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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Can computers survive bubble nucleations?

According to string landscape theory, our vacua with a cosmological constant of $10^{-123}$ is a metastable vacua which can decay to a supersymmetric vacua with either a zero or negative cosmological ...
11
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3answers
1k views

Does gravity require strings?

OK, before I ask my question, let me frame it with a few (uncontroversial?) statements: The low-field-limit plane-wave solution to Einstein's equations is helicity-2. In the early days of string ...
3
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2answers
783 views

Is string theory a quantum theory of gravity?

I have read that string theory predicts (or requires ?) the existence of gravitons. So, would that make it a quantum theory of gravity ? If so, I have also read that quantum gravity would allow us to ...
2
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1answer
501 views

Do Neveu-Schwarz conditions make sense?

When putting fermions on the string, we have to choose boundary conditions for our spinor fields - Ramond or Neveu-Schwarz. NS conditions on the closed string have antiperiodic conditions such as $\...
3
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1answer
332 views

Does kaon decay etc prove “CP violation” or just “CP or CPT violation”

Shlomo Sternberg (math professor at Harvard) wrote a book called "Group theory and physics". On p156 (link) there's a strange offhand comment: "Experiments done in 1964 by Fitch and Cronin seem to ...
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1answer
466 views

Do we need a quantum deformation of the diffeomorphism group in string theory?

Let me justify my question before I go on. In string theory, gravitons are strings extended over space. Longitudinal gravitons are pure gauge modes of the diffeomorphism group. However, in string ...
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8answers
5k views

Why are extra dimensions necessary?

Some theories have more than 4 dimensions of spacetime. But we only observe 4 spacetime dimensions in the real world, cf. e.g. this Phys.SE post. Why are the theories (e.g. string theory) that ...
3
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1answer
306 views

Could the 6 extra dimensions in superstring theory be a product of two manifolds?

Could the 6 extra dimensions in superstring theory be a product of two manifolds?
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2answers
202 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 ...
3
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1answer
351 views

Can we have non continuous models of reality? Why don't we have them?

This question is about Godel's theorem, continuity of reality and the Luvenheim-Skolem theorem. I know that all leading physical theories assume reality is continuous. These are my questions: 1) Is ...
8
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0answers
191 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) ...
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1answer
554 views

The measure problem in the anthropic principle

The anthropic principle is based upon Bayesian reasoning applied to the ensemble of universes, or parts thereof, conditioned upon the existence of conscious observers. That still leaves us with the ...
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1answer
349 views

D-branes wrapping divisors and/or cycles

What is the difference between a divisor and a homology cycle? What is the difference between a D-brane wrapped around a divisor and a D-brane wrapped around a cycle?
3
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1answer
102 views

Why is the sum over string worldsheets of varying genuses unitary?

It can be shown the sum over all Feynman diagrams in quantum field theory leads to a unitary S-matrix. Where can I find a proof that the sum over string worldsheets with varying genuses also leads to ...
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1answer
738 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 "...
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2answers
241 views

Compactification of Dimensions

As the only way String theory can respect the principles of quantum mechanics and Special theory of relativity, by formulating it in hypothetical nine dimensional space. You could use string ...
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0answers
335 views

Is there any simple proof of the no-ghost theorem?

Is there any simple proof of the no-ghost theorem in string theory?
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1answer
378 views

Drawbacks of Standard model

I am a graduate level student, interested in String theory. I was reading a paper on "String Theory and Einstein's Dream" published in Current Science, vol. 89, No. 12, p 2045, Dec. 25, 2005. and I ...
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1answer
511 views

Why doesn't string theory have a mass gap?

Gravitons are string modes which can have arbitrarily small energies. Just make the wavelength arbitrarily large. String theory has no mass gap, but why? A classical string can only have positive ...
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1answer
382 views

Charges and Topology

I must apologize, I was a little bit excited when I began understanding some of this, I can not say I can compete with professionals, and words are still difficult concepts. In (1) S.H. et al. it is ...
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1answer
148 views

Black Holes and String states

We seem to know that black hole energy, and apparently event horizon geometry and topology, are functions of Mass, Charge and Angular Momentum. Area is a function of geometry and topology as well, ...
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2answers
917 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
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2answers
511 views

In what order should the subjects be studied in order to get to String Theory [duplicate]

I know: Quantum Mechanics (Griffiths Level, currently doing Sakurai Level) Mechanics (Newtonian+ Lagrangian/Hamiltonian but at level lower than Goldstein/Landau) Classical Electrodynamics (...
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1answer
210 views

If strings are infinitely extended, are they nonlocal?

To completely localize a string within any bounded region of space, no matter how large, requires an infinite energy. Does this mean strings modes are inherently nonlocal?
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1answer
640 views

Does the renormalization group apply to string theory?

Can we implement a scale dependent cutoff Λ to string theory? Can we perform a renormalization group analysis of string theory consistently?
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1answer
583 views

What is the smoking gun signature of string theory?

What is the smoking gun signature of string theory? Suppose we have a complete and consistent model of quantum gravity with a zero or negative cosmological constant, but all we are given is its ...
2
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1answer
640 views

What is the mathematical nature of space time quantization in string theory/super string theory?

I don't know much about string theory, apart from it being a theory of everything which brings QM, QED and nuclear forces and gravity under one single roof. I am curious to know from a mathematical ...
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1answer
266 views

The 4D Physics of a Superstring Background

Suppose I have a compactification of string theory to four Minkowski dimensions of the form $M^{1,3}\times X$, where the internal CFT on $X$ is a $c=9$, $(2,2)$ SCFT. For example, let the SCFT on $X$ ...
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1answer
224 views

The chiral ring of N=2 WZW models

Does anyone knows if the chiral ring of the Kazama-Suzuki models have been found? If yes, please send me the reference. Thanks
6
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1answer
679 views

String theory and trace anomaly in semiclassical gravity?

what does string theory have to say about the trace anomaly in the expectation value of the stress energy tensor of massless quantum fields on a curved background and its interpretation as the ...
3
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3answers
787 views

Question on Conformal Field Theory

Since every question has to be asked in a seperate topic, I'm asking a question refering to the following topic: Beginners questions concerning Conformal Field Theory In particular I'm referring to ...
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2answers
256 views

Does the lack of modular nuclearity in string theory mean anything?

Nuclearity is a postulate in algebraic quantum field theory (AQFT). Basically, it says thermal states at any temperature always have a thermodynamic limit with extensive quantities. This is violated ...
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1answer
404 views

Chern-Simons Theory in 3D

For the CS theory on a three manifold $M$ with a gauge group $G$, it is said that the gauge field $A$ is a connection on the trivial bundle over $M$. Why the bundle should be trivial? I know that ...
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3answers
625 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 ...
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1answer
1k 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 ...
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1answer
243 views

Is the quantum state or information of a particle is all that differentiates it from another particle?

So I have learned in my QM classes that you can't tell one electron from another electron. They are indistinguishable. I also learned that the wavefunction of a particle includes the spacial part and ...
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0answers
221 views

If D-branes are the same as p-branes, and p-branes open out to “another universe”, why is the other universe invisible in D-branes?

Related to my other misguided question, D-branes are equivalent to p-branes. D-branes are described by a sheet in topologically trivial spacetime. p-branes are extremal black branes. They have an ...
4
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1answer
294 views

Is the “moduli problem” completely solved in string theory?

We know, string theory, from its inception, has a technical problem of the instability of the extra dimensions. I have heard of the partial solution of the problem quite a few years ago. My question ...
3
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1answer
362 views

Do open strings with both ends attached to the same D-brane really exist?

Perturbatively, open strings with both ends attached to the same D-brane definitely exist. But D-branes have nonzero p-form charges. These charges give rise to a nonzero flux with nonzero stress-...
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3answers
3k 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 ...
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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 ...
9
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1answer
360 views

Can the connectivity of space change in string theory?

A flop transition changes the second homotopy group of a Calabi-Yau compactifation, but not the fundamental group or the number of connected components. Can the number of connected spatial components ...
5
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1answer
454 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 ...
7
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1answer
244 views

Why aren't D-branes and strings independent degrees of freedom?

A condensate of open strings with both ends attached to the same D-brane can be equivalent to a displacement of the D-brane with no open string condensate. A solution to the D-brane Born-Infeld ...
7
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1answer
389 views

Graviton Emission from D-Branes

I'm working through Polchinski's book on string theory, and I ran into something that I don't think I understand. I'm hoping that someone who knows this stuff can help me out. Before calculating the ...
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1answer
460 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? ...
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8answers
3k views

What future technologies does particle physics and string theory promise? [closed]

What practical application can we expect from particle physics a century or two from now? What use can we make of quark-gluon plasmas or strange quarks? How can we harness W- and Z-bosons or the Higgs ...
4
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1answer
469 views

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 co-...
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2answers
429 views

Classifying all possible BPS configurations in string theory

Is there a classification of all possible BPS configurations in string theory? It has to include Calabi-Yau orbifolds, intersecting D-branes, coincident D-branes, etc. . To simplify matters, take the ...
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3answers
409 views

References on the non-compositeness of the known elementary particles

What paper(s) or theory(s) describe or prove that the elementary particles that we have determined today cannot be made up of smaller more fundamental particles?