-2
votes
2answers
178 views

Are massive gravitons as the dark matter fluid more correct than the notion of WIMPs?

Accepted at APS Physical Review D: Massive gravitons as dark matter and gravitational waves Precursor: Bigravitons as dark matter and gravitational waves The massive graviton is a viable ...
1
vote
2answers
70 views

Equal transit time fallacy and Newton's laws of motion

I've seen the equal transit time theory being used to explain aerodynamic lift [basis is Bernoulli's principle] several times. However recently I've been told that there is NO physical compulsion for ...
1
vote
2answers
30 views

What is the difference between crystals and solid? [on hold]

In condensed matter physics, what are the differences between crystals.
0
votes
1answer
24 views

Weight Detection Under Concrete/Asphalt

Consider that a weight sensor was embedded in a road. Would cars that drive over it trigger the sensor? I was thinking it'd look something like this (if we ignored the downward force that the ...
0
votes
0answers
21 views

What is the difference between the Lorentz force in a cloud chamber and the repelling/attracting force between magnets?

In a cloud chamber charged particles are bend by a magnetic field where the Lorentz force is causing the bending. But when a ferromagnetic material is attracted or repelled by a magnet it is more or ...
1
vote
1answer
38 views

What is the angular divergence of sun-rays?

I just want to find a number and I could not. Does anyone has it or can calculate it easily? Just in geometric optics, without diffraction, atmospheric effects and etc. Update: I think for me will be ...
0
votes
1answer
33 views

Group Velocity of guassian packet equals time derivative of mean position?

If I look at a gaussian wave package, and then interpret (in the usual Quantum-Mechanics Way) its square value as the propability density, then I can calculate a mean value for the position: $$ x_{...
5
votes
2answers
126 views

What happen if Hawking radiation is not found?

I'm not a physicist but reading from a few popsci books. I read that Hawking has equations that explain Hawking Radiation precisely, right? Is this equation a proof that the radiation is real or we ...
2
votes
0answers
19 views

A cheap experiment to verify that a monitors intensity response is not linear

For the past year or so i have had to answer different questions on how the intensity response of a monitor behaves, nearly every week. Many of you probably know that the monitor intensity response to ...
5
votes
2answers
94 views

What is the difference between active and passive transformations in Quantum Mechanics?

I am trying to understand what each transformation means and what their differences are but many books that don't state which transformation they are referring to make it a bit confusing to understand ...
0
votes
0answers
25 views

Strain calculation for complex sampe

When performing tensile tests samples must have constant crossection alongside the axis. Then two marks are made and we can define engineering stress $\sigma=\frac{F}{A_0}$ and engineering strain $\...
0
votes
0answers
8 views

What is the difference between luminosity of a star and absolute luminosity

The equations for the habitable zone of a star call for the "absolute luminosity." Is this different from the luminosity value calculated by AσT^4 (Stefan-Boltzmann ...
0
votes
0answers
16 views

Minimal size of an optical lense

Is the minimal size of an optical lense (diameter, width and the curvature) limited by the wavelength of the incident light?
0
votes
1answer
24 views

Is it possible that an object orbits another object without ever tangenting or crossing its equator?

Imagine Object 1 beeing the earth and object 2 beeing the moon having a orbit around earth, like the yellow line is demonstrating. Could something like this anyhow naturaly as standalone occur? I'd ...
0
votes
1answer
14 views

What does “ambient atmosphere of 20 mu” mean?

I've read through a publication from 1960 which discusses oxygen annealing. It shows a the following graph. What does the "ambient atmosphere of XY mu" mean? What is a mu atmosphere? taken from: ...
6
votes
4answers
133 views

How can I tell that a Lagrangian has an $SU(2)\times SU(2)$ symmetry?

this is a very basic question and it probably has a very simple answer. I was reading through some handouts when I came over something that I did not understand. One considered the simple Lagrangian ...
1
vote
2answers
57 views

Is the Pauli exclusion principle also involved in free electrons?

Imagine I want to make a laser of electrons like a laser of light. Is that possible, or does the Pauli exclusion principle prohibit that?
1
vote
0answers
7 views

Rusting of induction hardened portion when the non hardened portion is chrome plated [on hold]

When a ferritic steel component that has a portion of it induction hardened and quenched in oil is chrome plated over the non hardened portion, I see rust formation after some time on the induction ...
1
vote
0answers
11 views

Proof from Calculus 1 [migrated]

Last days, from going into a website of the university of Pisa, I found an exercise given in the previous exams, in 1999. The problem was like: Given a continuous function f in R, and which ...
-1
votes
0answers
15 views

How can I find the acceleration of a spring when the spring is elongated of $x = y$ $meters$? [on hold]

Good morning to everyone! I have a problem that I don't know how to solve: I have a block on a plain, I know its mass I know the angle of inclination of the plane, and the coefficient of friction. It ...
0
votes
1answer
17 views

ultimate tensile strength for elastomers

I'm doing experiments with an elastomer and I'd like to know how I should determine tensile strength in practice. Is this the point where I begin to observe tears in the elastomer or where the ...
3
votes
1answer
42 views

Is there a theorem which specifies the state (with energy $E$) with maximum entanglement?

Does there exist any theorem in quantum information which states that the particular state with energy $E$ is the state with maximum entanglement (or discord) among all possible state with the same ...
1
vote
0answers
36 views

Origin of the magnetic field of Earth [duplicate]

The Dynamo theory gives a good explanation of the magnetic field of the Earth: the Coriolis force focus inner currents into current spirals generating magnetic(s) field(s). What I'm trying to ...
1
vote
0answers
27 views

Light passing through two sets of double-slits in tandem

Has anyone ever set up a double double-slit experiment - one in which a second double-slit is inserted at one of the bright spots of the interference pattern produced by the first one? The intensity ...
-6
votes
0answers
71 views

If mass rotates at varying speed, will the whole system be pulled in the direction of the strongest centrifugal force? [on hold]

And, what are the implications in terms of Newtonian law of action and reaction, as well as conservation of momentum and conservation of energy? Practical example: https://www.youtube.com/watch?v=-...
0
votes
0answers
7 views

What is the ray diagram for Schuster's focussing?

I haven't been able to find it online. Our course book also doesn't provide a ray diagram for this particular phenomenon. I feel like it's difficult to understand the process without the ray diagram.
1
vote
0answers
13 views

What is signifcance of density of the universe if it changes?

So theories of expansion of the universe (before dark matter and energy) said that the ultimate fate of the universe is based on the density of the universe and this being compared to the critical ...
-2
votes
0answers
7 views

what is the benefit from finding relative speed/ velocity of two moving objects (cars)in the same direction? [on hold]

I just want to know why do we find relative speed/ velocity of two moving objects (cars)in the same direction? I mean how will this give me benefits.
7
votes
3answers
2k views

Is it possible to have a photon with -1 spin?

Wikipedia states that a photon has a spin of value 1. What I want to know is this: are there two possible spins for photons, i.e. +1 and -1 (like electrons, which can have +1/2 or -1/2)? If the spin ...
0
votes
0answers
18 views

Rotating rod viewed in standard frames S and S' [on hold]

I am doing a problem in relativity book by Rindler and for one question I do not have the answer. It states that in the rest frame a rod centred on the origin rotates uniformly (frame S'). What will ...
0
votes
0answers
18 views

the lagrangian of the axial vector field [on hold]

What is the Lagrangian of a axial vector field? How can I find it? I want to describe a model which is made by standard model with extended by an axial vector and a Dirac fermion!
0
votes
0answers
15 views

Charge distribution in a conductor [on hold]

If some charge is given to a hollow conducting hemisphere of some thickness,where will be the charge present in that hollow conducting hemisphere?
-1
votes
0answers
25 views

Laws of motion in use [on hold]

Do the laws of motion apply to photons and other particles like mesons,gluons etc.Can you please specify the reason if yes and no
0
votes
0answers
14 views

Can DC electric field be regarded as a quantum harmonic oscillator? [duplicate]

The essence of quantum theory of the radiation field is the association of a quantum harmonic oscillator with each mode of the field. However, in the case of DC electric field, can we describe DC ...
10
votes
1answer
337 views

In quantum mechanics, how exactly do we associate Hermitian operators to classical observables? [duplicate]

In a first course on quantum mechanics, everybody learns some version of the following statement: Postulate: To every classical observable $A$ of a physical system, there corresponds a Hermitian ...
1
vote
0answers
21 views

Is the reduction of tensor loop integrals to scalar integrals using Passarino Veltman Functions, theory dependent?

While reducing the tensor integrals to scalar integrals all that we use are Lorentz covariance and the physical interpretation of the result. Thus I think that the Pa Ve Reduction of Tensor integrals ...
-2
votes
0answers
32 views

Contradictory kinematics formula [duplicate]

The displacement of a particle in the $t$th second of its motion is given by: $$ S(t)=u + \frac{a}{2}\left(2t-1\right) $$ where $u$ is the initial velocity, $a$ is the acceleration and $s$ is the ...
0
votes
0answers
37 views

Publishing in American Journal of Physics [on hold]

Can I publish my article in American Journal of Physics, if I am not a part of any educational/research institute nor a part of private industry? Also I do not have any referee. Do I need to pay to Am....
2
votes
3answers
59 views

Second Law of Dynamics and Pulleys

The system in the figure is initially at rest . If the system starts to move , evaluate the acceleration of the block $A$. Mass of the block $A$ is $m_A = 60\;\mathrm{kg}$ ; mass of blocks $B$ and $C$ ...
-5
votes
1answer
44 views

Newton's 1st law [on hold]

If all of a sudden the gravitational force and gravity disappears then the planets would still continue to rotate and revolve ? Give reason
0
votes
1answer
17 views

Selection rules for electric quadrupole radiation

The selection rules for electric quadrupole radiation in a Hydrogen-like atom are: $$ \begin{aligned} \Delta l &= 0,\pm2 \hspace{1cm}(l=0\leftrightarrow l'=0 \textrm{ is forbidden}) \\ \Delta m &...
1
vote
1answer
32 views

What is the meaning of a negative Galactic longitude?

What is the meaning of negative longitude in Galactic coordinate system, for instance in this article? Does the longitude $-65^\circ$ equal $295^\circ$?
3
votes
1answer
29 views

Can circular polarized light be cancelled?

I can cancel the light output from an LED screen by placing a linear polarizer at 90 degrees from the linear polarizer built into the LED display. OLED displays use circular polarizers instead of ...
0
votes
1answer
17 views

Reducing coefficient of friction by vibrations?

Very simply put, if one places a block of some material on a level surface and pushes it horizontally, a certain coefficient of friction is measured. If one tightly couples an oscillator of some sort ...
1
vote
1answer
65 views

Does the use of $\gamma=\left(1-v^{2}/c^{2}\right)^{-1/2}$ automatically assume a (+ - - - ) metric? [on hold]

In Special Relativity, does the use of $\gamma=\left(1-v^{2}/c^{2}\right)^{-1/2}$ automatically assume a (+ - - - ) metric convention? For introductory textbooks, the Lorentz factor is is always ...
0
votes
1answer
50 views

Before Dark Energy was discovered

I'm really confused on this topic. Pardon my French if my questions seem really stupid. Before Dark Energy was discovered in 1998 did scientists know that the cosmological constant calculated, I ...
2
votes
0answers
15 views

Does the vacuum have a zero Seebeck coefficient?

I was considering how at very high energies (e.g the Schwinger Limit) the vacuum starts having properties we would normally associate with "materials", such as non-linear polarizibility. The Seebeck ...
-6
votes
0answers
23 views

Answer true or false? [on hold]

True or false? Q: The magnitude of displacement is equal to distance covered in a given interval of time if the particle ___. A: moves with constant acceleration
0
votes
0answers
50 views

Why do we add gamma to derive the Lorentz transformation?

I was trying to derive the Lorentz transformation with the following... $$\frac{t'}{t} = \frac{c-v}{c},\qquad \frac{t}{t'} = \frac{c+v}{c}$$ After adding gamma $$\frac{t'}{t} = \gamma\frac{c-v}{c},\...
-1
votes
1answer
23 views

Curious about headphones [on hold]

So I'm trying to learn more about headphones. I have a small piston that is in a small sealed volume (the earcup, say it is $25\, cc$). And there is a front volume between the piston and the ear (...

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