0
votes
0answers
3 views

Intuition for Homological Mirror Symmetry

first of all, I need to confess my ignorance with respect to any physics since I'm a mathematician. Since I'm interested in the physics intuition of the Langlands program I need to understand what ...
0
votes
0answers
4 views

Does displacement current occur in an inductor?

We have learned in school that displacement current comes about due to a change in electric field flux per time in a capacitor (Ampere-Maxwell Law). Does the same displacement current come about in an ...
-1
votes
0answers
4 views

A moving object appears to move faster towards you and slower away

First: So sorry if I'm posting this in the wrong section Also, no, this is not a question. It is a theory of mine. But, relating to the previous line, I don't know where else I would put it. Okay. ...
0
votes
0answers
4 views

Hamiltonian for semiconductor

I was wondering which terms we need in a semiconductor Hamiltonian where no transition between the valence and conduction band occur? First we would have a term describing the energy of the full ...
2
votes
2answers
13 views

The relationship between Light and Magnetic Fields

I have two questions. 1, Does light have a magnetic field? 2, If not, can it be affected by other magnetic fields?
0
votes
3answers
19 views

Where is the energy stored in destructively-interfering waves?

Let's say we have two waves moving along a string. One of them is represented by the function: $$f_1(t)=\sin(\omega t)$$ The other one is represented by a function: $$f_2(t)=-\sin(\omega (\tau-t))$$ ...
0
votes
0answers
19 views

General solution of the four-vector with each component satisfying the wave-equation

Maybe this is more appropriate for Math stackexchange, but this question regards the solution we use in order to find representation for massive / massless spin-1 particle. When $$(\Box + m^2)A_\mu = ...
1
vote
0answers
23 views

How to find creation and annihilation operators?

I get confused when trying to find this. Please describe it as simply as possible, but keep in mind I have no budget whatsoever to pay for textbooks, so here goes: How do you find the creation and ...
1
vote
0answers
12 views

Has the cosmic alignment of Earth and the Solar System been explained (CMB anisotropy)

The Cosmic Microwave Background anisotropy is currently aligning Earth and the Solar System with the largest and earliest structure of the universe. Has this been explained yet? Or are the theories ...
0
votes
0answers
19 views

Does Big Bang Cosmology imply/require infinite space?

The reason I am asking this question is because if all points in space observe recession of galaxies the same as we do from Earth, the universe would have to be infinite (or a closed sphere in 4D or ...
0
votes
3answers
37 views

Intuition behind Rocket propulsion equation

What's the intuition behind the Tsiolkovsky rocket equation: $$v - v_0 = v_{ex} \ln{\frac{m_o}{m}}.$$
3
votes
0answers
12 views

Phase Transition at Zero Temperature (Not QPT)

As is well known the Ising model exhibits a phase transition, except the one dimensional case in which the phase transition occurs strictly at $T=0$. Now I have always thought that this makes the case ...
4
votes
1answer
47 views

Solution of the wave equation

The solution of the wave equation \begin{equation} \frac{d^2y(x)}{dx^2}+k^2 \left(1+\eta(x)\right) y(x)=0 \end{equation} Can be found by using the Green function method as \begin{equation} y(x)=c_1 ...
1
vote
0answers
24 views

Spectral lines and QM

In the various presentations I've seen so far in atomic physics of series such as the Balmer series, the wavelength of each spectral line is definite - but in QM, free particles have no definite ...
1
vote
1answer
24 views

Potential Energy, Kinetic Energy, velocity, question?

A man standing a certain height above the ground throws a rock straight up with an initial velocity of $10 \:\mathrm{m/s}$. A few moments later, the rock hits the ground with a kinetic energy of ...
1
vote
1answer
29 views

What is the minimum velocity a toy car has to travel in order to survive going through a loop of radius 0.2 meters?

I tried height = 2 * radius = 2 * .2 m = .4 m. Potential energy = mgh. Kinetic Energy = $\frac{1}{2}mv^2 = mgh$ Then $\frac{1}{2}v^2 = gh$ $v = \sqrt(2gh) = 2.8 m/s$ The correct answer is 2 ...
5
votes
1answer
25 views

Why is a hexagon such a stable shape for materials?

A hexagonal lattice is famously the shape of graphene, the source of the 2010 Nobel prize. The shape also shows up in beehives and in the basalt columns of Giant's Causeway in County Antrim. ...
-1
votes
0answers
26 views

Ratio of kinetic energy concerted to internal energy [on hold]

I need help with this question: Consider four identical cars. Two of them collide head-on when both are traveling at 34 m/s. The other two collide head on when both are traveling at 25 m/s. What ...
-7
votes
0answers
20 views

Help! I need to know the category and subcategorie hlp [on hold]

i would like to know the dimensions of aXb in the relation p= b-x^2/at where p is power, x is distance and t is time
1
vote
1answer
37 views

Estimating divergence of set of vectors

I have a set of points where directions and intensities of a flow are given (in 3D). Is it possible to estimate the divergence of the flow defined by those vectors? I only need a rough estimate and I ...
1
vote
0answers
17 views

Microscopy: aperture matching and Huygen's principle

I have repeatedly read that the maximum spatial resolution of a microscope occurs when the aperture of the objective and condenser are the same. However, I don't understand why. The resolution is ...
1
vote
0answers
10 views

Have there been any experiments that have demonstrated a quantum error correcting code?

Has quantum error correction been demonstrated? I know that classical error correction has been demonstrated by [1], they correct a single bit flip error, but has anyone been able to detect and ...
3
votes
4answers
235 views

Can we change a photon's frequency in mid-air?

Can we have a light source emitting photons in the infrared range and after, lets say, 5 meters, these photons become a photon in the x-ray range? The only way I know we can change a photon's ...
1
vote
2answers
44 views

Is my answer possible? (Newtonian Third Law Pairs and Forces, Multiple Choice Word Problem)

So I recently took a test and the teacher graded my answer correct, yet my friends saw that the other answer was correct and they protest that it should be the right answer: The question goes: ...
1
vote
0answers
49 views

How can I use Einstein's field equations?

Every time I try to find the answer to this question I get redirected to different pages that ultimately do not end up answering my question. I have some understanding of Riemannian geometry but have ...
2
votes
1answer
18 views

Conductor held at constant potential

What does it mean for a conductor to be held at constant electric potential? So if my reference point is infinity, and I integrate inwards over the electric field to any point on the conductor, I will ...
0
votes
1answer
32 views

If a charge needs potential difference to move

Let's consider a circuit with a ideal source of emf and a resistor. Consider the segment of wire that connects emf with resistor. If we measure potential difference at any point of the wire, this will ...
2
votes
2answers
25 views

Directly calculate electric potential due to a spherical volume charge

Q: Say we have a uniformly charged sphere with radius $R$, total charge $Q$. Now we need to find out the electric potential inside the sphere, at a distance r from the centre. I understand that we ...
-3
votes
3answers
32 views

Given Force in vector form, how do I find work done?

A force of $F=\hat i+2\hat j-3\hat k$ is applied to a particle that moves 10 meters in the direction of $\hat i+\hat j$. How much work is done?
1
vote
4answers
341 views

What is the universal speed limit relative to? [duplicate]

If all speeds are relative, then what "governing" force is that speed limit relative to? Is there some sort of fixed or absolute grid with locations everything is compared to? Does this also mean ...
0
votes
0answers
18 views

Voltage induced in coil

Okay, so I have two coils. A ring of radius $R$ is stationary at origin. A coil of $N$ turns and area $A$ carries current $I$ and is moving along the $x$ axis such that $x = x_0 + cos(\omega t)$. ...
-2
votes
1answer
49 views

Are there nonlinear models of quantum mechanics which forbid superluminal signaling?

What would a nonlinear model of quantum mechanics which forbids superluminal signaling look like? Of course, a nonlinear $\psi$-ontic theory with entangled states could have superluminal effects upon ...
-5
votes
0answers
20 views

equilibrium pulley system [duplicate]

the question asks what mass i need for m1 to be in static equilibrium while m2 is given as 60kg. im not sure first of all if that means the two masses have to be equal in length balanced. secondly, ...
1
vote
1answer
51 views

How do I find the angle given the mass, the acceleration and the force acted on a body?

My Issue I have the mass, the horizontal acceleration and a force that acts on a body. The force forms an angle $\alpha$ of unknown degrees with the x-axis. I would like to know how I can find the ...
-1
votes
0answers
33 views

Calculating Hall Effect in Semiconductors Without the Hole Convention

** Edited to be a clearer separate question from some existing ones ** We should be able to do solid state physics without recourse to the hole convention (although less convenient: Holes in a P-type ...
-2
votes
0answers
55 views

mass needed for equilibrium in pulley system [on hold]

Question says: For what m1 will the illustrated pulley system be in static equilibrium if m2 = 60 kg? ive tried equating the changes in length where change in x1 is equal to twice the change in x2 in ...
0
votes
2answers
26 views

Why do the free electrons in N-type want to diffuse?

I'm trying to understand how a diode works and for this I've used(among other resources) the book written by Albert Malvino, Electronic Principles. Everywhere I read about this topic, it says that ...
0
votes
1answer
29 views

Force of impact of a projectile [on hold]

I need to calculate the force of impact of a projectile on a target . The projectile has been fired at an initial velocity $U$ and an angle of departure $X$. The projectile is hitting the target at an ...
1
vote
2answers
42 views

How do I find the horizontal acceleration of a body given its mass and the force that acts on it? [on hold]

My Issue I have the mass of a body and the force that is acted on a body. I am trying to calculate the horizontal acceleration and to understand how the horizontal acceleration is connected with the ...
3
votes
2answers
75 views

Do light particle/waves have a frequency? [duplicate]

I sought the answer to the question about amplitude of light waves first, but I was actually thinking about whether the wavelength is the only property of a single quanta of light. I suppose direction ...
1
vote
1answer
22 views

2 level atomic system interacting with Black body radiation. Relaxation time issue

I am studying the transient regime of a 2 level atomic system (N1,N2) interacting with a blackbody radiation from a source at constant temperature Tnr. The initial state of the atomic system is ...
0
votes
1answer
23 views

Will all the mass collapse in one place?

Will the stars, planets and everything in the universe collapse due to the gravity? Or does the constant expansion of the universe break that idea ? What will happen with the energy?
2
votes
3answers
41 views

origin of the major symmetry property of the elasticity tensor

In linear elasticity theory the stress tensor $\sigma$ is related to the strain tensor $\epsilon$ via the elastic tensor $C$. Specifically $$ \sigma_{ij} = C_{ijkl} \epsilon_{kl} $$ Because $\sigma$ ...
0
votes
0answers
34 views

Missing Matter Problem and Galactic Kinematics

This is a re-wording of an earlier problem I posted. The standard example of the Missing Mass Problem comes from the rotational profiles of galaxies. By counting up the visible matter, we extrapolate ...
0
votes
3answers
42 views

Current flow in a copper wire

How does current flow in a copper wire? If it passes through the transfer of electrons, then why does a copper wire still exist, even after losing electrons which are the fundamental particles that ...
1
vote
0answers
17 views

Lindhard function for surface plasmon

Is there anybody that knows how to calculate the Lindhard function for the surface plasmon (between the surface of two metals of different dielectrics)? What I'm looking for is to find this function ...
0
votes
1answer
26 views

Distinguishing density operators with the same diagonal elements

If I have two sources of qubits and one source produces the density matrix: $$\rho_1 = \begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}$$ and the other source produces: $$\rho_2 = ...
1
vote
0answers
40 views

A Proposed Improvement to the Diet Coke and Mentos Experiment

I am sure most of you are aware of the Diet Coke and Mentos craze - put a few mentos in a bottle of diet coke and whoosh! Equally, I am sure most of you are aware that this occurs because the gas is ...
0
votes
1answer
38 views

Independence of position and velocity in Lagrangian from the point of view of physics?

I would like to continue discussion from my previous post on time dependence of lagrangian Time dependence of the Lagrangian of a free particle?. I have also read this old post Why does calculus of ...
1
vote
2answers
43 views

Does the gravitational force of a massive, spherical body draw only towards its center of gravity, and to no other area?

Consider the premise that at the center of Earth (for example) an object would be weightless because of the relatively even distribution of mass surrounding it, and the resulting gravitational pull on ...

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