All Questions

0
votes
1answer
20 views

How far can you pee on the moon vs. mars?

Let's suppose you are at Elon Musk's Future Mars colony and you drank too much beer, how far can you pee on Mars if you can pee one meter on earth? If the next day you get on the shuttle to the ...
0
votes
1answer
9 views

How does thermal energy in a system do mechanical work?

Explain that a system with thermal energy has the capacity to do mechanical work. Also, in addition to this what are the differences between work and mechanical work?
0
votes
0answers
3 views

How to determine exchange particle of two-to-two process?

For the process, $e^+e^- \rightarrow e^+e^-$ I know that the exchange particle is a photon and for the process $\gamma\gamma \rightarrow e^+e^-$, the exchange particle would be an electron but I'm not ...
0
votes
1answer
12 views

Relative energy

Suppose a ball is travelling at 5km/h, person A is travelling at 2km/h and person B is travelling at 5km/h in the opposite direction. The ball is travelling at 3km/h relative to A and at 10km/h ...
0
votes
0answers
7 views

How was Maxwell able to derive velocity distribution?

Did he assume that their velocities follow some kind of statistical distribution and fit the parameters accordingly. Or did he mathematically prove it?
0
votes
0answers
8 views

European XFEL : TDS strutures

Can someone explain whats the difference between fill time, accelerator fill (Ta) time and cavity fill time(Tc)? Is fill time and acellerator fill time the same ?
0
votes
0answers
3 views

Bond Nature of a comound

How can we determine the type of Bond in LiBaPO4? can we find out the nature of bond through charge transfer values of these elements? if yes then how?
0
votes
0answers
15 views

Experiment interpretation. Dielectric polarization/triboelectricity/other?

My aim was to create a relatively strong electrostatic field to experiment with biological systems. So, I built a kind of "sandwich" made of a plate of aluminium surrounded by two 4mm plates of ...
0
votes
1answer
47 views

Ground state of two fermions coupled with one boson

I have an Hamiltonian of the form: \begin{align} \begin{aligned} H _ { 1 } & = f _ { 1 } \otimes b ^ { \dagger } + f _ { 1 } ^ { \dagger } \otimes b \\ H _ { 2 } & = f _ { 2 } \otimes b ^ { \...
6
votes
1answer
180 views

Is the $\alpha'$ expansion in string theory an asymptotic expansion?

The low-energy bosonic effective actions of string theory lead to Einstein-Hilbert gravity, along with scalars and $p$-form Maxwell fields. For example, the action for type IIA string theory is $S = \...
0
votes
3answers
27 views

If a wavefunction is normalized at $(x,t)$, is it also normalized at $(x\!-\!ct,t)$?

If $\Bigl( \Psi(x,t),\Psi(x,t) \Bigr) =1$, I want to find out if $\Bigl( \Psi(x-ct,t),\Psi(x-ct,t) \Bigr) =1$. My attempt was $\Bigl( \Psi(x-ct,t),\Psi(x-ct,t) \Bigr) = \int_{-\infty}^\infty |\Psi(x-...
1
vote
1answer
15 views

Molecular model of liquids

The macroscopic behavior of gasses and solids follow very intuitively from the description of matter as quasi-spherical molecules interacting with each other with attractive and repulsive forces. ...
0
votes
1answer
25 views

Radial vs tangential component of electrical field due to dipole

I was wondering that why should the maximum magnitude (with respect to $\theta$) of radial component of electrical field of an electric dipole, $$E_r=-\partial V/\partial r=\frac{2p \cos\theta}{4\pi\...
0
votes
2answers
27 views

Lorentz transformation of vector field

Under a Lorentz transformation, a vector field transforms as: $A'_{\mu}(x')=\Lambda^{\nu}_{\mu}A_{\nu}(x)$ My question is, why is the Lorentz transformed vector field evaluated at $x'=\Lambda x$, ...
0
votes
0answers
14 views

Don't matter-antimatter annihilate each other completely releasing energy as photon?

Matter and antimatter should annihilate each other completely releasing energy in the form of photon, however it is discovered that smashing electron and positron together can also spew out higgs ...
-6
votes
1answer
35 views

SuperString theory and mass-energy equivalence [on hold]

Please ignore the previous question. As i had said that i knew that the energy released in electron-positron annihilation is 511keV in form of gama rays. Please reply- What is(or whether there is a) ...
1
vote
1answer
35 views

Self-induction and conservation of energy [on hold]

back EMF when switch is open is greater than back EMF when it is on; is that opposes the law of conservation of energy?
0
votes
1answer
23 views

In static fluid, pressure at same heights are equal. Is this applicable to the oceans?

Generally we consider the reference as horizontal line. But if we consider a vertical water column in the ocean. Then, if we want to consider the reference it should be a circular not a horizontal ...
1
vote
1answer
174 views

Governing equations and boundary conditions for a steady-state compressible viscous flow in an axisymmetric annular orifice

I'm trying to simulate a 2D axisymmetric model of steady-state compressible viscous flow using Mathematica, but I get some errors. There is a chance that I'm making some mistakes with the governing ...
0
votes
2answers
15 views

Can I make an inductor coil from covered cables?

I have huge amounts of wires, and it's impossible to remove all the plastic cover off of them. I thought of making the coil just like that, as they are, will it have the same magnetic field or at ...
0
votes
1answer
16 views

Skin effect prevailing the drift velocity effect

In general, an electron will propagate randomly in a conductor at the Fermi velocity( produced due to thermal energy of the conductor). An applied electric field will give this random motion a small ...
5
votes
5answers
1k views

Entropy of photons

Do low energy photons have greater entropy than high energy photons, or is the entropy of all photons the same (and the relationship between high and low entropy radiation is just a function of the ...
0
votes
2answers
36 views

Could we use experimental evidence of micro black holes to prove the existence of additional spatial dimensions?

They are planning to create a new particle accelerator that can smash particles together at a much higher energy than the LHC. If in the process we observe the decay of a micro black hole, would that ...
0
votes
1answer
16 views

Imaginary part of vacuum polarization tensor

I deal with vacuum polarization diagram calculation with help of QED by Landau et al. and I would like to understand one interesting statement. I know how to compute $\Pi_{\mu\nu}(k)$ via dimensional ...
1
vote
1answer
22 views

How can one the find normal force of a block resting on a pool floor underwater?

There is the force of gravity on the block, the atmosphere, the water pressure o top of the block, but how about between the block and the floor? Would we calculate water pressure pushing up from the ...
1
vote
1answer
172 views

Does a lens with a given numerical aperture (NA) increase etendue, even if it follows a source (e.g. fiber) with lower NA?

It is well known that the etendue of an optical system cannot be decreased - i.e. the brightness of a source cannot simply be increased by using lenses to try and focus something more tightly. ...
0
votes
2answers
540 views

Why equivalence principle is principle and not law?

We can prove that the inertial mass and the gravitational mass should be the same (equivalence principle) from the $f=mg=ma$ then $g=a$, so we have equivalence law! But why we said equivalence ...
2
votes
0answers
22 views

What is so topological about topological phase transitions?

I am studying the KT-transition, which is called a topological phase transition. The phase transition is driven by vortices in a 2-D superfluid, where it is shown that at a critical temperature $T_c$ ...
0
votes
0answers
20 views

What kind of integration is used in different areas of physics? [on hold]

I'm aware that there are multiple types of integration in mathematics, e.g., there's the Riemann integral, the Riemann-Stieljes integral and the Lebesgue integral, but I'm not privy to their ...
1
vote
0answers
35 views

Is the Palatini-Lovelock action of order k topological in 2k dimensions?

I am interested in Lovelock actions in the metric-affine (or Palatini) formalism. It is well-known that the metric version (starting from the Levi-Civita curvature) of the Lovelock lagrangian of order ...
1
vote
1answer
90 views

Why does the Redfield equation model thermal relaxation while the Lindblad equation does not?

In open quantum systems, we model a process known as thermal relaxation. What is this process, and why is it that only the Redfield equation models this process, and the Lindblad equation doesn't?
2
votes
3answers
949 views

Why do electrons have to fall on the nucleus in the Rutherford atomic model?

As I read on Wikipedia, the Rutherford atomic model is not correct according to classical electrodynamics, as it states that electron must radiate electromagnetic waves, lose energy and fall onto the ...
0
votes
1answer
15 views

Does the distance between the slits, in the double slit experiment, affect the pattern displayed?

Does the distance between the slits affect the pattern displayed? I want a pattern where light parts and dark parts are equal, and I don't want the light parts to be bigger than dark parts.
1
vote
2answers
71 views

Paradox are all 4D distances zero?

The 4 dimension distance from the origin of a point is $\sqrt{x^2+y^2+z^2-t^2}$. Which means the 4 dimensional distance on the light-cone is zero. Take a point A and a point B in the future at ...
0
votes
1answer
177 views

Work it takes to move a charge from one point to another closer to an infinite uniformly charged plate?

In the video, (khan) says to calculate the work done on the charge to move it from a point to 3 meters closer to the plane, you multiply it by the force at the original point by the distance (3 meters)...
0
votes
1answer
68 views

Question about special relativity in Carroll lecture note

In the lecture of General relativity by Carroll, page 7 is written that: Notice the distinction between this situation and that in the Newtonian world; here, it is impossible to say (in a ...
0
votes
0answers
8 views

With respect to which system are accelerations written in a non-inertial frame?

If $\vec{a}=\vec{a_0}+\vec{a_r}+\vec{\omega}\land(\vec{\omega}\land\vec{r})+\frac{d\vec{\omega}}{dt}\land\vec{r}+2\vec{\omega}\land\vec{v_r}$ being $\vec{a}\to$ absolute acceleration of the ...
0
votes
0answers
208 views

Feynman Lectures Vol1, Chap20-3 gyroscope precession

http://www.feynmanlectures.caltech.edu/I_20.html "The gyro actually does fall, as we would expect. But as soon as it falls, it is then turning, and if this turning were to continue, a torque would be ...
0
votes
1answer
10 views

Principle of Energy Dispersive x-ray Spectroscopy

I have a question about the EDS I don't understand how the detector can differentiate the Energy of incident x-ray simultaneously. In my thought, the emitted x-ray from the sample have different ...
-5
votes
1answer
34 views

Why is the mainstream theory of cosmological redshift inconsistent with the mainstream theory of gravitational redshift

Gravitational redshift Cause : A reduction in the decompression of space* over distance (due to the presence of mass). Mainstream theory: Photons are emitted in a region of higher gravity with ...
2
votes
3answers
52 views

Explanation of Lenz's Law phenomena

If we drop a magnet through a copper pipe (without it touching any of the sides), it would fall slower than it would if there were no pipe. Having the pipe otherwise accelerate the magnet would be in ...
0
votes
0answers
3 views

Strategy for finding flow field for steady, incompressible flow in 2D based on density information

I'm working on a simulation where we wish to determine the flow field for an incompressible fluid based on known values for density at each point. The only outside force is gravity. (Density is not ...
-3
votes
0answers
42 views
0
votes
1answer
191 views

What happens to flow in a constant area duct when there is a pressure gradient?

In nozzles and diffusers the cross-section area follows the one defined by the pressure gradient. In a nozzle it decreases to keep mass flow rate constant. In a diffuser the opposite happens. But ...
-1
votes
0answers
35 views

Predicting the Frequencies of Visible Light [on hold]

Why can't the Standard Model predict the frequency range of visible light; which must rather be inferred from measures of wavelength? Given that QFT is a gauge theory in which, since the fields are ...
0
votes
1answer
43 views

How much harder is a proton theoretically speaking than a diamond?

It's generally said that a diamond is the hardest substance known to man (apparently there are a few materials known to be harder). However, one ought to expect that a proton or neutron should be ...
5
votes
5answers
105 views

How can an electrically neutral planetary core be geodynamo? [duplicate]

The standard theory for the earth's magnetic field is that the planet's core is a geodynamo. I know moving electric charges can induce a magnetic field, but I also know that opposite charges produce ...
0
votes
0answers
14 views

Determining the pseudo-time period of a system of $n$-pendulums via Kane's method in Python

We can use Kane's method to integrate the equations of motion for a system of $n$ pendulums with arbitrary masses and lengths (see derivation). In particular, if $(x_i,y_i)$ denotes the Cartesian ...
0
votes
1answer
186 views

Clebsch Gordan Coefficients in $SU(3)$

Where should I start in order to find the C-G coefficients for, say, the tensor product $$3\otimes 6=8\oplus 10~?$$ In general, is there a simple way to describe the calculation for a general tensor ...
0
votes
1answer
29 views

Proof that electrostatic self-force is zero

Suppose there is a charge distribution in region V and zero charge density outside V such that electric field goes to zero infinitely far away. How to prove that this charged body does not exert an ...

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