instruction stringlengths 31 24.3k |
|---|
I have a Hamiltonian with two degrees of freedom, and when I change to action angle variables, one of the action variables does not appear in the final Hamiltonian. The reason seems to be because the redundent action variable shifts the area of the second variable and therefore does not appear in the final energy expre... |
Let there be a circular loop of radius r and two protons are moving in this loop with same (and constant speed $v$). They are always at diametrically opposite ends. They complete one revolution about the centre in time $t$ [which is $2\pi r/v$]
Now the question is, what is the current flowing in the loop?
I have two p... |
We all know that at any point potential can be defined.
When we say a capacitor is charged to a certain potential we mean that the plates acquired some charge, having a potential difference between the two plates (in the case of parallel plate capacitor) equal to the potential difference of battery.
So my question is:
... |
I am currently working through Shankar's Princeiple of Quantum Mechanics
Exercise 2.8.2 is to verify that the infinitesimal transformation generated by any dynamical
variable g is a canonical transformation. (i.e. the following is a canonical transformation)
$$q_{i} \rightarrow \bar{q_{i}} = q_{i} + \epsilon \dfrac{\pa... |
Is this due to a mathematical problem that is not solved? Or could this be due to our current amount of information regarding mass and other such factors in our system?
|
So imagine we have a mass attached to a string and spin it. If angular momentum is conserved then why does the object not have a tendency to move in a curved path if the mass is suddenly let go off. Linear momentum appears to be conserved in this case at an instantaneous point where the mass $M$ would have velocity $v$... |
So according to physics laws, energy can't be created or destroyed but transformed from one form to another. But what happens when an atom flows with certain velocity and is stopped by other atom's electric attraction ?
Where does that kinetic energy go? Or let's say I throw a paper ball, and it's momentum is canceled ... |
When we think about Newton's 3rd law we assume that a change in action leads to a simultaneous change in the reaction. If there are two objects at a distance and this change happens at the same time at an inertial frame of reference , at one other this change does not happen at the same time. How can we explain that? D... |
It is well known that the Rutherford model of atom was not satisfactory since it contradicted the energy conservation law and the Maxwell equations. Indeed according to the latter the electron moving around the nucleus has to emit electromagnetic waves and hence loose energy. It has to loose all of its energy and fall ... |
In one of the papers (related to Quantum Computing) I am reading, I came across this statement which says,
An elementary result is that sets of orthogonal rank-one eigenprojectors of Hermitian operators
are not unique when the spectrum includes degenerate eigenvalues, and that uniqueness is recovered when
rank-one eig... |
This is an example of a refracting telescope:
As you can see, when passing through the eyepiece (second lens), the rays are refracted parallel to each other.
Why are they refracted parallel relative to each other? What determines if light rays will be refracted parallel to each other and why?
|
If a body is rolling without slipping is it necessary that there is friction acting on it ? I encountered a question in which there is a spherical body and a force is being applied on its top point ...so if there is only force then it should do translation motion only .. If there is friction also then it then only i... |
Could someone please help me with this question about Newton's laws and free body diagram?
"A block of mass M = 8.00 kg is located on a horizontal surface without friction. A second block of mass m = 2.00 kg is placed over the first. Neglecting possible friction between the contact surfaces, (a) what should be the acce... |
Suppose an experiment measures a quantity to be $5 \pm 0.3$ and another measures it to be $9 \pm 0.3$
What metrics can be used to emphasize and quantify the error in the estimation of uncertainties by the two experiments?
|
How exactly does a Foucault pendulum work? The usual explanation says that the plane of the oscillation of the pendulum is fixed while the earth rotates underneath. On Wikipedia, there is a demonstration of this effect, showing what it's like on the north pole. But surely that can't be right, for this gets at the heart... |
Earth orbits the Sun because the Sun's mass curves spacetime. But the Sun is 150 million kilometers away from here; how can mass curve spacetime that it's not actually in? Is that a form of action at a distance?
|
Say we have a particle in an infinite deep well that is $V(x)=\left\{\begin{array}{ll}0 & 0 \leq x \leq L \\ \infty & \text { elsewhere }\end{array}\right.$.
The energies corresponding to various states are given as $E_n=\frac{n^{2} \pi^{2} \hbar^{2}}{2 m L^{2}}$.This means that the particle can have different energies... |
Consider a time varying magnetic field. This induces an electric field upto infinity as per Faraday law and other related laws.
Is energy stored in this induced electric field?
If so, what kind of energy is it since it is said to not have a potential associated with it?
Further is it something like this - The source ... |
Say you have a mass on a string being twirled around in a circle by your fingers at a constant angular velocity , and then you increase its angular velocity . What are the forces involved that increase the angular velocity of the mass? I first thought that one needed a torque to increase the angular velocity but can o... |
In Kleppner's Mechanics, there is a problem given as
A rope of mass $M$ and length $l$ lies on a frictionless table, with
a short portion, $l_0$, hanging through a hole. Initially the rope is at rest.
Find the general equation for the length of rope hanging through hole.
In the solution, the problem is solved by usin... |
I am trying to get out of this problem, which I know to be basically obvious, but I guess I need a bit of help in: knowing if I am doing the right things, and a bit of mathematical help too.
So I have this action:
$$S = \int \text{d}t \left(\dfrac{1}{2}m\dot x^2 + \lambda x (\ddot x)^2\right)$$
Where $\lambda$ is a co... |
Assume fallowing situation:
Atom 1 travels in direction of Atom 2 with velocity (kinetic energy) vy.
As Atom 1 gets closer to Atom 2, the Atom 2 repealing forces have more impact on Atom 1.
At some point Atom 1 will stop and lose all its initial kinetic energy.
Atom 1 will be pushed back now by Atom repealing forces.
... |
Is there any procedure to add a mass to Faddeev-Popov Lagrangian density of a pure Yang-Mills theory, other than just add it from nowhere?
|
In the Cohen-Tannoudji QM book they say that the potential $$V(x)=\frac{1}{2}m\omega^2(x_1-a)^2 + \frac{1}{2}m\omega^2(x_2+a)^2 + \lambda m\omega^2(x_1-x_2)^2$$ describes two classical coupled harmonic oscillator ($a, \lambda$ are parameters). I tried to come up with a physical system with this potential and I found it... |
I have been trying to derive the expressions of partial derivatives of unit vectors with respect to each other in the spherical coordinate system. I was able to get all of them except $\frac{\partial \hat{\phi}}{\partial\theta}$
Note: I am using the mathematics convention of denoting azimuthal angle as $\phi$ and polar... |
Can we say that two wavefunctions $\psi(x)$ and $e^{i\theta(x)}\psi(x)$ are the same even when $\theta$ depends on position $x$? Are they also same as $e^{i\phi}\psi(x)$ where $\phi$ is independent of $x$?
|
Velocity and acceleration are directly proportional to each other but in the case of throwing a ball up , at the top velocity is zero but acceleration is there. why?
|
In section 2 of 'All possible generators of supersymmetries of the S-matrix', an operator $G$ on the Hilbert space of states is introduced that has to commute with the S-matrix and act additively on multiple particle states. They state that this requirements are equivalent to $G$ inducing an infinitesimal transformati... |
I'm supposed to prove that the uncertainty of the annihilation operator of the harmonic oscillator, given by
$$\Delta \hat a=\sqrt{\langle\hat{a}^{2}\rangle-\langle\hat{a}\rangle^{2}} \tag1$$
doesn't change over time.
My attempt at a solution
What I have tried is to calculate the derivatives of $\langle\hat{a}^{2}\ran... |
When I practise problems, I come across ideal situations like constant velocities, constant accelerations, etc. But in real situations, objects usually don't magically gain momentum or acquire acceleration.
Correct me if I'm wrong, but velocities often fluctuate due to a rate of change, i.e., acceleration, and accelera... |
In the book of Lowell Brown on QFT its mentioned that
$$\int_{\mathbb{R}^2} \frac{dq'dp'}{2\pi} e^{(-z^{*}z + z^{*}_1z + z^{*}z_2)} = e^{z^{*}_1z_2}\tag{1.8.12}$$
where $$z=\frac{q'+ip'}{\sqrt{2}} \qquad \tag{1.8.1}$$ is the eigenvalue of a coherent state.
In the next paragraph, its mentioned that
the transformation f... |
The Polyakov action is given by
$$
S_{P} = -\frac{T}{2} \int d^2\sigma \sqrt{h} h^{\mu \nu} \gamma_{\mu \nu}
\tag{1}$$
where $h_{\mu \nu}$ is the dynamical metric and $\gamma_{\mu \nu}$ is the induced metric. It is well known that this is equivalent to the Nambu-Goto Action
$$
S_{NG} = -T \int d^2\sigma \sqrt{\gamma}.\... |
When reading Mechanism for ordinary-sterile neutrino mixing it is stated in the abstract that:
"(...)sterile neutrinos can occur only if Dirac and Majorana mass terms exist which are both small and comparable."
What is the meaning of comparable in this context? Does it means both mass terms must be on a similar scale (... |
Here, the mean power of thermal noise is given by:
$P = 4kT$ ($T$ = temperature, $k$ = Boltzmann’s constant)
And the voltage in the instrument is, of course, thus given by:
$V^2/R = 4kT$
The thermal noise, and therefore the voltage, is distributed as a Gaussian around this mean, with RMS given by:
RMS = $4RkTB$ ($B$ = ... |
Please tell me if I'm wrong with an explanation (A Level explanation please).
You feel the heaviest at the bottom of the ferris wheel because in order for there to be a centripetal force, the normal force has to increase to provide the force. Therefore, your weight decreases because Newton Third's Law states that the t... |
According to my physics book, all materials could manifest diamagnetic effects (it is a consequence of Faraday's law of electromagnetic induction). However due to the presence of intrinsic magnetic moments of molecules, the effects of diamagnetism are weak.
Anyway I am not sure why.
|
Can somebody explain to me why we measure the spring potential energy from the point it's unstretched? I've been puzzled with that and I've tried to prove it mathematically but I don't understand why we should measure it from this particular point .
|
The motivation behind this question comes from an unsettling statement said in an electrical engineering course that if you have a ferromagnetic core with a coil looped around it in one limb with an air gap at the other limb, the two separate faces across the air gap experience a force that tries to "increase the store... |
I'm reading through Kerson Huang's presentation of the Onsager solution. We end up determining that the natural log of the partition function is
$$\ln Z = \frac{1}{2}\ln (\frac{2 \cosh^2(2 \beta \epsilon)}{\sinh (2 \beta \epsilon)}) + \frac{1}{2 \pi}\int_0^{\pi}d\phi \ln \frac{1}{2}(1+\sqrt{1-\kappa^2 \sin^2 \phi})$$
w... |
Consider the case where a P-type semiconductor and an N-type semiconductor are placed in perfect vacuum. Now, the two junctions are brought together.
In the time immediately after they are brought in contact (say the first 1 micro seconds after they are brought in contact), the electrons from the N-side will diffuse i... |
I happen to live on an infinite flat Earth. It has a constant uniform gravitational field extending above it. Don’t I still observe relativistic effects such as light not traveling in straight lines, even though there doesn’t seem to be any spacetime 'curvature' involved anywhere?
|
Let's assume there is an astronaut with a very long rope trailing behind him. As he approaches a very large black hole, he can look back and see the rope behind him trailing off into the distance.
What would he see after he crosses the event horizon and looks back along the rope while a portion of the rope is still out... |
I have a small tritium key chain light I got for my birthday. It will glow for decades, so I thought it would be fun to try to figure out how bright it is in lumens, and how much energy is stored in it. I have looked on google, but there is just nothing I can find on this subject. My first approach was to treat it like... |
I have seen it said that if we want to avoid violations of causality (I can see why we would want to avoid that!), we need the information-transfer "speed limit" of c.
I presume(?) this assumes some other stuff in the model though? Consider a 2D universe of discs moving uniformly and bouncing off each other elastically... |
Given a holomorphic field $H(z)$ with OPE: $$H(z)H(0)\sim -\ln z$$ What is the most smart way to calculate the OPE's of the exponential operators $e^{\pm iH(z)}$, given as follows? $$e^{iH(z)}e^{-iH(0)} \sim \frac{1}{z},$$ $$e^{iH(z)}e^{iH(0)} \sim 0,$$ $$e^{-iH(z)}e^{-iH(0)} \sim 0.$$ Should I expand $\exp$ and do ter... |
So I’m in high school and I’m doing research on fluid dynamics. However I can’t find any references for how a fluid flow expands when it leaves a nozzle/hole.
For exemple, when I blow, I can feel the flow in a small region of my hand when it’s close to my mouth, but if I move my hand just a feel centimeters away, the c... |
The second equation of the image above shows the position $y$, which describes the position $y$ of a wave function given an input $x$. Furthermore, we now want to see the wave is traveling over time.
Hence,
$\sin(\delta x)$
$\delta x = x_{f} - x_{i}$
Because of the relationship of $\delta x$, I would argue:
$y(x,t) = ... |
I attempt to understand the $0$-dimensional QFT from these QFT lecture notes by Ronald Kleiss from 2019. The author defines the generating function $Z(J)$ and its logarithm in the following way.
$$Z(J) = \sum_{n\geq 0} G_n \frac{J^n}{n!}, \quad W(J) = \ln(Z(J)) = \sum_{n\geq 0} C_n \frac{J^n}{n!}.$$
Exercise 1 (page no... |
I was learning about wave motion and how in transverse waves, each particle executes SHM up and down. If that is the case, how is it so that energy is still transferred onto the next particle? The logical answer should be that it disturbs the other particle, but if it moves up and down how does that happen?
|
From wikipedia thermodynamic activity is given as
$$ a = \exp \left(\frac{\mu - \mu_{0}} {RT}\right)$$
which becomes,
$$ RT\ln(a) = \mu - \mu_{0}\tag{1}$$
And i have to do a calculation where activity is given as
$$ RT\ln(a) = \left (\frac{\partial{G_m}}{\partial{N_A}}\right)_{T,P,N_{B}} = G_{M} + (1-c) \left(\frac{\pa... |
Suppose I have two mechanical oscillators $a(t), b(t)$, coupled through the interaction $V_\text{int} = \mu^2 a(t) b(t)$. Is there a simple way to express the rate of energy transfer from $a$ to $b$ using only $V_\text{int}$? Something like $\partial_t V_\text{int}$ would have the correct units, but it is symmetric in ... |
I saw a question in my physics book asking for the time when all the three particles (each at the corner of an equilateral triangle and each having constant velocity v along the sides of the triangle) meet at a common point.
I can't find the reason why these particles should meet at a common point.
What I think is tha... |
I was following along my Physics textbook for the derivation of the kinetic energy associated with a wavelength of the wave, but
$\frac{1}{4k}sin(2k\lambda)$
disappeared at the end of the equation. Why would it be 0? I am not able to reason out why the wavenumber or the wavelength for the sin function to be 0 in order... |
What is relative angular velocity of one point, say A, with respect to another point, say B? Both the points lie on the same rigid body which is rotating with constant angular velocity ω about a fixed axis.
Edit:
Here is the figure
The above body is rigid. For simplicity consider the rod joining A and B to be massless... |
I've done some research, and found some videos and articles on how I could find the resonant frequency of normal objects - By hitting them, and then finding the frequency using a software. But the problem with a glass pane, is that it doesn't ring, so it's hard to find the resonant frequency, as the software only catch... |
How would you explain the concept and applications of Feynman Diagrams to a high school kid?
|
Special relativity teach us there is no way to deduce which body is moving and which one is standing still and that it is all frame of reference dependent. But in the case of the two twins that are moving at different speeds we can say both are moving away from each other and then getting close or we can say one was st... |
IFMIF neutrons source use $^7\rm Li$ as target for deuterons. Neutrons are emitted.
But what happens to protons? Why they stay in the target?
|
Two blocks of masses $m_{1}$ and $m_{2}$ are kept on a smooth horizontal surface. A spring of mass $m$ and natural length $L$ connects the two blocks as shown in the figure. At t=0, $m_1$ and $m_{2}$ are given velocities $v_{1}$ and $v_{2}$. Just after t=0, what is the value of $x$ so that the point $P$ remains at res... |
You bore straight down inside the Earth. The further you go, the less gravity you experience, because mass above you grow, and mass below you shrink. At the (ideal) center, gravity cancels out to zero, as you experience equal mass all around you. Right?
So, centrifugal force must, at some point, overpower the diminishi... |
I understand that, from the state-operator correspondence, $$|0;p\rangle \;=\;:e^{ip.X(0,0)}: |0\rangle.$$
This is given in Polchinski, equation (2.8.9).
I am now trying to understand the S-matrix for $2\times$tachyon $\rightarrow$ $2\times$tachyon scattering. My understanding is as follows.
We seek to calculate $\lang... |
I saw a statement saying that a direct current of a units can be superimposed with an alternating current of bsin(wt) but this seems a bit contradicting as one quantity is continuously varying will other is constant. It seems like adding speed to velocity. So is there a way I can convince myself
|
When reading about the 2015 Nobel prize and how this led to the possibility of the existence of sterile neutrinos I am told that:
"(...) three active neutrinos $\nu_e$, $\nu_\mu$, $\nu_\tau$, are superpositions of three massive neutrinos $\nu_1 $, $\nu_2 $ ,$\nu_3 $ with respective masses $m_1$, $m_2$, $m_3$"(...)
I kn... |
Is it possible for a given spectrum to calculate an artificial Goethe spectrum (sometimes also refereed to as edge spectrum or shadow spectrum)?
Hereby a Goethe spectrum would describe the spacial distribution of intensities when light caters at an edge, an example is given with this image and this image used on th Wik... |
How can one find the rate of collision per unit area with the walls of a gas container given the distribution as $$d N\left(v_{x}\right)=N\left(\frac{m}{2 \pi k T}\right)^{1 / 2} e^{-m v_{x}^{2} / 2 k T} d v_{x} \quad.$$ I tried to find it but I end up with an extra factor of $1/2$ in the end. The correct expression be... |
Two charged metal spheres L and M are placed in contact.
Before contact L had a net charge of +10e and M a net charge of -10e.
A positively charged rod is brought close to L, but does not touch it.
The two spheres are then separated and the rod is withdrawn.
What is then the charge on each sphere?
I think that when the... |
I learned that renormalization used in the standard model while working is using some math that has not yet been proved. Put very simple renormalization is subtracting an infinite number from another infinite number to get a finite number. I learned during a lecture on quantum field theory that there is no mathematical... |
or a myopic swimmer with a prescription of -7.0 diopters, what should the radii of curvature of the lens surfaces be if the goggles are made from a high index plastic of n = 1.6? First, what is the radius of curvature of the outer surface (furthest from the eye)? If the surface is flat, enter 'i' for an infinite radius... |
I am reading Asboth, Oroszlany, Palyi 's lecture notes on Topological insulators. I am having some diffculty with the mathematics on page 4, Section 1.2.1.
We have the SSH hamiltonian:
$$
\hat H_{bulk} = \sum_{m=1}^N(v|m, B\rangle\langle m, A|+w|(m\text{ mod }N)+1, A\rangle\langle m, B|)+\text{h.c.}
$$
and we want to f... |
I know there are three "masses".
"inertial mass", based on Newtonian Mechanics
"rest mass" and "relativistic mass", based on relativity
Anyone can explain three of these in a relatively easy way? I'm confused
|
Would there be a way to test how velocity affects the coefficient of kinetic friction using some sort of mass pulley experiment?
|
We all know when I hit glass with a stone, the glass will shatter, the stone will most likely survive.
If I hit a rubber cube with the same stone, both would probably survive and I might get a stone in my face...
I have a single question how do I calculate that?
Since it was asked I am trying to create a simulation gam... |
I have a rather technical question about lifetimes and propagators. The definition of the single particle propagator is:
$g(r, r', t, t') = -i <\Psi_{0}^{N}|T[\psi(t, r)\psi^{\dagger}(t', r')]|\Psi_{0}^{N}> = - i \theta(t-t') <\Psi_{0}^{N}|\psi(t, r)\psi^{\dagger}(t', r')|\Psi_{0}^{N}> \mp i \theta(t'-t) <\Psi_{0}^{N}|... |
I was studying identical particles in Quantum Mechanics, when I came across the notion of the 'exchange operator' acting on a two-particle wavefunction, $\psi_(x_1, x_2)$, in one dimension: $$ P_{12}\,\psi(x_1, x_2) = \psi(x_2, x_1)$$
The way I understand, all that $P_{12}$ does is switch the positions of the two parti... |
Some questions about Wigner's friend. In wiki, this system is described as two state spin system $|0\rangle_S$, $|1\rangle_S$ and assume it is in a superposition state $\alpha|0\rangle_S$ +$\beta|1\rangle_S$. From the friend's point of view, when the friend measure the spin in $|0\rangle_S$, $|1\rangle_S$ basis, spin ... |
Fanno flows are a very interesting phenomenon in fluid dynamics: the flow (steady, 1D, adiabatic) is moving in a pipe where friction forces are not negligible. Due to the second law of thermodynamics, if the inlet flow is subsonic, the presence of friction in this case decreases the flow's temperature and increases its... |
When solving a constrained motion (particularily in wedge constraints) problem we often, in order to solve it quickly, use a trick or formula which goes by
$$\sum \vec N \cdot \vec a = 0$$
where $\vec N$ is the normal force acting on a body and $\vec a$ is its
acceleration.
What I wanted to know is how far is this form... |
Well we know that if you are inside a car you are shielded from electric field due to lightning. But my question is if you are inside the car and touching any metal which is covering the outside of car , will you get shock or not .
I mean similarly if we are inside a large spherical hollow conductor having charge Q, t... |
I was investigating the effects of heated wall materials on outdoor air temperature and indoor air temperature with a certain software. The system is as the following:
1x1x1 meter cube of outdoor air
1x1x0.15 meter cube of brick wall
1x1x1 meter cube of indoor air
The radiation source was set on the outdoor side of t... |
If we lit a single fire that was fueled by a substance that burns at 500°F, then around that fire we lit directly against it another fire surrounding the original one. This second fire's fuel also burns at 500°F. Would the original fire increase in temperature? If yes, is there any topic related to this event that I ca... |
I am going through this paper on the Big Bang singularity using an M(atrix) theory description. A type IIA superstring moves through a linear dilaton background in ten dimensional Minkowski space and couples to the dilaton field as $g_{s} = \exp(-QX^{+})$ where $Q$ is a constant. With this background, the dilatino feel... |
My teacher posed this question and it got me thinking;
The electric flux through the curved surface area of a hemisphere of radius R when it is placed in a uniform electric field is?
Before this, I was taught the definition of flux as the number of field lines passing perpendicularly through an area. (If the lines ar... |
How to make the connection between the energy released by the fission of uranium and the power of a nuclear plant ?
How to vary the power in a nuclear plant since the energy released by fission of uranium is a constant given by nature (physics) ?
(I know that the power is the derivated of the energy by the time.)
|
I am trying to derive the R-N solution and i am following Blau's notes (to be found here http://www.blau.itp.unibe.ch/newlecturesGR.pdf) pages 677-679. With the same metric ansatz:
$$ ds^2 = -A(r)dt^2 + B(r)dr^2 + r^2 d\Omega^2 $$
and four potential ansatz:
$$A_{\alpha} = (-\phi(r),0,0,0).$$
i am trying to calculate th... |
Consider the an infinitesimal coordinate transformation $x^{\mu}\mapsto x'^{\mu}:=x^{\mu}+\epsilon^{\mu}(x)$. The appropriate changes in the metric manifest as:
$$g'_{\mu\nu}=\frac{\partial x^{\alpha}}{\partial x'^{\mu}}\frac{\partial x^{\beta}}{\partial x'^{\nu}}g_{\alpha\beta}= g_{\mu\nu}-(\partial_{\mu}\epsilon_{\nu... |
We are also to assume that air resistance provides a small perturbation to the motion, which is largely determined by the force of gravity.
Suppose that air resistance is proportional to the square of the velocity.
I know that the change of energy is equal to the work done on the system, so
$$\Delta E = \int_{0}^t F_{a... |
I would like to refer to the answer by John Rennie to the following (previously asked) question:
How to derive the phase difference of a standing wave?
It's a short one so please skim thorugh that.
Ok, I understand that $\Delta \phi = k(x_2-x_1)$, and that was what I expected.
But please see the problem below with whic... |
This question has arisen out of a previous question regarding the various approximations in optical diffraction theory, and when they can each be applied.
I would like to know the steps that must be taken to numerically calculate the diffracted field observed after an arbitrary aperture geomerty, at small distances fro... |
I've a short question about basis transformations in QM. Suppose I have two bases $\{|{\phi_n}\rangle\}$ and $\{|{\phi_n'}\rangle\}$. For brevity, we can make them orthonormal. I know that any state vector can be expanded in terms of both bases:
$$|\psi\rangle = \sum_n |\phi_n\rangle \langle \phi_n | \psi \rangle = \su... |
Is it compulsory for a mercury thermometer to be straight?
|
Apart from the interception by a sufficiently powerful laser, what would be the means to neutralize (kill/repel) an insect in full flight and indoors (so no water, pepper, etc), and without touching it by physical contact.
Would ultra-targeted ultrasound be possible?
|
Is it possible to write all Maxwell's equations only in terms of $\vec{E}$ (without $\vec{B}$)? The common formulation of Electromagnetism is governed by the equations below:
The Lorentz Force: $$\vec{F} = q( \vec{E} + \vec{v} \times \vec{B}) $$
Maxwell's equations:
$$\vec{\nabla} \cdot \vec{E} = \frac{\rho}{\epsilo... |
There are many possible decay products for uranium 235 fission.
I'm interested in the average value of the energy released (not an order of magnitude : a rather "precise" value of the average)
I know that binding energy of uranium 235 is 7.59 MeV per nucleon.
I know that average binding energy of decay products is 8.5 ... |
By a popular definition, "entropy quantifies the number Ω of microscopic configurations (known as microstates) that are consistent with the macroscopic quantities that characterize the system (such as its volume, pressure and temperature). Under the assumption that each microstate is equally probable, the entropy S is ... |
I don't understand how to derive the chain of equalities right after equation (3.31):
We are told $$\frac{\delta \phi}{\delta \xi^\nu} = \partial_\nu \phi\tag{3.30}$$ and $$\frac{\delta \mathcal{L}}{\delta \xi^\nu} = \partial_\nu \mathcal{L}\tag{3.31},$$ and I'm confused about the line immediately following it:
"Since ... |
What is often called the Indistinguishability Postulate is expressed in (at least) two different ways depending on the textbook.
For any normalized composite states of N identical particles $|\psi \rangle$ in $H^{N}$, and observable O on $H^{N}$, and any permutation operator $P$ in the permutation group $S_{N}$,
$\lan... |
I have heard that not even black holes last forever, because of Hawking radiation. But what about elementary particles? Will an electron, for example, exist for all time?
|
An observer $A$ standing on the circumference of a disc rotating with an uniform angular velocity $\omega = 1$ units , and radius $r=1$ units observes a person $B$ at rest w.r.t ground.Given the $\angle \theta = 30^\circ $ as shown in the figure
Find out the,
relative velocity of $A$ w.r.t $B$
relative velocity of $B$... |
The text I am reading claims that if there exists a symmetry generated by $Q$, and under this transformation an operator transforms by$$f\rightarrow f +\delta f,$$ then by Noether's theorem
$$\delta f = i\epsilon[Q, f].$$
However, this is not the Noether's theorem I am used to, which I see to be similar to this stateme... |
I can understand that the role of electrons and protons are not interchangeable for elements heavier than Hydrogen, because there is no nuclear force to keep the charged electrons together in a nucleus, but at least for the Hydrogen atom, it should be possible to exchange the proton and the electron? Is there a reason ... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.