Model Definition and 1000 Threads

This is just a quick alert regarding a paper today https://arxiv.org/abs/2005.03048 Exceptional Unification of Families and Forces Alfredo Aranda, Francisco J. de Anda, Stephen F. King [Submitted on 6 May 2020] This work considers the remarkable suggestion that the three families of quarks and...

I just want to confirm something. You need about 13.6 eV of energy to ionize a hydrogen atom in the ground state. Can the atom absorb a photon with 15 eV of energy? I think it can. This would free the electron, and the freed electron would move off with a kinetic energy of 15 minus 13.6 eV...

Good afternoon, I have developed a Vector Control for a PMSM motor in Simulink using Simscape Electrical but my motor is not spinning. I have tried applying various speed values but nothing happens. I am applying a step signal from 0 to 300 but the motor speed still doesn't move. My error...

Entanglement's non-locality ('spooky action at a distance') depends on the instantaneous collapse at all points in space of the entangled particles' common wave function. The Many Worlds model has no wave function collapse. Does it also have no entanglement?

As seen in the video above, ten years ago Stephen Wolfram teased a computational physics program which he simply called 'Physics'; some of this work was outlined in his magnum opus "A New Kind of Science". A few days ago he has finally given a huge update of this in his blog...

Sometimes I hear particle physicists refer to left/right chiral electrons as different particles that are 'mixed' by the mass term. Maybe I misunderstood entirely, but if there is even a handwavy sense in which this is the case, clarifications would be appreciated. In high energy collisions...

I was reading an introductory text on nuclear models and came across the Fermi Gas model. I understand that the depth of the potential well of the proton should be less than the depth of the potential well of the neutron due to the Coulombic repulsion between the protons. But I did not...

I am trying to derive the adjoint / tangent linear model matrix for this partial differential equation, but cannot follow the book's steps as I do not know the math. This technique will be used to solve another homework question. Rather than posting the homework question, I would like to...

I'm considering a dynamical model of the scenario of a disease spreading across the population, modelling the number of cases, and there's a mathematical puzzle which I'd like to solve. It's kinda different from the S-I-R model, and its also a crude model. First, we consider two numbers, NT...

$$H=-J\sum_{i=1}^{N-1}\sigma_i\sigma_{i+1}$$ There is no external magnetic field, so the Hamiltonian is different than normal, and the spins $\sigma_i$ can be -1, 0, or 1. The boundary conditions are non-periodic (the chain just ends with the Nth spin) $$Z=e^{-\beta H}$$...

A bit over two years ago I began using Blender on a more regular basis for doing 3-D modeling. One of the first models I did was of an AT-AT from the Star Wars movies. This is the result: In the time since, I've honed my skills some, learned a bit more about Blender, and picked up a couple...

Hello, I have faced a weird problem and would really appreciate any comments. Assume a 2D model e.g. an axisymmetric model, meshed with quad, linear, and reduced integration elements. As you now if a model contains contact, we will get "CSHEAR1" and "CSHEAR2" in outputs. Assuming that the...

I'm trying to dynamically model the scenario of a disease spreading across the population, modelling the number of cases, and I would love to hear your feedback. It's kinda different from the S-I-R model, and its also a crude model. First, we consider two numbers, NT and NA. NT is the total...

I was trying to put together a basic mathematical model for the Coronavirus and happened to stumble across the predator prey model; if ##x## is the number of humans and ##y## is the number of Covid-19 viruses, then $$\frac{dx}{dt} = ax-bxy$$ and $$\frac{dy}{dt} = cxy - dy$$ I took the reciprocal...

I was discussing a problem related to Einstein's universe model. As we all know its an unstable equilibrium. So a small fluctuation in the density would result in an either expanding or contracting universe. However, I read that "There are static and stable solutions in Newtonian gravity...

Hey there, I was looking at the Higgs sector of the standard model, particularly its coupling to the fermions: ##\mathscr{L}_{ yukawa }=-\sum _{ a,b=1 }^{ 3 }{ \left( { Y }_{ ab }^{ u }{ \bar { Q } }_{ a }{ \hat { \varepsilon } }_{ 2 }{ H }^{ \dagger }{ u }_{ b }+{ Y }_{ ab }^{ d }{ \bar { Q }...

OK, this is more on history of astronomy than anything else. I hope someone has an insight on how they were thinking of things back then. The Ptolemaic model of the Solar system, i.e. the Geocentric model, placed Venus inside the sun's orbit around the earth. And to account for the retrograde...

The question is taken from An Introduction to Modern Astrophysics by Carroll and Ostlie. I did manage to do the entire question and plot the relevant graphs but I just want to to investigate a bit more. For example I want to look at how the graph would like in the case of the Sun. I don't know...

Hey all! I am trying to understand the terms in the source-side of the k-epsilon transport equations. My only reference on this so far has been the wikipedia article (in my defense, it's not in Landau! the gospel has forsaken me :cry:). If you have a reference that goes into gory detail on the...

So far, I have implemented the code below, using Java Priority Queues and Maps. I tried to identify each customer by the time they came in (ranging from 360 and onwards) and their grades. However, this is my first time using priority queues and maps, and I am not very sure if I'm doing things...

I just came across a 2016 paper [1] that claims to have computed reasonably accurate masses for hadrons using what it calls a "rotating lepton model" and "the relativistic Newton equation". An earlier 2001 paper by two of the same authors [2] appears to be the first introduction of the general...

Young Galaxy Comes to the Rescue of an Old Theory The Steady State Theory of the universe has taken on a new lease of life with the discovery in 2014 of galaxy DDO 68, a dwarf galaxy 39 million light years away which, based on its structure, appearance and composition, appears to be relatively...

Hi everyone, even before addressing the following points I have a serious issue in understandig the text of the Exercise.My idea was to model this system with a lattice gas. Given that each site can host 2 atoms I have 3 possibilities for each site: I'll call'em ##S_{11} S_{00}## and ##...

I have to solve a problem related with an 'invented' (non-real) MOSFET working in its saturation region (amplifier). I have solved all the questions, but I'm unable to get the last one. Basically, I need to determine the output resistance of the amplifier as a function of other given 4...

I have never seen ray model of light being considered for radio waves, or waves of larger wavelengths. I have a feeling that this model does not apply to them. Am I right?

We say that principal quantum number tells us the average distance from the nucleus, so the sub shells of some principal quantum number say 3 has 3 sub Shells 0,1,2 and in 3p sub shell their will probability of finding the electron near the nucleus which doesn't mean electron will find in region...

The standard answer: “In GR, only average density matters.” That is what Friedmann’s equations (1) say—mathematically—but he does not derive that conclusion. He starts with it. Friedmann does not start with a messy, real-world model of the universe, one that has fractured into galaxy clusters...

If I put a slab of some material whose refractive index is \mu and width is D, in front of slits in Young's Double Slit model, then In the figure you can see that I have placed the slab just after the slits. So, when rays going to come out of the slab they will bend away from...

I wanted to know what is understood as the dispersive approximation (or limit) in the context of the Jaynes-Cummings model for one mode of the field.

This took roughly two months to complete from start to finish. Link to imgur album so that the full-size photos can be viewed. Rendered in 4K.

Can a Bernoulli or Timoshenko model be reasonable for a crane arm, on ships? Yes, the arm might have a truss element, yes there is a hydraulic force to lift the arm (or cables). But to some extent, can one model the crane arm as one of a simple beam (either Timoshenko or Bernoulli -- and...

Just a curious question, is there a limit within the standard model on how many fundamental forces there can be? I have some familiarity with particle physics/QFT(not quite mastery obviously otherwise Id probably be able to answer this myself) and the thought popped in my head when reading about...

Here is an interactive 360 degree panoramic photo of a 3D computer model I made of the RBMK-1000 nuclear reactor central hall. The refueling crane is a work-in-progress. https://www.artstation.com/artwork/A9BAJm

5 links (thus 6 frames) and corresponding theta, alpha, d and a values are all given. However, I'm not sure how to start coding the DH parameters to derive a forward kinematics model. I know that I'll have to use matrix operators, but do I just put in the values of the 4 factors mentioned above...

Hi all, I have trouble understanding some ideas relating to the Debye model. In my text (Oxford Solid State Basics by Steven Simon, page 11), it was stated that Debye wrote the following expression ⟨E⟩=3∑→kℏω(→k) [nB(βℏω(→k))+12] What was not stated was the meaning of this expression. The only...

Hi, I'm working on a project for a thermal fluids design class in which a theoretical Thorium reactor is to be designed and modeled, and I'm a little bit at a loss for how to start analyzing the problem. I know the system will have 4 fluid systems: an enriched FLiBe system connected via HX to...

Hi, I've been given a homework to do based on 2D Ising model. Ive already read plenty of articles bout 2d ising model but I'm not fairly certain about some things. I got to do a chart similar to the one I attached. Correct me if I am wrong, but on the Y axis, I have to put average of...

Consider the pseudoscalar and vector meson family, as well as the baryon J = 1/2 family and baryon J = 3/2 family. Within each multiplet, for each particle state write down its complete set of quantum numbers, its mass, and its quark state content. Furthermore, for each multiplet draw the (Y...

I am using the derivative of momentum (dp/dt) with Newton’s 3rd Law with the gravitational force of Earth. F - [Force of gravity on rocket] = dp/dt F - (G * m_e * m_r / r2 ) = v * dm/dt + ma F = Force created by fuel (at time t) G = Gravitational Constant m_e = Mass of Earth m_r = Mass of...

Here is a 3D model (blender 2.8) I created of the Chesapeake And Ohio Allegheny 1601 steam locomotive, which remains today the largest locomotive ever built.

[Moderator's note: Spun off from previous thread due to topic/level change.] Which current model? Doesn't "spatially infinite" imply Euclidean flatness which as far as I'm aware of requires ##\Omega = 1##? The theories of inflation don't predict that. They predict a value for ##\Omega## which...

I know that we use quantum mechanic and wave function to calculate probability of finding electrons but is there anything valid about bohr model that we still use it?

I have a single technical question regarding a statement on page 7 of the paper "Dynamical quantum correlations of Ising models on an arbitrary lattice and their resilience to decoherence". The paper up until page 7 defines a general correlation function ##\mathcal{G}## of a basic quantum Ising...

So I was trying to learn how to build a mathematical model of an oscillating system. The system and FBD is shown below. I just got confused why I got a different value of k from both x force and torsional equilibrium equation? Am I missing something?

According to the semiclassical approximation, in response to a constant electric field I would get a periodic motion of the electron, like this: The sinusoidal type function is the velocity, while the function that goes to infinity is the effective mass. Thus I was wondering, since ##v## also...

My naive attempt to expand the log was##log(k2+A2−λ)=log[(k2−λ)(1+A2(k2−λ))]=log(k2−λ)+log(1+A2(k2−λ))≈log(k2−λ)+A2(k2−λ)##but it did not help me so far since the second term vanishes. Can someone point me to the right direction?

Hello, I am having trouble understanding the two friction force terms from the ball rolling on page 4 of this physical model: http://www.dewtronics.com/tutorials/roulette/documents/Roulette_Physik.pdf What is the reason for the cos\theta term ? I think the frame of reference is made up of the...

Here is a 3D model I made of a nuclear reactor and reactor core.

I am watching a show about the Standard Model and The Theory of Everything (which of course we do not have right now) and the lecturer mentioned gravity is not part of the Standard Model. Yet other books include it. What is the general consensus? Thanks Bill

Usually, critical phenomena can be categorized in some kind of universality class which determines the critical exponent. A typical example is the class of the Ising model; adding a next-nearest-neighbour hopping term does not change the critical behavior. The typical explanation is that the...