String Definition and 1000 Threads

Hello. So I am having some trouble answering this question and I would really appreciate some help. I figure I should probably first define what standing waves are and I know that they are the result of the repeated interference of two waves of identical frequency while moving in opposite...

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...

Homework Statement A disk of mass M and radius R is help up by a massless string. Let there now be friction between the disk and the string, with coefficient u. What is the smallest possible tension in the string at its lowest point? The problem is problem 8 from here...

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

Homework Statement A string has the fundamental tone of ##s_1 = A_1\sin (\omega_1 t - k_1 x)## Determinate the wave equation for the first harmonic of the string if the sound intensity level of the harmonic is 20dB lower than the fundamental tone. ##\omega_1 = 1360/s## and ##k_1 = 4/m##...

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).

This is not coursework; I am preparing for an exam and this question is from a past paper. We have access to past papers but we are not given the answers to them. 1. Homework Statement Two waves are generated on a string of length 2m, to produce a three-loop standing wave with an amplitude of...

i'm in 10th standard and am fascinated about theoretical physics.i have started reading books related to it-"brief history of space and time","The Elegant Universe"by Brian Greene.of all the stuff,i'm mostly interested in the string theory.my concern is that is there a scope for being a...

Is there quantum foam between strings?

what will be tension on string pulled by equal but opposite forces?

I had this question : if a diameter of a string is increased , how will the linear mass density(u) value changes ? the answer was it will increase because mass will increase , but how the mass has increased ? so what other factors affect the linear mass density ?* μ=T/ λ2 f2

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...

Homework Statement There is a question that says: A small bal of mass m is attached to the end of the string of length ##l=1m## whose other end is fixed. From its lower position, the ball is given a kinetic energy ##\frac {mgl}{5}##. Find the net acceleration (in ##m/s^2## ) of the ball at...

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...

A couple of simple, (maybe dumb) questions - Consider a string, maybe a meter long, with one end attached to a small rock, and the other end attached to the shaft of a motor standing so the shaft points upwards. When the motor is turned off, the string hangs limp. When the motor runs, the rock...

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...

Hi All, Is it correct to apply Huygens Principle to a situation in which a wave propagates in a string with fixed ends? I know Huygens principle is related to regular propagation e superposition properties of waves, and all these can be found in the string context, but I am not sure this...

how the wedge is connected with highlighted string?

Homework Statement Homework Equations F=ma The Attempt at a Solution A FBD on the bottom block gives tension in C is equal to Mg. Then, a FBD on the middle block should give T_b-T_c=0, so tension on B should also be equal to Mg. Finally, a FBD on the top block gives the tension on A is...

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

Homework Statement A string is wrapped around a disk of mass 2.1kg and radius 0.045m. Starting from rest, you pull the string with a constant force of 13N along a nearly frictionless surface. At the instant when the center of the disk has moved a distance 0.13m, your hand has moved a distance...

Homework Statement Hi, this is a problem regarding mathematical descriptions of waves. I've attached an imagine of the picture but I'll also type out the problem for clarity. "A sinusoidal wave is propagating along a stretched string that lies on the x-axis. The distplacement of the string as a...

Hey, Most related questions here specifically talk about torque, force, angular momentum/velocity etc. I just want to know how I can aptly describe the motion of the tip of some string as it wraps around a cylinder. So basically, the path of an object in circular motion with a decreasing radius...

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...

If we take one end of a mass-less string and pull it with force F, would the string have any tension in it? Would it have any tension when we pull it with force F from both the ends?

Hi, my level of knowledge of string theory is the following : I understand that to each elementary particle there corresponds a string vibrating at an associated frequency (mode). So my questions are : 1. Is there some table yet that proposes a correspondence? Such as : electron : so many Hz...

The way we have a phasor analysis for a point mass executing un-damped simple SHM, is there something like that for transverse waves on a string. According to me if we fix the position then we can focus on the isolated SHM at that particular position. Is there any way in which I can relate the...

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...

Hello everyone, just a quick question: I have heard that it is impossible to do research in physics by yourself anymore. I heard that "The days of Einstein are gone" and that nowadays in physics, especially string and quantum relativity research, everyone publishes in groups. I feel like this is...

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...

Homework Statement Derive the equation of motion for the system in figure 6.4 using Lagrange's equations [/B] Homework Equations m1=.5m m2=m strings are massless and in constant tension Lagrange=T-V The Attempt at a Solution I currently have the kinetic energy as .5m1y'12 + .5m2y'22 I am...

Homework Statement "A cylinder of mass m and radius R is lodged between crossed sticks that make an angle θ with each other. The crossed sticks, each of negligible mass, are connected at the point C, with AC=BC=2R and CD=CE=3R. Determine the tension in the string at DE. Assume the floor is...

Homework Statement A disc is on a desk, with a rotation point underneath. A string is wrapped around it, and the end of the string has a mass attached to it. The string end is put over a pulley, and when the mass is dropped it causes the disc to rotate. We are given mass of the disc (80g)...

We've got a 0,5m string attached to a frame and has its own fundamental frequency at 440Hz. We cool our system for 15°C. What is the proper frequency now? String length l=0,5m String section S=0,02 mm^2 String density ρ=7800 kg/m^3 Young module E=2*10^5 N/mm^2 Fundamental frequency ν=440Hz ΔT=...

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...

Homework Statement A new musical instrument is fashioned from a metal can of length L and diameter L/10, open at one end, with a string stretched across the diameter of the open end. The string is tensioned such that the 3rd harmonic frequency of the vibrating string matches the fundamental...

Hi, I am new here! 1. There is no actually data given, I am just supposed to explain why a string that crosses a pulley have the same tension both sides. The pulleys moment of inertia is zero and friction is negligible. There is a little hint in this problem that says; study equation 9-15...

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...

according to book "...Let us look at a particular wave crest generated at the left end of the string by a fork. It travels to the right end of the string, is reflected back, and is reflected again at the fork.Now it interferes with the next wave..." doubt: the fork keeps vibrating and keeps...

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.

Homework Statement A string is sewn in a 2D membrane. What is the amplitude of the reflected wave? All the parameters you need in order to get to the result are known. Homework EquationsThe Attempt at a Solution Ok, so we have a 2D membrane, with a string at ##x=0## along the the ##y## axis...

Can resonance occur at multiple frequencies for the same given instrument? For example, in a violin, each note on a given string (say A) resonates and is the loudest only at a specific point on the string. Since each note on the same string can resonate, and each note has a different frequency...

Hello, I was recently reading a physics book and was told that, if a string were to hang down with a weight attached to it, its tension would be the mass times gravity. However, if it were to gain some velocity and move from left to right, the tension would increase enough so that the string...

Homework Statement I am stuck on this problem: So the question is asking for F21, F12, F32, and F23. (That's the force by 2 on 1). The mass of m2 is variable. There are four cases where I need to solve for the forces: when m2 has mass of 3kg, 0.3kg, 0.03kg, and 0kg. The mass of m1 = 2.5kg, the...

Homework Statement (Im translating this from another language, so if it doesn't make any sense, please let me know and ill try to do a better job.) A metal ball (mass=120g) is hanging from a string (lenght=85cm). The ball is struck horizontally. When the angle of the swing reaches 125 degrees...

Homework Statement http://puu.sh/frpk5/eae7bce2e3.png Homework Equations v = sqrt(T / (m / L)); The Attempt at a Solution 7.86 g / cm^3 = 7860 kg / m^3 T = v^2 * m/L T = 160 ^ 2 * 7860 which is a huge number I have no idea where the diametre plays a part.