Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [string-theory]

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.

0
votes
0answers
39 views

two-dimensional bosonic field theory

I'm struggeling with the following question: Consider a two-dimensional bosonic field theory defined by the following action $S =\frac{k}{2} \int dx_{1}dx_2 [(∂x_1 φ(x_1, x_2))^2 + (∂x_2 φ(x_1, x_2)...
0
votes
0answers
10 views

IIB Supergravity from worldsheet (super)conformal invariance of Green-Schwarz string

After reading this question How are low energy effective actions derived in string theory? I began to wonder what is the coupling of the string to the other sugra fields. In almost all textbooks ...
2
votes
2answers
64 views

Role of AdS/CFT correspondence in the context of integrability

I was wondering how the AdS/CFT correspondence fits in the context of integrability. As I understand, the AdS/CFT correspondence postulates a duality between gravity theories and CFT's. If one theory ...
2
votes
1answer
25 views

Stress-Energy Tensor and Conformal Invariance in String Theory

Since the Euler-Lagrange Equations corresponding to the Polyakov Action implies no dependance on the auxillary metric we arrive at the constraint $T_{ab}=0$. We then change to lightcone coordinates $++...
0
votes
1answer
31 views

In M-Theory are membranes excited states of a field? [duplicate]

Are M2 and M5 membranes in M-Theory excited states of some underlying field, or are they fundamental? In what sense are membranes solitonic? In the reference question, someone made a comment that had ...
0
votes
2answers
58 views

The Strings have a finite size they can vibrate?

as I searched about the Strings theory I found out this explanation: Since the strings have a finite size they can vibrate. All the known particles of nature are just different modes of vibration of ...
-1
votes
1answer
95 views

Should I change my major from physics to math? [closed]

Right now I majoring in physics, but i just realized that the physics program in my university is just for people who want to become experimental physicists and you can clearly notice that in the ...
-1
votes
1answer
37 views

Photon wavelengths/frequencies in String Theory

How are different photon wavelengths explained with String Theory? From what I understand, a photon is a string with a particular configuration. Are all photon strings identical? There are photons in ...
0
votes
0answers
34 views

Particle spectrum in dimensional reduction

First of all, sorry if this question is a bit stupid, but my knowledge of certain aspects of particle physics and group theory is a bit limited. I am compactifying the heterotic $E_{8}\times E_{8}$ ...
0
votes
0answers
54 views

Biggest string theory competitors

i am a layman in physics and i just want to know what are, as of today, the most importants framework for quantum gravity that contrast string theory and why is so?
0
votes
3answers
63 views

Electron repulsion in String Theory? [closed]

How electrons repuls each other in String Theory? Is this the same mechanism as in QFT?
-3
votes
1answer
75 views

Does string/M-theory provide a solution to the dark matter/energy problem?

Would string theory or any other propesed UFT help explain, at least in theory what the other 95 percent of matter and energy in the universe are about? It seems as thaugh there is a reacurring theme ...
0
votes
0answers
43 views

Coulomb forces in String Theory

In QED electrostatic forces are mediated by field theoretic effects known as virtual "particles" if I am not mistaken, but I don't know how string theory explains electrostatic interactions between ...
1
vote
0answers
42 views

What is the relation between a $D_2$-brane and an $M2$-brane?

I am only familiar with the concept of a $D_2$-brane from a first course in String theory. I would like to learn, at least on a conceptual level, what an $M2$-brane is and what is its relation to the $...
0
votes
0answers
49 views

Does anyone know how to symmetrize $\gamma$-matrices?

I'm trying to construct the SO(5, 5) $\gamma$-matrices which are real and symmetric. Recently, I have 6 symmetric and 4 antisymmetric $\gamma$-matrices ($6_S + 4_A$ representation). How can I ...
0
votes
0answers
30 views

Unitary representations of a Kac-Moody algebra

I am reading one of the original papers about the GKO construction. They say that a representation of the (untwisted) Kac-moody algebra $\hat{g}$ is one where the generators are such that $T^{a\dagger}...
2
votes
0answers
44 views

Where does the string worldsheet live?

Suppose you define a Euclidean two-dimensional CFT for a scalar field $X$ of dimension length, $$ S = \int d^2x h{}_{\mu\nu} \partial^\mu X \partial{}^\nu X \, , $$ and $h{}_{\mu\nu}$ is the metric of ...
0
votes
0answers
23 views

Derivation for the commutation relation of $\alpha_m^\mu$ and $\alpha_n^\nu$

I have been trying to derive the commutation relation of $\alpha_m^\mu$ and $\alpha_n^\nu$ in a closed-string mode expansion, but I found an extra factor of $2$ that ruins things out: Given $\dot X = ...
0
votes
1answer
47 views

What will happen to these colliding strings?

What happens when these two strings collide? Do they cancel each other out, pass through each other or interact in some way? Thanks.
0
votes
0answers
29 views

Einstein Field Equation for a Garfinkle-Horowitz-Strominger theory

When deriving the Einstein field equation from a theory with a dilaton field, we have: GHS's calculation However, in my calculation: My calculation So I found that GHS has missed $R$ and $(▽φ)^2$. ...
1
vote
0answers
60 views

If spacetime is emergent, are strings and branes in String/M-Theory also emergent?

Many physicists including string theorists say that spacetime is emergent from something more fundamental. String theory says strings and branes are fundamental, or in the case of M-Theory, membranes ...
2
votes
1answer
92 views

Why do we say that AdS/CFT is a background independent definition of string theory?

It is usually said that AdS/CFT is a background independent definition of string theory, how this concept emerge from the AdS/CFT correspondence? We can define string theory on other manifolds ...
1
vote
0answers
32 views

Kinematic aspects of quantum gravity

Quantum gravity proposals at the leading perturbative order, such as the quantisation of linearized gravity, or the low-energy effective action like in string theory, provide the dynamics for the ...
2
votes
1answer
51 views

Quantum expressions for the Virasoro constraints

I am trying to derive the quantum form of the Virasoro constraints. $$ L_{m} = \frac{1}{2} \sum_{n} :\alpha_{m-n}.\alpha_{n}: $$ :...: meaans normal ordering. Using the common commutator between ...
1
vote
1answer
35 views

What superstring or brane phenomenology can be observed in LHC heavy ion collisions?

What superstring or brane phenomenology can be observed in heavy ion collisions at the LHC energy densities. Of course, I am aware that LHC experiments can constrain the conclusions from the ...
1
vote
0answers
66 views

Does a Black-hole Represent a Limit To The Value of Energy-density? [closed]

I've recently read an article that stated the singularity of a black hole could be a string, which is stipulated to be pure energy. If that's the case, does this mean that the singularity of a black ...
0
votes
0answers
23 views

What is the simplest possible explanation of the String Theory? [duplicate]

I was recently reading through 'The Little Book of String Theory' by Steven S. Gubser, and found it too complicated. Now, some people may say that the string theory is meant to be complicated as even ...
1
vote
0answers
36 views

Penrose diagram of Janus black holes

Recently I'm interested in the Janus black holes, it's a solution of three dimensional Einstein-scalar action which can be embedded in ten dimensional type IIB supergravity with appropriate ansatz. ...
2
votes
1answer
93 views

Why can AdS/CFT correspondence be applied to condensed matter systems when their space is not anti-deSitter?

The AdS/CFT correspondence postulates a duality between string theory of gravity and a CFT on an AdS background. This duality is employed in some condensed matter systems. I was wondering why it is ...
3
votes
1answer
44 views

Relationship between compactification moduli and generations in standard model

The situation I am describing is a $10D$ heterotic string theory which is compactified on a Calabi-Yau to get a $N=1$, $4D$ effective theory. It is mentioned in Ashoke Sen's notes on string ...
2
votes
1answer
67 views

Are there other types or versions of holographic principle?

Holographic principle (https://en.wikipedia.org/wiki/Holographic_principle) establishes a correlation between a bulk and its boundary. It says, in layman terms, that the amount of information in a ...
2
votes
1answer
55 views

Energy of string in bosonic string theory

When we start from the Polyakov action, we can choose to work in the conformal gauge $h^{\alpha\beta}=\eta^{\alpha\beta}$ where $h^{\alpha\beta}$ is the metric on the world-sheet and $\eta^{\alpha\...
2
votes
1answer
85 views

Does string theory violate general covariance?

In a 2007 note on ArXiv, it said: String theory unifies all interaction but provides a perturbative background dependent formulation which violates general covariance. However, another 2012 paper ...
4
votes
0answers
44 views

Does the background shift affects the renormalization group equations?

In Section 21 of "Quantum Field theory" by Mark Srednicki, it is shown that there are two equivalent ways to get the quantum action of the shifted field $\phi'= \phi-\tilde{\phi}$, where $\phi$ is the ...
1
vote
1answer
97 views

Do strings propagate through space time or do they make space time?

In the beginning of string theory textbooks, strings are said to live in a background "target" space time. They then propagate through this space time. Strings also have a spin 2 ("graviton") mode, ...
1
vote
1answer
45 views

Are the “extra dimensions” in string theory universal?

Are the extra (compactified) dimensions from string theory universal, in that any particle/field with a sufficiently small enough wavelength will be able to propagate through them? The reason I want ...
7
votes
3answers
258 views

Does string theory accommodate effects of dark energy?

String theory is arguably, among best candidates for a Theory of Everything. So, because every TOE is an attempt to bind together the big and very small effects and things, a TOE must be able to ...
1
vote
0answers
28 views

Aharony-Bernman-Jafferis-Maldacena (ABJM) and k=1 Chern Simons matter

I have read recently that the partition function / half-BPS wilson vev (w/ NG probe) of a Chern-Simons matter theory with N=6 U(N)k x U(N)-k super-conformal symmetry (ABJM) on S3 is proportional to ...
0
votes
0answers
23 views

Resources on Gubeser-Klebanov-Polyakov (GKP) strings and N=4 Super-Yang Mills dual description

*I have learned recently that the Gubeser-Klebanov-Polyakov string / folded string in AdS3 (if I recall correctly, and I assume with some additional virasoro constraints, etc) is dual to large-spin ...
0
votes
0answers
49 views

Understanding Moonshine via Heterotic E8xE8 (resubmitted, originally asked on mathematics stack exchange)

Recently I have become familiar with the conjectured relationship of monstrous moonshine and pure (2+1)-dimensional quantum gravity in AdS with maximally negative cosmological constant and, it’s being ...
1
vote
2answers
88 views

Where is the Physical Singularity under the Holographic Principle?

From this article, it states that The holographic principle states that the entropy of ordinary mass (not just black holes) is also proportional to surface area and not volume; that volume itself ...
1
vote
1answer
53 views

Mass formula for open string with mixed boundary conditions

I want to give an expression for the mass formula of an open string with has Neumannn condtion in $m$ directions and Dirichlet in $n$ directions $X^{i}(\sigma ^{1}=0)=x_{0}^{i}, X^{i}(\sigma ^{1}=\pi)=...
0
votes
0answers
55 views

How does Alain Connes NCG compare phenomenologically with superstring theory?

In Veltmans book on QFT, diagrammatica, the full SM Lagrangian is published. There are more than a hundred terms and it looks pretty uninspiring and not quite the kind of equation one would want to ...
4
votes
0answers
147 views

Free Field Realization of Current Algebras and its Hilbert space

I have some conceptual confusion regarding the interplay between current algebras, their free field representation and the Hilbert space generated from it. Let's sketch a simple example, $\mathfrak{...
2
votes
1answer
64 views

If strings of matter are of the same substance how can matter carry differing charges?

Considering that a string is a loop of energy composed of the same underlying material how is it possible for it to be either positively or negatively charged? For that matter, how is it possible for ...
0
votes
1answer
40 views

Generalization of Chern-Simons Wilson Line

The Wilson line in Abelian Chern-Simons theory is $$\langle\exp\left(i\int dt\dot{x}^{\mu}A_{\mu}\right)\rangle=\int\mathcal{D}A\exp\left(i\int dt\dot{x}^{\mu}A_{\mu}+\frac{i}{4\pi}\int A\wedge F\...
0
votes
1answer
43 views

Root weights and states in orbifold compactifications

I have the following question regarding orbifold compactifications of the heterotic string: What is the relation between a certain representation and the weights of the root lattice? I mean: take ...
1
vote
1answer
45 views

Question about Mode expansion of free compact boson

$(1+1)$-Dim free compact boson, Lagrangian is $$\mathcal{L}= \frac{1}{2}(\partial_\mu\phi(\sigma,t))^2$$ with $\phi(x,t)\sim\phi(x,t)+2\pi r$ and periodic boundary condition along $x$, i.e. $\phi(\...
0
votes
0answers
19 views

Branes without Fayet-Iliopoulos term

Often D-brane effective actions are given as (let's take D3-branes) $$ S=-T\int d^4x \sqrt{-det(g_{mn}+2\pi\alpha'F_{mn})}. $$ After expansion in $2\pi\alpha'$ there is a constant Fayet-Iliopoulos ...
3
votes
1answer
57 views

What happens to the $U(1)$ factor in the $U(N)$ SYM gauge group of the AdS/CFT correspondence?

I'm learning about the AdS/CFT correspondence. I know that from the open string perspective, the dynamics on a stack of $N$ coincident $D3$-branes is given by a $\mathcal{N} = 4$ Super Yang Mills ...