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I have heard that spacetimes which admit null Killing vectors are sort of constrained. I wish to know how and why? What makes null Killing vectors so special?
|
The figure below shows a cord attached to a cart that can slide along a frictionless horizontal rail aligned along an x axis. The left end of the cord is pulled over a pulley, of negligible mass and friction and at cord height $h= 1.20$ m, so the cart slides from $x_1 = 3.00$ m to $x_2 = 1.00$ m. During the move, the ... |
By Bloch's theorem, all the eigenfunctions of a Hamiltonian with a periodic potential $$U({\vec r}+{\vec R})=U({\vec r})$$ can be chosen to have the form $$\psi_{n{\vec k}}({\vec r})=e^{i{\vec k}\cdot{\vec r}}u_{n{\vec k}}({\vec r})$$ where ${\vec k}$ can be any reciprocal lattice vector. However, the statement is tha... |
If regenerative braking can't stop an electric car fast enough, can't we actively slow it down by applying a reversed voltage to the DC motor?
EDIT: By really fast, I mean in emergency situations where you are about to hit something or someone and want to stop as fast as possible.
|
For hydrogen atom radial wave function is the analytic form of the matrix elements,
$$\langle n'\ell'|r^k|n\ell\rangle,$$
known? I am especially interested in $k=-2$ and $k=-3$.
Notation:
$$|n\ell\rangle=2^{\ell+1} e^{-\frac{r}{a n}} \sqrt{\frac{(-\ell+n-1)!}{a^3 n^4 (\ell+n)!}} \left(\frac{r}{a
n}\right)^\ell L_{-\... |
There are tons of information about the transition from static friction to kinetic friction but I'm having a little trouble finding information about the converse situation.
I need that because I'm simulating an oscillator damped by friction between two surfaces, but I'm in doubt if static friction will even develop p... |
let's consider a Fabry-Perot interferometer:
Illumination is provided by a diffuse source, and its rays are focused towards the cavity by a lens. Inside the cavity there are multiple reflections and transmissions of rays. Rays transmitted towards right will have a certain phase shift depending on the input wavelegth. ... |
Considering the usual Landau functional of the form:
$$ \beta L[\phi] = \int d^D r [\frac{1}{2} |\nabla \phi(r)|^2 + \frac{r_0}{2} |\phi(r)|^2 + \frac{u_0}{4} |\phi(r)|^4 ] $$
In searching for the upper critical dimension of the theory, we have two different viewpoints.
1) we know that at critical point, $r_0$ approach... |
Suppose the interior of the cavity is made of a non-black body. Then in thermal equilibrium, the spectral radiance of the non-black body, say $R_T^*(\nu)$, will be different from the spectral radiance of a pure black body, $R_T(\nu)$. So the way I see it, inside the cavity there is a distribution of radiation with spec... |
If a point charge $q$ is placed inside a cube (at the center), the electric flux comes out to be $q/\varepsilon_0$, which is same as that if the charge $q$ was placed at the center of a spherical shell.
The area vector for each infinitesimal area of the shell is parallel to the electric field vector, arising from the p... |
I think I understand the classical doppler effect in sound, where the equation is non-symmetric whether the source of the observer is moving because the speed of medium where sound wave propagates is different according to each of the observers.
I think I also understand why doppler effect is symmetric with light since... |
The convention for the Hydrogen atom's interpretation subject to the laws of quantum mechanics is that you can prove the quantization of $|L|$, $L_z$, and Energy through quantum numbers $\ell$, $m_\ell$, and $n$ respectively. You can check the wavefunction with some parameters as ($n$, $\ell$, $m_\ell$) based on the ap... |
I am studying the time-reversal symmetry in the context of
topological insulators.
As usual, the minimal non-trivial model to be considered is a two-level system with Hilbert space $\newcommand{\ket}[1]{|#1\rangle} \mathcal{H} = \text{span} \{\ket{0}, \ket{1}\}$.
Previously I always considered linear operators which ca... |
Consider a setup of an experiment to measure the photoelectric effect. We have a photodiode which is linked to an ammeter and a source of voltage which can apply voltage in either direction. Let the light shone onto the photodiode be such that the energy of photons exceeds the work function of the metal and a current i... |
Why is the direction of friction on an inclined plane always "up the incline" when a body goes up or down the plane with pure rolling motion?
|
I was just watching some videos and came across beta+ radiation (when a positron is emitted). It then occurred to me, how can the following be true, given that a positron and an electron have the same mass:
neutron = proton + electron [eq 1, beta- decay]
proton = neutron + positron [eq 2, beta+ decay]
As this would mea... |
The Planck collaboration has measured $w=-1.0$ for the equation of state of the cosmological constant Lambda. Can somebody explain what this means?
(1) Does $w=-1.0$ mean that Lambda was constant over time in the past?
(2) Does $w=-1.0$ mean that Lambda is made of virtual (instead of real) particles?
(3) Does $w=-1.0$ ... |
Does the shape of the pipe (the length not the cross section area) affect resistive force acting on water? Does keeping the pipe straight or keeping it in curves folded over each other effect the efficiency of water transport?
|
I know that changing volume changes internal energy and work for an ideal gas. However how does one add $Q$ into it? what exactly is the mechanism for doing so?
I know definition of $Q$ is that it is the net heat transfer. But how does one transfer heat?
But how does one "transfer heat" isn't heat already energy in tra... |
I am looking at waste heat recovery from gas fuelled engine exhaust.
I am using a data sheet for a Jenbacher J620 engine-. I assume the engine exhaust flows out through some kind of waste heat boiler and then to atmosphere. In the data sheet it is stated that;
Exhaust gas mass flow (wet) = 17325 kg hr ( not sure ab... |
While Solving the TISE for a particle an infinite square well with potential given by:
$$
U(x) = \left\{
\begin{array}{ll}
0 & \quad -L/2 \leq x \leq L/2 \\
\infty & \quad \text{otherwise}
\end{array}
\right.
$$
we get two sets of solutions:
$$
\psi(x) = \left\{
\begi... |
I'm learning physics in the online textbook "The Physics classroom". The chapter on energy of waves ("Energy Transport and the Amplitude of a Wave") makes the energy proportional to the square of the amplitude. And goes on: "Putting a lot of energy into a transverse pulse will not effect the wavelength, the frequency o... |
This example purports to show reflection of light rays from a spherical mirror. It looks good, until you try to draw a ray from the tip of the candle flame, then through the focal point, $F$, and then emerging parallel to the optic axis $(CF)$.
Go ahead, draw it on your computer monitor screen, or print this page and ... |
My question upon first glance looks quite elementary, however my specialisation in physics is not circuitry and such I am not sure of my calculations.
A little bit of background: I am trying to create a coilgun (Alas like so many others) to help translate my physical knowledge to a practical application. I am relativel... |
When we have a system we can have the surface containing it to be as big as we like assuming there is no other thing included as we make the boundary surface bigger. So what exactly would be the formal definition of a boundary?
For example we consider PdV as work to expand boundary of a system. But how do we precisely ... |
I have started studying electrodynamics for a couple of weeks and I came across a basic concept that I can not understand well, it is about the relationship between the magnetic field $H$ and the magnetization $M$ of an isotropic body ($M = \chi H$).
1- If $M$ is uniform, can I infer that $H$ is always constant inside... |
I'm currently studying the Brillouin-Wigner theory from the book "Atomic many-body theory" of I. Lindgren & J. Morrison.
The energy $E$ of the perturbated state $|\alpha>$ is linked to the unperturbed energy $E_0$ of the state $|\alpha>$ and the unperturbed eneregy $E_0^\beta$ of all the states $|\beta>$ such as $\alph... |
The relationship between angular and linear displacement is given by:
$$\vec{s}=\vec{\theta} \times \vec{r}$$
If we want to calculate the differential, it is:
$$d\vec{s}=d\vec{\theta} \times \vec{r} + d\vec{r} \times \vec{\theta}$$
In all the derivations I've came across the second term is zero, see here, right under F... |
consider there is 3 electron in surface of a sphere they will be arrange themselves in a triangle shape (because they want to be as much distance from each other).
now put an electron in center of this sphere, it can not change the arrangement of system so the place of electron in surface still unchanged but there ... |
This is a question from Maier-Saupe model section in the book.
Eq. (4.25) is:
$$(4.25)\ \ \ g=G/N=-k_BT\ln(4\pi\int_0^1 d\mu \exp\{\rho U \beta [(3\mu^2-1)Q-Q^2]\})$$
Eq. (4.26) is:
$$(4.26) \ \ \ g= G/N = -k_B T \ln(4\pi)+\rho U Q^2(1-\frac{2}{5}\beta \rho U)-\frac{8}{105}\beta^2\rho^3 U^3 Q^3 + \frac{4}{175}\beta^3 \... |
As we know that the conductor contains a lot of free charges positive as well negative. And also if it is placed inside the electric field the charges of conductor arranges themselves in such a way that they produce an equal and opposite induced electric field. This is what, when a conductor is placed in external elect... |
Given the initial state: $$\Psi(x,t=0)=c_1 \psi_1(x)+c_2\psi_2(x)+c_yy(x)$$ where $\psi_1$ and $\psi_2$ are eigenstates of $\hat{H}$ and $y(x)$ is a normalizable function but is not eigenstate of $\hat{H}$, how the $\Psi(x,t)$ wave function could be written?
|
consider the schematic, we have two capacitors, $C_1$ is charged and $C_2$ uncharged. (connect the plates together to keep the plates neutrally charged).
In principle $C_1$ generates an electric field $E$, but inside the plates of $C_2$ there is an electric field?
Another question, the electric field of C1 induces the ... |
If you attach a gyroscopic stabilizer to a vehicle like a car, plane, or boat, you stabilize the entire vehicle, effectively increasing the inertia of the vehicle.
My question is, what happens to the internal motions of a gas contained within a tank that is attached to a gyroscopic stabilizer?
This must be a known prob... |
Consider a system including two generalized coordinates $q_1$ and $q_2$ whose dynamics is supposed to be obtained using first-kind Euler-Lagrange (E-L) formalism
$$\frac{d}{dt}\frac{\partial L}{\partial \dot{q_{i}}} - \frac{\partial L}{\partial q_{i}} = 0 \quad (i=\{1,2\}),$$
where $L$ denotes the Lagrangian of the sys... |
Consider the following situation:
I have given that uniform density is $\lambda$ and the lengh of the rods as shown in the picture.
I marked my origin as the bottom of the left corner (and would like to stick with that mark)
I found that total mass is $\frac{5L\lambda}{2}$. I am not sure how I should calculate the sec... |
Our universe is expanding so every body is in acceleration. Now, all of atom of universe in acceleration. Why accelerating atoms don't produce photons?
|
How does $\{\gamma^\mu , \gamma^\nu\}= 2g^{\mu\nu}I$ imply that $\gamma^\mu$ is traceless?
where I represents the identity matrix
I know that $$\{\gamma^\mu , \gamma^\nu\}=\gamma^\mu\gamma^\nu + \gamma^\nu\gamma^\mu \tag{1}$$ and that
$$g^{\mu\nu}= \begin{pmatrix}
1 & 0 & 0 & 0 \\
0 & -1 & 0 & 0 \\
0 & 0 & -1 & 0 \\... |
In a spacetime diagram the spatialized time direction is the vertical $y$-axis and pure space direction is the horizontal $x$-axis, $ct$ and $x$, respectively.
The faster you go and therefore the more kinetic energy you have, you'll have a greater component of your spacetime vector in the $x$-direction. More of your en... |
I read that the meniscus, due to surface tension, exerts an upward pull to the liquid column below it.
The water rises to a height until the weight balances the pull.
Now liquid exerts pressure because of its weight. Then why does the pressure in the liquid column increase with depth?
|
Consider two people A and B in 1-dimensional space. If in A's frame, he observes that B is $1$ light-year apart and moving at a constant speed of $c/2$ to the right, A would think if he sends a light signal, it would take $2$ light years in his frame for the signal to get to B. Because in A's frame, the relative speed ... |
The SSH model describes states of electrons in a polyacetylene chain, which is modeled as a lattice with two orbitals per site. Now, in many articles it is claimed that in the ground state, half of all the energy eigenstates (those with non-positive energies) will be filled due to the Pauli exclusion principle.
This me... |
I am trying to understand a difference between LOCC and separable measurements.
If I get it right in the paper Quantum Nonlocality without Entanglement it was given a set of pure states, which cannot be distinguished by any LOCC measurement, but by a separable measurement. These states are:
\begin{align*}
\{&|1\rangle ... |
I was analyzing results of an experiment on a crossover filter and I was trying to take into consideration the parasitic resistance of the inductor L (called $R_L$).
I know the theoretical crossover frequency under the assumption that $R_1 = R_2$ and $R_L = R_3 = 0 \Omega$ is $f_c = \frac{1}{2\pi}\sqrt{\frac{1}{LC}}$.
... |
Let $u_{ik}$ denote the $i^{th}$ component of the position vector of the $k^{th}$ particle. Then kinetic energy of the system of $N$ particles is given by:
$$T=\frac{1}{2}\sum^N_{k=1}\sum^3_{i=1}m_k\dot u_{ik}\dot u_{ik}$$
Next, since $u_{ik}=U_{ik}(q_1, ... , q_n, t)$, we may write,
$$\dot u_{ik}=\frac{\partial U_{ik}... |
Dark matter is generally considered to be stable or at least long-lived (age of the universe) and I understand that is necessary to have such abundance today. My questions are 3:
Is it 100% necessary to have this long-lived condition? Both for a positive and negative answer could you please maybe elaborate on the nece... |
With rigid-body systems, we choose a finite number of generalized coordinates to model a system, i.e. a pendulum. However, I've read that deformable bodies like elastomers have "infinite" degrees of freedom. How does one write the Lagrange's equation for such systems? Is there an integral of infinitesimal volume?
|
I am currently studying the textbook Surface Enhanced Raman Spectroscopy -- Analytical, Biophysical, and Life Science Applications by Sebastian Schlücker, Wolfgang Kiefer. Chapter 1.2.2 Planar Surfaces says the following:
Once the complex dielectric function $\epsilon(\lambda)$ is known, all the electromagnetic proper... |
I have given a finite-dimensional matrix-representation of $SU(N)$. In this representation, the generators are denoted by $G^{a}$ for $a=1,\dots N^{2}-1$. I have to show that I can choose the generators always in such a way that
$$\operatorname{tr}(G^{a}G^{b})\propto \delta^{ab}.$$
How can I show this? One idea would ... |
I am trying to get the formula for energy of EM waves:
$$W = \frac{E^2 + B^2}{2}$$ calculating the work done on a test charge by the force: $$\mathbf F = q(\mathbf E + v \times \mathbf B)$$ $\mathbf E$ and $\mathbf B$ are vectors of the type $\mathbf F(u)$, $u = (\mathbf {k.x} - \omega t)$ and $\omega = \frac{c}{|k|}$... |
What does the coefficient physically mean for an operator that isn't an observable. For an observable the coefficient is the eigenvalue and is the value that will be measured, but for operators that aren't observables they can't be measured. An example is the Ladder Operator where $a\vert n \rangle = \sqrt{n+1}\vert n+... |
I have managed to confuse myself with the notion of hermiticity in momentum space.
In most quantum mechanical applications we assume:
$$
H(R) = H^{\dagger}(R)
$$
For $R$ some position vector. Now expanding this $H(R)$ in momentum space (on some lattice) gives:
$$
H(R) = \sum_{k}e^{ikR}H(k)
$$
So that the hermiticity co... |
(Assuming the hypothesis of the experiment is null)
Why are there fringes at the observer? From what I can understand of the experiment, the only reason why this can happen is if the light at the source is not coherent(however non-coherent light would make this experiment useless) or because of experimental inaccuraci... |
From Wikipedia:
Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed.
Suppose we apply 2 equal and opposite forces on a 2d plane with area 'A' perpendicular to it ($F_a$ & $F_b = F$)
Will we say that pressure is $0$ or $\frac{2F}{A}$
Suppose we h... |
I am currently learning about dynamical systems. I understand that dissipative systems have attractors but can not find anything online about whether or not non-dissipative systems have attractors. It may be that my understanding of attractors is not complete but any help with this would be much appreciated!
|
While a beam splitter can be thought of as producing a unitary transformation on the input states, it also known that in a realistic beam splitter, the reflective layer sandwiched between the two triangular prisms can absorb some of the incident photons.So, it appears that although a beam splitter effects a unitary tra... |
A metal rod is bolted down on one end. The other end has a rocket firmly attached, pointing perpendicularly to the rod. Before the rocket is turned on, the system is at rest. Thus net force $= 0$.
When the rocket is turned on, the only new force is thrust, which acts to the right (or left). If the net force when the ro... |
Purcell says that taking the surface integral of the magnetic field $\textbf{B}$ over the surfaces $S_{1}, S_{2}, S_{3},...$ below is a good way of taking the volume integral of $\textbf{B}$ in the neighborhood of these surfaces.
More specifically, he says in page $553$ of the third edition,
Now taking the surface i... |
Is there a rule-of-thumb for selecting a cutoff for the Morse potential in molecular dynamics simulation? For instance, is it typically some multiple of the equilibrium distance?
|
I'm studying my first-year physics in college, and I'm having to write a report of some proton-proton collisions that were registered in the LHC of CERN years ago. The main goal is to identify different bosons (W and Z) that are decaying into other elemental particles. I've been asked to get the W+/W- ratio in these ev... |
Every evening I am preparing hot water for my two year old son wakes up in the night to get his milk. We use a rather bad isolation can for this. It is a typical metal cylinder shaped can holding half a liter. If I put cooking hot water into it, I know that about 5 hours later it will have room temperature already, but... |
can somebody explain Why the liquids that are denser, place lower than those who have a lower density from a macroscopic and microscopic point of view??
|
In the paper https://arxiv.org/abs/1310.1385 it's calculated the electron electric dipole moment (eEDM) in terms of a function $f_1(x)$ defined as
$$
f_1(x) = \frac{2x}{\sqrt{1 - 4x}}\left[Li_2\left(1 - \frac{1 - \sqrt{1 - 4x}}{2x}\right) - Li_2\left(1 - \frac{1 + \sqrt{1 - 4x}}{2x}\right) \right], \quad Li_2(z) = -... |
Trying to do some basic manipulations with 4-vectors and I have a question about the proper (no pun intended) approach. It's probably easiest if we look at a simple example. So let's define a 4-velocity:
$$V=(\sqrt{t^2x^2 - 1}, tx, 0,0)$$
(Let me know if this isn't a valid 4-velocity. I tried to come up with a simple e... |
I'm working on a problem of my quantum mechanics homework set.
The problem is as follows:
A particle is in the ground state of infinite potential well (the well is determined by the region 0 < x < L)
At t=0, the wall at x=L starts to move adiabatically accordantly to the expression
$$L(t) = (2-e^{-\frac{t}{\tau}})L$$
T... |
This is a question from David J Griffith's Introduction to Electrodynamics.
A specified charge density $\sigma(\theta)=k\cos(\theta) $ is glued over the surface of a spherical shell of radius $R$. Find the resulting potential inside and outside the sphere.
The question was solved using legendre polynomials and the f... |
In the total destructive interference of a wave, the peak of one wave, perfectly aligns with the trough of another wave (assuming they have the exact same amplitude and phase), causing the waves to cancel out (I know this is very difficult experimentally).
An example using water waves would mean the output is the still... |
When the quantum field theory of a free fermion field is formulated on a finite lattice, the Hilbert space is finite-dimensional. The "spectrum condition" that we normally require in QFT is automatically satisfied: the spectrum of the Hamiltonian has a lower bound simply because the Hilbert space only has a finite numb... |
So I have a bit of an interesting question. My physics professor showed me this diagram:
And he asked us all what the potential difference, or voltage, was. Now, from my understanding these batteries are not in series. To be in series the negative terminal of one battery must touch the positive terminal of the next ba... |
I've recently been reading into deformation quantization as another formulation of quantum mechanics. I have focused on understanding the Moyal product in particular, as it contains the seeds for the non-classical behavior of the theory. I understand the mathematics and how to apply the definitions, but I am confused b... |
From where does an electron get its energy to revolve around the nucleus?
If it continues its movement, then from where does it get the energy?
|
Was just wondering if someone could clarify this situation:
When I take a Allen wrench and let it come in contact with an iron nail nothing happens. Not really surprising. None of the objects are magnetic.
When I take the wrench and let it touch the North end of a magnet and then let it come in contact with the iron na... |
In the double slit setup, why is only the path difference taken into account in calculating the phase difference? If the two waves from the two slits have to reach the detector at the same time then shouldn't one of them start out at an earlier time? And shouldn't that mean that one has to take the phase difference due... |
Problem:
Suppose we have a fixed planet $A$ exerting gravitational force and a particle $B$:
I want to obtain the function that gives the trajectory of $B$ to $A$. If $B$ has no velocity and no acceleration, the problem is easy. But if $B$ has some velocity into a certain direction, we could have:
Or (I guess)... |
The action for the gravitational field is known as the Einstein-Hilbert action:
$$\begin{equation}
S_{G}=\int d^4 x \sqrt{|g|} R
\end{equation}$$
where $R$ is the Ricci scalar.
The action for a matter field that is minimally coupled to gravity is:
$$\begin{equation}
S_{matter}=\int d^4 x \sqrt{|g|} \m... |
What is the difference between kinetic energy and thermal energy? Is it the size of the particles or number of particles or is there some other defining factor?
|
Consider a hydrogen chloride molecule (HCl). Let's assume that we're given the distance between hydrogen and chlorine nuclei $d=1.27 \times 10^{-30} \mbox{m}$. How to calculate electric dipole moment $p$ basing on that information? I came up with two ways of solving it but I'm not sure which one is correct.
Try one $p=... |
I am reading David Tong's lectures on string theory and on the page 180 in chapter 7 of his lecture notes http://www.damtp.cam.ac.uk/user/tong/string.html : he claims that D-branes are something in between the fundamental strings, which tension is independent of $g_s$, and solitonic branes, whose tension scales as $1/g... |
Consider for instance a parallel plate, a spherical or a cylindrical capacitor. Usually we analyze it by considering the surface charge density on each plate uniform, i.e. constant along the plate.
Why do we understand that? The only explanation I have found on the web is: "Because like charges repel one another".
Ok,... |
From the sources I've read it I found that it was "found by clausius" but how did he find it? What was the motivation?
I know of the clausius inequality and the fact that summing up the quantity $\frac{dQ}{T}$ over the whole cycle of a heat engine is equal to or less than zero always. However why is that for a reversib... |
First question
This question may be uber-trivial, but I have a spectrometer that provides as output the number of ADC counts at given wavelengths (the wavelength vector is not equally spaced), i.e., something like
╔═════════════════╦════════╗
║ Wavelength [nm] ║ Counts ║
╠═════════════════╬════════╣
║ 220 ║... |
I would like to simulate various shapes for rotor blades that will be used in a quadcopter. Which simulation software is used to understand how shapes, rotation interacts with the surrounding air? I know some physics, solving differential equations etc. I have AutoCad experience, and can work with Python APIs, Matlab, ... |
I tried to study some scattering problem and I face the following integral-
$$\int_{-a}^a \, dy_0\int_{-b}^b \, dz_0\int_0^{\infty}dt_0 \exp (-i\omega t_0)\frac{\delta (t_0-(t-\frac{s(t)}{c}))}{s(t)}$$
where, $a,b \in \mathbb{R}$, $t_0$ and $t$ represents time and $s(t)=\sqrt{d^2+(y-y_0)^2+(vt-z+z_0)^2}$, represents ti... |
The pitch of a note is how high or low it sounds. The pitch of a note depends on the frequency, or the number of vibrations each second.
If you listen to the notes produced by a loudspeaker connected to a signal generator you notice that, as the frequency increases, the pitch gets higher.
This is all the information ... |
Because relative motion between the two is causing current to flow in the coil, would there be any electromagnetic induction in the coil when both coil and magnet move simultaneously in opposite directions with equal speeds? Will the induced current be more than the standard induction model or will it be cancelled out ... |
We know that ,
$ \Delta G = \Delta H - T \Delta S$
We know that $ \Delta H = q = T \Delta S$
so,
$\Delta G = 0$
Where is my mistake here?
|
Hi when I am putting the Dishwashing liquid on the sponge it sometimes makes such small bubble like 5mm in the diameter that pops afterwards and I always wonder if it is possible that the particles of the popping liquid might fly so long (distance of outstretched hand) and hit the eye (because I am watching it).
Is the... |
I've recently read about material dispersion in an optical fibre which is caused when light that enters have several different wavelengths. What I don't understand is why would wavelength affect the speed of light in the core in anyway?
|
Imagine we have to liquids with densities $\rho_2$ and $\rho_1$ and $\rho_2>\rho_1$. Suppose we pour $\rho_1$ into a container. And then we pour $\rho_2$ on it. As a rule, the denser liquid ($\rho_2$) moves downwards and $\rho_1$ moves upwards. This process is caused by the buoyancy force. But how does the $\rho_2$ buo... |
Normalisation of the following wavefunction:
$\psi(\theta,\phi)=\cos(\theta)$
So I thought about setting the following
$N\int \cos(\theta)\cos^*(\theta) d\theta=1$
But then maybe I thought I was leaving out $\phi$ about using a volume integral like
$N\int^{2\pi}_{0} \int^{\pi}_{0}\int^{r}_{0} \cos(\theta) r^2drd\thet... |
One of the most central concepts in physics is energy. But on a deeper level energy is the same thing as information. Classically information about a system is given by spacetime coordinates and their derivatives. How much physics can be done without ever referring to time and space directly, calculating the physical p... |
I am currently studying the textbook Surface Enhanced Raman Spectroscopy -- Analytical, Biophysical, and Life Science Applications by Sebastian Schlücker, Wolfgang Kiefer. Chapter 1.2.3.2 Localized Surface Plasmon Resonances of the Cylinder says the following:
The exact solution of a 2D cylinder with dielectric functi... |
Imagine a fully charged capacitor.
This will create an electric field, and if a fixed charged particle is nearby, it will possess some amount of electric potential energy.
But what happens to the potential energy if one discharges the capacitor?
The potential energy must be converted into other forms of energy, but I c... |
Firstly, after reading this source, the length, $s$ of an energy-momentum four-vector is
$$s=m_0c^2\quad\fbox{Rest Mass}$$
But, according to this, the length of an energy-momentum four-vector is $$s=m_T^2c^4=E_T^2-p_T^2c^2\quad\fbox{Centre of Mass}$$
From yet another source, the length of an energy-momentum four-vecto... |
Could someone please tell me what is a quasi-local charge? For instance, why are Brown-York charges called quasi-local?
|
I am dealing with a two dimensional intrinsic semiconductor with a 100meV band gap. I have the conduction and valence band equations which are parabolics. Also I have been given the electron and hole effective masses ($m_n=0.01m_e$ and $m_h=m_e$). When computing the expression for n and p I make use of the density of s... |
Suppose that two particles (1) and (2) collide, and (1) experiences a force $\mathbf S_{12}$ from particle (2) and the sum of all the other possible forces as $\mathbf F_1$. Then, the impulse on (1) during the collision time interval $[0, \tau]$ can be written as
$$
\Delta \mathbf p_1 = \int_0^\tau \mathbf S_{12} + \m... |
I need to calculate the amount of heat that is lost in an hour. I know the temperature of the building the (effective) temperature of the outside and the thermal inertia of the building.
The building is not necessarily actualy cooling down since heating is a thing.
Is there a formula to calculate this?
does it make it... |
In the experiment we say that light coming from the slits at center part of the screen are in phase. Let at some time amplitude of both wave are at crest, then a maximum bright spot will be formed. But after some time both will have zero amplitude. Then at that time intensity will be lowest. Similarly as the amplitude ... |
I've heard that gases like hydrogen and helium leak out of the earth's gravity a little by little.
but where are they going? where do they end up after leaving earth's pull?
would the sun pull them towards itself? or they just wander in space until they find another space object with some mass?
|
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