2
votes
1answer
30 views

Energy conservation around a black hole

In the Schwarzschild black hole, the Killing vector "time translation" $k^a$, so that the following quantity is conserved along a geodesic: $$E = -g_{ab}k^au^b = (1 - ...
1
vote
1answer
30 views

100 lbs of drag? Really? Chain running physics

Recently came across this video of an endurance technique involving the strapping of a 100lb chain to one's back and running along the grass dragging it behind. What is the true force experienced by ...
2
votes
0answers
15 views

Kitaev chaing, time reversel symmetry, particle hole symmetry

I was wondering if the Kitaev chain has time reversal symmetry. I think it probably doesn't because by staking Kitaev chains it is possible to create a so called Chern insulator with propagating ...
4
votes
2answers
103 views

Are the path integral formalism and the operator formalism inequivalent?

Abstract The definition of the propagator $\Delta(x)$ in the path integral formalism (PI) is different from the definition in the operator formalism (OF). In general the definitions agree, but it is ...
0
votes
0answers
10 views

Excitation of air with the eigen-frequency

I was just wondering (as a layman) what the eigenfrequency of breathable air is? If it exists: what would be the effects of exciting air with its eigenfrequency (w/ regard to humans, matter nearby?)
0
votes
0answers
31 views

Calculation of charged sphere distribution near a wall in Cartesian coordinates

I am following a similar derivation as found in the beginning of this paper "Quantitative aspects of the growth of (charged) silica spheres" by A.P. Philipse. This paper calculates the growth of a ...
2
votes
1answer
252 views

Heuristic equation for Friction force between materials

I'm programming a game where different types of objects will be sliding over different types of terrains (Top-down in two dimensions). At my current level of physics education we are given the ...
0
votes
2answers
68 views

What is more fundamental: Geometry and Topology or physical matter? [on hold]

Since, there is always an interplay between gravity and the fabric of spacetime. I wonder which is more fundamental: Geometry and Topology or physical matter?
6
votes
4answers
2k views

How much does the Earth's rotation affect a golf ball?

When launching rockets into space, they start straight but begin to lean, I assume due to the Earth's rotation. For something on a much smaller scale, such as a golf tee, is there a measurable ...
0
votes
1answer
18 views

Energy (voltage) correction on energy level between metallic electrodes with dielectric and accounting for work function difference

My goal is to understand how to correct for the field drop and the work function difference when performing electrical measurements on a certain energy level of a sandwiched system. The situation is ...
1
vote
0answers
33 views

Indicating that indices are equal in Einstein notation

tl;dr: I have an expression like this: (dramatization) $$ R_{\mu\nu} = \begin{pmatrix} B^{00}C_{00} & 0 & 0 & 0 \\ 0 & B^{11}C_{10} & 0 & 0 \\ 0 & 0 & B^{22}C_{20} ...
0
votes
2answers
23 views

Probability of Millikan's drop gaining or losing charge during the experiment

I performed Millikan's experiment with latex drops. I did not get the "step graph" that I wanted (though the precision of the experiment was really bad as seen in the figure). My first drop is ...
0
votes
2answers
38 views

How do I use a free body diagram in this case? [on hold]

In the above cases I want to find the acceleration $a$ for $m_1$. I can do it by considering $m_1$ and $m_2$ to be a system, which would give me $a = F/(m_1+m_2)$. How can I use a free-body diagram ...
0
votes
0answers
23 views

Does a photon follow a straight trajectory in a thin transparent film?

Does a photon follow a straight trajectory in a thin transparent film if the source has emitted a photon inside the film with impulse parallel to the film surface. (lambda greater than thickness)? ...
2
votes
0answers
13 views

Derivation of generation of time between two subsequent particle enters into computational domain

I have problem with understanding derivation of one equation in following problem. You have 1D computational domain (it is not 1D but because it is symmetrical and we are watching only radial ...
3
votes
2answers
53 views

What happens if I slowly lower a dangling object into a black hole?

I could've sworn I've seen this question before, but I couldn't find it. Suppose I have an object on the end of a really long string. I can slowly lower it near the event horizon of a black hole, ...
0
votes
0answers
8 views

Change in Q factor on tuning external magnetic field in Electron spin resonance experiment

Does the Q factor of the cavity resonator show a dip at the resonant value of the external magnetic field while performing an ESR experiment?If so, what is the physical reason behind it?
0
votes
0answers
9 views

Lorentzian nature of reflected microwave power in Electron Spin Resonance

Reflected microwave power has Lorentzian shape when plotted against frequency in ESR. How to mathematically prove this?
0
votes
1answer
28 views

electron in magnetic and electric field

I have this problem where i should find the direction and magnitude of the electric and the magnetic force on the electron. And then I'm supposed to find the direction and magnitude of the ...
1
vote
1answer
32 views

Derivation of Biot Savart law for a curve

I'm ok with the following expression for Biot-Savart: $$ {\mathbf B}({\mathbf r}) = \frac{{\mu _0}}{{4\pi }}\int\frac{{{\mathbf J}({\mathbf r'}) \times {(\mathbf{r-r'})}}}{{|\mathbf{r-r'}|^3 }}dV'. $$ ...
0
votes
1answer
150 views

Internal Resistor in a Diode

When we talk about the resistance of a diode (of the P and N region), is this resistance like the one inside an Electro-Motive Force or it acts like a normal resistor (external electric field exist)? ...
1
vote
2answers
82 views

Is multiplication in physics purely mathematical or is there a physical explanation to it?

Here is what I mean: We always use mathematics in physics, which is pretty powerful, but I still need to ask whether multiplication in physics has a better explanation to what I already think. For ...
2
votes
1answer
62 views

Is Phone-Charging Plant Product Even Possible?

Bioo, a new company making the rounds in the press, claims to produce "electricity from plants' photosynthesis." Specifically, their website claims that a single potted plant with their integrated ...
8
votes
1answer
818 views

Defy gravity torques with gyroscopes?

Context On the following drawing, a platform is hung from the ceiling not exactly from its centre of gravity. Because of this it can't sustain an arbitrary orientation for long; I want to increase ...
1
vote
2answers
66 views

Using $\sqrt{-g}$ in integrals of proper volume

I am a little confused over integration using proper volume element. When do we use $\sqrt{-g}$ in calculations? For example, in many calculations involving stars, say when using TOV equation, this ...
0
votes
1answer
32 views

Understanding electric potential in the context of gravitational potential?

I'm trying to understand the concept of electric potential and the significance of an electric field being related to the gradient/derivative of an electric potential. I found this question that ...
0
votes
0answers
34 views

How many observations over an atom can be made?

In order to determine the orbitals of any unknown atom , is it possible to make and record direct observations of electrons around the atom without disturbing the atom ? How many observations can one ...
2
votes
1answer
113 views

Continued Fraction Algorithm in Shor's Algorithm

I am just trying to make the final link of Shor's algorithm clear. Here $r$ is the order of $x$ modulo $N$. We have a number $\psi$, which for a rational number $\dfrac{s}{r}$ satisfies ...
0
votes
1answer
37 views

Fine structure constant and unit conversion

In a paper I'm reading, the author writes down the following formula: $$\Gamma=\dfrac{\alpha^2}{576\pi^3}\dfrac{\left(4+z\right)^2}{z}\dfrac{m^5}{m^2_\pi f_\pi^2}$$ $\Gamma$ is a function of $m$ (in ...
2
votes
1answer
24 views

Why is hot wood ash more fluid than cold ash?

When I remove ash from my fireplace I do so by scraping it away through holes about 5 millimeters wide in the fireplace floor. Whenever the ash is hot, it definitely feels much more fluid than when it ...
1
vote
4answers
191 views

Voltage - Energy drop

I'm having a hard time understanding the nature of voltage and am hoping you guys can help. The main issue is the concept of the voltage drop. Take the following circuits : In regard to the first, ...
5
votes
1answer
65 views

How to motivate the importance of the spacetime interval

The spacetime interval is a rather important thing in Special Relativity. It allows us to define the separation between any two events as spacelike, timelike or lightlike and more importantly, the ...
0
votes
2answers
29 views

Lowest energy product state of a local hamiltonian

Lets consider one-dimensional spin chain with periodic boundary condition and $N$ sites. We are given a translationally-invariant local hamiltonian $H$ which is defined as $H=\sum_{i=1}^N h_{i,i+1}$, ...
0
votes
0answers
20 views

Is there a preferred mode of exchange of gluons?

Red , Blue and Green quarks are colorless when put together and thus the color of the proton remains colorless.In principle quarks can exchange colorless gluons to keep quarks together. Quarks can ...
0
votes
1answer
31 views

What processes create or destroy information?

From a classical standpoint, it seems pretty clear that information can be easily lost. If you knock over a bookshelf and the books fall out, it seems like their initial order on the shelf cannot be ...
0
votes
3answers
51 views

How does frost form above freezing temperature?

This is a follow-up to the best answer linked below: Why does ice form on bridges even if the temperature is above freezing? I've witnessed that phenomenon, recently. The temperature was above zero ...
0
votes
1answer
14 views

Exponential decay of correlation in PEPS

PEPS (Projected Entangled Pair State) is a tensor network that plays the same role in two dimensional lattice as MPS (Matrix Product State) plays in one dimensional spin chain. A good introduction can ...
3
votes
1answer
187 views

How to obtain a vector relation for the Rabi frequency?

In this paper by Golovach et al.: http://journals.aps.org/prb/abstract/10.1103/PhysRevB.74.165319 there is the following equation for spin evolution: $$\langle \dot{\bf{S}} \rangle=({\boldsymbol ...
1
vote
1answer
15 views

Michleson Interferometer fringe shift

I have a problem with interferometer fringe shift. I am learning it from my physics book. In the book, it is written, "As the L1 (Displacement of moveable mirror) is changed, the pattern of ...
6
votes
4answers
793 views

Why is Newton's first law necessary?

Newton's second law says $F=ma$. Now if we put $F=0$ we get $a=0$ which is Newton's first law. So why do we need Newton's first law ? Before asking I did some searching and I got this: Newtons first ...
0
votes
0answers
35 views

Has anyone explored a possible duality between quantum gravity and statistical mechanics?

There is a well known duality between quantum mechanics in D dimensions and classical statistical mechanics in D+1 dimensions. Specifically, the Euclidean version of the path integral in D dimensions ...
4
votes
4answers
12k views

What is the difference between Raman scattering and fluorescence?

What is the difference between Raman scattering and fluorescence? Both phenomena involve the emission of photons shifted in frequency relative to the incident light, because of some energetic ...
1
vote
0answers
15 views

calculation of mean energy value of CMB photons for recombination

I am interested in the calculation of the mean energy value of CMB (Cosmic Microwave Background) photons from which the recombination is performed. The subject on French Wikipedia says : ...
0
votes
0answers
13 views

Multifractal spectrum of a signal using wavelet transform [on hold]

How to extract singularity spectrum from wavelet partition function.? Please can any one help me with a Matlab code.
0
votes
0answers
26 views

How many quanta on average, at room temperature?

I have a nanoparticle consisting of four copper atoms. My assignment is to find out how many quanta of energy, per average, are in this nanoparticle at room temperature (293 K). I'm aware of the ...
0
votes
1answer
132 views

How can energy be negative in a finite square well?

Say if the potential $V(x) < 0$ in the well but the sides or the scattered states its zero potential, anyways How is that the energy in the well is less than zero? Is it because the potential ...
-3
votes
0answers
30 views

Difference in time for clock in attic vs clock in cellar [on hold]

This question is regarding relativity: Two clocks are stationed in a house, one in the cellar and one it the attic. Which one of the following statements is true? A : The clocks tick at the ...
1
vote
1answer
46 views

Time-ordered product of two normal-ordered products of fields

Suppose you have a scalar field theory with field operators $\phi(x)=\phi(x)_+ + \phi(x)_- $ that can be decomposed into terms of annihilation and destruction operators. Let $$ D(x-y) = ...
0
votes
1answer
35 views

Is potential energy included in internal energy?

I thought internal energy is only the energy due to molecular motion and chemical bonds, but here it says it's also the potential energy of the system! Is that true?
4
votes
2answers
106 views

Does QM unequivocally violate the law of bivalence?

I had heard that QM violates the law of bivalence. Does anyone claim that?

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