0
votes
0answers
13 views

Are there any specific examples of the application of Lewis-Riesenfeld procedure to time dependent Hamiltonians in QM?

Lewis-Riesenfeld invariant theory is a theory applicable to solve time-dependent Schrodinger equations. I have always encountered the theory related to the procedure, however never encountered any ...
1
vote
0answers
20 views

What is an overview of secondary school astronomy textbooks for students who have taken some calculus?

I teach mathematics at the secondary level. This year my students have founded an astronomy club. Most have finished two semesters of "college-level" calculus and are familiar with the derivative, ...
4
votes
2answers
80 views

Two inertial frames (different angles)

The motion of the earth relative to a star changes the angle at which the star is perceived. Consider to inertial frames of reference I and I'. I' moves with velocity w relative to I along the ...
1
vote
1answer
268 views

Why is an exciton only observed when we excite to the conduction band and not to other electronic level inside the bandgap?

Excitons can be observed when we excite electrons to the conduction band. I don't know about excitons being observed when we excite the electrons to an electronic level that would eventually be in ...
0
votes
0answers
7 views

Plasmon quenching vs plasmon decay. What is the difference?

I'm reading an article "Quenching, Plasmonic, and Radiative Decays in Nanogap Emitting Devices" (pubs.acs.org/journal/apchd5). I don't understand the following: Counterintuitively, we evidence ...
-1
votes
0answers
17 views

How hail stone is created?

In atmosphere water vapor condense to form water. Since density of water is higher than atmosphere it will come down as rain. Then how hail stones are formed. Before vapor get freezes to ice, why it ...
-2
votes
0answers
15 views

how to apply capstan law? [duplicate]

I am having trouble to apply Capstan Law. I don't know which side is supposed to be the large force and which the small. If you have a capstan that doesn't rotate, and you have a mass 1kg from one ...
0
votes
0answers
20 views

Relation between Canonical and Grand Canonical Ensemble for a two levels system

For a two-level system of classical non interacting distinguishable paricles, labelling energy levels as $+\epsilon, -\epsilon$, in the canonical ensemble I found for the partition function ...
0
votes
1answer
31 views

White noise in the Langevin model and it's autocorrelation function

I am having some trouble understanding and interpreting the noise term in the Langevin equation for a colloidal particle in a fluid. By the Langevin model, I mean the following model as the equation ...
0
votes
0answers
41 views

Mass spectrum of field theory

How can I find the mass spectrum of a field theory given a Lagrangian made of a canonical kinetic term and a potential. I mean, I think I have to find the matrix of the quadratic terms in all the ...
0
votes
0answers
26 views

Are alpha and beta rays also generating electromagnetic rays?

To discover radio waves in 1886, Hertz used electric sparks between two iron balls. These sparks caused radio waves which generated a current between other balls. The oscillating charges caused a ...
5
votes
1answer
1k views

Infinite-range 1D Ising model + Hubbard-Stratonovich-Transformation

I have a probably quite simple question RE the HST. After some work, I obtain as the partition function for the infinite range 1D Ising model $$Z = \int_{-\infty}^\infty \frac{dy}{\sqrt{2\pi / ...
1
vote
0answers
18 views

Ads/CFT coordinates

I have an AdS space written in Poincare' coordinates and in global coordinates. The transformation that brings one set in the other is a conformal transformation?
0
votes
0answers
33 views

Pauli matrices and $SU(4)$ [on hold]

together with the 2-dim identity matrix, the pauli matrices build a basis of the vector space of the 2x2 hermitian matrices. The set of i*pauli matrices build a basis for the SU(2). Assuming, we ...
2
votes
1answer
37 views

Can a theoretical object exist as such that its mass overcomes gravitational collapse

A daydream the other day led me to the question if "a universe filled with water (or any other substance for that matter), instead of being mostly void" could exist within the rules of our current ...
0
votes
0answers
8 views

problem in making hologram (3 sided) [on hold]

why the image become illusion in transparent glass ? (in making hologram).
0
votes
2answers
4k views

Exactly how much lift is needed to overcome the weight of an average person?

I am designing a "glider" of sorts, and I have some basic questions about the physics involved to get me started. How much lift is required to overcome the weight of an average person, say 150 pounds? ...
0
votes
1answer
50 views

Questions about null geodesic [on hold]

Show for the null geodesic in 3D flat spacetime using polar coordinates so the line element is $ds^2=-dt^2+dr^2+r^2d\phi^2$. Do light rays move on straight lines? My question is that I only learned ...
2
votes
1answer
59 views

Diagonalisation: Schmidt vs eigenvalue - when to use which?

In physics we encounter diagonalisation of matrices or operators in a variety of areas. But there are different kinds, the main two being Schmidt decomposition and eigenvalue diagonalisation. The two ...
0
votes
1answer
217 views

Electric field inside two parallel lines of charge

At what force will a particle be subjected to inside two parallel line charges with the same length and charge density. I get that in the middle the forces will cancel, but will they cancel if the ...
0
votes
0answers
12 views

Tidal heating of body

I am trying to make a plausible, though not necessarily accurate model of tidal heating of a body moving close by a gravitational attractor, not necessarily in orbit and not considering the spin of ...
0
votes
0answers
8 views

Infrared Camera spectral filtering with an uncooled camera? [on hold]

I have been doing experiments with thermal cameras and stumbled upon CO2 detection. Having ordered a filter I was full of joy and immediately tried it out - nothing happened. So I talked to the ...
1
vote
1answer
45 views

How do I calculate the differential cross section with respect to the transversal momentum?

First of all, sorry for my English, my first language is German. My problem is: I calculated the matrix element of the quark-gluon-Compton process (q+g -> gamma + q). With the kinematics of ...
2
votes
2answers
31 views

Thermodynamics : Heat transfer : Conduction or convection?

I have an hot object, that is place in a room of 20°C. My goal is to be able to estimate how warm the object will be in T seconds. To be able to do that, I must first understand what is really ...
0
votes
1answer
36 views

About periodicity of coordinates given a metric

If I am given a metric how do I decide which coordinate is periodic? Eg. can I look at metric in plane polar coordinates and tell that θ direction is periodic. Also How do I calculate the period of ...
-1
votes
2answers
33 views

Simple harmonic motion angular frequency

I'm struggling with this physics question. "A simple harmonic wave of wavelength 16 cm and amplitude 2.5 cm is propagating along a string in the negative x-direction at 35 cm/s." a) Find its angular ...
0
votes
1answer
31 views

How would one attach black hole to starship in the Black hole Starship model? [on hold]

A black hole starship is a theoretical idea for enabling interstellar travel by propelling a starship by creating an artificial black hole and using a parabolic reflector to reflect its Hawking ...
3
votes
1answer
192 views

Superposition and simultaneous observation

Trying to understand superposition. Ok, so double slit experiment. The multiple paths the particle simultaneously travels interfere with each other but as it is absorbed, it chooses one "actual" ...
4
votes
1answer
158 views

What is the difference between the Big Bang Model and the Λ-CDM Model?

If I'm going to write about "The Consensus Model of Cosmology" should I include Big Bang Model or should I go with just the $\Lambda$-CDM Model?
-1
votes
1answer
49 views

I can get a heating strip - why can't I get a cooling strip?

A typical heating strip is a flexible silicone material containing a resistive heater. However, I would like the opposite - something I can wrap around my experiment and use in a similar way to the ...
0
votes
1answer
28 views

First Law of Thermodynamics and Signs

I have a question in my text book about the first Law of Thermodynamics. It gives 3 situations with the systems for each in brackets: 1) Rapidly pumping up a bicycle tyre (air in the pump) 2) ...
2
votes
1answer
34 views

Dipole moment of a single point charge

Kindly refer to the Multipole Expansion section (chapter 3) of David Griffith's Introduction to Electrodynamics. Let us first discuss about why multipole expansion is needed. As far as I understand, ...
-1
votes
0answers
12 views

How to Calculate Engine Torque from Drive Torque @ The Wheels for All wheel drive and Front wheel drive? [duplicate]

Would it be possible for someone to explain how engine torque is calculated from drive torque at the wheels and how this differs between AWD and FWD. Thanks.
2
votes
0answers
29 views

Majorara zero mode in Ising chain, not exactly zero subtlety

We know the transverse field Ising model with N sites(open boundary), can be mapped into N free fermions(there are 2N modes if including the negative energy counterparts) With property: ...
5
votes
1answer
187 views

Rotation of Spacetime $\Rightarrow$ Change in orbit/path

Along the idea of frame-dragging; Will the rotation of a black hole, which has some velocity v and angular momentum, influence its path in 3D space? I've seen the fact that depending on the ...
1
vote
0answers
19 views

Room with open door and heater : use inside boundary conditions or heat source for PDE?

I want to model the stationary temperature in a room (=square) that has one open door (=side) is otherwise perfectly insulated is heated through a (circular) heater that is placed somewhere in the ...
-1
votes
1answer
17 views

On a AC to DC adapter there are +12v wire with 24A and -12v have 0.5A. How many amp this adapter will provide in total?

I have a PSU of a pc which is 500w. I want to charge a 12v 100ah battery which need 20 amp of current. Is this psu can provide current that I have wanted? Main question is On a AC to DC adapter ...
-4
votes
0answers
30 views

Intuitive understanding of vector spaces [on hold]

I want to understand the intuitive meaning of vector spaces (Hilbert, Banach, metric, normed). I have read a lot of texts and understand the mathematical formalism given but how does it correspond to ...
2
votes
1answer
83 views

Is meters per second equivalent to seconds per meter?

I know this question is probably ridiculous, but bear with me for a moment. This thought emerged while I was converting between nm and wave numbers ($\rm cm^{-1}$). In order to prove this conversion, ...
0
votes
1answer
26 views

Spherical 'capacitor' with only one charged plate

A question I came across asks about two concentric spherical conductors where only the inner sheet is charged. The question first asks to find the capacitance of such an arrangement. The first part ...
1
vote
0answers
11 views
5
votes
1answer
142 views

why the Laughlin's wave function is an incompressible quantum state?

some comments about the meaning of an incompressible quantum liquid are posted here: Incompressible quantum liquid In the same context, the Laughlin's wave function for a filling factor of 1/3 ...
3
votes
2answers
146 views

Does all of spacetime exist?

In Brian Greene’s 2004 book, The Fabric of the Cosmos, he quotes Einstein on the meaning of time, …the distinction between past, present and future is only an illusion, however persistent. ...
1
vote
1answer
41 views

Decoupling coupled differential equations in dynamically coupled two state system

Consider the following dynamically coupled two state hamiltonian, $$H=-B\sigma_z-V(t)\sigma_x$$.Taking the eigenfunctions of $\sigma_z$ ($|+> and |- >$) as basis vectors, we have the wave ...
-2
votes
1answer
25 views

Newton's 2nd law for rotation (accelerated rolling and inertial frame of reference) [duplicate]

I need help in understanding why, in accelerated rolling, the center of mass must be at the origin of an inertial frame of reference in order for the second law to be applicable. Thanks!
4
votes
2answers
7k views

Is radioactive decay spontaneous or random?

When the count rate of a radioactive isotope is measured, the readings fluctuate. Do the fluctuations demonstrate the random nature of the decay or the spontaneous nature? (This question was asked in ...
1
vote
0answers
23 views

Scale invariance and stress energy tensor

I have seen in a paper [1] that in a quantum field theory scale invariance takes place provided the stress energy tensor is traceless. How this is true? References: "INFINITE CONFORMAL SYMMETRY IN ...
1
vote
1answer
19 views

Immersing a copper sphere into a conducting liquid that is itself in a conducting bath

Question A small copper sphere of radius a is half immersed at the surface of a poorly conducting liquid of resistivity $\rho$. The liquid is contained in a spherical copper bath of radius b, where b ...
0
votes
2answers
41 views

Difference between stiffness and damping?

I understand stiffness as the extent to which an object (e.g. a mass spring) resists deformation from an applied force, or the rigidity of an object. And I understand damping as the energy ...
1
vote
2answers
176 views

Computing Acceleration in mass and pulley system using conservation of energy

I have a question in which a multiple pulley and mass system is being analysed. I can compute accelerations and Tension without any issue using newtons second law. However I am asked to use ...

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