Path Definition and 1000 Threads

Hi all. This may be a stupid question to some.. But please do answer it. Why do planets move in an elliptical path? Why only ellipse? Or even a circular path for approximation? Why not a path which has corners? Like an octagon or a square?

Suppose you have the transition amplitude in the presence of a source <q''t''|q't'>_{f} To extract the ground state, we change the Hamiltonian to H-i\epsilon , because we can write: $$|q't'>=e^{iHt'} |n><n|q> \rightarrow e^{iE_0t'} |0><0|q>=<0|q>e^{iHt'} |0>=<0|q> |0 t'> $$ where only...

Two questions about the path integral: a) Intuitively, how does one (as Landau does) start quantum mechanics from Heisenberg's uncertainty principle, which states there is no concept of the path of a particle, derive Schrodinger equation i \hbar \tfrac{\partial \psi}{\partial t} = H \psi the...

Say I have a large spacetime lattice set up on a supercomputer where I calculate the scattering cross section of two spinless electrons of equal and opposite momentum via lattice QED. To get the right results we must add the amplitudes for every possible "path" the field can evolve from initial...

I am a senior right now in high school and am pretty much deciding the beginning of the rest of my career right now. Ultimately, I would love to study both physics and computer science with either a double major or with computational physics. I love learning about mathematics, physics, computer...

I'm currently a sixth form student in Jamaica starting to think about career paths to take. I'm in love with math and I'm sure ill never drop out of love with it. But I'm a little uncertain about which career path to take. I was thinking of either doing acturial science but wonder if the job...

Say we try and calculate the ground state energy of the bound state of a quark antiquark meson via lattice QCD. Say I look at one space time lattice point of one path. Do the fermi fields "live" on the lattice points? Do the boson fields "live" on the legs between the space time lattice points...

If we diminish the intervals Δt between measurements to zero, we can definitely know the path of the electron. Isn't it?

Hello everyone, Here is the definition of path connected and domain my textbook provides: Definition 171. An open set S is path connected if each pair of points in S can be connected by a polygonal line (e.g. a finite number of line segments connected end to end). A domain is an open set that...

1. "William Tell is said to have shot an apple off his son's head with an arrow. If the arrow was shot with an initial speed of 55m/s and the boy was 15m away, at what launch angle did Bill aim the Arrow? (Assume that the arrow and the apple are initially at the same height above the...

Hey guys, I am a software developer who plans to go back to school in September 2015 to get a degree in physics. I live in Europe so I will have to get a bachelor's degree (3 years) then a master's degree (2 years). I am 26 years old and at the moment, I spend all of my free time re-learning...

Homework Statement (We are to solve this with Monte Carlo programming. Based on the universe from Olber's paradox) Suppose you are in an infinitely large, infinitely old universe in which the average density of stars is n = 10^9 Mpc^−3 and the average stellar radius is equal to the Sun’s...

Hello everyone, well this is my first post and i hope someone could help me I'm starting choosing what to study now and at first i choose Aerospace Engineering, but now I'm towards to Computer Engineering. Also I'm really interested on audio and acoustics. I saw an university that have Acoustics...

So, I am a student at the university of Richmond, a small liberal arts college, and my goal coming in was to go for the 3/2 engineering program partnership with Columbia, but I decided that I wanted to go into Mining and Minerals, which happens to be one of the few Engineering programs that...

Hi guys! Sorry I'm new so the questions might seen a bit vague but I'm unclear about a lots of things I want to make a career purely in physics, I'd prefer cosmology and theoretical physics because that was I was so interested in from beginning. But I've heard the career in theoretical physics...

Homework Statement A satellite has a circular orbit 500 km above earth. A ball is thrown directly downwards radially at 20 m/s. Find the path of the ball relative to the satellite. Homework Equations mv^2/r=GMm/r^2 The Attempt at a Solution From the height of the orbit you can easily solve...

Homework Statement hi,guys! Problem: s(t)=At-Bt^2+Ct^3,where A,B,C is know constants. What is the path,velocity and accelartion after 2s from beginning of motion. Homework Equations The Attempt at a Solution So v(t)=s'(t) a(t)=s''(t) But where i get confuzed is when I am asked to calculate...

I'm searching for a week from now and can't find out difference between optical and geometrical length in optical path. Can anyone explain or give me idea or how can I find it out?

my book says that the surface integral of a gradient field is path independent so long as the gradient field is continuous. This seems fishy to me. I'm envisioning a continuous gradient filed where z=grad f(x,y) and the object traced out looks like a mountain range. The equation for such a...

Hello I'm struggling with well-known problem of finding shortest path between two points on a sphere using calculus of variations. I managed to find correct differential equations of great circles, but I'm not confident about validity of methods I used. Below I describe my approach. In...

I am unable to prove step 8.3 in this proof of the path integral formulation of molecular dynamics https://files.nyu.edu/mt33/public/jpc_feat/node11.html Any help would be much appreciated.

Homework Statement A transparent flim of thickness t and reflective index n is placed in front of Y . Which one shows the new condition for destructive intefrence to occur ? the ans is (n-1) t = m λ . In my opinion , it should be (n-1) t = (m-0.5) λ , because for destructive interference...

Suppose that I have already calculated the two-point correlation function for a Lagrangian with no interations using the path integral formulation. \langle \Omega | T[\phi(x)\phi(y)] | \Omega \rangle = \frac{ \int \mathcal{D}\phi \phi(x)\phi(y) \exp[iS_0] }{ \int \mathcal{D}\phi \exp[iS_0] }...

I'm a 1st year Physics student from the UK that's trying to get informed. After seeing the patent attorney thread, I did a little digging. Not sure how it works in other places, but in the UK you're required to have a degree in science (not a PhD, and as far as I'm aware, there's no requirement...

Hey! (Blush) I am looking at the proof of the following sentence: Let $s \to u \to v$ a shortest path from the vertex $s$ to the vertex $v$. Suppose that we relax at some time the edge $(u,v)$.If,before the call of Relaxation(u,v,w),it stands that $d[u]=\delta(s,u)$,then after the call of...

Hi, I am trying to derive the path length of a charged particle in a B-field. I am assuming the particle will travel a distance L along the applied field. Using the following equations for the path length of a helix and gyroradius: Helix defined as [a*cos(t),a*cos(t),b*t] for t on [0,T] has...

Homework Statement for part a , in order to produce first minima from the central bright ray , the path differenece between 2 ray should be equal to λ/2 or 180 degree am i right? why the notes give the path differenece = λ ...If path differenece = λ , the two light ray are in phase right...

Homework Statement i can't understand why the optical path diffrence is 2nt+0.5λ. why is it so? the 0.5λ is due to the path difference change of 180 degree of when it is reflected lower ray when it is reflected from the lower glass surface... why there's also phase change of 2nt. since both...

Hi everyone Homework Statement I'm trying to understand the Laue equation but I have problems unterstanding the derivation, especially one part in my textbook about the path difference (see attachment) The Attempt at a Solution My textbook says that the path difference here is...

Homework Statement for diagram 2 , i just can't understand why S1P -t + ut (upper ray ) is longer than the lower light ray (S2P) , ? if I take S2P minus ( S1P -t + ut ) , then i would get mt t (thickness ) is negative , which is indeed wrong! so it has shown that optical path of the upper...

Homework Statement In this question, when S2 is covered with a very thin glass, the fringe move toward Y . why is it so? Homework Equations The Attempt at a Solution

This is my first posting, so forgive me for any errors I am making. A quick review of topics in the past shows that my question has been touched on in the past, but was not (in my opinion) given any serious attention or consideration. Over the past 5 years or so, I have witnessed (almost...

I'm a mod developer and I would need some help to calculate best path/route to take for an entity. To keep this post more math related than game programming related I'll try to explain this process easily. Basicly the entity (spaceship) tries to fly in 3d-space from point A to point B and it...

Hi all This question came up to me when I was playing a game called KSP (a space sim game): Given an initial velocity and starting altitude, how do you create a 2D Cartesian equation of the orbit of that projectile around earth? For example if I told you a projectile is traveling at a...

Can anyone suggest me a good reference for path integrals (QFT), apart from peskin.

Hi, I am studying path integral formulation from Ballentine. Till equation 4.50, I follow quiet well. G(x,t;x_0,t_0) = \lim_{N \to \infty}\int\ldots\int\left(\frac{m}{2\pi i\hbar\Delta t}\right)^{\frac{N+1}{2}}\exp{\sum_{j=0}^{N}\left(\frac{im(x_{j+1}-x_j)^2}{2\hbar\Delta...

does anyone have a proof of this?

Hi Just wondering about the orbital path of a high speed particle - eg electron in orbit. Is it length contracted? Then how do we manage nλ=2.π.r ? Neil

Hey all! I am currently doing a computer science project for a scientific collaboration at an REU this summer. I am a physics student and I plan to be a researcher one day. I really do not want to continue this project for two main reasons: I simply do not know the computer science...

Hi, I'm giving a talk tomorrow morning, and I'd like to use the following fact: a path-connected subgroup of SO(3) consists of either a) only the identity, b) all the rotations about a single axis, or c) all of SO(3). Unfortunately, I can't for the life of me find where I read it, and I'm not...

Hello everybody, I am Victor Moussalli, 17 years old, just starting grade 12 of high school. My passion is energy efficiency. The only types of engineering that I like are: environmental, energy, and electrical. I want to know what is the best path to take; university or not, to guarantee a...

Homework Statement Electron A is fired horizontally with speed 1.00 Mm/s into a region where a vertical magnetic field exists. Electron B is fired along the same path with speed 2.00 Mm/s. Which electron has a path that curves more sharply? A does. B does. The particles follow the same...

Homework Statement A missile and an aircraft are separated initially by a distance 'L' on the y axis. The aircraft starts moving along the x-axis with constant velocity 'u'. The missile is heat seeking which makes it point towards the aircraft at all times. The velocity of missile is 'v'...

(1) Exact form of U exists because of the results of experiments in adiabatic work, what are such experiments which gives proof for above statement? (2) Is differential of Internal energy dU path dependent?

Hi All, I am trying to understand the some of the properties of wakefields, namely the energy change. So, as a preface I am interested in primarily the wakefield due to electron beams as they progress through a curved section (the eletcrons radiate strongly when they are in circular motion)...

So I'm a junior in high school currently with a very, very strong interest in neuroscience, among other sciences (specifically chemistry and physics), and engineering as well (part of school's FIRST robotics team as lead programmer). For the past few months or so, I've been exploring academic...

Hi, my name is Tristan Barrow, I know this forum has gotten a lot of questions like this but none of them really fit my particular needs so I thought I would ask it again. Do the math subjects I am interested in lead me to Quantum Mechanics? If not what would be the best place for me given...

Hello Physics Forums, I'll be graduating with an Ms in Applied Physics in 2014/15. I could see myself getting deeply interested in high energy theories from SM to SUSY to LGR to string theory. Particularly string theory - even before my first lecture on F=ma I daydreamed about a rudimentary...

Hey! :o I am facing some troubles understanding the proof of the following theorem. Let $\overrightarrow{F}$ be a vector field, $\overrightarrow{F}=M\hat{\imath}+N\hat{\jmath}+P\hat{k}$, where $M,N,P$:continuous at a region $D$ ($M,N,P \in C^0(D)$) . Then a suficient and necesary condition so...

Homework Statement problem form div curl grad and all that by h.m.schey An object moves in xy-plane in such a way that its position vector r is given as a some function of "t" by r= i acosωt+j bsinωt show the object moves on the elliptical path Homework Equations (x/a)^2+(y/b)^2=1The Attempt...