String theory Definition and 782 Threads

How are fermions, like electrons, described by m theory? Are they closed strings like gravitons, or are they open strings attached to a D2/M2, D4, or M5 branes?

Can the 5brane turn into a fundamental string?

Hi fellow physicists, Suppose a spring with a stiffness k, is attached to wall and with the other side a block with a mass, m, a force F, then pulls the block away from the wall. How do you derive a function for acceleration of the block as a function of time, a(t)? When trying to solve this I...

I have been following along the problem on SO(32) st. in Zwiebach's "A first course in String theory" and my question concerns this problem. I have no problem with the mathematics of SO(32), at least not at the simple level Zwiebach discusses it, rather the "why" behind a particular concept of...

Can someone explain string theory? and how it works please? I am really interested thanks :D

Hello, Before starting, I would like to apologize for any errors in the use of symbols. This is my first time :sorry:. I am studying the wonderful book of Barton Zwiebach, "A First Course in StringTheory". In chapter 02, I am experiencing for the first time with the mathematics of special...

In one book of Susskind I found the following claim and I wanted to ask for its basis. Susskind says that each kind of boson gives positive contribution to the cosmological constant (the lighter, the better). Each kind of fermion gives negative contribution to the cosmological constant. Thus...

Can the M theory/ string theory coexist with the penrose interpretation of quantum mechanics?

Strings are said to be one dimensional, due to the math. And I understand that there are problems in the math when they put the strings in 3 or 2 dimensions. According to string theory, lengths smaller than Planck length have no physical significance. Could it be that strings are 3...

When they say strings are one dimensional, do they mean that the height and width are really small that its only the length that matters? And if not, how can a one dimensional object exist if it has no height or width?

Are strings really just one dimensional? Is it possible that strings are 3 dimensional? Or even 10 dimensional?

This question, at the moment, is ridiculously difficult or even impossible to answer. Some prefer string theory, and some think that it is overly speculative and LQG may be a better fit, and some say the opposite. I would like to ask; In your opinion, what could be the right theory of quantum...

String theory is what I'm currently studying. The dominant form is the action formulation of it. A classical string Lagrangian is submitted and quantized to produce the equations of motion of a string. Is there a purely quantum formulation of string theory that doesn't start with a classical...

I was recently watching a talk by Witten and he mentioned that one of the magical things about string theory is that it forces us to accept certain symmetries of nature, as opposed to choosing them as we do in QFT. Can anyone give an enlightening explanation of this? I do have very basic...

Is it allowed to travel to the past in ST?. I've always thought about paradoxes in the regular framework (4D space-time). What about ST framework?. I need a little guidance here. Thank you in advance, AGZ

Please hint me the order in time to read those String Theory books:Zwiebach,Polchinski,Hatfield,Kaku,Green-Schwarz-Witten,West,Johnson(D-Branes),David Tong(lecture on String Theory dampt).

Is there quantum foam between strings?

I was watching a sixty symbols video on Stephen Hawking: , and it got me thinking. Is there any practical value for theoretical physicists, if what they are doing is simply speculation not backed by any data? I understand observing a physical phenomena, and from understanding it predicting new...

Hi. 4 years ago my child asked to me a question... What will be happen, if the light is stop? I tried to answer it ... But my knowledge is insufficient. (I had been educated at social science, specially labor laws) . So I searched, tried to learn something new... So I liked physics. Of course it...

Layman question here: When discussing the difficulties in merging GR and Quantum theory, it is often mentioned that a main issue is that GR is continuous while quantum theory is discrete. A less commented point is the fact that GR is a deterministic theory while quantum theory is probabilistic...

This is a stupid question (good that I ask). String theory treats bosons and fermions in different ways e.g fermion potential are differ from boson potentials,actions differ and so on... My question is simply : why? Yes I know fermions and bosons are different groups of particles (integer and...

Hi, So in an informal sense, we hear about string theory requiring small, curled up dimensions locally at every point of spacetime. In my very, very limited knowledge of geometry, I would like to think of this as a fibre bundle structure over each point of Minkowski space. However, analogous...

As I understand it the proposed SUSY model is based on an "expectation of symmetry", which also happens to nicely solve specific problems with the SM. If the LHC does find evidence of SUSY structures - is string theory a candidate for a fundamental theory that would "explain the harmony" of the...

I'm not sure where to post this but it is technically homework but it doesn't follow the template and its less of a math question and more of a conceptual thing anyways. I have to write an English paper on a problem in a future career and it has to be big. I'm thinking about physics so I wanted...

What is the prerequisite to learn string theory ? I know Quantum Field Theory at the level of David McMahon, i don't konw General Relativity

I wasn't sure whether I should post this question in this category or "High Energy, Nuclear, Particle Physics", but I decided to post here, since I want to get opinions from the people who are studying the topics discussed in this category, not the experts on standard model or particle physics...

In his 2001 Three Roads to Quantum Gravity, on its p.l66, Smolin says, "M theory, if it exists, cannot describe a world in which space is continuous and one can pack an infinite amount of information into any volume, no matter how small." As a lay person, I'm hoping to get an informed opinion...

Are the general principles of string theory “the properties of fundamental particles are due to their unique vibrational pattern of strings in 10 or 11 or 26 dimensions” incompatible with both general and special relativity? due to an observer would be able to detect changes in properties of...

I've been tasked with giving a presentation on any subject i like to my undergraduate physics class. Inspired by a recent lecture i attended by David Tong i have chosen to do a quick (10 minute) overview of the current state of theories beyond the standard model, obviously aimed at being...

I read somewhere that the Monster Group appears is related to String Theory as 26D String theory on a 24D Leech Lattice gives a vertex algebra whose symmetries are the Monster Group. Just wondering if the size of a big group like that appears in the actual Universe? For example, there are lots...

Well, the string theory talks about multiverse, unlike the Big Bang theory. Michio Kaku explains it by comparing it with bubbles. There are many universes. These universes are like bubbles floating around, and when they collide, they form a single bubble- a universe. When a single bubble...

Hello everyone. I am an international student from China. Currently I received offers of a PhD position from both Caltech and Stanford. I applied for Hep-th and my main interests are formal field theories and string theory. I know both Caltech and Stanford are great schools in physics. And it...

Hi guys, To the experts of particle physics and of course to anyone else who knows and wants to share, what is the current status of string theory? Is there any progress? regress? are we stuck at a point (if so, I'd love to know which and why)? Thanks.

Hello, if you have ever heard of the TOE then you may be able to answer my question on this theory. The theory explains that there are tiny little strings in all atoms. Imagine the universe being an atom, the stings in this atom would be the size of a tree here on Earth. That is how small they...

If a function f'(u) has Fourier coefficients anμ and bnμ, by integration one can make new coefficients Anμ ,Bnμ which include constants of integration. My question how can I verify that : Anμcos nτ + Bnμ sin nτ= -i/2 ((Bnμ) -Anμi) einτ- (Bnμ-iAnμ) e-inτ I assume this is the complex form of...

Hi guys, So I'm a bit confused about why strings can't move at the speed of light. I understand that the end points do if the string is open, but the rest of it doesnt. To paraphrase, really I want to know why you must have timelike and spacelike tangent vectors to a point on the world sheet...

In string theory/M theory, there are two types of strings, open and closed strings. What kind of strings are fermions(electrons, quarks) made out of? Closed or open strings?

Dears, What do you think, hypothetically, Einstein should think about String Theory?. Obviously, if he was here to study it.

I'm a beginning graduate student in string theory and I'm in the process of teaching myself algebraic geometry. I'm using lecture notes that go without mention of physics. I'm curious if there is a introductory book, or paper, or set of lecture notes that describes the application of alg...

Hello guys. I am fortunate that I have found this website and I have created an account just to ask one question. I asked this on yahoo answers as well but no luck. So here goes. I'm 14 years old and I love astrophysics. I have learn most of the basic stuff and I've also read A brief history...

Hello folks, I want to starting learning the subject this Christmas (Merry Christmas :D) and I am wondering what would be the best way to introduce me to Strings. I am a masters student in Theoretical Physics. Best wishes, and many thanks in advance. Breo.

My question is rather simple: How can I derive the equation for the change in action "delta S" ? If S is the Nambu gotto action.Thanks for any clarifications.

Hello Everyone, I want to know if it's a good time to study string theory from the basics? Or is it wiser to wait till next year, after the 2015 LHC run, if indeed we find any evidence for it? I have done a course in mathematical physics, classical and quantum field theory, electrodynamics and...

Hi. I am no physicist but I am trying to know something about the holographic principle. As I understand, everything is happening in a surface and our three-dimensionality is an illusion of our senses. On the other side, string theory assume the existence of 11 dimensions. Are the two theories...

In string theory, the Neveu-Schwarz B-field appears in the action: S_{NS}=\frac{1}{4\pi\alpha^\prime}\int d^2\xi\;\epsilon^{\mu\nu}B_{ij}\partial_\mu X^i\partial_\nu X^j. In Polchinski's text, the antisymmetric tensor appears in the form of \frac{1}{4\pi\alpha^\prime}\int...

I'm beginning to apply to grad schools (primarily in observational or computational cosmology and extragalactic astronomy) but have a deep interest in M-theory and quantum gravity although I haven't been able to study it. I very much enjoy theory and think that I would find studying M-theory or...

Greetings, I am intending on learning bosonic string theory in self study before new years eve and I nead a ruff and short introduction on the basics and the idea of gauge theory. The introducton is preferably in PDF form, yet books are fine to.

Consider the feynman diagramms for two freely propagating particles...Correction from one graviton exchange. Correction from two graviton exchange.The problem at hand is the divergence (of the math) at arbitary energys and each additional graviton exchange. So there are several resoultions and...

I am looking for introductiory books on gauge theory and conformalfield theory and polyakov integrals for research in Bosonic string theory. Any other material recommendations for String theory that are necessary for bosonic string theory or heterotic string theory are definelty apreciated. To...

This will, no doubt, sound like a silly question but I am just getting my feet wet in string theory. It seems from what I know so far, that string theory is very far removed from our observable universe. What I mean by that statement is that it seems we just say "well, maybe our universe is a...