String theory Definition and 831 Threads

In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings. String theory describes how these strings propagate through space and interact with each other. On distance scales larger than the string scale, a string looks just like an ordinary particle, with its mass, charge, and other properties determined by the vibrational state of the string. In string theory, one of the many vibrational states of the string corresponds to the graviton, a quantum mechanical particle that carries gravitational force. Thus string theory is a theory of quantum gravity.
String theory is a broad and varied subject that attempts to address a number of deep questions of fundamental physics. String theory has contributed a number of advances to mathematical physics, which have been applied to a variety of problems in black hole physics, early universe cosmology, nuclear physics, and condensed matter physics, and it has stimulated a number of major developments in pure mathematics. Because string theory potentially provides a unified description of gravity and particle physics, it is a candidate for a theory of everything, a self-contained mathematical model that describes all fundamental forces and forms of matter. Despite much work on these problems, it is not known to what extent string theory describes the real world or how much freedom the theory allows in the choice of its details.
String theory was first studied in the late 1960s as a theory of the strong nuclear force, before being abandoned in favor of quantum chromodynamics. Subsequently, it was realized that the very properties that made string theory unsuitable as a theory of nuclear physics made it a promising candidate for a quantum theory of gravity. The earliest version of string theory, bosonic string theory, incorporated only the class of particles known as bosons. It later developed into superstring theory, which posits a connection called supersymmetry between bosons and the class of particles called fermions. Five consistent versions of superstring theory were developed before it was conjectured in the mid-1990s that they were all different limiting cases of a single theory in 11 dimensions known as M-theory. In late 1997, theorists discovered an important relationship called the AdS/CFT correspondence, which relates string theory to another type of physical theory called a quantum field theory.
One of the challenges of string theory is that the full theory does not have a satisfactory definition in all circumstances. Another issue is that the theory is thought to describe an enormous landscape of possible universes, which has complicated efforts to develop theories of particle physics based on string theory. These issues have led some in the community to criticize these approaches to physics, and to question the value of continued research on string theory unification.

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  1. S

    A What does this article mean? (The holographic principle and M-cosmology)

    I was reading an article about holographic principle and M-cosmology and how could they be used to interpret QM mechanics. But there's a part where it talks about holographic principle in a strange way to me. What does this article mean with this?: "Since for the participant observer the...
  2. CessnaTexan

    I Definition of "info" as it pertains to string theory

    Hello, everyone! I am a lover of physics, specifically that of the quantum type. The very specific question I have is the exact scientific definition of "information" pertaining to string theory. Any insight is good insight!
  3. S

    A Information encoding in the Holographic principle

    Can whatever type of information be encoded in a boundary in holographic principle? in a question some years ago regarding holography (https://physics.stackexchange.com/questions/75436/are-stokes-theorem-and-gausss-theorem-examples-of-the-holographic-principle) It is said that AdS/CFT is the...
  4. R

    Explain string theory -- I'm interested in interpritations

    Hello all! I am trying to get a more reliable definition, plus, any opinions you might offer would be greatly appreciated!
  5. VIctor Medvil

    A I want to know the exact problems of Merging GR and QM

    This thread is I want a set of experts in the subject to show me the exact math of why Einstein's field Equations along with Special Relativity and Schrodinger's Equation along with deeper QM like QFT cannot be fused with GR. I want to see the exact anomalies in the equations myself from the...
  6. Spinnor

    I Can String Theory Explain the Energy Density of Empty Space?

    So if string theory is to be correct it must be able to come up with the observed value for the energy density of empty space which is pretty close to zero? A naive understanding of the compact spaces of string theory tells me that an "energy audit" of the highly curved compact manifolds of...
  7. S

    A Can a 3d holographic universe exist in 3d?

    In a holographic universe model, could our 3D universe be encoded in 3D and still be a holographic universe, instead of 3D information encoded in 2D space? Or is the standard model (non-holographic) of the universe already 3d information encoded into 3d space...
  8. I

    Schools String theory school recommendation: UC Davis, UIUC or other

    I'm currently applying for grad schools in string theory with an interest in AdS/CFT but am open to fundamental formalisms in string theory. I was trying to decide on a few universities to apply to. I am currently considering University of California Davis and University of Illinois Urbana...
  9. Spinnor

    B String theory, Calabi–Yau manifolds, complex dimensions

    So in string theory at each point of Minkowski spacetime we might have a 3 dimensional compact complex Calabi–Yau manifold? We can have curved compact spaces without complex numbers I assume, what is interesting or special about complex compact spaces? Thanks!
  10. B

    Exploring String Theory: Recommended Books and Critiques

    What are the books that speak about string theory you would suggest me? And the book against this theory? (I'm an undergraduate physics student) Thanks!
  11. binbagsss

    Polyakov action, reparameterisation q, string theory

    Homework Statement i am stuck on part d , see below Homework Equations parts a to c are fine polyakov action: ## \frac{1}{2} \int \frac{1}{e(t)} \frac{dX^u}{dt}\frac{dX_u}{dt}-m^2 e(t) dt ## EoM of ##e(t)##: ##\frac{-1}{(e(t))^2} \frac{dX^u}{dt}\frac{dX_u}{dt}-m^2=0## [1]you plug the EoM...
  12. K

    A Are String Theory physicists violating the Scientific Method

    The Scientific Method says that if a theory disagrees with observations, it has been falsified (according to Karl Popper). String theory predicts that spacetime is 10-D, but it is observed to be 4-D. This is a wrong prediction by the theory. So string theory is falsified. String theorists then...
  13. A

    A String Vacua and Particle Interactions

    I've been doing a little bit of reading on string theory, and the very large number of string vacua that are possible (i.e., perhaps 10^500 or more). One thing that is not clear to me is exactly what constitutes a 'vacuum' in string theory. In QFT theory, the vacuum is defined as the state with...
  14. K

    I String theory on complex spacetime, twistor string

    bosonic string theory requires 26 dimensions superstring theory requires 10, 9 spatial 1 dimension of time Witten has researched twistor string theory has there been any serious research with (super) string theory written on 4 complex -valued dimensions of spacetime? the additional dimensions...
  15. binbagsss

    String Theory, Number Operator , Mass of States

    Homework Statement I have the following definition of the space-time coordinates Homework Equations Working in a certain gauge we can also do: From which we can find: Where ##N_{lc} ## sums over the transverse oscillation modes only. The Attempt at a Solution [/B] MY QUESTION: I...
  16. J

    I Are Dimensions Real? | Questioning Space Dimensions

    I wonder if dimensions of space are real things, or just a way that humans describe space, rather like 'good' and 'evil' are just ways that humans describe behaviour, but good and evil are not themselves real. So just as good and evil are not real, perhaps dimensions are not real, and space...
  17. Spinnor

    B Branes, gluons, time reversal, and string theory.

    So a gluon in string theory may be an open string whose ends live on one or two branes? These strings have an orientation along the string? Does the orientation change direction if we reverse time, some where I thought I read that one can think of a flow along the string so if you reverse...
  18. B

    Studying Is Studying String Theory Worthwhile for a Future in Theoretical Physics?

    Hello, I am studing theoretical physics and i would like to focus my work in string theory, but my fellows say that is a waste of time. ¿Do you think that is worthwhile to spend my time and effort un string theory? Greetings
  19. Spinnor

    I Electric and Color charge in String Theory

    I get a gist of how electric charge comes about in string theory here, https://physics.stackexchange.com/questions/5665/electric-charge-in-string-theory How much needs to be amended to the above answer to understand how color charge comes about in string theory? I assume there are interesting...
  20. marce

    I Can Muons or Tau Particles Be Explained by Kaluza-Klein Towers?

    - Does anyone know , why for instance a muon or a tau , can't be considered as Kaluza-Klein tower(s) ? M.
  21. tom.stoer

    A String Theory and Einstein-Cartan Gravity

    I know two essential points where General Relativity plays a central role in String Theory: i) definition of the theory using a target spacetime with some Riemannian background metric in the Polyakov action and ii) recovery of the Einstein field equations as conditions regarding conformal...
  22. ohwilleke

    I Is this thesis a plausible explanation for muon weirdness?

    Background and Motivation In the Standard Model, a muon is simply an electron with a bigger mass. But, measurements of the radius of muonic hydrogen and the muon magnetic dipole moment (muon g-2), show a fairly significant discrepancy between theory an experiment in that respect, at the five...
  23. J

    Quantum What are your thoughts on Manoukian's QFT textbooks?

    Hello! Manoukian's two books on Quantum Field Theory seem pretty good to me, but before buying them I would like to know your thoughts about them! Bear in mind that I need a pedagogical textbook(with good exercises if possible). Thanks!
  24. S

    A Symmetry/Conservation Violated in Quantum Anomaly

    String theorists have apparently applied String Theory to expose a Quantum Anomaly in a physical analog system: electrons flowing in a Niobium Phosphide crystal. The electrons were found to violate symmetry in relation to Spin...
  25. Urs Schreiber

    Insights Super p-Brane Theory Emerging from Super Homotopy Theory - Comments

    Urs Schreiber submitted a new PF Insights post Super p-Brane Theory Emerging from Super Homotopy Theory Continue reading the Original PF Insights Post.
  26. Mary curie

    Want to learn about string theory

    Hello ! I have just graduated from high school but I have a big interest in the strings theory. I am trying to understand its roots aka from where/ how did it come! To that I Need some references for my research, references to make me understand the bases only ! Thank you!
  27. F

    A Do you think this year's string conference solved anything

    I just found out about the lectures, are there any interesting or profound ones. https://www.youtube.com/channel/UCFeW8O-DWElfT436yuivT6g/videos
  28. J

    Cosmology Book on Black Holes, Strings, AdS/CFT

    Hello, I would really like a book like Susskind's "An Introduction To Black Holes, Information And The String Theory Revolution: The Holographic Universe" but not so condensed. If you have anything to suggest please do so. Also, if you know of any book that contains any part of the above book in...
  29. binbagsss

    String theory reparameterisation/ transformation law metric

    Homework Statement Attached Homework EquationsThe Attempt at a Solution [/B] where ##\tau## and ##\sigma## are world-sheet parameters. where ##h_{ab}## is the world-sheet metric. To be honest, I am trying to do analogous to general relativity transformations, since this is new to me, so in...
  30. J

    High Energy AdS/CFT book that includes prerequisites

    Hello! Is there any book on Gauge/Gravity duality(or AdS/CFT correspondence) that includes a pedagogical and detailed overview on its prerequisites? Thanks in advance!
  31. A

    I String theory and Lorentz invariance - 10D vs. 4D....

    Hi all, Clarification question: I've read that string theory is manifestly Lorentz invariant - however, I'm confused about this being true in 4D spacetime or in the full 10D setting of the theory (well, one version anyway). At some point I'd also read in a paper that 4D Lorentz invariance...
  32. A

    A Einstein manifolds as asymptotic background spacetimes in Type IIB string theory

    On page 30 of the notes (https://arxiv.org/abs/1501.00007) by Veronika Hubeny on The AdS/CFT correspondence, we find the following: So far, we have been describing just one particular case of the AdS/CFT duality, namely (3.3). There are however many ways in which the correspondence can be...
  33. AuntyMatter

    I Black holes and extra dimensions

    We often hear about string theory requiring extra dimensions over and above our 4D spacetime. Does this shed any light on the singularity which is supposed to exist at the centre of a black hole? Does our normal spacetime simply join the other dimensions in their hidden (curled-up) form? This...
  34. C

    A Best way to learn string theory?

    I am a cosmologist/theoretical astrophysicist, and so far my research (all 2 years of it) has focused on quantum cosmology. However, I have become interested in string cosmology recently, and wish to do some work in that field. Obviously though, there is a minor problem with that idea. Learning...
  35. M

    B How does string theory fit with QFT?

    In string theory, particles is vibrating strings. However, QFT treats particles as excitations in a quantum field. Can both of these theories be correct? If so, how does them fit together?
  36. binbagsss

    A String theory - no-ghost state - virasoro constraints

    1. Homework Statement Question (with the following definitions here): - Consider ##L_0|x>=0## to show that ##m^2=\frac{1}{\alpha'}## - Consider ##L_1|x>=0 ## to conclude that ## 1+A-2B=0## - where ##d## is the dimension of the space ##d=\eta^{uv}\eta_{uv}## For the L1 operator I am able...
  37. binbagsss

    Strings, Virasoro Operators&constraints, commutator algrebra

    Homework Statement [/B] Question: (With the following definitions here: ) - Consider ##L_0|x>=0## to show that ##m^2=\frac{1}{\alpha'}## - Consider ##L_1|x>=0 ## to conclude that ## 1+A-2B=0## - where ##d## is the dimension of the space ##d=\eta^{uv}\eta_{uv}## For the L1 operator I am...
  38. Gjmdp

    I Why bother with Astrophysics if we have String Theory?

    If there is a "theory of everything", a single equation that basically explains everything, why should be study Astrophysics, Condensed matter, or so? I mean we should rather study String Theory, Quantum Gravity... So, am I wrong? Maybe I'm leaving some important details.
  39. craigi

    A Introductory String Theory Texts

    I'm looking for a recommendation for an up to date, introductory String Theory text and an overview of the prerequisites. Thanks in advance.
  40. K

    I Eletrons muons tau in string theory

    in string theory, where strings are posited as fundamental entities, what is the relation between eletrons muons tau how does string theory explain the increasing masses of leptons how do these leptons other properties come about in string theory what about the antiparticles of each? i.e...
  41. arivero

    A Does String Theory incorporate Kaluza Klein? How?

    From time to time, I point to string theoretists that they should have considered more seriously to use Kaluza-Klein theory and they invariably answer me "we do", and move forward. So I am starting to thing that perhaps I am wrong and I have missed some developing of the theory the the XXIth...
  42. P

    A String theory and zeta function z(-1)

    Over the last couple of years there has been allot of traffic on youtube about the sum of all positive integers being equal to -1/12 as is explained in numberphile video. Some argue that their calculations are wrong and the sum really is infinity. In their original video numberphile shows a...
  43. K

    I Why String Theory Is Still Not Even Wrong

    Horgan: Do you still think string theory is “not even wrong”? Woit: Yes. My book on the subject was written in 2003-4 and I think that its point of view about string theory has been vindicated by what has happened since then. Experimental results from the Large Hadron Collider show no evidence...
  44. I

    B What exists between Strings in String Theory?

    Hello, I am new to this. As I understand it, the difference between the quantum field theory and string theory is that in the former, physical field is considered as the fundamental reality, while in the latter it is believed that everything comes out of strings. My question is, by everything do...
  45. S

    I Energy conservation in String Theory

    Hello! I read some stuff about "attempts" to test some aspects of string theory at LHC and I was wondering if there is any deep reason behind the conservation of energy in general or it is just based on the fact that it holds in all the experiments (excluding uncertainty principle arguments)...
  46. Spinnor

    B Photon, string theory string, E&M field

    Is it possible to associate electric and magnetic fields with the vibrating string that is thought to represent a photon in string theory? Thanks!
  47. binbagsss

    A Intro to String Theory: Lightcone Gauge & Oscillators

    Lightcone gauge is ##X^u=\tau=1/\sqrt{2}(X^0+X^{D-1})## (1) The mode expansions are: My book says 'it is possible to solve for one of the oscillators in terms of all the others' with this relation. What is a oscillator? Is this any of the ##X^{D}## coordinates, what exactly does ##n##...
  48. Viet Tu

    B What is status of String Theory now?

    Are there anything new in String theory?
  49. N

    I Non linear interpretations of QM and string theory?

    Are interpretations that are non linear with respect to the wave function (eg. GRW, transactional) compatible with string theory?
  50. BiGyElLoWhAt

    I Why Plot Spin vs Mass^2 in Particle Physics?

    Maybe this is more quantum, but I'm not sure. I was watching Susskinds first String lecture on youtube, and he was talking about how, within each particle family, you get a straight line called a regge trajectory if you plot spin vs. mass^2. He also mentioned that there was some slight insight...
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