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On a classical computer, the maximum possible number you can count to is a finite number. I've asked around about this, and generally there has been opinion one way or another, but it seems to me that this is the case. This is because a classical computer has a finite number of transistors, and so a finite address spac... |
Reading from example the old question, Angular Momentum and Kepler's Second Law
Considering that now I not remember the proof because starting from the angular moment conservation of $L$ we have the
$$v_pr_p = v_ar_a \tag 1$$
I wish to know the reason, with the physics or mathematical steps, because not can be the cons... |
I'm currently a third year (BSc.) physics major.
My learning method has always been to rewrite my notes and redo the exercises. I do that because my handwriting becomes pretty bad when the lecture goes too fast so that my notes are not very readable or at least you cannot really study from it. Therefore, it allows me t... |
I am reading a paper, written by G. Chalmers and W. Siegel - https://arxiv.org/abs/hep-th/9606061, where they discuss the action of self-dual Yang-Mills theory, which in light-cone formalism is obtained by preserving only one of the triple vertices with the gluons of following helicity (++-), or in Lorentz invariant fo... |
I am trying to create a simple car simulation in 2D in Unity3D, I'm having a hard time figuring out the right approach.
Say I have given the throttle percentage, I know the current engine's and wheels' angular speed and car's speed. Say, the car is moving on a flat ground, in a straight line.
I can calculate the engine... |
So I have this (possibly dumb) question about the implications of the second law of thermodynamics to the use of renewable energy for the world, so please bear with me. Here goes: Apart from the finiteness of fossil fuels (FFs), which is obviously an issue, the main problem for sustainability in burning FFs for energy ... |
I heated my milk cup in the microwave today and noticed that the cup was hot but not the handle. Even if I heat it too much , cups handle temperature remains the same. How is that possible?
|
I have been told that the acceleration of free fall is lower at the equator than at the poles, and that this has to do with the fact that at the equator, you are moving with circular motion so centripetal and centrifugal forces are at play, whereas at the pole this is not the case.
I've considered two frames of referen... |
G. Feinberg and J. Sucher showed that neutrino-pair exchange can induce long-range repulsive forces between electrons that is proportional to $r^{-6}$. In the paper, they also stated that changing a particle to its antiparticle changes the sign of the force. However, in case of neutrino-pair exchange, one cannot induc... |
In a multi-phase system with a liquid which meets a gas at the free surface, one can define liquid-vapour surface tension $\gamma_{LV}$: is this surface tension a constant when one varies the pressure of the vapour in the system? My suspicion is that whatever equation one has for the liquid-vapour surface tension woul... |
Does anyone know how to prove these statements?
|
Considering that I have a uniform magnetic field given by $\vec B = B_0 \hat k$ and $\vec v = (a\hat i,b\hat j,c\hat k )$.
Taking into account that the radius of the spiral path can be acquired by $R = \frac{mv}{qB}$, what are the components of the velocity vector that i should consider for the calculation? I believe ... |
The concept of thermodynamic equilibrium is only valid for isolated systems. Heat death of the universe can be understood as attainment of thermodynamic equilibrium.
There has been much fanfare about exploring heat death and what happens when we get there, but it isn't clear to me if we can even declare the universe an... |
I was trying to prove that for any second order tensor:
$$A^{\mu\nu}_{;\mu\nu}=A^{\mu\nu}_{;\nu\mu}$$
considering the torsion free property and locally flat coordinates. Considering the point where all the Christoffel symbols vanish and applying the covariant derivatives one at a time we see that all the terms with Chr... |
I have a few questions in understanding the difference between coupling and entanglement in quantum systems: Is there a clear boundary between quantum coupling and quantum entanglement?
If two quantum systems are coupled, do they need to be restricted to a certain distance? Is there a difference between 'coupling the t... |
I have to determine the Lagrangian and the angular velocity $\omega = \dot\theta$, in cylindrical coordinates $(r, \theta, z)$, of a electron with mass $m$ and charge $-e$, wich is experiencing a magnetic field $\textbf{B} = \nabla \times \textbf{A}$, where $\textbf{A}$ is given by:
$$
\begin{equation}
\textbf{A} = \fr... |
In diagnostic ultrasound the acoustic pulse propagates in a non-linear fashion (Duck 2002).
I have been taught that:
The increase in wave velocity in the compressive phase increases particle acceleration/velocity amplitude.
Through this a portion of the energy is converted to harmonic resonant frequency.
How does an ... |
PROBLEM: The figure above shows an accelerometer, a device for measuring the horizontal acceleration of cars and airplanes. A ball is free to roll on a parabolic track described by the equation $y=x^2$, where both x and y are in meters. A scale along the bottom is used to measure the ball’s horizontal position x. Find... |
How can we get the equations inside the box, which represent hopping between p and d orbital? I mean why we consider only two neighbouring?
|
When we solve the Einstein Field Equations
$G_{\mu\nu} = 8\pi T_{\mu\nu}$
one way of doing it is by specifying a symmetry (and thus a general form of the metric) and then specifying the stress-energy-tensor $T_{\mu\nu}$. Most examples found in text are for vacuum solutions (vanishing $T_{\mu\nu}$) or homogeneous isotro... |
Can a beam of light, coherent or otherwise, conduct electricity.
|
I'm no expert on string theory, but I've been reading about it. I've been quite surprised because of how it appears to be inconsistent with observations, but hasn't been rejected yet. Examples:
On the cosmological implications of the string Swampland
Criterion 2: The current B-mode constraint $\epsilon < 0.0044$ corre... |
The question I have is regarding material from an old University book I am currently reading, Chapter 13, "The Solid State", Third Edition, H.M Rosenburg.
And it states that the first mechanism of polarization is when an electric field $E$ acts on an individual atom and as a result that atom acquires a dipole moment $p... |
In the textbook, I am following it describes flavour space with basis up, down and strange quarks. I am not sure why we did not choose up, charm and top as the basis and why only three bases can define the complete flavour symmetry.
|
(Here's my understanding just in case if I misunderstood something)
I understand that for order to induce a voltage on the other side of the transformer or in the secondary coil even though there's no battery over there, a varying magnetic field is needed to be cut repeatedly (lenz's law).
This can be done using an AC ... |
I was working on some E&M problems when I came across one I did not quite understand, the problem goes something like this:
The potential at a radial distance r from a point charge q is V=$\frac{q}{4\pi\epsilon_0r}$
. Considering the absence
of radial symmetry find the vector form of the electric field (E) from this ex... |
Is the intensity or brightness of light the same idea? In other words, when we are observing Malus's law, are we looking at the "brightness" of light? If they are not the same quantity, how can we qualitatively see the intensity of light and distinguish it from the qualitative visualization of brightness?
|
If we have three capacitors in series, would the energy supplied to the system be the same as the energy that is contained in the equivalent capacitance of these three capacitors?
|
Deriving the transfer function
Suppose we have a free particle in one dimension with position $x$ and momentum $p$, and some damping $\Gamma$:
\begin{equation}
\begin{aligned}
\dot{x} &= p/m, \\
\dot{p} &= -\Gamma p+F(t).
\end{aligned}
\end{equation}
I want to find the impulse response if some force $F(t)$ is applied t... |
I believe that squeed vacuum can be represented in the Fock state basis as:
$|\mathrm{SMSV}\rangle=\frac{1}{\sqrt{\cosh r}} \sum_{n=0}^{\infty}\left(-e^{i \phi} \tanh r\right)^{n} \frac{\sqrt{(2 n) !}}{2^{n} n !}|2 n\rangle$
Looking at pictures, it seems as though the electric-field representation looks like this:
Whi... |
I was given a force, let's say $F = 15xy$ N to the right which moves a system from $A(0,0)$ to $B(3,4)$ and was to find the work done by the force, in Joules.
My approach was by using $\vec{F} = -\vec{\nabla}U$ to find the potential energy in $A(0,0)$ and the potential energy in $B(3,4)$, then using the relationship th... |
I've been reading Lancaster & Blundell, and in Chapter 14 they focus on the Lagrangian
$$
\mathcal{L}=(\partial^\mu\psi)^\dagger(\partial_\mu\psi) - m^2\psi^\dagger\psi.
$$
To impose invariance to the transformation $\psi\rightarrow\psi\exp(i\alpha(x))$, where $\alpha(x)$ is a coordinate-dependent phase, they replace t... |
I'm reading Merzbacher's Quantum mechanics. In Chapter 3, section 2, he tackles this question. For a function solely of coordinates, say $f(\mathbf r)$, he says that the expectation value is given by
$$\langle f(\mathbf r)\rangle = \int\psi^*(\mathbf r, t)\; f(\mathbf r)\;\psi(\mathbf r, t)\;d^3r, $$
and this makes sen... |
Suppose $f$ is function which depends on $\phi$, $f = f(\phi)$; and $\phi$ is a scalar field. We define
$$\square \equiv g^{\mu\nu} \nabla_\mu \nabla_\nu$$ and $$\nabla_\mu f(\phi) \equiv f_{;\nu}$$
Is this expression below correct?
$$ -f_{;\mu\nu} + \square f g_{\mu\nu} = 0 $$
I think it is correct since
$$ \nabla_... |
I am study about stellar model of stars by using polytropic equation of state $$P=k\rho ^{\gamma}$$ or $$P=k\rho ^{1+1/n }.$$
I studied that different values of polytropic index $n$ describes different physical interpretation of stars in stellar configurations. I want to know is there any physical acceptable posiblibi... |
While considering the contribution of the electronic specific heat capacity, it is stated that, when the temperature increases from 0 K , only the electrons with energy range of the order of $k_bT$ from the Fermi energy are excited. How was this range determined? (Ref: Introduction to Solid State Physics, 8th Edition b... |
In the book Basic Laws of Electromagnetism by Igor Irodov, He introduces force on a closed current-carrying loop as;
$$ F = \oint I \vec{dl} \times \vec{B}$$
And then he states the most interesting case of analysis is that of a small planar current loop of sufficiently small size and introduces a quantity $p_m$ to stud... |
This page on Wikipedia says, "In the language of quantum field theory, charge conjugation transforms as -
$\psi \Rightarrow -i\big(\bar{\psi} \gamma ^0 \gamma ^2 \big)^T $
$\bar{\psi} \Rightarrow -i\big(\gamma ^0 \gamma ^2 \psi \big)^T $
Could someone explain the reason behind choosing this specific mathematical tra... |
Many documentaries I see on the Solar System or the planets or the threat of collisions with meteorites talk about how lucky we are to have Jupiter, with its immense gravity attracting asteroids to it thereby protecting us and the rest of the Solar System. (It's been compared to a giant vacuum cleaner)
But I don't unde... |
The orbital angular momentum operator is given by
$$L_i=\epsilon_{ijk}x_j p_k$$
where $x$ and $p$ are the position and momentum operators.
In the Dirac equation, the hamiltonian operator is a 4x4 matrix. Will $L_i$ then also be a 4x4 matrix, which is given by $$L_i=\epsilon_{ijk}x_j p_k I$$
where $I$ is the identitiy m... |
Say there is a mass inside a liquid. What causes the force on its upside downwards and the force on its downside upwards? It seems logical that the downward force is due to the weight of the fluid above it, is it similar with the upward force? Just collision of liquid particles?
|
Is there a possibility that the global $U(1)$ of Peccei-Quinn theory can be identified with $U(1)_R$ symmetry in supersymmetric extensions of the Standard Model?
|
i'm currently reading about electron scattering and i cant understand the following statement of the book im reading. I quote the book(translated by me):
Many scattering experiments are done with unpolarized beams, and the polarization of the scattered particles are not measured. It is required that we take the mean va... |
At Fermilab the $g\!-\!2$ Muon experiment is going on which measures the magnetic dipole moment of the muon.
Can we explain the difference in prediction of theory and experiment if we introduce preons, particles which make up leptons and quarks?
|
QUESTION CONTEXT:
The universe is roughly 14B years while its diameter 93B light years, making radius 46.5B ly. If I understand correctly if we froze everything, go on the one side, then go to the other by the speed of light while everything else would be frozen, it would take us 93B ly. From the spectator POV however,... |
What is the complete general expression for the electric current $i$ induced in a coreless conductive loop of inductance $L$ and resistance $R$ when it is subjected to a given external magnetic flux, which is varying linearly from zero to some $\Phi_{EXT}$ in time interval $t_1-t_0$. Assume $i(t_0)=0$
According to the... |
An interesting thought struck me today, can sound be recovered? I mean sounds from the past, maybe a year or a millennium back.
|
I am currently working on quantum mechanical wave packets and minimum uncertainty states, to be specific I am trying to prove that the minimum uncertainty state is represented by a gaussian.
Anyway, I was following the argument reported on my textbook when I stumbled upon the following definition of the operators $\Del... |
I asked this question on electronics.SE but I don't get any good answer may be because its more of a physics question .
I just started reading about transistors from book "Microelectronics circuits"by Sedra/Smith,
This is written in book which I don't understand, any help would be much appreciated
For forward active mo... |
A common (but, as I think, incomplete) description of the uncertainity principle is the following:
You cannot determine a particle's momentum and position at high accuracy at the same time
It could also be other properties, but those two are the most commonly used to introduce the uncertainity principle. As fas as I ... |
My level of understanding of Particle Physics is elementary.
Suppose say I have conducted an experiment (maybe a poll) with a sample size of $n$, then I can calculate the mean $\mu$ and the standard deviation $\sigma$ from the data. Once I have this, I can calculate the confidence interval for some confidence level. Fo... |
We are asked to show that the ground state in a system of 3 free identical fermions that are on a circle of length, 2$\pi$, is equivalent to $\sin(q_1-q_2)+\sin(q_2-q_3)+\sin(q_3-q_1)$ up to some scalar multiplication. Furthermore we are asked to find the dimension of the eigenspace corresponding to the first excited e... |
According to this the plasma of a plasma torch can reach up to $28000$ degrees Centigrade.
How is it possible for the plasma to reach a temperature much higher than that of The Sun's surface and not completely burn and melt everything in a mile radius?
Even with the poor heat conductivity of the air this high a tempera... |
What is the exact form of local Lorentz transformations (from the point of view of the metric) in a curved spacetime background like in general relativity? It should deviate substantially from ordinary Lorentz transformations in Minkowski space.
|
We know that when two particles collides inelastically, the net energy equation is given by
$$E_i=E_f+Q$$ where $E_i$ and $E_f$ are initial and final mechanical energies of the particles and $Q$ is heat produces.
In most of the cases we have $Q>0$ and thus $E_i>E_f$.
I just want to know if there are cases where $E_i>E_... |
In Conformal Field Theory(Di Francesco et al.) chapter 4, the eq(4.17)
$$\dfrac{x^{'\mu}}{x^{'2}}=\dfrac{x^{\mu}}{x^2}-b^{\mu}.\tag{4.17}$$
can be derived from the last equation of (4.15)
$$x^{'\mu}=\dfrac{x^{\mu}-b^{\mu}x^2}{1-2b\cdot x+b^2x^2}.\tag{4.15}$$
Here I can't understand the calculation of $x^{'2}$. If I jus... |
I was wondering that a change in velocity can change the mass of an object slightly. I thought of this since p=mv so if we rearrange it to be m=p/v. Does this mean that a change in momentum or velocity can actually change the mass?
|
When a conducting rod moves orthogonally through a magnetic field, charges in that conductor experience a force that is perpendicular to both the magnetic field and their velocity. Let's say that because the electric force on this charge is at this point less than the magnetic force on it, the charge moves a little bit... |
In Type I superconductors the transition from normal to superconducting state occurs exactly at its transition temperature.
Does this mean that we could theoretically use only a little bit of energy to "turn it on" and "off"?
When we have a magnet on top of a Type I superconductor that transitions, we observe the Meiss... |
The ADM mass is defined for any asymptotic flat spacetime. Using cartesian coordinates:
\begin{equation}\tag{1}
E_{\text{ADM}} = -\: \frac{1}{16 \pi G} \, \lim_{r \, \rightarrow \, \infty}\oint_{\mathcal{S}_r} (\, \partial_j \, h_{ij} - \partial_i \, h_{kk}) \, dS_i.
\end{equation}
I consider linearized theory: $g_{... |
I am trying to show the following commutation relation for the Dirac matrices $\gamma^\mu$ and the metric $\eta^{\nu\lambda}$: $$2[\gamma^\mu,\eta^{\nu\lambda}I]=0$$
where $I$ is the 4x4 identity matrix and $\eta^{\nu\lambda}$ is a matrix element of the metric.
The Dirac matrices satisfy the following anti-commutation ... |
I'm thinking of a project that would send a laser beam through a powell lens to create a horizontal laser line. But I also want the line to have a certain vertical viewing angle. So just as an example say 20 degrees at 1000m. I don't mean bend the laser to 20 degrees, more like anyone at an angle of -20 to 20 degrees c... |
I often watch videos where they say that even Newton was bothered by the idea of action at a distance, and that General Relativity solved that problem.
But why is 'Action at distance' a problem in the first place? If universe does it, it does it. We shouldn't presume anything about the universe. What alternative do we ... |
When you lift your $2.5 \,\text{kg}$ laptop (a 15-inch Apple MacBook Pro, for example) by a foot, you do work of approximately $2.5 \,\text{kg} \times 10 \,\text{ms}^{−2} \times 0.3 \,\text{m} = 7.5 \,\text{J}$ which is about $4.7\times10^{19} \,\text{eV}$.
This is what I saw, my reputation is to low to ask them.
Where... |
How do exothermic reactions not violate energy conservation if e.g reactants were given 2200kJ/mol of energy and product released 2300kJ/mol of energy, where has this +100kJ/mol come from?(2200kJ/mol to break bonds and 2300kJ/mol released from products bonds forming).
|
I have this suction cup to hold dashcam in car. When I leave car in sun suction fails and camera falls down.
Did camera fall because air got heated under suction and expanded or plastic/rubber expansion?
If i fix suction at that hot windshield will it be strongest suction, as air can cool only from this temp ?
|
There are a lot of questions about the m87 image on this site, non of them actually answer my question.
I have read this question:
Does an expanding event horizon "swallow" nearby objects?
For the distant observer no event horizon ever forms and the the infalling observer takes an infinite time to pass the point r=rs ... |
Recently in a paper $[1]$ the researchers presented a rotating traversable wormhole solution using the famous Newman-Janis Algorithm $[2]$. But something is anoying me. In $[1]$ they presented the Morris-Throne metric in the following way (section 4):
(...) we rewrite the spherical symmetry wormhole
spacetime metric a... |
Say a charge is moving in space. Ignoring relativistic effects, how can we define a scalar potential for its electric field ?
My thoughts are that we can define the potential in exactly the same way as we did in electrostatics only that here our scalar potential will be time dependent. That is we go to some time instan... |
According to the Wikipedia article on Antiparticles:
Solutions of the Dirac equation contain negative energy quantum states. As a result, an electron could always radiate energy and fall into a negative energy state. Even worse, it could keep radiating infinite amounts of energy because there were infinitely many nega... |
I am doing a project with the Inelastic Collison equation and was wondering whether you can insert a relativistic mass into it or whether you can only use rest masses. If you can, is there any mathematical way to prove this?
Here is what I am trying to do:
In this equation:
$$V=\frac{M_1 V_1 + M_2 V_2}{M_1 + M_2}$$
I w... |
If you have an electron in a cavity and it has a ground state and an excited state which are somehow localized in either site of the cavity, does this mean that you can describe this situation as photon induced hopping? If you would then create a lattice of cavities all pointed in the x-direction could you then describ... |
Does anyone know how to find the Green function for this operator?
$$\delta(t_1 - t_2) \frac{d}{d t_2}.$$
Where we should have something like
$$\int dt_2 \delta(t_1 - t_2) \frac{d}{d t_2} G(t_2,t_3) = \delta(t_1 - t_3).$$
And/or any pertinent identities.
|
It's the whole day that I try to figure out at what point exactly the phase factor appearing in both creation and annihilation operators, went away maybe absorbed inside occupation number states. Here the procedure I followed: sorry in advanced for the "heavy" notation, I'm dumb and I need to have all informations in f... |
Suppose that we have a rotating fluid with nonzero heat conductivity and the rotation is uniform and stationary. The centrifugal force should then be compensated by the gradient of temperature (assume for simplicity that chemical potential is constant). Now, it is clear that there is no heat current induced by this gra... |
I’m studying aerodynamics. I understand Bernoulli’s principle very well, I just can't wrap my head around why pressure decreases as velocity increases. Like the garden hose example: if you cover the hose with your finger, water flows out of the hose faster (and somehow pressure decreases) but when the finger blocks the... |
How do you calculate acceleration due to gravity for objects in 3D space?
My current understanding for the force due to gravity on object $i$ from object $j$ is
$$\mathbf{F}_g=(\mathbf{r}_j-\mathbf{r}_i)m_jm_iG/|\mathbf{r}_j-\mathbf{r}_i|^3$$
where $\mathbf{r}_i$ and $\mathbf{r}_j$ are the 3D position vectors of object... |
I took a cart on a track and measured the velocity at two positions and the amount of time it took to get from gate 1 to gate 2. I have solved for the uncertainty of the velocity (was specifically told to take the standard deviation of all my results) but am not sure how to get the uncertainty in the acceleration.
For ... |
What process needs to be done on molecules to put them in a state of superposition in laboratory experiments?
I understand that it involves working with systems cooled down to very low temperatures. And one of the steps is getting the object to its ground state. But what specific operation places an object into superpo... |
There are formulations of QED where electrostatic Coulomb fields around a charge are expressed as coherent states of photons with longitudinal/timelike polarization. See for example chapter 3 of Scharf's "Finite Quantum Electrodynamics" and https://arxiv.org/abs/1001.1387
How general is this claim? Are there formul... |
Neutron stars form dense clusters of neutrons which I have heard being called an element 0 and theoretically could form strange matter and the like from what I have read. Given that a black hole is essentially a more extreme version of a neutron star would black holes be made of a new form or state of matter. Essential... |
So let we have a magnetic field which is
$$B_\mu=\frac{q}{2}\frac{x_\mu}{|x|^3}-2\pi q\delta_{3\mu}\theta(x_3)\delta{(x_1)}\delta{(x_2)},\tag{4.65}$$
where $\theta$ is step function and $\delta{(x_\mu)}$ is dirac delta.
So in many places (for example Polyakov's book on gauges and strings at eq 4.64 and eq 4.65), it is ... |
I am a bit perplexed with regards rotations about a certain axis.
Say we have a cuboid with lengths $l_1$, $l_2$, $l_3$ (not a cube, so $l_1$ does not equal $l_2$ does not equal $l_3$). I am okay with determining the inertia tensor matrix about the centre of mass and about a corner of the body (of constant density, I s... |
I’m confused about work and gases. So let’s say we have a container with gas in it as well as a piston above it that is moveable. If we draw a force diagram of the gas, it has a force applied from the piston/surroundings, and an equal and opposite force from the container. So when a gas does work on its surroundings , ... |
Let’s say you have a moving charge, relative to a stationary observer. They measure that it has an electric field $E$ and a magnetic field $B$. Because the observer is stationary, they experience no magnetic force only the electric force. However, because that charge is moving, relative to my stationary observer there ... |
I came across degenerate matter (not the first time) after learning about degeneracy in eigenstates and eigenvalues. Are the two connected? Or is this just another use for the term?
|
It is said in arXiv:1401.4118 that Squeezed vacuum can be represented in the Fock state basis as:
$$|\mathrm{SMSV}\rangle=\frac{1}{\sqrt{\cosh r}} \sum_{n=0}^{\infty}\left(-e^{i \phi} \tanh r\right)^{n} \frac{\sqrt{(2 n) !}}{2^{n} n !}|2 n\rangle$$
In my attempt to plot some pictures of the wavefunctions of squeezed li... |
I had a discussion with a friend who claimed that vinegar is useful when defrosting a freezer because it lowers water's melting/freezing point. I disagreed, because I believe that the freezing point is irrelevant as long as the surrounding temperature is significantly higher that 0 ℃ (which it typically is in a normal ... |
I'm having trouble properly conceptualizing a question.
The question is:
"Suppose you are driving down a steep hill (5 degrees, 8.7%, which is fairly steep for roads), on a rainy day ($\mu$ = .5) at a reckless 30 $\frac{m}{s}$. The stoplight at the bottom of the high turns red. It is 75 meters in front of you. (You can... |
This is a part of a question I was solving, the question asked about what will happen if the switch is in position 2.
My answer was to say that all the lamps are going to turn on as I thought the current will travel the way I drew in the picture.
I knew later, though, that my answer was wrong and that the current will... |
As far as I have understood, the case is that there is nothing that argues that time or space is continuous, but at the same time we must assume this in order to be able to calculate derivatives or integrals with respect to these, how can we justify this?
|
When an electron in a solar cell is excited beyond the conduction band edge, it will most likely thermalize which can only be counted as a heat loss. But in a few cases the electron will directly recombine back to the valence band, correct? My question: How "often" does this happen?
I heard of the future technology Hot... |
This is a bit of a weird one but I didn't know where else to ask this.
I was recently talking to my brother and he told me about an idea he had talked with his boss about how to create compressed hydrogen and also use it to do work in a somewhat renewable way. I was skeptical of his claims but I wasn't able to pinpoint... |
I have invented this little problem to help me understand the magnetic force better.
Imagine 3 positive charges all on a line. The first charge is separated by distance D from the second charge, and the second charge by distance D from the third charge. So
+ ---------------- + ------------------ +
... |
For the VOC it is:
VOC = E_g - something,
where something is positive and depends on the Urbach energy. Otherwise it should be linear:
https://aip.scitation.org/doi/pdf/10.1063/1.49397
For the ISC I didn't find anything. Only one paper on bifacial solar cells, where there Equation (4) gives a formula, but I am not sure... |
I'm working on a problem in Griffiths E&M and I can't seem to figure out to get
$$\vec{v}=R\omega\hat{\phi}+\dot{z}\hat{z}$$ from just $R$ which is the radius of a disk centered at the origin in the $xy$-plane. It revolves around the $z$-axis with $\omega_0$.
If $\vec{\omega}=\omega_0\hat{\phi}$ and $\vec{r}=R\hat{s}$,... |
I have read numerous things saying that a travelling charged particle emits radiation primarily in a cone in the direction of travel, and other places say the radiation is emitted and polarized in an azimuthal direction (or normal, or perpendicular, or transverse, etc.)
I am confused....
|
To find the attractions between planets and stuff like that, you use the center of gravity/mass to apply to Newton's equation. So even if those planets collided into each other, you could separate them if you give enough force, because $r$ (distance between the center of gravity/mass of each planet) in the gravitation ... |
Goldstone theorem states that when a continuous symmetry is broken there is a massless mode for each broken generator. To exemplify the theorem, many references consider the complex scalar theory with an $U(N)$ symmetry. The potential for the theory is
$$-m^2H^\dagger H+\frac{\lambda^2}{2}(H^\dagger H)^2$$
when $m>0$ t... |
For a closed subshell configuration of a many-electron atom, $M_L=\sum_i m_{\ell_i}=0$ and $M_S=\sum_i m_{s_i}=0$. But I do not understand why does it necessarily mean $L=S=0$. The values $M_L=M_S=0$ are compatible with nonzero values of L and S. Then how does $M_L=M_S=0$ enforce $L=S=0$? I looked at all my books (Bran... |
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