Confusion Definition and 1000 Threads

I am a bit confused about how kets in dirac notation are working. I read on wikipedia, that kets are linear, so |a*Φ>=a*|Φ>. Also I read (https://ocw.mit.edu/courses/physics/8-05-quantum-physics-ii-fall-2013/lecture-notes/MIT8_05F13_Chap_04.pdf) that this is not true for the position state ket (...

Hi All Have a look at the following discussion about QM: Its long so I do not expect too many people to watch it in its entirety. But it does show confusion about QM even amongst educated people, and the physicist involved IMHO seemed a bit 'confused' himself. You can easily see how the...

https://en.m.wikipedia.org/wiki/Schrödinger_equation "Two-slit diffraction is a famous example of the strange behaviors that waves regularly display, that are not intuitively associated with particles. The overlapping waves from the two slits cancel each other out in some locations, and...

Here, the correct options are A,D. Solution: I got A as answer as ∫ B.dl=µI. But, the answer to the question says that it is a solenoid and therefore Bx=0 for point P. Here I'm a bit confused. I know this system resembles a solenoid in some ways, then By must have some finite value, but...

I've been attempting to run through some quantum mechanics and I've seen something extremely odd, and I just can't spot my mistake. I know the relationships: ##p = \frac{h}{\lambda}## and ##E = hf##. I also know the relationship ##E = \frac{p^2}{2m}##. I tried to show using the energy-momentum...

--no explanation as conceptual error--

What does "F(r,θ) = 0" mean here?

I'm not sure as to why my working is incorrect. When the sign on a_x is postive, i get t = \frac{R\omega_0}{3\mu_kg} which would give the correct value for distance if plugged into the kinematic equation. However, I'm not sure why a_x would be positive though since the friction force is pointing...

According to the theory, every mass has a Schwarzschild radius associated. Any object whose radius is smaller than its Schwarzschild radius is called a black hole. So in principle is possible to create mini-black holes, it is just a fact of matter condensed. Those mini black holes have their...

When we calculate the curl of magnetic field, that is the curl of Biot-Savart equation for magnetic field. Please consider these . The working of last equation $$ \nabla \times \mathbf {B} = \frac...

ik that i have to add the positive and negative ions but the cross section (surface) confuses me how do i resolve this?

Suppose there are two clocks. Clock B is moving with a speed of ##v## relative to clock A. Then clock A is moving with a speed of ##-v## relative to clock B. Let ##t_0## be the time interval for two events in the framework of clock A, while ##t## be the time interval for the same two events in...

If we have a plane wave, usually in Relativity notation it is written as ##A^\alpha = a^\alpha \exp(i x_\alpha k^\alpha)##. (I know we need to take the real part in the end). In cartesian coordinates, and two dimensions say, that ##x_\alpha k^\alpha## would be ##x^\alpha k_\alpha = x k_x + y...

[SIZE=14px][FONT=Noto Sans]So I was trying to understand Horner's method. I understand that you can take a polynomial and factor out the x's and re write it as multiple linear functions recursively plugged into each other and that this makes evaluating a polynomial easier because you just...

$$1 - \Omega_{tot} = \Omega_κ = \frac{-κc^2}{R_0^2H_0^2} $$ For ##\Omega_κ=-0.0438## we get a some value for ##R_0##. This ##R_0## is the radius of the observable universe right ? Not the universe ?

Hello, I am simulating the input impedance of a high-pass filter with the output voltage of the filter input to the non-inverting pin of an op amp. I'm confused as to why the input impedance can possibly dip below the resistance of the high-pass filter resistor. Please see the following circuit...

When first introduced to the concept of the ecliptic, I was under the impression that the ecliptic was the path taken by the Sun across the sky over the course of a day. That is to say, the rising in the east and setting in the west, due to the Earth's (daily) rotation from west to east. (Image...

I was looking into neutrinos and found that a man named Ettore Majorana proposed neutrinos and antineutrinos are the same thing. If this could be true, antineutrinos emitted during double beta decay could annihilate one another and vanish. However, this would violate lepton number conservation...

I am admittedly entirely confused as to where to start, sorry. This is the diagram I'm given that fits with the rA + rB. If rB is 47.0 degrees above the x-axis normally, it would be the same counter-clockwise here, right? Then 180 - 47 = 133 degrees for the clockwise angle. But now I'm stuck...

Consider a continuous charge distribution in volume ##V'##. Draw a closed surface ##S## inside the volume ##V'##. ___________________________________________________________________________ Consider the following multiple integral: ##\displaystyle B= \iint_S \Biggl( \iiint_{V'}...

Hi there! I have what I hope is a relatively straightforward question regarding Faraday's law and motional emf, but its been causing me to scratch my head for quite a while. Consider the diagram attached to this post (source is linked at the bottom). Assume that all of the wires and the rod are...

If this belongs in classical physics, please move it there. But it seems like the kind of question chemistry people would know so I'm putting it here. I was reading a textbook on chemical thermodynamics, and it says to raise the partial molar Gibbs free energy of n moles a substance from...

Hi all, Just had a look at the 2016 paper by Wang, Zhu, and Unruh, "How the huge energy of quantum vacuum gravitates to drive the slow accelerating expansion of the Universe," Qingdi Wang, Zhen Zhu, and William G. Unruh, Phys. Rev. D 95, 103504 – Published 11 May 2017 The paper states...

I will refer to the spin example outlined in the opening chapters of the Theoretical minimum. Suppose we prepare a spin with a z component of +1. If we rotate the apparatus about 180 degrees, the ‘classical component’ of the prepared spin vector along the new axis of the detector is -1, so...

Problem Statement: Given in the "Attempt at a solution section". Relevant Equations: Given in the "Attempt at a solution section". Problem Statement: Given in the "Attempt at a solution section". Relevant Equations: Given in the "Attempt at a solution section". I am having some serious...

I will refer to the example given in 'On the electrodynamics of moving bodies' concerning a rod moving in a coordinate system, in which a beam of light is sent from one end of the rod to the other and is then reflected back. Usually when calculating relative velocities, we may simply consider...

Since my major is not physics. My QM knowledge is not pretty good (Mostly self study). I am sorry if this question was asked multiple times in the forum. I've learned that wavefunction can be written as a linear combination of eigenfunctions due to completeness property. If an electron is...

So, Heavside's method confused me, I mean, but we can't divide by zero, can we? So, my mind sees it as cheating, and to multiply both sides by zero to cancel zeros, and for the example above(from Thomas Calulus), when x = 1, before you multiply by x-1(=0), you get: 2/0=A/0+B/-1+c/-2, and I think...

Hi Im current in last year of HND mechanical (100% distinction so far) and have HNC in general engineering (100% distinction). Im better at the research and piratical bad at exams (diffucult reading and writing and slow comperhention skills and expression using writting what i want to...

I'm a mathematician with a longstanding interest in physics, and I've recently been enjoying reading and thinking about Arnold Neumaier's thermal interpretation, including some threads on this forum. There's something that's still confusing me, though, and I'm hoping someone here can clear it...

Hi, I'm currently learning QC with Nielsen's QCQI. I've written a program in Matlab following the factoring algorithm in page 233 and 235. I run the program for factoring 15, 18, and 25. I got the proper results several times, but I also got error reports sometime, especially when factoring 18...

Hey there! I’ve been thinking about the Born rule recently and whether it can be derived from the other postulates from QM. I’ve done a bunch of google searching, across PF, stackexchange and the arxiv, but most of it has felt a little opaque, particularly on whether anything has been...

Hi! I am studying Shankar's "Principles of QM" and the first chapter is all about linear algebra with Dirac's notation and I have reached the section "The Characteristic Equation and the Solution to the Eigenvalue Problem" which says that starting from the eigenvalue problem and equation 1.8.3...

Solution: ##\frac{\partial z}{\partial x} = yx^{y -1}+1## ##\frac{\partial z}{\partial t} =\frac{\partial z}{\partial x}\frac{\partial x}{\partial t}+\frac{\partial z}{\partial y}\frac{\partial y}{\partial t}## ##\frac{\partial z}{\partial t} = (\frac{yx^{y-1} + 1}{2\sqrt{s+t}}) +...

In "Sheldon Axler's Linear Algebra Done Right, 3rd edition", on page 21 "internal direct sum", or direct sum as the author uses, is defined as such: Following that there is a statement, titled "Condition for a direct sum" on page 23, that specifies the condition for a sum of subspaces to be...

Equations: Question: Using the equation for t' I got the answer -0.00000499756s (Wrong anyway) As we know the values: v = 0.67c m/s x = 3900 m t = 0.000005 s Also how can time be negative? Does this mean that event 2 happened before the first event when t = 0?

Before I modeled it, I thought the current would move in a figure 8 due to the battery on the right still loading the current. Then I thought of how the battery on the left would counteract that current. I am still not sure what is going on here. Is it kind of like a short circuit where the...

I'm revising for my condensed matter exam, and I've never understood the point group notation, in particular of the 32 crystallographic point groups, so let me try and explain what I understand of it and point out where my confusion lies. Please point out any other misunderstandings I have. We...

Hello. As I understand it, Kepler's 2nd law of planetary motion can be explained through conservation of energy or conservation of angular momentum. I am having trouble with the conservation of energy explanation. We know that the sum of potential and kinetic energy of a planet in orbit around...

Hi! $$\lim_{n \to \infty }\int_{0}^{n}\frac{dx}{1+n^{2}\cos^{2}x }$$ I found to solution on the internet but I didn't understood it 100%. First, it says that the function under integral has period $pi$.Why pi ? I know that cos function has period $2kpi$ Consequence: $\int_{0}^{k\pi...

Hello, I am an undergrad and am in an introductory level astrophysics course. I have a bit of confusion that I didn't know where to get help from so I made an account here. Please let me know if I miss some common etiquette or something... I don't understand how the slingshot maneuver...

Assume we have a diode . We connenct the negative terminal of the battery(anode) to the n type region and we connect the positive terminal of the battery to the p type region of the battery.The net force forces electrons to start flowing from the n type region to the p type region.As long as we...

1) I know that the binding energy is the energy that holds a nucleus together ( which equals to the mass defect E = mc2 ). But what does it mean when we are talking about binding energy of an electron ( eg. binding energy = -Z2R/n2 ? ). Some website saying that " binding energy = - ionization...

Hi, i am currently in class 10 and have a lot of interest in physics(mostly quantum ,particle and astrophysics) and want to pursue it further but climate change occurring vigorously around us worries me a lot .what should i do ? pursue physics or pursue a course like engineering which will help...

Dear all, I've been reading and got confused of the concept below have two questions question 1) For <ψ|HA|ψ> = <Hψ|A|ψ>, why does the Hamiltonian operator acting on the bra state and <ψ|AH|ψ> in this configuration it will act on the ket state? question 2) what does it mean for H|ψ> = |Hψ>...

Hello, I am an undergrad currently trying to understand General Relativity. I am reading Sean Carroll's Spacetime and Geometry and I understand the physics (to a certain degree) but I am having trouble understanding the notation used as well as the ideas for tensors, dual vectors and the...

Hey there! I've recently been looking at calculating amplitudes, densities of states and scattering cross sections in QFT, but am having a little bit of trouble with the exact form of the cross section - particularly with factors of ##2E## for the energies of the incoming and outgoing particles...

The answer says B, it does makes sense, but why D is regarded as incorrect. If the Elastic Potential energy when loading is the area under the loading curve, so why not with the unloading?

I understand that waves are function of space and time in nature, so E(x,t) will be fundamental description of a wave. I notice that often people denote a wave as E(t) for instance, an envelop function of a pulse. For this case, E is an oscillation at a fixed spatial point x? So that the point x...