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:
Is any of the conjectures in:
http://arxiv.org/pdf/hep-th/9610043v3.pdf
have been proven/disproven? what has been left still open?
I am thinking of reading this article sometime in the future, hope it's digestable (but first need to finish my studies of QFT and GR.)
Hey everyone,
I just made an account because I have a problem concerning angular momentum and precession.
In the picture below you see the vectors l1 and l2 that make up total orbital angular momentum L precess around L. I can get my head around why that is the case. The same for s1 and s2...
Homework Statement
Hi. I'm in high school physics, and as I'm only 2 months in, I still don't know much. We launched a model rocket as an experiment and I need to find the thrust after adding 100g of mass to the rocket's body.
The engine is an Estes A8-3. My teacher told me that its thrust is...
Homework Statement
The Hamiltonian of the 1D Ising model without a magnetic field, is defined via: $$\mathcal H = − \sum_{ i=1}^N K\sigma_i \sigma_{i+1},$$ where ##K ≥ 0## and ##\sigma_i## are the Ising spins (i.e. ##\sigma_i= \pm 1##).
A) Set up a decimation procedure with decimation...
Homework Statement
The 3 state Potts model is defined by $$-\beta \mathcal H = J \sum_{r,r'} (3 \delta_{\sigma(r), \sigma(r')} - 1) + h\sum_r \delta_{\sigma(r),1},$$ with J > 0 to encourage neighbouring Potts spins to have same value and h orienting field. The spin like variables can take...
I am working on a thesis, but new to programming.
What is the best and easy to use program that I can use for the work:
Measurement and analysis of elastic scattering of alpha–particle and light heavy ion scattering using nucleon-nucleon interaction
http://phys.org/news/2015-07-cosmology-standard.html
The most popular candidate for the elusive particles that give the Universe extra mass is Cold Dark Matter (CDM). CDM particles are thought to move slowly compared to the speed of light and interact very weakly with electromagnetic radiation...
I've been discussing this elsewhere recently. In my opinion Purcell's explanation in section 5.9 doesn't actually explain why an electron moves in a circular or helical fashion in a magnetic field:
However this length-contraction explanation has been around for so long that's it's...
Homework Statement
Consider the below network of spins, the spins numbered on the nodes of the diagram. The spins interact via the following Hamiltonian ##\mathcal H = \sum_{\langle i j \rangle} \sigma_i \sigma_j##, where the sum ##\langle i j \rangle## is over nearest neighbours and ##\sigma_i...
Hey guys the Idea of simulating the DSE with a program caught my interest but I just had a few questions regarding the DSE
Is there a function that models the probability of finding an electron at a certain point ONCE It's BEEN FIRED FROM AN ELECTRON GUN? like an amplitude function squared or...
Homework Statement
Over the last ~100 years, the average solar constant has increased by ~ 0.1 W/m2.
How much would the Earth’s temperature change simply due to this increase in the solar constant?
Homework Equations
[L * (1 – a)] / [4 * e * sigma]) 1/4 = Tground
L is the incoming solar...
A check my work question...
Homework Statement
Louis de Broglie tried to explain Bohr’s hydrogen atom electron orbits as being circles of just the
right circumference such that an electron of the Bohr energy going around the circle will
interfere constructively with itself. This seems to...
When reading about GUTs you often come across the 'Standard Model decomposition' of the representations of a given gauge group. ie. you get the Standard Model gauge quantum numbers arranged between some brackets. For example, here are a few SM decompositions of the SU(5) representations...
For low values of n, Bohr's model fails to reproduce the value of the square of angular momentum, and the repulsion angles
But Bohr model is basically a planar model... so the question should be, if we solve the hydrogen atom potential in a 2D equation, is it still different? The eigenvalues of...
Homework Statement
given one each of u types of candy, two each of v types of candy, and three each of of w types of candy, find a generating function for the number of ways to select r candies.
The Attempt at a Solution
I am not sure if I understand this correctly, but this is what I came...
Homework Statement
Homework EquationsThe Attempt at a Solution
Hello,
I am trying to construct the model, but I don't know how to incorporate 3 steps. I tried making 3 step blocks, but the input for the transfer function will only take one line. Then I tried to use one step block and make a...
http://www.iop.kiev.ua/~obraun/fk-intro.htm#model
Question? Why this model is discreet? As far as I see particles can have any position?
Why then is written in the text then In the continuum-limit approximation we come to the sine-Gordon (SG) equation?
From the semi-classical Bohr model of the hydrogen atom the velocity of the electron in a certain orbit can be determined. With these velocities the electron's relativistic masses can be determined. With E=mc2 the energy levels are in agreement with those from the Bohr model. I know Bohr's model...
Homework Statement
My problem is with the last line of the derivation. Usually, we take the rate of change of momentum (force) to be change of momentum divided by the impact time. But this slide of pp showed that the traveling time of the particle in the box is used but not the impact time. Why...
Celeste: A new model for cataloging the universe
The roots of tradition run deep in astronomy. From Galileo and Copernicus to Hubble and Hawking, scientists and philosophers have been pondering the mysteries of the universe for centuries, scanning the sky with methods and models that, for the...
Its been suggested that the metastibility of the Higgs may lead to a new cyclic cosmology to replace inflation.
http://arxiv.org/abs/1307.8106
Can anyone give a layman's guide to how this works and they propose to solve the problems of the big bang that inflation is supposed to solve:
flatness...
[Mentor's Note: Thread Moved from EE Forum]
This link has the picture, for some reason it wasnt showing in this post. http://i.imgur.com/TYlb32t.jpg
Here is my problem, I am supposed to use this circuit and solve for Av and Rin. My problem is that I have solved for Av but I can't solve for Rin...
Homework Statement
can liquid helium at 4k (.1 nanometers interatomic spacing) be modeled by non spreading wave packets?
Homework Equations
1/(√2π)∫∞-∞ei(kx-wt)Φ(k)dk
W(k) was Taylor expanded to a quadratic term Δpx2/(2mħ)
The book then sas for a non expanding wave packet:
|t| << mħ/Δpx2...
Problem:
In analogy to the Bohr Theory of the hydrogen atom, develop a quantum theory of Earth satellites, obtaining expressions for the orbit radius (r) and the energy (E) in terms of the quantum number (n) and the other relevant parameters. A satellite of mass 1000 kg is in a circular orbit of...
Hi everyone,
I want to build a car-model which should be good enough to study under-steer/over-steer and test various safety algorithms like ABS, TCS, ESP. Initially I made a quarter car model, here I could implement simple ABS,TCS. Quarter car model supports only longitudinal dynamics and is...
I was looking at building a fpv plane. I was wondering if anyone could help me with the basic equations i would need for motor sizing etc. Just how I would go about finding power required. Looking at about a loaded weight of about 5kg wingspan 2.5-3m. Not sure of speed maybe around 40-70kph.
Homework Statement
There is a diagram in a book that shows a water pump sending water down a hill that then rotates a water wheel. The water reaches the bottom reservoir and is then carried back up the hill by the pump to start the cycle again.
Q1. Use this model to describe an ammeter...
Whats the best value of ##Ω_k## (Considering Planck 2015 results).I asked best value cause If you think our universe can be also hyperbolic so ##Ω_k## can be different then 1.
I remember the relationship between ##Ω_k## and k is
##Ω_k=-k/a(t)h^2## or some sort of something like that.k is zero I...
Hi there.
I'm having a hard time understanding the precise meaning of the so called "cosmological principle":
My understanding of the general Big-Bang model is that far enough back in time the observable universe came down to something very small (compared to now), very dense, very hot... Ok, i...
Homework Statement
1) vs = 1 mV. Find v1, v2, v3 and vL
2) Model the three-stage cascaded amplifier by a single voltage amplifier model. What are the values of Ri , Avo, and Ro?
Diagram:
Homework EquationsThe Attempt at a Solution
1) v1 = 0.909 mV
v2 = 9 mV
v3 = 818 mV
vl =...
Now after applying and removal magnetic field H=0 there will be residual magnetic domain in XYZ directions
Is the Heisenberg Model at very low temperature express about the energy of the system with higher accuracy than Ising Model in the previous case ?
and at high temperature is the Ising...
hi,
i want to derive a model of digital control valve. i don't have physical valve with me. still i have to develop such a simulator which can behave the same as the digital control valve.
the working concept of digital control valve is little bit different than normal control valve.
here is...
1.In Abelian higgs model,we can come to the results that the gauge bosons acquire mass, implying the photons also acquire mass in this model;however,photons are massless in reality.How to explain this dilemma?
2.What does U(1) mean in this model?Does it correspond to some coservation laws,or...
From a recent thread:
Is this true of gluons? Doesn't the color charge invert under CPT? (For example, a red-antigreen gluon's antiparticle would be a green-antired antigluon.)
Hi! I'm working on something that could potentially be pretty big, maybe even huge, but I am in need of some consultation and data to work out various details in effort to buildup the framework needed for my theories.
Bear with me though... a lot of the questions I'm going to ask may not be...
Hi
I m studying modelling the viscoelastic passive properties of vascular walls and there is question!
Why does Maxwell andKelvin-Voigt fail to represent a solid?
and also
what steps are required from a numerical point of implementation point of view , are required to turn an elastic model...
In this paper (http://science.uniserve.edu.au/school/curric/stage6/phys/stw2002/sefton.pdf) the author describes the transfer of energy in an electrical circuit as follows:
"To explain energy transfer we need to look at what is happening outside the wires. As a consequence of the surface...
Hi I am Ken. Nice to meet you. I would like to get some info on this synchronizing module. It has a 3 phase lamp for synchronizing an alternator. Any knows what's the theory behind that flashing lamp? what if the lamp blink very fast or blinking slow? the reason is frequency is out of phase but...
Not according to this paper. arXiv:1507.08279 [pdf, ps, other]
A Test of Cosmological Models using high-z Measurements of H(z)
Fulvio Melia, Thomas M. McClintock
Comments: 22 pages, 1 figure, 1 table. Accepted for publication in the Astronomical Journal
Subjects: Cosmology and Nongalactic...
The supposed discovery of the Higgs three years ago was widely celebrated. Nobel prizes were handed out and the mystery of the origin of mass is now explained. But does the Higgs actually explain mass at all?
When thinking about the Higgs, I think it's best to ask these questions first:
1...
Hi all,
I am new to the forum. I have a BS in Chemistry (1984). So I remember a little quantum mechanics. I am trying to wrap my head around cosmology. I started studying GR on my own about a year ago. It took me almost that long to understand tensors. This invariably lead me to start reading...
Just started the study Exotic Hadrons (like mixing of Charmonium states with tetraquarks etc.) and got confused with quenched & unquenched quark model.
What are the major differences between these two models? What key factors I should keep in mind doing calculations with these models...
Here's the main problem. I'll like a function of distance with respect to time which moves the planets in accordance to Kepler's law: planets in orbit travel equal area in equal time. I use a blender, a 3D app that allows for path programming.
What is the "consensus" status of the existence of a lattice standard model? These two sets of notes don't seem to be in agreement.
Wiese's 2009 notes http://www.itp.uni-hannover.de/saalburg/Lectures/wiese.pdf say "Thanks to a recent breakthrough in lattice gauge theory, the standard model is...
Homework Statement
I am trying to solve the model analitically just for 2 sites to have a comparison between computational results.
The problem is my professor keeps saying that the result should be a singlet ground state and a triplet of excited states, but when I compute it explicitally I...
Hi,
Just to let you know my level of knowledge/ability, I studied a degree that included some dynamics, but that was nearly 15 years ago, so I'm rusty. I'm a games programmer, and I tend to understand code (or things that can be translated into code) more easily than hardcore maths equations...
More than 300 years ago Galileo Galilei began to revise the geocentric model and he defended the heliocentrism model, now that still use the geocentric model and helps to much, time (time, day, month and year are based on geocentric model), geometry (Euclid), math, the same system of...