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This is the setup of a Physics HL paper of past year:
I would like to understand the model underlying this problem.
From the solutions I can find worked out in that video for instance, this is the only way it can make sense:
the problem considers air as an object of a certain mass that gets accelerated from rest to a... |
One of the postulates of quantum mechanics is that, given a quantum state $\psi_{0}$ at time $t=0$, the state of the system at a posterior time $t > 0$ is given by $\psi_{t} = e^{-iHt}\psi_{0}$, where $H$ is the Hamiltonian operator of the system.
The operator-valued function $\mathbb{R}^{+}\ni t \mapsto U(t) = e^{-iHt... |
A puck is released from the top of curved, frictionless track. The puck descends, then rises again at the end, such that it leaves the track and continues in free fall until hitting the ground. The ground is assumed to be a plane on the same level as the exit point from the curve.
Question
Does a brachistochrone such a... |
A standard window glass shows exactly what is on the other side of the glass. If the watcher changes the angle or the position of their eye, the image they see changes.
I know there is a tool which lets you create a similar effect, but without actually putting anything on the other side of the glass. It's called mirror... |
I've been studying chemistry (I know this is a physics page) and I've read that electrons are supposed to lose energy because they are moving in an electric field (I know this is not actually happening).
My question would be why are they supposed to lose energy? It is because they are attracted toward the center of the... |
When you calculate the gravitational force $F_G = G \cdot\frac{m\cdot M}{r^2}$.
Is this equation precise for relativistic big masses, given that $m$ and $M$ do not and can not move?
If not is there an "easy" accurate equation?
What does not moving mean:
I am interested in the force purely caused by the existing masses,... |
The cosmology calculators I've been playing with have $\Omega_\Lambda$ and $\Omega_M$ as their main parameters, and calculate $\Omega_k$ with that.
Are there parameters for FLRW models that don't predict a finite age of the universe, and/or have lookback times that grow unbounded?
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I am learning the relationship between Schrödinger and Heisenberg pictures. I have a question about how to compute the time-dependent Hamiltonian with the form
$$H=\frac{p^2}{2m}+V(x,t)$$
in the Heisenberg picture.
To define notation clearly, I use $H_H(t),p_H(t),x_H(t)$ to denote quantities in the Heisenberg picture, ... |
I'm currently in a NMR lab for an undergraduate physics class, and I am attempting to determine the decay constant $\tau$ (e.g. $T_2$) associated with a free induction decay signal. However, our instrument has a periodic background noise present, which limits my ability to determine the decay constant. An approximation... |
I am working on a project on which I need to calculate the geomagnetic field in different coordinates. When I use the conventional form of the dipole field in spherical coordinates:
$$\vec{B}_{r,\phi}=\frac{B_0 R^3}{r^3}(-2 \cos \phi\, \hat{e}_r- \sin \phi\, \hat{e}_\phi),$$
with $B_0$ as the field intensity in the equ... |
Since short circuits have >1 electrical pathways for current to flow, the unintended and intended pathway, I would assume that short circuits are parallel circuits and therefore current is distributed to the unintended and intended pathway based on the ratio of their resistances?
|
I was reading this notes about chemical potential. I am confused about some things in section 2: Potential energy and the chemical potential
Let us look at two systems A and B a the same temperature that may exchange particles, but the two systems are not yet in diffusive. We assume that we start from $\mu_B>\mu_A$ so... |
I am new to aeronautics and I am interested to know how can the section of an aerofoil be determined just by looking at its lift-to-drag ratio against angle of attack ( $C_l/C_d$ as a function of AOA).
Specifically, I would like to know:
What are the key characteristics that experts look for when analyzing the $C_l/C_d... |
Why is it proper to assume the electronic velocity after collision is zero in Drude's model?
(Where are momentum and energy conservation?)
|
while I was watching a derivation of angular momentum of a rigid body on youtube, it came to my attention that the person who was doing the derivation, used $\Delta m$. my question is, why did he use delta m? I mean even if a force is applied to a rigid body, mass remains the same. delta means change right? but mass d... |
I had read it somewhere that on the space station, people are weightless. even though artificial gravity is created there, people are still weightless. how can this be possible if there is gravity, even if it's created? to make a person weightless, shouldn't gravity be zero?
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I have a figure of the electric field lines of two point charges as above. I have a question, do photons follow electric lines of force, then "collision" with negative charges and create an electric force?
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I and my friend noticed a strange behaviour of a rotating disc (or a cylinder) and we don't know how is that happening.
This is the video.
Actually what is happening in the video is that the disc wobbles (the rotational axis precesses about the vertical) a bit and then it stops wobbling (the rotational axis coincides w... |
While I was reading a proof on Newton's Shell Theorem, an idea struck my mind. It was that if there is a 2-D ring of mass $M$ and radius $R$ with constant linear mass density and we keep a point mass $m$ anywhere inside the ring other than it's center at a distance $r$ away from it, then what would be the net gravitati... |
For visible light, we are able to use mirrors to focus on what we want.
However, gamma rays' wavelengths are too short and can't see solid objects.
So how do scientists focus high-energy electromagnetic waves onto a target and what would they use for such a process?
|
I'm reading Tong's notes on GR http://www.damtp.cam.ac.uk/user/tong/gr.html and i cannot understrand how he derived the equation that relates the varation of the metric with its inverse in page 141 under equation 4.2.
A different approach could be that
$$g_{\mu\nu}g^{\mu\nu}=d \to \delta g_{\mu\nu}g^{\mu\nu} = -\delta ... |
I came across this question online, and I was just thinking how to find the transverse voltage ΔV. If we divide the large semicircular strip into very thin semicircular strips of width dx, then the outermost strip will have more resistance than the innermost one, due to its longer length. But does this mean that the c... |
When a positively-charged rod is brought near a neutral insulated metal sphere, the electrons on the sphere will be attracted to the side of the sphere that is near the rod, leaving protons on the other side of the sphere away from the rod. Since protons cannot move, how do we explain this phenomenon?
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The Zeeman effect is the change in energy of a system with a permanent magnetic moment in the presence of an external magnetic field. Consider electrons for example. In general, in $B \neq 0$ electrons with $\mu$ aligned with $B$ will experience an increase in energy, while electrons with $\mu$ antiparallel to $B$ will... |
1.Ionization energy equals minimal energy electron needs to overcome atom’s Coulombs and gravitational fields.
Ionization energy depends on which state atom currently is. For ground state ionization energy highest. For every next states it is lowering.
So, if atom is not at ground state it needs less energy to be ioniz... |
It is generally accepted that a closed shell structure is a very good picture for inert atoms. But how good is it quantitatively? Suppose we do both the Hartree-Fock approximation and the (in-principle exact) configuration-interaction for an inert atom, how close to each other are the results? How close is the exact gr... |
In Zwiebachs "A First Course in String Theory" 2nd edition he states in chapter 25.2, that
"the amplitude for an initial state consisting of a $\phi$ particle to turn into a final state consisting of the two outgoing $\chi$ particles is
$$_\text{out}\langle p_1,p_2|p\rangle_\text{in} = -i(2\pi)^4\delta(p-p_1-p_2)T(p,p... |
In Fourier optics one decomposes the field into plane waves to find the solution of the scalar Helmholz equation. The scalar means that the electric field $\vec{E}$ is aligned towards only one direction.
The direction of a plane wave is given by the vector $\vec{k} = (k_x,k_y,k_z)$.
For transverse waves $\vec{E}\perp\v... |
Consider the geometric length of a magnet to be $L$ and magnetic length to be $L'$.
Some sources claim that $L'$ = $(0.84)L$.
One such claim can be found here:-
I cannot find any good reason to be satisfied with the expression. Is the above equation true for all cases? If so why?
|
Let me explain you why I am asking this question.
The other day I was studying about power factor correction of a (step up or any) transformer. It said that on the output side of transformer's secondary, when the voltage is higher, there's no current flowing because of highest impedance, and when voltage starts to reve... |
We represent light by a ray. Again,we know light which is emitted from the sun has all seven colors in them,hence again seven light rays. So doesn't it mean that that light is again composed of $7$ rays? Why do we represent it by a single ray then? I beg pardon if this doesn't make any sense but i am confused by light ... |
For a particle in a box, where the walls of the box have a finite (i.e. not infinite) potential
energy, what is the expectation value of the momentum of a particle which has tunnelled
through the wall and has escaped?
|
According to Wikipedia Zwicky used "virial theorem" to discover the gravitational anomaly in the Coma Galaxy cluster. But I also remember reading that he used Kepler's third law. Which one is correct?
|
There are different approaches to solve the many-body problem of an open-quantum system. Just to mention two methods, there are the Equations Of Motion (EOM) and the Hierarchical Equations Of Motion (HEOM) methods. While the first one focuses on solving the Green´s function of the system, the latter solves for the den... |
Suppose we have a two-loop graph that looks like two balloons next to each other or stacked on top of each other. What are the symmetry factors of these graphs?
Note that I'm trying to compute a two-point function, so I don't need to consider the symmetry of the external lines. My intuition tells me that these both sho... |
I am currently reading the TASI Lectures on Inflation 1. Deriving the Friedmann equations one gets (with $c = 1$)
$H^2 = \frac{4\pi G}{3}\rho - \frac{k}{a^2}$.
But when talking about inflation with one scalar field, the last term is dropped (on page 32). This term is negligible for large $a$, but I dont see why this as... |
I have read that Kelvin-Planck statement and Clausius statement are equivalent. The problem I have is that Kelvin-Planck statement does not deny the possibility of a non-cyclic process where the net result is complete conversion of heat $Q_H$ into work $W$, like the case of an isothermal ideal gas expansion. Couldn't t... |
As I understand in the deep inelastic scattering process, a collision of electron beams and protons occurs, resulting in a scattered electron. However, when the proton absorbs the virtual photon emitted by the electron, it gains more energy and mass by generating sea quarks and gluons.
But this energy can't just disapp... |
In lecture, we discussed electron shielding as an additional influence in the interaction between electrons and ions.
My understanding of shielding is that because of coulomb force, electrons have a higher probability of being near a nucleus (instead of being homogeneously distributed across space) and therefore shield... |
Are there spacetimes or metrics where symmetries (like Poincaré, Lorentz, diffeomorphism, translational... invariances) are only local and the symmetries of one local neighbourhood are not, a priori, the same for another, even close to it? I mean spacetimes with "local neighbourhoods" which are not diffeomorphic to eac... |
Let $\rho$ a density operator $\rho: H \to H$ representing a mixed state, with $H$ Hilbert space. The operator $\rho$ (together with its corresponding matrix) represents a mixed state; when it additionally satisfies the property $\rho^2 = \rho$, then it is a pure state.
In any case, I was wondering if $\rho^2$ has any ... |
To see an object, its light rays have to meet on the retina in the focal point. But the focal point is a small white dot. Basically nothing would be distinguishable and the retina would burn because all energy is concentrated at a single point? Obviously, this is not happening. But why?
|
I am reading Sakurai and the free particle solutions to the Dirac equation. For the positive energy solution, one of them is:
$u_R(p)=\begin{pmatrix} 1 \\ 0 \\ \frac{p}{E_p+m} \\0\end{pmatrix} $
He then says that the 3rd component is small in the non relativistic limit, and then ignores it in what follows.
But my quest... |
Consider a one parameter family of curves with curve parameter $\lambda$. We denote the deviation vector $W^\mu=\frac{\partial x^\mu}{\partial \epsilon}$ where $\epsilon$ can be thought of as the transverse coordinate. In this scenario the relative acceleration of the geodesics
$$
A^\mu=T^\omega\nabla_\omega T^\nu \nab... |
I'm getting my feet wet with orbital mechanics and have a very basic question. Kepler's 2nd Law shows that 2 objects in an elliptical orbit sweep out equal areas in equal time, implying objects increase in velocity as they get closer to one another.
This makes sense to me re: inverse square law of gravity - as distance... |
Long-duration cryopreservation of biological tissue (most often semen, egg cells, or fertilized embryos) is typically done at 77 K, since the samples can be easily kept at that temperature by immersing them in liquid nitrogen. As tissues are cooled down to that temperature, they pass through one of two different phase ... |
Classically it is explained by E and B fields.
However, my question is in QFT where the polarization of a photon is encoded as a vector (left or right handed in the direction of motion; in other words +1 or -1): how does the polarization (or a superposition of polarizations such as linearly polarized) of a single photo... |
Suppose we are calculating the two-point function $\langle\phi(x_1)\phi(x_2) \rangle$ and we've obtained a loop diagram of the kind on the left. Will there necessarily also be a diagram as on the right? Or is this part of the symmetry of the one on the left? I know in correlation function calculations that the external... |
As a student you are typically told that Maxwell's equations (ME) in vacuum are linear. However, it seems that for extremely high electromagnetic fields the equations for electromagnetism turn out to be nonlinear. I think examples are super-strong laser pulses (even if the precise mechanism is unclear to me).
How is th... |
I am interested in studying (squeezed-state light in integrated-photonic devices by means of four-wave mixing). I would like to be completely familiar with the working method and all the devices that are active in this process.
Is there a website or an article to fully understand how this system works that will provid... |
Is every Quantum Field theory, including CFTs, an Effective Field Theory?
Can every interacting CFT become the infra-red fixed point of some high energy QFT?
|
Solid state detectors are based on semiconductors and in particular on silicon pn junctions.
When a pn junction is reverse polarized, a significat portion of the semiconductor is depleted of free charge carriers. Ionizing radiation that deposits energy within the depletion region generates a number of electron-hole pai... |
Consider adding angular momentum. Shankar describes the state of the system as the direct product of states while Ballentine (and I think most other people) describes the state of the system as the tensor product of states. I assume Shankar isn't straight up wrong. Thus, I am a bit confused.
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Amorphous ice is often produced by cooling liquid water below its glass transition temperature so fast that it does not have time to form ice crystals. The fact that this can only occur if the temperature change is fast suggests to me that amorphous ice is unstable and results in the system getting "stuck" at a local b... |
I was reading this thread and I'm a bit confused. The answer says negative probabilities can account for destructive wave interference and the events cancelling out. But if events just cancel out, shouldn't that make the probability zero? Why would it be negative?
Additionally, my (possibly incorrect) understanding ... |
This semester I'm taking Quantum Mechanics II and we are in the theory of angular momentum. One particular thing got me thinking: when one does the representation of the rotations of the $SO(3)$, a direct result is that the components of the total angular momentum are the generators of rotation. Is this a purely mathem... |
I have had this thought for a while and I was wondering whether it's valid.
Entropy is often described as the amount of "unuseable*" energy in a system
at a micro level, entropy is related to the number of states that can be reached
If we know the trajectory of a system, we can theoretically extract work from it.
Equa... |
I am wondering if could it be possible that the Universe is expanding in some areas while contracting in other areas.
I have wondered if perhaps as one area of the Universe is squeezed inward by some force, a force such as dark energy, all the matter that is within that squeezed space is flowing outward in all directio... |
I am studying MRI, specifically spin echoes.
Now I kind of understand how magnetic resonance imaging works, but what I'm stuck is the definition of "degree" in MRI. What I thought was that if I say "90-degree RF pulse," I fire an RF pulse perpendicular to $\mathbf{B}_{0}$, so the magnetic field and RF coils inside an M... |
I just covered the rejection method with students in an optimization course. Naturally, I mentioned the benefit of the rejection method when you receive e.g. empirical data from a research team with a statement like "nothing is known about probability distributions and their parameters, and all we can provide are the d... |
A rigid body (i.e., a 2-dimensional object) has principal moments of inertia about the centre of mass of $I_1 = (\mu^2 -1), I_2 = \mu^2 + 1, I_3 = 2\mu^2.$ I wish to show, using the Euler equations, that, in the body fixed frame, the component of angular velocity in the plane of the lamina (i.e., $\sqrt{\Omega_1^2 + \O... |
For context, I was looking at the definition of the operator postulate from hyperphysics given here, which matches up pretty well with how I remember Griffiths explaining the definition of an operator in QM in his QM text.
I got confused part about this part:
The mathematical operator $Q$ extracts the observable value... |
In high temperature cuprates phase diagram there are different phases namely pseudogap and strange metal. Why do we call them pseudogap and strange metal regime?
|
If the electric field on a closed region is uniform then by Gauss's law you have $0=\nabla\cdot\vec{E}=\rho/\epsilon_0$, so $\rho$ would be zero.
Is the converse necessarily true? Could we conclude that the electric field is uniform when $\rho=0$?
|
Has anyone figured out a way to recycle specifically the energy used to power electromagnets? Since for many applications, the Bfields required are extremely high magnitudes, the currents must match to enforce that. That is a lot of power being used and I would imagine that's probably where most of the energy expenditu... |
Suppose we have a theory with conformal invariance that has been extended to a diffeomorphism invariant theory in a way that the resulting energy-momentum tensor is traceless on-shell (which can always be done, as e.g. explained in my answer in Relation of conformal symmetry and traceless energy momentum tensor). In ge... |
When we spin a top (give it kinetic energy $K_0$) and place it on a table, it starts precessing around the vertical axis.
Is the total energy of the spinning and precessing top equal to the initial spinning energy $K_0$?
If your answer is a Yes, please explain how the energy transfers from spinning axis to precession a... |
In such a container, a liquid with density $\rho$ is filled to the brim. I have to find the net force exerted on the walls. Since the horizontal component cancels out, only the vertical components remain which acts upwards here. I have figured out the answer to be conclusively $$F_y=\frac{5R^3\pi\rho g}{3}$$ by taking... |
NOTE: I only wish to understand the underlying concepts and visualization aspects. I do not by an intention mean to seek a complete worked out solution for this answer.
In the diagram shown, the mass of the [man + block] $A$ is $10$ kg and of block $B$ is $5$ kg. The coefficient of friction under both the blocks is $.... |
Why are Euler angles used when describing the rotation of a rigid body instead of angles around the principal axes of inertia? What exactly is the benefit of introducing Euler angles? They seem not like a "natural" choice but they are the standard way to handle rigid body rotation in classical and quantum mechanics.
I ... |
I wonder what the time scale to demagnetize a fully magnetized permanent magnet with an external magnetic field is. The temperature is assumed to be constant.
I found a reference 1 for specific cases, the time scale for a full magnetization reverse is $10^{-9}$ sec.
But I do not know how to apply the method to real per... |
https://www.youtube.com/watch?v=xJzrU38pGWc&ab_channel=mehranshargh
"I might say that my recent work has been very much concerned with Einstein's general relativity and I believe that the Times and Distances which are to be used in Einstein's General Relativity are not the same as the Times and Distances which are pro... |
I am new to study MRI. Please understand if some terminologies I use are wrong.
This might be a silly question, but I wonder why water is bright in a T2 weighted image. T2 relaxation is also called spin-spin relaxation, because FID signal decays faster when there is spin-spin interference. Then water must be denser in ... |
Consider the hamiltonian of a ferromagnetic finite Heisenberg chain for spin $1/2$ of $N$ sites:
$$\hat{H} = -J \sum_{j=1}^{N-1}\hat{S}_j \cdot \hat{S}_{j+1}.$$
If we fix periodic boundary conditions, that is, we add the term $J\hat{S}_1 \cdot \hat{S}_N$ then the Bethe Ansatz gives the solutions that has been known for... |
We measure an angle to be -55 degrees (2 sigfigs).
Let us take the sine of this angle. We get sin(-55) (2 sigfigs). Now, since sin(-55)=sin(305), then we can also take the sin(305) (3sigfigs). Now, since sine(305) is just sin(3905), then we can also take sin(3905) (4sigfigs) and so on. In this manner we can get a preci... |
Is there a significance or an important interpretation of the fact that the plots in the Fermi-Dirac distribtion graph, all intersect at the point with coordinates ($\epsilon_F$,$\frac {1}{2}$)?
https://www.researchgate.net/profile/Pradip-Basnet-2/publication/280311898/figure/fig2/AS:614251689418778@1523460423753/Fermi... |
I'm looking at this article from Scientific American: https://www.scientificamerican.com/article/star-wars-science-light-speed/#:~:text=Normal%20humans%20can%20withstand%20no,heavier%20blood%20to%20the%20brain.
The third paragraph states that:
"When undergoing an acceleration of 9 g's, your body feels nine times heavie... |
Let $G(x, y_1, \cdots, y_n)$ be my Green function
I want to expand Green function with Fouier transformation of $y_{i}$ and inverse Foruier on $x$ so that $$G(x, y_1,\cdots, y_n) = \int dk_{x} \int_{k_1, \cdots, k_n} G'(k_{x}, k_{1}, \cdots, k_n) e^{-i k_x \cdot x} \delta(k_x + \sum_{i} k_{i}) e^{ik_{1} \cdot y_{1}} \c... |
Girish Argawal writes in his book Quantum statistical theories of spontaneous emission and their relation to other approaches (1974) at the end of chapter 7:
It may appear from (7.13) that the equal-time commutation relations between the field operator and the matter operators are violated; however, there is a sense i... |
Can anyone explain what Pile ups are in a particle accelerator experiments? How can anyone know that an event is a pile-up interaction and how can anyone get rid of these events?
|
The intensity of a sound wave is dependent upon pressure amplitude squared.
Consider a source of power P emitting sound in all directions. An observer moving with a speed v towards the source will not see any change in the pressure amplitude. This shows that intensity of sound wave heard by observer would be the same a... |
The operator product expansion (OPE) of the stress-energy tensor with itself in two-dimensional conformal field theory is:
$$T(z)T(w)\sim \frac{c/2}{(z-w)^4}+\frac{2}{(z-w)^2}T(w)+\frac{1}{z-w}\partial_wT(w)$$
In his lecture on quantum field theory, Ginsparg stated that the $TT$ OPE can be obtained by "performing two c... |
(Please message me or comment if this is not concise enough as a question)
GIVEN:
Energy in the form of electromagnetic waves (aka photons) exerts a gravitational force proportional to said energy:
Does a photon exert a gravitational pull?
Moving towards any direction increases the frequency (decreases wavelength) o... |
I am aware that many quantum entanglement experiments are based on uncertainties related to the polarization of a single photon, which can be measured in the horizontal/vertical, clockwise/counterclockwise, or any other orthonormal basis. However, I have been reading about the nature of photons in more depth from the b... |
Consider the quantum Ising model defined by the Hamiltonian
\begin{equation}
\hat H=-\sum_j\hat\sigma_j^z \hat\sigma_{j+1}^z-h\sum_j \hat\sigma_j^x-g\sum_j\hat\sigma_j^z.
\end{equation}
For $g=0$, we expect the system to be integrable due to the symmetry of spin inversion with respect to the $x$-axis, and therefore... |
My starting point is to find out how the time reversal operator $\Theta$ acts on Holstein-Primakoff (HP) bosons ($\hat{a}_i$ and $\hat{a}^{\dagger}_i$).
Since the HP bosons are related to spin operators through Holstein-Primakoff transformation
\begin{aligned}
\hat{S}_{i}^{z} &= S-\hat{a}^{\dagger}_i\hat{a}_i,\\
\hat{S... |
There are many posts on this forum asking whether motional emf is actually an instance of Faraday's Law -- because, confusingly, it is often taught as though it is, with no qualification. The best answer I've seen so far is this really excellent one by @Timaeus. But I would like to go one step further conceptually. ... |
The gran-canonical partition function for an ideal gas of bosons can be written as
$$\mathcal{Z}=\prod_{(\vec{r},\vec{p})\in\mathbb{R}^{6}}\sum_{N=0}^\infty e^{-\beta E(\|\vec{p}\|)N+\mu\beta N}=\prod_{(\vec{r},\vec{p})\in\mathbb{R}^{6}}\frac{1}{1-e^{-\beta\left(E(\|\vec{p}\|)-\mu\right)}},$$
i.e. every mode $(\vec{r},... |
If liquid pressure is higher at greater depths, particles colliding with the container exert more force, and this is only possible if they collide with greater velocities (assuming mass to be identical for each particle). If, let's say, the system starts out with every particle having the same speed, why does it always... |
My textbook is very unclear on why the dual particle wave in electrons was discovered by the Thomson experiment. I don't understand why they first show me the Thomson experiment for the proof of this phenomenon and then state that the double slit experiment actually confirmed the theory. Also I don't understand how the... |
Consider a metal sphere of radius $b$ with uniform surface charge inside an insulating material with permittivity $\epsilon$. I want to calculate $E$ and $D$ in the dielectric region. I set up a a Gaussian spherical surface with radius $r>b$ around the sphere. I see two options here; (a) Compute $E$ using the total cha... |
I'm working with strain tensors of all sorts at the moment, and I think I've understood how they're derived. However, I'd like to get more intuition of what they're actually telling us.
More specifically, I want to understand what each element in the stress tensor corresponds to in the sense of deformations. Compare my... |
In view of Haag's Theorem, it seems the Hilbert spaces of a free theory and an interacting theory are not the same. Though it seems very believable, I could not find a result that states that this is the case for all theories.
Intuitively, it seems obvious that the Hilbert space of an interacting theory involving disti... |
I am confused regarding the ansatz of the two-photon state. Generally, the two-photon state in the frequency domain is：
$$
|\psi\rangle=\int\int d\omega_1d\omega_2 f(\omega_1,\omega_2) a^+(\omega_1)a^+(\omega_2)|vac\rangle\,,
$$
where $f(\omega_1,\omega_2)$ is the probability function, $a$ is the annihilation operator ... |
Lets say a door is entirely supported by two hinges, one at the bottom corner and one at the top corner.
I know that the two vertical forces of the hinges are produced by newton third law, however where does the horizantal forces came from,why are they produced??
I see that since the body is at rest the horizontal for... |
Given 2 observers isolated from each other and a virtual particle (electron?) is measured for "Spin" by Observer 1 --- condensing it into reality with a state of "Up".
Observer 2 makes measurement of what they still perceive as a virtual particle with an unknown 50/50 chance of "Up" or "Down".
Could Observer 2 get diff... |
I was reading a paper https://arxiv.org/abs/1707.03094 considering the SM extension with $SU(2)$ singlet and doublet fermions. After EWSB, the mass eigenstates are the linear combinations of gauge eigenstates. However, when I tried to diagonalize the mass matrix shown in Eq.7 of this paper, I found that eigenvalues of ... |
Let $A^\nu$ be a 4-potential. In Folland's book on quantum field theory (page 117), he quantizes this object in the case where it represents a massive particle as:
$$A^\nu(x) = \int \sum_{j=1}^3 \frac{1}{\sqrt{2\omega_p}} \big[ e^{-ip_\mu x^\mu} \textbf{$\epsilon$}^\nu(\textbf{$p$}, j) a(\textbf{$p$},j) + e^{ip_\mu x^\... |
Suppose we have we have a Lagrangian $$\mathcal{L} = \frac{1}{2}\partial_\mu\phi\partial^\mu\phi - \frac{m^2}{2}\phi^2$$ for a scalar field $\phi.$ We now treat the first term as the free Lagrangian $\mathcal{L}_0$ with propagator $\frac{i}{p^2+i\epsilon}$. The second term will be our interaction term $\mathcal{L}_I$. ... |
Recently I made a question, you can click in this link. I am having issues with the divergence of the magetic field in the orbital cylindrical frame, in which the divergence of the magnetic field is non-zero, contradicting Maxwell's equations. I revised the calculation and have not found any error.
The magnetic field i... |
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