Model Definition and 1000 Threads

Hello! I am taking a course on Electroweak & Strong Interactions (you could equally call it Standard Model I) and I find it absolutely fascinating! 😍 We studied how weak interactions violate parity, introduction to QCD, flavor physics (CKM matrix, CP violation, …) and neutrino physics...

Hi Everyone, can you guys please help me with the exercise attached? I knot that according to the book, van der Waals interaction is “charge fluctuations in atoms due to zero point motion.” This is correct once you understand that they are not talking about zero point motion of nuclear...

These are images of a 3D model I made of the legendary Edmund Fitzgerald, a great lakes bulk carrier ship, which famously sank in lake superior in 1975.

Made using Blender 3D, version 2.9, rendered in eevee. https://www.artstation.com/artwork/oAmVDw

Hi, I was working on a predictive linear regression model and was hoping to obtain some bounds to represent the uncertainty present in the model. Question: I suppose this boils down into two separate components: 1. What is a good measure of uncertainty from a linear regression model? MSE, or...

This Tesla Model S Owner Repairs His Own Car, because after the warranty period expires, you're on your own. Greg Furstenwerth was an early adopter of the Tesla Model S, but once the car was out of warranty he had a hard time getting the parts and service he needed. So he took on the repairs...

First of all, I'm using TensorFlow version 2.3.0 The code I'm using is the following: from tensorflow.keras.models import Sequential from tensorflow.keras.layers import Dense, Flatten, Conv2D, MaxPooling2D from tensorflow.keras.callbacks import ModelCheckpoint def get_new_model(): model =...

Do particles have air in between them in the ideal gas model? I think the answer is 'no, but I am not quite sure about the explanation. Is it because in an ideal gas model, the volume of the particles is negligible? Thank you.

I am sure that the answer will be negative, but I'm not 100% sure on how to solve the problem. My initial answer was -350 J. Please help. Thanks!

Homework Statement:: Discuss the limitation of the Explicit Finite Difference Model. Relevant Equations:: no formula Hello there, I have to discuss the limitations of using the Explicit Finite Difference model to calculate a 2D Heat Diffusion through an aluminium place, however, I really...

Assume a transformer as above, with 230V L-N, and I want to work out the L-L voltage. A phasor diagram will show me that the voltages are 120° out of phase. (230∠0°) + (230∠120°) = (230cos0 + j230sin0) + (230cos120 + j230sin120) = 230 + (-115 + j199.2) 115 + j199.2 = 230∠60 What I’m looking...

Hi, Several times I encounter the argument that there is a "problem" with the masses in the Standard Model that we try to "understand". From the one side, you have people who ask why the neutrino masses are so small, and from the other side they ask why the top quark mass is so large. The...

From an excel file I can get the probability of each energy state Εi and I saw at Wikipedia that the probability of each energy is proportional with e^−Εi/KT, from this I find the energy of every micro state. Also from the formula which I found on a paper I can get a curve like the curve...

is the concept of potential just a mathematical model

The assignment states: Pipe A takes 20 hours longer to fill swimming pool than pipe B. Together, pipe A and pipe B can fill the swimming pool in 30 hours. The assignment question I am stuck on is to write a function R(x) that models the combined rate of the two pipes in relation to the time it...

I've tried to show b) by using the sine Fourier series on ##[0,2a]##, to get ##g_k = \Sigma_{n=0}^{2a} \sqrt\frac{2}{a} Sin(q_k x)## Therefore ##\sqrt\frac{2}{a} = \frac{1}{a} \int_0^{2a} Sin(q_kx)g_k dx## These are equal therefore it is an orthonomal basis. I'm not sure if this is correct so...

Since this quesstion popped up in this thread I thought it might be better to create a new thread: https://www.physicsforums.com/threads/a-question-about-an-electrons-movement-in-a-dc-circuit.997736/ The question is the following: What kind of descriptive model could/should one use while first...

Hello, I have recorded time-domain data from an experiment. I am using a finite difference time domain algorithm to simulate the experiment. The model has been tuned to resemble the data fairly well but I'd like to be able to quantify the fit. Most of what I see online seems to be about...

Why do we exclude interband transitions in semiclassical model of electton dynamics? I mean why it is an assumption in this model?

Cosmological inflationary models are general models in the sense that they could be applied to a variety of fundamental theories. Most physicists working in inflation assume that there is only one (but yet unknown) fundamental theory which through inflation would produce multiple regions or...

This is a 3D model I made of the Mir space station.

In satellite motion around a planet, if the satellite is in orbit, it experiences only the gravitational force and its energy in orbit is constant (see 'https://openstax.org/books/university-physics-volume-1/pages/13-4-satellite-orbits-and-energy'): It's not radiating energy, is it? Its...

Hi everyone I've just completed a mechanical engineering degree, and one aspect of the classic 2DoF quarter car model that still bugs me is the representation of the tyre as a linear spring attached to the ground. Does anyone have any experience of modelling the system with the tyre spring...

Summary:: Due tight-binding model I derived the energy spectrum of the particle, showing that it comprises three energy bands E+(k), E−(k) and E0(k)=0. Now, I have to find the dispersion laws. Why do I have a flat energy band? What is its physical significance?. Also, what happens to the...

What is the relation between Wannier function and LCAO in tight-binding (TB) model? I know in TB we use LCAO but why we have an alternative approch using Wannier function? For example as said in this lecture note: But I don't understand why we use wannier function? Or in general why we use a...

I've slowly been writing a thread on octonions and particle physics, just to explain some facts in a self-contained way, with all the proofs. I don't know where this will lead. I'm certainly not presenting a theory of physics, much less advocating one. Mainly it's just fun. Octonions and...

There has been a lot of talk about the value of beauty in theoretical physics. There seems to be a lot of little things that are beautiful because they make sense, according to what we already know, like the discovery of anti-particles, and recently the Higgs. The standard model was revealed...

Quantum mechanics is often said to be equivalent with Feynman path ensemble, which "after Wick rotation" becomes Boltzmann path ensemble, also called euclidean path integrals (popular for numerical calculations), or random walk/diffusion MERW (maximal entropy random walk). But Boltzmann path...

It has been hypothesized by quantum field theory that the vacuum is not empty due to the energy time uncertainity relationship. Instead it is filled with a sea of virtual particles popping in and out of existence and renormalized to the observed value we see today in experiments like the casimir...

I'm looking for a general analytical solution to a particular ODE that comes up in neuroscience a lot. My feeling is that such a solution can't be obtained, otherwise someone would have presented it by now, but I don't have a good understanding of why it is so hard to solve. The equations as...

Does anyone know if it is possible to develop a fully analytical solution for a leaky integrate and fire neuron driven by arbitrary time-varying current? Here's what I have so far (setting as many possible constants to 0 and 1): The equations: ## \dot{V} = - V + I(t) ## and if ##V(t) = 1##...

My homework consists of trying to create a simple model for a collision. But I have trouble understanding a specific part of the assignment, namely what g-force is. I'm guessing that I'm allowed to make assumptions. But without understanding adequately the definition for g-force, I don't think...

Hey guys! Not a brain scratcher as such, just a clarification. When we talk about Bohr's postulates for his atomic model, would the Bohr-Bury scheme be involved in it? like in his postulates?

Has anyone else come across the soliton model of the action potential? https://en.wikipedia.org/wiki/Soliton_model_in_neuroscience It seems extremely non-mainstream, especially given that it presented as an alternative to the Hodgkin-Huxley model, which is undoubtedly the most successful...

If τ is the relaxation time, τ means, on average the time between two collisions for an electron moving under a constant electric field inside a metal. Now according to the assumptions of drude model, the electron acquires an additional velocity of \frac{-eEt}{m}where t is the time elapsed since...

Physicist Geoffrey Chew proposed the concept of bootstrap (related to S-matrix theory) where he denied that fundamental laws of nature existed at all, as it is indicated in a writing in his memory written by one of his collaborators ([https://www.fritjofcapra.net/in-memoriam-geoffrey-chew/])...

Title says it all. Maybe it belongs more in Astrophysics but given the title... "Beyond the Standard Model Explanations of GW190521" - - - - https://arxiv.org/abs/2009.01213 If this is for real I'm surprised it's gotten so little attention..? EDIT PS: (for my own convenience mostly) ...

Hi, Here is a basic picture of the famous electric circuit of the HH model. Can someone please tell me the anatomical locations of the connections marked in red in the cell? Thanks.

I guess the crux of the question is, where are we more likely to encounter new physics? The standard model already explains almost every experimental result, but not EVERY result. But what are some of the most important results that are either incompatible with the standard model or just...

In this paper, on quantum Ising model dynamics, they consider the Hamiltonian $$\mathcal{H} = \sum_{j < k} J_{jk} \hat{\sigma}_{j}^{z}\hat{\sigma}_{k}^{z}$$ and the correlation function $$\mathcal{G} = \langle \mathcal{T}_C(\hat{\sigma}^{a_n}_{j_n}(t_n^*)\cdot\cdot\cdot...

I have just watched a video lecture about the Tomlinson model (aka Prandtl–Tomlinson Model) which explains the friction mechanism at a nanoscale by analogy with a tip dragged by a spring. The video has prompted me to ask several questions. The spring is dragged over a corrugated substrate, as...

Summary:: Is there a primarily non-technical book covering all aspects of the Standard Model of particle physics? The Standard Model comes up a lot in YouTube videos. There must be a decent amount of public interest. I think there would be a market for a semi-technical but accessible for the...

Hi. I'm looking for recommendations of books, surveys, or lecture notes, that deal with physics beyond the standard model all in one place. The starting point is someone who already knows QFT and the SM at the level of Schwartz's book on QFT and the SM...

I thought this might be worth a read: https://iopscience.iop.org/article/10.1088/1361-6552/aa5b25/pdf

I can only find papers relating to how they've used the model but nothing about the model.

They seem to have something to do with Z or W particles, maybe, and they have something to do with mediating weak iso spin, I think, and they may be related to the Higgs field. But they don't have a box dedicated to them on the Standard Model of particle physics. Can someone tell me why this is...

This is my problem : it all starts with some very basic linear least-square to find a single parameter 'b' : Y = b X + e where X,Y are observations and 'e' is a mean-zero error term. I use it, i find 'b', done. But I need also to calculate uncertainties on 'b'. The so-called "model uncertainty"...

The RW metric reads $$ds^2 = -dt^2 + a^2(t) \Big( \frac{dr^2}{1-kr^2} + r^2 d\theta^2 + r^2 sin(\theta)^2 d\phi^2 \Big)$$ The value of k determines the model is flat/open/closed. But say if we have a model on a completely different form, with no explicit k-dependence. How would I determine if...

The dictators at physics.stackexchange want to close my post that I post here. I hope someone can help me with this question, I want to compute this by hand, without Computer algebra software, mainly because I don't know which syntax to use for Mathematica (if you know the syntax, can you give...