1
vote
0answers
10 views

Correlator of the harmonic oscillator at finite temperature

The correlator $G_\beta(\tau, \tau')$ of the harmonic oscillator at a finite temperature $\beta$ is given by $$ \DeclareMathOperator{\Tr}{Tr} G_\beta(\tau, \tau') = \frac{1}{Z_\beta}\Tr ...
1
vote
0answers
15 views

Can one calculate the distance from Earth to the camera, given a single picture?

Given an image of (part of) a sphere of known size, can one calculate the distance to the camera based on the relative size of the sphere in the image? My instinct is "no" unless you have some fixed ...
-1
votes
0answers
9 views

energy from nuclear decay prevention

A neutron is stable when next to a proton in hydrogen but unstable if two neutrons are present. Could energy be obtained by preventing neutron decay in tritium with a strong magnetic field using Lenz ...
-1
votes
1answer
16 views

Straining/burning sensation in eyes [on hold]

Why does prolonged Television viewing in a dark room cause eye strain while in a brighter room doesn't?
0
votes
1answer
49 views

Quantum Mechanics in Electric Field

I am working on a problem which looks like this. Consider a charged particle with charge $q$ trapped in a box of length $L$ with finite constant potential $ V_0 $ on both ends. A constant (static) ...
2
votes
1answer
69 views

Can two electrons have the same momentum and spin directions?

I am trying to understand the Pauli exclusion principle. Here is an except from Feynman Lectures on Physics It just isn’t possible at all for two Fermi particles—such as two electrons—to get into ...
5
votes
2answers
40 views

Interpreting some domain issues of (potential) momentum operators

In the context of mathematical quantum mechanics, a well known no-go theorem known as Hellinger-Töplitz tells us that an unbounded, symmetric operator cannot be defined everywhere on the Hilbert space ...
-2
votes
0answers
24 views

How to calculate anti log for this different case? [on hold]

While solving a numerical , I came to a step where log k = 2.45 x 10^-3 So K = anti log ( 2.45 x 10^-3 ) But how to calculate the anti log of this number ? I just know to calculate the anti log ...
-1
votes
0answers
13 views

Magnetic field due to infinitely long and thin conducting ribbon of width $b$ [on hold]

An infinitely long and thin conducting ribbon tape has a width of $b = 5$ cm and a constant current $I = 10$ A flows through it, uniformly. Calculate, in vacuum, the magnetic field $\overline{B}$ in a ...
0
votes
1answer
17 views

What temperature is achieved in focus point by 5000 flat 1x1cm mirrors onto a satellite dish?

There is this video ("R5800 Solar Death Ray") where teenager built a 5000 mirror device which concetrates the solar rays which is showing the potency of the mosaic method of concentrating sunlight ...
0
votes
0answers
8 views

Intuitive way to explain why the edge states of topological insulators are dissipationless?

I was just wondering if there was an intuitive way to see why the edge states of topological insulators are dissipationless. More mathematically, is there a quick proof for why the edge states are ...
0
votes
2answers
39 views

Percent error calculations dilemma

I have a set of experimental results for calculating g: 9.82 9.52 10.77 10.39 9.75 9.79 10.13 10.56 10.26 9.84 10.07 9.58 These were taken using a pendulum experiment. My dilemma is that, ...
-1
votes
2answers
16 views

What is the difference between the actual distance covered by a projected object and the displacement?

What is the difference between the actual distance covered by a projected object and the displacement? A stone was projected with an angle of projection of 30 and it covered a horizontal distance ...
0
votes
0answers
31 views

Learning how to use Levi-Civita symbol

I've recently started my second course in Quantum Theory and am now often required to prove more complex commutation relations. I'm aware that the Levi-Civita symbol often makes this sort of thing a ...
4
votes
1answer
75 views

Energy conservation of Virtual Particles - Quantum Fluctuation?

I (as a middle-school student) was wondering how virtual particles even conserve energy of the entire system? I don't mean just the particle's energy, but conservation with respect to the ...
0
votes
0answers
16 views

Capacitance between multiple conductors [on hold]

So, I am having trouble figuring out the capacitance of systems like these( 3 parallel wires) First and third are connected so their potentials are the same, and since their radii are also the same ...
10
votes
1answer
240 views

Which hemisphere am I on?

Inspired by this answer to a question on Puzzling.SE (which contains the old but wrong idea that the Coriolis force determines the direction in which a bathroom vortex rotates, and also an approach ...
0
votes
1answer
13 views

A question on the partition function, having a degenerate energy level [on hold]

We are told that a system A is in thermal equilibrium with a heat reservoir at temp T. the system has 4 states with corresponding energies o,2e,3e and 5e then asked to assume that energy levl 3e is ...
0
votes
0answers
15 views

breitenlohner freedman stability condition

I am looking for a simple way to derive the breitenlohner-freedman bound. Actually I can't understand why we have stability above the BF bound and instability below the BF bound,while both have ...
2
votes
0answers
25 views

Why do electrons form Cooper pairs below certain temperature? [duplicate]

Just a heads up - please make this answer understandable to around 1st year degree level physics - not PhD research. So I can understand it - thanks. 1) In solid state physics, why is it that below a ...
1
vote
0answers
25 views

Some books to bridge the gap before GR [duplicate]

I am extremely interested in GR, but somehow feel that the books I read are not really enough. Frankly, I find many question on this site and elsewhere completely bewildering, which makes me think ...
0
votes
0answers
25 views

Simple questions on the symmetric eigenstate and time-reversal (TR) breaking eigenstate?

Followings are two independent questions as implied by the title: (1) Considering a quantum Hamiltonian $H$ possesses some symmetries described by a symmetry group $G=\left \{ g_1,g_2,...,g_n \right ...
1
vote
0answers
18 views

Why do weak interactions give such slow decay rates, if the analog of the fine structure constant isn't signifigantly small?

Intuitively, it seems as though the reason would be a small value for the coupling constant, as the probability for emitting $W^{-}$ bosons would be low. However, it's value is almost the same as the ...
1
vote
0answers
11 views

What makes Monocrystalline silicon a semi-conductor? [on hold]

I'm researching Monocrystalline silicon for a school project and focusing on its application in Electronics. One area I'm researching is how the structure of the material makes it a good ...
1
vote
0answers
20 views

Is a sonic boom loudest when source is at exactly Mach 1?

Please imagine this cartoonish thing: a flying loudspeaker, playing a continuous sound, with zero air resistance (i.e its moving through the air doesn't generate any whooshing sounds) is coming ...
0
votes
0answers
21 views

What does one get when admitting negative mass? [duplicate]

So essentially, both gravitational and electric fields behave in exactly the same way. The only difference is that, while mass can only be positive, charge can be positive or negative. As I understand ...
0
votes
1answer
31 views

Can this type of graph be analysed to produce any meaningful data?

The above is a graph of pendulum length on the x-axis measured in metres, and pendulum period on the y axis measured in seconds. The pendulum period is not squared. I know that if I square the ...
-2
votes
2answers
91 views

Why should Newton's third law necessarily be universal?

I read all the previous answers concerning the 3rd law and I have seen that it is definitely not universal. Newton derived his law from the collisions in a primitive 'cradle'. Why do physicists ...
0
votes
0answers
10 views

What type of the charge particle were there at time of formation of the solar system according Nebular hypothesis.? [on hold]

When our solar system created by nebular hypothesis or any other theory. What type of the particle would be there? Charged particle? Are these accelerating or moving with high speed with different ...
0
votes
0answers
18 views

How derivate paradox of dicressiang the charge in Liénard–Wiechert potential?

My professor discuss the Liénard–Wiechert. and give the formula for the moving point charge. there was a paradox by which it charge density is replace by the charge with paradox times of decreasing ...
0
votes
1answer
28 views

Does the lack of absurdities in our universe call into question the validity of multi verse theories? [on hold]

Does the lack of absurdities in our universe call into question the validity of multi verse theories? If the theories about multi verse are to be true and we have explained the immensely improbable ...
0
votes
0answers
19 views

What is the physical interpretation of time-energy uncertainty? [duplicate]

I have a question. What is the physical interpretation of time-energy uncertainty?
0
votes
0answers
26 views

Negative Feedback [on hold]

In the circuit in figure below the narrow resistor is made of the same material as the thick connecting wires. (a) Sketch a graph of the electric field’s magnitude at different locations. (b) ...
-1
votes
0answers
15 views

light movement, not in a straight line [on hold]

In physics class our teacher asked when the light doesn't move in a straight line, why, and how can we use it.I looked for an answer all over the internet and found photography sites and the physics ...
0
votes
1answer
18 views

What is the speed at which hydraulics take place

Consider a long pipe filled with some newtonian liquid, with piston at both the ends. You push the piston at end A, and observe it at the other end B. How much time does it take for piston at B to ...
-2
votes
0answers
8 views

Prandtl's equation - Calculating coefficients [on hold]

I don't even know how to get started. Could you please give me a clue? I haven't seen a similar problem before.
0
votes
1answer
34 views

What happens when ice melts? [on hold]

Case 1: You take x litres of water and cool it to solid ice(say 0 degree) and measure the volume of ice as ...
1
vote
1answer
39 views

Is it possible to use “negative sound waves” to “cancel out” a sound to create silence?

I saw youtube videos that claimed to do this, although I'm quite certain the videos just excluded sound and lied. However, I am wondering if the physics of this is actually possible - to create a ...
0
votes
1answer
35 views

constant $c$ in Lorentz force

I met some of examples of force in studying classical dynamics, and Lorentz force was represented as $$ \mathbf{F}=\frac{q}{c} \mathbf{\dot{r}} \times \mathbf{B} $$ I've searched for meaning of $c$, ...
2
votes
1answer
39 views

Why does light fade from a room?

So basically in my toilet I have this really bright ceiling light, but when I turn it off it doesn't just instantly plunge me into darkness, but rather sort of fades out over a few seconds. It looks ...
1
vote
2answers
43 views

Can Newton's Law of gravity be deduced using dimensional analysis?

I tried using dimensional analysis to deduce Newton's law of gravity but I wasn't able to do so as one of the equations were $0=-2$ which is a contradiction. But I thought that we can't do that ...
1
vote
0answers
20 views

How can colors from heat tinting depend on temperature only?

Colors caused by heat tinting of a material can be listed by temperature. For example, for carbon steel: ...
0
votes
1answer
52 views

No need for spin?

Here's a cool idea: we don't need spin: recall that a quantum field arises from an attempt to construct an object that transforms unitarily under $SO(1,3)$ (i.e. by choosing a representation). A ...
0
votes
2answers
19 views

Does gravity change the pressure of a column of water when the column is tilted from horizontal to vertical?

I need to settle an argument. I think gravity causes a column of water to exert greater pressure against the walls of a pipe in which it is contained as it is tilted from horizontal to vertical. In ...
8
votes
5answers
634 views

Is a suit that hides a soldier's heat signature fundamentally possible?

I recently played "Crysis", a game where the protagonist wears a suit that allows the player to hide both himself and his heat signature. Then I watched Iron Man 3, where a kid suggests that Tony ...
0
votes
2answers
101 views

How can Terminal Velocity be greater than gravity? [on hold]

It's been over a decade since my last high school physics class, so I apologize in advance if this is a dumb/ignorant question, but how can a skydiver fall faster than the speed of gravity? If gravity ...
2
votes
0answers
8 views

Main differences between elastodynamic and light scattering when using S-matrix to find bound states

What are the main differences (top 5 if question is too broad), for using the S-matrix to find bound states, between elastodynamic and light scattering? (if it facilitates a higher quality ...
0
votes
0answers
47 views

Is Japan truly the “Land of the Rising Sun”? [on hold]

Is it possible to determine which part of earth was first to receive sunlight? In that light, is it not just convention that the western time is later than the eastern time? I do not see a reason why ...
1
vote
0answers
17 views

Relaxation time approximation in Drude model apparant paradox

In the Drude model of the free electron gas to explain the conduction of a metal, the relaxation time approximation that the electron has a collision in an infinitesimal time interval $dt$ is ...
0
votes
0answers
31 views

Results from TLE & SGP4 propagation - don't seem right & need help with interpretation [on hold]

I acquired a TLE of the ISS from internet and used the C++ SGP4 propagator to compute future position and velocity vectors of the Station. I am a little unsure about some aspects of results though and ...

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