0
votes
1answer
13 views

Do photons interact with everything?

Suppose you shoot a beam of photons in a particle collider. Are there any particles in which the photons do not interact with? Q2: What is an interaction between particles?
-1
votes
1answer
25 views

Wigner Function for Thermal State

I am currently doing a reading on the subject of Quantum Optics from the book "Quantum Optics by Marlan O.Scully and M.Suhail Zubairy", I am currently learning about Quasi Probability distributions. ...
0
votes
0answers
6 views

How to calculate possible spin of two photon system?

Photon hasn't well defined quantity such as spin. Instead of it, it is characterized by helicity $h$. Let's assume state of two photons in CM frame (with $\mathbf k$ being the momentum of one of ...
1
vote
1answer
40 views

How is the energy efficiency in bicycles accounted for?

Bikes are more efficient than walking, but that's only because roads are flat so wheels make sense, right? Does it make sense to say that this fact is simply gained by putting a lot of energy into ...
0
votes
1answer
75 views
+50

Why does the parallel component of the velocity gradient affect viscous force in a fluid?

The force density due to viscosity in an incompressible fluid is $-\mu \nabla^2 \mathbf{u}$ where $\mathbf{u}$ is the velocity and $\mu$ is the dynamic viscosity. Let's suppose some particular small ...
-2
votes
0answers
6 views

Electrodynamics

I am having some trouble with this question. Why is there such a discrepancy? Is my reasoning correct? (this is my first time on such forums.. So kindly inform me if I am posting it at the wrong ...
4
votes
3answers
148 views

Do gravitational waves propagate backwards in time?

Gravitational waves are spacetime waves, which stretch and squeeze both space and time. Since relativity puts space and time (almost) on an equal footing, it seems to me that since gravitational waves ...
0
votes
1answer
26 views

Physical meaning of enthalpy

I've been reading about thermodynamics and reached the topic about enthalpy . I've understood its derivation but I don't understand its physical meaning ... Also I don't understand why they have ...
1
vote
1answer
67 views

Monte Carlo, Non-polar optical phonon scattering?

I have a question on electron and non-polar optical phonon scattering in GaAs. Is it allowed to consider intravalley electron non-polar optical phonon scattering in L-valley of GaAs? I found in the ...
0
votes
0answers
7 views

astrophysics specially universe formation

It is said generally that nature is symmetric. for ex if light behaves as both particles and waves then matter must also do which is true.but if we see the universe we can see that there is far more ...
1
vote
1answer
209 views

Can the physical properties of the EM field be described directly from the 4-gauge potential?

I'm trying to make an argument that classically, the EM field is considered a more 'real' physical quantity than the potentials, and am tempted to say that the fact that the field carries energy & ...
14
votes
7answers
3k views

How can a battery charge up another battery to a higher percentage?

Say I have my phone on 5% and a large battery pack on 35% and I charge the phone. By the end the phone is on 100% and the pack is on 12%. How can the battery pack charge the phone up to a higher ...
-2
votes
1answer
30 views

Why speed of light is constant with respect to any inertial frame of reference? [duplicate]

Its getting too difficult to think.if we travel at the speed of light then will light will cross us at same speed or travel with us adjacent (special theory of relativity)
0
votes
0answers
6 views

question from nuclear models byJudah Eisenberg and Walter Greiner

On page 311 of the book nuclear theory by Judah Eisenberg and Walter Greiner. Now for identity (49) which is: $\omega_{1,2}^2=\frac{\omega_\alpha^2+\omega_\zeta-2bc\omega_\alpha\omega_\zeta}{2(1-b^2)}\...
53
votes
2answers
7k views

Is it possible to “see” atoms?

As per my knowledge, atoms are small beyond our imaginations. But there is an image on Wikipedia that shows silicon atoms observed at the surface of silicon carbide crystals. The image: How can we ...
0
votes
0answers
9 views

Explosion of a object into fragments and their position? [on hold]

While I was looking through my textbooks, I found a question: An isolated particle of mass $m$ is moving in a horizontal plane (the $x$-$y$ plane) along the $x$-axis at a certain height above the ...
0
votes
0answers
21 views

What is the relation between the Boltzmann distribution and Boltzmann equation?

The Boltzmann equation without collision operator $\Omega$ is as follows: $$\dfrac{\partial f}{\partial t} + \mathbf v \cdot \nabla f = 0 \tag{1}$$ Where $\mathbf v$ is the velocity, and $f$ is the ...
2
votes
1answer
192 views

Is the Maxwell distribution a solution of the Boltzmann equation?

I am studying about the Boltzmann Equation for non-equilibrium rarefied gases (dilute gases to be more specific): $$\frac{\partial f}{\partial t}+\pmb{v}\cdot\nabla_{\pmb{x}}f=Q(f,f)$$ My question is ...
0
votes
0answers
17 views

How To Arrive At Ground State Metric of Kaluza-Klein Theory

The ground state metric, after an extra dimension of space is compactified (to a circle) in Einsteinian gravity, is the metric which corresponds to the R_4 × S_1 geometry of the separated dimensions. ...
0
votes
0answers
23 views

Euler-Lagrange Equation in Quantum Field Theory

The quantum fields are operator valued distributions. In some sloppy books like Peskin and Schroeder the Euler-Lagrange equation are used to get the equations of motion. What does it mean to take a ...
-1
votes
0answers
13 views

Which lightning (/physical phenomenon) did I witness to?

I witnessed a lightning at quite close distance, but since it was somewhat unusual, I was wondering what it was more exactly. I was on a pier on a small river; the weather was relatively clear - ...
0
votes
1answer
17 views

Multi-particle systems with different accelerations

While taking a system of multiple bodies under motion, is it possible to take those bodies in a system which have different accelerations? Say there are 3 particles having acceleration along x,y and z ...
2
votes
2answers
3k views

Young's Double Slit experiment question

Q-A beam of light consisting of two wavelenghts 600 nm and 450 nm is used to obtain interference in Young's Double Slit experiment (YDSE). Find the least distance from the central maximum where the ...
0
votes
0answers
17 views

Acceleration mass graph of constant force

If the same horizontal force is applied to objects of different mass. Which graph explains the experimental results. My logic was that since $$ f = ma $$ Is a linear equation it will be a straight ...
4
votes
1answer
165 views
+100

Electric Potential Field of Parallel Electrodes within Grounded Shell

Any help would be greatly appreciated I think I need to solve this using boundary potential conditions and Laplace equations. Here is the system I'm attempting to model: The red rods are metal ...
6
votes
2answers
517 views

Why do single particle states furnish a rep. of the inhomogeneous Lorentz group?

Following up on this question: Weinberg says In general, it may be possible by using suitable linear combinations of the $\psi_{p,\sigma}$ to choose the $\sigma$ labels in such a way that $C_{\...
0
votes
0answers
12 views

complete local thermal equilibrium and conserved quantum numbers

I am reading Weinberg's Cosmology book and I am confused of the statement "complete local thermal equilibrium in which all conserved quantum numbers vanish". My question is: How is complete local ...
0
votes
2answers
58 views

Curvature of Hilbert space

That may appear as a dumb question, but: Does Hilbert space have curvature, or is it a flat space? How and why?
-2
votes
0answers
23 views

what is the rough motion of an electron in an atom

If The Uncertainity principle is true,then how does an electron move ?if the motion cannot be random also,then how does it occur?
2
votes
3answers
66 views

Can astronomers observe neutron stars optically?

Are there any neutron stars near enough for astronomers to observe them optically? If not, then how close are we to having the technology to do so?
-2
votes
1answer
59 views

Observation and deduction about a stick

Given a horizontal stick AB and a string, of course a stick that is hang on the string in its center of mass is in equilibrium. This is a fact that we take as rule because we can observe it, right? I ...
2
votes
1answer
4k views

Calculating rate of vaporization of water

Let there be a cylindrical vessel with diameter D that only has liquid water and water vapor as the picture below shows (The water vapor is the grey portion and the liquid water is the blue portion). ...
5
votes
1answer
143 views

Derivations of Newton's laws?

I feel convinced that the mathematics behind newtons laws can be derived from Noether's symmetry theorems. The fact that displacement s can be described by a cartesian coordinate system with a ...
1
vote
1answer
102 views

Differences between thermal and non-thermal plasmas

I have a doubt about plasmas which may as well be trivial or very stupid, but I couldn't get a clear and straightforward answer anywhere I looked, and I can't get the grasp of it since I wasn't given ...
0
votes
0answers
15 views

Total dilation of a signal from Tau Sagittarii [on hold]

Please forgive my ignorance, but I'm attempting to figure out how to do this... I want to learn how to evaluate the total dilation of a signal (waveform) leaving Tau Sagittarii to us. This assumes ...
-1
votes
0answers
19 views

how can I detect cosmic muons from background?

Is there anything I should be careful with if I would like to detect muon at sea level? Noise background? Threshold? Even signals from other particle with stronger flux rate?
3
votes
0answers
13 views

Inflaton Decay Rate

After inflation, (p)reheating is supposed as the mechanism which is responsible for restoring hot Big Bang. Always the resulting decay rate of inflatons into bosons and fermions are mentioned without ...
0
votes
1answer
45 views

Is Biot-Savart Law valid for time-varying currents unlike Ampere's law?

I have just finished learning the basics of magnetism, and it should be noted that I am not very familiar with Maxwell's equations. Note: In the question, when I say "Ampere's Law", I am referring ...
6
votes
8answers
2k views

Prove that an electron in a hydrogen atom doesn't emit radiation [duplicate]

According to electrodynamics, accelerating charged particles emit electromagnetic radiation. I'm asking myself if the electron in an hydrogen atom emits such radiation. In How can one describe ...
-2
votes
0answers
20 views

Beats: frequency of resulting wave vs. beat frequency

The beats frequency heard from the interference of two sound waves with frequencies $f_1$ and $f_2$ is $$\nu=|f_1-f_2|$$ Nevertheless the frequency of the resulting wave is not $\nu$ but the mean ...
-1
votes
0answers
28 views

Could Earth being multipolar 600 million years ago might have caused Cambrian radiation?

According to some of the latest research Earth might have been multi polar instead of being bipolar 650 million year's ago (http://phys.org/news/2016-06-earth-ancient-magnetic-field.html) Do you think ...
5
votes
0answers
21 views

How are coherent astronomical objects imaged?

I am studying astronomical imaging, and am curious about how to image astronomical objects which are coherent. Stellar interferometry measures the mutual coherence function of a star, and then uses ...
6
votes
1answer
373 views

Quantum Hall Effect and Edge States

In quantum hall effect we measure the hall conductance (in transverse direction) which is quantized. My question how do they take care of the edge states that are in the longitudinal side?
1
vote
0answers
35 views

Charged pendulum oscillations

Recently, a question was asked in our school, regarding the calculation of the time period of a charged pendulum bob suspended in an electric field with the help of an insulating thread(gravity also ...
0
votes
0answers
23 views

What enclosed geometry amplifies sound the most?

I am going to build a record player. It will read sound electronically but I also want it to be able to project sound mechanically, like a classic record player. So if sound enters a tube, can you ...
2
votes
1answer
50 views

Clarifications on Ampere's Law [on hold]

I have just learnt Ampere's Law, useful for calculating the magnetic field in situations having a high degree of symmetry. However, I have some conceptual doubts regarding it: Before I begin, I would ...
0
votes
2answers
86 views

Can two different objects or system of molecules have different temperatures, but having same internal kinetic energy?

If I take an extreme case, where a body has only an internal potential energy with zero internal kinetic energy, does this body have a temperature? Another question related to it: if two objects A and ...
0
votes
0answers
15 views

Decomposition of the Time-Evolution Operator: Translationally Invariant MPO

Hello everyone myself Sudipto. Currently I'm learning the matrix product state technique in order to simulate 1d spin system and study different properties of the system form quantum information ...
-1
votes
2answers
23 views

Radius of sphere formed by equipotential surface of point dipole

One of the Equipotential surface formed by point electric dipole placed in parallel electric field forms a sphere enclosing the dipole.how to find the radius of the sphere?
-3
votes
0answers
30 views

use of earth magnetic field

If we use earth magnetic field as a big magnet and take earth opposite charged electromagnet than it is possible that earth opposite charged electromagnet repel from earth surface.

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