Particle Definition and 1000 Threads

Homework Statement Consider Compton scattering of a photon by a moving electron. Before the collision the photon has wavelength λ and is moving in the +x-direction, and the electron is moving in the −x-direction with total energy E (including its rest energy mc2). The photon and the electron...

Given a source of electrons, like from an electron gun. Physicists call these freely traveling particles and often use a Gaussian wave packet to represent them with the group velocity being precisely defined as the velocity of the center of the packets. But if we do not measure the position of...

Hi all, Question for which .I feel silly asking - but since I'm still learning: A particle state in QFT is considered to be an asymptotic state with a well defined energy. Now, if I take an ensemble of particles after a very large number of interactions (say, e.g., a macroscopic object like a...

I think I've asked this question here before but I'm still not clear about the answers. To reiterate, some experts on this forum seem to be of the opinion that wave particle duality doesn't exist anymore and this has been expressed in different threads and in different ways with certain...

I was thinking about the "distribution" of a particle in space in different situations. An electron bound in a atom have a wave function that is broad. What about the broadness of the wave function of conduction electrons in a wire? Or doesn't it even make sense to quantum-mechanicaly speak of...

[Moderator's note: posts from several threads on the same topic have been merged into this thread.] When we measure the EM field of a charged particle, what exactly are we measuring? Are we measuring the position of the EM field, the strength of it, what? Does a penning trap measure the EM...

Suppose we have a classical particle in box. The number of degrees of freedom is 6. The position of the particle and its momenta. Now if we want to calculate the entropy of the system as a function of the energy we only need to find a relation between all the possible states the particle can be...

"The search for water, or even signs of life, on the planet Mars has been ongoing for some time. But with today’s announcement by CERN and NASA scientists, the exploration of the red planet has revealed a major new discovery. New images of the surface of Mars taken by NASA’s Mars Reconnaissance...

Consider a small rigid spherical particle of radius a, fully immersed in a viscous incompressible Newtonian fluid of shear viscosity η above a hard-wall with stick (no-slip) boundary conditions, located at the plane z = 0. A constant positive (external) torque Tx is applied on the particle. My...

What does "fluid particle is an abstraction" mean? https://confluence.cornell.edu/display/SIMULATION/Big+Ideas%3A+Fluid+Dynamics In the second vid. Thank you.

Everything in the universe that has a beginning seems to also have an end. Stars, galaxies, molecules, atoms. But what about elementary particles? In case of heat death would it become a uniform quark soup?

Homework Statement [/B] A particle detector shows tracks produced by two particles X and Y that were created by the decay of a lambda particle at O. Which of the following is a correct statement about energy at the decay? The energy of X must be greater than that of Y. The combined energy...

http://depts.washington.edu/uwptms/research.html In a penning trap where they use sideband detection of the particle, they need to "drive" it. But what does that mean? Is the position of the particle detected anywhere along this process?

How do we solve the particle in a box (infinite potential well) problem using matrix mechanics rather that using Schrodingers Equation? Schrodingers Equation for this particular problem is a simple partial differential equation and is easy for me to follow. The solution has the following...

Homework Statement Considering a neutral particle with spin +½ and a dipolar momentum μ placed on an uniform magnetic field. Find the variation of the expected value of the 3 cartesian components of the angular momentum spin operator for the following situations: a) the angular momentum of...

Context: In James Hartle's Gravity, pp. 318-319, Example 15.1, he considers the case of a particle that starts falling from infinity into a Kerr black hole, initially with no kinetic energy (e = 1) and initially moving radially (ℓ = 0). The particle's motion is constrained along the equatorial...

Every magnetic object has a magnetic moment. From electrons to molecules, to even planets. But my question is, what determines how much of a magnetic moment a quantum object has? I'm not sure if "how much" is the right word for it. What determines the "quantity" of a magnetic moment of a...

Homework Statement (a) A spaceship at rest in a certain reference frame S is given a speed increment of 0.50c. Relative to its new frame, it is then given a further 0.50c increment.This process is continued until its speed with respect to its original frame S exceeds 0.999c. How many...

Hi all, I recently flipped through a paper which got some press several years back, entitled "A Scenario for Strong Gravity in Particle Physics: An alternative mechanism for black holes to appear at accelerator experiments." There are a lot of speculative elements in the work, but the thing...

Given that an unstable particle has a constant probability of decaying per unit time, why is it said that its chance of surviving falls exponentially?

Hi, I'm not sure if this idea is something old that's been discussed to death or something I'm not formulating right, but i can't find anything online like what I would expect to. What I mean, is a list or rather a table of all possible elementary particle transformations and couplings from...

The energy equation for a particle contains the rest mass and momentum. If the momentum is zero, all the energy comes from the term mc^{2}. That means the particle still holds some energy. What is the form of that energy? For example string theory explains particles as vibrating strings, and I...

How anything can be a particle or wave at the same time.

This is a question that has been bugging me for a little while. If sound propagation in air changes from an adiabatic to an isothermal process (for example via the use of fiberglass or other heat conducting material), the wave velocity is lowered due to the reduction in the bulk modulus of air...

There is a video from the Space Station here: At around the 1 minute mark, you see the stability of the CD player when the CD inside is spinning. Don Pettit goes on to tape additional CD players together at 90 degrees to the original to make it stable in 2 directions, but my questions is are a...

I'm trying to get my head around some ideas in Quantum Mechanics, but I'm trying to find a visual/mental image of the ideas, so that I may, in some cases, understand a little better, if that's even possible. I have a mental image of wave/particle duality and I'd like to know if it's a valid...

In GR. What's the worldline of a quantum particle before and after it undergoes state reduction (before and after Born rule applied)?

Hi I will write physics terms but actually this is a math problem. Consider a particle which moves in accordance with the following equation $$m\boldsymbol{\ddot r}=\boldsymbol B\times\dot{\boldsymbol r}-\frac{\gamma}{r^3}\boldsymbol r,\quad r=|\boldsymbol r|\qquad (*)$$ and...

Hello! I am trying to write a program that solves the Schrodinger Equation for a particle in an infinite square well. I did a lot of research regarding the methods that could be used to accomplish this. I am writing this program in Matlab. The method I am using is called the Shooting Method. In...

Recently, I was thinking about fusion and this thought struck my mind. In tokamaks, the plasma is heated to extremely high temperatures in order to supply enough energy to the ions for them to fuse. But since, the plasma follows a Boltzmann maxwell distribution curve,only a few ions have have...

We know that when many particles are shot through the double slit they make an interference pattern. Also when a single particle passes through double slit it makes an interference pattern, ie one particle passing through two slits at once. But when we put a particle detector near the slits...

I heard that even particles with a mass can be described as waves. The frequency of the waves increases with the speed of the particle. So what would be the wavelength of an electron moving at, let's say, 1m/s?

Homework Statement Can't really find out b, probably due to a mistake in a. Was wondering what I did wrong. Homework Equations Kinematic equations of motion, w/ constant a ##F=qE## The Attempt at a Solution [/B] (a) ##E=\frac {\Delta V} {\Delta d}= \frac {V_R-V_L} {L} = \frac {V_0}{L} ##...

I'm doing some special relativity exercises. I have to find $$x(t), v(t)$$ of a charged particle left at rest in $t=0$ in an external constant uniform electric field $$\vec{E}=E_{0} \hat{i}$$, then with that velocity I should find the Liénard–Wiechert radiated power. I will show you what I did...

Hello, at the moment, I am working on my project of particle acoustic levitation, but I want to move the particles in a certain direction. In order to generate ultrasound wave for moving a particle, I want to use two transducers. Now, my question is: Has the reflection of those sound waves...

Homework Statement I post here to check if I am in the right way to understand this point in the book. The wave function of free particle is ##Ae^{\frac{i}{\hbar}(px-Et)}##.This could be regarded as ##{\phi}(x,t)=Ae^{\frac{i}{\hbar}S(x,t)}##. ##S(x,t)## is the free particle's least action...

According to this article an electron can be split into 3 quasiparticles: ‘holon’ carrying the electron’s charge ‘spinon’ carrying its spin ‘orbiton’ carrying its orbital location The article links to an experiment that was made in 2012, where physicists were able detect the spinion and the...

Anti-particle is particle that moves back in time ? Jonh Wheeler has an argument about it ? Is this really true ? How this works ? Thanks

Homework Statement I need to show that a particle suspended on a spinning liquid (which is spinning with constant angular velocity) describes a spiral . (I need to solve this without using Lagrangian-Hamiltonian formalism)Homework Equations [/B] Weight and Bouyant forceThe Attempt at a...

When we say a fundamental particle is 0 dimensional, is that literal or figurative? Is it physically possible that a particle has it's properties (like charge, mass) spread out in a finite volume, but can be "shrunk" to increasingly small volumes when we measure it?

So I had a test and this was the only exercise I miss points at and I can not understand why, I did everything according to my class notes. A particle moves according to the following equation: x=( −0.00521 cm/s^4 ) t^4 +( 0.0895 cm/s^3 ) t^3 + ( 0.335 cm/s^2 ) t^2−( 1.881 cm/s ) t−1.237 cm...

Are the physical properties of a particle spread out through the wave function in bohmian mechanics? This is from wikipedia "Also, unlike in classical mechanics, physical properties (e.g., mass, charge) are spread out over the wavefunction in de Broglie–Bohm theory, not localized at the position...

Homework Statement A beam on Pions, Kaons and Protons, all with momentum ##\mathrm{P} = 10 \mathrm{GeV}## and negligible angular divergence travels ##100 \mathrm{m}## before hitting a target. What is the required timing resolution of the detector so that pions and kaons can be distinguished...

Say we have a particle, like an electron in a double slit experiment. And say that we have a measuring apparatus to detect it right after its fired out of the electron gun. And after that it goes through the double slit and hits the detector plate. Would we see an interference pattern? If the...

Why are particle with half integer spins anti-symmetric while integer spin particles are symmetric? Or in other words, how does spin relate to the symmetry of indentical particles?

Homework Statement Consider a charged particle entering a region of uniform magnetic field B - for example the Earth's field. Determine it's subsequent motion when the y-axis is parallel with the magnetic field Homework Equations F=qv x B = ma vector components of velocity, acceleration, and...

14 February 2017: First single experiment observation of the decay Bs0→ μ+μ-. From discovery to precision measurement. [ Branching fraction Bs0→ μ+μ- = (2.8±0.6)x10-9 ; B0→ μ+μ- < 3.4x10-10 ] "“We love this decay because it is one of the most promising places to search for any new effects of...

I have been through following papers for research: 1)http://cdsads.u-strasbg.fr/cgi-bin/nph-iarticle_query?1990ApJ...362..584M&amp;data_type=PDF_HIGH&amp;whole_paper=YES&amp;type=PRINTER&amp;filetype=.pdf 2)https://arxiv.org/pdf/gr-qc/9905054.pdf Conclusion of the second paper given above...

So I'm doing some research for a physics essay on particle accelerators and I don't want to go into too much mathematical detail (as I haven't studied statistics or higher level Physics at school yet), but I have googled a lot of things and nothing seems to come up for methods scientists are...

Homework Statement A particle of mass M and 4-moment P decays into two particles of masses m1 and m2 1) Find the total energy of each particle (lab frame). 2) Show that the kinetic energy T1 of the first particle in the same reference frame is given by $$T_1= \Delta M (1 - \frac{m_1}{M} -...