0
votes
0answers
30 views

At what velocity does space no longer equal a vacuum? [on hold]

In Dr. Alistair Reynolds's book (Revelation Space), he mentions that space only equals a vacuum at low speeds. At which velocities would space no longer count as an almost vacuum?
-2
votes
0answers
18 views

Leptons slide between quarks? [on hold]

I wonder if one of particles (maybe quarks?) are constructors of highways in 3d field for others floating around re/distributing energy by some (leptons?), restricted to laws set by (bosons?). If ...
-1
votes
0answers
42 views

No length contraction!

Suppose a person standing on a platform were to observe and measure the length of a train passing by. Instead of the usual approach involving a clock and knowing the speed of the train, the person ...
0
votes
0answers
15 views

Role of the crystallographic point group on properties of tensorial elasticity

If a space point group for a crystal is known, does this automatically define the elastic tensor symmetry of the material? What further implications can be found? The crystallographic subgroups: ...
3
votes
1answer
36 views

Fruit flies in a bell jar [duplicate]

You place a bell jar on a scale and the scale registers x grams. You then trap y grams of flying, non-landing fruit-flies in the bell jar. What does the scale register? x grams? x+y grams? Something ...
0
votes
1answer
17 views

Latent heat of solidification

What is the heat release mechanism involved in solidification from liquid phase? Is the energy transferred to nucleation centres?
1
vote
1answer
23 views

Evaporation of water at room temperature

Could anybody refer me to some literature (textbooks or research, although preferably textbooks!) dedicated to explaining quantitatively the phenomenon of evaporation of fluids? I understand that it's ...
1
vote
1answer
39 views

Hooks Law and acceleration [on hold]

A 435 gram sharpened piece of iron rebar into a spring loaded device. It takes a force of 355 Newtons to compress the spring by 27.5 cm. With what speed does the rebar shoot out of the device? ...
-8
votes
0answers
30 views

What is the speed of times arrow [on hold]

If the maximum speed of time in a vacuum is C you would have included time in relativity theory and have a definition of space time, Or the mass-time equivalence. A thought experiment.
0
votes
0answers
12 views

How non-invasive blood glucose concentration measurement work? [migrated]

Diabetes patients need to conduct the “fingerstick” a few times a day. One of the mechanisms of "fingerstick" is to take small amount of blood sample and put it onto a test strip. The enzyme on the ...
0
votes
1answer
51 views

Do we exist in multiple dimensions?

I have heard that there are 12 spacial dimensions. Does this mean that this many are possible,or that 12 dimensions actually exist? If the ladder, then do the same things that exist in 3 dimensions ...
0
votes
3answers
43 views

Determine which circuits are parallel and which are in series

I need to find the Equivalent Resistance across A and B. The problem is, I don't know which one's are in series and which ones are in parallel. How do I identify which ones are parallel or series?
2
votes
4answers
37 views

Sound diffraction through a single slit

When sound waves diffract through a single slit, do they produce an interference pattern which is mathematically identical to that of light waves in the corresponding experiment?
0
votes
1answer
39 views

Two Particle System with Identical Particles

I'm studying for an exam in quantum mechanics and tried to calculate the ground state and the first two excited states of two identical bosons (spin 0) in an infinite one dimensional potential well. ...
1
vote
1answer
35 views

Pressure and variation in pressure due to depth

In my class, we were shown the following problem: Using the equation $P_1$ = $P_0$ + $\displaystyle\rho$gh, where $P_1$ is the pressure at Superman's mouth and $P_0$ is the pressure at the surface ...
-1
votes
0answers
15 views

Uniform motion - need help with this problem [on hold]

Body A is moving towards body B (which is moving to A) with speeds v1 (for A) and v2 (for B) on the road s.Body B starts moving after time Δt compared to the body A (so t2 = t1 + Δt).I want to know ...
-4
votes
0answers
17 views

Law of conservation of linear momentum is a consequence of Newton's forst law substantiate [on hold]

Law of conservation of linear momentum is a consequence of Newton's first law substantiate.
0
votes
2answers
140 views

If Earth starts moving when attracted by an object, where does the energy come from?

Suppose a body(very big but not bigger than Earth) moves against gravitational force of Earth. The force will do negative work on the body decreasing its kinetic energy. The decreasing energy is ...
15
votes
2answers
178 views

Topology of phase space

Context: From Liouville's integrability theorem we know that: If a system with $n$ degrees of freedom exhibits at least $n$ globally defined integrals of motion (i.e. first integrals), where all ...
1
vote
1answer
51 views

What wilI I observe when travelling at almost the speed of light? [duplicate]

If I and a group of friends are travelling at or just below the speed of light - can I see myself, can I see them, or they me? Would we see anything at all?
3
votes
0answers
62 views

Difference in “momentum” names in Lagrangian mechanics

In the context of Lagrangian formulation of classical mechanics, the following names keep occurring in most textbooks, which confuse me a lot, are they different in any way? Momentum Generalized ...
1
vote
3answers
89 views

Variational Theorem proof

I have been trying to prove variational theorem in quantum mechanics for a couple of days but I can't understand the logic behind certain steps. Here is what I have so far: \begin{equation} ...
1
vote
0answers
57 views

Metric with 5D signature: +---+

From a paper that a friend sent to me (on inflation theory which I am still in learner mode) a 5D signature +---+ was specified with the 5th dimension being a velocity dimension. I didn't know that ...
0
votes
0answers
14 views

(Optical) Coherent states being all orders coherent

I recently read that coherent states $|{\alpha}\rangle = e^{-|\alpha|^2/2} \sum_{n=0}^\infty{\frac{\alpha^n}{\sqrt{n!}}|{n}\rangle }$ are all orders coherent, according to the definitions given on ...
1
vote
0answers
16 views

How to calculate the $g$ degeneracy factor for alkali metals and their singly ionized species?

The Saha ionization equation is $$\frac{n(X_{i+1})}{n(X_{i})} = \frac{(2\pi m k T)^{1.5}}{n_e h^3}\frac{2g_{i+1}}{g_{i}}e^{-\chi/kT}$$ where $\chi$ is the energy difference between the two ...
2
votes
3answers
84 views

Index notation with Navier-Stokes equations

This is an index-notation question rather then the NS one: For incompressible flow and Newtonian fluid, the continuity equation is denoted with: $$\frac{\partial u_i}{\partial x_i} = 0, $$ which ...
1
vote
0answers
21 views

Uncharged Gluon Representation

I'm currently learning for an exam and in an old exam the question was posed: If Gluons were uncharged, under which representation would they transform? The ...
1
vote
2answers
42 views

For a massless pulley moving upwards with acceleration, is the upward force equal to the downward force?

Imagine a massless and frictionless pulley with two weights hanging either side of the pulley by a massless string. Like this except not attached to a ceiling Rather than being fixed to a ceiling, ...
0
votes
2answers
39 views

Direction of pressure in fluids

ok so my friend told me that in a container, the pressure exerted by the walls on the liquid in the container act in the upward direction.Is he correct ? so what I am imagining is a cylindrical ...
2
votes
2answers
44 views

Why aren't classical phase space distribution functions always delta functions?

The phase space distribution function (or phase space density) is supposed to be the probability density of finding a particle around a given phase space point. But, classically, through Hamilton's ...
0
votes
1answer
32 views

Recent important observations on dark matter [on hold]

I would love some suggestions about my undergraduate research, thought it may be improper to ask here. I apology if I break the group rules. My undergraduate research topic is dark matter. My plan ...
0
votes
0answers
17 views

Semiconductor band diagram with a doping gradient

What does the Energy band diagram in a semiconductor look like if we introduced a doping gradient? What would it look like if after we added the doping gradient we introduced an electric field? I ...
0
votes
0answers
28 views

How would the transactional interpretation “bootstrap”

I have an interest in quantum physics and have been trying to educate myself here, other places on line and by reading "The Quantum Universe". During this process I became quite drawn to the ...
3
votes
1answer
56 views

Two different transformation laws for Quantum Fields

I found a nice answer to a problem that was bothering me for quite a while in a lecture script (unfortunately in german). The first step of the answer, is what remains unclear to me. The script states ...
0
votes
1answer
56 views

Graphene has a honeycomb lattice - true or false?

In my grand ignorance I would state that graphene has a honeycomb lattice. Some tend to agree with me and some others do not. I'm curious to know what members of the SE community think is the right ...
0
votes
2answers
40 views

Is there a relationship between the diameter of a copper wire and the bandwidth it can carry?

I'd suspect intuitively that the bandwidth should decrease as the diameter decreases, but I don't have any reasoning to back it up. Secondly, would the actual wavelengths that it can carry, also ...
10
votes
2answers
115 views

Black hole “no hair” theorem

The "no hair" theorem (or conjecture), suggests that black holes can be entirely described by their mass, angular momentum and charge. All other details of the BH formation are lost. Is there a ...
2
votes
2answers
780 views

These two operators commute…but their eigenvectors aren't all the same. Why?

The Hamiltonian $$H = \left[ \begin{array}{cccc} a & 0 & 0 & -b \\ 0 & 0 & -b & 0\\ 0 & -b & 0 & 0\\ -b & 0 & 0 & -a \end{array} \right] $$ commutes ...
0
votes
1answer
14 views

J-coupling constants and nuclei with zero total angular momentum

The Wikipedia page on J-couplings states that Scalar or J-couplings (also called indirect dipole dipole coupling) are mediated through chemical bonds connecting two spins. It is an indirect ...
0
votes
1answer
90 views

What is $g$ when traveling quickly around a planet?

I am trying to model a rocket orbiting a planet. I want to simplify the problem so that the rocket is travelling along an infinitely long flat surface with a $g$ along the $y$-axis. This is what ...
0
votes
0answers
9 views

Does a superconducting state change in a Type 2 collapse the whole superconductor?

If (say) we have a 1m length bar of a Type 2 superconductor in a superconducting state and something is done to one end of it to collapse the superconduction there, does the state of the whole bar ...
0
votes
0answers
18 views

How does lattice field theory relate to string theory?

The former is sort of a "mapping" technique with the goal of making quantum fields computable, while the latter wants to act as an underlying system of it. (as far as I know) What is their relation to ...
0
votes
0answers
28 views

A flight attendant on a plane - special relativity problem [on hold]

the question goes like this: on a plane, flying at 0.8c which is 100m long (in plane system), at the back of the plane there is a flight attendant moving at 0.55c (relativitly to the plane system). ...
4
votes
3answers
624 views

If something is not moving in space, is it moving on the time axis at the speed of light? [duplicate]

I heard this theory yesterday: If something is not moving in space, then it is moving on the time axis at the speed of light. I realize that in essence there is no object which can be considered as ...
1
vote
0answers
18 views

Difference between a “source dipole” and a “force dipole”

I know quite well what a dipole is and in general what multipole moments are (in the context of, for instance, electrodynamics). What I find myself confused by is something called a "force dipole" in ...
-1
votes
0answers
13 views

How do we measure the local distribution function of electrons in a metal?

How is the measurement of the local distribution function(or DOS) of electrons in a metal with a superconducting electrode connected to the wire by a tunnel junction done?
4
votes
1answer
131 views

In QED, why is the $e^- + e^+\leftrightarrow\gamma$ process forbidden on-shell?

QED has a vertex that couples a single photon to two fermions. This vertex describes the annihilation of an electron-positron pair into a photon. Why is this process forbidden for all three particles ...
0
votes
1answer
23 views

Determining energy stored in capacitor and inductor in RLC circuit

I've been stuck on the following homework problem for a few hours now with little progress. As you can see, it's a relatively simple RLC circuit with a couple independent sources and a ...
0
votes
0answers
3 views

Spectroscopic notation for more than one excited electron

In spectroscopy, notation like $^3S_1$ or similar is often used to define atomic states. This is unambiguous when considering only a single electron excited from the outermost energy level. But how ...
1
vote
0answers
16 views

Schwabl states that a change in external parameters cannot increase entropy. If so, how can an adiabatic process be irreversible?

I am working my way through trying to understand statistical physics, and this particular, apparent inconsistency has had me stuck for days. Any help or advice would be hugely appreciated. I was ...

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