Particle Definition and 1000 Threads

As you no doubt have heard countless times, GR's prediction that a black hole should collapse to zero size is considered problematic because it would imply infinite density, which isn't physically possible. And yet, over on the other side in QM, electrons seem to be considered pointlike...

link: "Particle Creation by Black Holes", S. Hawking Hello all, I just want to know the meaning of the text followed by equotation 1.2. Especially if the flat or asymptotic flat region could interpreted for Minkowski-Spacetime at an arbitary Point in M or just at the positive/negative...

As above: there was, I believe some kind of particle resonance experiment: it doesn't work when the level of resonating particles was the same, but raising part of it up by 20-30m (60-90ft) does the job. Could anyone remind me what it was? Thx.

Hi, I am stuck with the following task I have developed a Taylor expansion for ##L[\gamma]=\sqrt{c^2-v^2}## up to the third order for the position ##a=0##, for this I have rewritten ##L[\gamma]## as follows: $$L[\gamma]=\sqrt{c^2-v^2}=c \sqrt{1-\frac{v^2}{c^2}}$$ Then I did the following...

Hi all, I'm a european about to have to start his Master's thesis in particle physics. I might have the opportunity to choose between SLAC, Brookhaven lab and Purdue university. Purdue would offer me a more standard academic outlook, with the prof even mentioning a probable phd opportunity after...

Using the above equations for potential and kinetic energy, I figured that potential energy would be twice kinetic energy where ##kx^2=2mv^2##. Solving this equation for v (where ##k=mw^2##), we get ##v=wx/sqrt 2## Counting one complete cycle of the function on a graphing calculator, I found...

In the following thread: https://www.physicsforums.com/threads/particle-movement-in-quantum-mechanics.1054807/ the discussion established/confirmed that the matter of a particle’s continuity of movement in Quantum Mechanics QM is not a scientific question in QM, refer to PeroK post # 6...

I found some excellent videos from Berkeley on what QFT is. https://www.youtube.com/@hitoshimurayama2746 The view is that QFT is simply a multi-particle ordinary QM. The videos give the full details, so I won't say anything else except to mention some highlights. Particle creation, Compton...

Newtonian gravity is the force law such that for any mass M, the circular orbit of any test particle m at a distance equal to the Compton length of M has the same areal speed, independent of M and m. I wonder, have you seen this sort of definition online in the literature? I guess that...

Adrian Cho, who is always excellent, has a very good article on the recent difficulties Fermilab has been having: https://www.science.org/content/article/trouble-and-strife-deepen-famed-u-s-particle-physics-lab A little background. In 2007, the current contractor received the DOE contract to...

For this problem, My solution is However, the my answer for ##\Delta x## is not correct. The correct answer is ##\Delta x = 0.18a##. Does someone please know what I have done wrong? Kind wishes

So I was always wondering what a gluon computer (a computer using gluons instead of electrons or photons for the computing medium) would be like. There is absolutely NO literature anywhere online for it and the only mention is a brief card (with no description) in a sci-fi board game. People...

When looking into how particles decay, it seems that it will happen if there exists an interaction between the initial and final state, and if the final state has lower potential energy than the initial. (i.e. turning mass into kinetic energy) If this is true, how does a gluon turn into a quark...

Is there only one type of elementary charge? The type of elemental charge that appears on particles such as electron, proton, etc. It is well known. Could there be another different type that we don't know yet?

I appreciate Sabine Hossenfelder's latest video, and thought I would assemble some references. There's a mix of particle physics and cosmology topics. In general, the coincidences mentioned are mainstream topics in cosmology, whereas the particle physics coincidences are not. 1) Proton/electron...

Ever since High school I've seen this model of the "particle zoo," including in my recently finished particle physics undergrad course, and I can't seem to find where the mass numbers for the neutrino family is coming from! Sure the model has a less than sign, but from what I understand all...

According to Einstein's formula, energy is generated when mass is obtained or lost. What does losing or gaining mass mean for an atom or particle valence? It's simply because of the formula I don't want this kind of answer I want. What does it mean for an atom or particle to lose or gain mass...

I just started studying Quantum physics and i'm learning about Comptonspreading and I have this question in my book that I don't completely understand So if an electron is standing still, then it gets hit by a photon moving in a straight line into the electron. The photon then bounces off the...

solution is here; I just need to understand this part ##14.7 = -14.7 =9.8T##... why initial velocity upwards is a negative value? or i am interpreting it wrongly. ........... In my reasoning, ##v=u+at## ##0=14.7 + (-9.8)t## ## t_1=1.5## in reverse direction, from top to start point ##T##...

Since the ball will follow a parabolic trajectory , i threw it into the coordinate plane with particle starting from the origin . $$y= kx^2$$ Differentiating wrt ##t## : $$ gt=2ku^2 t\implies u=\sqrt{\frac{g}{2k}}$$ where $$k=\frac{\sin\theta}{R\cos^2\theta}$$ Now , final speed when it reached...

Hi, i was wondering why a W Boson must always decay into a quark anti quark pair of the same generation. Why can it not for example decay into an up ant anti strange pair?

A wave pulse moves along a stretched rope in the direction shown. Which diagram shows the variation with time t of the displacement s of the particle P in the rope? A B C D my answer was c because i thought that the particle would move in the same way the wave was coming...

TL;DR Summary: Looking for help on a Intro to QM Problem Hi All, THIS IS A GRADED PIECE OF WORK AT MY UNIVERSITY PLEASE DO NOT JUST GIVE ME THE ANSWER , I have made this post to see if what i've calculated seems reasonable, it sounds unlikely as 0.4 - 0.5L is in the middle of the well. The...

Quarks and electrons have clear electric polarity. So, can we assume that an electric source as electromagnetic is needed to create those kinds of particles?

Hi guys it's me again. I need help with this exercise which reads: a particle of mass m, placed in an infinite rectangular one-dimensional potential well that confines it in the segment between ##x = -\frac{a}{2} and x=\frac{a}{2}##, is at instant ##t=0## in the state: ##|\psi \rangle =...

This is from an old exam. The velocity of a particle moving along a straight line is v = 4 + 0.5 t. What is the instantaneous acceleration at t=2? The solution is supposedly 2 because a = dv/dt = t. But I thought dv/dt here would be 0.5. What am I missing? Thanks.

Hi guys i have this exercise: A particle of mass m, confined in the segment -a/2 < x < a/2 by a one-dimensional infinite potential well, is in a state represented by the wave function: 1. Determine the constant N from the normalization condition. To do this, I have to integral the square...

When I submitted it, this answer was incorrect.

Why do we say that wave amplitude tells us where we are likely to find the particle versus where we are likely to find the wave from the particle? Isn't the later a more accurate description of the QM math?

I know the mass of J/ψ to be 3097 mev and the mass of phi to be 1018 mev. I know that J/ψ decays to electron and positron 5% of the time. I also know the full width of j/psi to be 0.092mev and that the phi meson lives 50 times longer than J/ψ . My professor claims that if I am given that info...

Hi, Unfortunately, I am not quite sure whether I have solved/plotted the following task correctly I started by resolving the expression ##\phi=2 \pi t## to t so that I can represent ##\rho(t)## with ##\rho(\phi)## The vector ##\vec{e}_r## was written in my lecture as follows...

Question image: The question should be solved by conservation of mechanical energy.( I assume surface density##\sigma## and acceleration due to gravity##g=const.##)Therefore: $$PE_i+KE_i=PE_f+KE_f$$ The axis of rotation ##PQ## is line of zero potential. Then 1) ##PE_i=\int Fdy## Since...

I calculate 4.8x10(^10) particles /kg of sand in the sample. Do you find the same ? Is my solution correct ? How many particles do you find ? Thanks in advance !

I'm following the derivation in Lancaster and Blundell. First, the Lagrangian for the free particle is ##L=-\frac {mc^2} {\gamma}## and the action ##S=\int -\frac {mc^2} {\gamma} \, dt##. Then, EM is "turned on" with the potential energy ##-qA_{\mu}dx^{\mu}##. Then, they say, the action becomes...

Hey, I've been working on this for a couple hours, and still no luck. Since the force in the radial direction is zero, I set r'' = rθ'^2. Then since Fθ = m r' θ' and, since it's in polar coordinates, Fθ = m(2r'θ' + rθ''). Setting these two equal, I get: -r'θ' = rθ'' At this point, I'm...

Attaching the image of the problem as an image. Somehow text is not copied from the book. Somehow, I can't imagine the picture in my head. We can do it in 2D plane. I know, it mentions the solution, but need to see the drawing, otherwise, my logic fails. I thought that maybe, first half space...

edit: I don't know why my latex isn't rendering, any help would be appreciated. Edit 2: The question was due to a misunderstanding I had, I thought integrating instantaneous velocity would give me average velocity. I have attached what I have tried so far. I had a doubt. Can you calculate the...

Hi, I have problems with the task part b and g To solve the task, we have received the following information Task b First, I wrote down what the state ##\psi## looks like $$\psi=\frac{1}{\sqrt{N}} \sum\limits_{k}^{} \psi_k$$ $$\psi=\frac{1}{\sqrt{N}} \sum\limits_{k}^{} \frac{1}{\sqrt{N}}...

For this, They say internal energy is the sum of the all the mechanical energies of each particle in within the thermodynamic system, however, they then define internal energy differently using the average mechanical energy for all particles within the system (Pink equation). Does someone...

I am only interested in the initial equilibrium conditions, and I am struggling to convince myself whether that should correspond to the equality of chemical potentials for H2 or an equality of temperatures as well. My work is as below: We take both gases as simple ideal (this is only relevant...

Assume spin 1/2 particle So the spin operator gives +/- hbar/2 eg. S |n+> = +/- hbar/2 |n+> But S= s(s+1) hbar = sqrt(3)/2 hbar So I'm off by a factor of sqrt(3). I suspect I am missing something fundamental about my understanding of spin. My apologies and thanks in advance.

Assume there is a force (vector field) on the space .....does the effect of this field on the particle(the change of momentum) at some position depend on the speed at that position? And is it related to the time interval dt the particle experiences this force ? Can i say dt=dx/v? And is that...

From the picture, the particle experiences upwards force. But how to determine the direction of motion? I think there are two possibilities: if the particle is positive, it moves from Q to P and if it is negative it moves from P to Q. Thanks

For this, The solution to (a)(i) is 0 ft/s. However I got -4 ft/s. The formula I used was, ##v_{avg} = \frac{s_f - s_i}{t_f - t_i}## ##v_{avg} = \frac{\frac{1}{2}t^2_f - 6t_f + 23 - \frac{1}{2}t^2_i - 6t_i + 23}{t_f - t_i}## ##v_{avg} = \frac{ \frac{1}{2}(t^2_f - t^2_i) - 6(t_f - t_i)}{t_f -...

I keep getting particle lost error even though there were no hole in the lattice. Can someone identify any mistake in my code?

in https://www.physicsforums.com/threads/black-holes-to-explode-due-to-evaporation.1051054/page-2#post-6869765 there was a discussion about where the mass inside a black hole is located. according to general relativity it is located in an infinite small point, which causes spacetime to be...

hello i would to get some help with my homework. 1. true 2. i dont know 3. true 4. i dont know 5, false 6. i dont know about 2,4,6 i really have know idea what to think I really appreciate help

A) I just did what it said to do: $$\sin\left(4x_{1}\right)=1\implies x_{1}=\frac{\arcsin\left(1\right)}{4}\ m=\frac{\pi}{8}\ m\approx 0.392699081699\ m$$ B) I modified the method from an example from the lecture the other week: $$U\left(x\right)=-\int...

I understand how a massive, electrically charged spinning ball would have both angular momentum and a magnetic dipole, and i can see how the Stern–Gerlach experiment shows that the magnetic dipole of an electron is quantized. What kind of experiment demonstrates a connection between electron...