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The miller indices of the middle plane is $(2,0,0)$ and it's easy to see why it's so but I've read that one should reduce the Miller indices down to lower integers so the miller Indices of this middle plane should be $(1,0,0)$. If that's so why does the author use $(2,0,0)$ to designate the plane?
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A lot of people say that a battery converts chemical energy to electrical energy which is transferred by the charges to components in the circuit (such as bulbs). This analogy doesn't make sense as it implies the current would decrease once it has passed through a component (when we know that current is the same every... |
I'm currently reading Peskin's "An introduction to Quantum Field Theory", but I'm stuck on page 87; I don't understand why he gets such a Bra for the vaccum state of the interacting theory, say $\langle \Omega |$:
$$\langle \Omega | = \lim_{t\rightarrow\infty(1-i\epsilon)} \langle 0 | U(t,t_0)\left(e^{-iE_0(t-t_0)}\lan... |
If there is lab-frame observer with coordinates $(t,x)$ and a uniformly acceletaing observer in $1+1$ dimensional flat Minkowski spacetime with coordinates $(t',x')$, can we analytically relate $(t',x')$ and $(t',x')$ i.e. express $t=t(t',x')$ and $x=x(t',x')$?
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I want to compute the coefficients of the second fundamental form $K$ of a timeslice $\lbrace t=0\rbrace$ in the Kerr metric in Boyer-Lindquist coordinates. I tried to do this via the definition of the second fundamental form, $K(X,Y)=\,^4g(\nabla_X \nu, Y)$ (where $\nu$ is the unit normal of the timeslice), and also v... |
I am interested if the proposed shape of bricks would have impact on stability of walls.I think the cube structure would not absorb so well the lever effect when a possible earthquake moves every upper brick left-right and tries to break the connection with the lower one.Should the variant b) from the picture reinforce... |
I know what modal analysis is, and I know how to conduct one. I can get the eigenvalues and vectors (modes). Not a problem.
However, I am lost at trying to understand the philosophy of what it is.
By that, I mean ...
You take a two mass oscillator, for example (two masses connected by springs). I use either Newtonian ... |
I have a quick question.
Particle in 1D box with length $L$ and wave equation
$$
\psi(x,t=0)=Ax^3(L-x)
$$
If I want to express time evolution do I just add time factor at end like this?
$$
\psi(x,t)=x^3(L-x)e^{-iEt/\hbar}
$$
Or am I suppose to use superposition of wave functions describing particle in a box? Then the t... |
If you were to hold a string at both ends what shape would the string take(in earth's gravity). Obviously this depends on the length of string and the distance you hold the 2 ends apart so let's say that you can only change the distance of the ends from one another on a straight line parallel to the ground. What equati... |
The proton decay rate in the standard $SU(5)$ grand unified theory is given by
$$
\Gamma \sim \left(\frac{g^2}{M_x^2}\right)^2 m_p^5 =\frac{g^4}{M_x^4}m_p^5
$$
Naively we could push up the bound for the decay rate $\Gamma$ arbitrarily high by increasing the mass of the $X$ boson, $M_x$. However, it seems that we set $... |
Imagine discrete orthonormal basis made of infinite set of kets $|\phi_1\rangle , ..., |\phi_n\rangle,...$
Completeness or closure of the basis is given by:
$\sum_{n=1}^{\infty} | \phi_n \rangle \langle \phi_n | = \hat {I}$
(From Zetilli's Quantum mechanics book)
So what I did manage is that the eigenvalues of the oper... |
Why can't two clocks synchronized with signals SLOWER than the speed of light, measure the speed of light in one direction?
I know that it is not possible to measure the speed of light in only one direction, and I understand why two clocks synchronized with light signals are useless. But I realize that I can't explain... |
I am trying to do some error propagation to find the error on polar coordinates starting with cartesian coordinates.
Using the equations found in Hughes and Hase, "Measurements and their Uncertainties", I come up with a final error for the rho value in polar coordinates as:
rho error = $\sqrt{x^2+y^2}\cdot\frac{1}{2}\c... |
I am stuck on the following question:
"Calculate the fraction of the light incident on the surface with an angle less than the critical angle for total internal reflection"
The context of the question is an LED where the refractive index of the semiconductor is 3.40 and the wavelength is 705nm. It also says to assume l... |
Consider a 1d Ising model with no external magnetic field $(h=0)$ and adopt a decimation transformation in which every other spin is traced out.
So the Hamiltonian $H$ is given by
$$H = -J\sum_{(i,j)} s_i s_j$$
where $(i,j)$ corresponds to the nearest neighbors of $i$.
I am trying to sketch the RG flow of this system, ... |
In the Faddeev-Popov procedure one defines the Faddeev-Popov determinant through the formula $$\int {\mathcal{D}\alpha \ } \delta\big[G(A^\alpha)\big]\Delta[A]=1,\tag{1}$$
where $G(A^\alpha)$ is the gauge-fixing condition and $A^\alpha$ is the gauge field $A$ transformed by a finite gauge transformation obtained expone... |
Recently I've encountered a problem stated as follows:
A smooth bowl has the shape of a paraboloid. The equation of the cross-section with the $(x, z)$-plane is $x^2= 2R_Az$, where $R_A$ is the curvature radius at point $A$. One releases at a point with height $z=h$ a point mass with an initial velocity equal to $0$. W... |
I have a series of individual (time) measurements with a certain uncertainty each per measurement, which is the same for all the measurements (±one frame). I have understood that the uncertainty on the arithmetic mean of these measurements will be equal to that same uncertainty of the measurements (±one frame in this c... |
In another post, I was taught that when we are moving (running, for example), radiation (in the form of heat, both from our muscles and friction with the ground) takes away from our momentum. That makes perfect sense and I understand.
I was also taught that heat/radiation is directional.
My question is: since radiation... |
I am having some trouble with the following passage in section 4.2 of vol. I of the Feynman Lectures on Physics:
A very simple weight-lifting is shown in Fig. 4-1. This machine lifts three units "strong". We place three units on one balance pan, and one unit on the other. However, in order to get it actually to work, ... |
In Hartree-Fock method, one is interested in calculating the energy expectation value for a Slater determinant. The problem is separated into an one-electron operator and a two-electron operator.
For a system with two electrons we can write down the one-electron operator $\hat{O}_1 = \hat{h}(1) + \hat{h}(2)$. Where $\h... |
Excerpt:
A very simple weight-lifting is shown in Fig. 4-1. This machine lifts three units "strong". We place three units on one balance pan, and one unit on the other. However, in order to get it actually to work, we must lift a little weight off the left pan. On the other hand, we could lift a one-unit weight by low... |
Excerpt:
Call this reversible machine, Machine A. Suppose this particular reversible machine lifts the three-unit weight a distance X. Then suppose we have another machine, Machine B, which is not necessarily reversible, which also lowers a unit weight a unit distance, but which lifts three units a distance Y. We can ... |
Common sense would suggest that sudden braking is worse than gradual braking.
On the other hand, a basic physics-based analysis would seem to indicate that the two cases would cause the same wear to the brake pads. After all, if a car (or bike, etc.) travelling at speed $v$ needs to come to a stop, then the energy dis... |
Imagine a sphere of radius $R$, centred at the origin (0,0,0).
We take a super-thin wire and start winding it on the surface of the sphere from one pole to another (let's assume poles are at $x=-R$ and $x=+R$), so that the windings are always parallel to x-z plane ("wire thickness" is negligible). So we are basically c... |
Two questions ...why is it that increasing the mass of a mass-spring system increases the resonance amplitude? And why is it that increasing mass causes its resonance curve to be 'narrower' - i.e. it has a steeper gradient away from the resonance frequency?
|
I am totally an amateur in this field, but I need this for my own multi-disciplinary project.
I know this might be a basic question, and I actually did do some researches. I just want to make sure that my understandings are correct. And I also have some questions.
My goal:
I want to calculate how far can aerosols diff... |
I am trying to get an expression for the radial timelike geodesics in EF coordinates:
$$g_{\mu\nu}dx^\mu dx^\nu = -\left(1-\frac{2GM}{r}\right)dv^2 +2dvdr +r^2d\Omega^2$$
for an observer initially stationary at $r_0 > 2GM$ falling into a black hole with a 4-velocity of $u^\mu = (\dot v(\lambda), \dot r(\lambda),0,0)$.
... |
The well-known equation for thin lens is:
$$\frac{1}{f}=\left(\frac{n_L}{n_m}-1\right)\left(\frac{1}{R_1}-\frac{1}{R_2}\right)$$
But there's a more appropriate equation that includes the thickness of the lens, which is:
$$\frac{1}{f}=\left(\frac{n_L}{n_m}-1\right)\left(\frac{1}{R_1}-\frac{1}{R_2}+\frac{(\frac{n_L}{n_m}... |
so I have a question here:
An airplane travelling initially at 240 m/s[28° s of e], takes 35 s to change its velocity to 220 m/s[28°e of s]. what is the average acceleration over this time interval?
I was told by my teacher to subtract the vectors, but how do you know when to subtract the vectors, and when to add the... |
After performing dimensional analysis of the current versus voltage graph when studying the photoelectric effect, this graph should measure units of siemens. It shows, however, high intensity and low intensity when looking at different positions of this graph. Can anyone clarify what the information the Current vs App... |
The propagator for a scalar particle can be written as
$$
\frac{1}{x + i\epsilon} = {\rm PV}\left( \frac{1}{x} \right) - i\pi\delta(x), \quad x = p^2 - m^2, \tag{1}
$$
where $p, m$ are the momentum and mass of the particle. My question is about how to compute ${\rm PV}(1/x)$. Gathering the post Principal value integral... |
I have learned about the commutators, and read this:
$$[A, f(B)] = f'[A,B]+\frac{1}{2}f''([A,B]B+B[A,B])+\frac{1}{3!}f'''([A,B]B^2+B[A,B]+B^2[A,B])+...$$
then Simplified to
$$[A, f(B)] = [A,B](f'+f''B+\frac{1}{2}f'''B^2+...)=[A,B]\frac{df}{dB}$$
I do understand the first two equations, only don't understand is why the ... |
In stars, the Balmer lines are usually seen in absorption, and they are "strongest" in stars with a surface temperature of about 10,000 kelvins (spectral type A). Balmer series|Role in astronomy
At 10,000 K the hydrogen is a plasma, I suppose. How can we talk about Balmer lines if the electrons are not bonded anymore... |
I'd like to preface this by saying that I am not talking about glowing caused by the heat generated from air resistance. Instead lets just say that the hypothetical object we're talking about it in a perfect vacuum.
This question was inspired by the idea that a car is hit by more rain when it is moving than when it's s... |
$SU(N)$ is the group of all $N\times N$ matrices that satisfy
$$ \mathbb{U}^\dagger\mathbb{U}=1~~,\quad\text{and}\qquad \det \mathbb{U}=1~~. $$
Denoting the $\mu$-row and $\nu$-column entry in $\mathbb{U}$ as $U^\mu_\nu$, the unitarity constraint may be written as
$$ \mathbb{U}^\dagger\mathbb{U}=1\quad\implies\quad \b... |
A hexagonal pencil lies on a
slope with inclination angle α; the angle
between the pencil’s axis and the line of
intersection of the slope and the horizontal
is φ. Under what condition will the pencil
not roll down?
The solution says $$cos(\phi) tan(\alpha) < tan(\frac{\pi}{6})$$
And the hints point toward 3D coordina... |
I made a classical experiment to demonstrate centrifugal force. The experimental setup is made to stand vertically and spun along the vertical axis. The balls that initially rest at the bottom, on spinning, move up to the chamber. Can someone please explain in layman terms as to why this happens? I have added images. F... |
I'm following the lecture notes by Timo Weigand on QFT.
On page 169, section 6.2 he is briefly touching on the non-abelian gauge symmetry in the SM.
The fundamental representation makes sense to me. For example, for $SU(3)$, we define the object or column vector with three component, suppressing spinor indices, $\psi(x... |
What is the purpose of Thévenin's theorem use if there are multiple formulas and theorems available for solving a circuit like KVL, mesh, nodal, etc?
|
We know from Lie representation theory that the Lie algebra is a vector space. Therefore a representation of the Lie group can be transformation of this vector space itself which we call the Adjoint Representation. An element of this vector space, is itself represented by a matrix. For example, in the case of $SU(3)$, ... |
While reading this answer by Rishab Navneet here, it is shown how we can visualize the harmonic oscillator as the shadow of a body moving in a circle onto a line. How was it found that the plane curve is a circle? More generally, is there a way to go from differential equations to see the plane curve whose projection o... |
This question is mainly about pressure and how kinetic forces work actually. But I would like to ask it within some certain examples:
Let's assume I have enough deuterium and tritium at right temperature and pressure to create fusion. You may think the force is applied downwards to these isotopes, and fusion event occu... |
Consider a canonical transformation from variable $(q,p) \rightarrow (Q,P)$ generated by the generating function $F(q,Q)=qQ$ so in this
case
$$p=\frac{\partial F}{\partial q}=Q\Rightarrow Q=p$$
and $$P=-\frac{\partial F}{\partial Q}=-q\Rightarrow P=-q$$
Which says in this space the old coordinate and momenta are change... |
You know how the way that electrons repel other electrons can be explained using particle interaction?...
Well, in that explanation an electron emits a photon...where does it get the energy to emit that photon...I mean its not like it KNOWS to emit a photon when it gets near an electron, so it must be emmiting photons ... |
I watched some videos and read a lot of posts mentioned that pointy shaped objects create denser electric field than other objects (especially spherical ones), that's why people use pointy and conductive metals to make lightning rods. As the clouds started to gather charges ( usually negative ions ) the lightning rods ... |
What is the relationship between near point and focal length of the eye?normally in a convex lens when the object is kept at 2f we get the same size image as shown . A healthy human eye can see objects without any trobles. Then is the near point of the eye, 2f of the eye lens? Im really confused about focal length of e... |
Suppose I have a particle in an infinite potential 2D well
$$
V(x,y) = \begin{cases}0 & \mathrm{if}\ 0<x<a, \ 0<y<b \\ \infty & \text{otherwise}.\end{cases}
$$
Now if I assume that $\Psi(x,y)=f(x)g(y)$,
I understand why I get
$$-\frac{\hbar^2}{2m}\nabla^2\Psi(x,y)=E \Psi (x,y)$$
and, after some derivations,
$$\frac{f'... |
Why does an electric spark occur discontinuously while an electric arc is not extinguished as long as the current is maintained?
|
I have a particle $p$ with speed $u$ in lab frame approaching a stationary particle $q$.
The $p^{\mu}$ and $q^{\mu}$ velocity 4-vectors are:
$$p_{LAB}^{\mu}=\gamma_u(c, u, 0, 0)$$
$$q_{LAB}^{\mu}=(c, 0, 0, 0)$$
To get to ZMF, I need a standard lorentz boost with speed $v=u/2$:
$$p_{ZMF}^{\mu}=
\begin{pmatrix}
\ga... |
If legth is increased, resistance is increased and heat produced is directly proportional to the resistance. So why current rating is still independent of its length? Please give answer assuming that there is no heat loss
|
Short question: Why is it that steel looks grey/silver on a macroscopic scale, whereas under a light microscope it appears white, yellow or brownish? (C. f.
https://de.wikipedia.org/wiki/Perlit_(Stahl)#/media/Datei:Perlit07.png or https://de.wikipedia.org/wiki/Austenit_(Phase)#/media/Datei:AISI_304_-_austenitic_structu... |
It is well-known that Maxwell added the displacement current term to Ampère's Law to make electrodynamics whole. As it is taught in the modern context (I am currently reading Griffiths's text, Introduction to Electrodynamics), we can motivate the addition of the displacement current term by noting that its addition to ... |
I'm wondering whether I correctly understand the increase of the Hall resistivity rho_xy in Quantum Hall effect.
As you can see the graph,
As magnetic field becomes much larger, the quantization of Landau level is also increase.
So, what I understand is, the density of states that passes the Fermi level(or Fermi surfa... |
I am trying to understand the proof of why the force acting on a spherical shell and a particle is
$$\frac{GMm}{r^2}$$
Where M is the mass of the sphere and m is the mass of the particle.
I am looking at Wikipedia in the section of "Outside a shell".
The method there is to "cut" the sphere into small rings and then ca... |
Update after @knzhou's comment
If in a theory, the coupling of the dark matter (DM) field to the Standard Model (SM) fields is small enough, the rate of interaction of the DM particles in the primordial plasma of the early Universe may not be able to compete with the expansion rate of the Universe i.e. $$\Gamma(T)<H(T)... |
In the problem I am trying to solve the axles and string have no mass. My friend who solved it said I need to find the acceleration of the axle by taking the second derivative of the displacement of the axel with respect to the ceiling, but how can the axle have acceleration if it’s given that it has no mass.
|
I was wondering what is the smallest unit of measurement possible. I found from google that it is Planck length but it was mentioned that any microscope couldn't see it. Then why is it even a unit of measurement? And how did they discover it or made it?
|
ow to prove this theorem? I have a doubt.
Theroem: Suppose that $w(x,\alpha)$ solved
$\ddot{w}+\frac{2}{x}\dot{w}+\alpha^{2}w=0$ with $w(0)=1$,
$\dot{w}(0)=0$, $w(1)=0$.
Then $v(x,\alpha) := \omega w(x,\alpha)$ solves
$\ddot{v}+\frac{2}{x}\dot{v}+\Theta^{2}v^{n}=0$ with $v(0)=\omega$,
$\dot{v}(0)=0$, $v(1)=0$ provided ... |
The direction of propagation of an electromagnetic wave is given by the Poynting Vector
\begin{equation}
\boldsymbol{S} = \frac{1}{\mu_0} \boldsymbol{E} \times \boldsymbol{B}.
\end{equation}
This diagram shows the direction in the opposite direction.
|
Is there inertia in absence of gravity? If I was in a region of space with zero gravity, would I have to apply some force to accelerate a massive body?
|
Considering a parallel plate capacitor initially charged, with circular plates of radius $a$ and with a distance $d$ from each other. A battery with internal resistance $r$ and EMF $ε$ is then connected to the capacitor and it starts charging.
In a teacher's lecture notes, he describes that the induced magnetic field a... |
If you were to change one universal physical constant (say, electron charge) then the universe would behave differently in observable ways. For one thing, this would change the fine structure constant, and the behaviour of every system which features it.
But suppose we also changed Planck's constant and/or the speed of... |
In the first place, I am struggling when trying to derive the path integral formulation of the Green function for non-interacting particles
$$G_{ij}(\tau)=-\frac{1}{Z}\int D(\bar{\psi},\psi) \psi_i(\tau)\bar{\psi}_j(0)e^{-iS(\bar{\psi},\psi)}$$
with the action $$S=\sum_i\int^{\beta}_{0}d\tau \bar{\psi}_i(\tau)(i\part... |
When we tear a dry paper, it produces a clear audible sound but when the same experiment is tried with a wet paper, we hardly hear any sound.
So can someone explain me what is happening here at the atomic scale ? Why isn't the wet paper creating any sound at all ?
|
I have a problem to solve for Physics III at university and I can't seem to understand how to solve this question.
I have the fundamental frequency at $440$ Hz, $L=1$ m, and $ρ=0.002$ kg/m.
After having proven that $f[n+1]/f[n]=f[n]/f[n-1]=a^{1/12}$ we are asked to find the positions $x(i)$ for $i=1,2,...,12$ in order ... |
Today I found a wierd thing that as I removed the pin of the echo dot
And after this I removed the adapter from the power supply and found a wierd buzz sound coming from the adapter but as I connected this pin to Echo dot thinking that it would stop the sound and to my surprise The buzz sound faded with time and event... |
I'm trying to find and model the apparent motion of the retrograde motion of Mars as viewed on Earth, incorporating Lagrangian or Hamiltonian mechanics.
For the lagrangian I have:
$L = \frac{1}{2}m_{Earth}(\dot{r}_{Earth}^2 + r_{Earth}^2 \dot{\theta}_{Earth}^2) + \frac{1}{2}m_{Mars}(\dot{r}_{Mars}^2 + r_{Mars}^2 \dot{\... |
I cannot understand why people say RG fixed point is scale invariant.
Scale invariant means the action $S[\phi]$ of the theory is invariant under scale transformation like $\phi(x)\to\lambda^{-\Delta}\phi(\lambda x)$. Fixed point of RG is a theory with action invariant under RG transformation (i.e. integrating out fas... |
Consider some quantum well of infinite depth, that is, for some region $R$,
$$
V(r)=
\begin{cases}
0, \quad r \in R \\
\infty, \quad r \notin R
\end{cases}
$$
My professor said, without much justification, that if a quantum particle were placed inside this well, the forces that the particle exerts on the sides of the ... |
The EEP says that freely falling frames are inertial. But suppose the freely falling frame is at some spacetime point. At that point you can by a suitable coordinate transformation reduce the metric to $\eta$. But after sometime the freely falling frame is at another location and you can't reduce the metric to $\eta$ a... |
If I see a body at temperature $T$, will I see the same temperature in another frame under a Lorentz boost. And will the internal energy of a body also remain invariant under a Lorentz boost or not..
|
I have a basic question about how to make the comparison of different measurements. For example, suppose I have measured the focal length of a convergent lens using three different methods, $A$ and $B$ and $C$, and I have obtained the following values and uncertainties:
$$\left({f^\prime}_{A}\pm\Delta{f^\prime}_{A}\rig... |
How much can liquid water be compressed?
I mean the maximum achieved in practice and the maximum achievable in theory.
Say for example one liter of water at 4 degrees Celsius.
Can it be compressed to fit in half a liter?
Are there any applications for compressed water?
|
I am trying to setup an interferometer to monitor displacements and tilts between two surfaces. I am quite struggling because I never studied optics deeply.
I have found in this paper (https://iopscience.iop.org/article/10.1088/0957-0233/25/7/075205/meta) a way to measure three degrees of freedom (yaw, pitch, spacing) ... |
Given two vectors in 3D superspace $(x_1^\mu,\theta_1^\alpha,\overline{\theta}_1^\alpha)$ and $(x_2^\mu,\theta_2^\alpha,\overline{\theta}_2^\alpha)$ I am trying to find a polynomial invariant under supersymmetry.
e.g. Something like:
$$I_{12} = (x_1-x_2)_\mu(x_1-x_2)^\mu + \theta_1 \gamma_\mu (x_1-x_2)^\mu\overline{\th... |
So a Lorentz transformation leaves the internal product invariant in the Minkowski spacetime. Let's say I do a Lorentz transformation, either a boost or a spatial rotation and I choose the reference frame at rest with this new observer. If I want to describe the metric in these new coordinates ($x'^{\mu}$) the metric i... |
The description of quasiparticles seems to come in two flavors: Completely qualitatively, where it is simply said that different (quasi-)particles interact to "form" a quasiparticle, or quantitatively, but indirectly via characterization of, e.g., the effective mass of interacting electrons, or via association with pea... |
Consider for simplicty 1d discrete chain - $x_1 \ldots x_n$, and let the field $\phi(x_i)$ reside on the sites of this chain.
Operators $\mathcal{O}$ in this this theory are hermitian $n \times n$ matrices.
Translationally invariant operators, those, which commute with the discrete translation operator $\mathcal{T}_i$ ... |
Considering a classical scalar field theory, I can find the canonical energy momentum tensor and if I calculate the $00$ component I get:
$$T^{00}= \frac{1}{2} \dot \phi^2 + \frac{1}{2} (\partial_i) \phi^2 + V(\phi) $$
and it should be an energy density. My issue is that this looks like energy but I don't see why it is... |
Any Hamiltonian dynamic on a qubit is necessarily a rotation.
I consider a two level system having a Hamiltonian $H$. Decomposing this Hamiltonian on the Pauli basis and using the fact it is Hermitian, it is easy to show that it can be rewritten as:
$$H=\frac{\hbar \Omega}{2}\overrightarrow{n}.\overrightarrow{\sigma}$$... |
Source: https://openstax.org/books/university-physics-volume-3/pages/3-3-multiple-slit-interference
$dsin(\theta) = m \lambda$ (1)
where
$d \mbox{= spacing between slits}$
$\theta \mbox{= angle between path and line from the slits to the screen}$
$\lambda \mbox{= wavelength of electromagnetic radiation}$
W... |
Let an atom is in superposition of two eigen energy states E1 and E2. If it returns to the ground level E0 what energy should have the photon released in the process?
|
Let's say we have a molecule which belongs to $D_{3h}$ point group. The IRREPs of inital and final states are as follows $A'_{1}$, $E'$. Hence, the IRREP for the dipole moment has to be $E'$ so that the transition is allowed. Does this mean the external electric field has to have $x$ and $y$ components to interact with... |
I know there are various definitions of the "preferred basis problem." I'm trying to understand what Wikipedia is saying here.
... a quantum state can equally well be described (e.g.) as having a well-defined position or as being a superposition of two delocalised states...
Do they mean something like this?
$$|\psi\r... |
I have a hard time combining two topics that are often discussed in physics in a coherent way.
In a lot of Introduction to particle physics-classes one will hear about "multiplets", which often are represented as in done in the left figure. On the other hand, if one attends a class on the Classification of compact simp... |
I have learned in Lagrangian Mechanics that the existence of time symmetries makes energy conserved. But from thermodynamics, we know that entropy introduces the forward arrow of time, i.e., the time asymmetry. We do know that energy is also conserved in thermodynamics. Where am I missing the point? Can someone connect... |
A flat platform is moving in a tunnel with velocity V relative to the tunnel. A stationary reference frame S1 is attached to the tunnel and a reference frame S2 is attached to the moving platform.
On the platform floor there is a light source perpendicular to the platform which turns on at the moment that S2 coincides ... |
I want to find the probing depth of the XAS spectroscopy at Iron edge, I found this paper: Magnetic circular dichroism study of Fe/Co/Cu (001) using electron yieldx-ray absorption spectroscopy with different probe depths but I still don't know how can I find the probing depth from this graph
Can somebody explain ?
|
The derivation of $s = s_0 + v_0t + ½at^2$ starts with $v = dx/dt$, which is rewritten as $v dt = dx$ and then $v$ is replaced with $at+v_i$. Then it is integrated.
Why is this substitution done, instead of integrating $v dt = dx$ directly? Is it to replace $v$ (not constant) with $a$ and $v_i$ (constants) and ther... |
Suppose I have a galactic ruler spanned from earth to Alpha Centauri. With marked units, so one can read off the distance starting with 0 at earth until 4 light-years at Alpha Centauri.
Now according to relativity, if I fly with my spaceship at 97% of the speed of light from earth to Alpha Centauri this will only take ... |
Here are the "knowns" that I'm working with.
Internal Energy for a monatomic gas is
$$U = (3/2)nRT$$
For a diatomic gas its
$$U = (5/2)nRT$$
All of my textbooks and online sources indicate that it's a (1/2)nRT contribution from each degree of freedom. So monatomic gets 3 spatial degrees of freedom. Diatomic gets 3 spat... |
Is there any way to add chemicals/elements to water to increase the penetration of light (em waves)?
|
I know that this subject is pretty saturated even thought i waited a few days.Its a generalized theoretical expiremental set up to try and measure one way speed of light,i just want any input on this but beware it will require a few minutes of your spare time.
(Last edit:The fundamental flaw is that the problem of simu... |
Generally to detect the hydrogen spectrum people uses the hydrogen gas tube as a light source.
My question is, since the gas in the tube is the hydrogen molecule $H_2$ why is the spectrum equal to the spectrum of atomic hydrogen $H$ ?
|
A beginner's question: Why does friction vanish at the top and bottom of loops? If friction works in the opposite direction of motion, then surely there must be some element of friction that is in the same direction as the normal force at the top of the loop? Or does friction have to always lie on the plane on which th... |
When one does the numerics for the usual random walk, one might use the transition matrix in order to get the probability ar time $t$ of the process. As expected, the asymptotic behavior yields a Gaussian.
There is a way to introduce non-markovianity in the process using a "microscopic" approach, dubbed the "elephant r... |
I've watched The Truth About Gravity With Professor Jim Al-Khalili | Gravity And Me | Spark where astronaut Chris Hadfield says at 3:55:
To come back to Earth is violent
Then after several seconds of music and video of descent
it can be five times the force of gravity...for quite a long time
I got immediately puzzl... |
Let's calculate the Miller indices of the yellow plane.
The intercepts are $(2,2,1)$ . Taking the reciprocals we get $1/2,1/2,1$ .
Clearing the fractions I get the indices as $(1,1,2)$. Why then does the figure show a different indices? Am I supposed to clear fractions as I've done? I'm finding conflicting answers on ... |
This makes intuitive sense to me but I have never heard anyone confirm it. Is it one photon per wave length or does it approximate one wavelength or something else?
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