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Please don't see this as a homework question, for I have already solved the problem and all I'm trying to do is understand the results and make a correct interpretation. In a cylinder made out of magnetic material without free currents, with magnetization $$ \boldsymbol{M} = M_0 \frac{r}{a} \boldsymbol{u}_{\phi} $$ one... |
The quantum entanglement and delayed choice quantum eraser variation to the double slit experiment has given very strange results. So if a particle is detected then the pattern is changed. Does the detected particle communicate with its entangled pair in the past? or there is another explanation to it?
|
My question is whether light can be produced in some way through neutral particles?
Like usually I hear about light being produced by oscillating charged particles. Can it be produced by neutral particles by any means, and not involving charged particles? I've heard light being produced by smashing neutral with charged... |
The question I'm stuck with is the following:
The quadrupole moment in a way describes the shape of the electric charge distribution of a nucleus right?
Oblate if negative, prolate if positive and 0 if spherical.
Furthermore, things that add to it are the rotation of the nucleus and which excited state it is in...etc.
... |
Why is electric field inside a charged conductor always zero? In an uncharged conductor if an electric field is applied then the charges reconfigure themselves as to have no net electric field. In a case of a charged conductor when a net electric field always zero even when there is no electric field applied. Can some... |
Suppose we have two syringes -- both in the halfway position -- filled with water and connected by a tube (there is no air in the system, only water).
If we push one of the syringe plungers in, then the other syringe's plunger will move outward. I'm content with this
What happens if I pull out one of the syringe plunge... |
Say you can measure $3$ observables $(A, B, C)$ and you do the measurements in two different ways.
$\newcommand{\ket}[1]{|#1\rangle}
\newcommand{\bra}[1]{\langle#1|}
\newcommand{\braket}[2]{\langle#1|#2\rangle}$
In the first setup, you first measure $A$ and block all except one of the outputs, say eigenstate $\ket{a^1}... |
I think that, since Earth is spherical, the amount of mass in the upper half of Earth should be the same as the second half, therefore, if the strength of gravitational field increase linearly from distance 0 to R, it should also decrease at the same rate from R to 2R, however, it will never reach zero
|
I read that the Inflationary Epoch is posited to have lasted $10^{-32}s$. That seems quite quick.
In the big bang model did the universe therefore essentially reach the size it is now in less than one day?
I am look to see some numbers and calculations of the rate of expansion one day after the big bang and also now.
T... |
I've been studying quantum computers and while it's apparent to me how electrons are used as qubits, through their spin number, it's not as clear what makes a photon a viable candidate to be used as a qubit.
I understand how entanglement between qubits works, and how quantum gates work (though I haven't looked into opt... |
My understanding of surface tension is that it acts perpendicular to an imaginary line on the surface of the liquid. i.e for a paper clip it will act horizontally, and in the same plane as the surface of water.
Gravity, however will act downwards, and the two forces in theory shouldn't balance each other right? Then h... |
I am involved in a research project in Magnetostatics. I am a Mathematician, but I did take EM for Electrical Engineers during my Electrical Engineering years. Lately though, my research collaborator has been talking about sources and surface currents in Magnetostatics, and I have questions since I have not studied the... |
Over time, gravity (on a macro scale) and erosion (on a micro scale) will work together to smooth out a planet. How does the gravity work? Is it like erosion on a massive scale (ie pulling down the outside of a mountain) or does it un-deform the planet like unsqueezing a water ballon (ie by pulling the inside of a moun... |
I have the operators
$\hat{V}=\sum_{j=-\infty}^{\infty}\hat{a}_{j}^{\dagger} \, \hat{a}_{j+1}, \qquad \hat{V}^{\dagger} = \sum_{j=-\infty}^{\infty} \hat{a}_{j+1}^{\dagger} \, \hat{a}_{j}$,
where $\hat{a}_{j} \; (\hat{a}_{j}^{\dagger})$ is the bosonic annihilation (creation) operator and $j$ is a subscript running from... |
I've recently come about the free plane wave solutions to the Dirac equation, and i'm having a hard time proving that the normalization factor $n$ is
$$n=\frac{1}{\sqrt{2m(m+\omega)}}$$
Where $\omega$ is the energy.
The information that i've used to try and prove it is that
$$\bar{u}_ru_s=\delta_{rs}$$
(Im focusing on ... |
Why can visible light, which lies in the middle between X-ray and radio waves in terms of frequency/energy, not penetrate walls?
|
How do I tensor differentiate a factor without tensor, such as:
$$\partial_\mu e^{i\Lambda(x)}\tag{1}$$
Should it be zero or should I differentiate it twice changing the order of the tensors follows:
$$\partial_\mu e^{i_\mu \Lambda^\mu}+ \partial_\mu e^{i^\mu \Lambda_\mu}= ({i_\mu + \Lambda_\mu} )e^{i\Lambda }$$
If the... |
I'm trying to understand why it is that the physical quantities $\rho=T_{\mu \nu}a^{\mu}a^{\nu}$ and $b^{\mu}=T^{\mu}_{\:\: \nu}a^{\nu}$ can be given the physical interpretation that they have which are:
if $a^{\mu}$ is timelike then (1) $\rho$ is the total mass energy density (2) $b^{\mu}$ is the momentum (both measu... |
If Observer A moves at speed $v$ respect to observer B, then there is a time dilation given by
$$t_B=t_A\gamma$$
as is known from special relativity. Here, $t_A$ is the time interval measured by A and $t_B$ is the time interval measured by B. However, a friend of mine asked me about the inverse case, what if we take th... |
I stumbled across the Wikipedia article on coupling constants [1] and didn't quite unterstand, what the paragraph on running couplings is trying to express.
It relates the virtual particles taking part in some scattering process and the apparent violation of energy conservation to the uncertainty principle of energy an... |
I'm trying to understand the physical interpretation of the value of the probability current density of an electron in a hydrogen atom: $$j_r=0$$$$j_{\theta}=0$$ $$j_{\phi}=\frac{h}{rsin\theta}|\psi_{nlm}(r,\theta,\phi)|$$
I kind of understand why $j_r=0$, but I can't find any physical interpretation for $j_\theta$ bei... |
The relation is often stated as $E = h\nu$
Simple enough. But the frequency $\nu$ doesn't have to be a natural number or even an integer, correct? It can be any rational number or even any real number. So why is the energy $E$ quantized anyway? And if the given equation is technically faulty then how should it be writt... |
I'm curious if there's a relationship between the inhomogeneous spin dephasing and the optical coherence of a material. Certainly, in many applications quantum information applications, you want both to be as long as possible. But, I'm curious if there is any direct relationship between the two?
More specifically, is t... |
Photons do not seem to be very well defined in quantum mechanics like an electron or even a quark. My assumption is that the relationship between the quantum and classical views on radiation must be fleshed out to some extent. Ive read in several places that quantum mechanics converge into classical mechanics when expa... |
The metric is ($a,b, = 0,1,2,3,4$)
\begin{equation}\label{eq:1}
ds^2 = g_{\mu\nu}dx^\mu dx^\nu + e^{2\sigma}(dx^4 + A_\mu dx^\mu)^2
= \eta_{ab}e^ae^b + (e^4)^2.
\end{equation}
The vielbeins are
$e^a = {e^a}_\mu dx^\mu$ and
$e^4 = e^\sigma(dx^4 + A_\mu dx^\mu)$.
The spin connection is defined as
$de^I = -\varOmega^I_{\;... |
Is it possible to clone physical objects, as a computer does with any file?
For example, can we do a Ctrl + C and Ctrl + V of the quantum state, and by extension, of the atoms of a car?
|
A ball of mass $m$ and speed $v$ strikes a wall perpendicularly and rebounds with undiminished speed. If the time of collision is $\Delta{t}$, what is the average force exerted by the ball on the wall?
My thoughts were that we would simply use $\Delta{p}=-mv$ and continue on, but the given solution is
The change in ... |
I was reading the Feynman lecture about vector magnetic potential and I have a doubt about it. For a certain example it is written that:
We have, then, a general method for finding the magnetic field of steady currents. The principle is: the $x$-component of vector potential arising from a current density $\boldsymbo... |
I am trying to understand the paper "Off-diagonal coefficients of the DeWitt-Schwinger and Hadamard representations of the Feynman propagator" by Decanini and Folacci.
Consider a ($m$)assive scalar field $\phi$ living in a spacetime with metric $g$ (coupled to the Ricci scalar $R$ with coupling $\xi$). I specify to $D=... |
I want to ask a question about the derivation of the partial gas law that I covered today.
Our lecturer spoke about the Helmhotz free energy that can be expressed (when measured relative to the ground state)
$$A = A(0) - kTlnQ$$
and given that
$$Q = \frac{q^N}{N!}$$
$$q = \frac{V}{ʌ^3}$$
$$P = \frac{\partial A}{\part... |
Photons are considered massless so how do they interact with gravity? According to Einstein Relativity, only curvature of space is responsible for bending of light rays. If so, and mass to mass interaction is useless, is considering gravitation a force pointless?
|
If I wear a VR headset, I still have to wear my glasses, because the image arriving on the surface of my eye is still arriving as if it were actually far away. But how does that work? Why does the image from a distant object arrive at the surface of the eye differently than a near object?
|
Can the Euler-Maruyama method be used to simulate Langevin equations for non-Gaussian white noise?
I need to evaluate a Langevin equation of the form
$$ dx= a(x)dt+D \eta dt$$
where $\eta$ is a non-Gaussian white noise.
|
Is it possible somehow that antimatter (-ve mass) could create an upside curvature on spacetime, as it bulges outward rather than inward as in case of real matter (+ve mass)?
|
I am not getting how above equation is derived using cylindrical coordinates transformations.
This is from page 36, Mathew Sadiku
|
We know that the eigenvalues for $\hat{J}^2$ is $2j+1$ - fold degenerate. However, most textbooks I have read, when explaining the ladder operator, shows the action of the ladder operator to be like this:
$$
\hat{J}_z \bigg(\hat{J}_{-} |j, m\rangle \bigg) = \hbar(m-1) \ \hat{J}_{-} |j, m\rangle
$$
they then proceed to ... |
Imagine a charged particle suspended between 2 horizontal magnetic plates, which create a uniform magnetic field. Now instantaneously, the particle is accelerated to velocity $v$. By my understanding, the particle will now start doing uniform circular motion, due to the Lorentz force.
However, what if the magnetic fiel... |
I found the difference between dynamical and static variables explained here: https://physics.stackexchange.com/a/154977/239775
My question is: Are only dynamical variables represented by observables in quantum mechanics, or both?
|
How to calculate the perpendicular vector of a given vector $A=[a,b,c]$ in Cartesian system? Any other information is not there.
|
Consider the image above. The block has a mass $m\;kg$, the friction coefficient between the block and the surface is $μ$, the spring is massless with spring constant is $k$.
The question asks to find the minimum force which must be applied to the spring so that the block just slides on the surface.
I am unable to pr... |
Coulomb's Law states that :
$$F_e = K_e \dfrac{q_1q_2}{d^2}$$ where $F_e$ means the electrostatic force between two charges of magnitude $q_1$ and $q_2$ and $d$ is the distance between them.
Scientist Charles Augustine de Coulomb derived it in the following manner:
He observed that $F_e$ was directly proportional to t... |
I have some problem with the virtual particle process as discussed below.
We have some interactions that have real photon as produced particle. We consider a tree level Feynman diagram for it and the interaction is shown in the picture here:
(direction of time is from left to right)
Here, $u$ can be any particle obeyi... |
$$ \psi(\theta,\phi) = 1/(2\sqrt{3\pi}) [ \sqrt{5} \cos\theta + \sin (\theta + \phi) + \sin(\theta -\phi) $$
Calculate $\hat{L}^2 \psi$ and $\hat{L}_z \psi$. Is $\psi$ an eigenstate of $\hat{L}^2$ and $\hat{L}_z$?
I solve and I get $\hat{L}^2 \psi$ = 2$\hbar^2 \psi$ and $\hat{L}_z \psi$ = $-\hbar [(\sqrt{2}/3) Y^1_... |
I'm trying to obtain the Mass-radius diagram of a non-rotating neutron star, following the work of Oppenheimer and Volkoff (I consider an EoS of a free Fermi gas of neutrons) :
$$E(x)=\epsilon_0\left[(2x^3+x)(1+x^2)^{1/2}-\text{arcsinh}(x)\right]=\epsilon_0 e(x) $$
$$P(x)=\epsilon_0\left[\left(\frac{2}{3}x^3-x\right)\... |
I have to compute the chemical potential in the zero bandwidth s-f model, analized in this article, from the following condition
$$
n=\left\langle\hat{n}_{\uparrow}\right\rangle+\left\langle\hat{n}_{\uparrow}\right\rangle
$$
where $n$ is the band occupation while the average values are
$$
\left\langle\hat{n}_{\sigma}... |
We have the Gauss-Bonnet term
$$L_{GB}=R^{2}-4R_{\mu\nu}R^{\mu\nu}+R_{\mu\nu\rho\sigma}R^{\mu\nu\rho\sigma}$$
where $R$, $R_{\mu\nu}$ and $R_{\mu\nu\rho\sigma}$ are the Ricci scalar, the Ricci tensor and the Riemann tensor respectively. The variation of $L_{GB}$ with respect to the metric $g_{\mu\nu}$ should give $$\fr... |
In Taylor's classical mechanics, he derived Lagrange equations and showed that they are equivalent to Newton's second law. Then, it was obvious that Lagrange equations are similar to the Euler-Lagrange equation, meaning that solving them makes "something" stationary. As a result, he introduced the principle of stationa... |
I hope this is the correct TA here, but please consider the below rudimentary diagram, which depicts bodyweight plank rows using a particular device.
The image shows the setup of the device, and the exercise:
I have not studied physics for years, and have no idea where to start with this, so I am asking here:
1) Giv... |
My mom uses frozen sausages for a soup. She defrosts frozen sausages by submerging them in water (room temperature I believe). She claims this makes them defrost faster. She learned this from some article in a magazine and now swears by it. She is of no scientific background, so no accurate experiments have been made. ... |
My question arises from Susskinds book on Special Relativity and Classical Field Theory. (page 102 equation 3.29 to 3.30 and page 105 equation 3.34 to 3.36.)
The relativistic Lagrangian for a free particle is given by the following equation.
$$
L = -mc^2\sqrt{1-\frac{v^2}{c^2}} = \frac{-mc^2}{\dot{X}^0},\tag{1}
$$
whe... |
I am studying Special Relativity along with the tensor notation used there. I do not know General Relativity but I have heard that Special Relativity is formulated in pseudo-flat space. I am interested to know about this fact in a little more detail, especially about the form of the metric tensor in Special Relativity.... |
If we integrate both sides of the Lorenz gauge condition, $\nabla \cdot \mathbf{A} = -\frac{1}{c^2}\frac{\partial \phi}{\partial t}$, over a small volume (free of charges for simplicity), we get:
$$
\int_V \nabla \cdot \mathbf{A} \, dV = -\frac{1}{c^2} \int_V \frac{\partial \phi}{\partial t} \, dV
$$
Applying the Gauss... |
Will the electrons flow from negative terminal of the battery to the charged body so as to neutralized a charged body..thus causing a decrease in pd of battery
|
The ponderomotive force tells me that if I apply some non-uniform oscillating acceleration field $\ddot{x} = g(x) cos (\omega t)$ where $g(x)$ is the strength of the field as a function of location and $cos(\omega t)$ describes high frequency oscillations, it will result in some motion towards decreasing $g(x)$:
$\ddot... |
In first quantization I've easily shown that the momentum operator is the generator of translations. I simply used the Baker-Hausdorff relation and the definition of Taylor series to show that.
But now in second quantization, my total momentum operator is defined as $T=\sum_{k\sigma} \vec{k}c^\dagger_{k\sigma}c_{k\sigm... |
a link to consideration about the perpetual motion machine
[]
diagrams and working out are included above. the assumptions are set to minimise engineering challenge and face perpetual motion machine on a conceptual level. What is wrong about the working?
|
I am trying to verify the commutation relation given in Peskin and Schroeder. In particular, I don't know how to go between these two lines:
$$[\phi(\textbf{x}), \pi(\textbf{x}')] = \int \frac{d^3p d^3p'}{(2\pi)^6} \frac{-i}{2}\sqrt{\frac{\omega_{p'}}{\omega_p}}\left([a^\dagger_{-p}, a_{p'}] - [a_p, a^\dagger_{-p'}] \... |
A paper concerning local sheet conductivity and sheet current density says the equation governing local transport $$\nabla \cdot \vec{j} = − \nabla\cdot(\sigma \nabla U) = 0,$$ where U denotes the local transport potential, can be rewritten as $$\nabla (\ln \sigma) \cdot \nabla U_0 =− \nabla ^2(U_0),$$ where $U_0$ is t... |
During particle-antiparticle annihilation, are the photons expelled perfectly perpendicular to the original direction of the particle-antiparticle pair?
There is very little information on the web about this topic, though I read a book awhile ago that stated that the photons are emitted from an angle, not perfectly per... |
Basically law of conservation states that input energy is equal to the output energy. But i was wondering that in case of generating electricity in dams no input energy is required. As the dam only collects the water and then the water is made to fall on the turbine from a height in order to generate electricity. But c... |
Why don't we consider incident rays which doesn't pass through the center or focus of a spherical mirror while drawing a ray diagram? Do those rays form any image when they intersect? like point a,b,c?
|
If I place a ferromagnetic body in external magnetic field it will be attracted to field, and hence, body will move in the direction opposite to magnetic field strength vector direction, yes?
If the first statement is correct, if I place a diamagnetic body in magnetic field, it will repeal, i.e. move in the direction... |
The particular dispersion relation for water waves or gravity waves dictates that waves with a longer wavelength travel faster than those with a shorter wavelength https://en.wikipedia.org/wiki/Dispersion_(water_waves). Which is very much clear from from $\omega-k$ plots. When we define group velocity we add sinusoids ... |
I've already seen this question, and it talks about any means in general. I just wanted to know if any chemical substances can be added to water to make it evaporate faster? Does addition of Edible Salt (Sodium chloride) make it evaporate faster? ( I just heard it).
|
The problem is the following:
Set up:
A sealed box contains a collisionless classical gas of particles, each of mass $m$. The box is
coupled to a thermostat such that interactions between particles and the box walls maintain
the temperature of the gas but which can otherwise be neglected.
The single particle distributi... |
I was wondering if there is a book (or a pdf) with all the conversion factors, equations etc., and also between different systems like all the conversions between the SI and cgs and so on.
It's so frustrating to forget some conversion factor and spend hours to find the right answer.
|
Let $\mathfrak n^\alpha$ be a vector density of weight 1. Define the covariant derivative $\nabla$ such that under a coordinate transformation $x^\mu \to \bar x^\mu$
$$ \nabla_\rho \mathfrak n^\alpha \to \left\lvert \frac{\mathrm d \bar x^\mu}{\mathrm d x^\nu} \right\rvert \frac{\partial x^\sigma}{\partial \bar x^\rho... |
As we know that wave functions are the solution of schrodinger wave equation which contains all the information about an electron. We also tought that these wave functions are the atomic orbitals of that electron. But my question is as orbitals are the region where the probebility to find the electron is maximum than o... |
Assuming a rod is set into vertical translation in the positive y direction, while being rotated around it's center of mass with uniform angular velocity: what direction will centripetal force act on? Will it depend on the orientation of the rod at that instant?
|
Motivation: I was wondering if by any chance gravity could not be a "non-force", but instead be a residual of all other forces that is generated when you put together a bunch of particles with slight imbalances.
Actual question: So I was considering how well the strong nuclear force go to zero and becomes negligible o... |
When reading about Superficial Degrees of Divergence (SDOD) I have seen in An Introduction to Field Theory (Chapter 10.1) that for Lagrangians with a $\phi^n$ interaction term we know that:
$$\tag{1} L=P -V +1,$$
$$\tag{2} nV = N + 2P,$$
Where $L$ represents the number of loops in a diagram, $P$ the number of internal ... |
At a high-level Wikipedia states: "A convolution between two functions produces a third expressing how the shape of one is modified by the other."
But there are clearly many ways of combining functions to get a third one. A convolution is a specific type of such combination; one that requires reversing and shifting on... |
In QFT, one is interested in studying functional integrals of the form:
\begin{eqnarray}
\langle \mathcal{O}_{1},...,\mathcal{O}_{n}\rangle = \int e^{\frac{i}{\hbar}S(\phi)}\mathcal{O}_{1}(\phi)\cdots\mathcal{O}_{n}(\phi)D\phi \tag{1}\label{1}
\end{eqnarray}
In Euclidean Field Theory, the action $S=S(\phi)$ can be assu... |
All the papers I’ve seen in black hole thermodynamics (e.g. arXiv:hep-th/9908022) define the electrostatic potential of a black hole with horizon Killing vector $\xi^a$ as
$$\Phi := \xi^a A_a \big|_{r \to \infty} - \xi^a A_a\big|_\text{Horizon},$$
where $A$ is the four-potential. Where does this definition come from? ... |
I'm a beginner at relativity, I have a question about eq 2 if its true. I know that the interval can be calculated like this in special relativity:
$$
ds^2 = \eta_{\mu\nu}dx^\mu dx^\nu \tag{1}
$$
where $\eta_{\mu\nu}$ is the metric tensor (for example the conventional $\text{diag}(-1,+1,+1,+1)$ in Cartesian coordinate ... |
I'm asked to compute the matrix elements $\left( x^i \right)_{nm}$ where $i=2,3,4$ and $x$ represents the position operator for the quantum harmonic oscillator. I know that for $i=1$:
\begin{equation}
(x)_{nm}=\sqrt{\frac{\hbar}{2m\omega}}(\sqrt{m}\delta_{n,m-1}+\sqrt{m+1}\delta_{n,m+1})
\end{equation}
I have already s... |
Why do we analyse the $stability$ (Stable, unstable, or neutral) of a body only under the influence of a conservative force? What if non-conservative forces are acting on the body as well?
For example, a marble rolling around in a round-bottomed bowl tends to move towards the bottom surface of the bowl and when it is ... |
I'm trying to find a statement and proof of the Hawking rigidity theorem for black holes, and I'm not having much success. The theorem basically says that given some assumptions, the event horizon of a stationary black hole is a Killing horizon. All the references I've found cite The large scale structure of space-time... |
I'm reading about the Operator Product Expansion in Gelis's A Stroll Through Quantum Fields section 7.4.2. As an example, he's using the product of currents
$$A_1^\mu = \overline{d}_L\gamma^\mu u_L$, $A_2^\mu = \overline{u}_L \gamma^\mu s_L.$$
He uses the fact that these currents are conserved at one loop order to say ... |
I'm studying for an experiment of measuring the lightspeed c. It will be measured following the rotating mirrors method by Fizeau-Foucault, using a HeNe laser.
I could understand - and visualize - the difference between phase, group and front velocities, in Wikipedia have some good stuff.
But there is some confusion ab... |
I know that work is the energy transferred by a force, and energy is the ability to do work, but I cannot contain my imagination to just that.
Does energy do anything else other than doing work? It seems to me that for energy to do just work doesn't seem to chime with me. I feel that there are other alternative uses of... |
Suppose $2$ photons move along the $x$-axis in opposite directions and collide head on. They fuse to form a single particle with rest mass $M$, which then decays to produce $2$ particles moving in opposite directions along the $y$-axis. The frequency of the electromagnetic wave associated with the photon is given as $f... |
In classical density functional theory, one traditionally calculates the chemical potential by taking the variational derivative,
\begin{equation}
\mu_{i} = \frac{\delta F}{\delta \rho_{i}}
\end{equation}
of the Helmholtz free energy
\begin{equation}
F[\rho] = \int d\textbf{r} f(\rho, \nabla \rho, ...) \textrm{.}
\end{... |
I recently read that in order to conduct electricity over vast distances via power lines they had to step up voltage which results in a decrease in current through the medium. This is reflected in the formula $P=IV$. What I can’t seem to grasp is why this results in current ($I$) dropping and not rather power ($P$) inc... |
I am reading on the BCS theory and the bogoliubov transformation to diagonilize the BCS Hamiltonian. And there is one step that I really can't seem to get.
So the Hamiltonian looks like this:
\begin{equation}H=\sum_{\mathbf{k} \sigma} \xi_{\mathbf{k}} c_{\mathbf{k} \sigma}^{\dagger} c_{\mathbf{k} \sigma}-\sum_{\mathbf{... |
Consider an electric circuit with a battery and a resistor connected through a wire of zero resistance. Since the wire offers no resistance, all points on the wire are at same potential, then why on earth does the electrons flow towards the resistor? And what if there was no resistor at all. Why would a potential diffe... |
I am a math student taking a course in General Relativity. I haven't taken many physics/applied maths courses before, so I am not sure if I can describe this question well, but I am slightly confused by a kind of usage of parameters. We use $c\tau=s$, where $\tau$ is proper time. In most cases, we have derivatives with... |
So AFAIK the objects that have been confirmed to be black holes by direct observation of the event horizon("black hole shadow"), like M87 for instance, also show observable evidence of frame dragging (the characteristic of a black hole with a Kerr metric). Now the thing about Schwarzschild black holes is that a point s... |
In the usual statement of the Particle in a Box problem, we assume two infinite potential barriers, to hold its wavefunction constrained, so it goes to zero on both ends:
But instead of invoking some unphysical infinite barrier, could be the case the wave just return to the same point. Using a simple warp drive(two pa... |
In section 6.2 (page 128) of David Tong's Lectures on QFT, Gauss' law is derived for the free Maxwell theory. The result of computing the Hamiltonian of the theory is (eq. 6.17),
$$H = \int d^{3} x \frac{1}{2} \vec{E} \cdot \vec{E}+\frac{1}{2} \vec{B} \cdot \vec{B}-A_{0}(\nabla \cdot \vec{E}).\tag{6.17}$$
I am comforta... |
Particles can be diffracted due to their quantum nature and that is understood by their wave-like behavior. Clearly seen in e.g. plane wave solutions of the Schrodinger equation or a superposition of states which can be seen as a wave packet.
Statistical interpretation tells that those wave functions are merely to des... |
I often see references to 'model building' in the particle physics literature, presumably to refer to creating new QFTs which go beyond the Standard Model.
How exactly does this process of model building begin? Does one simply write down a Lagrangian which has the desired properties and then alter it with trial and er... |
On this page, under the heading "Orbit Calculations": http://underactuated.mit.edu/pend.html or here.
The author says,
"This equation has a real solution when $\cos{\theta} > \cos{\theta_{\rm max}}$"
and then they give a piecewise function for $\theta_{\rm max}$.
I have no idea how these statement and function wer... |
Since the Sun emits X-rays, what would happen if we had a hypothetically planet sized x-ray film and exposed it behind the earth?
I understand we wouldn't be able to see the insides of the earth, but what about around the edges, what would it look like?
|
A student submerges one tip of a copper bar into a reservoir
of boiling water at 100 ° C and the other tip in a mixture of water
and ice at 0 ° C. Both bars are isolated. After the bar reached a
steady state, 0.16 kg of ice had melted over a certain period of time,
∆t. The water has a specific heat capacity of... |
Perhaps it goes without saying, but according to Newton’s laws “every action has an equal and opposite reaction”. How do astronauts, especially those inside small spacecraft like the Crew Dragon, not “push” the spacecraft when they bounce and push off walls? In orbit, where even button-sized ion thrusters push spacecra... |
Physicists Stephen W Hawking and James B Hartle 1 proposed that the universe, in its origins, had no boundary conditions both in space and time.
To do that, they proposed a sum over all compact euclidean metrics. I have heard that they only considered these metrics in order to simplify the calculations (since their aim... |
I am reading a paper(https://arxiv.org/abs/1906.03540) where a Balanced Homodyne detector is producing a homodyne signal that is the instantaneous change in the oscillator's frequency.
I know that a homodyne signal is proportional to either quadrature (x or p) of a field mode. Why it is the instantaneous change in osc... |
The correlation length for the two-dimensional classical ising model goes as
$$\xi_{ising}(T)\sim |T-T_c|^{-\nu};\qquad \nu=1$$
We can map the classical ising model to its quantum cousin, one-dimensional transverse field ising model or simply TIM. Jordan-Wigner transformation followed by Bogolibouv transformation gives... |
I've been transiently interested in the research of a Brazilian physicist named Fran De Aquino. The majority of his papers are related to gravity manipulation, which raises a lot of red flags. This man claims to have known the secret to anti gravity since the late 90's, and is employed by a college on Brazil as a profe... |
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