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When finding the electric field due to a ring. We take on the cos component as the sin component gets cancelled out. Now if we integrate the sin component of the electric field of the sin component should it come 0?.According to me when we integrate the sin components it should not come zero as integral is simply a su... |
I know that the weak force acts on nuclei and causes decay.
But what exactly does the weak force do? Or to put it another way, why do we call it a force? Does it push the red particle of the picture away from the nucleus? Is it called a force only because it has some corresponding force particles? And if it is a force... |
I'm teaching a O-level physics student (grade 10th). We were talking about waves and she asked this question, how does waves transfer energy forward if the molecules just moving up and down? How does the energy stored in waves?
I struggle to explain this in a conceptual way. Can you please help me?
|
The Lorentz Transformation equations are generally presented as a transformation of spacetime between two observers, when they each move at a velocity $v$ along the $x$ axis relative to each other. My question is, what are the equations if the relative motion between the observers is not strictly along the $x$ axis. Fo... |
Consider the Lagrangian $L(q_i,\dot{q_i},t)$ for $i=1,2, ...n$. Transform (invertibly) $q_i$ to another set of generalized coordinates $s_i=s_i(q_j,t)$. Now, in a different scenario, consider transformation of $q_i$ under some group, so that $q_i \rightarrow q_i'=f(q_j,\epsilon_k)$ where $f(q_j,\epsilon_k)$ is some fun... |
Let $(M,g)$ be a flat spacetime, $(\gamma:\mathbb{R}\rightarrow M,e)$ an observer (where $e_1(\lambda)$, $e_2(\lambda)$, $e_3(\lambda)$ together with $\dot{\gamma}(\lambda)$ form the basis of the observers frame at $\gamma(\lambda)$) and $\delta:\mathbb{R}\rightarrow M$ a particle.
How does the observer generically obs... |
From the Feynman lectures Chapter 4, Fig 4-3
"We lifted the one-pound weight only three feet and we lowered W pounds by five feet. Therefore W=3/5 of a pound."
If there is a change of 3ft in height for 1lbs, and the weight on the other side of the pulley -- W -- had a change of 5ft in height, shouldn't we deduce that W... |
Assuming a system of two particles with no external force acting on it,the two particles would come together due to mutual gravitational forces (ignoring electromagnetic forces).
Since gravitational potential energy is considered zero at infinity, is it right to assume that in a closed system, gravitational potential e... |
While writing an answer to this question, I encountered a puzzling conceptual problem when applying Newton's second law for rotation about an instantaneous axis of rotation when the moment of inertia is changing. I will restate the premise of a simplified version of the original problem.
A massless cylindrical tube o... |
I am confused whether drift velocity depends upon area or not .
I checked answers for this question but all of them were cancelling each other out .
from the equation
$$I = neAv$$
It is clear that drift velocity should depend upon area but at the same time don't you think that by
increasing the area of cross section of... |
From Forman Williams' kinetic theory
Diffusion velocity can be related to Binary diff. coeff. and gradient of mass fraction as below.
$V_1 Y_1 = -D_{12} \nabla Y_1$
How can be this derived?
In order to prove this, 2 equations are given.
$V_1 Y_1 + V_2 Y_2 = 0$
$\nabla X_1 = \frac{X_2 X_1}{D_{12}} (V_2 - V_1)$ or $\n... |
Lets say we have an irregularly shaped conductor with a random cavity inside it and a charge +q outside the conductor. Now I have to find the potential inside the conductor due to induced charges on conductor and +q outside the conductor.
Now from the property of conductors with cavity, the field due to outer surface c... |
Does anyone know of a gauge system that is not a model of (super-)gravity where the gauge algebra fails to close off-shell?
|
If a structure were sufficiently strong at a large enough radius from a black hole, could it completely enclose a black hole without collapsing in, since in some sense the material would pull on itself uniformly?
|
If we need to calculate the time-averaged Maxwell stress tensor for an arbitrary field like
$$
\vec{E}=E_{0x}e^{ikz-iwt}\hat{i} + E_{0y}e^{ikz-iwt}\hat{j}+E_{0z}e^{ikz-iwt}\hat{k}
$$
I know we should omit the $e^{-iwt}$ term and multiply by $\frac{1}{2}$ to get the time average, but since the Maxwell stress tensor shou... |
In Griffith's it has been said that while deriving the equation $\nabla\cdot D=\rho_f$
where $D\equiv\epsilon_0E+P$ and $\rho_f$ is the free charge, there has been no mention of the surface bound charge.
This has been justified by the fact that Gauss' Law cannot be calculated at the surface since the volume bound char... |
I’m looking for a qualitative explanation for why electric field strength is the negative of potential gradient.
|
Using Maxwell's equations and Gauss's theorem, we get
$$\dfrac{d}{dt} \int \rho \ dV + \int \mathbf{j} \cdot \mathbf{n} \ dS = 0,$$
where $\rho$ is the electric charge density and $\mathbf{j}$ is the electric current density.
Therefore, we have that
$$e = \int \rho \ dV$$
is the total charge.
Electric current is said t... |
Force can be representd by potential energy function which for 1 dimension case satisfies the derivatives condition $f(x)=-d U(x)/d x$.
If we now consider 3D space, then position will now depends on coordinate system $(x,y,z)$. Then force can be expressed in components as:
$$F_x =-\frac{d U(x,y,z)}{dx}.$$
Similarly, $F... |
I read here that a black hole with a mass of the observable universe, $M=8.8\times10^{52}kg$, would have a Schwarzschild radius of $r_s=13.7$ billion lightyears.
I immediately noticed that at the speed of light, to travel a distance of $r_s$, it would take nearly exactly the age of the universe. Is that a coincidence, ... |
I have given a function
$$G=p_1q_1 - p_2q_2$$
on a 4-dimensional phase-space. This function $G$ commutes with the Hamiltonian
$$H= \frac{p_1p_2}{m} + m\omega^2q_1q_2.$$
It generates a flow
$$(\vec{q},\vec{p}) \rightarrow (\vec{Q}(\vec{q},\vec{p},\alpha), \vec{P}(\vec{q},\vec{p},\alpha)) $$
defined by
$$\frac{dQ_i}{d\al... |
I can't remember exactly what it was, but I remember going through a problem in physics related to gravity on and inside a sphere, and found that inside, gravity acts linearly as a result of some triple integral cancellation with an assumption on uniform density.
Suppose Earth itself was a perfect sphere and you could ... |
In this excellent answer by Emilio Pisanty, he states that:
Of course, all the cool laser-driven QED stuff at the top of that second diagram: if your laser is strong enough that, if you release an electron into the focus, the kinetic energy of its oscillations will exceed $m_ec^2$
, then you can start to have things l... |
I am currently studying Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light, 7th edition, by Max Born and Emil Wolf. Chapter 1.1.2 Material equations says the following:
Metals are very good conductors, but there are other classes of good conducting materials such as ioni... |
I'm having trouble understanding how two D-branes leads to a $U(2)$ gauge theory from David Tong's notes, chapter 7, pages 191-192. I am learning group theory and I understand that a 'charge' is a generator of the symmetry transformation, in this case $U(1)$ of $A_{\mu}$. But now you have non Abelian gauge fields that ... |
The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the positive charges at this point.
this is a quote from wikipedia and if I'm not wrong, it says that: $$||J|| = \frac{I}{A} = \sqrt{J... |
Consider the Hamiltonian:
$$H=D\bigg(S_z-\frac{1}{3}S(S+1)\bigg)$$
Where $S_z$ is the spin-$z$ operator (one half the Pauli matrix for a doublet state) and the matrix representation of $S$ is the unit-matrix times the spin of the system considered. Now my question is, is $S$ classified as an operator, like $S_z$ is? If... |
Let's say we have an infinite current-carrying wire parallel to an infinite conducting plate. Is the magnetic field behind the plate zero? I would say yes, because the field in the plate is zero. Also is the field in front of the plate, so the region containing the wire, given by the field produced by the wire only or ... |
[Ref. Core Principles of Special and General Relativity by Luscombe, page 246]
Let's say we have any two covariant derivative operators $\nabla$ and $\nabla'$. Then there exists a tensor $C^{\alpha}_{\mu\nu}$ such that for all covariant vectors $\omega_{\nu}$,
$$\nabla_{\mu}\omega_{\nu}=\nabla'_{\mu}\omega_{\nu}-C^{\al... |
In the case of charge renormalization, one can present a neat and nice physical idea that brings a physical ground to it called "Vacuum Polarization". Which can be even extended to non-abelian gauge groups(as Coleman did)
I want to know if there's any mechanism that gives some physical sprit to mass renormalization, si... |
Is there a formula to calculate the gravitational force of attraction between two bodies - both are suspended in 3D, both have a non-uniform mass density, both are closed geometric shapes in 3D, and cannot be deformed.
[I'm a computer engineer, and something at work requires this]
|
Consider the Hamiltonian term:
$$H=\left(\frac{1}{6}\right)\left[S_{x}^{4}+S_{y}^{4}+S_{z}^{4}-\frac{1}{5} S(S+1)\left(3 S^{2}+3 S-1\right)\right]$$
where $S_x,\ S_y,\ S_z$ are spin operators.
I know there are implicit unit matrices in an expression like this, but where exactly does it, or they, belong in this express... |
How to tackle real life problems in KINMEATICS in which air drag in some way is involved?
I've attached one such problem in which I was stuck.
|
It is given to us some white noise as $A z(t)$ and the autocorrelation of $A z(t)$ is given as
$\phi(t)= A^2 \delta(t)$ where $\delta(t)$ is the Dirac delta function
Now one signal with $y(t)= B \cos(\omega t)$ with autocorrelation $\phi (t) =[B^2 \cos(\omega t)]/2$ get mixed with the above white noise to form a new i... |
When using $CP(1)$ representation, we will write the unit vector $\boldsymbol{n}$ as the the spinor form, i.e. complex number:
$$\boldsymbol{n}=\left(\begin{array}{cc}z_{1}^{\dagger} & z_{2}^{\dagger}\end{array}\right) \boldsymbol{\sigma}\left(\begin{array}{c}z_{1} \\ z_{2}\end{array}\right)$$
with the constraint
$$z_{... |
I have been reading David Tong's notes on Phonons: http://www.damtp.cam.ac.uk/user/tong/aqm/aqmfour.pdf
I am quite interested in Section 4.1.4, where he quantises the vibrations. First, he defines the most general
(classical) solution $u_{n}(t)$, for the displacement of the $n^{th}$ atom in the chain:
(A) \begin{equati... |
How can I calculate the charge density that is emitted by a hot filament by Thermionic emission?
I was thinking of using this equation since I know the current density and the velocity of the emitted electrons, am I correct?
|
After cooking using a pressure cooker, it usually takes a while for the pressure to be released and for the cooker to be opened. However when I think the food may have been slightly overcooked, I take the pressure cooker from the stove and put it under running cold water from a tap. Within a few seconds, I am able to e... |
So in a diode in forward biased condition the electron from n side recombines with the hole in p side.I also understood that the electrons in n type are in conduction band and holes in p type are in Valence band.So inorder to a conduction band electron to recombine with a hole they should lose that extra energy right?
... |
Can we create a matrix of ring shaped magnetic fields as shown in the attached picture
|
off-diagonal long range order in superfluid is an effect that the matrix element of the single particle's density matrix remains finite in the long distance limit.
My question is: how to prove this experimentally?
|
For example, if I have a function which gives the radius of a circle dependant on $x$ and $y$:
$$
R[x,y]=\sqrt{x^2+y^2}.\tag{1}
$$
Then its partial derivative with respect to $x$ will be
$$
\frac{\partial R[x,y]}{\partial x}=\frac{1}{\sqrt{x^2+y^2}}2x.\tag{2}
$$
If I then claim that the radius is fixed to $A$, I cannot... |
I know that a general quantum measurement is described by a set of measurement operators $\{M_j\}$ satisfying the completeness relation $\sum_j M_j^\dagger M_j = 1$ and that the outcome j occurs with probability $$p(j)=Tr(M_j^\dagger M_j \rho)$$ Furthermore, the post-measurement state after obtaining this outcome is $$... |
If we have a model with more than one Higgs-doublet, when do the VEV of a scalar field of one of those doublets must induce a nonzero VEV on a scalar field of another of those doublets?
|
So I watched a MinutePhysics video explaining the idea of Lorentz transforms geometrically and the way he described it sounded very similar to how 3Blue1Brown explained the idea of change of basis. I know special relativity can be modeled using linear algebra and I found a derivation of the Lorentz transform that was ... |
I have a fan on my desktop. I started to wondering if it would not be just as effective if I flipped it 180 degrees. Since all the wind that comes out of the front has to be sucked in from behind, right?
But it was not. It felt much less effective. I don't have any equipment to perform any actual measurements, but the ... |
Susceptibility means how much is a particular substance allowing or tends to allow magnetic field to pass through it. Diamagnetic substance are those which repel magnetic field and henceforth its susceptibility is negative. But for paramagnetic which are weaker than ferromagnetic but still attracting the magnetic field... |
If we have a $2 \times 2$ $SU(2)_L$ and $SU(2)_R$ matrix $\Phi=\begin{bmatrix}
a & c \\
b & d
\end{bmatrix}$, where a, b, c and d are four complex Klein-Gordon fields, that under a gauge group $SU(2)_L \times SU(2)_R$ transforms as $\Phi \rightarrow U_L \Phi U_R^\dagger$, where $U_L$ and $U_R$ are the SU(2) matrices r... |
If I float motionless in outer space, I will measure spacetime to be approximately flat.
By the equivalence principle, I will get flat spacetime if I am free falling near earth.
Is this right? otherwise I can distinguish between the two scenarios.
Let say I declare myself (while free falling) to be at rest in an inerti... |
First of all, to the fellow Physics Stack Exchange community:
I'm a undergraduate student with knowledge on basic General Relativity (GR).
I do not asking this with an aim to extract relevant competitive results.
I have a poor knowledge on black hole analogues concerning the theory and experimental theory; I know actu... |
"find a force F such that the blocks are stationary relative to the trolley. All surfaces, wheels and pulley are assumed to be friction-less"
1:
This is a very common mechanics problem and has been mentioned on this site before. I tried to solve this question from the pulley frame of reference using pseudo forces and ... |
let's consider the simplest example of electromagnetic waves:
If we consider only this picture, it seems that the magnetic field lines are not closed loops, which is clearly not possible. I know it is due to the fact that each vector in the picture is applied only in one point of space, and that to see the closed loop... |
In many sources discussing neutrino decoupling I find the following claim:
"The thermally averaged rate of weak interactions is given by:
$\Gamma = n \langle\sigma |v|\rangle$,
where $\langle\sigma |v|\rangle$ is a thermally averaged cross section given by:
$\langle\sigma |v|\rangle=G_F^2 T^2$.
My problem is:
It is th... |
I have been looking at a paper modelling velocities and accelerations for dropped objects, in this case a perfectly elastic collision for an object hitting the ground. Where $v_1$ is the impact velocity and $v_2$ is the velocity immediately after impact (i.e the rebound velocity), the velocity time graph can be modeled... |
We are all familiar with the standard construction of the Lagrangian of a free relativistic particle:
Start with the definition
$$
S=\int_{\Delta t}ds. \tag{1}
$$
Then use the definition of the line element $ds=\sqrt{g_{\mu\nu}dX^\mu dX^\nu}$
$$
S=\int_{\Delta t} \sqrt{g_{\mu\nu} dX^\mu dX^\nu}\tag{2}
$$
Then parametri... |
I'm wondering if the information lost by rearranging the letters of a book is measurable as a difference in its initial and final mass.
Choose a long, random string over an alphabet, say $\{0,1\}$, of length $N$. It should be random in the sense that it is incompressible. You might also choose a big book, at random, an... |
Before the electric power grid, what were Ampere, Faraday, Coulomb, et. al using to study electricity?
In everything I read, it just kind of says "____ noticed that when wires carrying a charge came near each other" or something of the sort, but nothing really talks about how they were generating current through these ... |
Assume the Hamiltonian of a quantum particle to be independent of time and be of the form $H=\frac{1}{2m}(\hat{p}^{2}_{x}+\hat{p}^{2}_{y})+V(x,y)$. Define a new operator $\hat{p}=\hat{p}_{x}-\hat{p}_{y}$ and such that it commutes with the $H$. But then this implies that $\hat{p}$ is independent of time. In other words,... |
Assuming the mass of the universe was spread completely evenly throughout space why would gravitational attraction happen? All bodies in the universe would feel gravitational tug equally in all directions so why would they go anywhere?
|
Whats the theory behind bike skidding on the sand?
Is it related to friction and if then why it skids. Is that the
sand has more friction if so then pedaling should be difficult rather than skidding.
|
I’ve read that Fast Radio Bursts are very “intense”, but how is intensity measured?
|
The QCD lagrangian has a $SU(N_{f})$ vectorial symmetry, which is explicitly broken by the difference in quark current masses. If this symmetry was exact ($m_{u}=m_{d}=m_{s}$...) the charges associated with these transformations would be conserved.
In my view, these charges are the number of each quark flavour, so if t... |
This question has been asked before in the form of the 'Twin paradox' , and there are 42 pages of questions on this site alone when I search for 'twin paradox'.
For example
Does the twin paradox require both twins to be far away from any gravity field?
Clarification regarding Special Relativity
The counterargument has ... |
I am studying Introduction To Quantum Mechanics by David Griffiths. Great book.
In section $2.4$ he introduces the Free Particle potential and describes finding general solutions made up of an envelope '$\phi(k)$' and ripples 'complex exponential in $x$,$t$'
The envelope function '$\phi(k)$' is found by integrating the... |
In a physics lab inclined plane experiment, I am calculating the kinetic friction $\mu$ using the formula:
$$\mu = \tan\theta - (a/g)\sec\theta$$
Here $a$ is the acceleration and $\theta$ is the angle made by the inclined plane with the horizontal.
For the given uncertainties $\Delta\theta$ and $\Delta a$, I calculate ... |
I need to obtain the derivative of internal energy $U$ w.r.t. pressure $p$ at a constant volume $V$. Realizing that $\mathrm{d} U = T \mathrm{d} S - p \mathrm{d} V$, I rewrite
$$
\left( \frac{\partial U}{\partial p} \right)_V = \left( \frac{\partial U}{\partial S} \right)_V \left( \frac{\partial S}{\partial p} \right)_... |
The gravitational potential energy at infinity os supposed to be zero. Since body always moves towards lower potential, the gravitational potential is taken as negative so that gravitational potential energy can decrease on moving towards earth.
On the other hand,for near earth surface, potential is taken to be zero at... |
Suppose there is an electron at the n side.Does the electron have to travel until the p side to get recombined or is it like an electron travels some distance along n side gets recombined ,then another electron pops up moves a small distance then recombines again and this process repeats until it reaches hole in the n ... |
I seem to remember reading somewhere that within the lifetime of a closed, recollapsing Friedman-Lemaitre-Robertson-Walker universe light could travel around the space precisely once.
Could someone please enlighten me, or provide a negative answer if I'm "off my rocker"? I would imagine things like matter v.s. radiatio... |
What type of materials can block UV-C type radiation? Such radiation is used in germicidal chambers. Do these materials actually block all of the radiation?
|
If a mass is suspended from the ceiling by a massless rope, will tension be the same at all points on the rope?
|
I was watching a video about Electrostatic Potential and Electric Potential Energy by Professor Walter Lewin when I encountered a question.
So, Professor Lewin assumes that a charge $Q$ was placed in free space, and hence, no work was done to place it there. Then, another charge (a test charge) $q$ was placed at a dis... |
Last year we captured shadow of black hole at the centre of M87 by Event Horizon telescope. I am wondering if Hawking radiation can have any effect on the black hole shadow. The more I think about Hawking radiation: if it can have some observational effect on blackhole shadow, the more I am convinced that it won't bec... |
The book says that if the net of all external forces acting on a system equals zero, the system's(centre of mass of the system basically) momentum is conserved. But what if some internally stored energy in the system is converted to kinetic energy? I mean to say, for example -->
Consider a toy car which runs on spring ... |
If I have a non-inertial frame accelerating with acceleration $A$ with respect to an inertial frame and if I have two pendulums, one in the inertial frame and the other in the non inertial frame, then how will the motion of the pendulum differ when seen from each frame? The pendulum in the inertial frame should oscilla... |
The formula for energy density of electromagnetic field in electrodynamics is
$$\frac{1}{8\pi} (\vec E\cdot\vec D+\vec B\cdot\vec H).$$
This formula appears in all general physics courses I looked at. However Feynman writes in Section 27-4 of his well known course:
... we must say that we do not know for certain what ... |
When exactly is the Net work done by internal forces on a system 0, and what is the intuition behind it?
I have heard it is valid for rigid bodies but I am unaware of what they are as of this point, since i am only in high school.
Secondly, what is the reason behind it? I know that by newton’s 3rd law, internal forces ... |
I try to calculate energy-momentum tensor from Sugawara construction of Wakimoto representation for $SU(2)_k$ current in 2d CFT. but at first I have to understand rearrangement lemma. so can anybody tell me what happens here? parentheses are normal ordering here.
|
My book makes the following assumptions (as far as I understood) in deriving length contraction and time dilation from Lorentz transformation :
Suppose there is an inertial frame $S$ and another frame $S'$ which has a velocity $v$ relative to $S$. There is a rod whose starting point is $a'$ and ending point is $b'$ in ... |
Exploring the nature of confined energy giving rise to "mass" or gravitation,
My assumptions:
Most of my own mass is from the confinement of baryonic quarks in the strong force
A bunch of photons in a mirror box makes the box weigh more
All types of confined pressure actually produce a gravitational effect
This is bec... |
I'm watching Schuller's lectures on gravitation on youtube. It's mentioned that spacetime is modelled as a topological manifold (with a bunch of additional structure that's not relevant to this question).
A topological manifold is a set $M$ with a topology $\mathcal{O}_M$ such that each point in $M$ is covered by a cha... |
Vacuum is said to have an intrinsic impedance. What is the source of this? Impedance is quite understandable in bulk matter, but I'm unable to comprehend it's presence in vacuum.
|
Do points in a wave move along with the wave?
I was reading this post and I have become utterly confused with the concept of a wave. First, is a wave made up of particles or not? (Then again light is said to both a wave and a particle.) I am really confused. Is a light wave a collection of photons?
Second, in that post... |
If we see metric-compatible connections (not Levi-Civita) then can we say that the connections are spin-3 objects? If not, when do we say that an object with $J$ index is a spin-$J$ object ($J \in \mathbb{Z}$) ?
|
In our lecture, we had the following scenario:
Suppose we have a 2D-free electron gas which is in a magnetic field $B$ perpendicular to the free electron system. Now the electron states have energies of $\hbar \omega_c\left( \lambda + \frac{1}{2} \right)$, where $\lambda \in \mathbb N_{0}$ is the Landau Level index and... |
So, I was trying to do this question and here is my attempt:
I first tried work out the surface tension forces like so:
I did $ F= PA$
$ P = 4 \frac{\gamma}{r}$ by laplace law
so,
$ F = 16\gamma \pi r $
But this answer is wrong, And I'm even more confused how to account for the unknown charge thing
However I attempte... |
Consider two disks (not friction-less) with some moment of inertia ($I_1$ and $I_2$). Both of them are given angular velocities ($\omega_1$ and $\omega_2$) both in same sense.
Now if we bring both disks in contact after some time they will have common angular velocity. Now my text says that the new angular velocity ($\... |
I'm studying renormalization group theory from "Quantum and Statistical Field Theory by M. Le Bellac". At page 78 he is linearizing the renormalization group transformation around a fixed point. The transformation is $K_\alpha=K^*_\alpha+\delta K_\alpha \approx \sum_\beta T_{\alpha\beta}(s) \delta K_\beta$ with $T_{\al... |
I studied about the direction of current density but nowhere it is mentioned that what is the significance of direction of current density
Also I want to know why we used dot product instead of cross product, though I know we used it because current is a scalar but still that doesn't suffice it any better
$$I=\vec{J}\c... |
Let’s say there are 4 batteries in series in a circuit connected to a bulb. One of the battery is flat. Can the bulb still light up?
I’m so confused now.
|
I was trying to solve the following problem from the problem book on relativty:
Problem 5.22. Show that the velocity of sound $v_{s}$ in a relativistic perfect fluid is given by
$$v_{s}^{2}=\partial p /\left.\partial \rho\right|_{s=c o n s t a n t}$$
For a high temperature relativistic gas with an equation of state $\r... |
In a previous question, I asked what the matrix representation of the electroweak fields is, and I was told they are identical to the Faraday tensors, but come in a set of three ($W_i, i\in \{1,2,3\}$), associated to the $SU(2)$ symmetry and another one ($B$), associated to the $U(1)$ symmetry for a total of four.
I al... |
I have seen this stack question Applying Gauss' Law to find Electric Field but I got confused when I saw the comment and the answer because, clearly the flux is a scalar quantity (due to dot product). So after using Gauss law to find magnitude, how do I find the direction in which the field vector points?
|
Say that I have the following two-particle states:
$$|a\rangle = c_1^{(+)} c_2^{(+)} |0\rangle,$$ where $c_1^{(+)}$ and $c_2^{(+)}$ are two fermionic creation operators and
$$|b\rangle = c_3^{(+)} c_4^{(+)} |0\rangle,$$ where $c_3^{(+)}$ and $c_4^{(+)}$ are two fermionic creation operators.
I wish to find the matrix el... |
Q)A parachutist jumps from the top of a very high tower with a siren of frequency 800 Hz on his
back. Assume his initial velocity to be zero. After falling freely for 12s, he observes that the
frequency of sound heard by him reflected from level ground below him is differing by 700 Hz
w.r.t. the original frequency. Wha... |
Suppose a block of mass $1$ kg is kept on a rough horizontal surface. Let the friction coefficient be $0.2$. Now let's say, I apply a force of $1$N in the east direction. Friction will act in the west direction and will easily be able to balance $1.5$ N . Now suppose if I again apply $1.5$ N force on the block (while... |
Scenario 1 - Ideal battery
Suppose I have an ideal battery whose electrolyte’s resistance is zero. In the working battery there will be current flowing inside the battery also (due to battery forces) from lower potential to higher potential. Now I choose two points inside the battery, one on the positive terminal and o... |
I'm trying to reconcile how photons do and don't have mass, and the distinction seems to come from the frame of reference. As far as I understand, if you were to somehow stop a photon relative to an observer so that it was at rest, you wouldn't be able to measure its mass, probably for multiple paradoxical reasons, alt... |
First off, I did look through some other questions:
Covariant Derivative of Metric Tensor
Why is the covariant derivative of the metric tensor zero?
https://math.stackexchange.com/q/2174588/
But they either give the covariant derivative as:
$\nabla_{\rho} g_{\mu\nu}=\frac{\partial g_{\mu\nu}}{\partial x^{\rho}} - g_{\... |
I am reading through Landau, Lifschitz "The classical theory of fields", in particular I am reading about bremsstrahlung spectrum in $\S70$ "Radiation in the case of Coulomb interaction".
The book says that the radiation emitted by a single particle is given by:
$$d\mathcal{E}_\omega=\dfrac{\pi \mu^2\alpha^2\omega^3}{6... |
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