Particles Definition and 1000 Threads

Why do photons only interact with charged particles?

The book explains covalent bonding is due to exchange forces of attraction, which isn't a real force but the last term in [5.22]. This term arises due to electrons being indistinguishable particles. If electrons were distinguishable, there would be no exchange forces. Then, would there still be...

The summary, erm, sums it up. I just can't wrap my head around "probability." ...Does space even exist? And the field thing I'm really half-remembering. I read somewhere particles are vibrations in fields, or fields bumping into each other, or something. What's a field?

Hello, I'm doing some refreshers before going back to school. Stat mech is my shakiest and I'd appreciate some help on this problem. I know that for a single particle, the partition function will be $$Z = 1 + 2e^{-\beta\Delta} + 2e^{-4\beta\Delta}$$ and so its internal energy is $$\frac{1}{Z}...

I actually have 0 clue how to approach this. I'm thinking this might have to do something with the Stern-Gerlach experiment, but I don't know how that would help me test a spin-0 particle. If anyone could please help me with this, that would be great!

Problem Statement: It is possible to describe synchrotron radiation as caused by a loss of electrical charge of relativistic particles that are moving in a magnetic field? Relevant Equations: E = mc2 An Italian expert of black hole M87 (Elisabetta Liuzzo) explains that the expected axial...

Let's for example consider the Z boson. It can't directly be detected; so is it ever really correct to draw it as an external line on a Feynman diagram? I've seen processes involving it before be written as something -> Z + something, then Z -> ... but since unstable particles aren't really on...

assume i have a gass made from N identical particles in a box and i want to calculate the probability for k out of N particles to be in the left side of the box. the problem is ,that if we treat the N particles as identical , each state in which exacly k of the N particles are in the left side...

I am new here so apologies in advance. When a virtual particle and anti particle appear at the event horizon of a black hole, before they destroy each other, they are split with one being sucked into the black hole and the other becoming exhaust. Are these the same particles as the quantum...

I was talking to a physicist who said to me that virtual particles can have a mass of a constant times by i ,as in the root of -1. I have been thinking about this more and it intrigues me. I have done some research into this and can't find further details. If they have an imaginary mass does...

I tried to apply the chain rule $$X_{ik} = \frac {\partial U}{\partial \xi_{ik}} = \frac {\partial U}{\partial x_{i}} \frac {\partial x_i}{\partial \xi_{ik}} = \frac {\partial U}{\partial x_{i}} $$ and I got the force x-component of the force acting on ##P_i## I guess. but I do not know what...

A lecturer today told the class that relativistic QM for single particles is flawed by showing us that for a state centered at the origin, it was possible that ##Pr(\vec{x}>ct)>0##. He said that this was down to the fact that we should be considering multi-particle states in relativistic...

I'm reading Mechanics by Landau and Lifshitz, chapter IV, and trying to understand how in a (closed) center of mass system, with randomly distributed and oriented particles that disintegrate, "the fraction of particles entering a solid angle element ##do_{0}## is proportional to ##do_{0}##, i.e...

Hello! I am a bit confused about the distinction between virtual and real particles. For example a Z boson, which has a very short lifetime, in all experiments will decay to some other stable particles (i.e. it is detected through its decay). This means that it will always appear as a...

I need some clarification on how the Higgs field work. The popular science explanation explains the effect on moving particles the way an object would be impacted by moving through a medium of maple syrup. I understand this is a very bad, inaccurate analogy. What I want to understand is does...

If virtual particles are supposed to be some sort of Green's function excitation of a field following a particular Lagrangian or PDE (induced by the presence of another particle, free or virtual), then why are they allowed to be "off shell"? (Especially: Why are they allowed to be nonzero...

Summary: I have found the Hamiltonian for the free particles and the electromagnetic field (##\mathbf{E}## - electric, ##\mathbf{B}## - magnetic) to be (non-relativistic !): ##H=\sum_i \frac{m \dot{r}_i^2}{2} + \int d^3 r \left(\frac{\epsilon_0}{2} E^2 + \frac{1}{2\mu_0} B^2\right)## (1)...

Hello, I'm trying to couple 3 spin 1/2 particles. So far, I have been able to find the coefficient for the other states but I can't get the results for ##j_{12} = 0## to ##j_3=1/2##. Here is my attempt: 1) Using CG table...

Hello, I am a high school physics teacher, and I have been thinking about a way to model quantum mechanics in an intuitive way in order to teach it better, but I don't want to lead my students down the wrong path. I am certainly no expert in quantum theory. In looking at the guidelines, I...

The Schrödinger equation can be derived from the path integral quantization of the Lagrangian of classical, non-relativistic particles. Can the Klein-Gordon (and maybe the Dirac) equation be derived from the path integral quantization of a given classical (supposedly relativistic) Lagrangian of...

Most of the mass of matter comes from energy of strong force interactions between quarks. However the quarks still have intrinsic mass. Other particles have no intrinsic mass but still have energy. So according to mass-energy equivalence, these particles should still have effectively mass, to my...

Do magnetic lenses do work on charged particles flowing through them? Intuitively I would think yes because the magnetic field produced by the electric current in the coil is applying a force on the particles flowing through the lens, so therefore an electric current (the beam of particles to...

Summary: What is energy of proton, deuteron and alpha particle in circular motion of the same radius. Hello, I have a problem. Here is the content of an exercise: In some experiment, proton with energy of 1MeV is in circular motion in isotropic magnetic field. What energies would have...

What I did was consider a circular orbit around the Sun. We'll have the comet's velocity tangential to its movement (vorb) and a radial velocity pointing towards the sun due to the ejected particles (vej). Therefore we can find the total velocity to be vtot=√(vorb^2 + vej^2). What I did after...

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if lithium 7 3 captures proton, it is divided into two alpha particles. Calculate the kinetic energy of the alpha particles. the proton energy can be neglected and the mass of the nucleus of Li is 7,01601u. I only know how to write the equation: 3Li7 + 1H1 → 2He4 + 2He4 Can anyone help me? How...

A charge is entering magnetic field perpendicularly! Griffiths says it motion will be circular! But it is accelerated so it must radiate energy and it's motion should be spiral inward?

I was just curious if there were any known (theoretical) particles with zero inertial mass that don't travel at light speed. Is this even possible?

If you have enough information could you not determine with certainty the movements of pollen particles in water? In other words, if you were able to measure the movements the particles, then repeat the exact same experiment, with all things controlled, would the particles move in the same way...

I want to compute the fraction of time both particles spend outside the finite potential well. All I can get is the probability to find them outside. The wavefunction outside the potential is: $$\frac{d^2\psi}{dr^2} = -L^2 \psi$$ Where: $$L = \sqrt{\frac{2mE}{\hbar^2}}$$ Solving the...

Can someone help me with this excercise?: Consider two electrons constrained to move in one dimension. They interact through the potential $$ V(x) = \begin{cases} 0, & \text{ if } |x| > a \\ -V_{0}, & \text{ if } |x| \leq a \end{cases} $$ where ##x## is the relative coordinate. The total spin is...

I am studying identical particles and I have some doubts. Considerer two identical spin 1/2 particles interacting through a central potential ##V##. In the rest of CM, the hamiltonian is $$ H = \frac{\textbf{P}^{2}}{2M} + \frac{\textbf{p}^{2}}{2\mu} + V(r),$$ where ##\textbf{P}## is the momentum...

Homework Statement Two particles in a high-energy accelerator experiment approach each other head-on with a relative speed of 0.890c. Both particles travel at the same speed as measured in the laboratory. What is the speed of each particle, as measured in the laboratory? Homework Equations...

Is it correct to say that free particles always follow geodesics?

Homework Statement Construct the four lowest-energy configurations for particles of spin-##\frac{1}{2}## in the infinite square well, and specify their energies and their degeneracies. Suggestion: use the notation ##\psi_{n_1,n_2}(x_1, x_2) |s,m>##. The notation is defined in the textbook...

Homework Statement 28. Particle A (mass = m, charge = Q) and B (mass = m, charge = 5 Q) are released from rest with the distance between them equal to 1.0 m. If Q = 12 μC, what is the kinetic energy of particle B at the instant when the particles are 3.0 m apart? a . 8.6 J b. 3.8 J c. 6.0...

In my lecture notes, the normalisation for such a bosonic state was given by However, I can't quite seem to grasp how the normalisation factor came about. Could someone walk me through it? Many thanks in advance!

Homework Statement I'm trying to reconcile the answers to two questions regarding the average potential and kinetic energies in simple harmonic oscillator Question 1: The average potential energy of the vibrational motion in the ground state of a diatomic molecule is 12 meV. The average...

Since there is no privileged inertial frame, I would have expected the first particles in the universe to have no particular bias in their momenta. Relative to an observer I would expect the distribution to be uniform and unbounded. The mean momentum of the initial particles relative to an...

When I first learned about these subjects, I did what was intuitive to me and treated particles as if they carried potential energy. I would do this similarly for rigid bodies where I would also treat them as a particles with their body's mass at the center of mass. This wasn't helped by...

I just saw this public lecture and I really enjoyed it (the lecture begins at about 18 minutes into the video). He is an engaging and rather funny speaker. At the end there is a Q&A in which he for instance goes into some of the misconceptions about quantum mechanics. David Kaplan is also one of...

Good day everybody! As we have already known the structure and operation of the cloud chamber, can someone explain to me why the cooling is done at the bottom of the chamber and the heating at the top, but not vise versa?? How this affect the function of the cloud chamber?

Hello. I started to work on pedrotti optics book (2nd edition) and i got confused about what is relativistic mass and why we use it rather than kinetic energy (1/2mc^2)? Also in the beginning of these explanations there is one equation i barely understand nothing out of it. Could you please...

Homework Statement Two objects ##1## and ##2## move at constant speeds ##v_1## and ##v_2## along of two mutually perpendicular lines. At the moment ##t = 0## the particles are located at distances ##l_1## and ##l_2## from the point of intersection of the lines. At what time will the two objects...

Chemical potential is defined as the change in energy due to change in the number of particles in a system. Let we have a system which is defined by the following Hamiltonian: $$H = -t \sum_i^L c_i^\dagger c_{i+1} + V\sum_i^L n_i n_{i+1} -\mu \sum_i^L n_i$$ where ##c^\dagger (c)## are creation...

Thought experiment: If we had one kilogram of Helium in a nonpermeable box in the middle of the void between sol and our nearest Stellar neighbor and we left it there with no other interractions (all other things being equal) what happens to those electrons protons and neutrons ASSUMING no high...

Homework Statement Mass of m1=90kg Inclination is 40degrees. (see the attachment) a) What must be the size of m2 , to hold the system in balance (no movement) ? b)what must be the size of m2 at least, to make m1 move upwards. The static friction coefficient between m1 and the plane is 0.3...

I am doing DMRG (in traditional formalism, not MPS) for Hubbard model H = -t ∑i ∑σci,σ ci+1,σ + U∑ini,σni,σ- In every iteration we add two sites to the system, but how do we set that how many particles are allowed in the system?

I just confused about it.Why can't we discribe a particle just one wave function instead of wave packet(group of waves with different phase velocities)?