1
vote
2answers
86 views

What happens to the physical properties of electrons after diffraction?

Particle Wave duality shows us that waves and particles are the same thing. Therefore electrons can be viewed as both particles and waves. The wave properties of electrons can be seen in the double ...
7
votes
2answers
258 views

Can we show that time is orthogonal to space?

It's easy to show that the time we measure is "in a different direction" from the space directions we measure. However, it's not immediately obvious to me that these directions are orthogonal. How do ...
2
votes
1answer
134 views

How many kinds of topological degeneracy are there?

Here I want to summarize the various kinds of topological ground-state degeneracy in condensed matter physics and want to know whether there exists any other kind of topological degeneracy. For ...
4
votes
0answers
80 views

Free path distribution

I'm studying statistical mechanics, and I'm trying to resolve some problem known from my thermodynamics course. So I want to calculate mean free path for particles with a concentration $n$ and ...
4
votes
0answers
66 views

What is the radius of convergence of the Fefferman-Graham expansion?

There is this general result that for any metric $ds^2$ that is asymptotically $AdS_{d+1}$, then there is a coordinate system in which $$ ds^2 = \frac{1}{r^2}(dr^2 + g_{ij}(r,x^k)dx^i dx^j) $$ where ...
4
votes
2answers
246 views

Difference between Scattering and Fluorescence

It is often said that substances, objects have color because they selectively absorb all color of sunlight except one. The wavelength that is not absorbed reaches our eyes and we perceive it as ...
5
votes
4answers
238 views

Fermion boundary conditions at finite temperature

In a finite temperature QFT, fermions must obey anti-periodic boundary conditions. What is the reason for this?
5
votes
1answer
171 views

Arbitrary Complex Powers of Ladder Operators

Given the following pair of operators $a$ and $a^{\dagger}$ that satisfy the usual bosonic CCR: $$[a,a]=[a^{\dagger},a^{\dagger}] = 0;\ [a,a^{\dagger}] = 1$$ For what values of $\alpha \in\mathbb C$ ...
4
votes
1answer
113 views

How do aspherical gravitational monopoles look like?

I was recently pointed by laboussoleestmonpays to a beautiful paper from some time ago, Aspherical gravitational monopoles. Alain Connes, Thibault Damour and Pierre Fayet. Nucl. Phys. B 490 no. ...
3
votes
1answer
125 views

How is relativistic N-body simulation possible without knowing the entire histories of each particle?

In n-body simulation you need to know the positions of the particles in order to calculate the force between them. The new velocity of each particle can then be calculated given a simulation timestep ...
0
votes
1answer
117 views

What are the experimental observations behind the first principle of thermodynamics?

As far as I understand it, the first principle of thermodynamics is a mere definition of the quantity “Heat”: $$\text d Q: = \text d L + \text d U.$$ This is somewhat the point of view taken in ...
0
votes
1answer
754 views

How to evaluate, how much current flows in the circuit?

Please take into advisement, that I'm quite a beginner in subjects of physics and especially about electricity. Lately I've decided, that I want to learn more on basics of electronics and I've started ...
3
votes
1answer
163 views

Will a relativistic rocket be destroyed by incident photons?

I have read, that as a rocket approaches light speed, objects in front of it become blue shifted and also intensity of light increases. Does this mean that at some point any rocket will be destroyed, ...
1
vote
2answers
79 views

What is the effect of phase transition on the thermodynamic state variables of a material?

When a material undergoes a phase transition, it releases an amount of heat (under a specific temperature). So the effect of the phase transition on entropy would be equal to: \begin{align} ...
1
vote
0answers
50 views

Is there a matching material interior for the Kerr solution of Einstein's equations?

Is there a matching material interior for the Kerr solution of Einstein's equations? I can only find informal and conflicting information about this. Some time ago, I've heard that it was expected to ...
5
votes
2answers
506 views

Why does adjoint representation matter in some field theories?

Recently I am reading a paper about monopoles. In several cases, it seems that writing fields in adjoint representation of the gauge group makes a difference. Once it leads to different group after ...
0
votes
1answer
73 views

Unit for expressing energy eigenvalue in infinite potential well problem

How are the energy eigenvalues expressed in a infinite potential well problem( Joules/eV)?
4
votes
1answer
308 views

Some doubts about photons

I am reading Berkeley Physics Course vol. 4 (Quantum Mechanics) , chapter 4 (photons). (1) Section 46: book says: consider a typical photon emitted by the source. It can be regarded as a a wave ...
3
votes
3answers
682 views

Angular Displacement

If something is rotating about a point and it covers a complete circle, should we take its angular displacement as 360 degree or 0? Please give link to some established material on this subject ...
0
votes
0answers
24 views

Calculating the stability/invertibility of energy maps by multivariate time series model

You have the following energy maps for 14 different structures so about 4-5 pixels for one unit. The color density represents energy. I am thinking that you can set multivariate time series models ...
2
votes
2answers
196 views

Does the pilot of a rocket ship experience an asymptotic approach to the speed of light?

A question has recently come up that goes beyond my knowledge of special relativity. Suppose a pilot has his foot on the gas pedal of a rocket ship and keeps it applied to achieve a constant ...
4
votes
1answer
201 views

Schrödinger equation for two particles in a 3D box?

This is not a homework question, just a question I have developed to get a better conceptual understanding of the results of the Schrödinger equation. If I had a 3D spherical container or radius R, ...
1
vote
1answer
917 views

Commutator of Momentum with a Position dependent function

I heard from my GSI that the commutator of momentum with a position dependent quantity is always $-i\hbar$ times the derivative of the position dependent quantity. Can someone point me towards a ...
3
votes
1answer
133 views

Classical dynamics with Schrodinger equation

What are some interesting classical systems for which the dynamics can be reduced to a many-body Schrodinger equation, at least in some useful regions of phase space, and in particular, with many ...
2
votes
2answers
383 views

Comparing effect of electric and magnetic dipoles on their fields

So at the end of one of my prof's lectures he gives us something to think about: Both electric and magnetic dipoles tend to line up with their respective fields. Materials made out of ...
4
votes
3answers
110 views

Possibility for contact lenses that enhance the vibrancy of color

Would it be possible to develop oculars that would enhance the vibrancy of color? I know there are many digital filters to improve vibrancy, but are there physical devices able to produce the same ...
0
votes
3answers
285 views

Creating a 2d magnet simulator [closed]

I need to create a "simple" magnet simulator, unfortunetely I have little to no physics knowledge. The best way to describe my idea is, imagine a hockey table. There's a disk and I need to throw it ...
1
vote
0answers
76 views

How to analyze this constraint question

Let $\gamma$ be a smooth curve in the plane, and introduce curvilinear coordinates $q_1,q_2$ on a neighborhood of $\gamma$; $q_1$ is the direction of $\gamma$ and $q_2$ is distance from the curve. ...
0
votes
3answers
257 views

How to derive the uncertainty relation for a system of arbitrary potential?

I've been trying to understand the derivation of the uncertainty principle for the harmonic oscillator as described here (see pages 100-101). What I don't understand is how the potential for the ...
-2
votes
1answer
68 views

Attraction of a Bullet due to Gravity in a Perfect Vaccum

I realise that this might be conventially very difficult to answer because there's no KG or Newtons in space, only particles. As far as I understand, every object creates a 'pull' due to the forces ...
5
votes
1answer
232 views

Peskin & Schroeder Chapter 3.1 EoM Lorentz Invariant under Lorentz Invariant Lagrangian

From Peskin & Schroeder QFT page 35: The Lagrangian formulation of field theory makes it especially easy to discuss Lorentz invariance. And equation of motion is automatically Lorentz ...
1
vote
0answers
48 views

Thermal exfoliation of graphite oxide

I have been reading up on the production methods of graphene, and one that I found interesting in particular was the thermal exfoliation of graphite oxide. From what I gather the basic idea is that ...
3
votes
0answers
141 views

Gauss-Bonnet term in Physics

Given a 4-dimensional compact manifold (torsion free), the Euler characteristic is defined as: $$E_4 ~=~ \int \epsilon_{abcd}R^{ab} \wedge R^{cd}$$ with $R^{ab}$ is the curvature 2-form. Perturb the ...
1
vote
2answers
124 views

Fermion field structure in non-abelian gauge theories

I am trying to understand the structure of the fermions in non-abelian gauge theories. Disclaimer: my question might be very trivial (I suspect the answer could simply be "a change of basis"), but I ...
3
votes
2answers
710 views

Why do people with bigger hands/wrists have bigger torque advantages in arm wrestling?

I have arm wrestled people with less strength than me who win simply because they have thicker wrists, or larger hands. It has nary to do with having better technique either, because their wrist size ...
2
votes
2answers
164 views

How is it possible to move something without completely lifting it?

For example, let's assume a chair here: It can be "slid" across the force if we use minimal upwards force, but not enough to actually "lift" the chair. Why should it move? Here's a better example: I ...
-1
votes
1answer
110 views

Was Joule's experiment able to show: thermal energy = $mgh$

Is my understanding of this experiment correct? There is the quantity $MC\delta \theta$ associated to the heat which I think is not an absolute value to be compared with $mgh$ since the $\delta ...
0
votes
0answers
60 views

What “time” is it for or on Voyager 1? If you could be “still” in the Universe who fast would time be? [duplicate]

I just sent this to JPL but am not putting all my eggs in one basket so thought I would try some other clever people. :-) I think about physics and space quite a lot but I'm not a maths genius so do ...
7
votes
2answers
302 views

Anti-matter as matter going backwards in time? (requesting further clarification upon a previous post)

I understand this question has already been asked here, however, I don't have enough reputation points to place a comment (I suppose that's the reason) on a specific answer to request a reference. A ...
1
vote
1answer
191 views

A few simple questions about Grassmann numbers: commutation relations and derivatives

I'm trying to learn about Grassmann numbers from the book "Condensed Matter Field Theory" by Altland and Simons, but I am currently encountering some difficulties. I have several smaller questions ...
2
votes
1answer
374 views

Understanding the time dilation calculation in Brian Cox's Doctor Who lecture

Background My son has just watched Brian Cox's fascinating "The Science of Doctor Who" lecture on space-time and was particularly intrigued by the part (at 22m:22s) where he said: Let us say that ...
0
votes
3answers
1k views

What is the use of this formula 1 Tesla = 1 Newton/Ampere/Meter?

What does Newtons/Ampere/Meter stand for? From this formula: 1 Tesla = 1 Newtons/Ampere/meter what can it be used for? To do what? Ampere/meter Is the same unit as a field's intensity H? Or what is ...
2
votes
3answers
161 views

Why are high voltage lines “high voltage?”

If I have two spheres of the same size and one sphere has a small amount of charge compared to the other that has a lot more charge, then clearly the sphere with the larger charge has a larger voltage ...
2
votes
0answers
137 views

Problem with (grad school) physics education? [closed]

(Just to anticipate, having looked at other closed threads about physics education, I don't think this question should be too opinion based or broad.) Since being in a lab now for a couple years, ...
7
votes
1answer
252 views

Does a pendulum necessarily emit gravitational waves?

A question about the behaviour of a pendulum in a frictionless vacuum recently made it back to the front page, and a few comments below John Rennie's excellent answer set me thinking about one ...
2
votes
3answers
234 views

The cooling curve of tin during solidification

I'm going to measure the freezing point of tin by recording the cooling curve. It sounds like a dull experiment because all I have to do is to heat up the tin, wait for it to cool, and the computer ...
2
votes
2answers
61 views

Difference between a central potential that is a point and one that is a sphere?

In quantum physics there is a special case known as a particle in a spherically symmetric potential. I have a problem which is similar to the case of a hydrogen atom in that there is one free ...
3
votes
2answers
137 views

Srednicki's book on QFT

I am reading Srednicki's book on QFT and there's a thing I don't quite see in chapter 6 (Path integrals in QM) equation (6.7) is ...
1
vote
1answer
63 views

How to calculate thrust ratios for an object with a non centered mass [closed]

I am trying to figure out a formula that, given an initial thrust value, will give me the thrust value that I need to apply to each thruster (red) to make the overall thrust be straight up with no ...
8
votes
4answers
399 views

Doesn't the use of a thermometer alter the temperature of the system?

If I place a mercury thermometer in hot water, heat energy will transfer from the water to the mercury inside the thermometer. Will this continue until thermal equilibrium is reached and thus the ...

15 30 50 per page