymmetry and dark matter?
I was attempting to read this paper after watching a show with Brian Greene. As I understand it, sparticles are a prediction of supersymetry, so I was wondering:
Wouldn't the discovery of ...
4
votes
3answers
316 views
Why (in relatively non-technical terms) are Calabi-Yau manifolds favored for compactified dimensions in string theory?
I was hoping for an answer in general terms avoiding things like holonomy, Chern classes, Kahler manifolds, fibre bundles and terms of similar ilk. Simply, what are the compelling reasons for ...
4
votes
1answer
163 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 ...
4
votes
1answer
187 views
Conformal transformation equation
I am currently reading Kiritsis's string theory book, and something bugs in the CFT (fourth) chapter. He derives the equation that should satisfy an infinitesimal conformal transformation $x^{\mu} ...
4
votes
2answers
228 views
How to check Einstein-like equations on their correspondence with the real world?
Physicists studying the grounds of physics and some mathematicians often come to a theories which are like a general-relativity, but do not coincide with it. Often these theories contradict the real ...
4
votes
2answers
194 views
The string Poisson bracket
Where does the factor $\frac{1}{T}$ ($T$ is the string tension) in this Poisson bracket come from?
$$ \{X^{\mu}(\tau,\sigma),\dot{X}^{\nu}(\tau,\sigma')\} ~=~ ...
4
votes
1answer
128 views
Why Must Conserved Currents of Lorentz Symmetry Satisfy the Lorentz Algebra
I've seen it written many times that the commutation relation
$[M^{I-},M^{J-}]=0$
is required for Lorentz invariance in the light cone gauge quantisation of the bosonic string. This follows ...
4
votes
1answer
52 views
Proof of S-duality between Type IIB, IIB and Type HO, I string theories
About every source on string theory I've read which do mention S-duality state that:
$$\begin{array}{l}
\operatorname S:\operatorname{IIB} \leftrightarrow \operatorname{IIB}\\
\operatorname ...
4
votes
2answers
242 views
Fundamental equation(s) of string theory?
I often hear about string theory and its complicated mathematical structure as a physical theory, but I can't say that I've ever actually seen any of the related math. In general, I'm curious as to ...
4
votes
1answer
159 views
Trick for deriving the stress tensor in any theory
In D. Tong's notes on string theory (http://www.damtp.cam.ac.uk/user/tong/string/four.pdf) section 4.1.1 he explains a trick for deriving the stress-energy tensor which arises from translations in the ...
4
votes
1answer
105 views
How to handle D-brane particles in the S-matrix using string worldsheets?
In string theory, it's possible to collide a number of strings only in the asymptotic past, and get a final asymptotic state which contains a D0-brane, an anti D0-brane, and a number of strings. If ...
4
votes
2answers
301 views
Does String theory say that spacetime is not fundamental but should be considered an emergent phenomenon?
Does String theory say that spacetime is not fundamental but should be considered an emergent phenomenon?
If so, can quantum mechanics describe the universe at high energies where there is no ...
4
votes
1answer
706 views
What do “tachionic” neutrinos mean for QG?
Reading about the spectacular Opera claim, I`m (again ;-P) wondering if a confirmation of superliminous neutrinos could help settle some still open quantum gravity issues ...?
In this post, Lumo ...
4
votes
1answer
497 views
On black holes, Hawking radiation and gravitational atoms
Over the past hour or so I've been following one of my standard physics-based, wanders-through-the-internet. Specifically, I began by reviewing some details of dark energy theory but soon found myself ...
4
votes
1answer
292 views
What is the current status of the swampland?
What is the current status of the swampland? Have people expanded the list of swampland criteria?
If let's say I wish to figure out if the Standard Model belongs to the swampland, are there any ...
4
votes
3answers
162 views
Open/Closed Branes
Hello this is my first question.
For an open string you can pick different boundary conditions for the endpoints along different directions of space time. For example, you can choose Dirichlet ...
4
votes
1answer
70 views
How can we have massive states of strings and CFT on the string worldsheet at the same time?
Ok, so we can have conformal invariance on a string world sheet. However, it is well known that to preserve conformal symmetry we require states to be massless. So how is it that string theories ...
4
votes
1answer
249 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 ...
4
votes
1answer
271 views
Boundary conditions in AdS/CFT
This question is in reference to this very famous paper of Witten.
In general through the whole paper why is the author able to just focus on the scalar field propagating in the bulk and not need ...
4
votes
1answer
108 views
Open String Coupling
I'm reading Zwiebach's First Course in String Theory. At present I'm learning about string coupling. Zwiebach says it's possible to prove that $g_o^2=g_c$ where $g_o,\ g_c$ are open and closed string ...
4
votes
2answers
345 views
The multiverse of eternal inflation
I don't have a clear picture of what is "by definition" the multiverse appearing in the models of eternal inflation. A long time ago I heard that it is a quantum state, but in the cosmology books I ...
4
votes
1answer
75 views
What is the connection between extra dimensions in Kaluza-Klein type theories and those in string theories?
This follows to some extent from a question I asked previously about the flaws of Kaluza-Klein theories.
It appears to me that Kaluza-Klein theories attach additional dimensions to spacetime that are ...
4
votes
2answers
163 views
question about SL(2,Z) duality of string theory/N=4 SYM
N=4 SYM has an SL(2,Z) duality group. This can be thought of in two ways: 1. This theory can be obtained by compactifying the 6D N=(2,0) theory on a torus, and this group comes from the group of ...
4
votes
2answers
321 views
What is currently incomplete in M-theory?
As it is, what is currently and seemingly incomplete in M-theory?
One example I can give is explaining dark matter proportions
and.. how do we perceive the world as 4-dimensional.
Thanks everyone.
4
votes
1answer
278 views
Angular momentum in string theory
Since strings are extended objects, is all angular momentum in string theory essentially "orbital" angular momentum? Or is there still a kind of intrinsic angular momentum assigned to a string?
...
4
votes
1answer
156 views
What is the stress-energy distribution of a string in target space?
If $| \psi \rangle$ is a string mode, how do you compute $\langle \psi | \hat{T}^{\mu\nu}(\vec{x}) | \psi \rangle$ where $\vec{x}$ is a point in target space? This information will tell us the energy ...
4
votes
1answer
181 views
Are there string backgrounds which can't be described by first quantized string theory?
In the strong coupling limit of type IIA and heterotic E8 string theory, we get 11 dimensional M-theory in which we have no strings. Instead, we have M2 branes.
Are there any other backgrounds in ...
4
votes
1answer
464 views
Where's the mass?
When you look a the Polyakov or Nambu-Goto action, you see a T for tension, but no mass. When you look the action of a relativistic particle, you see the m. See here.
So here's the question. Where is ...
4
votes
1answer
97 views
Is there an upper bound on the gauge group rank in F-theory compactifications on CY 4-folds?
It is known that in F-theory compactifications on CY 4-folds one can get gauge groups with very large ranks. The largest single factor* gauge group for compact CY 4-folds I found in the literature is ...
4
votes
2answers
321 views
T-duality approaches
The textbook approach to explaining T-dualities is to show that a type of T-duality transformation "inverts the radius of the circle, that is, it maps $R\rightarrow\tilde{R} = \alpha'/R$ and it ...
4
votes
1answer
84 views
Virasoro TT OPE in Polchinski's book
I'm trying to understand eq. 2.2.11 in Polchinski's first book.
He's computing
$$:\partial X^\mu(z)\partial X_\mu(z): :\partial' X^\nu(z')\partial' X_\nu(z'):$$
Now, I understand why this ...
4
votes
1answer
88 views
Where and how is the entropy of a black hole stored?
Where and how is the entropy of a black hole stored?
Is it around the horizon? Most of the entanglement entropy across the event horizon lies within Planck distances of it and are short lived.
Is ...
4
votes
1answer
207 views
About 2+1 dimensional superconformal algebra
I would like to get some help in interpreting the main equation of the superconformal algebra (in $2+1$ dimenions) as stated in equation 3.27 on page 18 of this paper. I am familiar with supersymmetry ...
4
votes
2answers
457 views
Critics of Mannheim's Conformal Gravity Theory?
I'm looking for more articles/reactions/critiques/support for Philip Mannheim's recent conformal gravity theory.
See here: http://arxiv.org/abs/1101.2186v1
Any ideas on where to start?
4
votes
1answer
187 views
How is black hole complementarity derived from path integrals or string theory?
How is the black hole complementarity version of the holographic principle derived from path integrals and/or string theory? That has never been obvious to me. Can someone show me how to do it step by ...
4
votes
2answers
170 views
Is it outside science to figure out the precise string compactification of our universe?
String theory has at least $10^{500}$ 6D compactifications. Denef and Douglas proved the computational complexity of finding a compactification which fits the parameters of the low energy effective ...
