# Questions tagged [models]

DO NOT USE THIS TAG just because the involved physics is based on a model. All physics descriptions are inherently model-based. This tag is reserved specifically for addressing model development, validity, simplification, or other meta-model questions.

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### How to get started in Mathematical Modelling in Physics Research? [closed]

I am a beginner in Physics Research. I want to develop Theoretical/Math Models for the phenomenon I am researching on. What are the basics of Developing Theoretical Models in Physics, and How do I ...
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### Clarification for understanding matter fundamentally

I am entering my undergrad second year (so I have no formal quantum physics education) and have been stuck on conceptualizing matter at its core on a day to day basis. I've always envisioned matter as ...
1 vote
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### Breakdown of the Fermi gas model for the nucleus

One of the predictions of the Fermi gas model for the nucleus is that the most energetically favorable situation for a nucleus is to have $N=Z$, an equal number of protons and neutrons. Observing the ...
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### Finite Difference Modeling of MOSFET Device

Does anyone know of any references for MOSFET modeling done using the Finite Difference Method that they could point me to? I understand the gist of the operation, namely using Poisson's equation to ...
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### Burger equation and shock waves

Given the burger equation, $$m_{\tau} + mm_x = 0,$$ one expects to have discontinuities and thus shock waves in the case the initial conditions are smooth. For example, one may take m_0(x) = \sin(x),...
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I'm studying a model in the field of complex systems regarding the epidemic spreading. The model is the susceptible-infected model, i.e., there is a population of N subjects and each of them can ...
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### What kind of equations is needed to solve this kind of problem? [closed]

Imagine that I have the following situation, it is raining with different intensity along ($x$-coordinate) and a man is holding a bucket and is walking with varying velocity $v(x)$, how do I find the ...
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### Besides Beard and Chuang model, any prevalent models for the shape of raindrops?

In Beard and Chuang, 1987, the famous Beard and Chuang model that describes the rotational cross-sections of raindrops in their equilibrium state. My question is: Besides this model, any prevalent ...
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### Why do people say that the $\Lambda$-CDM model has six independent parameters?

The Wikipedia article on the $\Lambda$-CDM model says that the model has six "independent parameters". It also says that the model has several "fixed" parameters and several "...
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### What is the link between permittivity, thickness and optical path length (OPL) of a sample?

I am reading this paper regarding cornea phantom sensing using THz radiation. In this paper, the authors propose using a bunch of modelling and to measure a bunch of spheres of different radius of ...
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### Can the value of Limiting friction be achieved?

My teacher states that if we apply an external force just equal to the value of limiting friction, then the body will start moving. But if the external force is just equal to the maximum frictional ...
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### How precisely can change in temperatute be modeled without a thermometer?

This is mainly a gastronomical question, however, it is not exactly trivial. I'll present the setting in the form of a problem: In order to make a dessert, the recipe states that we have to "...
57 views

### Is there a way to represent whole objects in a formula? [closed]

In physics I always see formulas with variables representing properties of objects like (this is a simplified example): ...
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### Modelling of a heat exchanger [closed]

re mathematician so im so lost... Any help will be very appreciated!
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### Effects of an electrode in a microchannel flow

I am working on modeling the effects of an electrode in a microchannel flow. I am a little confused about how to model this. I have two electrodes on the boundary. Do I add the electric field effects ...
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### What is the most general and accurate real gas equation?

I've been presented in my thermodynamics course with both the ideal gas and Van der Waals state equations for the study of gases, being the latter more accurate in measurement than the first one. ...
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### Can we model the pitch up of an aircraft due to sudden application of brakes while it is rolling down an inclined using angular impulse method? [closed]

Consider an aircraft parked on an inclined plane. Due to a mistake by the pilot the brakes were released, and the wheel chocks were missing. When the plane started to roll down, the pilot applied the ...
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### General Relativity "doesn't quite work" without dark matter?

I am taking an astrophysics course, and my astro professor said that "we need to introduce dark matter because Einstein's general relativity doesn't quite work without it". I wanted to ...
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### If an equation describes some physical phenomenon is the assumption that it works in all cases? [closed]

I may be misunderstanding the general idea and the following specific example, but I was told that Dirac predicted the existence of the positron based on a formula for the motion of the electron(?) ...
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### Can anyone suggest a calculation model for estimating the location of a dropped object falling from a height?

I'm trying to find models that allow me to calculate dropped objects, specifically, a model where I can consider lateral displacement due to wind force and vary the weight and resistance force of the ...
1 vote
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### Graphical representation of an arbitrary tensor

I am interested in finding graphical models for tensors. To begin with, let's think about graphical models of tensors in 2D and 3D. If possible, I would be interested in the graphical representations ...
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### Torque profile with fixed boundary condition

I am trying to find a simple treatment of elasticity theory of a scenario where I have a thin rod attached to a disc (radius $r_0$), and the disc is held fixed at its edge. Now I apply some torque to ...
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### Equations modelling a snowboarder/skier on a jump

I am currently a highschool student elaborating an internal assessment for my mathematics AA HL course (a sort of research paper we must elaborate for the IB) and was looking into the relationship ...
1 vote
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### Is there a missing variable in the double slit experiment? [closed]

I've been reviewing the double slit experiment lately and I believe it is missing a few crucial things. Thickness of the wall is my primary focus. How could I add thickness into the equation? I'm ...
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### Optical Properties of Heavily Doped Silicon in the Visible and Near Infrared

I am looking for a model of the changes in the complex refractive index of doped Silicon based on the doping level and type in the visible and near-infrared wavelengths (400-1000 nm). I have seen ...
278 views

### Are there any laws of physics that are always true?

I understand that "laws of physics" is a bit of a misleading term since all they really are is just us applying a logical statement about observed physical phenomena in a way that allows us ...
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### What exists in the world according to the special relativity? [closed]

Before I learned about special relativity, I thought that only one 3-dimensional state of the world exists. Then, like in game of chess, in one "turn" previous state is destroyed - and the ...
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### What's the difference between observable and unobservable objects in a physical theory?

Both can help explain physical effects, but I'm looking for a rigorous definition of “observable” and “unobservable.” For example, how is the experimental evidence for the existence of particles such ...
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### What are Quantum Field Theories?

Every time I read about quantum field theories, I wrongly assume and associate the theory to the Standard Model, that is, our current theory of particles and interactions. However, it seems that the ...
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### Is the informational approach to thermodynamics generally accepted as "correct"?

This question is about the "ontology" as it were of statistical mechanics. In my limited reading of (equilibrium) statistical mechanics texts, I have encountered two viewpoints for what is &...
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### Is math really fundamental or would it not matter if physics did not depend on math? [closed]

Can you disprove this please because it's been bugging me and I don't know much about physics at all as I'm only in 10th grade. It's one of those weird thoughts but I would like confirmation to keep ...
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### Why did these algae grow like this in the pool? Are these curves the gravitational equivalents of the bell curve?

My friend sent me these pictures of a pool that has been abandoned for a long time, and we are curious about the reason behind the peculiar growth of algae in this pattern. The needle-like towers of ...
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### Near-field diffraction

I want to calculate near field diffraction loss due to the presence human blockages which are modeled as cylinders with random heights and diameters in indoor mm wave network as mentioned in " ...
1 vote
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### Nancy Cartwright's distinction [closed]

Nancy Cartwright introduced an interesting distinction in the context of her study of the history of the evolution of our understanding of superconductivity. She emphasized the distinction between ...
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### If two models generate identical predictions, must one be mathematically reducible to the other?

If two models always generate identical predictions of measurable observables given identical inputs of measurements over a given domain, must one be mathematically reducible to the other over that ...
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### What is the meaning of an imaginary part of position in Lorentz-Drude model?

Some time ago I got to know about Lorentz-Drude model, which predicts dependence of complex permittivity $\varepsilon = \varepsilon_1 + i \varepsilon_2$ from classical assumptions. In the model, ...
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### Best spacetime metric for a cylinder

I am studying a rotating cylinder model in general relativity. The interior metric is given, but I am trying to express the exterior metric. It has to be practical and describe spacetime around a ...
1 vote
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### In physical calculations, is the elimination of higher-order small quantities an approximation or a strict equality in mathematics?

Physics sometimes uses a technique called the method of differentials, which seems magical and not very systematic. This makes me unsure which variable I should take the differential of, and sometimes ...
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### Does a point mass have constant mass?

Expanding on the title, I am hoping for a little bit of insight into the philosophy of Newton's mechanics as a physical theory. My question, essentially, is does a point mass have constant mass by ...
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### In this time dilation explanation, shouldn't gravity and mass affect the example?

recently i've started "exploring" general relativity, and found this example explaining time dilation caused by velocity: The example was taken from https://en.wikipedia.org/wiki/...
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### Is there any physical situation where the electric potential is discontinuous? [duplicate]

I am wondering if the fact that "the electric potential is continuous" should not be added to the set of axioms of physics. I have never seen a problem where the potential is discontinuous, ...
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### Time scale of earthquake simulations on scaled building models

The effect of earthquakes on a building can be investigated by creating a scaled down model of the building, and simulate an earthquake on a shake table. A recording of a natural earthquake can be ...
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### What are the Equations for Climate modeling of alien planet?

I am studying complex dynamic system and I would like to analyze the climating formation of a possible alien planet considering climate as a complex system . For this I do not want to use a whole ...
1 vote
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### Is there a way to mathematically model the stress/strain graph of a material after the limit of proportionality? [closed]

I am currently working on an application that simulates physics experiements, and am struggling to find a way to model the graph after the limit of proportionality. I have constrained the simulation ...
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### Will the probability for tunnelling go completely to zero? [closed]

According to quantum mechanics, the probability for quantum tunnelling (of an object) never become completely zero, no matter how "big" is the height and the thickness of the barrier. ...
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