Particles Definition and 1000 Threads

Let's say I have two particles A and B and I want to find the total charge parity of the system ##C_{AB}##. In what cases is it allowed to say ##C_{AB}=C_{A}.C_{B}##? I suspect that if A and B are their own antiparticles, then that is OK. Is this even the case when the system has a relative...

Does anybody know what happens when say a laser accelerates charged particles? Do photons get absorbed and the intensity of the laser drops, or do they get absorbed and scattered and there's a redshift of the photon etc

Do elementary particles, e.g. electron, protons, etc, have material substance in the ordinary meaning of substance? If so, what is the substance?

When my eighth grade daughter was studying physics in her class, I watched a movie with her on the Hadron Collider (" Particle Fever "). We discussed atoms, electrons, protons, neutrons; we discussed orbits and statistics, and then down into the standard model and fermions, leptons, yadda...

Homework Statement Suppose that in a fixed-target proton-proton collision, the two protons are scattered with equal energies at equal angles θ/2 to the beam. Show that in the CM frame, this implies they are scattered at right angles to the direction of the beam. Calculate the energy and...

A complex classical field Φ of particles is, by itself, invariant under global phase changes but not under local phase changes. It is made gauge invariant by coupling it with the EM potential, A, by substituting the covariant derivative for the normal partial derivative in the Lagrangian. But...

Hello, My question on virtual particles is quite simple but I cannot find an answer. Are virtual particles just a filler for math or do they actually come into existence?

Hello! I'm struggling with a probably easy physics question concerning random walks. Here I have the slide regarding this: Delta is the distance that a particle moves. Can someone explain where the n-1 initially comes from? Does it have to do wtih the concept of the degrees of freedom? Than...

When we say that elementary particles are wave-like in nature does that encompass, lead to and necessarily imply the fact that they travel in wave-like trajectories or is wave-like displacement a separate, distinct notion from their wave-like intrinsic natures? IH

Why are particles in QFT assumed to be point-like? This assumption is the source of ultraviolet divergences. Does anyone know what is the source of this assumption, and what happens if you assume that particles are not point-like?

The probability of finding one single particle at energy ##\epsilon## in a system of such distinguishable particles at thermal equilibrium in the thermodynamic limit is given by the Boltzmann distribution that is: (up to a constant factor in front) ##e^{-\frac{\epsilon}{kT}}## To find this...

https://www.sciencenews.org/node/20378 Y'all might find this interesting. John Conway and Simon Kochen's 1-0-1 theorem. I have no questions. Sorry.

I need to ionise lots of particles quickly. Upwards of 1kg /sec. What's the best way of doing this? I'd consider pre ionised solutions boiling etc. Thanks

I'm wonder what particles have mass. Is it true that only fermions have mass and bosons do not? Or is it true that only those partices which have an antiparticle partner are those that have mass? I believe that the higgs boson has mass and does not have an antiparticle partner. Are there others...

Homework Statement I'm making a program that draws a graph of the weight of an hourglass. Obviously at first we know the weight, and as the grains begin to fall it decreases by the amount of mass in free fall. However I ran into a problem when the grains begin to hit the bottom. It's impossible...

[Split off from this thread] I think that the force is always repulsive. I think that an electron would have to travel faster than c for it to become attractive.

Do separate instances of virtual pair production interact with each other. Say you have a virtual pair production of an electron and a positron; they separate and then come back together. What happens in the event that there is another occurrence of a virtual electron/positron pair production...

Hi buddies. I recently finished my quantum mechanics course, however, I would like to know the solution of this exercise because i couldn´t solve it on my last exam, and i would like to take this doubt off. An operator ##F## describing the interaction of two spin ##\frac{1}{2}## particles has...

Homework Statement Two boxes of volume V sharing a common wall with a hole of ΔA. Both boxes have gas at T. At t =0s there are N1(0) at one box at time t and N2(0) particles in the other box.The particles from box 1 leak into box 2 through the hole and vice versa. a. obtain two differential...

Homework Statement For six indistinguishable particles obeyed Fermi Dirac statistics where multiplicity, Ω = 162, g = 3 (degeneracy), U = 7 a. Find the total number of macro states. Answer in book: 8. Idk why b. Calculate the thermodynamic probability, W of each macro state. d. Find the...

Homework Statement a. Find macro states of 4 particles among two energy level one of which is twofold degenerate. SOLVED b. Find the thermodynamic probability of each macrostate for indistinguishable particles. SOLVED c. ------------------distinguishabled problems (need help) d. the assembly...

I have a question that I didn't see covered in any book that I read in QFT (I read so far Srednicki which I finished and Peskin and Schroeder which I haven't finished), can the vacuum generate an infinite number of real particles? How do we generate real particles from virtual particles? Is...

Homework Statement "A model system consists of N identical ”boxes” (e.g. quantum wells, atoms), each box with only two quantum levels, energies E0 = 0 and E1 = ε What is the number of microstates corresponding to the macrostate with total energy Mε?" The Attempt at a Solution I've done...

How would two rapidly approaching slits appear to a particle? Would they appear fuzzy or even indistinguishable?

Question: There is a large parallel beam of incoming particles with mass m and uniform velocity v0 (v0≪c) in the presence of a gravitational field of a (spherical) planet with mass M and radius R. (without GR) The question is what fraction of the particles will eventually arrive at the planet...

Hello again, Am facing a difficulty, the question is that , Is energy and momentum conserved for a particle in an infinite square well, at the boundary i.e, at x=a, where the potential suffers an infinite discontinuity?? V=0 for -a<=x<=a V=infinite else-where Thanks in...

Why does a large number of identical particles randomly distributed produce a diffraction pattern same as that of a single particle?

Homework Statement Show that for a two spin 1/2 particle system, the expectation value is \langle S_{z1} S_{n2} \rangle = -\frac{\hbar^2}{4}\cos \theta when the system is prepared to be in the singlet state...

I am looking to correct my understanding about the relative abundance of particles and antiparticles created before the two periods of annihilation: (1) protons/neutrons and anti-protons/anti-neutrons, and (2) electrons and positrons. In a previous thread...

I would like to ask your opinions on what would happen if you had a liquid containing charged particles and then applied a sinusoidal magnetic field? 1. would the particles move in one direction and when the current changes direction then move in the other direction? 2. would there be a...

I start with the spatially flat FRW metric in conformal co-ordinates: $$ds^2=a^2(\eta)(d\eta^2-dx^2-dy^2-dz^2)$$ This metric has the following non-zero Christoffel symbols: \begin{eqnarray*} \Gamma^0_{\alpha \beta} &=& \frac{\dot{a}}{a} \delta_{\alpha \beta} \\ \Gamma^i_{0j} &=& \Gamma^i_{j0} =...

When electrons of high energy fall on metal X rays are produced.What about the metals having large atomic number and showing natural radio activity?Will there be a collision between the electrons and alpha and beta particle? I can not understand this. So please help me.

Just as there are virtual photons, which are in the EM field, are there virtual particles in fields such as the Higgs and Strong?

(I think) I know that massless particles can only exist traveling at c, but I find it somehow counter-intuitive (like many other real things... :D ) Would anyone please be so kind to confirm that, for instance, a gamma photon generated by the radioactive decay of a stationary isotope is already...

Are there any particles which have a neutral electrical charge and are not affected by the weak or strong nuclear force? Thank you for your time and please excuse me if I'm being very ignorant!

In what cosmological era did particles get mass? And why did they not have mass before this?

At the LHC, particles are accelerated at near light speed to produce heavier particles in the collision E=mc2. Are the resulting particles in the collision produce the same fundamental atomic particles (electron, neutron, proton). What are the the chances of producing the same elementary...

Hi. I'm a first year Engineering student at QUT here in Brisbane. My problem is I come up with all these great ideas but lack the confidence and skills to carry them through to realization. I am currently taking 6 months deferment from my degree due to the difficulty of the maths. I have this...

in simpleton's terms, a tokomak magnetically confines a circulating plasma. I assume the plasma circulates for the same reason that electric current flows in the presence of a changing magnetic field. By looking at the design of a tokomak, I would guess the donut magnets are activated...

Have we ever observed or created atoms with nuclei made up of charmed and strange quarks, surrounded by a muon "cloud" or "shell"? Or perhaps an atom with a top-and-bottom-quark-nucleus and a tau particle orbiting it?

Homework Statement Diagrams (a) to (c) show a magnetic field of flux density 0.2 T directed perpendicularly into the paper. In each of (a) and (b) a conductor of length 0.3 m is entirely within the field and is carrying a current of 4 A in the plane of the paper. In (c) an electron is moving in...

From the elementary particles that science has been able to identify until now, are there any that appear to be useless, at least as far as we know? Or do all the identified particles play a role in the grand scheme of the universe?

Just something, probably obvious, that I want to be sure about, please confirm or correct the following: If we have 2 (or n) particles, they are a system only if there are internal forces between them? So, no internal forces implies forces on one won't affect the other... If particles are a...

Homework Statement 1000 neutral spinless particles are confined in a one-dimensional box of length 100 nm. At a given instant of time, if 100 of these particles have energy 4ε0 and the remaining 900 have energy 225ε0, then the number of particles in the left half of the box will be...

Hi all, This question is similar to a question asked previously, but slightly different. I understand that there have now been attempts to extend the Broglie-Bohm, or Pilot Wave, interpretation of QM to QFT. I'm a layman, but if I understand correctly, the standard method for computing the...

Hello everyone, Can atomic or subatomic neutral composite particles that consist charged particles emit cherenkov radiation if they are polarised strongly enough (and are fast enough)?

This is a restatement of a question I have been pondering whilst helping my daughter with GCSE physics. My previous post didn't get me the closure I was after so am trying again. I have three different GCSE textbooks. All three have a simple section on the kinetic theory of particles in...

I was thinking about entanglement today and found myself struggling to envision entanglement and relativity working together. If I send entangled electrons out in opposite directions, their states are not determined until one of them is observed. I know that. What if one of them passes...

One of the possible decay modes of the neutral kaon is ## K^0 \rightarrow \pi^+ + \pi^- ## The rest masses of the K0 and pion are 498 MeV/c2 and 135 MeV/c2, respectively. In 2-dimensions (xz-plane), if the kaon has an initial momentum of 2000 MeV/c in the z direction, what is the momentum of...

So during a particle physics lecture, the lecturer used Heisenberg's uncertainty principle to set a lower limit on the KE of the quarks bound in a proton (given the mass,size of proton and the mass of u/d quarks), which is of the order of 100 MeV, while the mass of quarks is about several...