All Questions

Filter by
Sorted by
Tagged with
0 votes
0 answers
11 views

Which symmetries lead to the ladder operators of the harmonic oscillator

It seems like symmetries usually lead to ladder operators. For example in a central potential problems the conservation of angular momentum leads to angular momentum ladder operators being used in the ...
eli morhayim's user avatar
1 vote
1 answer
16 views

Moment of Inertia of cube about the axis along one of its diagonal

How can we find Moment of Inertia of a solid as well as a hollow cube about the axis passing from one of its diagonal? I tried really hard solving it, please guide me to the solution.
Het Patel's user avatar
1 vote
0 answers
24 views

In which direction is the relation between the time-component of celerity and the Lorentz factor defined?

Celerity (a.k.a. four-velocity) is defined as $w^\alpha=\frac{\mathrm{d}X^\alpha}{\mathrm{d}\tau}$, where $\mathrm{d}X^\alpha=(\mathrm{d}t,\mathrm{d}x,\mathrm{d}y,\mathrm{d}z)$ and $\mathrm{d}\tau$ is ...
controlgroup's user avatar
0 votes
0 answers
26 views

Distributing 3 distinct particles among 4 distinct energy states

If we consider the following state of the above mentioned system with energy 5: $$\{|x_1x_2||x_3\}$$ Where, 2 particles occupy the state $E_1$ with energy 1 and 1 particle occupies state $E_3$ with ...
Leibniz's Alien's user avatar
0 votes
0 answers
19 views

Symmetry group and dualities

Let's say two quantum models $M_1$ and $M_2$ are dual to each other and let their symmetry groups be $S_1$ and $S_2$ respectively. Is it necessary for $S_1$ to be isomorphic to $S_2$? (I thought so ...
Barry's user avatar
  • 366
0 votes
0 answers
19 views

Can the eye lens not produce a virtual image when the object is between Focus and Optical Centre?

My teacher dismissed the question saying it is not possible for the eye to do so simply because we didn't know the focal length of the eye. That confused me. The focal length can vary, sure. When we ...
Shristeerupa's user avatar
1 vote
2 answers
39 views

Why can't thin clouds form rainbows?

Sunlight easily passes through THIN layers of clouds, composed of small water droplets/vapor, what is the problem accounted by the light rays that they are not able to form a rainbow?
Shristeerupa's user avatar
0 votes
0 answers
14 views

In which case do you get 10 spectral lines in a Zeeman spectrum? [closed]

Solving old exam questions, i came accross this question: In case of anormal zeeman effect, we observe spectral lines at a position transverse to the magnetic field and a spectral line $(l, s, j ->...
phein1's user avatar
  • 11
-12 votes
0 answers
29 views

What is PHI? Theory by Infiniti Creati, ESQ [closed]

IF PHI = "Consciousness" THEN "NOTHING" = PHIbar therefore MULTIVERSE = PHI XOR PHIbar AND UNIVERSE = PHI AND PHIbar
InfinitiCreator's user avatar
0 votes
0 answers
20 views

Quantum mechanical state expression for degenerate discrete and continues spectrum of the Hamiltonian [closed]

The setup is the following: I am considering a conservative and isolated/confined system. In order to be as general as I possibly know and can, I am considering that the spectrum of the Hamiltonian of ...
imbAF's user avatar
  • 1,398
0 votes
0 answers
19 views

Broken symmetry vs emergence of symmetry

In many condensed matter presentations going from a gas/liquid state to a solid (especially a crystal) is presented as breaking the complete translational and rotational symmetry of the gas/liquid to ...
kangermu's user avatar
-2 votes
1 answer
34 views

Big-crunch divergence? (Not very serious)

Slightly whimsical question, inspired by Poul Anderson's story "To Outlive Eternity" and novel "Tau Zero." If the Big Crunch model of cyclic cosmology actually applies in some ...
cTen's user avatar
  • 17
0 votes
0 answers
22 views

Why are the number of $k$-points in the Brillouin zone different from the number of lattice sites?

Suppose I am doing some sort of Hartree-Fock/DFT calculation in momentum-space. Let us then consider a system comprised of $N$ lattice sites, with lattice constant a. The allowed $k$-points within the ...
meer23's user avatar
  • 51
0 votes
0 answers
20 views

Spin importance for the prob. density and norm conservation

In our class, we discussed about time-dependent quantum systems. $i\hbar \frac{d}{dt}|\psi(t)\rangle=H(t)|\psi(t)\rangle$ Initial conditions: $|\psi(t_0)\rangle$ is known. Therefore we can determine $|...
imbAF's user avatar
  • 1,398
0 votes
0 answers
24 views

Derivation of Equation of Motion of Graviton

In Feynman's Lectures on Graviton, Feynman tries to simplify the equation of motion of gravitation field, $$h_{\alpha\beta,\sigma}^{,\sigma} - (h_{\alpha\sigma,\beta}^{,\sigma} + h_{\beta\sigma,\alpha}...
Ting-Kai Hsu's user avatar
1 vote
2 answers
25 views

Energy of photons in perfect mirror box with FRW metric

In FRW metric, distance is described by \begin{align} ds^2 = dt^2 - a(t)^2[d\chi^2 + S_k(\chi)^2 d\Omega^2]\\ =dt^2 - a(t)^2\gamma_{ij}dx^i dx^j \end{align} where $a$ is the scale factor. Now by using ...
littlegiant's user avatar
0 votes
0 answers
20 views

Correspondence between Fock state and Slater determinant

Let's consider the application of a bra to a Slater determinant (I shall neglect all constant factors or signs because they are irrelevant to my question): \begin{align} \langle\varphi_{k_\beta}^{(N)}|...
lhye's user avatar
  • 1
1 vote
4 answers
29 views

Conceptual doubt related to motion of two blocks on an incline

I was solving the following question: In the arrangement shown in the figure all surfaces are smooth. Select the correct alternative(s) (A) for any value of θ acceleration of A and B are equal (B) ...
Chetan's user avatar
  • 13
0 votes
1 answer
32 views

Selection rule in three dimensional harmonic oscillator in representation $(n,l,m)$ [closed]

Selection rule for transition probability of first order perturbation . But in the one where a periodic perturbation Axcos(ωt) add to a three dimensional harmonic oscillator, I don't understand why ...
Gene Vettel's user avatar
0 votes
0 answers
15 views

The angle of the prism for which there is no emergent ray will be, if its critical angle is $i_c$?

I read the answer here https://www.toppr.com/ask/question/the-angle-of-the-prism-for-which-there-is-no-emergent-ray-will-be-if/ . It said Applying snell's law at the two refracting surfaces, sini=...
Newbie's user avatar
  • 1
-2 votes
0 answers
29 views

Why do we take $v_{rms}$ speed in de Broglie wavelength not average speed for a gas? [closed]

While solving many questions, I came across many solutions where we took v as vrms speed for de broglie wavelength of a gas but why can't we take v as average speed as it would give us average ...
S K's user avatar
  • 41
0 votes
0 answers
33 views

Phonon operator in Electron-Phonon Interaction [closed]

I'm going through Mahan's many body physics (3rd Ed), and I'm having some trouble understanding a step on p.28. He has the electron phonon coupling term in terms of a Fourier Transform (Eq 1.225) $$...
Redcrazyguy's user avatar
0 votes
1 answer
17 views

Confusion about Derivation for Bragg's Law/Condition

I am currently learning about Bragg's Law and its derivation. However, the assumptions/logic behind the derivation seems flawed to me. It is probably likely that I am incorrectly understanding some of ...
grandmak2323's user avatar
1 vote
0 answers
28 views

What are the differences of Scalar and Pseudoscalar Yukawa Theory?

I know that some polarized interactions are forbidden. But for unpolarized (summed over incoming and outgoing spins), are the amplitudes and decay rates of a Yukawa scalar and pseudoscalar coupled to ...
Diana's user avatar
  • 81
0 votes
1 answer
33 views

Why does cutting a solenoid into half reduce its magntic properties

Cutting a solenoid is said to reduce its magnetic properties. Is this change attributed to its magnetic moment or to its magnetic field. Magnetic field of the solenoid could be same because the turn/...
Xlomer's user avatar
  • 1
0 votes
0 answers
39 views

Closing Door on a Moving Car [closed]

I am working a problem from the 3rd edition of Goldstein's Classical Mechanics (problem 5.23): An automobile is started from rest with one of its doors initially at right angles. If the hinges of the ...
Georgy Zhukov's user avatar
0 votes
2 answers
73 views

In equation (20) from lecture 10 in Leonard Susskind’s ‘Classical Mechanics’, why is there a summation involved?

Here is the equation $$\{x_i,L_j\}=\sum\limits_{k}ϵ_{ijk} x_k.$$ Is this equation generalised for any number of dimensions? In which case, would the following example be correct assuming 4 dimensions? ...
Bradley Peacock's user avatar
-4 votes
0 answers
28 views

Do quantum fluctuations follow Hamilton's principle? [closed]

I already asked a related question yesterday (Equation of motion of quantum fluctuations/ quasi particles), but i did not get any satisfying answer. My question is simple: Do quantum fluctuations ...
Clara's user avatar
  • 13
-6 votes
0 answers
46 views

GRAVITOELECTROMAGNETISM [closed]

Has anyone here worked on approximate theories of gravitation, such as GEM? If I hypothesize the existence of a field dual to the gravitational one, similar to how the magnetic field is dual to the ...
Arcangelo Recchia's user avatar
0 votes
2 answers
30 views

Contradiction in the Carnot Cycle?

The carnot cycle is reversible, because the temperature difference between heat reservoir and fluid is extremely low, so that heat can flow in both directions. Also, the carnot cycle is described as ...
Theiserino's user avatar
-6 votes
0 answers
36 views

Maxwell's equations in electromagnetic theory [closed]

At M.Sc physics or BS physics level a student should study Maxwell's equations with how much depth tell name of specific concept
Saqiba Ishaq's user avatar
0 votes
3 answers
46 views

Is gravitational potential energy of body by $mgh$ negative? [closed]

Consider a 15kg object at 1m from earth ground level, is P.E = 15kg * 9.8m/s^2 * 1m = 147J or P.E = -Gm1m2/r^2 * h = -9.8 * 15kg * 1m= -147J after browsing for a while on debate of potential energy's ...
Neptotech -vishnu's user avatar
-5 votes
0 answers
45 views

Oblique Projectile Motion "HOMEWORK AND EXERCISES" [closed]

It is a multi-correct question. We have a body projected from the top of a tower with specific initial conditions. $V_\text{initial} = 9.8\,\text{m/s}$ $\text{Height} = 19.6\,\text m$
Sanjith Sivakumar's user avatar
-5 votes
1 answer
35 views

Does the Earth's Magnetic Field Affect Sleeping Position? [closed]

Does the Earth's magnetic field affect the sleeping position of a person? For sleep experience with Nature sounds, check out this video: https://www.youtube.com/watch?v=5FzjrdiUr90
Shahzad Mahmood's user avatar
-7 votes
3 answers
96 views

What, exactly, does Schrödinger's wave equation describe (just in plain English, without any of the math please) [closed]

I've been studying the philosophical foundations of quantum mechanics and would love to find out if my understanding is correct. Could anyone please let me know if the below description is accurate? ...
Asli Theobald's user avatar
-2 votes
0 answers
56 views

Does Mass Actually Displace Space-Time, or does Mass only Distort it?

1. Question Given the plethora of space-time illustrations, there is a sense that space-time is actually being displaced by mass, (planets). But on its face, this doesn't really make sense because ...
elika kohen's user avatar
-3 votes
0 answers
47 views

Could Space-Time Displace or Distort Itself? [closed]

1. Question Could space-time distort and displace space-time? If space-time can interact with surrounding space-time, then which ...
elika kohen's user avatar
0 votes
0 answers
20 views

How to find permeability of a magnetic material?

I have been working with magnetic materials for quite some time now and never really explored this fundamental parameter. After looking through the literature I realize there and quite few different ...
assasinchop7's user avatar
0 votes
0 answers
50 views

Topic : Classical Electrodynamics; Lienard wiechert potentials [closed]

So I have just finished studying the Lienard wiechert potentials for a moving charged particle. After doing some problems from Griffiths I stumbled upon some problem which as follows: An ...
Souvik Pramanick's user avatar
1 vote
0 answers
44 views

How do you build a small-scale neutrino detector? [closed]

*This question is similar to: Is a DIY neutrino detector feasible?. The difference between my question, and the old one is that the question is from over 8 years ago. Naturally, some of the answers ...
Justyn's user avatar
  • 21
0 votes
1 answer
29 views

Enthalpy at constant pressure/volume

Enthalpy is defined as the heat the goes into (leaves) a system at constant pressure. $dH =TdS+ d(PV) = TdS + PdV + VdP$ For some reason, most texts simply write $dH = TdS + VdP$ but haven't they ...
David's user avatar
  • 5
0 votes
0 answers
32 views

Lorentz transformation of Creation and Annihilation operators for a real scalar field theory - MIT OCW QFT I Problem set 3 [closed]

I have been working through the MIT OCW's QFT lecture notes and problem sets, but I have come to realize that I have a fundamental misunderstanding of what is meant by how objects transform under ...
Nicolas Mendoza's user avatar
0 votes
1 answer
51 views

Does A Pivot Exert A Force

On a frictionless horizontal table, a uniform stick is pivoted at its middle, and a ball collides elastically with one end, as shown in Fig. 8.10. During the collision, what are all the quantities ...
John Doe 's user avatar
2 votes
1 answer
54 views

Parametric down-conversion - QFT necessary?

In quantum optics, one ususally starts by quantizing the free electric field and obtains an expression for the electric field operators: $$ E(\vec{r},t) = \sum_{\vec{k},p} C_{\vec{k}} \vec{e}_{\vec{k},...
sqrt6's user avatar
  • 21
1 vote
1 answer
38 views

Entanglement distance and quantum mechanics length scales

In this answer https://physics.stackexchange.com/a/9253/256311, the author said Usually, we think of quantum mechanics to govern the microscopic world, involving length scales of under a micrometer, ...
Nicole's user avatar
  • 11
-1 votes
1 answer
49 views

Why particle is certain to escape the conservative field when the mechanical energy is positive?

It is generally said that the particle is bound into the conservative field when the mechanical energy is negative and zero is the limiting case and the particle will escape the field when the ...
Het Patel's user avatar
1 vote
0 answers
40 views

Drake Equation with Random Walks

Goal I'd like to use the Drake Equation with random walk theory to estimate the probability of aliens reaching Earth. Drake Equation The Drake Equation estimates the number of advanced civilizations ...
vengy's user avatar
  • 173
0 votes
4 answers
43 views

Explanation between the potential energy of a charge and the electric force experienced by a charge

Suppose there are two opposite charges and an infinite distance between the two. At this initial point, the electric potential energy of the two charges and the electric force experienced by each ...
12-CB09 Mayor Zander P's user avatar
0 votes
1 answer
45 views

What is the frequency of a standing wave? [closed]

I understand that constructive interference of waves results in standing waves. And for a wire with both ends fixed the frequency should match the fundamental frequency of the wire to produce standing ...
android's user avatar
  • 91
0 votes
0 answers
29 views

Is there a substance which can pass both IR and UV radiations?

I have been thinking about this for a while. A quartz prism allows UV Radiation to pass. A rock salt prism allows IR radiation to pass. Glass absorbs both. Is there something, that is, a substance to ...
Ritzthephysibeast's user avatar

15 30 50 per page
1
2 3 4 5
4743