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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23
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7answers
4k 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 ...
3
votes
2answers
199 views

Identification of extended quantum objects?

In some physics theories like string theory we have notion of spatially extended quantum objects - strings, membranes etc. Assuming that such objects exist, how would they appear in experiments ? More ...
4
votes
1answer
160 views

Mass of a superstring between two branes?

A open bosonic string between two parallel branes seems to obey formulae such as $M^2 = \big((n + {\theta_i - \theta_j \over 2 \pi}) {R' \over \alpha'}\big)^2 + {N-1 \over \alpha'} $ So that the ...
5
votes
2answers
908 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 ...
2
votes
1answer
223 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 ...
3
votes
0answers
56 views

Do unoriented strings possess asymptotic states?

In QFT based particle theory, SU(N)-colored particles are not really present as asymptotic states, then raising some problems to build a S-matrix or other more axiomatic approaches to the theory. ...
14
votes
1answer
646 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 ...
3
votes
1answer
868 views

Why does the universe exhibit three large-scale spatial dimensions? [duplicate]

Possible Duplicate: Is 3+1 spacetime as privileged as is claimed? Regardless of your favorite theory of how many dimensions the universe has in total, the universe seems to have a deep ...
0
votes
0answers
42 views

why is the modelisation of elementary particle as a two dimensional object in contradiction with General Relativity?

This is asserted by Trinh Xuan Thuan in his book "Chaos & Harmony" chapter String theory.
3
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1answer
303 views

Quantization of Nambu–Goto action in multiples of Planck's constant?

Isn't it possible? Quantization of Nambu–Goto action $$\mathcal{S} ~=~ -\frac{1}{2\pi\alpha'} \int \mathrm{d}^2 \Sigma \sqrt{{\dot{X}} ^2 - {X'}^2}~=~nh\qquad n \in\mathbb{Z}.$$
3
votes
1answer
691 views

Recent Higgs boson observation and credibility of superstring theories

Data are coming in, and it seems that recent Higgs boson observation is eliminating many SUSY models. If so, what is happening to superstring theories, like M-theory?
2
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0answers
91 views

M-Theory: Are the branes still colliding and matter is being produced into our universe?

In M-Theory membranes are rippling in the 11th dimension and when they collided the bing bang happened and the ripples produced matter, is it still happening and matter is still being produced? ...
13
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2answers
1k 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 ...
2
votes
1answer
100 views

Constraints on open strings absent at the perturbative level

Studying Disappearance of moduli for condensate of open strings and Negative open string norms after BRST cohomology? gave me a huge huge shock! Suppose we have N completely wrapped Dp-branes over a ...
4
votes
1answer
835 views

How do Einstein's field equations come out of string theory?

The classical theory of spacetime geometry that we call gravity is described at its core by the Einstein field equations, which relate the curvature of spacetime to the distribution of matter and ...
15
votes
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 ...
4
votes
1answer
173 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 ...
2
votes
1answer
132 views

How exactly are the different motions of only one kind of fundamental string assumed to give rise to the spectrum of elementary particles we observe?

In string theory, it is assumed that all particles can be described as quanta corresponding to the excitations of only one kind of fundamental string. How can in principle the different motion ...
16
votes
2answers
765 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 ...
0
votes
0answers
190 views

Colliding bubbles in hyperspace

Assuming the following A universe is the surface from a bubble in hyperspace. Inside a bubble there is nothing, only the surface represents a universe. The size of the bubble is time. Dark matter is ...
1
vote
1answer
891 views

Branes Collision -> Big Bang

Imagine universe occurred when two parallel branes collided, Momentum of Branes converted to big bang kinetic energy after Collision. Thus, high-energy quanta are high-Vibrating strings. what ...
3
votes
1answer
220 views

What interaction does a Fayet-Iliopoulos coupling parameterize the strength of?

Couplings give the strength of interactions. They appear in a Lagrangian as a coefficient to the two (or more) interacting fields. Unfortunately, I'm struggling to find a source that describes what it ...
4
votes
1answer
115 views

Negative open string norms after BRST cohomology?

The question Disappearance of moduli for condensate of open strings made me think. Suppose we have a Dp-brane completely wrapped over a $T^d$ compactification with $p\leqslant d$. Look at an open ...
4
votes
0answers
320 views

Isn't a single Quantum one single string? [duplicate]

In physics, a quantum (plural: quanta) is the minimum amount of any physical entity involved in an interaction. In Quantum Mechanics There is no difference between one Quantum to another one. ...
2
votes
0answers
117 views

Can decompactification explain the inflation of the early universe?

I've just reread chapter 11 of this book where it is explained among other things, that our four dimensional universe could be unstable concerning a decompactification transition, since potential ...
3
votes
5answers
176 views

Why is the world sheet of an open string a cylinder?

I went to a lecture a few weeks ago and was told the following: The world sheet of a closed string is a normal, standing cylinder. The world sheet of an open string is a cylinder on its side. This ...
6
votes
1answer
132 views

Disappearance of moduli for condensate of open strings

Consider a Dp-brane. Compactify $d$ spatial dimensions over a torus $T^d$. Suppose $d\geqslant p$, and that the Dp-brane is completely wrapped around the compactified dimensions. Look at the open ...
5
votes
3answers
289 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 ...
8
votes
0answers
565 views

String theory from a mathematical point of view

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 ...
0
votes
0answers
113 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 ...
3
votes
1answer
332 views

Mathematical definitions in string theory

Does anyone know of a book that has mathematical definitions of a string, a $p$-brane, a $D$-brane and other related topics. All the books I have looked at don't have a precise definition and this is ...
3
votes
1answer
270 views

what does holographic principle from string theory say about the possibilities of wormhole travel?

Is travel through stable macroscopic wormholes between remote points of spacetime going to be possible in a definitive theory of gravity, be it string theory or something beyond it? Physicists level ...
7
votes
2answers
388 views

Is there stringy Morse theory?

This question is pretty vague and open. I'm just curious if anyone has considered this. Morse theory has a nice physical formulation: a Morse function can be thought of as a potential, so the ...
2
votes
1answer
238 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 ...
3
votes
0answers
89 views

Schwarzschild radius in matrix models

The Schwarzschild radius for 11D BHs is given by $l_{11}(l_{11}m)^{1/8}$, which is the special case ($D=11$) of the general dimensional case of $(G_Dm)^{\frac{1}{D-3}}$. Here $m$ is the BH mass and ...
9
votes
3answers
197 views

Embedding of $F(4)$ in $OSp(8|4)$?

Is the superconformal algebra in five dimensions, $F(4)$, a subalgebra of the (maximal) six-dimensional superconformal algebra $OSp(8|4)$?
2
votes
1answer
155 views

M-theory on a Planck scale torus

We know that 11D M-theory is described by BFSS matrix model and for M-theory on a torus $T^p$ (at least for small $p$s) the description is given by SYM theory in $p+1$ dimensions by using the ...
2
votes
0answers
105 views

Superstring theory and renormalization [duplicate]

Possible Duplicate: Does the renormalization group apply to string theory? Renormalization in string theory QED and some quantum theories require renormalization techniques and take it as ...
4
votes
1answer
510 views

The Universe is a Hologram

First my background: no physics, but Ph.D. in math. I was reading this article on Slashdot. It links to this Wikipedia page. The content of the Slashdot article is that some physicists believe the ...
4
votes
1answer
128 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 ...
7
votes
1answer
130 views

Is the LEP B meson asymmetry evidence for higher dimensions and/or string theory?

According to this blog, new standard model calculations have changed the 3 sigma B meson forward and backward production asymmetry observed at LEP into two anomolies: A 2.5 sigma B meson production ...
1
vote
0answers
110 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 ...
1
vote
3answers
2k views

Relation between quarks and strings

In string theory(s), are quarks just individual strings, or are they made of multiple strings? Are the heavier quarks made of heavier or longer strings? Are there red, blue, and green strings ...
6
votes
2answers
388 views

Why is a stack of N D-branes equivalent to an extremal black brane?

A stack of N D-branes can have open strings ending on them. There is a U(N) brane gauge field, and r adjoint Higgs fields, with r equal to the number of transverse spatial dimensions. The eigenvalues ...
3
votes
1answer
112 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....
2
votes
1answer
220 views

“low-energy effective action” but in what sense?

In string theory, consistency with Weyl invariance imposes dynamics on the background fields through the vanishing of the beta functions. Those dynamics can also be derived from the so-called low ...
1
vote
0answers
97 views

Examples of manifolds and fluxes coming from generalized complex geometry

The paramount object in generalized gomplex geometry is the Courant algebroid $TM\oplus T^\star M$, where the manifold $M$ is called background geometry I think (I am not sure). More generally this ...
0
votes
1answer
76 views

Can we use some type of magnifying glass to magnifying gravity react on a body by theoretical physics?

Can we use some type of magnifying glass to magnifying gravity react on a body by theoretical physics? If so, could someone use it to destroy the earth
8
votes
1answer
412 views

Clarification on “central charge equals number of degrees of freedom”

It's often stated that the central charge c of a CFT counts the degrees of freedom: it adds up when stacking different fields, decreases as you integrate out UV dof from one fixed point to another, ...
2
votes
1answer
287 views

Black hole entropy

Bekenstein and Hawking derived the expression for black hole entropy as, $$ S_{BH}={c^3 A\over 4 G \hbar}. $$ We know from the hindsight that entropy has statistical interpretation. It is a measure ...