A class of theories that attempt to explain all existing particles (including force carriers) as vibrational modes of one-dimensional objects.
6
votes
0answers
63 views
String landscape in different dimensions
For D = 11 large (uncompactified) spacetime dimensions, the only "string theory" vacuum is M-theory
For D = 10, there are 5 vacua. Or maybe it's more correct to say 4, since type I is S-dual to ...
5
votes
4answers
519 views
Does string theory tells us anything concrete about black hole decay?
EDIT: I edited the question to reflect Moshe's objections. Please, look at it again.
It's apparently a black hole time around here so I decided to ask a question of my own.
After a few generic ...
5
votes
1answer
45 views
Are there stable string theory vacua with non-minimal cosmological constant?
Naive reasoning suggests that a string theory vacuum with cosmological constant Lambda1 is always unstable as long as there is a string theory vacuum with cosmological constant Lambda2 < Lambda1 ...
5
votes
2answers
148 views
Advanced topics in string theory
I'm looking for texts about topics in string theory that are "advanced" in the sense that they go beyond perturbative string theory. Specifically I'm interested in
String field theory (including ...
5
votes
3answers
456 views
What is the physical significance of the dilaton in string theory?
Strings always have a dilaton in their spectrum. Its a scalar field (so presumably no spin), and so far a hypothetical particle. What is its physical significance?
5
votes
2answers
341 views
More questions on string theory and the standard model
This is a followup question to
How does string theory reduce to the standard model?
Ron Maimon's answer there clarified to some extent what can be expected from string theory, but left details open ...
5
votes
2answers
430 views
Is there a maximum number of types of elementary particles?
Doing a Google search i found a paper called The maximum number of elementary particles in a super symmetric extension of the standard model.
It claims in the abstract that the upper bound is 84 (i ...
5
votes
1answer
88 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
...
5
votes
1answer
63 views
Choice and identification of vacuums in AdS/CFT
I know how we define a vacuum in flat space QFT and also in a curved space QFT. But, can somebody tell me how do the choice of vacuum state in (say) the CFT side of AdS/CFT changes the choice of ...
5
votes
2answers
464 views
What is background independence and how important is it?
What is background independence and how important is it?
In order to be a theory of everything, will the final string-theory/m-theory have to be background independent?
Does the current lack of ...
5
votes
3answers
257 views
Information loss in a black hole
How does the Holographic Principle help to establish the fact that all the information is not lost in a black hole?
5
votes
2answers
638 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 ...
5
votes
2answers
384 views
Question about Calabi-Yau manifolds and quantum fluctuations at the Planck scale
Super string theory establishes that at each point of our 4 dimensional spacetime, there is attached a 6-dimensional Calabi-Yau (CY) manifold which encodes the geometry of the additional compactified ...
5
votes
2answers
180 views
If we are willing to accept tachyonic string modes, are there valid projections other than the GSO projections?
One reason superstring theory has often been touted as being an improvement over bosonic string theory is that we can impose GSO projections to remove the tachyonic mode. If we insist upon the no ...
5
votes
2answers
507 views
Other possible theories (other than string theory) which are generalizations of the standard model with incorporation of gravity
The only finite mathematical framework that incorporates both the standard model of particle physics and gravity under one umbrella that I am aware of is string theory. I would like to know whether ...
5
votes
1answer
127 views
Vector and Spinor Representation in Ramond-Neveu-Schwarz Superstring Theory
I am learning Ramnond-Neveu-Schwarz Superstring theory (RNS theory). I often find the following notation, especially in the closed string spectrum etc.:
$$\mathbf{8}_s,\mathbf{8}_v $$
And it is ...
5
votes
2answers
106 views
How to understand worldsheet fermion as a section?
I am reading Witten's paper on topological string, and I found some mathematical notation is hard to understand for me.
Consider the nonlinear sigma model in 2 dimensions governed by maps
$\Phi : ...
5
votes
1answer
78 views
About Vanishing of BRST commutator in path integral
In Witten's paper Topological Quantum Field Theory, about formula (3.2), the property $<\{Q,\mathcal{O}\}>=0$ depends on the assertion that $Z_{\varepsilon}(\mathcal{O})= \int \mathcal{D}X ...
5
votes
2answers
126 views
Quantization of strings on a curved backgrond
usually when people want to quantize the string on flat background, they will try to find the the OPE of embeddings (by solving a green function in a 2D space) and use them to find the energy-momentum ...
5
votes
1answer
25 views
Scaling solutions in context of Denef - Moore
My question is based on the paper Split states, entropy enigma, holes, halos.
What are the scaling solutions discussed on page 49 of the paper ?
It is stated that the equations ${\sum_{j, i\neq ...
5
votes
1answer
96 views
Renormalization of the R-charge?
In general I would like to know as to known or what is/are the standard references about R-charge renormalization in supersymmetric theories. When does it do so and what is expected or known to be ...
5
votes
2answers
209 views
Lorentz transformation in light cone coordinates in string theory
What is the explicit form of the Lorentz transformation changing the light cone coordinates in the light cone gauge in string theory? The extended nature of the strings complicate matters, especially ...
5
votes
1answer
189 views
Why are the even and odd Regge trajectories degenerate?
This is an old classic which I don't think ever got a clear answer. The Gribov-Froissart projection that gives the relativistic version of Regge trajectories treats even angular momentum differently ...
5
votes
1answer
209 views
Why aren't string compactifications by generic conformal field theories considered more often?
Most string theory compactifications analyzed so far have as backgrounds a conformal field theory corresponding to a nonlinear sigma model with a Calabi-Yau target space, or some relatively classical ...
5
votes
1answer
199 views
Is this explanation of “Why nine space dimensions?” correct?
In Gordon Kane's Supersymmetry and Beyond (p. 118), he states:
String theory has to be formulated in nine space dimensions or it is not a consistent mathematical theory. There doesn't seem to be a ...
5
votes
2answers
155 views
How can string theory work without supersymmetry?
This question is inspired from reading Mitchell Porter's nice answer here to a question asking why supersymmetry should be expected naturally. Among other things, he explains that since weak scale ...
5
votes
1answer
249 views
Bosonic Tachyon Condensation?
The tachyonic string mode in perturbative bosonic string theory indicates that the "vacuum", flat Minkowski $\mathbb{R}^{25,1}$, is not really a vacuum. What is conjectured about tachyon condensation ...
5
votes
2answers
325 views
Is string length in string theory quantized?
Is there a minimal string length (maybe the Plank length?), and is it quantized?
Do strings have a 0-dimensional (ie point) cross-section?
5
votes
1answer
254 views
CY moduli fields
When one does string compactification on a Calabi-Yau 3-fold. The parameters in Kähler moduli and complex moduli gives the scalar fields in 4-dimensions. It is claimed that the Kähler potentials of ...
5
votes
1answer
109 views
How Exactly Does Linear Regge Trajectories Imply Stability?
(for a more muddled version, see physics.stackexchange: http://physics.stackexchange.com/questions/14020/whats-with-mandelstams-argument-that-only-linear-regge-trajectories-are-stable)
There is a ...
5
votes
2answers
61 views
Significance of massive states in string theory
A free superstring has an infinite tower of states with increasing mass. The massless states correspond to the fields of the corresponding SUGRA. In "Quantum Fields and Strings: A Course for ...
5
votes
1answer
39 views
Interplay between the cosmological constant and “microscopic” properties of string vacua
As far as I understand, string phenomenology is usually concerned with compactifications of string theory, M-theory or F-theory in which the uncompactified dimensions form a 4-dimensional Minkowski ...
5
votes
1answer
184 views
Can a $CFT_2$ which can't be factorized into chiral and antichiral parts and/or have a central charge not a multiple of 24 have AdS duals?
In the article Three dimensional gravity reconsidered by Ed Witten, he remarked that the CFT dual to three dimensional quantum gravity has to admit a holomorphic factorization and have a central ...
5
votes
2answers
619 views
How much can AdS/CMT tell us?
I will begin my research on AdS/CMT, however I find AdS/CMT is only a phenomelogical method, so I want to know can AdS/CMT give some results the condensed matter physicists can not give, or even ...
5
votes
1answer
63 views
AdS/RCFT examples?
RCFT's (rational conformal field theories) in two dimension are very well-studied, but it seems that there is no any gravity dual of such theories has been found. Is there example of the holographic ...
5
votes
1answer
308 views
Taking the continuum limit of $U(N)$ gauge theories
I would like to draw your attention to appendix $C$ on page 38 of this paper.
The equation $C.2$ there seems to be evaluating the sum $\sum_R \chi _R (U^m)$ in equation 3.16 of this paper. I ...
5
votes
1answer
3k views
How would the discovery of Higgs Boson affect superstring theories?
As we probably all know, a new particle similar to Higgs Boson has been discovered.
If this turns out to be true, standard model will get a boost (as the discovered mass almost equals to the ...
5
votes
1answer
113 views
Some questions about the BCFW reduction
I am trying to give a fast sketch of what the BCFW reduction does and embed within it some questions at the steps which I don't seem to understand clearly. The first bullet point is sort of a very ...
5
votes
1answer
307 views
Doubts about tubular Feynman diagrams in string theory
The tubular Feynman diagrams in string theory, unlike the usual Feynman diagrams in QFT, is assumed to represent scattering amplitudes, rather than derived from algebraic expressions of perturbative ...
5
votes
1answer
344 views
Is Weyl invariance absolutely necessary for string worldsheets?
The Polyakov action for a string worldsheet has Weyl invariance. In the conformal gauge augmented with Weyl gauge-fixing, we can always impose a flat worldsheet metric in Minkowski coordinates. The ...
5
votes
2answers
187 views
Superselection sectors and $p+1$ form potentials in String Theory
we often come across the phrase superselection sector. I have couple of questions from that.
First of all, I learned from some references about it (as a overview) and how is it related to ...
5
votes
4answers
422 views
Is String Theory a Field Theory?
Is String Theory a Field or Quantum Mechanical Theory of the String rather than a Particle?
I should know this having studied this for a term, but we jumped into the deep end, without really ...
5
votes
1answer
293 views
Mathematically rather than physically speaking, is there something “special” about 10 (or 11) dimensions?
As I understand it, string theory (incorporating bosons and fermions) "works" in $9+1=10$ spacetime dimensions. In the context of dual resonance theory, I've read descriptions of why that is ...
5
votes
1answer
264 views
At what scale does UV/IR mixing happen in string theory?
Imagine, if you will, a string background with an extremely tiny value for the string coupling. The Planck scale is many orders of magnitude smaller in size than the string scale. Is the UV/IR mixing ...
5
votes
2answers
351 views
Space-time filling D-branes in type-I superstring theory
It's known that gauge group for type-I superstring theory should be SO(32) for chiral anomalies to cancel. This is realized by presense of 16 space-time filling D9-branes, together with 16 space-time ...
5
votes
1answer
133 views
Correlators in String Theory (Green Schwarz Witten)
I'm reading about correlators in string theory for amplitude computations. More specifically formulae 7.1.53 and 7.1.54 in Green Schwarz Witten. I don't see how they can be derived.
E.g. 7.1.53 is
...
5
votes
1answer
642 views
Some questions on Conformal Field Theory, Current algebras and the Sugawara construction
Since I don't know how to add another question to an already existing topic,
I'm opening a new thread. However I'm referring to:
Beginners questions concerning Conformal Field Theory
As noted, a ...
5
votes
0answers
249 views
Can the laws of quantum mechanics be derived from a more fundamental theory? [closed]
String theory takes quantum mechanics for granted and tries to make it compatible with gravity but if it turns out to be a theory of everything then shouldn't it in principle explain why our world is ...
5
votes
0answers
106 views
Has hep-th/0312070 forgotten to fix $s_{0} = 1/2$ for the fermionic states in the second table on page 52?
Link to the original paper: The Gauge/String Correspondence Towards Realistic Gauge Theories (arXiv paper)
On page 52 we see that, for a theory of Dp-branes placed at an orbifold (orbifold = ...
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? ...
