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12
votes
2answers
658 views

Why one-dimensional strings, but not higher-dimensional shells/membranes?

One way that I've seen to sort-of motivate string theory is to 'generalize' the relativistic point particle action, resulting in the Nambu-Goto action. However, once you see how to make this ...
8
votes
1answer
1k views

Electric charge in string theory

The mass of an elementary particle in string theory is related with the way the string vibrates. The more frantically a string vibrates the more energy it posses and hence the more massive it is. My ...
8
votes
1answer
83 views

Matrix geometry for F-strings

A stack of N D-branes has the strange property that the traverse D-brane coordinates are matrix-valued. When the matrices commute, they can be interpreted as ordinary coordinates for N ...
7
votes
1answer
131 views

The stability of D-Brane

In "String Theory and M-Theory: a modern introduction" by K.Becker, M. Becker and J.H.Schwarz, they say that BPS D-brane is stable as it preserves half of the Supersymmetry. I really want to ...
7
votes
1answer
114 views

Counting D0-D4 Bound States

I have a slightly technical combinatorics question. Consider the degeneracy $D_n$ of bound states of $n$ D0 branes and one D4 brane. This is given in Polchinski by (13.6.24), \begin{align} ...
7
votes
0answers
97 views

Is it possible to derive the brane action in pure supergravity?

The branes that source the RR fields of supergravity are described by the DBI action plus a CS term. I know this only from superstring considerations. Is there a way to find this result without ...
6
votes
1answer
165 views

Critical dimension in quantization of p-branes

So I have what might be a fairly basic question, but my understanding that in the quantization of the the string, or the 1-brane, there are conditions on the number of spacetime dimensions to ensure ...
6
votes
1answer
129 views

Disappearance of moduli for condensate of open strings

Consider a Dp-brane. Compactify $d$ spatial dimensions over a torus $T^d$. Suppose $d\geqslant p$, and that the Dp-brane is completely wrapped around the compactified dimensions. Look at the open ...
5
votes
1answer
246 views

M(atrix) theory and things other than D0-branes? And is it non-peturbative M-theory or non-peturbative Type IIA theory?

When I first read the BFSS Paper on M(atrix)-theory, I was under the impression that it was a non-peturbative formulation of M-theory. But recently, upon reading this paper of Nathan Seiberg's, I ...
5
votes
1answer
135 views

Why does unbroken supersymmetry imply the absence of tachyons?

Just a quick question, same as in the title. I'm trying to understand stable D-branes.
5
votes
1answer
93 views

A question about the coupling between string and gauge field $A_{\mu}$

I have a question about deriving the coupling term of string and the gauge field on brane. According to David Tong's lecture note p184/(191 in acrobat), the coupling is given by $$ ...
5
votes
0answers
44 views

Why does a string connected between a D0-brane and an anti-D0-brane turn into a tachyon upon their annihilation?

Consider a string stretched between a D0-brane and an anti-D0-brane. In this case as the stretching energy is greater than the quantum zero point energy the string will have a positive mass. But, as ...
4
votes
1answer
232 views

What does it mean to “wrap” a D-brane around some manifold?

I am getting quite confused with this terminology when I read the papers. Like while constructing the near horizon $AdS_3$ in the $D1-D5$ system one considers $IIB$ on $R^{1,4}\times M^4 \times S^1$ ...
4
votes
1answer
60 views

Solitonic nature of RR sources

In the famous paper by Polchinski where he shows that D-branes are sourcing RR fields, he says (before we known the result) that RR sources must be objects with tension going like $1/g_s$ (page two of ...
4
votes
1answer
151 views

Mass of a superstring between two branes?

A open bosonic string between two parallel branes seems to obey formulae such as $M^2 = \big((n + {\theta_i - \theta_j \over 2 \pi}) {R' \over \alpha'}\big)^2 + {N-1 \over \alpha'} $ So that the ...
4
votes
1answer
109 views

Negative open string norms after BRST cohomology?

The question Disappearance of moduli for condensate of open strings made me think. Suppose we have a Dp-brane completely wrapped over a $T^d$ compactification with $p\leqslant d$. Look at an open ...
3
votes
2answers
316 views

String theory: why not use $n$-dimensional blocks/objects/branes?

I have a basic question: if we use 1d string to replace 0d particle to gain insight of nature in string theory, and advanced to use 2d membranes, can we imagine that using $3$- or $n$-dimensional ...
3
votes
1answer
106 views

Even-branes in IIA and odd-branes in IIB

The R-R sector of IIA and IIB are respectively given as, $8_s \otimes 8_c = [1]\oplus [3] = 8_v \oplus 56_t$ $8_s \otimes 8_s = [0]\oplus [2] \oplus [4]_+ = 1 \oplus 28 \oplus 35_+$ Now looking at ...
3
votes
1answer
78 views

Must string models that describe 4d effective field theories always have D-branes that extend in the 4 non-compact spacetime dimensions?

In string theory the D-branes give those directions that the strings are allowed to move along. The string excitations give the fields that we detect. Is it correct to think of a particle propagating ...
3
votes
1answer
97 views

A question about T duality

Normally T-duality is introduced perturbatively by computing world-sheet spectrum of fundamental strings, and one of the conclusions is that it switches between momentum mode and winding mode of ...
3
votes
1answer
271 views

The theory of strings stretching between intersecting D-branes

I am trying to understand various aspects of intersecting D-branes in terms of the gauge theories on the worldvolume of the D-branes. One thing I'd like to understand is the worldvolume action for ...
3
votes
1answer
91 views

Can a D-brane be closed and contractible?

Let's consider for simplicity D-branes in bosonic string theory. I have a very basic question whose answer I couldn't find clearly stated in the few textbooks where I looked for it. Take for ...
3
votes
1answer
211 views

Neumann boundary condition and the open string

In string theory, If an open string obeys the Neumann boundary condition, then in the static gauge, one can show that the end points move at the speed of light. The derivation is straightforward, but ...
3
votes
0answers
47 views

Action for $p-p'$ strings (equation 13.5.21 in Polchinski's textbook)

This action reads $$S=-\frac{1}{4g_{D9}^2}\int d^{10}x F_{MN} F^{MN}-\frac{1}{4g_{D5}^2}\int d^{6}x F'_{MN} F'^{MN}- \int d^6 x \left[ D_{\mu} \chi^{\dagger} D^{\mu} \chi + ...
2
votes
3answers
443 views

Do extra-dimensional theories like ADD or Randall-Sundrum require string theory to be true?

What I mean is could it turn out that the world is not described by string theory / M-Theory, but that nevertheless some version of one of these extra-dimensional theories is true? I have no real ...
2
votes
1answer
100 views

Constraints on open strings absent at the perturbative level

Studying Disappearance of moduli for condensate of open strings and Negative open string norms after BRST cohomology? gave me a huge huge shock! Suppose we have N completely wrapped Dp-branes over a ...
2
votes
0answers
42 views

$D$-brane and 5th dimensions

While I was looking up the 5th dimension of the Randall-Sandram model, I have wondered whether Kaluza Klein theory can be applied to the $D$-brane or $p$-brane. Can the $D$-brane and $p$-brane ...
2
votes
0answers
38 views

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

Is brane world scenario in contrast in some way with inflation theory ?
2
votes
0answers
51 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} ...
2
votes
0answers
210 views

Tree level and loop level

I'm trying to read through a paper which explains the following about Universal Extra Dimensions (UED) vs ADD models: The new feature of the UED scenario compared to the brane world is that ...
1
vote
1answer
817 views

Branes Collision -> Big Bang

Imagine universe occurred when two parallel branes collided, Momentum of Branes converted to big bang kinetic energy after Collision. Thus, high-energy quanta are high-Vibrating strings. what ...
1
vote
1answer
35 views

If QFT is a sum over 1-D topologies and String Theory over 2-D topologies, what is the corresponding theory for N-D topologies?

My understanding is that perturbative QFT can essentially be described as a weighted sum over 1-D topologies (ie Feynman graphs), and String theory is essentially the generalization to a sum over 2-D ...
1
vote
1answer
67 views

Are branes in 4D-spacetime moving, or are they static?

Given that a worldline, worldsheet, worldvolume, are representation in a 4D-spacetime of a point particle, a string or a brane, respectively, I was wondering if those objects necessarily have to be ...
1
vote
0answers
197 views

What happens to the amplituhedron in a non-peturbative context?

The Amplituhedron has recently been popular; it supposedly encodes perturbative scattering amplitudes in a simple, geometric fashion. What happens to it in a non-perturbative context? Is there ...
1
vote
0answers
85 views

Orientifold Plane, Anti-Dp Brane and SUSY breaking

In "String Theory and M-Theory" by K. Becker, M. Becker and J.H. Schwarz, page 222, they give a brief introduction about the (space-filling) Orientifold Plane $O9$ as an object needs to be add in the ...
0
votes
1answer
205 views

Does string/M-theory address higher-dimensional membrane vibration modes?

A loop is a 1-sphere that can vibrate in increasingly complex ways as it is embedded in higher dimensional spaces. Does string theory assume that 1-spheres are the only possible vibrating ...
0
votes
0answers
21 views

Within the context of string theory, is matter nothing more than a vibration on a membrane of space-time? [duplicate]

I've been reading about string theory, and as I understand it, it proposes that matter is nothing more than a vibration of a membrane of space-time. Is my understanding correct?
-1
votes
1answer
47 views

branes-collision -> big-bang -> 2nd Universe?

If the cosmological model of the Ekpyrotic universe is correct should there not always a 2nd universe be created on the 2nd brane? Pictures and articles I found speak only of one universe. Why is ...