0
votes
0answers
6 views

Euler-Lagrange equations in quantum field theory

Hey I'm trying to learn some quantum field theory...My question is do "quantum field operators" have to obey the Euler-Lagrange equation? If yes why do they have to? Is there a "quantum version" of ...
0
votes
0answers
5 views

Functional variation of potential in integral form

I am trying to vary the following action, $$ S=\int_{t_0}^{t_1} \text{d}t\,(v^\mu v^\nu g_{\mu\nu} + V(t)) =\int_{t_0}^{t_1}\text{d}t\,(v^\mu v^\nu g_{\mu\nu} + \int_{t_0}^t\text{d}s T_\mu v^\mu) $$ ...
0
votes
0answers
12 views

Why do Newton's laws hold in a normal and tangential coordinate system?

In my book it says: 'When applying the equations of motions, it is important that the acceleration of a particle be measured with respect to a reference frame that is either fixed or translates with ...
0
votes
0answers
10 views

general relativity vs graviton discovery

Will the discovery of the graviton lead to the redundancy of general relativity even though it has been so well established. If not, will it mean that gravity will have two separate theories that ...
-1
votes
0answers
15 views

Inversed square law (destroying a hypothetical solar system)

Here is my question, say it was possible to have enough antimatter as the explosive of choice to achieve such a feat, and that a black hole isn't formed the magnitude of energy at the origin. How much ...
0
votes
0answers
8 views

What is the tension on the horizontal rope in this conical pendulum setup?

A rope is attached to the top of a straight pole. A person of 890N and a seat of 201 N are attached to the end of this rope. The person rotates 37.4 revolutions/min in the horizontal plane while the ...
0
votes
1answer
12 views

Potential step and tunnelling

Imagine a particle with energy $E$ heading towards a potential step with height $V_0$ where $E<V_0$. The particle's wave function is oscillatory before the boundary and exponentially decaying in ...
0
votes
0answers
6 views

Wear rate with sliding speed

I read so many research studying the effects of sliding speed on wear using pin on ring testing machine all of papers said: when the sliding speed increase the wear rate will increase because the true ...
0
votes
1answer
16 views

Propulsion system

Can a propulsion system be made by facing two air ionizers towards each other, accelerating the ions with fans, and having them repel each other? Something like this: Thanks in advance
0
votes
1answer
25 views

Direction of travel in universe

When observe the universe we see that galaxies are much closer than they are at this very moment because of the time it takes for the light to reach us. However do we see this phenomenon in every ...
2
votes
0answers
15 views

Eigenvalues of spherical harmonics in d dimensions

I'm working on the Schrodinger equation for a hydrogen atom in a $d$-dimensional space, so I'm interested in the possible eigenvalues of the angular momentum part of the $d$-dimensional Laplace ...
0
votes
0answers
9 views

Charge density on two hemispheres, enclosing a conducting sphere

Two uniformly charged non conducting hemispherical shells each having uniform charge density $\sigma$ and radius $R$ form a complete sphere (not stuck together) and surround a concentric spherical ...
-1
votes
1answer
25 views

Is uniqueness a fundamental property of nature?

The Laws of nature are universally applicable and at every point in force. Together they shape our universe but are all "shapes" unique? For example, is it possible that there is a second identical ...
0
votes
0answers
11 views

triboelectric effect at a liquid-liquid boundary?

In reading up on the triboelectric effect, most experiments deal with solid-solid interfaces. I've found some studies regarding solid-liquid boundaries, and even some engineering manuals outlining the ...
0
votes
1answer
13 views

What is the refractive index for partially ionized plasma plasma (mixture of electrons ions and atoms)?

I asked a question earlier, why ions are not included in refractive index of plasma . What I do not understand is how a refractive index of plasma can be formed mathematically that is just partially ...
1
vote
2answers
40 views

How well-defined is the infinite-sheet-of-mass computation?

When computing the gravitational force from an infinite plane (or the electrical field from an infinite sheet of charge), it is standard to begin by making a symmetry argument to say that the ...
0
votes
2answers
33 views

Projection of a tensor

Consider the following tensor (abstract index notation, e.g. Wald's) $B_{ab}$ and timelike vector field $X^{a}$ such that $X^aX_a=-1$ and \begin{equation} B_{ab}=\nabla_bX^a \end{equation} Then one ...
0
votes
0answers
35 views

Why do we integrate in the following derivation?

Electric potential due to a point charge. Let a point O have charge $q$ at a distance $x$ from point A and at a distance $r$ from point P ($r<x$). Suppose a test charge $q_1$ is placed at A force ...
0
votes
0answers
21 views

Can we see interference if move screen?

In interference using electrons in double slit experiment, we cannot use light source, as it disturbs apparatus. But, can't we simply move screen towards and away from screen, to know where they ...
-2
votes
0answers
18 views

Uncertainty principle-QM [duplicate]

I some trouble understanding the uncertainty principle. I understand most of the math derivation but not the physics. Is there any intuitive explanation of this idea, and why is the uncertanty does ...
0
votes
0answers
44 views

(1+1)-General Relativity

Goodevening everyone, my question is: What is the interest of studying the (1+1)dimension General Relativity? Can you explain please? Thank's in advance!
0
votes
1answer
24 views

Force of water hitting a wall

If you had a 8" pipe with 500psi stream of water exiting it and hitting a wall at 90 degrees 8 feet away, what would the force of the water on the wall be? Thank you all. Non-mathematician.
1
vote
1answer
23 views

Projectile motion with air friction force/resistance

We have to find the x (the distance, if you didn't know that then I'm not sure if you should be doing this problem) that the projectile travel during the time in the air until the time it hits the ...
0
votes
1answer
25 views

Is this possible to create a 1D or 2D thing in real?

We are living in the fourth dimension(time).So we can now travel through the third dimension. Now just imagine to make a 1 dimension thing, A line in real world. If I draw a line in paper with a ...
2
votes
1answer
34 views

A puzzler in induction and special relativity

Some reading I was doing jogged my memory about a puzzle in E&M that hit me back in my undergrad days, but I just let it go at the time and never found an answer. A pretty common undergrad E&...
-1
votes
0answers
26 views

General relativity applications other than gravity

Do the Einstein field equations successfully predict/describe physical processes other than gravitational ones?
0
votes
0answers
19 views

Can orbiting a black hole 99.99% speed of light make other object with relatively fast clock travel faster than light, relative to me?

If i orbit a black hole, 99.9% speed of light, time for me is moving slowly, relative to me, planet earth is aging fast, and i have traveled 10 years into the future(relatively) in 1 second, suppose ...
1
vote
2answers
40 views

How is one element capable of radiating (almost) every wavelength?

Black bodies are considered as emitting all wavelengths. A incandescent light bulb has (nearly/almost) also the continuous blackbody spectrum near-perfect color rendition. In this bulb is only one ...
0
votes
1answer
20 views

Strings acting on a car

I am trying to solve a problem but I can't figure out why the answer comes out to be what it is: A man of 80kg enters a car and compresses the 4 strings of the car, causing a change of 1,2cm from ...
1
vote
1answer
13 views

Does resonator will always dampen the driving oscillator?

I was doing a question about resonance of sound box connecting to a tuning fork. It asks why the sound lasts for a shorter time with sound box than if the tuning fork is struck identically without the ...
2
votes
0answers
39 views

Intuitive analysis of gradient, divergence, curl

I have read the most basic and important part of vector calculus gradient,divergence,curl these three things are too important to analyse a vector field and I have gone through the physical meaning of ...
0
votes
1answer
34 views

Such a huge mass for Higgs boson? And how can it, as a quantum, decay?

With a mass of 126GeV/c2 Higgs boson would have a mass slightly greater than a caesium atom. Isn't it too much? Wouldn't be in this way the ubiquitous Higgs field so dense to cause problems for the ...
0
votes
0answers
19 views

How small can a sample size be of space to detect space-time curvature?

What is the minimal sample size of space necessary to detect space-time curvature?
0
votes
1answer
16 views

Derivation of photon propagator from EM Lagrangian

I am following Ryder's Quantum Field Theory. In chapter 7, in order to derive the photon propagator, he first derives eq. 7.4 $$\mathcal{L}=\dfrac{1}{2}A^\mu[g_{\mu\nu}\partial^2-\partial_\mu\partial_\...
0
votes
2answers
33 views

What is a magnetic line of force?

Do magnetic limes of force 'flow'? If so, what is it that is flowing? What is the 'line of force' composed of?
1
vote
0answers
26 views

Bernoulli equation and pumps

I have a doubt on the use of Bernoulli equation for pumps. Consider the situation in the picture. I marked different points: $1$ on the surface of first tank, $2$ in the exit from first tank, $3$ ...
0
votes
0answers
26 views

Problem in thermodynamics

There is a 500 watt heater and a ton of wood. How much will the temperature of the wood increase over the course of 6 hours? P = 500 W m = 1000 kg t = 6 h = 21600 s c_wood= 1700 J/kg E = P * t ...
0
votes
1answer
8 views

Nuclear physics study materials

I'm currently a ChemE undergraduate student and wish to pursue masters in nuclear engineering. Can you suggest some introductory reading material so that I can get acquainted with nuclear engineering ...
1
vote
2answers
21 views

Compressibility factor and deviation from ideal gas behaviour

I have recently started to study the deviation of ideal gas behavior. The source from which I am reading doesn't give me an intuitive understanding of the compressibility factor. I dont understand how ...
0
votes
0answers
13 views

(Iso)spin coupling of three particles

I need Isospin calculations to predict the relative amount of strong decays, namely $D^{**0}\to D\pi\pi$, where the $D$ and $\pi$ can be charged or neutral. My problem is the order of contracting the ...
0
votes
0answers
18 views

Communication between two LEO satellites

Anybody have any idea about any mathematical model to allow communication between two LEO Satellites is possible in space, where two LEO satellites do not know their positions in two different polar ...
0
votes
0answers
14 views

Video lectures for studying graduate level kinetic theory

As the title says it all, I require Video lectures for studying graduate level kinetic theory including but not limited to detailed analysis of viscosity and conductivity, diffusion and Maxwell's ...
1
vote
0answers
41 views

Generalisation of a particle in QFT

In classical mechanics, we assumed a particle to have a definite momentum and a definite position. Afterwards, with Quantum mechanics, we gave up the concept of a time-dependend position and momentum, ...
0
votes
1answer
36 views

Even when the drift velocity of the electrons is very small, how is current in the circuit established immediately?

So I have this question in my textbook and Ive also got it in my test. Ive written a wrong answer. My friend wrote the drift velocities of each particle add up and he got full marks. Is it right? Can ...
1
vote
1answer
19 views

How can I calculate the torque on a body resulting from a spinning propeller?

If a quadcopter has all of its propellers spinning on the same direction, the body of the quad will obviously start spinning in the another direction. I know how to calculate the torque acting on a ...
0
votes
1answer
29 views

A question about heisenberg uncertainity principle

In my textbook about atomic structure we have a brief part about Heisenberg uncertainty principle. While the derivation was not given in the book which simply stated Heisenberg as $\Delta x\, \Delta p\...
2
votes
0answers
15 views

How rigorous is the description of the edge of the Kitaev Honeycomb as a CFT?

My understanding of the Kitaev honeycomb model is that high-level abstract properties (anyons and their braid statistics) can be seen to emerge the microscopics of the model (fermions and vortices). ...
3
votes
0answers
42 views

Lagrangian of classical electromagnetism without $A_{\mu}$ field [duplicate]

Is there a Lagrangian reproducing Maxwell's equations without the use of the scalar and vector potential? Obviously $\mathcal{L} = -\frac14F_{\mu \nu}F^{\mu \nu}$ doesn't work since in terms of $E$ ...
1
vote
1answer
37 views

Why don't windows and mirrors cancel light?

So I understand that when light goes from a material of low index to a material of higher index it picks up a phase change of 180. Most glass has an index of around 1.5. I know that when light goes ...
-1
votes
0answers
16 views

Force needed question [on hold]

I am standing on a ladder 24 ft. in the air,The angle of the ladder is 65 degrees and I weigh 200 lbs and the ladder weighs 65 lbs ,How much force would be needed to lift the ladder off the ground,...

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