Model Definition and 1000 Threads

When we do the stretched rubbers he etc analogy of gravitational well, there are two differences 1) the ball moves into depression because of gravity of the earth. 2) stretched rubbersheet is physical and prevents ball from falling down while space would allow you to move anywhere as space...

Hi All. On Tuesday I have to present my research proposal for my undergrad research. I intend to model our solar system using general relativity and compare and contrast my results with observations. Attached is my paper that I had to submit to my adviser. He suggested that I talk about some...

would a gravity well resemble a angle food cake pan well traveling through a sphere? being you start outside the well. travel inward towards the core then outwards to the edge of the well again. wouldn't this also mean gravity wells would be replaced with pressure wells at the core?

Homework Statement Question a) Briefly describe the Rutherford model of the hydrogen atom and mention any inadequacies that it might have. b) Describe the Bohr model of the hydrogen atom, and indicate the significance of the quantum number 'n' in the Bohr model. Homework EquationsThe Attempt...

Hi everyone. I'm looking for a good book or some good source of informations about the stantard solar models, but i can only find compact stars stuff. Do you guys have any sugestions ?

Good afternoon. Which modifications did the Bohr model introduce into the Rutherford one to justify the Discountinuous atomic spectra, specially the one for the Hydrogen atom? Thanks

*Constraints (sorry the title got mangled) I want to model N spherical points pi in R3 with masses mi and bounding radii of ri for 1 <= i <= N. So I can write (N2-N)/2 inequality constraints: Ci,j : ||pi - pj|| - ri - rj >= 0 for unique pairs of i,j. Looking at the same problem for three...

Homework Statement I am unsure of Q3 but have posted my solutions to other parts Homework EquationsThe Attempt at a Solution 3) ok so it is clear that because the metric components are independent of ##x^i## each ##x^i## has an associated conserved quantity ##d/ds (\dot{x^i})=0##. (1) The...

Homework Statement Let us consider a fully connected Ising model with four-spin interaction in a transverse field Write the mean field Hamiltonian. Homework Equations none The Attempt at a Solution I know that the mean value of the product of two spins is equal, in the thermodynamic limit...

Homework Statement 2. Homework Equations Ohm's law and Kirchoff's voltage law The Attempt at a Solution My solution is a bit long so I will just briefly explain it. First, we find the total equivalent resistance. Since the circuit extends to infinity, it is equal to replacing the second...

I am trying to see how to derive the following inequality on page 36 in the proof of Lemma 11.3: https://arxiv.org/pdf/math/0412040.pdf I.e, of: $$\| fg \|_{Lip} \le \bigg(1+\ell \sup_{t\in T} |g'(t)|\bigg)\sup_{t\in T}|f'(t)| , \ \ supp \ f(1-g)\subset S^c$$ My thoughts about how to show...

Hamiltonian of XY model is defined by ##H=J\sum_i (\sigma_i^x \sigma_{i+1}^x+\sigma_i^y \sigma_{i+1}^y)## and because it is isotropic it is sometimes called XX model. If we do some unitary transformation, and get hamiltonian ##H=J\sum_i (\sigma_i^x \sigma_{i+1}^x-\sigma_i^y \sigma_{i+1}^y)##...

I was thinking about hall conductivity, when this question popped up. If there is a magnetic field and an electric field perpendicular to it, then a hall current is generated since the ions have larger gyro radii compared to electrons. Now this current would produce a J cross B force in the...

Homework Statement Hi, I'm just trying to derive the small-signal model of the cascode MOSFET amplifier circuit. In the lectures, we were just given the small-signal model directly. I'm trying to derive it. I have almost the exact same thing except where I put the output voltage. In the...

I'm creating a tennis game and at this point I'm trying to model ball motion. I found multiple lectures on projectiles equations of motion which seem to apply well for when ball is not moving, but they do not take into account the velocity may have at the time of impact. For example, I found a...

By fresh42's invitation, I here attach a paper which is related to the post on non-standard qm-models https://arxiv.org/pdf/cond-mat/9705290

Penrose's CCC model posits a mapping between our big bang and a future one. This is based on the idea than in the far future there will be no mass and at the big bang there was no mass. So in both cases the universe looses track of scale. I am aware that the idea of there being no mass in the...

Homework Statement I have found a differential equation that models a non-linear pendulum with air resistance, and now I have data. I've looked at the following site for guidance on how to analyse the data. It compares the motion of a damped spring, and compares it to the motion of a damped...

I just wanted to get this out of my system. I'm not talking about the main article on SM but the mathematical formulation one: https://en.wikipedia.org/wiki/Standard_Model_(mathematical_formulation) Very, very hard to find good summarized material on SM out there. It's either good coverage but...

Hello Physics Forum Users! I have an annoying situation with the Finite Heat Release Equation used to simulate combustion and expansion processes in an internal combustion engine. The equation is as follows: Nomenclature: P = Cylinder Pressure (kPa) θ = Crank Angle (Deg) k = Specific Heat...

Hello, I have found references giving the equation for an ABC model for GaN-based LEDs (see: file://icnas3.cc.ic.ac.uk/lsm16/materials-10-01233.pdf), but I am not able to find any for simple GaAs infrared LEDs (LED information: https://uk.rs-online.com/web/p/ir-leds/8108247/#). Does similar...

Hi I am going through Edx course on Introduction to Differential Equations by Paul Blanchard (BUx: Math226.1x). At one point, he is explaining the Logistic population model.$$\frac{dp}{dt} = kp\left(1- \frac{p}{N}\right) $$ After this, he says that since the right hand side does not involve t...

Hi, I am currently working on a Hybrid Rocket which uses fuel grain as 3-D printed ABS and oxidizer as N2O, but i need to calculate some basic parts such as required thrust to reach specific altitude. I want to calculate the required thrust to reach 1.5km for 10kg rocket with 7cm radius. It will...

Here is another work-in-progress 3D model that I made using blender. It's the lower half of Metal Gear REX from the 1998 video game Metal Gear Solid. https://imgur.com/a/I9zUg I can't wait to post screenshots of the finished version of it!

The Hamiltonian of the Qi, Wu, Zhang model is given by(in momentum space): ## H(\vec{k})=(sink_x) \sigma_{x}+(sink_y) \sigma_{y}+(m+cosk_x+cosk_y)\sigma_{z} ## . What is the physical meaning of each component of this Hamiltonian? Note: for the real space Hamiltonian(where maybe the analysis of...

Scenario: An average of 5 test subjects are brought into a study in subsequent months and are administered 1 monthly test for as long as they remain part of the study. The time they remain in the study is 3 months. Could someone please explain a formula or technique to sum the number of...

Why is the XY model in statistical physics called so?

This is the very first thing that I made using the 3D modeling program Blender after watching a handful of hours worth of video tutorials on youtube. https://imgur.com/gallery/b8BwM

Not the best at physics but trying to understand the standard model. So can someone please tell me if this is right or not and if not, can you explain me why? Higgs bosons reacts with everything that has mass. Electromagnetic force reacts with everything that has charge. Weak force reacts with...

This is a homework problem in a course in particle physics at Cornell University. Assume the Left Right Symmetric (LRS) model for leptons. The gauge group is GLR = SU(2)L×SU(2)R×U(1)X. The Standard Model group SU(2)L×U(1)Y has to be included in the LRS group. Namely, U(1)Y ⊂ SU(2)R×U(1)X. Find...

Homework Statement For the first question , why when the humidity increase by 1 percent , the moisture content will increase by 0.2727 percent ? Shouldn't it the moisture content will increase by 0.2727 + 0.4911 percent when the humidity increase by 1 percent ? Second question , it's clear that...

Hi; Thank you so much in advance for any help. My question about FeynArts model file, I have coupling of my model and I did arrive to insert (write) constant 4*4matrix in generic model file in Feynarts or I should write it in model file. Thanks again

Hi, I'm slightly confused with the Aguirre-gratton model, and was wondering if someone could explain using simpler terms? I have read from : http://www.preposterousuniverse.com/blog/2007/04/27/how-did-the-universe-start/ " Aguirre and Gratton have presented a proof by construction that such a...

This T-shirt I bought at a physics conference displays the following equation. It looks like the Lagrangian of the Standard Model of particle physics but I only recognise lines 1 (electroweak) and 3 (Higgs mechanism). What are lines 2 and 4 and what is/isn't included? eg. are quarks, gluons...

Hi Everybody, First post on the forum, this one's stumped me I'm afraid. I'm basically trying to model a rotary connection in an AC circuit, and I'm having a bit of trouble with it. Ideally I'd like a reasonable approximation with conventional circuit elements. Basically I've got a...

Homework Statement In the grey atmosphere radiative energy balance model, we replace the multi-layer approximation used above with still simplified but significantly more realistic model involving a continuous atmosphere with a continuously varying temperature. The variation with temperature is...

Here are screenshots of a 3D model I made using a program called Blender, of the RBMK-1000 "Chernobyl-type" nuclear reactor and reactor hall. It's still a work-in-progress and not yet finished. https://imgur.com/a/rpHnK

Hi, I have not been able to learn how a pseudo-Hermitian differs from a Hermitian model. If one has a hermitian model that satisfies all the fundamental prescriptions of quantum mechanics, a non-Hermitian would not, as it yields averages with complex values. How does a pseudo-Hermitian differ...

Homework Statement Earlier in the book it was remarked that early in the history of nuclear physics the electrically neutral mass of nuclei now attributed to neutrons was considered to arise from neutral particles composed of combinations of protons and electrons (as opposed to neutrons in...

Homework Statement I'm having some trouble with this problem as it seems my concept of the problem is completely wrong. Could someone look through my solutions and point out what I understood wrongly? Thanks in advance. Homework EquationsThe Attempt at a Solution a) 21 macrostates - this...

I'm currently studying IR but my mind is having trouble tying everything together. While I see that vibrational frequency is determined really by just reduced mass, I can see from the equation that vib equation is the same throughout energy levels and so does energy (bc that basically depends...

Homework Statement Formulate as a mixed integer programming problem but do not solve. Maximize ##x_1 + x_2## subject to ##2x_1 + 3x_2 \le 12## or {##3x_1 + 4x_2 \le 24## and ##-x_1 + x_2 \ge 1##} ##x_1, x_2 \ge 0## Homework EquationsThe Attempt at a Solution if the first constraint is met, we...

Hi guys, I am currently working on my master thesis. I am supposed to make a dynamic model for a gas system and have some trouble setting up the energy balance. I am a noob when it comes to uploading pictures, so I don't have a figure for this, but let's consider a general control volume (CV)...

The covariant derivative in standard model is given byDμ = ∂μ + igs Gaμ La + ig Wbμ Tb + ig'BμYwhere Gaμ are the eight gluon fields, Wbμ the three weak interaction bosons and Bμ the single hypercharge boson. The La's are SU(3)C generators (the 3×3 Gell-Mann matrices ½ λa for triplets, 0 for...

Hello. I think I don't understand very well the Paul Steinhardt's cyclic model of Universe(s). According to Paul Steinhardt, 2 universes get closer. Then, there's the big bounce, which products effects like a big bang. If 2 universes get closer, they have a (relative) speed ( speed is the...

Copy and paste if you want to use any of this code. Its a simple iteration of converting biomass of elk into new wolves. % example for ODE and Gillespie % one reversible reaction b1 = .033; bo = .00047; a1 = .0022; ao = .00055; Aini = 5168; Bini = 34; %% Basic ODE simulation dt = 0.01...

I am no expert on the nuances of assumptions of various formulations of Bell theorem(s), but wonder if the following model is adequate to explain the correlations without any non-local features. If this is a known, flawed, approach, a pointer to its refutation (or an explanation) would be...

Sir currently I am trying to solve a system which has 8 sites and each site can have 3 possible states(0 or 1 or 2).So the dimension of matrix is 6561*6561.The lapack works good till 3000*3000.But for larger system it fails.I have studied the dsdrv1.f example from arpack where they have solved...

Homework Statement In the attachments there is the question and its solution, it's problem 3.5. Homework EquationsThe Attempt at a Solution My question is how did they get the dimensionless Hamiltonian in both cases, and how did they explicitly calculated ##m## in both cases? I assume it's...

Dear Forumers,Given a simulink model: http://www.femm.info/Archives/contrib/images/TransientLoudspeaker/SimulinkOverview.png I would like to implement fast code for it.I have no access to matlib or simulink at all, so I tried to implement the simulation in C code. Code for the block...