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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202 views

Why doesn't the anthropic principle select for N=2 SUSY compactifications with an exactly zero cosmological constant?

The party line of the anthropic camp goes something like this. There are at least $10^{500}$ flux compactifications breaking SUSY out there with all sorts of values for the cosmological constant. Life ...
2
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1answer
113 views

Spinors in more dimensions and new degeneracies?

As you more than probably know spinors dimensions go as $2^{\frac{D}2}$ in D spacetime dimensions. If we look at the peculiar case of D=2*4, spinors have 4 components and we usually say that's related ...
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2answers
438 views

Correlation functions in thermal field theory etc

Suppose I am studying a field theory at finite temperature or some black hole formation scenario from boundary theory perspective in the sense of AdS/CFT. How is it possible to gain information about ...
2
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1answer
317 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
137 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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43 views

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

From 't Hooft's String Theory lecture notes (paraphrased): To understand hadronic particles as excited states of strings, we have to study the dynamical properties of these strings, and then ...
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63 views

What exactly does it mean to wrap a D-brane or a M-brane in a Riemann surface $\Sigma_g$?

What exactly does it mean to wrap a D-brane or an M-brane in a Riemann surface $\Sigma_g$ ($g$ is the genous)? Is there some mathematical statement? And why do we get various supersymmetric gauge ...
2
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1answer
46 views

Extended SuSy from the kappa-Symmetry WZW terms

In José de Azcárraga, Jerome Gauntlett, J.M. Izquierdo, Paul Townsend, Topological Extensions of the Supersymmetry Algebra for Extended Objects, Phys.Rev.Lett. 63 (1989) 2443 (spire) it was ...
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87 views

Coulomb Branch vs. Higgs Branch (and the connection with D-branes, AdS/CFT)

I am confused about the difference between the Coulomb and Higgs branches of the moduli space of supersymmetric gauge theories. It's easy to find a definition for $D=4$, $\mathcal{N}=2$ supersymmetric ...
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76 views

Stack presentations and massive non-conformal theories

In the paper, Cluster Decomposition, T-duality, and Gerby CFT’s , by Hellerman, Henriques, Pantev and Sharpe, in the introduction it says: "Briefly, the idea is that nearly every stack has a ...
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65 views

Is time depending on the observer in string theory?

I heard that in the theory of relativity the time of an action is depending on the observer. But in string theory, is the time also depending on the observer? Are strings acting according to the ...
2
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2answers
103 views

Closed strings = open ones attached to a D0-brane?

I decided recently (to try) to learn String Theory, however from the beginning some newbie questions came up, which haven't given me a break. For this reason, I decided to ask some of them. I'd prefer ...
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82 views

BRST quantization of point particle

Suppose we have Lie algebra $\mathfrak{g}$ with basis $t_a$ with a representation $$ t_a \mapsto K_a: V \to V. $$ Denote by $c^a$ the dual basis. Chevalley differential is defined as $$ Q = c^i K_i - ...
2
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1answer
51 views

A paradoxical equation in RNS string fermionic part

It is well known for RNS string, $i.e.$, worldsheet supersymmetry formalism, the open string NS sector has worldsheet fermion expansion: \begin{equation} \psi^{\mu}_{\pm} = \frac{1}{\sqrt 2} \sum_{r ...
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0answers
58 views

Open string 4-tachyon amplitude for cylinder/annulus topology in bosonic string theory

One knows the formula for the open string $4$-tachyon amplitude for the disk topology in the bosonic string theory : it is proportional to the $s \leftrightarrow t \leftrightarrow u$ symmetrisation ...
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92 views

What is the future of complexity theory in black-hole physics and string theory? [closed]

I found the recent work by Hayden and Harlow and Susskind very fascinating. I have also heard talks by Scott Aaronson about this emerging connection. In particular this idea of understanding ...
2
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1answer
234 views

Higgs branch and Coulomb branch

I heard that the distinguish between Higgs branch and Coulomb branch is the limit of some parameters. (If i remember correctly, something like FI parameters. ) Here i want to know what is FI ...
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69 views

What is elliptic genera?

What is elliptic genera in physics? Reading many relevant papers, they just defined elliptic genus as sort of partition function. I try to find useful materials to explain it, but I couldn't find ...
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0answers
41 views

T duality for lower codimension branes or ALF spaces

These are purely mathematical questions in some sense but I believe this is relevant in string theory as the title says. I wonder if it is possible to perform T-duality of Taub-NUT space not along ...
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0answers
115 views

N=4 SYM from Klebanov-Witten field theory

This is with reference to M. J. Strassler's lectures on "The Duality Cascade" pg. 46. I want to see how $\mathcal{N}=4$ SYM emerges when D3 branes, in the KW setup, are placed at smooth point of the ...
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0answers
81 views

M-Theory and computer simulation

I have a question. Is it possible to perform computer simulations based on the M-Theory? I was looking for such simulators or source codes but I have not found anything. However, M-theory must have ...
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0answers
88 views

Open problems in string theory [closed]

I'm thinking of applying to do a PhD in String Theory. I'm gradually learning more about the subject through external reading, but still most papers are impenetrable. Could anyone give me a ...
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0answers
44 views

Existence and Uniqueness of spurious states in Bosonic String Theory

Green, Schwarz and Witten introduce so called spurious states $\phi$, that fulfill $$ (L_0 -a )\phi = 0\quad \text{and} \quad (\phi,\psi)=0 \text{ for all physical states }\psi $$ where the $L_n$ are ...
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0answers
35 views

What is the X(t) dependence of the ends of stretched Nambu-Goto string?

I'd like to have an expression for the velocity of an end of an open string being contracted due to it's tension. Not that of transverse oscillations, which seems to be the velocity of light, but ...
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61 views

Proof the superstring action is Weyl invariant

The superstring action is: $$ S = k\int \mathrm d\sigma \sqrt{-h} \left [ h^{\alpha \beta} \partial_\alpha X^\mu \partial_\beta X_\mu + 2i {\bar{\psi}} ^\mu \rho^\alpha \partial_\alpha \psi_\mu - i ...
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51 views

How does one expand gravity Lagrangians about an $AdS$ background?

I had previously asked this question. This is kind of a continuation of that. I recently found this expression which seems to be called the "Fierz-Pauli action" which is apparently the quadratic ...
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0answers
58 views

Anomalies from a Renormaization Group Equation (RGE)

This is an approach to anomalies which seems unfamiliar to me.. Firstly what is this function $W$ which seems to satisfy the equation, $\frac{\partial W }{\partial g^{\mu \nu} } = \langle T_{\mu ...
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0answers
37 views

What is 'heterotic string compactification'?

I've read that some exceptional groups arises in the context of 'heterotic string compactification'. Could someone explain (to a person studying physics but who doesn't know string theory) what ...
2
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0answers
310 views

Loop-Quantum Gravity versus String Theory [closed]

Basically asking what were the motives behind each theory. What was it that lead physicists toward these ideas?
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65 views

Why are string theorists interested in entanglement entropy?

I have been reading some papers by Ryu-Takyanagi but I am not seeing a good explanation as to why entanglement entropy of the boundary CFT is a good observable to probe the possible bulk quantum ...
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0answers
70 views

Is the cross section of a relativistic water hose or string always a perfect circle?

Given is a very long tube, such as a water hose or a tubular string with finite thickness, that has a constant circular cross section of radius $r$ along the length and that is at rest in an inertial ...
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60 views

String Vertex Operators in Light Cone Gauge

I have a basic confusion about how to compute string scattering amplitudes in light cone gauge, using the operator formalism reviewed in GSW. I am familiar with the covariant gauge formalism, where I ...
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73 views

Relation between holography and matrix models

Let's consider a 0-dimensional $N \times N$ Hermitean one matrix model. It is defined by a potential V(M). Its partition function is $Z = \int_{H_{N}} dM e^{-\frac{1}{g}V(M)}$ where $H_{N}$ is the ...
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345 views

BICEP2 and string theory

Can anybody elaborate on the implications of the BICEP2 result for string theory? The discussion here What experiment would disprove string theory? suggests that refuting string theory is rather ...
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0answers
15 views

Using the boundary states, is there a precise way to write down a planar open string multi-loop amplitude as a closed string tree amplitude?

The only explicit computation I have seen is the planar 1-loop one, but there should be a way to write the multi-loop case in terms of boundary states as well.
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40 views

Is brane world scenario in contrast with inflation theory? [closed]

Is brane world scenario in contrast in some way with inflation theory ?
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0answers
37 views

What is the constant appearing in the low energy action?

Usually one finds this expression for the low energy action $$S = \frac{1}{2\kappa_0^2}\int d^D X\; \sqrt{-G}\; \mathrm{e}^{-2\Phi}\,(R-\frac{1}{12}H_{\mu\nu\lambda}H^{\mu\nu\lambda}+4 ...
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0answers
64 views

Why does the object $\epsilon_L Q_L + \epsilon_R Q_R$ correspond to a 16-component conserved supercharge when we have a Dp-brane?

I understand that when a 10-dimensional superstring theory has a Dp-brane (say, extending in the $x_0, ... , x_p$ directions) we have the total conserved supercharge given by: \begin{equation} ...
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0answers
56 views

Stringy corrections to Friedmann equation

Does anyone know a reference or a paper which discusses string theory correction to Friedmann equations?
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93 views

Regulating an infinite sum in the $bc$ CFT

The EM tensor of the $bc$-CFT is $$ T(z) = \colon \partial b c \colon - \lambda \partial \colon b c \colon $$ After expanding in a mode expansion, we find $$ T(z) = \sum_{m} \frac{1}{z^{m+2}} \sum_n ...
2
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1answer
70 views

Explicit calculation of bosonic string Weyl invariance at one loop

I have been trying to do all the calculations in the Green, Schwarz and Witten Superstring Theory textbook. At the end of chapter 3, the author did one-loop calculation for Weyl invariance for the ...
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40 views

Lorentzian interpretation of open-closed string duality

In open-closed string duality, we can reinterpret the one-loop open string diagram (an annulus or cylinder) as a propagating closed string, depending on the direction in which we take time to be. This ...
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61 views

Question on Tachyon Correlator (GSW)

I'm reading through chapter 7 of Green-Schwarz-Witten and I have a problem with the derivation of the M-tachyon correlation function. Basically I'm trying to get 7.A.17 from 7.A.12 and eq 7.A.22 in ...
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0answers
100 views

A question about inverse Green's function

(The background is in a book, An introduction to String Theory and D-brane Dynamics 2nd, by Richard J Szabo p87, Eq. (6.31)) Given $$N(\theta,\theta')= - \frac{1}{\pi} \sum_{n=1}^{\infty} \frac{ ...
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0answers
66 views

State space of strings: Spin-1 particles in the conformal gauge?

I obviously have a problem with basics of group theory. consider an open string in flat spacetime. there are usually two common gauge to solve the classical problem and quantize the strings: ...
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134 views

Generalisations of AdS/CFT with string theory on both sides

From my previous post, I found out from the comments that there are various generalisations of AdS/CFT with different things replacing the CFT on the RHS; such as AdS/CMT, AdS/QCD, and also with ...
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60 views

About the most general (diff$\times$Weyl)-invariant and Poincare-invariant form of action

I have a question about the most general (diff$\times$Weyl)-invariant and Poincare-invariant form of action. In Polchinski's string theory p15, there is an action for manifold without boundary ...
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35 views

Moduli potential in Type IIB String Theory

In the book String Theory and M-Theory by K. Becker, M. Becker and J.H. Schwarz: Why is the potential for moduli given by eq (10.168): $$\tag{10.168 }V(T,K) ~=~ \frac1{4\mathcal{V}^3} \Big( ...
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328 views

What are the basic postulates of string theory? [closed]

I read the Popular Science books, The Brief history of time (Hawking), The fabric of the cosmos (Greene), and The Grand Design (Hawking), etc. but did could not manage to understand what string ...
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104 views

Deriving the critical dimension of bosonic string theory

I am going through the lecture note by Gleb Arutyunov on the derivation of critical dimension for bosonic string theory. I was able to reproduce all the results till the last step given on page 62. ...