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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Form of Dilaton term in polarization tensor

The vertex operator associated with massless state is $$V(k,\epsilon) = -\frac{2}{\alpha}\epsilon_{\mu\nu}(k)\bar{\partial}X^\mu(\bar{z})\partial X^\nu(z)e^{ik\cdot X(z,\bar{z})}$$ The polarization ...
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1answer
86 views

The quantum state of the Universe

As far as I know, the two popular attempts to quantize gravity (string theory and loop quantum gravity) rely on unmodified quantum mechanics. Since they aim to become ToEs, this also mean that the ...
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61 views

Quantum to String: making the transition

We have a Hamiltonian containing a quantum simple harmonic oscillator coupled to a meter and a force. There is a term in the Hamiltonian that involves the oscillator position and the force, a term ...
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74 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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1answer
93 views

Estimating volume of moduli space of genus-g Riemann surface with n marked points

I wanted to know how can I estimate the volume of the moduli space of a Riemann surface of genus $g$ and having $n$ marked points. I am reading some old string theory papers which discuss divergences ...
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42 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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2answers
249 views

Quantum Yang-Mills Theory and AdS/CFT

I just read the first chapter of Becker-Becker-Schwarz. To quote: A remarkable discovery made in the late 1990s is the exact equivalence (or duality) of conformally invariant quantum field ...
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2answers
90 views

World-sheet energy-momentum tensor and OPE

On p43 of Polchinski's book, it says that under the world-sheet translation $\sigma^a\rightarrow\sigma^a+\epsilon v^a$, $X^\mu\rightarrow X^\mu-\epsilon v^a\partial_a X^\mu$. And $$j^a=iv^b T_{ab},$$ ...
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1answer
107 views

Operator product expansion in CFT

I'm on Polchinski's p39. Can someone please tell me the steps in the equivalence below? $$\exp\left[\frac{\alpha'}4\int d^2z_4 d^2z_5\ln|z_5-z_4|^2\frac{\delta}{\delta X^\mu(z_4,\bar ...
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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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57 views

Cosmological constant (positive, dS) as SUSY/supertring issue

The "almost" de Sitter expansion of current cosmological model implies a puzzle for supersymmetry (SUSY) and also for string theory. A positive value of the cosmological constant implies a non-null ...
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1answer
114 views

Geodesic curvature and Weyl transformations

The geodesic curvature is given by $$k=\pm t^a n_b\nabla_a t^b,$$ where $t^a$ is a unit vector tangent to the boundary of the string worldsheet and $n_a$ is an outward vector orthogonal to $t^a$. I ...
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1answer
140 views

Why do people look for a field formalism for String Theory

String theory was originally formulated from a perturbative description (using quantum mechanics (QM) and replacing points by strings and evaluating path integral). Still, although QM has an upgrade ...
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1answer
48 views

String boundary conditions

I'm reading Polchinski and am confused about equation (1.3.13), $$\gamma_{\tau\sigma}\partial_\tau X^\mu-\gamma_{\tau\tau}\partial_\sigma X^\mu=0~~~~~\text{at}~~~~~\sigma=0,l.$$ It says that this ...
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1answer
51 views

Why does product of Moduli and Diff x Weyl Variation vanish?

According to equation 5.2.5 in Polchinski :- $$\int d^2 \sigma~ \delta^{'}g_{ab} \times [-2(P_1 \delta \sigma)_{ab} +(2\delta w - \Delta \cdot \delta \sigma)g^{ab}]=0$$ The assumption here is that " ...
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89 views

Polchinski equation 4.3.16

I am trying to obtain the polchinski's equation 4.3.16 which is following $ Q_B^2 = \frac{1}{2}\{ Q_B, Q_B \} = -\frac{1}{2}g^{K}_{IJ}g^{M}_{KL}c^Ic^Jc^L b_M =0$ Where $ Q_B = C^I(G_I^m ...
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2answers
62 views

Are string theories extra dimensions required to be “higher” than the four we know of? [closed]

Does the mathematics of string theory require extra dimensions to be "higher" than our own? Is it possible that extra dimensions are lower that that the four we currently know? Could our four be ...
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1answer
234 views

About solitons, what is the difference between kinks and vortices?

I am reading papers about solitons for my small reports, and i could not understand its physical meaning in detail. I know soliton is solitary wave which behaves like particle. And many text they ...
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31 views

diff-invariant, regulator, cutoff integral on string theory

The diff-invariant distance between $z'$ and $z$ is (for short distances) $e^{w(z)}|z'-z|$, so a diff-invaraint cutoff would be at $|z'-z|=\epsilon e^{-w(z)}$. Then $$ \int ...
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1answer
236 views

What comes after string theory/M-theory?

Classical mechanics is a good approximation to special relativity, which is a good approximation to general relativity etc. I have heard that if string theory/M-theory is right, then it is not just an ...
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1answer
92 views

Instantons as a -1 dimensional object

I don't know much about Instantons, and looking through the Wiki page it seems like one must have a lot of knowledge about QFT to understand them. However recently I've encountered a statement (which ...
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1answer
53 views

why is it important to find stability of supergravity solutions? [closed]

I want to know about the importance of the stability, generally,why is stability important in super-gravity? and why do we like these solutions?
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2answers
520 views

What experiment would prove string theory?

The conceptual model of multidimensional vibrating strings provides an incredibly rich and diverse "language" that almost certainly is encompassing all of known physics as a singular point somewhere ...
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83 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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4answers
2k views

Is our universe an emulation?

I was watching one of Neil Degrasse Tyson talks and there was a scientist (can't recall his name sorry) who was talking about a recent discovery: "Doubly-even self-dual linear binary ...
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213 views

What is the meaning of this String Theory Equation from CERN? [closed]

I have recently visited CERN, and in the Globe they showed an equation from string theory. My knowledge about it goes only as far as 'The elegant universe', so no mathematics, but i would say that ...
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1answer
50 views

Deriving conserved currents by promoting parameter

I currently reading Tong's text on String Theory. In Chapter 4.1.1 he alludes to a technique to derive conserved currents Recall that we can usually derive conserved currents by promoting the ...
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1answer
69 views

The equivalence of two worlds related by T-duality

T-duality in string theory relates a world containing open and closed strings with a D$p$-brane with a compact dimension with radius $R$ with a dual world with a D$(p-1)$-brane with a radius ...
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1answer
62 views

How can one calculate the central term of the conformal field theory algebra (and show it's really the virasoro algebra)?

So I'm following Szabo's book "An Introduction to String Theory and D-brane Dynamics (2nd ed, 2011); still on the canonical treatment in chapter 3. After doing a mode expansion, we get (up to a ...
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1answer
108 views

Infinite number of universes? Black holes are guilty? [closed]

I was thinking, if the space is infinite, what if there are infinite number of spaces, inside our universe? I mean, everyone knows that black holes exist, but nobody knows what happens when you get ...
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1answer
156 views

What are the implications for the AdS/Cft program if AdS is unstable?

To my understanding recent progress in the study of the non linear stability of AdS spacetime suggest that $AdS$ might be unstable. If this is true, what are the physical and mathematical ...
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50 views

“Dictionnary” between QFTs in D and D-1 dimensions?

Considering Einstein equations, suppose, for instance, that the RHS, the stress-energy tensor, is uniquely due to the electromagnetic field. Now, if we imagine a quantized version of these Einstein ...
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1answer
238 views

Can the compactified dimensions of M-Theory/String Theory become uncurled?

Is it possible for the curled dimensions described in superstring theories to become uncurled and open up. I have read that the big bang could have been the uncurling over 3 dimensions through ...
2
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1answer
52 views

relating spinor and fundamental representation for $E_8$

While proving a very important relation which is satisfied both by $SO(32)$ AND $E_8$, which makes it possible to factorize the anomaly into two parts. The relation is ...
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35 views

Stability of D-Branes and Coupling to Fields

I've been brushing up on my string theory using Becker, Becker, Schwarz (p. 208 in particular). They state that some D-branes can couple to R-R fields from closed string excitations. They then go on ...
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1answer
40 views

Long string model of black hole

I wonder if anyone can advise me literature about "long string model" of black hole. I've tried Google, and of course arXiv.org. Still I couldn't find anything about this theme. I would be also very ...
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22 views

Are O-planes not dynamical?

In Polchinski's book "String theory", he is saying "Unlike the case of D-branes, there are no string modes tied to the orientifold plane to represent fluctuations in its shape. Our heuristic argument ...
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50 views

Compactification and off-diagonal terms of the metric tensor

In standard 3+1 dimensional spacetime, the metric tensor is of order 4 and had ten independent coefficients, hence there are 6 terms off the diagonal in the corresponding $4\times 4$ real symmetric ...
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1answer
86 views

Traces in different representation

I am actually working with Green-Schwarz anomaly cancellation mechanism in which I have came across a strange formula which relates trace in the adjoint representation (Tr) to trace in fundamental ...
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96 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
140 views

I want to decompose a tensor product using Littlewood-Richardson rule, How do I find the component of this in each irreducible space?

Let me set up the notation I am using. $(abc,de)$ denotes the standard Young tableau where the first row is $abc$ and the second row is $de$. Each young tableau corresponds to the young symmetriser, ...
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1answer
66 views

About Shor's error correcting algorithm

In this paper, http://arxiv.org/abs/1301.4504 in equation 4.1 in what sense are the two states a "9-qubit state"? I did not understand this counting. Can someone explain what are the different $X_i$ ...
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1answer
63 views

Resonant Frequency & Opera Singers [closed]

Would it be possible under math of strings to note the frequency of each string vibrations? And in doing so, in hand with using the technique opera singers use to shatter glass with their voice, would ...
2
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0answers
46 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 ...
3
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0answers
85 views

Values of Spacetime Dimension and Virasoro Generator Ambiguity in Bosonic String Theory

I have already asked a similar question but I was suggested to split the questions so I do that now. In the book by Green, Schwarz and Witten spurious states are introduced to find values for the ...
3
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61 views

Structure of Hilbert Space in Bosonic String Theory

My question is about the canonical quantization of free bosonic string theory as described by Green, Schwarz & Witten. There they use spurious states to calculate a value for the ambiguity ...
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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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1answer
157 views

What does this question about entanglement and classical geometry mean?

Below is the question from Andy Strominger's presentation at the String 2014 conference. The question was asked by credible physicist Ashoke Sen as an important question. "What is the precise ...
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51 views

A question on the Bousso-Polchinski paper

In this famous paper by Bousso and Polchinski, Quantization of Four-form Fluxes and Dynamical Neutralization of the Cosmological Constant an example in M-theory compactification is given in section ...
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1answer
111 views

String Theory and Fourier Analysis [closed]

Me and my friend, both many years from learning string theory, had a recent debate about it anyway. He said he already partially discounts it because after learning waves, he believes any function, ...