A class of theories that attempt to explain all existing particles (including force carriers) as vibrational modes of extended objects, such as the 1-dimensional fundamental string. PLEASE DO NOT USE THIS TAG for non-relativistic material strings, such as, e.g., a guitar string.

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117
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11answers
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What experiment would disprove string theory?

I know that there's big controversy between two groups of physicists: those who support string theory (most of them, I think) and those who oppose it. One of the arguments of the second group is ...
26
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4answers
5k views

What if the LHC doesn't see SUSY?

A question in four parts. What are the main problems which supersymmetry purports to solve? What would constitute lack of evidence for SUSY at the proposed LHC energy scales (e.g. certain predicted ...
25
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11answers
6k views

Discreteness and Determinism in Superstrings?

So Gerard 't Hooft has a brand new paper (thanks to Mitchell Porter for making me aware of it) so this is somewhat of a expansion to the question I posed on this site a month or so ago regarding 't ...
22
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1answer
1k views

How does classical GR concept of space-time emerge from string theory?

First, I'll state some background that lead me to the question. I was thinking about quantization of space-time on and off for a long time but I never really looked into it any deeper (mainly because ...
21
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2answers
2k views

Is there a T-dual of Witten's twistor topological string theory?

In late 2003, Edward Witten released a paper that revived the interest in Roger Penrose's twistors among particle physicists. The scattering amplitudes of gluons in $N=4$ gauge theory in four ...
21
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1answer
376 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 ...
20
votes
10answers
4k views

Applications of Algebraic Topology to physics

I have always wondered about applications of Algebraic Topology to Physics, seeing as am I studying algebraic topology and physics is cool and pretty. My initial thoughts would be that since most ...
20
votes
3answers
16k views

What is the current status of string theory (2013)?

I've seen a bunch of articles talking about how new findings from the LHC seem to disprove (super)string theory and/or supersymmetry, or at least force physicists to reformulate them and change ...
19
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2answers
2k views

How does string theory reduce to the standard model?

It is said that string theory is a unification of particle physics and gravitation. Is there a reasonably simple explanation for how the standard model arises as a limit of string theory? How does ...
19
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2answers
5k views

What is tension in string theory?

One often hears the words "string tension" in string theory. But what does it really mean? In ordinary physics "tension" in an ordinary classical string arises from the fact that there are elasticity ...
18
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7answers
3k views

What are the strings in string theory made of?

This is a follow-up to an intriguing question last year about tension in string theory. What are the strings in string theory composed of? I am serious. Strings made of matter are complex objects ...
18
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4answers
1k views

What is your simplest explanation of the string theory?

How would you explain string theory to non physicists such as myself? I'm specially interested on how plausible is it and what is needed to successfully prove it?
18
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0answers
610 views

A dictionary of string - standard physics correspondences

Motivated by the (for me very useful) remark ''Standard model generations in string theory are the Euler number of the Calabi Yau, and it is actually reasonably doable to get 4,6,8, or 3 ...
17
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2answers
802 views

BPS states : Mathematical definition

First of all, let me congratulate the theoretical physics community for this site. I am a mathematics student with very little background in phyiscs. The question I want to ask is: What is the proper ...
17
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1answer
1k views

Why is there a deep mysterious relation between string theory and number theory, elliptic curves, $E_8$ and the Monster group?

Why is there a deep mysterious relation between string theory and number theory (Langlands program), elliptic curves, modular functions, the exceptional group $E_8$, and the Monster group as in ...
16
votes
1answer
264 views

Is string theory local?

By locality I mean something like the Atiyah-Segal axioms for Riemannian cobordisms (see e.g. http://ncatlab.org/nlab/show/FQFT). I.e. to any (spacelike) hypersurface in the target we associate a ...
16
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2answers
475 views

S-Matrix in $\mathcal{N}=4$ Super-Yang Mills

This is a general question, but what is meant when people refer to the S-Matrix of $\mathcal{N}=4$ Super Yang Mills? The way I understood it is the S-Matrix is only well defined for theories with a ...
16
votes
1answer
709 views

Zero modes ~ zero eigenvalue modes ~ zero energy modes?

There have been several Phys.SE questions on the topic of zero modes. Such as, e.g., zero-modes (What are zero modes?, Can massive fermions have zero modes?), majorana-zero-modes (Majorana zero ...
16
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2answers
749 views

Does the exact string theory $S$-matrix describe all physics there is?

Suppose someone manages to evaluate the string theory $S$-matrix to all orders for any and all vertex operator insertions including non-perturbative contributions from world-sheet instantons and ...
16
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3answers
1k views

Is decoherence even possible in anti de Sitter space?

Is decoherence even possible in anti de Sitter space? The spatial conformal boundary acts as a repulsive wall, thus turning anti de Sitter space into an eternally closed quantum system. Superpositions ...
15
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5answers
889 views

String Theory and Standard Model in CERN

I don't know how to say it, but in the TV dominatrices and the popular science books we see the string theory as "the best theory to explain everything", and as "the only game in town"... etc. And ...
15
votes
4answers
657 views

Isn't gravity non-local and non-causal?

The way I think of this is that, I can ask physical questions about a space-time which are impossible to answer unless one knows the full space-time, and hence I am inclined to believe that gravity is ...
15
votes
5answers
1k views

What's so special about AdS?

This question is coming from someone who has very little experience with M-Theory but is intrigued by the AdS/CFT correspondence and is beginning to study it. Why is the gauge/gravity duality ...
15
votes
2answers
375 views

Generalized Complex Geometry and Theoretical Physics

I have been wondering about some of the different uses of Generalized Complex Geometry (GCG) in Physics. Without going into mathematical detail (see Gualtieri's thesis for reference), a Generalized ...
15
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1answer
1k views

Good introductory text for matrix string theory

Where can I find a good introductory text for matrix string theory? Most textbooks don't cover it, or only cover it very superficially. What is the basic idea behind matrix string theory? How can ...
14
votes
3answers
1k views

What is a brief formulation of string theory?

I know that similar questions have been asked before, but none of them is exactly what I would like to know. I want to have a general idea of what string theory is, without having to read several ...
14
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1answer
1k views

Is String Theory formulated in flat or curved spacetime?

String Theory is formulated in 10 or 11 (or 26?) dimensions where it is assumed that all of the space dimensions except for 3 (large) space dimensions and 1 time dimension are a compact manifold with ...
14
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1answer
2k views

What evidence exists for string theory viability?

I know that string theory is still under heavy development, and as such it still can't make predictions (or not that many predictions anyways). On the other hand, it is clear from the number of years ...
14
votes
1answer
594 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 ...
14
votes
2answers
326 views

Newtonian gravity from the holographic principle?

Can one understand Newton's law of gravitation using the holographic principle (or does such reasoning just amount to dimensional analysis)? Following an argument similar to one given by Erik ...
13
votes
3answers
371 views

about the Atiyah-Segal axioms on topological quantum field theory

Trying to go through the page on Topological quantum field theory - The original Atiyah-Segal axioms - "Let $\Lambda$ be a commutative ring with 1, Atiyah originally proposed the axioms of a ...
13
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7answers
2k views

What reasons are there to suspect string theory may be an incorrect theory?

It's a truism that in science it is at least as important to state the reasons why a theory or idea might be wrong, as to state the reasons why it is might be correct. For example, early ...
13
votes
2answers
405 views

Renormalization in string theory

I'm taking a course in string theory and have encountered renormalization for the first time (and I suspect it isn't the last). Specifically, while quantizing the bosonic and spinning strings, an ...
13
votes
2answers
323 views

Which CFTs have AdS/CFT duals?

The AdS/CFT correspondence states that string theory in an asymptotically anti-De Sitter spacetime can be exactly described as a CFT on the boundary of this spacetime. Is the converse true? Does any ...
13
votes
1answer
185 views

realization of: CFT generating fuction = AdS partition function

An important aspect of the AdS/CFT correspondence is the recipe to compute correlation functions of a boundary operator $\mathcal{O} $ in terms of the supergravity fields in the interior of the ...
13
votes
3answers
907 views

Has the black hole information loss paradox been settled?

This question was triggered by a comment of Peter Shor's (he is a skeptic, it seems.) I thought that the holographic principle and AdS/CFT dealt with that, and was enough for Hawking to give John ...
13
votes
3answers
760 views

Space-time in String Theory

I would like to understand how Physicists think of space-time in the context of String Theory. I understand that there are $3$ large space dimensions, a time dimension, and $6$ or $7$ (or $22$) extra ...
13
votes
2answers
105 views

Uniqueness of supersymmetric heterotic string theory

Usually we say there are two types of heterotic strings, namely $E_8\times E_8$ and $Spin(32)/\mathbb{Z}_2$. (Let's forget about non-supersymmetric heterotic strings for now.) The standard argument ...
13
votes
1answer
68 views

Local Fermionic Symmetry

That is perhaps a bit of an advertisement, but a couple of collaborators and myself just sent out a paper, and one of the results there is a little bit surprising. We found (in section 6E) a fermionic ...
13
votes
4answers
2k views

Introduction to AdS/CFT

AdS/CFT seems like a really hot topic and I'd like to start reading about. I am looking for the best introduction at my level, i.e. I have a background in QFT, CFT and general relativity at the level ...
13
votes
1answer
516 views

How come random matrices can predict energy spectra of heavy atoms?

Some of the applications of random matrices is to find the spectra of heavy atoms in nuclear physics which are usually difficult to find otherwise. How can starting from randomness of some kind, ...
13
votes
1answer
37 views

SuperHiggs Mechanism on different Backgrounds & Compactifications

I've been studying Bagger & Giannakis paper on the SuperHiggs Mechanism found here. The paper shows how SUSY is broken by a $B_{\mu\nu}$ gauge field background restricted to $T^3$ in $M^7\times ...
12
votes
3answers
1k views

What are the details around the origin of the string theory?

It is well-known even among the lay public (thanks to popular books) that string theory first arose in the field of strong interactions where certain scattering amplitudes had properties that could be ...
12
votes
3answers
1k views

Mathematics of AdS/CFT

To date, what is the most mathematically precise formulation of the AdS/CFT correspondence, and what are the most robust tests of the conjecture?
12
votes
2answers
678 views

Does string theory have a notion of vacuum?

Does string theory have a notion of vacuum? If yes, what is known about it?
12
votes
2answers
662 views

Why one-dimensional strings, but not higher-dimensional shells/membranes?

One way that I've seen to sort-of motivate string theory is to 'generalize' the relativistic point particle action, resulting in the Nambu-Goto action. However, once you see how to make this ...
12
votes
1answer
66 views

Physical interpretation of superstrings

The scalar fields $X^\mu$ in bosonic string theory have a clear physical interpretation - they describe the embedding of the string in spacetime. Adding fermionic fields on the worldsheet is a ...
12
votes
3answers
2k views

Beginners questions concerning Conformal Field Theory

I started reading about Conformal Field Theory a few weeks ago. I'm from a more mathematical background. I do know Quantum Mechanics/Classical Mechanics, but I'm not really an expert when it comes ...
12
votes
1answer
988 views

What is the relationship between string theory and quantum field theory?

Please forgive a string theory novice asking a basic question. Over at this question Luboš Motl gave an excellent answer, but he made a side comment that I've heard before and really would want to ...
12
votes
1answer
216 views

Self-dual Maxwell equations, the second homology group, and topological invariants of a four manifold

In Witten's paper Quantum Field Theory and the Jones Polynomial, he mentioned that: Geometers have long known that (via de Rham theory) the self-dual and anti-self-dual Maxwell equations are ...