3
votes
1answer
60 views

Where would the dark matter particle fit inside a picture of the standard model?

While I am particularly fond of the Sterile Neutrino, I have not been able to find any example of a picture of the standard model arrangement of particles, with Dark Matter (and the higgs), inside a ...
0
votes
1answer
42 views

General Relativity - Four Velocity Derivative Question

I am trying to get my head around a small point used in a book I am reading about General Relativity. The book states that because $u_au^a = c^2$ it follows that $u_a \nabla_b u^a = 0 $ The first ...
0
votes
0answers
22 views

Help with inclined slope motion? [on hold]

I have this question (5ii) and I was wondering why this wouldn't work, why can't I solve for acceleration using $v^{2}-u^{2}/2s$=$a$ then solve for $t$? I obviously have to resolve and use $p=fv$ but ...
-2
votes
0answers
27 views

Is Twin Paradox solved in Special Relativity or General Relativity? [duplicate]

I'm getting pretty frustrated about finding the true solution to the Twin Paradox. If I open 10 relativity books, they all tell that they have the correct solution and the other books are wrong. So I ...
4
votes
1answer
23 views

Does the Advanced Photon Source use electrons or positrons?

Synchrotron light sources like the Advanced Photon Source (APS) (as well as SPring-8 and the ESRF) are typically mentioned as accelerating electrons up to the GeV range to produce extremely high ...
0
votes
1answer
31 views

How to derive path difference ($\Delta l=d\sin \theta$) for double-slit interference?

The Wikipedia page for the double-slit wave interference experiment states that the path difference between waves diffracting from the two slits is equal to: $$ \Delta l=d\sin \theta $$ where $d$ is ...
1
vote
3answers
135 views

What is the meaning of “ Ψ is not a measurable quantity in itself”?

I want to know that why the wavefunction Ψ as a complex quantity (i.e $A+iB$ form) in quantum mechanics and somewhere I have studied that Ψ is not a measurable quantity in itself that's why we ...
0
votes
1answer
42 views

How to determine which object in a special relativity physics problem has proper time?

I'm having some difficulty determining which object/location should have proper time applied to it in relativity physics problems. Example: If an electron travels at 40% the speed of light then ...
1
vote
1answer
36 views

Can a brane have infinite volume?

I'm asking this within the framework of brane theory. My intuition is that branes are objects with finite volume, but then how can they accomodate an Universe that is infinite in extent?
1
vote
2answers
38 views

Electric field due to a finite line charge [on hold]

I was wondering what would happen if we were to calculate electric field due to a finite line charge. Most books have this for an infinite line charge. In the given figure if I remove the portion of ...
2
votes
1answer
24 views

Polarization of light for a fast moving observer

For a fast moving observer the frequency of light becomes shifted due to the (relativistic) Doppler effect. But what about the polarization of the light? Could it be, that e.g. circular polarized ...
1
vote
1answer
77 views

When will the pringles can fall?

When I'm pushing a tall, cylindrical object stood on its end (like a Pringles can) I can push it near its bottom, and it will slide forwards, or push it near the top, and it will topple over. So, ...
3
votes
1answer
39 views

Why is energy in a system typically able to be described using quadratic expressions?

This might be more of an applied math question. Why is the energy of a system typically able to be described using quadratic expressions. Is there an underlying mechanic that drives this?
2
votes
0answers
27 views

Current carrying conductor with a loop at a distance [on hold]

In Fig, there are an infinitely long conductive wire and a circle conductive loop C with the radius r and the number of turns n. The distance L between the wire and the loop is much larger than r, ...
11
votes
6answers
2k views

Can you ever exert more downwards force than your weight?

So, because I'm a hardcore person, I risked all this afternoon by going out in the wind, the rain and the cold to construct a willow den. Yes, it seems a menial task, but it was actually quite ...
0
votes
0answers
26 views

Does the Meissner effect only effect magnetic fields?

I find this effect very interesting and was wondering what tests have been performed to check its effects on other fields? Also a side question related to this effect, can it trap a magnetic field. ...
0
votes
2answers
18 views

For a light of given frequency, what does the amount of refraction in a variable medium depends upon?

I want to know whether the amount of refraction of a given monochromatic light depends solely upon the density of the of the medium ( increase the density to increase the angle of refraction), or ...
0
votes
0answers
15 views

water pressure relationship to volume [on hold]

I have a one inch pipe 120 feet long and caped. I have a 60 pound input of pressure. I put a half inch pipe at the end and open it. What happens to the pressure in the one inch pipe? If I add another ...
0
votes
1answer
30 views

Is there serious research on superluminal travel? [on hold]

I was wondering if there are any serious attempts, or any ideas for loopholes in the current theories, that would enable us humans to travel with a speed greater than the speed of light?
1
vote
1answer
35 views

About shift operators

The question is this: Does $$L_+ L_- Y_{lm} $$ ,where $Y_{lm}$ is a spherical harmonic function, equals to zero. If so, why? The two operators above are defined as $$L_+ ={L_x + iL_y } $$ $$L_-={L_x ...
0
votes
2answers
44 views

Why do corpses come back to water surfaces after sinking at first?

I want to know that why do dead bodies or corpses come back to the water surface after being sunk at first by the use of stones or anything. For what I can understand, I think it's due to water ...
3
votes
1answer
29 views

Average force for repeated elastic collisions

I was asked to compute the average force exerted by a rigid spherical ball (mass m) on the floor over infinite time, in a situation where the ball is dropped vertically from a height (h) and makes ...
2
votes
0answers
23 views

Distribution forces

I've got two trees and between them is a rope. When someone about 100kg sits at the center of the rope, what are the forces on both parts of rope (to the left-hand side from the person and right-hand ...
2
votes
0answers
41 views

Newton's law of cooling for the heat equation boundary condition

Newton's law of cooling says the temperature of an object satisfies $$ \frac{dT}{dt} = -k(T(t) - T_0),\tag{1} $$ where $T_0$ is the surrounding temperature. See these HTML notes for example. Now if ...
0
votes
1answer
16 views

Why diamagnetic material is not repelled?

When an external magnetic field is applied to a diamagnetic materials, their atomic current loops will tend to align in such a way as to oppose the applied field. Diamagnetism is the residual magnetic ...
3
votes
1answer
58 views

Considering $\langle \underline{q} \mid \underline{p} \rangle=\frac{1}{(2\pi\hbar)^{n/2}}e^{i\underline{q}\cdot\underline{p}/\hbar}$ [duplicate]

I have been given the following complete systems of eigenvectors $$\mathbf{Q}\mid\mathbf{q} \rangle=\mathbf{q}\mid\mathbf{q} \rangle, \quad \mathbf{P}\mid\mathbf{p} \rangle=\mathbf{p}\mid\mathbf{p} ...
2
votes
1answer
49 views

Is there a time dilation between my left and right arms?

Is there a time dilation between my left and right arms when walking? due to special relativity I guess Thanks
4
votes
2answers
84 views

where is the logical hole in this reasoning? (special relativity)

I cannot see the problem in the following reasoning, so I'd be glad if you could help me out. The problem is defining a notion of "length" that is consistent with the constancy of the speed of light ...
0
votes
1answer
40 views

Second law of thermodynamics (in terms of entropy)

Is the second law of thermodynamics (in terms of entropy) for closed systems or isolated systems? I thought it must be valid for isolated systems, such as the Universe. But the book Fundamentals of ...
4
votes
1answer
37 views

Does the definition of compressibility depend on the frame of reference?

According to many authors, a fluid is defined to be incompressible if the material derivative of the density $\frac{D\rho}{Dt}$ is zero, that is to say, that in an frame of reference following the ...
1
vote
1answer
48 views

Where should five charges be placed inside a hollow sphere so as the system has the lowest potential energy? [duplicate]

I want to know the configuration where the system would be most stable.I only know basic Physics & Maths and cannot start solving the problem.I can understand it for 4 charges and 6 charges as a ...
0
votes
0answers
23 views

Charged particle inside a hole in a charged layer

The layer $-a\le x \le a$ is homogeneously charged with a electric charge density $\rho \gt 0$ and on the x-axis a thin hole is made. A particle with mass $m$ and charge $q \gt 0$ move on the ...
1
vote
1answer
16 views

When I put 2 electrodes into a electrical conductive solution, does the volume of the solution around the electrodes have biological effect?

Media these days give me a common sense that it is able to hurt someone if they step on a wet floor with a electric cord dipped in, several movies have this scene.However, I wonder if I set up an ...
0
votes
0answers
47 views

Where should five charges be placed inside a hollow sphere so as the system has the lowest potential energy? [on hold]

I want to know the configuration where the system would be most stable. But I cannot think of a way to start solving the problem. I've solved it for 4 charges and 6 charges and they have a symmetric ...
3
votes
0answers
53 views

Field states, particles, QFT

I'm trying to self-study QFT and write a presentation paper on neutrinos. Regarding the $\left\{ \nu_L, \nu_R, \bar{\nu}_L, \bar{\nu}_R \right\}$ set of neutrino states, what is the correct word to ...
1
vote
0answers
38 views

In Solution of the equation $\Box A_\sigma=0$. I find some mathematical difficulties [on hold]

The solution of the equation $$\Box A^\mu(x)=0$$ has the form $$A^\mu(x)=\int\frac{d^4k}{(2\pi)^4} e^{ik^\mu x_\mu}A^\mu(k)\delta(k^2).$$ Where we take $A^\mu(k)$ of the form $$A^\mu(k)=\sum ...
0
votes
1answer
25 views

Is it possible to make use of the gluon field's energy to use is applications?

As we know most of the mass of the proton comes from the energy caused due to the interactions of the quarks with the gluon fields (reference link of this statement ...
1
vote
1answer
40 views

What does 'zero-mean random noise with standard deviation equal to 1' mean?

Can anyone tell me what the meaning is of the phrase: "zero-mean random noise with standard deviation equal to 1"? Also, I want to know why not except zero-mean random noise and standard deviation ...
11
votes
1answer
168 views

Dispensing with the “a priori equal probability” postulate

I find the "a priori equal probability postulate" in statistical mechanics terribly frustrating. I look at two different states of a system, and they look very different. The particles are moving in ...
0
votes
0answers
22 views

Does relativity in any way “disprove” Newton? [duplicate]

I was reading a science magazine and it claimed that Einstein's theory of relativity disproves all of Newtonian physics. I was highly skeptical because all we have been learning at school is Newtonian ...
-5
votes
0answers
16 views

frequencies that affect newtonian and non newtonian liquids [on hold]

I have a science fair coming up and i need to know which sound frequences affect liquids, both newtonian and non newtownian. i also need to know the science and formulae behind it. Your answers will ...
2
votes
1answer
38 views

Does it mean the molecules of all matter above absolute zero temperature are moving? [duplicate]

According to my knowledge, heat is the energy that is stored in form of kinetic energy of molecules in Brownian motion. However, in a macroscopic view, a rigid body seem to be "stable" but still store ...
1
vote
0answers
51 views

Deriving effective model without integrating out degrees of freedom in path integral formalism?

In path integral formalism of quantum field theory (particle physics or condensed matter), one can in principle integrate out part of the degrees of freedom so as to attain an effective model ...
1
vote
1answer
53 views

Do Waves have mass? [duplicate]

Do any form of electromagnetic waves like visible light have mass? It is known that all electromagnetic waves have energy. According to Einstein's $$ E^2=p^2c^2 + m^2c^4 $$ formula, the energy of a ...
0
votes
1answer
33 views

Working out length of taut rope orbiting the earth remaining straight and radially directed [on hold]

A taut rope is orbiting the earth with angular velocity $a$. It remains straight and radially directed. If the midpoint is located at radius $r$, find the length of the rope. I can't even imagine ...
0
votes
0answers
33 views

How to calculate the potential energy of a magnetic dipole (with zero torque)

In the following problem, I would like to know how they arrived at their solution for finding the potential energy of a magnetic dipole (boxed in red). I understand I probably have to use the ...
-3
votes
0answers
21 views

Electric field calculation and its graph vs x [on hold]

Electric field along the line passing through two point charges, A point charge $Q_1= +3 \mu C$ is placed at the origin and a point charge $Q_2= -7\mu C $is placed at $x=0.4 m$ on the $x$-axis of a ...
0
votes
0answers
5 views

What is the exact definition of Magneto-optical Polar Kerr angle?

As stated in the title. I would like to know the exact definition of the Magneto-optical Polar Kerr angle. Whether it is just the rotation angle of the polarized light or it is something else?
0
votes
1answer
45 views

How can we define a frame of reference in general relativity?

I have started reading general relativity. (A First Course in General Relativity, Bernard Schutz). I am finding very hard to understand a frame of reference. When I was reading special relativity ...
0
votes
0answers
22 views

Entanglement and the boundaries of fiction

If entanglement is just a correlation from when the particles were in proximity, and there is no causality between the two, can the state of one particle be changed after being measured, and that ...

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