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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2
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19 views

Multi-Cut Matrix Models

I have a question pertaining specifically to a one-matrix model with a multi-cut solution. The standard procedure is to take a polynomial superpotential $W(x)$. In the classical limit (analogous to $...
-3
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0answers
18 views

Are electrons packets of energies made up of strings? [on hold]

I always wondered that if electron was a packet of energy it would hold true for most of the experiments and we won't need to deal with wave particle duality anymore,but then matter came in.what if ...
4
votes
2answers
111 views

What does string theory predict for the singularity inside a black hole?

The usual explanation for what's going on inside a black hole goes something like "General Relativity predicts a singularity with infinite curvature, but when matters gets so tightly compressed we ...
6
votes
2answers
240 views

From Quantum Mechanics to Quantum field theory to String theory?

Today during a very "unique" study session, I might have internalized why Quantum mechanics was not enough, and Quantum field theory makes sense. It seems the reasons are that When a potential is ...
0
votes
1answer
62 views

About the non-locality of gravitational energy 2

Gravitational energy is non-local which is essentially because of the equivalence principle. The equivalence principle says that you can always transform your frame so that you feel like in a ...
0
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0answers
30 views

OPE coefficents and commutation relations, and OPE with stress tensor

Basic question about conformal field theory: In a conformal field theory in $d\geq 3$ dimensions, what is the relation between commutation relations and OPE coefficients? In particular, because ...
0
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0answers
22 views

T-duality between $E_8 \times E_8$ and $\text{Spin(}32)/\mathbb{Z}_2$ heterotic strings at the $\sigma$-model level

I would like to understand how T-duality between the heterotic $E_8 \times E_8$ (HE) and heterotic $\textrm{Spin}(32)/\mathbb{Z}_2$ (HO) theories works, at the level of the worldsheet $\sigma$-model. ...
6
votes
2answers
316 views

Why does the non-linearity of the string action prohibit stretching due to strong excitations?

From 't Hooft's String Theory lecture notes on page 8 (paraphrased): To understand hadronic particles as excited states of strings, we have to study the dynamical properties of these strings, and ...
-1
votes
1answer
34 views

Do Quark confinement prevents proving strings? [closed]

In baryons like protons,neutrons;isolated quark doesn't exist due to quark confinement. We will need an infinite energy to pull quarks apart.Even if we try to pull them apart there will be pair ...
2
votes
1answer
109 views

Normal Ordering in String Theory: Polchinsky vs. all others

Polchinsky defines normal ordering in string theory as: $$:X^\mu(z,\bar z)X^\nu(w,\bar w): = X^\mu(z,\bar z) X^\nu(w, \bar w) + \frac{\alpha'}{2} \eta^{\mu\nu} \log |z-w|^2$$ and for more ...
1
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0answers
34 views

Ramond-Ramond potential and field strenght

I have a doubt about R-R potential in Superstring theory. The known facts are (according many books, for example "Basic Concepts in String Theory" by R. Blumenhagen, D. Lüst and S. Theisen): in the ...
2
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0answers
35 views

Which supersymmetry principles make the axio-dilaton field in F-theory holomorphic?

I am following the lecture notes on F-theory by T. Weigand . On page 7 he states that when considering F-theory as the strong coupling limit of type IIB orientifolds with D-branes, the axio-dilaton ...
-1
votes
1answer
46 views

How do comparatively larger particles arise from vibrations of infinitely smaller strings?

In String Theory, how can a string as infinitesimally small as the Planck length, manifest itself as a much larger and massive particle?
2
votes
1answer
83 views

What particles are closed strings?

In String Theory, I understand that gravitons are particles that are closed strings. Are there other particles that are manifested from closed strings?
5
votes
1answer
154 views

Superconformal approach to supergravity

In the book (Supergravity - Daniel Z.Freedman & Antoine Van Proeyen - Cambridge), there is (Chapters 16-17) a presentation of pure supergravity or supergravity with matter, from a superconformal ...
1
vote
1answer
51 views

How to calculate the free energy in curved space?

To study the Hagedorn temperature of string near a black hole, we need to calculate the free energy in curved space. This is can be done calculating a torus path integral, but I want to know if an ...
1
vote
1answer
35 views

What is the spin of the Kalb-Ramond field?

In bosonic string theory the massless states of the closed string are given by a rank 2 tensor, which is divided into its three irreducible spherical tensors: symmetric traceless, antisymmetric and ...
0
votes
1answer
39 views

Do Calabi -Yau shapes also influence a strings particle identity?

Since strings reside on the surface of a d-brane, and it' a three dimensional hyperspace, are their manifestations as certain particles also influenced by Calabi Yau Spaces? Could the way strings ...
3
votes
2answers
62 views

Question about notation used in writing the moduli space in string theory

In physics papers, particularly those by Aspinwall, or textbooks, I encounter things like $$\mathcal{M} \simeq O(\Gamma_{4,20})\setminus O(4,20)/((O(4)\times O(20))$$ For instance, this is from ...
5
votes
2answers
103 views

String quantization and Malament's theorem

Malament's theorem posits that, given a few assumptions on relativistic QM, it is impossible to have localized particles. For $E_\Delta$ the proposition that a particle is certain to be found within a ...
0
votes
3answers
96 views

In String Theory, can some particles contains multiple strings? [closed]

According to String Theory, can a particle consist of more than one string? I can visualize elementary particles, like leptons, being composed of a single string. But what about composite particles, ...
2
votes
0answers
47 views

Reference for orbifolds in string- and M-theory

A number of orbifold constructions have been studied heavily in string- and M-theory over the years, establishing various dualities between different theories. Can someone point me to a slightly more ...
3
votes
1answer
50 views

Problem obtaining string equations from Polyakov action [closed]

I am trying to obtain the string equations of motion from the Polyakov action in the conformal gauge, i.e.: $$ S=T\int{d\tau d\sigma (\dot{x}^2-x^{'2})}\equiv\int{d\tau d\sigma \mathcal{L}} $$ where ...
8
votes
1answer
153 views

Why are WZW models interesting?

I realise this is a very broad question, but when I was studying for my thesis I came across WZW models a few times and I never quite understood them. So, I understand that these models describe ...
1
vote
1answer
164 views

Generalized spin connection and dreibein in higher spin gravity

I am studying 3D higher spin gravity and I would like to know the mathematical and physical meaning of generalized spin connection and generalized dreibein that appear in this theory. It is well known ...
3
votes
1answer
44 views

How many orientifold planes does one need?

According to the book ''String Theory in a Nutshell'' by Elias Kiritsis (page 204, linked here), the tension of an $Op$-plane is $$T_{Op} = -2^{p-4}T_{Dp}$$ With this picture, one gets -- for type ...
2
votes
1answer
36 views

Exchanging a local operator with a path integral

I am reading a paper by J. Polchinski, called "What is string theory", hep-th/9411028. In eq. 1.1.9, and the line before it, the author seems to have used: $$\langle \partial_z \partial_{\bar{z}} X(z,...
4
votes
3answers
303 views

Fundamental Constants in a theory of everything (TOE)

Do physicists ever expect to be able to derive the fundamental constants of nature from theory? For example, if string theory or some other theory unites the four forces, would the theory be ...
4
votes
0answers
53 views

For intersecting branes, are we allowed to compactify on a torus such that one of the branes becomes dense in it? What is the result?

The story of how to get chiral fermions in the low-energy effective theory of a string theory with intersecting branes goes something like this: At the point of intersection of two branes, a direct ...
1
vote
1answer
36 views

p-cycles and Fluxes

I would like to ask why the existence of a non-trivial p-cycle leads to a non-trivial flux. I would say that e.g. for a five-form $F_{(5)}$ field strength , the flux is: $$\int\limits_{\mathcal{C}^{5}}...
2
votes
1answer
29 views

Multi-center Taub-NUT geometry and homologically nontrivial cycles

In the string theory book by Ibanez and Uranga (click here for the Google books excerpt), the four-dimensional multi-center Taub-NUT metric is written as $$ds^2 = \frac{V(\textbf{x})}{4}d\textbf{x}^2 ...
1
vote
0answers
15 views

Query about Ramond-Ramond fluxes associated with a Dp-brane

A paragraph in the string theory book by Ibanez and Uranga (String Theory and Particle Physics by Luis Ibáñez and Angel Uranga) has confused me. According to the book (for a screenshot of the ...
5
votes
2answers
56 views

Why cannot a fundamental string couple to the R-R gauge field $C_{\mu\nu}$?

People usually say that D-branes can carry R-R charges, or can couple to R-R sector gauge fields. But why a fundamental string cannot couple to a 2-form R-R sector gauge field? What's the essential ...
3
votes
0answers
55 views

Higgs mechanism in quantum GLSM

My question is regarding the following Gauged Linear Sigma Model (GLSM) in two dimensions. $$\tag{1} S=\int d^2x\Big(-D_{\mu}\overline{\phi} D^{\mu}\phi +\frac{D^2}{2e'^2} +D(|\phi|^2-r)\Big).$$ ...
4
votes
1answer
75 views

What, exactly, is a “delta function p-form” as used in the theory of branes?

In string theory, when dealing with branes, the following happens: We rewrite a worldvolume action $S = \int_{\Sigma_{p+1}} \omega^{(p+1)}$ of a $D_p$-brane as an integral over the whole $\mathbb{R}^{...
1
vote
0answers
94 views

Question on $E_8$ and twistor space [closed]

The Kahler $4$ form constructed from two-forms $\{\alpha, \beta\} \in H^2(M,\mathbb Z)$, and $M$ a $4$-manifold, is induced by $\alpha\wedge\beta$ with the map $H^2(M, \mathbb Z)\otimes H^2(M, \mathbb ...
0
votes
0answers
34 views

Confusion regarding Vacuum fluctuations, Strings & The Casimir Effect

From Wikipedia: Casimir Effect The typical example is of the two uncharged conductive plates in a vacuum, placed a few nanometers apart. In a classical description, the lack of an external field ...
1
vote
1answer
36 views

Enhanced D-Brane Gauge Symmetry and the string decoupling limit

Consider a system of $N_C$ $Dp$-branes (in Type IIA or Type IIB string theory, depending on whether $p$ is even or odd). In the Les Houches lectures on supersymmetric gauge theories by Berman and ...
5
votes
1answer
119 views

Gravitational wave and string theory

I'm new to physics and have been reading about fundamental and textbook physics text, which is the Young & Freedman University Physics (good book). I'm little skeptical towards string theory as ...
3
votes
0answers
41 views

Can random walks be applied to String Theory in curved space?

If we study the high temperature limit (near Hagedorn) of a string gas, most of the energy is concentrated in a single long string. If we model the string by a fixed number of rigid links of length ls ...
1
vote
1answer
102 views

Polyakov From Nambu-Goto Directly, for Strings?

The following derivation, for a classical relativistic point particle, of the 'Polyakov' form of the action from the 'Nambu-Goto' form of the action, without any tricks - no equations of motion or ...
2
votes
2answers
220 views

How to find the rank of the matrix $\frac{\partial ^2\mathcal{L}}{\partial \dot{X^\mu} \partial \dot{X^\nu} }$ for the Nambu-Goto string Lagrangian?

In this case $$\mathcal{L}~=~-T\sqrt{-\dot{X^2}X'^2+(\dot{X}\cdot X')^2}.$$ I was reading some books and papers about the constraints in the Nambu-Goto action, and all of them say something like ...
3
votes
1answer
367 views

Reduction of Nambu Goto action to true degrees of freedom

First consider the particle $$S=m\int\sqrt{-\dot{X}^2}d\tau$$ if you choose the static gauge $\tau=X^0$ and replace it in the action you get $$=m\int\sqrt{1-\dot{X}^j\dot{X}^j}d\tau$$ So now, you ...
10
votes
1answer
327 views

Could string theory be an effective theory?

I know that many quantum field theories could be low-energy effective theories in String Theory (ST), but I've also read and heard that ST cannot itself be an effective theory. I suppose this has ...
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0answers
27 views

What is the origin of the five-form field in bubbling Ads geometries?

I have been reading the paper: Bubbling Ads space and the 1/2 BPS geometries[hep-th/0409174]. In the paper they look at 1/2 BPS states in the field theory which are dual to D3 branes IIB supegravity. ...
1
vote
1answer
43 views

What relative effects be for object with near light speed velocity in compactified dimensions?

What relative effects be for an object with near light speed velocity in compactified dimensions? Does gravity increase the same as for an object with near light speed velocity in usual spacial ...
3
votes
1answer
56 views

D-branes conserving only half of the supersymmetries

Concerning D-branes as BPS states from T-duality. In D-Branes by Johnson (and other sources) I find the following statement (p.196): "Only the total [supersymmetric] charge of $Q_a+\tilde{Q}_a$ of ...
1
vote
0answers
44 views

Why RR cohomology is important in string theory?

I want to know the RR cohomology in string theory or topological field theory in detail. (RR stands for Ramond Ramond). In following papers they compute the nilpotency of differential operator for RR ...
0
votes
1answer
61 views

Question about a formula in the book by Green, Schwarz, Witten

In chapter 7 of superstring theory, it is written $$ g\langle0;k_1|\zeta\cdot\alpha_1V_0(k_2)\zeta_3\cdot\alpha_{-1}|0;k_3\rangle=g\langle0;k_1|\zeta\cdot\alpha_1e^{k_2\cdot\alpha_{-1}} e^{-k_2\cdot\...