instruction stringlengths 31 24.3k |
|---|
I have a series of doubt about how Lorentz's Transformation are written and used commonly:
First doubt:
It's really common to see Lorentz transformation written this way:
$$x'=\gamma x -\gamma \beta t$$
$$t'=\gamma t -\gamma \beta x$$
where, $c=1$ in natural units. However, this way of writing Lorentz's Transformation ... |
Is there a limit on the minimum diameter that a collimated electromagnetic beam must have (lasers or masers), in terms of its wavelength, or it is possible to create a beam with its diameter smaller than its wavelength?
edit: removed the plane wave sentence, as it was a misinterpretation of the dynamics of a laser beam... |
The generating functional for a free complex scalar field theory is given by:
$$W[J,J^*]=\int D\phi D\phi^* \exp (i \int_{}^{} d⁴ x [(\partial_{\mu}\phi)^*(\partial^{\mu}\phi) -m^2\phi^*\phi + J^*\phi + J\phi^*] ).$$
In order to compute it one has to make the following change of variables:
$$\phi ^{'}(x)= \phi(x) + \i... |
In analysing photon diffraction by a single slit we add up a series of electric field phasors. Is there a similar method for analysing electron diffraction by a single slit?
|
Observables in quantum mechanics are described by Hermitian operators $\hat A: V \to V$, where $V$ is the Hilbert space of states.
Examples include the $x$-coordinate operator $\hat x$, the $x$-coordinate momentum operator $\hat p_x$, and the Hamiltonian operator $\hat H$.
The possible measured values are the eigenvalu... |
I'm just trying to understand the ultimate underlying dynamics of heat that causes temperature increase of, let's say, a liquid. Is it the electromagnetic radiation vector that moves between the fields and effects atoms? How can I exactly visualize this phenomena?
|
Before Hawking radiations were discovered, people said black holes had no temperature even though we could extract energy from them using the Penrose process (which also leads to a relation similar to the first law of thermodynamics).
Could someone explain to me why, when we thought that black holes could not radiate, ... |
In Leonard Susskind's video lecture on the Higgs Boson, he uses a model of a box made from very light, very reflective material containing photons, explaining how in this way, for example, the proton can get its mass. Would it be intuitive to think that a smaller container would make the box more massive due to more re... |
In physics, we often describe the dynamic properties of fields using variational principles like defining an action or a Lagrangian. A field however is simply some function of space $\phi(x)$ so I wonder what kind of properties the dynamics must follow to lend itself to description by an action principle?
For example, ... |
For $l = 1$ the angular momentum operator $L_z$ has the eigenvalues $\hbar,0,-\hbar$ and the eigenstates are then $|1,1\rangle, |1,0\rangle, |1,-1\rangle$.
Now, we can calculate the matrix elements of the $L_x$ and $L_y$ operators in the basis of $L_z$ eigenstates which is given by: $$\begin{pmatrix}|1,1\rangle\\|1,0\r... |
When dealing with the Dirac magnetic monopole from the point of view of the gauge theory, most authors consider a principal bundle over $S^2$ under the pretext of being homotopic to $\mathbb{R}^3 \setminus \{0\}$. I do not understand why homotopy guarantees the invariance of such treatment.
Appreciate.
|
Suppose a coin is placed on a turn table which is then rotated. The coin initially rotates along with the disk and may fly off eventually.
My question is, why is static friction acting radially inward and thus providing centripetal acceleration? I know it acts opposite to the potential direction of relative motion, but... |
It is well known that the pair correlation function of the zeros of the Riemann zeta function reproduces the correlation function of the random matrices from the Gaussian unitary ensemble (GUE). Usually, it is said that this is a connection between the zeta function and physics. Nevertheless, most of the uses of random... |
I have a question, that may sound a little silly. Suppose that I have an $n$-dimensional metric given by
$$dS^2=e^{2 A(r)}[-f(r)dt^2+\frac{dr^2}{f(r)}+\eta_{m n}\,dx^m\,dx^n]$$
with $A(r)$ is a warp factor and $f(r)$ is blackening factor. Besides the condition that $f(r_h)=0$ for the event horizon, what other condition... |
I don't understand the concept of a frame of reference. I've read from online sources and they defined it as an abstract coordinate system. What is the coordinate in this system then and how do they all connect to each other? Then I've read the mentioning of an observer and the observer's state of motion and I don't un... |
All modern derivations of statistical quantum mechanics I've found in the literature, have relied on the axiom, that the physical density operator is the one which maximizes the Von-Neumann entropy
$$ S=-k\cdot\textrm{tr}(\rho\log\rho)$$
under certain constraints. These constraints define different ensembles, e.g.
Mic... |
An insulated sphere with dielectric constant $K$ (where $K>1$) of radius of $R$ is having a total charge $+Q$ uniformly distributed in the volume. It is kept inside a metallic sphere of inner radius $2R$ and outer radius $3R$. Whole system is kept inside a metallic shell of radius $4R$, metallic sphere is earthed as s... |
As seen from outside the gravitational field of an object (a black hole, say) in (where the field is very weak) clocks inside the field are observed to run at a slower pace, the length of measuring rods to look shorter nearer to its source as the field is stronger compared to the field at the observer. Does this mean t... |
I am reading the book of Griffiths, Introduction to electrodynamics, and he explains in this chapter about the bound charge densities $\sigma_b$ and $\rho_b$
but I do not understand how is it possible that the term $\rho_b$ can exist. In my head I imagine that in the moment there is an external constant electric field,... |
I understand for a scalar field theory the integration measure is $\frac{d^3 k}{(2\pi)^3}\frac{1}{2\omega}$ because it has to satisfy the following equation
$$\int \frac{d^4 k}{(2\pi)^4}\delta(\omega^2-|\vec{k}|^2-m^2)\theta(\omega)\Phi(x,k)$$
Such that it is always on shell and has positive energies. Is there an equiv... |
I've read a lot of answers to the questions why the sky is blue. However all the answers I found contain mostly qualitative analysis: Rayleigh scattering is changing the direction of blue light, so there is more blue light coming to the eye along the line of sight than the red one.
However these explanations raise addi... |
This fantastic question essentially asks what is the noise floor of air? Both the answer given on that thread and the value stated by Microsoft are around -23 or -24 dBSPL.
However, overall loudness is only one metric. What does the amplitude of the noise in dBSPL look like when graphed out as a function of frequency i... |
I am trying to understand the solution to a problem in Altland & Simons, chapter 4, p. 183. As a demonstration of the finite temperature path integral, the problem asks to calculate the partition function of a single harmonic oscillator. The coherent state path integral is
$$ \mathcal{Z} = \int D(\overline{\phi},\phi) ... |
I've written in Matlab a code for a Ising model in 1 dimension with 40 spins at $k_{B}T=1$.
I record the energy of every step in a Metropolis Monte Carlo algorithm, and then I made an histogram like this.
I want to show the theoretical Boltzmann distribution. What is the exact formula to get this shape? $Ax \exp(-\bet... |
If i have a container like this (filled full with water):
and I unplugged the small tap, would the water pressure be big enough to blast the water to the right side of the container and cause an infinite flow of water like this?:
If you have a $3D$ printer, can you please print this .obj file, fill it with water (plu... |
I am trying to calculate the quantum Fisher Information of some quantum states which are represented via their P (Glauber-Sudarshan) representation,
$$\rho = \int P_\rho(\alpha) |{\alpha}\rangle \langle\alpha| d^2 \alpha,$$
where $|{\alpha} \rangle$ are coherent states. In order to do that, one option involves calculat... |
Roughly speaking, Quantum Electrodynamics tells us that electromagnetic fields are really made up of photons (so I'm told). What does a uniform electric field in a specific direction look like in terms of photons? The same question goes for a uniform magnetic field.
In other words, are the photons traveling small amoun... |
Context : I am not sure if this question belongs more in Math SE or here. In fact, my question is similar to that one, but I am dissatisfied with the answers. I think physicists perspective could be interesting.
Also, the question is not about symmetries in quantum mechanics or classical mechanics, but about the genera... |
How does the width or depth of a container of water affect the speed of an object (e.g. a toy boat) travelling on it?
|
I'm interested in a paper by Prof. E.E. Nikitin from $1962$. The reference from the book is:
"E.E. Nikitin: Opt. Spektrosk. $13$, $761$ ($1962$) [English transl.: Opt. Spectrosc. USSR $13$,$431$ ($1962$)]"
I haven't had any luck with either the Russian version or the English translation since the oldest volume on Spr... |
A rod AB of mass M and length L is lying on a horizontal frictionless surface. A particle of mass m travelling along the surface hits the end A of the rod with a velocity v0 in a direction perpendicular to AB. The collision in elastic. After the collision the particle comes to rest
(a). Find the ratio m/M
I just want ... |
I am currently studying Diode Lasers and Photonic Integrated Circuits, second edition, by Coldren, Corzine, and Mashanovitch. In chapter 1.2 ENERGY LEVELS AND BANDS IN SOLIDS, the authors say the following:
In gas and solid-state lasers, the energy levels of the active atomic species are only perturbed slightly by the... |
Maybe majorana fermions could exist but is very different from both quasi particle pair and particle hole pair, it could have both positive and negative charge in superposition until it is being measured, is this possible?
|
I don't think I understand the concept of sub-atomic particles very well. How can an electron or any sub-atomic particle have mass and spin if they are waves?
|
Let's assume that we have a positive charge $Q$ and a positive test charge $q$ is moved by an external agent from a point $A$ to $B$. The distance of $Q$ from $A$ is $r_1$ and from $Q$ to $B$ is $r_2$.
Let's say that the external agent moves $q$ from $B$ to $A$. It does some work while doing so. If it had moved the ch... |
As 75% of the Sun is Hydrogen and 25% Helium and the latter derives from 4 hydrogen atoms where half of protons that formed neutrons expeled positive charges as positrons that anihilated with nearby electrons, so half of electrons are missing too. In that case 12.5% of all electrons and positrons(protons) that are now ... |
Can anyone describe how free electrons move in a solid, like when an electron moves into conduction band does it permanently goes out or still exist around the atom.
When we say electrons it is being refered to electrons in conduction band right?
|
$$k^2g^{\mu\nu}-k^\mu k^\nu=k^2P^{\mu\nu}(k)$$
Here 1st term can be written as 2nd term via breaking square term and then raising index.
|
Is specific heat at constant pressure for an ideal gas has unit always Joule/kg-K or can be Joule/kg-°C specifically for ideal gas only?
|
I understand quite a bit of transformers, their structure and other concepts and formulas related to mutual induction. However I'm not able to explain why the electrical power has to be constant during stepping up and down of voltage. This will also help me explain why it is beneficial to transport current at high volt... |
Does a magnetic field moving relative to a stationary charge act on it?
|
Imagine that a point is space x can be characterized by either A,B,C,D,E,F,G in the c_A, c_B .. classifications of x as A,B,C,... My data gives:
P(x = A | c_A) = f_A(x)
P(x = B | c_B) = f_B(x) and so on.
What I want to ask is what x most probably is in this realization, given the probabilities that it can be all these ... |
I understand the definition of charge given by
$$ Q = \int_{\mathbb{R}^{D-1}} \text{d}^{D-1}x J^0. \tag{1}$$
In Carroll’s Spacetime and Geometry book (pg. 455) he writes
Start by imagining that we have a conserved current $J^\mu$, by which we mean
$$\nabla_\mu J^\mu = 0. \tag{2}$$
[...] we can translate the conservati... |
A mass $m$ is placed inside a frictionless tube of length $R$ which rotates with constant angular velocity $\omega$ around an axis to it perpendicular passing through one of its extremes. The mass begins at rest and accelerates outwards because of the apparent centrifugal force.
What is the velocity of the mass once it... |
So I'm aware of this and this, but the question is Are Hard X-rays and Gamma-rays the same thing?
If not, then what would be the key difference between them. Moreover, How much would the properties of each type differ from each other?
I'd appreciate a simple answer without much technicalities.
|
I'm reading the chapter about the renormalization group in Yeoman's book "Statistical mechanics of phase transitions" and I'm puzzled about how the author relates the scaling of the RG with the critical exponents. We have some RG map on the Hamiltonian $H\rightarrow R(H)$. We suppose that we are close to the fixed poin... |
This question came up as an exercise in my quantum text?
I typically find these "word" questions quite difficult. I want to answer:
"What is meant by the stationary states?" as concisely as possible.
I would say something along the lines of " Normalizable/(sufficiently smooth) solutions to the time- independent Schrödi... |
The definition of the intensity of light is given as
$$I=0.5\varepsilon_0n_0\vert E\vert^2$$
Now, when transitioning from one material with $n_1=1$ to another one with $n_2=2$ at a normal incident angle, I will have a reflection coefficient of
$$r=\left\vert\frac{n_1 - n_2}{n_1 + n_2}\right\vert^2\approx0.11$$
which me... |
I'm studying GR with Schutz' First Course in General Relativity and I have some trouble.
When field is weak enough, we can take such coordinate system that our metric is written as
$$
g_{\alpha\beta} = \eta_{\alpha\beta} + h_{\alpha\beta}, \ \ \ |h_{\alpha\beta}| \ll 1
$$
where $\eta_{\mu\nu}$ is Minkowski metric whose... |
I have been taught that Electric Lines of Force do not Intersect each other except at charges.
But then I came across this simulation: www.falstad.com/vector3de
While drawing Field lines in 2D we show no field lines in this plane but technically, field is zero only at the null point exactly at the centre if we conside... |
First-order phase transitions like solid-fluid can be understood as breaking of translational symmetry into lattice symmetry (also rotations into discrete rotations). The characteristic of these transitions are latent heat. In general the first derivative of the free energy diverges.
Second-order phase transitions can ... |
Most answers and articles I've read so far try to give real world examples such as a spring or a pendulum. However, I'm trying to understand the core difference between the two terms in the most fundamental context.
Do we need the term vibration if we can treat a point in space as if it oscillates but in much shorter d... |
The Lagrangian for the motion of a particle with mass $m$ and charge $q$ in a constant magnetic field $B$ is given by $$\mathcal{L}(x,v)=\frac{m}{2}\left|v\right|^2-\frac{q}{2c}\left(v\cdot[x\times B]\right).$$
Show that rotations around the $B$-axis leave the Lagrangian invariant, where each rotation is given by $O_{... |
An observer and an object are in a closed container.(the object is tied to a string.)(the container is something like an elevator;not precisely an elevator). First the container is on earth and then it is raised high up. Then the whole thing is released under gravity. During the fall the object is cut from the string t... |
In quantum physics, the relation
$$
\int_{-\infty}^{\infty} (\psi[x,t]^*)(\psi[x,t]) dx=1 \tag{1}
$$
is paramount. What would the consequence be of defining the normalization condition as
$$
\int_{-\infty}^{\infty} \sqrt{(\psi[x,t]^*)(\psi[x,t])}dx=1 \tag{2}
$$
Of course, it goes without saying the mathematics will now... |
Why is the impedance of the inductor defined as $i\omega L$, and of the capacitor $\frac{1}{i \omega c}$ ? More generally, why are they complex numbers? Is impedance a mere mathematical tool?
|
Okay, so I have an idea and I wanted to know if it works out or not.
I imagine a black hole to form from a star, which is rotating. Let's say the star collapses because of some reason, and a black hole forms. While it is collapsing, it is spinning faster and faster (just like a dancer when they move their arms closer).... |
I want to learn lattice QCD by myself, but I don't know how to start. Can you recommend some books for lattice QCD?
|
For an Green function/partition function:
$$\int D[\phi]e^{\frac{i S[\phi]}{\hbar}}$$
We can make saddle point approximation and gives classical configuration:
$$\delta \mathcal{S}=0\Longrightarrow \phi_{cl}.$$
I can understand that when $\hbar \rightarrow 0$ (or other equivalent control parameters), the configurations... |
I do not understand this piece of my professor's lectures about the calculation of wavefunction of an electron inside a cubic semiconductor with side length L.
It expresses the solution of the Schrodinger equation in this way:
\begin{align}
\Psi_k(r) & = A_k(r) \sin k_xx \sin k_y y \sin k_z z
\\ \text{with} \qquad
k_x... |
Is it true that varying electric fields create varying magnetic fields only for higher frequencies? Why is this so? Correct me if I am wrong about this.
|
(If any of the following steps are wrong, please correct me)
The well known relationship, generalized for anisotropic materials, relate the electric displacement field with the electric field and the polarization field like so:
$$ D_i = \epsilon_0 E_i + P_i $$
which, by using the dielectric permittivity $\epsilon$ will... |
We know that in the Schrödinger picture, operators are time-independent if they do not have explicit time-dependence.
So do electric field and vector potential field operators have time dependence in Schrödinger's picture?
I ask this because, in canonical quantization of EM theory, this point is never addressed, after... |
The electric field across a boundary is discontinuous. Does this mean there is no field at the boundary? Can you explain if there is no electric field there, the work done across the boundary?
|
I am looking for more recently-written works (either major papers or review articles) on holographic superconductivity, preferably from 2019 or 2020. The main reviews I know are the following:
Sean A. Hartnoll, Christopher P. Herzog, Gary T. Horowitz, "Holographic Superconductors" (2008)
Gary T. Horowitz, "Introduction... |
I have learnt that an even number of fermions can behave like a boson, with a net integer spin.
Am I correct in thinking that this is only true on scales where the distance from the composite particle is much greater than the separation of the fermions in the composite particle, and that if we 'zoom in' we can no longe... |
In the nearly free electron model, we assume that the potential is weak.
Now, in a book by Rudolf Gross and Achim Marx, it states:
I know that the text is in German, but bear with me: The relevant passage is that we assume a "constant potential $V_0$". Two pages later, they have the following diagram:
What really conf... |
It took me some time after my Group Theory lecture to really start to understand how to apply all the mathematics in physics, in particular with respect to the quark model. I am currently reading the book "An Introductory Course of Particle Physics" by Palash B. Pal (pp. 201-227 for isospin symmetry and pp. 254-297 for... |
When we derive the existence of anyons in 'r-space' where r = r1 - r2 and r1 and r2 are the parameters describing two particles called '1' and '2', we remove the point r=0 so that 'the two particles do not ever occupy the same position'. However we know that bosons can occupy the same position, so why do we force this ... |
I have spilled around one liter of water to wooden floor. I'm afraid wood will deform and pop out.
What would be quickest way to dry it? I have wiped out what I could, but some water passed between the planks.
Conditions: It's summer time. Outside temperature is 19 degC, relative humidity is 85%, dew point is 16 degC. ... |
I am very new to physics and I want to pursue Unified Field theory now when I read about how to unify quantum mechanics with relativity as they are essentially the same thing and a relation must be found I read that this can be done by unifying to he forces now I have not studied the math so if someone could explain to... |
How to prove that
$$k=(\frac{\omega}{c} , \vec{k})$$
is a four-vector?
Where $\omega$ is the frequency and $\vec{k}$ is a wave vector.
|
I know that the Fubini Study metric for the $SU(2)$ coherent state is the metric on $CP^1$. The $SU(2)$ un-normalised coherent state is given by
$$
\mid z\rangle=\sum_{m=-j}^{m=+j}\sqrt{\left(
\begin{array}{c}
2 j \\
j+m \\
\end{array}
\right)}z^{j+m}\mid j,m\rangle
$$
The normalisation is
$$
\langle z\mid z\rang... |
Does a fan cool objects? I have a ceiling fan in my office which really helps to keeps the room cool. Does it also cool down vitamins in a plastic bottle with a screw on top? My office can get very hot which is probably not good for them. I keep them in my office to remember to take them. :-) I leave the fan going ... |
As I understand, intrinsic silicon, as opposed to extrinsic, means undoped silicon that has no added donors or acceptors. The diagram bellow, taken from the book The PN Junction Diode (George W. Neudeck), represents the energy band diagram for a p-n junncton
and as we can see $E_i$, the intrinsic energy level, is repr... |
Can the shape of curved space time under influence of mass be closely modelled by any function?
Like, without getting into tensors and Euclidean/non-euclidean geometry, can I make a function (in one dimension), something of the form $y=ax^n+...$ to closely tell the curvature of space time?
|
I'm looking for a review articles that explaining the issues with runaway potential in cosmology inflation, when a potential has a hilltop and then it goes to zero at infinity. I read somewhere that that if the universe start at a big bang (r->inf) and the expansion start climbing the potential to the hilltop ( if it h... |
I've seen 2 (or 3) definitions for stationary current.
Definition 1:$\quad\frac{\partial}{\partial t}\rho = 0 $ or $\nabla\cdot\mathbf{J} = 0 $
This means, as expected, that the current throught an arbitrary closed surface is $I = \oint \mathbf{J}\,d\mathbf{S} = 0$. If we consider an infinity cylinder (a wire) we conc... |
In equation 6-38 on page 176 of the book "Student Friendly QFT" by Robert D. Klauber it is said that the partial derivative w.r.t. time of a multi-particle state is equal to zero since we are working in the Heisenberg picture: http://www.quantumfieldtheory.info/website_Chap02.pdf
How do we know that we are working in t... |
I hope I'm asking in the right place!
I worked with automated TIG (GTAW) welding equipment. I'm confused about how the welding power supply controls the current applied through the work piece. If the entire circuit was a simple static load, with a known resistance, it makes sense that voltage across the load could be c... |
I do not clearly understand some concepts, so maybe someone will clarify this for me.
Imagine we have a random wavefunction for an electron, it could be anything.
How can I with known wave function calculate the value of spin of electron? I mean I know that we cannot exactly know with 100% would it be spin up or spin ... |
I am studying the Zeeman effect for spin-orbital coupling and there is a section which i do not fully understand:
In case of a weak magnetic field we can show that no splitting occurs by calculating the Lande $g$-factor and the zeeman energy for the spin-orbital coupling.
I know both formulas regarding zeeman energy an... |
A common derivation of the Lagrangian of a charged particle in an electromagnetic field starts with the Lorentz force that is rewritten in terms of the electromagnetic potentials $\Phi(\vec{x})$ and $\vec{A}(\vec{x}, t)$. So $\vec{F} = q(\vec{E} + \frac{1}{c}\dot{\vec{x}}\wedge\vec{B})$ becomes
\begin{align}
\vec{F} & ... |
In a discussion with a friend, he seemed to be saying that reflection of light happens because of the difference in refractive index between two media, implying that that is the only reason reflection ever happens.
Now, I understand that when light crosses an air/glass boundary, some light is reflected because of the c... |
In the context of solid state system, the spin-orbit (SO) coupling from low-energy expansion of Dirac equation is
$$H_{SO} = \frac{1}{2 m^2 c^2} (\vec{s}\cdot (\nabla V \times \vec{p}))$$
My question: I saw people treat SO as a gauge field on the link of the lattice in effective field theory, which I'm very confused ab... |
I was listening to an interview with Brian Cox and he mentioned that gamma-gamma scattering is when two photons "bounce off" each other and it occurs at "sufficiently high energy."
What sort of "high energy" are we talking about? Meaning, is there any natural occurrence in nature (say something like quasars) that is "s... |
I learned that the electric and magnetic field of a TEM wave cannot have components parallel in the direction of travel. I am working on a problem in which the TEM wave has a component in the $z$ direction but travels in the $x$ and $y$ directions. I used a well-known formula to calculate the electric field from the ma... |
I suspect that a vacuum pump's head is related to its absolute vacuum pressure but I can't find a straight answer as to how, so here is an example that demonstrates what I am asking. Say I have a 3 CFM two-stage vacuum pump that has an absolute vacuum pressure of 22.5 microns (which is .0225 torr if I am not mistaken, ... |
A high $Q$ cavity means that the light will travel between the cavity mirrors many times before leaving the cavity. The more times the light reflects, the longer the gain medium effectively extends.
It seems to me that a high $Q$-factor is always better. Is there any drawback of a ultra-high $Q$ cavity, especially for ... |
There are magnetic and electric fields outside the DC circuit wire. The fields are static and separate. Energy is stored in the fields. There is a low amount surface charges, and to detect the surface charges requires high voltages. The magnetic fields can be used for application. If the circuit is in a vacuum the... |
The inductance $L$ of a long solenoid of length $\ell$, cross-section area $A$, and turns per length $n$ is given by:
$$
L = \mu_0 n^2 \ell A
$$
where $\mu_0$ is the magnetic constant.
I am currently attempting to derive this from Ampere's law and Faraday's law. Using Ampere's law, I have been able to show that the mag... |
I have a very simple question I am struggling with. Lets say I want to propagate the error for some expression $$ y = x^2$$
Lets say I known that $x = 0 \pm 100$. Using standard error propagation I get that $$\sigma_y = 2x\sigma_x$$
This means that the value I get $$y = 0 \pm 0$$
Which I find very counter-intuitive. I ... |
I have read Witten's paper, and I am interested on computing the expectation value of a Wilson loop with a representation $R$ on Chern-Simons theory in $d=3$. I am especially interested in cases for $G=SU(N)$, and spaces of the form $\Sigma \times S^1$. I understand, from section 4, that the way to go would be to start... |
A uniform top of mass $M$ with its lower end fixed to the ground is rotating on its axis of symmetry with angular velocity $\Omega$, initially in a vertical position ($\theta=0, \dot \theta=0$). The main moments of inertia are $I_3,I_1=I_2$. The center of mass is located at a distance $a$ from the bottom point of the ... |
Suppose I have a bipartite pure state $\vert\psi\rangle_{AB}$. By the Schmidt decomposition, we know that the reduced states $\rho_A$ and $\rho_B$ have the same eigenvalues. I am now interested in applying a projector on subsystem $B$, where I project onto some smaller subspace of $\mathcal{H}_B$. On the full state, th... |
Einstein gave us the mechanism to explain how gravity works. (Namely that mass curves (or warps) space-time.) Do we have any theories for the "mechanism" as to how masses warp space? Is it related to the Higgs field?
|
Suppose the follow Lagrangian density:
$$
\mathcal{L}[x,t]=\sqrt{\phi[x,t]^*\phi[x,t]}
$$
The Euler-Lagrangian equations with respect to $t$ yields:
$$
\begin{align}
0&=\frac{1}{\sqrt{\phi[x,t]^*\phi[x,t]}} \left(\frac{\partial}{\partial t}(\phi[x,t]^*\phi[x,t])\right)\\
&=\frac{\partial}{\partial t}(\phi[x,t]^*\phi[x,... |
Flat 1x1 meter plate. Heat source indicated by red arrow. The rest is in space. No sun exposure at all.
Some of the photons will exit through the gaps between plates. No problem. My question is about the photons that do make it from plate to plate.
One photon leaves the first plate and is received by the second. ... |
The existing model predicts it should have no mass but observation says otherwise, it is known that the neutrino can change flavor over time but how does it qualify as a composite particle? Does it impliy that a neutrino consists of many unknown particles that like to stick together but each is vibrating at a different... |
Inspired by the Phys.SE post Geodesic Equation from variation: Is the squared lagrangian equivalent? I was wondering if it is always the case that the square root of a lagrangian gives the same equations of motion as the lagrangian itself? Are there specific counterexamples, or is there any way to derive a set of condi... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.