# What is M theory: Definition and 34 Discussions

M-theory is a theory in physics that unifies all consistent versions of superstring theory. Edward Witten first conjectured the existence of such a theory at a string-theory conference at the University of Southern California in the spring of 1995. Witten's announcement initiated a flurry of research activity known as the second superstring revolution.
Prior to Witten's announcement, string theorists had identified five versions of superstring theory. Although these theories appeared, at first, to be very different, work by many physicists showed that the theories were related in intricate and nontrivial ways. Physicists found that apparently distinct theories could be unified by mathematical transformations called S-duality and T-duality. Witten's conjecture was based in part on the existence of these dualities and in part on the relationship of the string theories to a field theory called eleven-dimensional supergravity.
Although a complete formulation of M-theory is not known, such a formulation should describe two- and five-dimensional objects called branes and should be approximated by eleven-dimensional supergravity at low energies. Modern attempts to formulate M-theory are typically based on matrix theory or the AdS/CFT correspondence.
According to Witten, M should stand for "magic", "mystery" or "membrane" according to taste, and the true meaning of the title should be decided when a more fundamental formulation of the theory is known.Investigations of the mathematical structure of M-theory have spawned important theoretical results in physics and mathematics. More speculatively, M-theory may provide a framework for developing a unified theory of all of the fundamental forces of nature. Attempts to connect M-theory to experiment typically focus on compactifying its extra dimensions to construct candidate models of the four-dimensional world, although so far none has been verified to give rise to physics as observed in high-energy physics experiments.

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1. ### A Basic Scheme and Fundamental Equations of String Theory

In Classical Mechanics you solve for a particle’s position through F=ma or the Lagrangian and Hamiltonian Methods. Quantum Mechanics you solve for the wavefunction or density matrix either the Schrodinger or Von Neumann Equations respectively or use Operator and Path Integral Methods...
2. ### Are there any resources for artists interested in theoretical physics?

TL;DR Summary: I would like to be involved in the physics community. Hello, my name is Joshua, I am a multidisciplinary artist and i have a big interest in engaging in conversations about theoretical physics to get a better understanding and also to apply into my art. My experience is pretty...
3. ### A M theory dimension change and large N_c, are they related?

Reading old text about the limit of large N_c, there are some remarks telling that for finite N we have a colour tube and that it becomes a string in the limit. It sounds as the extra dimension of M-Theory, and I wonder if the math of both calculations are related somehow. Is the transition to...
4. ### I The energy released from antimatter annihilation -- New uses?

The pure energy released from antimatter annihilation can there be any use of this clean energy for research purposes like the use of light in LIGWO for gravitational waves study can we use it efficiently like light in LIGWO I think we can and it could lead us to reveal mysteries of universe
5. ### B M Theory: What's the Consensus?

If question isint allowed please delete and let me know. I'm just wondering what the general consensus is about M theory?
6. ### B M theory, holography, many worlds -- What we do know?

Hi! Sorry for my bad English! I don't know much of physics, I know some experiments that show that relativity is real, quantum entanglement, particle and wave duality and so on... So, the only theory that explain all of it mathematically is M theory and the strings, but we can never test it to...
7. ### Standard model says 17 particals, M theory says 18?

Hi. I've only just started reading on M-theory. I'm otherwise a lay person so I'm going to have some basic questions. Here's my first. Standard Model has 17 elementary particles right? But doesn't M-theory say there's 18? Or 36 if you include the symetrical ones. So am I missing one particle...
8. ### How does M theory describe fermions?

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?
9. ### M Theory -- can a fundamental open string end on an M5 brane?

In M Theory, can an elementary open 1d string attach its ends on an M5 brane? According to M theory, the elementary string are created when an M2 brane is wrapped tightly around a circular dimension. When the open string is created can its end point attach on an M5 brane??
10. ### Can the 5 brane of M theory turn into a 1 string?

Can the 5brane turn into a fundamental string?
11. ### Can string theory and Penrose interpretation coexist?

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

### Why is it necessary to have 11 dimensions in M Theory?

I do apologize if this is the wrong place to post this. Why is it necessary to have 11 dimensions in M Theory? I've been at it for days emailing universities, Twitter, etc. No one has attempted to give me an answer and it's frustrating me. I just want to know what the purpose of each of the...
13. ### String theory and the M theory?

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?
14. ### Compactification of M Theory on Smooth G2 Manifolds

I am currently reading the paper given here by Acharya+Gukov titled "M Theory and Singularities of Exceptional Holonomy Manifolds", and in particular right now am following section 4 where the field content of the effective 4-dimensional theory is derived by harmonic decomposition of the 11D...
15. ### M Theory Formulations: Math & Competing Theories

Which is the current mathematical formulation of M theory, and what are its competitors?
16. ### A coherent survey of the problems in LQG and M theory.

Is there any survey article that accounts for all the problems that are as of yet to be solved in M theory and LQG? I mean if I'll have time to dive into this field once. (I don't have a girlfriend and I don't plan to, so maths and physics will do). :biggrin:
17. ### Opinions or facts about M theory

Hi, so I just wanted some opinions on string theory, superstring theory, or M theory. Any of them would be fine probably, but M theory is the one I'm really curious about (since it's the latest and greatest, according to some of the books I've read). So the only opinions on M theory that I've...
18. ### The logic of the 11 dimensions in M theory

According to M-theory as I understand, the 7 additional spatial dimensions to our familiar 3 are curled up all around us but they are too small for us to see. However I have difficulty in understanding how this constitutes a "dimension" because dimensions allow additional degrees of freedom...
19. ### Papers to prove and disprove string theory/ M Theory?

Hello, My name is Holly... I'm new here... so i have no idea weather I put this in the right section! D: ... Sorry if so :3 Basically, I have been put to the task of writing a paper on String Theory and weather or weather not String Theory/ M-Theory (i can do either one, will do the...
20. ### M Theory & Quantum Mechanics vs. SETI

Watched an episode of Brian Greenes NOVA "The Fabric of the Universe" for the 300th time and an episode of "The Universe" about M Theory and Parallel Universes. A thought/question popped into my head based on my uneducated understanding of these concepts (I was an Econ Major). * Quantum...
21. ### What are the 26 dimensions in the M theory?

What are all the 26 dimensions in the M theory, named?
22. ### Exploring the Latest Developments and Topics in M Theory: A Comprehensive Guide

does anyone know what are the most recent developments and breakthroughs on m theory...i don't seem to find anything big since holographic principle few years ago. if there haven't been any big breakthroughs than what are the topics that are being studied right now? does anyone know any...
23. ### Progress on M Theory: What We Know So Far

I am interested in what progress has been made understanding what M Theory is, what it's nature might be beyond dualities between partial theories, and any ideas about what types of phenomenon it might predict, beyond the partial theories. I would rather any discussions of plausibitlity of M...
24. ### M Theory: Exploring Gravity's Necessity in the Standard Model

How does M theory force gravity as a necessity when the standard model couldn't fit in gravity?
25. ### String/ M theory and Dark Matter

Hello, I am currently doing a research project on alternative theories to dark matter. I have covered all the main candidates fairly well such as nonsymmetrical gravity, conformal gravity and MOND etc. But I would really like to include a section on how string theory or M theory could explain...
26. ### Exploring the Theory of Cords and Lagrangian M Theory

Hi, well after several readings I believe it that the theory of the cords does not give in its approximations the standard model is it by what one does not know Lagrangian M theory ...
27. ### Understanding M Theory's 11 Dimensions

I've been reading into String Theory and M Theory lately and I think I have a general picture of what it's about, with the infinite parallel universes and whatnot. But this theory is built on the idea of 11 dimensions. I don't understand this.. how is it possible to imagine the 5th+ dimension...
28. ### Calabi Yau compactification and M theory

Ok, I really know nothing about this subject. Yeah, I know the definition, a Kahler manifold with a vanishing first chern class and a su(n) holonomy. I do think it's a cool mathematical concept that you could compact non-compact dimensions and in doing such you can generate the coupling...
29. ### Exploring the Role of Calabi-Yau Spaces in M-Theory and String Theory

Hello, Physicists have formulated a "Calabi-Yau space", to show the supplementary dimensions in the string theory. But this space have six dimensions, and the M theory, the presentest string theory, have seven supplementary dimensions... So, what is this Calabi-Yau space in the string...
30. ### Bosonic action in M Theory -> IIA Theory

In various textbooks like Polchinski and in papers like Witten hep-th/9503124 they go through the process of starting with the bosonic action (in p-form notation) of M Theory and turning it into the action for IIA string theory. I understand the process (ie dimensional reduction) which...
31. ### M Theory Questions: Exploring Big Bang & Membrane Impact

Ok I am very new to all of this, so my understanding is somewhat basic. The way I understand it is that m theory supposedly explains the big bang as a point in time where 2 membranes collided and the energy caused was the start of the universe. These membranes aren't flat but rippled, so they...
32. K

### What is M Theory? Understanding the Basics of this Fascinating Concept

i overheard someone talking about something called the M theory. They mentioned the string theory too (which i know about), but I have no idea what M theory is. Can someone please inform me?
33. P

### Exploring M Theory: A Comprehensive Guide to Reliable Sources

Can anybody point me to reputable and thorough sources for research into M Theory?
34. ### F Theory & M Theory: Exploring the Connection Between Two Theories

what is the relation between the two theories (if there is a connection between them)? thaks in advance.