0
votes
1answer
65 views

Does car colour affect car temperature? [duplicate]

My family will buy a car, so to minimise the car's air conditioning and heating (and thus fuel) costs, how should we choose a car exterior's colour and the interior's colour and material (eg fabric ...
0
votes
2answers
44 views

At what point do researchers in physics make the leap from wild theoretical ideas to physical experiments? [on hold]

Dark Matter, on the surface, appears to be a wild idea... Some invisible thing that we can't see that controls the movement of most of the universe. Yet, we are searching for it. Why? What evidence ...
0
votes
0answers
15 views

Real representations of chiral fields

Why we can´t have real representations of chiral fields, i.e. why does a multiplet of chiral field (Weyl spinors) under a real representaiton of a Lie Group transforms as a "vector". It is easy to see ...
2
votes
2answers
68 views

Birds and cables: how is the potential difference between two diff. cables established?

The common explanation of why birds don't receive a shock when standing on high tension cables is that there needs to be a considerable potential difference between both of his feet for him to receive ...
2
votes
2answers
50 views

Why can't dark matter be baryonic?

Here's what I know about dark matter: Astrophysicists realized the movements of galaxies and other astronomical bodies cannot be explained by the gravitational effects of matter known to be there, so ...
4
votes
3answers
76 views

Is gravitational Chern-Simons action “topological” or not?

Here are the 2+1D gravitational Chern-Simons action of the connection $\Gamma$ or spin-connection: $$ S=\int\Gamma\wedge\mathrm{d}\Gamma + \frac{2}{3}\Gamma\wedge\Gamma\wedge\Gamma \tag{a} $$ $$ ...
2
votes
0answers
18 views

Thermal Conduction with multilayered system

Sorry this question probably has a really simple answer but I have been looking and I can't figure out how to solve this problem. I know that the equation for power loss through conduction is ...
0
votes
1answer
94 views

Schroedinger Equation and Special Relativity

From what I understand, the Schroedinger equation describes how the wave function of a quantum system evolves in space over a given time (I am referring to a relativistic version of the Schroedinger ...
1
vote
1answer
59 views

Research papers readable by first years? [on hold]

This coming Spring I'll be running a Mechanics I lab for freshman (as a teaching assistant) and I'll have some say as to the way I do it. So I was thinking it would be nice if I could find some ...
1
vote
0answers
52 views

Alternate theories of space and time [on hold]

Do mainstream theories in physics make implicit assumptions about the nature of space and time? In particular, are there any theories which implicitly assume that space and time are continuous, or is ...
3
votes
1answer
68 views

Detailed balance condition for coupled Langevin equation

Suppose $a$ and $m$ are real variables and they satisfy the following two coupled Langevin equations: $$ \dot{a}=F_a(a,m)+\eta_a(t);\quad\dot{m}=F_m(a,m)+\eta_m(t); $$ where $\eta_a$ and $\eta_m$ are ...
-5
votes
0answers
56 views

Energy manipulation [on hold]

Haha, I don't want to offend anybody, but I want to make a superhero that can control all forms of energy. From what I've heard you can do a lot like, manipulate time and space, open blackholes, ...
-1
votes
1answer
33 views

Center of mass finding question [on hold]

Find the center of mass the rod in the figure if λ (the mass per unit lenght) varies with $x$ according to $\lambda=dm/dx=\beta x^2$, where $\beta$ is a constant. Sorry for quality of picture. I am ...
5
votes
0answers
84 views

Is there a textbook which covers QM via Geometric Algebra (GA)?

There is at least one good book on classical mechanics using Geometric Algebra (GA): New Foundations in Classical Mechanics by David Hestenes. Likewise there is at least one good book on classical ...
0
votes
1answer
101 views

Confusion with anti-symmetric tensors!

I want to prove the following fact for two antisymmetric tensors: $$ 2G^{+\rho (\mu} H_{\,\,\, \rho}^{+\nu)} = -\frac{1}{4}\eta^{\mu \nu} G^{+\rho \sigma}H_{\rho \sigma}^{+}. $$ When I try to do it I ...
0
votes
0answers
49 views

Heisenberg picture with creation annihilation operators

In the Schrodinger picture, states are time dependent and operators time-independent. So expected values look like: $\langle s_1,t|\hat{A}|s_1,t\rangle$. If we go over to the Heisenberg picture the ...
1
vote
0answers
26 views

Mechanism/derivation of Rayleigh scattering

I have a question that might just show my lack of understanding of the border/interaction of classical field theory and quantum effects (or might have a much more mundane answer). In a basic course ...
0
votes
0answers
44 views

How fast would a 60 km diameter moon ring rotate to simulate 1 G? [on hold]

After seeing this answer regarding increasing mass for greater weight on the moon, my eyes caught the first comment about centrifuges in science fiction. Naturally, the thought of putting Elysium on ...
0
votes
1answer
46 views

Resolving power of ultra-telescopes

Assuming we could create and orbit optical telescopes of arbitrary size, perhaps starting with (say) inflatables or active membrane of 100m diameter what kind of resolution in imaging extra-solar ...
0
votes
0answers
11 views

Using couple channel plus imaginary potential as against only imaginary potential in nuclear reactions

In some situations coupled channel calculation incorporating inelastic scattering and imaginary potential produces results comparable to experiments for elastic scattering rather than using an ...
2
votes
0answers
50 views

Quantum fluctuation

According to the quantum fluctuation concept, a particle and its corresponding antiparticle appear out of nothing only to annihilate and emit some energy in the form of electromagnetic waves. Does ...
1
vote
3answers
127 views

Non-locality in non-relativistic Quantum Mechanic

I guess the following obvious question is answered by any flavor of relativistic Quantum Mechanics, but I just wanted to check whether I understand correctly: Is it correct that nonrelativistic QM ...
1
vote
1answer
57 views

Symplectic notation proof?

Hello I am trying to work through a little proof of the symplectic condition for Hamilton's equations for a classical mechanics course. I am trying to understand the meaning of the relation ...
0
votes
1answer
32 views

Avalance diode -looking symbols with two triangles in the case of backpressure pump? [on hold]

I cannot understand the symbols where you have some q terms, some arrows and white triangles. It is related to managed pressure drilling (MPD) of the system where the system is different to ...
0
votes
1answer
14 views

If we rub glass particles with paper , will there be any charge induction in glass particles?

If we rub glass particles with paper , will there be any charge induction in glass particles ? I know if you rub with silk they do get charged, but i want to know specifically for glass and paper.
1
vote
0answers
13 views

How much will a round tube deflect under load? [on hold]

I'm trying to determine the materials I need to complete a hobby project, and I'm having trouble estimating how much flex a given steel tube would have under different configurations/loads. My setup ...
1
vote
0answers
15 views

Why is responsivity quoted as a figure of merit?

Lately I have been investigating the physics literature on proposed photosensitive electronic devices made of graphene. Often I see responsivity values quoted as if they suppossed to impress, and ...
0
votes
0answers
13 views

why the illumination in fluorescence microscope is cylinder shape?

I know that in fluorescence microscope, because the filament of the lamp is kind of cylinder shape, so in the Kohler Illumination setup, it has a image plane of the filament at the rear focal plan of ...
2
votes
2answers
97 views
+50

How did the operators come about?

This relates a little bit to my previous question (Experimentally, what categorizes a measurement as corresponding to a certain observable?), but it's different in a way and more historical. One of ...
13
votes
1answer
981 views

A Christmas Story question!

since the Christmas season is here, I would like to ask a question about the movie, "A Christmas Story." In one of the subplots of the movie, Ralphie's friends were betting each other that their ...
0
votes
0answers
3 views

how to completely remove the charge from the glass bubble particles?

Do you have any idea on how to completely remove the charge from the glass bubble particles (25-32 micrometer diameter)? Thanks
0
votes
0answers
8 views

maximum dislacement on dumping sistem with FDM [on hold]

A precision grinding machine is supported on an isolator that has a stiffness of 1 MN/m and a viscous damping constant of 1 kNs/m. The floor on which the machine is mounted is subjected to a harmonic ...
0
votes
0answers
7 views

High photon flux for ultrashort photons?

What is currently the highest photon flux one can achieve for single photons with a coherence length of femtoseconds? Does some know roughly know the order of magnitude? Unfortunately I was not very ...
1
vote
1answer
31 views

Parallel Universe Moving Backwards in time [duplicate]

We know that different parallel universes- if they truly exist - are governed by different sets of laws. But, Could there be a parallel universe that is moving back in time (?) - in different ...
1
vote
0answers
14 views

Nitrogen generator maximum flow check

We have a N2 PSA unit with following specs Now I have done some calculations as shown in the image. Assuming 0.8% of the air is (N2+inerts) rest being O2 can someone tell me that how 160CFM air ...
2
votes
1answer
68 views

Relativistic Kill Vehicle

What would happen if a significantly supra-molecular object (say ranking from grams to low kilotons) would be accelerated to relativistic speeds (>.10 c) such that its worldline would intersect with a ...
2
votes
0answers
30 views

What does “downshear” mean?

I occasionally read descriptions such as "downshear of the vortex" in meteorological publications. What does this mean?
0
votes
1answer
32 views

Origin of band Gap

I know that in the Kronig Penney model there are values of the energy $E$ for which solutions to the Schrodinger equation don't exist. I understand that these forbidden values of $E$ form the band ...
3
votes
1answer
88 views

Can LIGO measure anything?

LIGO, Laser Interferometer Gravitational-Wave Observatory, is a large-scale physics experiment aiming to directly detect gravitational waves. The device measures the phase shift laser beams. If I ...
0
votes
0answers
21 views

Connected diagrams in Sine-Gordon action

I consider a bosonic action of the type $$\int dx d\tau\left( \underbrace{a(\nabla\theta)^2+b(\nabla\phi)^2}_{free} +\underbrace{c\cos{4\phi}}_{interaction}\right),$$ and want to treat the cosine term ...
0
votes
0answers
56 views

Understanding the physical applications of the Laplacian: Finding the heat-equation using the continuity equation [on hold]

I know the following: $$q=\rho c T$$ Where $q$ is heat per unit of volume, $\rho$ is the density, $c$ is the specific heat capacity and $T$ is the temperature. The flow of heat is given by: $$\vec ...
-1
votes
0answers
31 views

What are the most likely technology advancements that will result from NASA manned missions to asteroids & Mars? [on hold]

The Apollo missions required development of various devices that are now widely used, such as CAT scanners, microchips & integrated circuits etc. (more here) Do we know what are the main problems ...
0
votes
0answers
16 views

Ohmic contacts in a diode (metal-semiconductor junction) - contact difference of potential $V_0$ - how to compute

I'm reading "Microelectronics" by Millman, Grabel. Premise: The book developed, for a pn step-graded junction, the contact potential as $$ V_0 = V_T \text{ln} \frac{p_{p0}}{p_{n0}} = - V_T ...
-1
votes
1answer
32 views

Ways to measure the focal length of a convex lens with only natural sun light [on hold]

What are the common ways to measure the focal length of a convex lens with only natural sun light?
-2
votes
0answers
34 views

Measuring audio signals with a digital volt-meter [on hold]

Is a digital volt-meter suited for measuring audio signals, I know audio signals are measured in frequencies, is it possible/ideal to use a digital vm or something else will be better ?
0
votes
2answers
41 views

Difference between energy levels and bands of energy

As per the notes of my Solid state physics, band gap arises when the two atoms come close to each other so that their discrete energy levels split and become continuous which gives rise to bands of ...
0
votes
2answers
87 views

How do I calculate the most probable orbital an electron is in?

If I saw a snapshot in time of an electron near a proton (Hydrogen), then the electron can be in any orbital as long as it doesn't lie on a node of the wave function. So how would I determine which ...
0
votes
0answers
16 views

Loud, low-frequency “booming” sound in car [duplicate]

I drive a Scion XD, and I've noticed that whenever I drive at about 40mi/hr or so with just the back windows rolled down, I get a loud "booming" effect at roughly 10Hz. What causes this? I assume it ...
-2
votes
0answers
26 views

Block slides down smooth hemisphere: WHEN will it leave surface? [on hold]

A block is at rest at the top of a frictionless hemisphere of radius r. It is slightly disturbed and starts sliding down. WHEN will it leave the surface of the hemisphere?
0
votes
1answer
123 views

Why should we believe in clock hypothesis?

It is often assumed in special relativity that the rate of a clock in a non inertial frame does not depend on the proper acceleration of the observer. The point is, Rindler's observer shows us that ...

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