String theory Definition and 782 Threads

In covariant quantization of the string, say as in David Tong's http://arxiv.org/abs/0908.0333 (p28), time is an operator. Is the time operator Hermitian, and does it correspond to an observable?

Right, Hello, I am new to this, and do not have much understanding, but can someone here help explain the Dimension Models and String theory to me?

LQG, strink theory and Penrose's spinor theory, or maybe it's twistor theory, I don't know, all I know is that all three theories achieve mathematical miracles in their attempts to go beyond the Standard Model - how can all three theories do this but be mutually exclusive at the same time. Or...

Hi everyone, I've always wondered what's that fuss for unifying general relativity and quantum mechanics all about. I stumbled upon things like string theory(or M theory) and even loop quantum gravity( which I think is as good as string theory despite rumors). My...

"Foundations of physics" Special Issue: Forty Years of String Theory http://www.springer.com/physics/history+&+philosophical+foundations+of+physics/journal/10701 If this has already been mentioned feel free to delete this post. Articles free through march, A Critical Look at Strings (Carlo...

I have been following Dr. Michio Kaku and his ideas on string theory. My question is, with the addition of other dimensions, what types of experiments and/or results could possibly provide evidence that this theory is correct. If we currently can't perceive these "discrete" dimensions, what...

From whst I have read, anything smaller than Plancks length, you need to account for quantum gravity.. also, it is assumed strings in string theory are Plancks length.. so how could anything be smaller than Plancks length if strings are Plancks length(or greater than)? I thought strings made...

Background-independence is the requirement that the theory be formulated based only on a bare differentiable manifold but not on any prior geometry. General relativity is the first example of such a theory. This is a radical shift as all theories before General relativity had part of their...

hello, I find both quantum mechanics and string theory to be a bit iffy. Mabey it's just because I don't understand it but I think the best way to understand the iffy stuff is to post it on here. Mentors might see this as a debate or going against mainstream physics but how are you able to make...

Can Someone Explain What String Theory Is? (Simple Terms With Examples) Ive been hearing a lot of references to this new string theory, what is it?

There was a thread about how to describe the proton in string theory that was deleted while I was writing an answer, so I will post my answer here in a new thread. How the proton, and processes inside the proton, are described in string theory, is an open research question, part of the area...

Hey guys, who can tell me briefly about the 10+1 dimensions in the string theory? I am going to deliver a short presentation on string theory ,but i am not very clear about the reason that we have to introduce 11dimendion to string theory ...

I just recently seen an article that the recent findings at the LHC seem to disprove supersymmetry. I would like to know how supersymmetry and string theory are connected and what the implications would be if the LHC totally disproves supersymmetry all together?

Just about few hours ago,my friend and i argued about which theory is the best theory nowadays ever existed. I claim that string theory is the only game in town as what i heard from Dr. Michio Kaku's TV shows, while my friend strongly disagree with it. He claimed that quantum theory is the best...

Consider me physics illiterate since my last class was advanced placement physics in high school (over 20 years ago). I am trying to understand what the title says, How does quantum entanglement, string theory, and the BB fit together? Skipping to the meat of the subject, everything revolves...

I was watching a video on string theory and they claim that its all vibrating strands of energy. I thought energy was just a property of the system, not a physical entity. So do they mean something else by "energy"?

I understand that suitable compactified strings in AdS correspond to conformal field theories (w/o gravity) living on the boundary space. What I do not get is the exact relationship between non-perturbative gravitational phenomena in the bulk and the CFT. All what I have seen are...

Could someone give me a short summary(if possible) of how discovering matter is made of vibrating energy will give explanation to all four fundamental forces?

I mean we really don't know what they are, right? We just know they can be positive or negative, north or south, but we really don't know why they exist. Will string theory give a definite answer to this? And also gravity. Will it confirm Einsteins theories?

Can anyone explain to me what is string theory mathematically?

It's really difficult as a layman trying to find out who is right and wrong in this debate as far as string theory. I find it kind of hard to believe that string theory is just simply completely wrong and has no relevance whatsoever to reality. After all so many theorists and so many papers...

Hi. I am fairly new to physics. I have recently read the first half of a book by Michio Kaku called “Beyond Einstein”, and I am really struggling to get my head around the superstring theory. The superstring theory seems illogical for the following reasons... 1. Nature demands symmetry. So...

Now obviously String Theory has been responsible for some valuable research, and even if the theory were completely disproven (although I don't see how; my understanding is that it is still too vague in it's predictions and descriptions to be proven or disproven conclusively). But String Theory...

Can Loop Quantum Gravity and String Theory coexist? What if String theory was correct in its description of matter and 3 of the 4 forces, with the only difference from modern M theory being that there is simply no real particle called the graviton, and instead, gravity is as is described by LQG...

Hi everybody, let's assume the Higg's boson exists. If I understand String theory correctly (and I understand very little of it), then Higg's particle - just as any other particle - can be expressed as a particular vibration state of a string. If I understand Higg's theory correctly, then...

Each year, the annual String conference provides us with a kind of snapshot of the field as it is today. The lineup of invited speakers and the titles of their talks give an idea of the current activity and interests of string researchers. This year Strings 2012 is in Munich and starts on...

I noticed that in quantum physics, an elementary particle has no dimensions, and is point like, but in string theory has one dimension. Why is this?

From what I understand, the Higgs Boson was the last missing piece of the Standard Model (12 indivisible particles, 4 forces). Now that the Standard Model is complete, has String Theory been disproved? Is there a conflict between the Standard Model and String Theory?

This may be a silly question since i am relatively new to the string theory. While going through a quantization of the bosonic string , I see a tower of states appearing corresponding to different modes of excitations of the bosonic string. Now I was trying to figure out how this whole machine...

A long time ago, physicists thought that only a small class of quantum field theories (QFT's) makes physical sense - those which are renormalizable. But then gradually it became accepted (Weinberg was the most influential figure in that regard) that QFT does not really need to be renormalizable...

I like to think myself as adequately familiar with the concept of String Theory and it's basic fundamentals, But I'm wondering if string theory offers explanations to the currently unexplained such as universal expansion, quantum Entangelment, radio active decay, why virtual exist, etc? Or does...

If String Theory explains/"leads to gravity, how does it not make predictions? String Theory "predicts" gravity. It can explain gravity and it explains "small" structures. If String Theory includes these two topics shouldn't it predict what happens when Quantum Gravity becomes non-negligible...

I'm not sure if this question is something that has been asked before or if i thought about it myself or if it's completely ridiculous! But I was thinking, if, according to String Theory, particles are 1-dimensional strings that go through modes of oscillation, could they describe how a...

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...

Can anyone give me a general sense of what the quantum master equation (or BV master equation) is and how it relates to string theory? I'm an undergraduate physics student and am hoping to do research with a professor on the topic, but need some basic knowledge on the subject.

Good evening. I am wondering if string theory and loop quantum gravity could be combined into a single theory. I have been trying to decide which of the two I should choose as my "religion," but I feel that both are correct. Could string theory and loop quantum gravity be different...

I have read in a couple different places that the math that comes out of string theory has helped a couple of different other branches of physics like quantum computing and condensed matter physics. Quote from: http://www.ams.org/news/math-in-the-media/11-2011-media "Maybe string theory is...

Hello all, I am currently a Junior in High School with a deep interest in Physics/Mathematics, specifically in the area of theoretical Physics and String Theory. I was accepted to a summer course on String Theory and am quite excited. The course stated that the only prerequisite is Single...

Hi, I was wondering what the scope is these days to do a PhD in theoretical physics, but without delving into string theory? Is the world of theoretical physics still very much dominanated by string theory, or can young physicists go down alternative routes? I seem to remember that some years...

The appearance here of threads such as Causes of loss of interest in the String program and Is string theory really science? are for me a symptom of the frustration of modern physicists struggling to formulate in a predictive way the concept of elementary objects that are geometrically linear...

I read somewhere that one power of string theory is that there is no adjustable dimensionless parameter in the theory. Why is this considered a strong point in favour of string theory? Second, how does the theory help in solving cosmological constant problem? Again there is no adjustable...

The scientific method says that if experiments or observations falsify a theory, that theory must be rejected. String theory requires space to have 9 dimensions. But observation shows that our space has only 3 dimensions. This alone should falsify string theory. I know that scientists have...

Are there any theories as to what could possibly cause/create the vibrating one dimensional strings in string theory? Are the strings at the lower end of electromagnetic radiation? Or something completely different?

--I understand that the original basis of string theory was as explanation for the ontological origin quanta . I have a few questions: 1) What is the origin and material make-up of the string? (How can we avoid the metaphysical pit-fall of an infinite regress in regards the ontological...

Hello everyone. I am an undergraduate senior anticipating degrees in both physics and astrophysics this spring. Until about a year ago I wasn't particularly sure what I wanted to do after graduation. However, after taking upper division QM and particle physics courses I've developed a great...

In a youtube video Paul Davies Beyond Belief, he said that string theory and M theory were so obviously and patently false that he didn't even bother to discuss them. I thought Lee Smolin was the only critic of string theory I didn't know that Paul Davies was one too. How much weight does...

Say you have a rudimentary grasp of classical physics and calculus. How many hours of study does it take before you can start to understand string theory. I'm not talking about how many hours does it take before you can actually make a contribution to the field, rather how long does it take...

In string theory, what are the small strings physically made out of?

In string theory, what physically causes the small strings to vibrate?

Hello, I was thinking of eventually studying some string theory and I came across Barton Zwiebach's book on the subject. Would this be a good place to start? I know some GR at the level of Schutz/Hartle, Schrodinger QM at the level of Griffiths, Classical Mechanics at the level of Marion &...