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I am not understanding how to derive this particular expression, which relates the inexact differential of work to the exact differential of volume,
$$\delta w = -PdV $$
My attempt:
Reversible work can be defined as:
$$w=-\int P dV $$
First, I integrate both sides with respect to volume,
$$\frac{d}{dV}(w)=-\frac{d}{dV... |
Obviously, two chunks of pure Iron-56 won't pass through each other like photons go right through each other...
Why is that?
Is it because of the fact that composite fermions are made of smaller fermions, which which repel each other?
What about the background quantum foam? Particles are more likely to pop into existe... |
In the theory of quantum mechanics theory (would it be a correct or incorrect theory), is the fact that quantum mechanic theory follows probabilistic laws directly connected ("bijection") to the fact that the energy levels are quantified in this theory ?
Could a theory manage to have discret levels while determinist l... |
In solid state physics, the schrodinger equation
$$H \psi_{\vec{k}} = E_{\vec{k}} \psi_{\vec{k}}$$
has solutions $\psi_{\vec{k}}(x)$. In the near free electron approximation, I was told that $$\psi_{\vec{k}+\vec{g}}(x)=\psi_{\vec{k}}(x)$$(exactly the same in real $x$, and no phase factor difference)
However, I was also... |
I want entropy as a function of pressure and volume for an ideal gas. So, for that, I found a simple expression for the Sackur-tetrode equation by knzhou here. It goes as follows:
$$S = n C_v \ln \frac{PV^{\gamma} }{n^{\gamma} } +C$$
I tried recreating this formula from the state function expression of entropy given bu... |
I watched a cool video today on Heisenberg's uncertainty principle and electron orbits. (https://www.youtube.com/watch?v=BMIvWz-7GmU)
Are S orbitals always a cloud around the atomic nucleus and a p orbitals always nodes?
How does an electron jump from one orbit to another? How do the orbits of very large atoms work?... |
In 'QCD and collider Physics' book by Ellis, Stirling and Webber, chapter 4.2 'The parton model from field theory' there is this equation for the amplitude of the process $e^- (k) P \rightarrow e^- (k^\prime) X$ (where $P$ stands for the proton and $X$ for an undetermined outgoing jet)
$$
A = e\bar{u}(k^\prime)\gamma^\... |
It's commonly used in imaginary-time path integral that "analytic continuation" means replacing $t \rightarrow - i \tau$ or reparametrizing the theory in terms of imaginary time $\tau = i t$. For example, it's common practice to just replace the imaginary time $\tau \rightarrow i t$ to figure out the real time Green's ... |
On this website one can use the FSPL model to calculate the Path Loss. This is typically interpreted online as the theoretical signal strength (in dB) that one may receive (e.g. from some WiFi). However, assuming that the G(TX) does not contain the information of the actual transmission power (but in fact some -+delta)... |
The Born rule implies that the probability density $\rho$ is defined as $$\rho(x,y,z)=|\psi(x,y,z,t_0)|^2$$ at time $t_0$. What is the difference in this probability density and the probability of a system being described by a particular eigenstate? I.e.,letting $|o_i\rangle$ be the $i$th eigenstate and letting $c_i$ b... |
This very nice NASA page continuously updates Voyager 1 & 2 distance away.
How is that distance calculated/determined?
|
In classical mechanics, the phase space of a single particle is given by the position $x=x(t)$ and its momentum $p=\dot{x}(t)$. More generally, a particle is described by generalized coordinates $q$ and $p = \dot{q}$. In quantum mechanics, this two objects become operators $\hat{x}$ and $\hat{p}$ by means of canonical ... |
So I’m doing QM and found bunch of problems for beginners and I’m struggling with this one:
$$\lim_{a\rightarrow 0}\int^{\infty}_{-\infty}e^{\frac{ip x}{\hbar}-a x^2}dx=2\pi\hbar\delta(p).$$
If I swap the limit and the integral I get the correct answer, but can I do that?
|
I found this section in The Feynman Lectures Vol. 1 page (28-2). I was curious on where we stand to solve this question as of today?
Any information/links on developments will be helpful.
\begin{equation}
\tag{28.3}
E=\frac{-q}{4\pi\epsilon_0}\left[
... |
I am talking about this particular statement by Lenz who made the Lenz law for finding directions of induced EMI - "Nature abhors a change in flux".
|
What is string theory ? (correct me if i am wrong) Why a new underlying theory was required when modern Physics was only one step away from establishing a G.U.T. (unification attempt for four fundamental forces out of which three could be clubbed.) using Tensor Flow ?
|
Various texts (1,2) state that electrons are point particles, but if this is the case then when two electrons collide, one of them knows the others position with exact certainty (treating one as an observer and the other the system). If this ever happens we run into contradictions, mentioned in this post.
This must mea... |
Some context for the above question is warranted.
While reading Hartle's Gravity, the following statements made recurring appearances: "Gravity is not a force, it is the geometry of 4D spacetime. ... In GR, the mass of the sun curves the surrounding spacetime, and the Earth moves on a straight line path in that curved ... |
From Wikipedia : In ion quantum computer, if the ions are not properly isolated, noise can result from ions interacting with external electromagnetic fields, which creates random movement and destroys the quantized energy states.
This statement also appeared on DiVincenzo's criteria for building quantum computer albeit... |
Before closing it as a dupe of this. Please go through the question once .
Is it theoretically possible that quarks make up an electron ( like you may get a particle with the same electronic charge $(-e)$ with three down quarks however the binding energy for that down quarks triplet should be a great number since Dr j... |
We have a disconnected capacitor having charge density $\sigma_{1}$ on its positive plate.
Now we fill it with a dielectric as shown.
Will the free charge density( the mobile charges on the capacitor plate not the bound charge of the dielectric) change now?
|
In Concepts of Physics part-2 by H.C.-Verma, it is written on page 87 right under section 28.10 :
"The energy of thermal radiation emitted per unit time by a black body of surface Area is given by:
$$ U =\sigma AT^4.$$
...now the accepted answer in this stack post by Daniel Sank says that the above equation describes... |
While learning atomic structure I stumbled upon a very unusual question.
As we know that the energy of a wave is given by the equation: $E=\frac{hc}{λ}$ and Louis de broglie wave equation is given by the equation $λ_{B}=\frac{h}{p}$. My doubt is that, that is $λ_{B}= λ$ $?$. Do the $λ_{B}, λ$ represent the same thing $... |
As a simple example, take a constant magnetic field $\vec{B} = (0,0,B)$. This is invariant under rotations about the $z$ axis. However, we can express $\vec{B}$ as the curl of a vector potential $\vec{A}$:
$$\vec{A} = \begin{pmatrix}
0 \\Bx \\ 0
\end{pmatrix} + \nabla \lambda$$
for any scalar function $\lambda$. The ve... |
If I move my swing my arm really fast, the matter in my arm should experience time slower than the matter in my body.
So how does my body still sync with each other?
And a more general question that derives from this: A lot of matter move at different speeds inside our body, how does anything ever stay synced?
|
Yes I've seen the other question posted on the site - Moment of inertia of solid cube about body diagonal , but I don't really understand the solution
The final result is $m l^2/6$, but I'm not able to get it.
I assumed it would be the same as the moment of inertia of diagonal for a square but that's $ml^2/12$.
When we... |
When the Andromeda galaxy and Milky Way merge in the future, the super-massive black holes at their respective galactic centers will likely eventually merge. Similarly to the gravitational waves detected by LIGO on 14th September 2015, I assume that the merger of these super-massive black holes will generate gravitatio... |
I was answering some questions in a textbook and it asked: Which one has the highest absolute uncertainty? A ruler, a voltmeter or vernier caliper?
I went with the ruler because the absolute uncertainty of a measurement (not a reading) is the same as its resolution and so the resolution of a ruler in 1mm. The vernier c... |
Reference : $^{\prime\prime}$Physics of Atoms and Molecules$^{\prime\prime}$ by B.H.Bransden and C.J.Joachain, 1983 Edition.
In $\boldsymbol{\S}$4.1 The electromagnetic field and its interaction with charged particles we read :
\begin{align}
\mathscr{E}\!\!\!\!\mathscr{E} \left(\mathbf{r},t\right) & \boldsymbol{=}\bol... |
Why the pressure at point $y=0$ in the given example (see image) is atmospheric pressure $p_o$. How can it be atmospheric pressure? The pressure at that point should be the pressure exerted by the fluid flowing through the hole but the author of my book "Fundamentals of Physics by Halliday/Resnick/Walker" has substitut... |
Some people consider all elementary particles to be non-existent. They tell us that they are changes in the field configurations that last which are called "real particles", while those that not last long enough are called "virtual particles".
But field configurations refer to wavefunctions that are a part of the entir... |
The question is pretty short. I have been told that unlike for flat spacetime, in curved spacetime we cannot write
$g^{\mu \nu}\partial_{\nu}f=\partial^{\mu}f$
With $f$ an scalar function, but I don't really get why.
|
A stone was dropped into an empty well. It takes 10 sec to hit the ground. What was the velocity of the ball?
So since I have to use the formula $v=gt$ I'm quite confused if g=$-9.81m/s^2$ or not? If g is negative, velocity will be negative too right?
I also want to know if the stone was thrown vertically upward fr... |
Is there a book for someone who already knows some group theory and theory of group representations on the mathematical side, and just wants something which explains the applications in particle physics and the Standard Model?
To be clear, I am not looking for a book which is intended or written for physicists, and I d... |
Suppose I have a complete set of two commuting observables $\hat{A}, \hat{B}$ for which:
$$ \hat{A} |{a} \rangle = a |a\rangle $$
$$ \hat{B} |b \rangle = b |b\rangle $$
Now, I can find a common eigenstate in the Hilbert space where $\hat{A}$ and $\hat{B}$ operates, or I can define a new Hilbert space which is the direc... |
Can u explain the line, " A voltage source likes open circuit load and hates short circuit load." In my textbook it just says 'for obvious reasons'
|
Let’s say we have a very massive neutron star. It gets hit by a sizable asteroid. The combined object becomes massive enough for an event horizon to form. According to what we know, would the neutron star itself necessarily change all that much during these events?
|
I have come across flux lines that are being used to tune the frequency of transmon qubits in circuit QED.
I do not understand it on the hardware level. Is it related to magnetic flux being passed through those flux lines to tune the frequency of the qubits?
|
It is known that an arbitrary rotation can be expressed in terms of three consecutive rotations called the Euler rotations. So instead of expressing the rotation operator as $\hat{R}(\hat{n},\phi) = \exp\left(-\frac{i\phi}{\hbar} \hat{n}\cdot\vec{J}\right )$ one can write $\hat{R}(\alpha,\beta,\gamma) = \hat{R}_z(\alph... |
My Question: For finding the Center of Mass ($COM$) of a hollow cone, why do we use its area to define its elemental mass ($dm$) and not its volume, which we use to find the $COM$ of a solid cone.
The formula I use for finding the center of mass of an object is:
$$\frac{\int_{o}^{h}dmy}{\int_{o}^{h}dm}$$
|
If I consider the situation of the problem below, and try to calculate the angular momentum of the rotating (without slipping) solid sphere about point $P$, then obviously I'll use the formula:
$$\vec{L_P} = m(\vec{r} \times \vec{v_{com}}) + I_{com} \vec{\omega}$$
The direction of $\vec{\omega}$ and $\vec{r} \times \v... |
From a source1 I regard as reputable, I heard the following assertion (without explanation):
If the water in a stream flows twice as fast, it can carry objects (pebbles/etc) sixty four times larger.
Bearing in mind a related question: Power vs. Speed - Indoor rowing which shows that to double your speed, you require ... |
Let's first have a look at the observed speed within galaxies (source):
On the left side we can see the speed of celestial bodies within galaxies derived by gravity only (gravity is usually created by a black hole at the center of a galaxy), on the right side we can see the observed speed of celestial bodies, both in ... |
Different interpretations of young's double slit experiment is available, I read Copenhagen and Feynman's path integral interpretation of double slit experiment; former uses the idea of wave function and later uses the idea of infinite paths and sum over the weight factors of each path obeys causality.
I Googled lot o... |
I know this question has likely been asked before, but I am horribly confused and need some help with this.
Let's say we have a system whose initial state at t = 0 is given in terms of a complete and orthonormal eigenvector of the Hamiltonian:
$$ | \Psi(0)\rangle = \frac{1}{\sqrt{3}} |\phi_1\rangle+ \frac{1}{\sqrt{2}} ... |
I wanted to find the density of states of a 1D ideal, noninteracting Fermi gas. My workings are below:
$$D(\epsilon) = \frac{1}{2\pi}\int_{0}^{\infty}\delta(\epsilon-\epsilon_k)dk \times2$$
$$\epsilon_k=\frac{\hbar^2k^2}{2m} \rightarrow dk=\frac{\sqrt{2m}}{\hbar}\cdot\frac{1}{2\sqrt{\epsilon_k}}d\epsilon_k$$
Which mean... |
We all know classical mechanics deal with bigger objects and
quantum mechanics deal with very tiny particles.
I hear spin number in quantum mechanics, but I don't see anything
like that in classic mechanics.
Why don't we calculate spin number in classical mechanics?
|
Consider an infinitely large plane which exerts gravity onto a point mass with mass $m$ and located at height $h_0$. The point mass moves perpendicularly through the plane without undergoing any friction.
It can be easily derived that the force exerted by the plane is a constant and thus independent of the height at wh... |
When we look through a very narrow slit, the image is blurred. We assume that the aperture is horizontal and we observe the image in red light. We are looking at an image consisting of horizontal and vertical lines. Which lines are more blurred? What will happen when we use green light?
|
A bicycle and its rider have a total mass of $100kg$ and travel around a circular banked track at a radius of $20m$ and at a constant speed to $10ms^{-1}$, as shown. The track is banked so that there is no sideways friction force applied by the track on the wheels.
Part a) wants me to draw the net resultant force, whi... |
Suppose Alice and Bob each hold qubits; they have a joint state
$$|\psi\rangle = \frac{1}{\sqrt 3}\big(|00\rangle + |01\rangle + |11\rangle\big).$$
Alice measures the first qubit in some basis (say $|+\rangle, |-\rangle$); I want to see what Bob's qubit looks like post-measurement. The result should be a a probabilisti... |
The quantum adiabatic theorem states that: A parametric system remains in its instantaneous eigenstate (with a phase difference) if one of the parameters of the Hamiltonian changes slow enough. This is very counter-intuitively to me giving the following example: Considering a material in a magnetic field, even we turn ... |
While surfing through some further reading suggestions on string theory, I stumbled upon this slide from a talk by Nathan Seiberg. I wanted to derive the main argument by applying a perturbation expansion for this partition function, but I couldn't get my head around the concept of a phase space for $N$ by $N$ matrices... |
Suppose you are given a line $L$ in space, then if you have a system of particles with forces acting on them the torque about a point on the line, you have to sum $ \sum r_i F_i$ over all particles. However say you wanted to compute the quantity 'torque about the line', then you'd find that this quantity is independent... |
I have been given a question as
RMS value of an RF(Radio Frequency) voltage after amplitude modulation to a depth of $50$% by a sinusoidal voltage is $80$ Volts. Calculate the RMS value of modulated voltage when modulated to a depth of $75$%.
Now my question is that, If the modulation index$(m_a=\frac{V_m}{V_c})$ of an... |
Consider the Nambu-Goto action
\begin{equation}
S=\int d\sigma d\tau \sqrt{(\partial_\sigma X^\mu \partial_\tau X_\mu)^2-(\partial_\sigma X^\mu\partial_\sigma X_\mu)(\partial_\tau X^\mu\partial_\tau X_\mu)}.
\end{equation}
We have that $\partial_\tau X^\mu$ and $\partial_\sigma X^\mu$ are element of the tangent space t... |
We can only speculate what is going on but does the black hole singularity make the light arrive faster than it would in space not affected by gravity?
|
I'm currently going through Byron and Fuller, and problem 1.13 is a problem about deriving the electromagnetic field tensor. The field tensor we derive is the complex version:
$$F = \begin{bmatrix}
0 & H_z & -H_y & -iE_x \\
-H_z & 0 & H_x & -iE_y \\
H_y & -H_x & 0 & -iE_z \\
iE_x & iE_y & iE_z & 0 \\
\end{bmatrix}$$
T... |
The Wikipedia article on the Novikov self-consistency principle has a section on time loop logic, where it discusses using time travel to solve any NP problem by finding an algorithm where the only consistent outcome is the solution.
For example you could have an algorithm as follows:
To find a factor of a number $n$:
... |
In Peskin and Schroeder (PS) Chap 16.4, such as after eq.16.45, in p.518, PS said:
"local gauge transformation parameter $\alpha$ is proportional to the ghost field and the anti-commuting continuous infinitesimal parameter $\epsilon$."
So the gauge parameter $$\alpha$$
and BRST anti-commuting continuous infinitesimal p... |
I am reading this article, where
the author uses the Jones formalism to describe the interference with polarizers.
The first one is vertical and the angle of the other can vary. This gives different patterns.
It goes from perfect fringe visibility when they are parallel to no fringe if orthogonal.
Intermediate visibili... |
I have conducted the experiment. My independent variable is the angle of releasing the pendulum and my dependent variable is the speed of the ball that is hit by it. I know the following quantities: masses of the pendulum ball and the grounded ball, different angles with different velocities which I measured in my expe... |
I am reading one very good notes on Maxwell-Juttner distribution, but I met some places that puzzled me a lot. Please give me a hand!
The notes:
Let $\Theta = kT/mc^2$ be the dimensionless temperature, $\vec\beta = \vec{v}/c$ is the dimensionless particle velocity, $\gamma = (1-\beta^2)^{-1/2}$ is the particle Lorentz... |
Lets say there are two objects in space that are attracted to each other, and are a distance r from each other. The gravitation force between the two objects is $$G\frac{Mm}{r^2}$$ As they accelerate, the rate at which $r$ changes increases, so the rate of change of the force increases, etc. I've heard you can keep tak... |
In a student experiment the following assembly is used to create an entangled photon pair.
From the left, a laser beam polarized along $\frac{\hat{x}+\hat{y}}{\sqrt{2}}$ is incident on a pair of BBO crystals. The optical axis of the first crystal is directed along $\hat{y}$ whereas in the second crystal it is directed... |
I am thinking about designing an underwater vehicle.
It's shape will be cylindrical(12cmx70cm). It will have a pump to pump water into a tank for adjusting density of the vehicle. In that way It will be able to dive and come up. I was planning to use one pump as well one water tank which will be centered on the vehicle... |
Given: closed-open pipe with Helium, density of the gas is P, pipes length is l. I have to find minimal frequency of standing waves in pipe
Picture:
I have found some info about simple standing waves in closed and open pipes, but no info about pipes with some kind of gas in it. As I guess, speed in Helium will be high... |
Consider a stationary Schwarzschild black hole: in a vacuum, no rotation, no electric charge. Using the Schwarzschild metric, we can draw diagrams describing how the radial coordinate $r$ varies with the angular coordinate $\varphi$ when a photon or a massive test particle spirals from a large distance towards the blac... |
I have a question about determining the phase and group velocity for a monoatomic lattice.
I know from various reference texts that
$$v_p = \frac {\omega}{q}$$
$$v_g = \frac {\partial \omega}{\partial q}$$
Where q is the wave vector and $\omega$ is the angular frequency.
My question is, why? This seems to be derived ou... |
If you were to design a drone or probe that could fly close enough to the sun to examine the corona, closer than the Parker Solar Probe, how close could you get and still have reliable communications with it? Is there a point where the sun's electromagnetic interference would make it impossible? This is assuming that t... |
I am working out the exchange symmetry of the eigenstates of the total angular momentum operator of a system of two spin-1 bosons.
I know that there must be a quintet, triplet, and a singlet state.
The highest state of the quintet is $|\uparrow\rangle |\uparrow\rangle$ and is symmetric under particle exchange.
Applying... |
I'm trying to solve the following homework question.
Suppose that in the laboratory frame of reference we have $2$ particles. Particle "$a$" is at rest with total energy $E_a$, while particle "$b$" is moving away with total energy $E_2$. If particle $b$ has momentum $\vec{p}$, show that the reference frame in which th... |
I could really do with some insight into how the capacitance of a conductor increases when you bring another oppositely charged or earthed conductor near it. The explanation in my book is as follows:
What I can't understand is how the potential ($V$) is decreased. If I bring an oppositely charged conductor near the c... |
I'm having trouble understanding Gauss's law.
Suppose you have a sphere centered upon a positive charge. Then the flux through the sphere is some positive value, according to Gauss's law. I try to analogize the positive charge as this 3D source of water and the surface of the sphere is this boundary line. Since there i... |
I want to find the general solution of the Helmholtz equation in the context of electromagentism
$$(\nabla^2+n(\omega)^2\omega^2)\hat{E}(\omega, \vec{r})=0$$
For this I tried Fourier transforming the solution
$$\hat{E}(\omega,\vec{r})=\frac{1}{\sqrt{2\pi}^3}\int d^3\vec{k}\tilde{E}(\omega, \vec{k})\textrm{e}^{i\vec{k}\... |
Until now, I thought electromagnetic potential $A^{\mu}(x)$ transform like $x^{\mu}$ under the Lorentz transformation:
$$A^{\mu}(x)=\Lambda^{\mu}_{\ \nu}A^{\nu}(x).$$
But according to time reversal symmetry of governing equations, $A^{\mu}(x)=(A^{0}(x), A^{j}(x))$ transform under the time inverse transformation:
$$A’^{... |
Currently I was going through the formula
$$(\Delta x)(\Delta p)\geq\frac{h}{4\pi}$$
which is of course the enclosed form of Heisenberg’s Uncertainty Principle. But I also get this formula
$$(\Delta x)(\Delta \lambda)\geq\frac{\lambda^2}{4\pi}.$$
I suppose this is an extension of Heisenberg's principle but I didn't get... |
Will cooling off the condenser coil improve the efficiency of a domestic refrigerator, based on R134a? If so, what is the lowest ambient temperature the condenser can take, for the system to still work?
My idea is to rewire a standard refrigerator, and put the condenser coil outdoors, while keeping the evaporator and t... |
I have a question regarding entropy:
The change in intropy for a system at constant composition with no other work than volume work is:
$T_sdS=dU +pdV$, were $T_s$ is the surrounding temperature, and $p$ is the system pressure
$T_sdS= dQ -p_sdV + pdV$
if the process is done in a quasi-static manner, p_s=p (because we a... |
If there was an M2-brane with the topology of a sphere. Then I can't see why there are not the same thing?
They both have the same topology if we consider the black hole event horizon.
Both seem to have information stored on the surfaces.
But if they are the same thing it would mean an M2 brane acts like a hologram of ... |
question: WHY BRST formulation works? In more details:
What are the conditions we need to impose on QFT to find the BRST (global) symmetry?
Why can we demand the BRST parameter $\epsilon$ directly that relates the gauge symmetry parameter $\alpha^a(x)$ to the ghost field?
And how to determine how many BRST parameter... |
Is a brain neuron (actually even only my own neuron, not anybody else's) the only physical object in existence which cannot be in superposition (firing / not firing)?
We never experience any superposition in our thinking, and computing in our brain to function obviously needs neurons to fire/not fire in definitive way.... |
In the following article: Classsical Mechanics, the letter for force $\underline{F} $, the momentum $\underline{p} $ and even nabla $\underline{ \nabla }$ are underscored. Is this a way of talking about covariant and contravariant?
|
Given that $a$ and $a^\dagger$ are bosonic annihilation and creation operators (in the language of second quantisation); are there any simpler ways to calculate the commutators of arbitrary products of these operators, without laboriously using the key bosonic identity $[a,a^\dagger]=1$ over and over again. For example... |
My understanding is that as someone/something falls into a black hole, they would get dimmer and dimmer until disappearing entirely as they cross the event horizon. Most non-radiant objects would probably become invisible to outside observers well before hitting the event horizon. But if we had something very bright (l... |
Most of the universe's nitrogen is formed in larger, main sequence stars using the CNO Cycle, right?
But I cannot find a good, specific explanation as to why $^{14}$N, with both an odd number of neutrons and protons, is formed preferentially to $^{15}$N?
|
In article The Fracton Gauge Principle complex scalar field is considered.
There's statement, that for conservation of charge one needs usual U(1) global symmetry:
$$
\phi \to e^{i\alpha}\phi \Rightarrow Q =\int d^Dx \rho
$$
For conservation of dipole moment:
$$
\phi \to e^{i\vec x \cdot \vec \lambda}\phi \Rightarrow Q... |
Imagine we've got two massless particles in an otherwise empty Newtonian world, both at the same position, with zero velocity in t0. One is without acceleration, but the other has a constant acceleration of 1.
Now, is my understanding correct that each one sees/measures the other one accelerating at the same rate, and ... |
The Problem
Let's start with the formula in Wikipedia:
I compute: $I \leqslant 4.6\times10^7 bits/eV m \cdot R \cdot E$
I chose these units because they are convenient for dealing with photons. In particular, I wish to consider a 1 m sphere containing a single 3 MHz photon, which has an energy of $1.24\times10^{-8} e... |
For a source with electromotive power $E$ with internal resistance $ r $ connected in series with a resistor $ R $, we have: $I = \frac{E}{r+R}$.
Is there any mathematical development that describes the current value when the connection is made in parallel? As well as for which $R$ value the current and the dissipated... |
It is a standard problem in quantum mechanics. For the equation
$$ -\psi'' + g \delta(x) \psi = E \psi ,$$
we integrate from $-\epsilon$ to $+\epsilon$ and thus get the boundary condition
$$ g \psi(0) = \psi'(0+) - \psi'(0-) .$$
Integrating again, we know the wave function is continuous at $x=0 $,
$$ \psi(0+)= \psi(0-)... |
What happens to the output of a beam splitter when you change the relative phase between two photons that enter from the two input ports?
In Hong-Ou-Mandel interference for a beamsplitter of the form, where I represent my outputs as $b^\dagger_1$ and $b^\dagger_2$:
$$ \begin{equation*}
\left(\begin{array}{cc}
\hat{b... |
I found this footnote in the appendix (on path integral page 333) of J. Polchinski’s string theory book. can you explain this?
|
The covariant derivative of a spinor $\psi$ is given by
$$ \nabla_\mu \psi = \partial_\mu \psi + \Omega_\mu \psi $$
where $\Omega_\mu$ is the spin connection. In equation (7.227) of Geometry, Topology and Physics by Nakahara, the spin connection is given by $$\Omega_\mu = -\frac{1}{8} \omega_{\mu ab} [\gamma^a , \gamma... |
Let's consider free Maxwell theory:
$$
L = -\frac{1}{4g^2} F^{\mu\nu}F_{\mu\nu}
$$
As I understand, one can describe external particles with help of Wilson lines:
$$
W(q,l) = e^{iq\int_l dx^\mu A_\mu}
$$
I don't understand, how to work with such operators? Could I calculate interaction between particles? Could I see ho... |
An electron, moving south, enters a magnetic field. Because of this field, the electron curves upward. We may conclude that the magnetic field must have a component:
a. towards the east.
b. towards the west.
c. downward.
d. upward.
e. towards the north.
The answer is "towards the west". I am very confused by this quest... |
Since a Farnsworth–Hirsch fusor is apparently a good fast neutron source that is simple enough to build at home, why can't it be used by rogue states or even terrorists to turn non fissile U-238, depleted Uranium that the US often shoots at its enemies in the form of shells, into fissile Plutonium-239 through neutron ... |
If light cant escape from a gravity well, how can gravity escape? we see that gravity of one object attracts another, obviously attracts itself. Is there a point that there is so much gravity that it attracts itself so hard that it turns back on itself. Is it a time energy of zero, i.e. instaneous effect on all objects... |
Let $\mathscr{H}$ be a Hilbert space and $\mathscr{H}^{n}$ be the associated $n$-fold tensor product of this Hilbert space. I'll skip the mathematical details in what follows, but my approach follows Reed & Simon's book. We can define an operator $A_{n}$, called anti-symmetric operator, which is an orthogonal projectio... |
Questions: Can any expert contrast the differences and similarities of
Supersymmetry (SUSY) v.s. BRST (global) symmetry?
(Question 1) What are the RULES and CRITERIA that having one symmetry implies that having the other symmetry? SUSY v.s. BRST (global) symmetry.
(Question 2) Is it true that we can only have a B... |
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