Particles Definition and 1000 Threads

Homework Statement Massive particles are relativistic when their kinetic energy is comparable to or greater than the energy corresponding to their rest mass. (This condition implies that their speed is close to the speed of light.) But what does the comparable mean? Is it that the particle...

It seems that historical events are the same every day. If the future affected the past wouldn't history books change everyday by themselves? Is it possible that history does actually change but we don't realize it because our memories change too?

I understand that we can create entangled particles in the lab. But how many (non-locally) entangled particles (such as photons/polarisation or electrons/spin) exist in free nature?

For example, general relativity relates the behavior of gravity the the deformation of spadetime. But does quantum mechanics explain why particles behave the way they do? Or does it only explain how processes such as entanglement work not why they occur.

I was wondering if there is a current hypothesis about the quantities of which matter particles were created? I'm not completely au fait with the standard model, but I've seen the picture...

Homework Statement A particle of mass 5.0kg travels initially with a velocity of 8.0mˆı and then interacts with a particle of mass 6.0kg which was initially at rest. After the interaction the 5.0kg mass travels at a speed of 4.0m/s along a direction which makes an angle of 53◦ with the x-axis...

Hello! It is sometimes useful to find the average energy of a certain number N of particles contained in a box of volume V. In order to find this quantity, the total energy is required and then divided by N. The result is E_{average} = \displaystyle \frac{1}{N} \sum_{n = 1}^{N} \left| a_n...

Im having trouble with my thought process for spin states of a system of two electrons Using Total Spin 'S' and Total spin mag quantum numbers 'MS' as state ket |S MS> My textbook states... " Three Symmetric Spin states Triplet spin stats for twin identical spin -1/2 particles | Up Up> = |S...

Global phase invariance has been identified with the conservation of electric charge. Local phase invariance via the coupling of the wave function/field with the EM four-vector has been identified with charged particles interacting with the EM field. Am I correct in assuming that, except for...

I know some people here hate the subject of virtual particles. So I will try to narrow my questions. Granted, virtual particles are just attempts to describe the math and are not real in and of themselves. But there seem to be a couple of different kinds of virtual particles (in the math)...

I've recently begun studying thermal effects. I learned that thermal energy could be transferred within an object through conduction and from a distant object through radiation. (let me know if I'm wrong here) I also learned that when matter is heated, it's particles begin to vibrate, move apart...

These are just a few quick and simple questions. When are particles in a quantum state? Are they always in a quantum state in-between interactions, or once interacted with are they never in a quantum state again? At the instant of the big bang was everything in a quantum state? If so, what...

I'm not sure if I posted this in the right category, it's something that came up just after the quantum mechanics section so I just chose this one. I've come across something that I simply can not find an answer for on my own. I'm taking Modern Physics course and the last chapter is some...

Perhaps someone can show me some simple math showing two states in superposition and entanglement so I can see how entanglement relates to superposition. Thanks.

Homework Statement 2-body, COM frame collision a+b ---> c+d E = Ea+Eb = Ec+Ed Show that dE/dPf = Vc+Vd Show that the answer is the same when the velocities are relativistic I don''t know how to work out the relativistic aspect of the question. Homework EquationsThe Attempt at a Solution E =...

Homework Statement Two particle of mass m each are tied at the ends of a light string of length 2a. The whole system is kept on a frictionless horizontal surface with the string held tight so that each mass is at a distance ‘a’ from the center P (as shown in the figure). Now, the mid-point of...

In the following, I want to consider both photons in a sharply focussed, monochromatic beam of light (''type P'') and electrons in an electron beam (''type E'') on the same footing. In the following, X is either P or E. If we only concentrate on the internal degrees of freedom, both kinds of...

It seems that the most popular hypothesis is that dark matter consists of WIMPs. Can the existing data be described with sterile particles rather than ones that interact through the weak force? Is the only reason to prefer WIMPs that they are predicted by SUSY? (To me, as a nonspecialist, SUSY...

The charged particles of a plasma are either strongly repelled or attracted to one another. Am I correct in saying that they do a "giant slalom" around one another? And does this mean that the transfer of momentum in a collision is much smaller than in a neutral gas where the atoms/molecules...

If light of certain wavelength falls on two particles say electron and a neutron(isolated) then since they are absorbing the same amount of energy their kinetic energy must be same. But using the formula: $$ \lambda = \frac{h}{\sqrt{2mE}} $$ we get $$ E = \frac{h^2}{2m \lambda^2}$$ which states...

Entangled particles give no interference. What happens in the Fraunhofer approximation when the source of entangled pairs is far away? If it depends on distance what about the apparent collapse?

I'm reading Goldstein's "Classical Mechanics", first chapter, and am confused about what's going on in equations of forces and work in systems of particles. For example, Goldstein calculates work done by all the forces, external and internal, in evolving the system from state ##1## to state...

Homework Statement A beam of identical neutral particles with spin 1/2 travels along the y-axis. The beam passes through a series of two Stern-Gerlach spin analyzing magnets, each of which is designed to analyze the spin projection along the z-axis. The first Stern-Gerlach analyzer only allows...

I'd like to discuss the question in the title, following up on my remark quoted below. Note that I don't want to repeat the discussion in https://www.physicsforums.com/threads/tracks-in-particle-detectors-and-quantum-paths.758778 so maybe reread that one first! The traditional analysis is...

As far as I know both mass and energy affects space-time. Mass creates a "sphere like zone of distortion", the space-time is less altered as we move away from the center. Photons on the other hand alter the space-time rather wave like, along the propagation trajectory and not "locally". Could...

In page 2 of Pathria's textbook on 'Statistical Mechanics,' it is mentioned that Consider the total energy ##E## of the system. If the particles comprising the system could be regarded as noninteracting, the total energy ##E## would be equal to the sum of the energies ##\epsilon_i## of the...

We know electrons can act as waves because of Young's Double split experiment, but what evidence is there to suggest they are particles?

It says everywhere that particle decay is not the only thing that creates entangled particles. "Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described...

Homework Statement Alright, this problem has been driving me into a confused rage. The wave is moving in an upward direction so particle A should be moving up as well, right? But every single website I've used to study claims that it's moving in a downward direction. How? Homework...

I am told that if an electric field is strong enough that it can polarize the vacuum enough to created positrons and electrons. Also, if quarks are separated enough, then the potential energy creates other quarks. My question is can the reverse happen, are particles ever absorbed back into a...

In this thread, I want to discuss the implications of quantum field theory for the interpretation of quantum mechanics. To set the stage I'll import in the next few posts a number of posts from other threads. The latest of these is the following: Only if it is the sole particle in the whole...

Does the gravitational force of different planets affect it? I know about the higgs boson and so is that what gives a particle mass?

Each particle has a wave associated to it according to the principle of wave-particle duality. Between two waves there is a phase difference. What is this phase difference in the case of entangled particles? 0 degrees? 90 degrees? 180 degrees? Somewhere in between?

Homework Statement [SIZE=13px][FONT=Helvetica]Q: A 3.000u object moving to the right through a laboratory at 0.8c collides with a 4.000u object to the left of the laboratory at 0.6c. Afterward, there are two objects, one of which is a 6.000u mass at rest. A) what are the mass and speed of the...

Hello, I'm doing some online research on fluid flow in waste water treatment. One of the problem I'm trying to find information about is how can visible particulate matter be separated within a liquid. I saw the following picture: What fluid concepts are going here that allow the grit to...

The mass of a particle will increase as its velocity increases according to special relativity. This has been confirmed in countless experiments in which particle accelerators accelerate charged particles. What type of experiments have confirmed this for uncharged particles? Thanks in advance.

The following is taken from page 13 of Peskin and Schroeder. Any relativistic process cannot be assumed to be explained in terms of a single particle, since ##E=mc^{2}## allows for the creation of particle-antiparticle pairs. Even when there is not enough energy for pair creation, multiparticle...

If a metric admits a Killing vector field ##V ## it is possible to define conserved quantities: ## V^{\mu} u_{\mu}=const## where ## u^{\mu}## is the 4 velocity of a particle. For example, Schwarzschild metric admits a timelike Killing vector field. This means that the quantity ##g_{\mu 0}...

Are there any particles known in the Physics world with an either positive or negative charge that can be viewed by the human eye under LED light illumination and have an attraction/repulsion to magnetism?

Homework Statement A particle of mass m and initial velocity v0 collides elastically with a particle of unknown mass M coming from the opposite direction as shown in the left-hand sketch on the next page. After the collision, m has velocity v0/2 at right angles to the incident direction, and M...

I think I have never seen a force equation for massless particles, I wonder if such thing exist or if not why not?

Freon is used every day to reduce temperature by compressing the gas then releasing the pressure. The Question is dose radiation from the sun (witch would be high pressure) steal energy from the objects it comes in contact with in space (witch is low pressure), Thus contribute to the loss of...

[FONT=UICTFontTextStyleBody]Hello, I was curiose as to if it is possible for a virtual particle to appear without its anti-mater/matter counter part. I posted a thread before asking about the existence and untimatly the "realness" of virtual particles. I concluded that they are real from the...

The question is: Which solution listed below is going to have the highest boiling point? A. 1.5 m NaCl B. 1.5 m AgCl C. 2.0 m C6H12O6 D. 2.0 m CaCl2 E. 1.0 m Al2(SO4)3 I chose D (which was right) because in a solution, the more solute particles there is the higher the boiling point (this is...

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...