What is Model: Definition and 1000 Discussions

A model is an informative representation of an object, person or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin modulus, a measure.
Representational models can be broadly divided into the concrete (e.g. physical form) and the abstract (e.g. behavioural patterns, especially as expressed in mathematical form). Of particular importance in the modern context, conceptual models are central to philosophy of science, as almost every scientific theory effectively embeds some kind of model of the physical or human sphere.
In commerce, a model might instead reference a specific version or configuration of a product offering, rather than functioning as a representation of something else.
In taxonomic settings (e.g. biology, architecture, art) a model is sometimes a particular instance of a set of related entities (species, built structures, artistic compositions) chosen as a convenient reference point around which to build discourse; such a model is almost always chosen to typify some central tendency of the group, exemplify the group's defining characteristic, or reify the group's historical lineage.
Kinds of models include:

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  1. I

    I Drude Model Permittivity Formula - e^iwt or e^(-iwt)?

    I've been having a sign problem while deriving the permittivity formula using Drude model, and I found out that the problem came from the fact that complex field vectors are expressed with e-iwt, not eiwt, thus producing (-iwt) term when differentiated...
  2. S

    Sherrigton-Kirkpatrick model for spin glass question

    I'm having some trouble understanding some of the steps done in the uploaded paper. I'ts the 1975 paper by Sherrington where they explain the SK model for spin glass. Homework Statement and Homework Equations[/B] Up to equation 5 I understand all steps. I used J_0 = J_0 / N and J^2 = J^2 /...
  3. J

    A Quark Parton Model: Explaining Inelastic Scattering

    Hi, I've been studying the quark parton model recently and all seems fine at first. However, there's just one thing bugging me right now. So in the quark parton model it is assumed that inelastic lepton-hadron scattering can be explained by elastic lepton-hadron scattering, but how can it...
  4. M

    A Can Wormholes Be Integrated into the Standard Model of Physics?

    Apparently the Internet hasn't noticed this paper yet: http://arxiv.org/abs/1807.04726 Traversable wormholes in four dimensions Juan Maldacena, Alexey Milekhin, Fedor Popov (Submitted on 12 Jul 2018) We present a wormhole solution in four dimensions. It is a solution of an Einstein Maxwell...
  5. L

    A The k direction in a k.p model ?

    I am trying to do some calculation based on a k.p model of GaN proposed by S. Chuang [Phys. Rev. B, 54, 2491]. It is a 8 by 8 Kane model with basis functions: The 8 by 8 Hamiltonian contain first order of k is where ##{k_ \pm } = {k_x} \pm i{k_y}## the reciprocal space and high symmetry...
  6. M

    Modified Poisson–Nernst–Planck model

    hello everyone can anyone know how can i add the modified Poisson–Nernst–Planck model accounting for the Stern layer to simulate the transient double layer dynamics
  7. W

    A How Do Generalized Linear Models Extend Beyond Standard Linear Regression?

    Hi, Just wanted to see if I understood the meaning of Generalized Linear Models: In the case of Standard ( "Non-generalized") Linear models, a dependent variable y is a linear function of a dependent variable x. In a Generalized Linear Model (GLM), a dependent variable y is linear in some...
  8. caterina magro

    Automotive How to model a CNG pressure regulator?

    I need a help with 1D simulation of a CNG pressure regulator. I have to model this valve in a software called GT power/GT suite. The model has a inlet, ball poppet, piston with spring, outlet and a pipe for balancing the valve. Maybe someone who has experience about modeling this kind of...
  9. entropy1

    I Can Quantum Mechanics Be Both Probabilistic and Deterministic?

    If we use a probabilistic model of QM, is there still room for determinism? If we don't have knowledge of the exact outcomes, can there still be underlying determinism in such a model? I am aware there are probabilistic and deterministic models available for QM. Does that mean QM could be...
  10. mastrofoffi

    Weird fluctuations in Ising model

    Not 100% sure this thread belongs in this section, sorry if it's out of place. I was trying to run a simulation of a 2D Ising model; i thought everything was going fine until I started to look at the numerical results and I noticed that I get some wild fluctuations in my results; as an example...
  11. W

    B Who drew the first model of the atom?

    Does anybody know who first drew (not just described but actually drew, even roughly) a model of the atom like the one below, and when: I'd appreciate it if anybody can point me to an evidence.
  12. P

    I A model of what makes up the physical world

    Hi there I am a high school science teacher and I want to present my senior classes with a model of the fundamentals of the physical world to serve as a mind map for us when we reach each topic. I have started by creating the one below and then realized I may have left off momentum...is momentum...
  13. Nikhil N

    Model developed from performance curves are dynamic models?

    I am trying to model a real heat exchanger in simulink. I don't have the geometry data. But I have UA curve with me. If I have developed the model with UA curve, will it be dynamic in nature?
  14. S

    MHB Can Categorical Variables be Used in Multiple Regression Models?

    Hello, I am trying to do the following regression model; Y = N + T + F + NT + NF + NTF + error Y= Grams of seed N= Number of fruit T= Type of fruit (2 types, alpha) F= Field number (3) I have tried putting this in MiniTab and I can't get this set up correctly. Assistant> Regression>...
  15. A

    A Multiverse reduction in the new Hawking/Hertog model?

    Hawking and Hertog's new paper "A Smooth Exit from Eternal Inflation?" does away with the infinite multiverse of Hawking's previous theory and proposes a cosmology that predicts "a simpler and finite universe". But I can't figure out the extent of this reduction to a "simpler and finite"...
  16. I

    I Data Model of Kepler's Second Law of Planetary Motion

    Hello, I am completing a research project for differential equations class. I am to derive Kepler's three laws and then compare the results of the derivation with real-world data. For Kepler's second law (a planet sweeps out an equal area in an equal time), I was hoping to find orbital data for...
  17. F

    A Solving Almheriri's Dilaton-Gravity Model in AdS##_2##

    I am going through Almheriri's article about " Models of AdS##_2## and I am stuck on a derivation. I think they make some kind of assumption which I don't understand. What I am trying to do, is to compute the equation of motion by varying the action with respect to the metric. Unfortunately I...
  18. A

    B Einstein's Gravity Model: Explaining Its Creation

    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...
  19. BiGyElLoWhAt

    Other Research Proposal For Senior thesis - GR Solar System Model

    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...
  20. F

    Stoner-Wohlfarth model, remanent magnetization

    Homework Statement " Plot remanent magnetization versus the sample angle for the sample. Derive an equation for the remanent magnetization using the definition of a hysteresis loop and Stoner-Wohlfarth model. " ##H## magnetic field ##K_u## anisotropy constant ##M_s## saturation magnetization...
  21. A

    I Gravity well model going through a sphere

    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?
  22. T

    Rutherford model of atom and Bohr model

    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...
  23. Leonardo Machado

    I Standard Solar Model: Learn About Its Complexity

    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 ?
  24. J

    Bohr Model Modifications into the Rutherford Model

    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
  25. fermipasta

    I How to model and resolve a static non-interpenetration constraint

    *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...
  26. binbagsss

    Cosmological model, geodesics question

    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...
  27. A

    Four-spin interactions the Ising model

    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...
  28. T

    Find the equivalent model of an infinite ladder circuit

    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...
  29. A

    MHB Derivation of an inequality from the paper “A CLT For A Band Matrix Model” by Anderson's and Zeitoun

    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...
  30. L

    A The Hamiltonian of the XY model -- when is it called the XX model?

    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)##...
  31. chandrahas

    B Confused about the Drude model

    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...
  32. C

    Cascode Amplifier Small Signal Model

    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...
  33. M

    Equations to model tennis ball motion

    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...
  34. A

    Single Sheet Tester COMSOL Model

    Hi, I'm trying to study single sheet testers. Anyone could provide with a sample model on comsol for me to get started with? Any help is greatly appreciated.
  35. M

    MATLAB Suggestions for a non-linear fit model in Matlab

    Good afternoon, I have a problem which I haven't solved yet, regarding a non-linear fit to a set of experimental data. I tried to solve it in Matlab, which I handle a little bit. I have a sensor, which has been designed to have 4 different filters in front of it. By making a sweep with the...
  36. SemM

    A What are some recommended books on non-standard quantum mechanical models?

    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
  37. W

    I Mass in the early universe and the CCC model

    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...
  38. Q

    A Susceptibilites for the Anderson Impurity Model

    My question is a rather general one about susceptibilities but specific answers for the Anderson Impurity Model are also appreciated. In this paper https://arxiv.org/abs/1101.2840 (was also published in the Journal of Physics: Condensed Matter...
  39. O

    How to model a non-linear pendulum with air resistance?

    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...
  40. diegzumillo

    This wikipedia article on the standard model is really good

    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...
  41. Jason Louison

    Engine Finite Heat Release Model (With Heat Transfer) Help

    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...
  42. H

    I ABC model for GaAs infrared LED

    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...
  43. I

    I A question regarding Logistic population model

    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...
  44. U

    How can I calculate the required thrust for my model rocket design?

    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...
  45. E

    Another work-in-progress 3D model of mine

    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!
  46. J

    A Physical meaning of terms in the Qi, Wu, Zhang model

    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...
  47. B

    MHB Formula to use instead of model

    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...
  48. Demystifier

    I Where does the name of XY model come from?

    Why is the XY model in statistical physics called so?
  49. E

    How Did My First 3D Model Turn Out After Hours of Blender Tutorials?

    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
  50. heavybuilder

    I Standard Model (Forces interacting with Matter)

    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...
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