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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15 views

C.o.m. position and total momentum of open DD string

I'm trying to calculate c.o.m. position $q_\text{DD}^\mu$ and total momentum $p_\text{DD}^\mu$ of the open string with Dirichlet boudnary conditions on both ends. Something is going very wrong though. ...
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1answer
47 views

STU-model for Black holes

In string theory in the realm of black holes, what does the acronym STU stands for when we talk about the STU model?
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1answer
73 views

Why do people care about Mathieu groups and related things? (Something about monstrous moonshine)

Before I begin, let me say I don't know anything about what I am asking. This morning for somewhat random reasons I decided to google moonshine and related things. As it were I discovered my ignorance ...
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0answers
29 views

Blackhole microstate counting

It's widely belived that p-branes and Dp-branes are the same objects in string theory. P-branes are charged solutions of type IIB supergravity that have the topology of a black hole, one would expect ...
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1answer
41 views

Non-perturbative Brane effects

In Johnson's Book about D-branes he gets the Tension of a D brane: $$\tau_p = \frac{\sqrt{\pi}}{16 \kappa_0 g_s}(4\pi^2\alpha')^{(11-p)/2}$$ By performing a string amplitude calculation and ...
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54 views

Physical meaning of the Morse functions? [closed]

What is the physical correspondence of the Morse functions in a physical system? Currently I am studying Mirror symmetry but I can not get a physical intuition out of it.
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0answers
96 views

What is the justification for continuing to model space-time as a manifold in string theory?

Background The question I have arises from taking seriously the idea that, in a physical theory, one should first define all physical quantities via (thought) experiment. Justification and ...
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0answers
82 views

What is the status of Lorentz Invariance in String Theory ? Is it global or local?

The questions is simple, what is the status of lorentz invariance in string theory ? Is it global or is it only local ? The proof of absence of anomalies assumes lorentz invariance. However, I believe ...
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0answers
25 views

Manifold corners and M theory

I am currently trying to understand a paper by Hisham Sati on manifold corners and M theory. The background is that M theory admits manifolds with corners. One of the results in the paper is that the ...
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1answer
50 views

Energy density of a 1D string?

As I understand there is a problem in physics where point-like massive (or charged, etc.) particles would have infinite mass/energy (or charge, etc.) density. I'm curious how in the context of String ...
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0answers
49 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 ...
2
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0answers
63 views

What is the “single equation” in string theory that's an inch long? [duplicate]

Michio Kaku, famous theoretical physicist claims to be one of the founders of string field theory and to have contributed a equation that's "no bigger than your thumb" that ties general relativity and ...
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1answer
99 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 ...
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0answers
57 views

Can anyone explain the Matrix version of M-Theory?

I am trying to understand "Matrix-Theory" (the version of M-Theory which describes the theory in the infinite momentum frame). I tried to read Susskinds original paper on it but it doesn't make any ...
2
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1answer
174 views

How much QFT do I need to get started on String Theory? [closed]

I want to get started learning String Theory (most likely from David Tong's lecture notes) and I would like to know which topics I need to know from QFT. In particular, if I were to follow Peskin, ...
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0answers
41 views

Can the KLT low-energy limit relations be obtained without string theory?

The KLT (Kawai-Lewellen-Tye) relations roughly say that -at the tree level- closed string amplitudes equal open string amplitudes squared and in the low-energy limit this becomes a "Gravity = Gauge ...
3
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0answers
43 views

Direction about future [closed]

I am finishing high school this year and i want to be a theoretical physicist. My academic result in mathematics is not good throughout last 5 years. But physics is my dream. I want to overcome every ...
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1answer
199 views

Why doesn't gravity fit into quantum theory?

Before you read, I want to point out that I probably don't know nearly as much as you guys about quantum theory, even though I love learning about it, so I would prefer explanations in relatively ...
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1answer
59 views

How does this quantisation relation come about?

I'm currently doing a course in string theory and in the lecture notes it is stated: $$ [x^-, p^+]~=~-i \tag{1}$$ I am fine with this. However, after trying (and failing) a question, I looked at ...
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1answer
137 views

What does the finding of gravitational waves mean for M Theory? [duplicate]

I was wondering if the finding of gravitational waves proves M theory. I know at Fermi Lab scientists were looking for gravitons in distant places in our universe so that they can prove string theory. ...
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0answers
35 views

Does flat-land really exist?

In a paper "Out of the White Hole: A Holographic Origin for the Big Bang." The authors talk about the possibility that our 4D(3+1) universe could of emerged from a 5D(4+1) Schwarzschild black hole. ...
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2answers
130 views

String models of particle physics

What general features of particle physics are derived/replicated by constructing string models of particle models? How do such models address the fixing of free parameters like the masses and the ...
2
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0answers
62 views

Correlation function for ghosts in 2D CFT

In Di Fracenso, page 117, it is explained that the correlation function for two primary fields $\phi_1,\phi_2$ of weights $h_1,h_2$ is constrained to be of the form ...
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2answers
94 views

In a 2D CFT of a free boson $X$, is $X$ a primary field?

A primary field $\mathcal{O}(w,\bar{w})$ with weight $(h,\bar{h})$ is defined by having the following OPEs with the stress tensor: ...
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0answers
36 views

What is known about the physics of Planckbrane (another brane) in Randall–Sundrum model?

Randall–Sundrum model imagines that our universe is a five-dimensional anti-de Sitter space and the elementary particles except for the graviton are localized on a (3 + 1)-dimensional brane or branes. ...
2
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1answer
65 views

Action with self-dual field strength

It is said that writing down an action in presence of a self-dual field strength is subtle and not known till date. The familiar example people give is that of type IIB super-gravity which has a ...
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1answer
237 views

What is Kaku's equation about?

When Michio Kaku talks about science he often likes to refer to string theory and sometimes to his equation which looks like this (not sure if wrote right): $$L = \Phi^\dagger[i\partial_{\tau}-H]\Phi ...
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37 views

Hamiltonian for closed strings [closed]

I am reading GSW volume 1 and it says in chapter 2 that the Hamiltonian for closed strings turn out to be $$ H = \frac{1}{2} \sum_{n=-\infty}^{\infty} (\alpha_{-n}.\alpha_{n} + \tilde{\alpha}_{-n}\cot ...
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1answer
92 views

Doesn't string theory have to exist? [closed]

String theory is a theory of quantum gravity, and the standard model doesn't include gravity. But since there is gravity down at the sub atomic level, then doesn't string theory have to be right since ...
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1answer
80 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 ...
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1answer
45 views

What is a Schrödinger background or a Schrödinger symmetry?

In some string theory paper, they mention "Schrödinger background" and "Schrödinger symmetry", which I never heard before. What does that mean?
3
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1answer
48 views

Importance and Origin of level matching condition

I want to know the origin of level-matching condition of string theory. And want to know why many string theory textbook mention that this condition is crucial. Is this level matching condition ...
2
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1answer
67 views

Problems with covariant action of the superstring

I was reading Kiritsis notes (http://arxiv.org/abs/hep-th/9709062), at page 105/106 (equation 10.1), where he has a covariant action of the superstring including the gravitino. I have problems showing ...
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0answers
29 views

Kalb-Ramond in T-duality

I'm working through a particular problem (Problem 17.4) in Zweibach's "A first course in string theory", because I'm trying to understand how the Kalb-Ramond field affects T-duality. The question ...
3
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1answer
79 views

Semi-infinite forms?

I am reading Vafa's paper 'Topological Mirros and Quantum Strings'. In this paper, the author says the Hilbert Space of a fermionic string theory corresponds to the space of semi-infinite forms on the ...
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0answers
25 views

Generally speaking, given two CFTs, how can we check that they are equivalent?

We can calculate their central charges. And beyond this, are there some other general approaches? Or we must find an isomorphism of operators between the two theories?
3
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0answers
71 views

Does Type IIB string theory feature D(-1) and D9 branes?

I'm slightly confused as to how one deduces the D-brane content of a string theory by studying the p-form fields in the effective field theory. In type IIB supergravity one has: The Kalb-Ramond ...
3
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1answer
85 views

Beyond usual quantum mechanic description of entanglement, is there any QFT or stringy formalism/explanation of it? [closed]

Currently entanglement is speculated to be one underlying mechanism of emergent spacetime, but what are its foundations?
3
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1answer
104 views

What is meant by open-string tachyon scattering amplitude?

It was said here that Veneziano derived: open-string tachyon scattering amplitude from principles of Regge theory and S-matrix theory and used the Euler beta-function to make all the critical ...
3
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0answers
46 views

Tension of string-theory string

Can the tension of a given string in string theory be increased (by say interaction with other strings), or is it always fixed. I am trying to figure out if the energy of a string can be increased. ...
1
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0answers
29 views

What does black hole temperature mean? [duplicate]

From the title, the question is a bit open ended. Let me make it a bit simpler. 1. What region of the black hole has temperature? Is it the surface space? the region outside? . . . etc , any precise ...
0
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1answer
51 views

What happens when an open string start to stretch in a full Neumann boundary scenario?

I'm only reading about string theory. I'm an undergraduate. I see that for a full Neumann boundary condition the ends of a relativist string travel at the speed of light. If they travel in opposite ...
9
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2answers
235 views

Symmetry of the Polyakov action?

Let us look at the Polyakov action for a string moving in a spacetime with metric $g_{\mu \nu}(X)$:$$S_P = -{1\over{4\pi \alpha'}} \int d^2 \sigma \sqrt{-\gamma} \gamma^{ab} \partial_a X^\mu ...
2
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0answers
40 views

What are the difference between a black holes and a black branes? [closed]

I want to know the fundamental difference between a black hole and a black brane? What is the planar limit?
5
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0answers
329 views

750 GeV diphoton resonance: KK graviton?

As everybody of you may know at LHC they found this probable resonance (https://cds.cern.ch/record/2114808, https://cds.cern.ch/record/2114853?ln=en). It may be a scalar or a KK graviton mode. Now, ...
2
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1answer
41 views

Why are only certain fluxes allowed in 11D SUGRA?

In Type IIA/IIB string theory we can have various fluxes, such as the 3-form H-flux, and the various Ramond-Ramond fluxes in even/odd dimensions. In 11D SUGRA, however, the field content seems to ...
0
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1answer
91 views

Geometry of spacetime and spinor bilinears

In this paper (http://arxiv.org/abs/0704.0247) p.20, the author says in the section titled Geometry of spacetime the following: In order to obtain the spacetime geometry, we consider the spinor ...
5
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1answer
112 views

Orbifold actions and twist operators

A twist operator $\sigma$ is the operator that acts on the untwisted vacuum $|0\rangle$ to create a twisted vacuum $\sigma|0\rangle$. States belonging to the twisted sector of an orbifold are built on ...
5
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0answers
141 views

on fundamental 2D conductivity equation boundary value problem

Consider the following homogeneous boundary value problem for a function/potential $u(x,y)$ on the infinite strip $[-\infty,\infty]\times[0,\pi/4]$ w/positive periodic coefficient/nductivity ...
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0answers
51 views

Squashed spheres in general dimension

The point of this question is to help me find references regarding squashed spheres in general dimension. I am interested in the general theory of squashing for arbitrary dimension. All of the ...