Models Definition and 369 Threads

Ever since Newton, determinism - i.e. the concept that the prior state of a system determines the next state of the system - has become an integral part of science, in particular of physics. This is particularly because Newton invented a mathematization of the concept of change: the calculus; in...

ρο/a4 ρο/a3 k Λ Βig Bang Big Crunch Polynomial Expansion Exponential Expansion x 0 x 0 >0 x +1 x +1 x 0 <0 x -1 x -1 >0...

Hi all, I've been looking at de Broglie-Bohm theory and more recent attempts at Bohm-like models that are relativistic and attempt to reproduce QFT. What I'm not clear on (non-expert) is how the vacuum is modeled in these cases? If we have a set of infinite quantum harmonic oscillators...

https://arxiv.org/pdf/1903.00009.pdf "We present an explicit construction of O(1015) globally consistent string compactifications that realize the exact chiral spectrum of the Standard Model of particle physics with gauge coupling unification in the context of F-theory. Utilizing the power of...

Homework Statement I have made a number of measurements of current against optical power for a given laser. As shown below, my measurements only go up to 8 amps. I am trying to use the data to predict the output power at 9 amps. In the ideal case, the behaviour is expected to be linear, but...

I am doing some research into atmospheric energy harvesting. To design a proper feasibility experiment, I need to establish some theoretical baselines. I see a lot of values for the field strength for example, tossed about from various papers. However, there does not seem to be a standard...

I have been studying primordial black hole formation through inflation for a while and I was curious to know how the parameters in an inflation model are determined such that they are consistent with CMB constraints. In my literature reviews, there are quite a few models that exhibit an...

Homework Statement Homework Equations ##\dot{x} = Ax + Bu## - Input Function ##y = Cx + Du## - Output Function The Attempt at a Solution I'm having trouble with the output functions specifically .. In a.) the correct solution for the output is: \begin{align} & y_1 = x_1 \\ & y_2 = x_2 \\ &...

I'm a speculative fiction writer and playwright, a retired archirect with a master of architecture degree in theory, and a theater producer, director, and acting improvisor. I'm currently working on a TV series of 169 episodes exploring life in a contemporary parallel universe very much like...

I see this happening a lot and have done this in my analysis as well. But it doesn't seem too intuitive to me as to why it works. So if we fit a linear regression, and the residual vs fitted plots are curved, we tweak the input variables to get a random residual vs fitted plot. But we have used...

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?

Arguments can often be presented using a discrete model on the assumption that continuous variables can be accommodated by taking the limit as the resolution is increased. I would have thought that this would be just fine in QM where functions are continuous. But maybe mathematicians here can...

According to the article in Astronomy Magazine June 2018, the satellite galaxies of Centaurus A are rotating in the same direction in a relatively thin plane, vs randomly distributed if there is a dark matter halo/sphere surrounding large galaxies. Any thoughts on this new finding? I've only...

Hi everyone. I'm new to the forum so sorry if the title or the "sub-topic" is wrong, and I tried my best not to break the posting guidelines, if I did, let me know. (First of all, I want to clarify what's my stance on all of this, I'm not a proponent of these ideas; in fact, I'm always sceptical...

Homework Statement A plane starts its descent from height ##y =h## at ##x = -L## to land at ##(0,0)##. Choose ##a, b, c, d## so its landing path ##y =ax^3 + bx^2 + cx + d## is "smooth". With ##\frac{\mathrm {d}x}{\mathrm {d}t} = V =##constant, find ##\frac{\mathrm {d}y}{\mathrm {d}t}## and...

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

Hello, I am not sure if this question is better suited to the mathematics section, but I thought it would be easier to explain the problem here. In Schneider, Kochanek and Wambsganss's "Gravitational Lensing: Strong Weak and Micro" pages 279-280, they derive a relation for determining the...

Hi, are there any models known in QM where the wavefunctions do not have to be infinitely differentiable, and thus can exist in other spaces than the Hilbert space? I assume Banach spaces allow elements that are not infinitely differentiable as subsets. Can therefore certain phenomena in QM be...

I wonder if anyone can please help / point me to some info on how to solve this problem. I posted the same question on another website, and so far there is no conclusive answer. I have some pharmacokinetic data for a molecule that was administered in rat, first IV (intra-venously), then PO...

Dear All I know that my question is not so related to this, but i will appreciate any answer. Why could we have 2 different models for the universe ( one expanding, collapsing...) although both are receiving the same experimental data... I need to write an essay about this topic. I have ideas...

Nowadays we hear a lot about AI deep learning artificial neural networks. People speak about simulations of billions of neurons and even much more synapses. However, as far as I understand it, the artificial neurons used in these simulations are extremely simplified models of real biological...

Homework Statement I am practicing diode circuit analysis for an ideal diode model and constant voltage drop model.I have an initial circuit shown here: Which I then redraw to look like this: I want to make sure my process in redrawing this was correct. When I attempt to get current through...

I have once again come across a smoke detector which requires not only a specific type of battery (9V alkaline) but also a specific model (in this case Duracell MN1604) to be used. I had a similar problem with a CO detector about a year ago (which came with a list of about 10 models that should...

Preface There are lots of times in physics when we use approximations of a more accurate or fundamental physics theory because it is easier to work with. For example, in quantum chromodynamics (QCD) lots of calculations are done using the Schwinger-Dyson equations rather than the actual...

Ref: http://www.spaceref.com/news/viewpr.html?pid=51416 I would be very interested to see comments from knowledgeable people about this. My impression is that this is one more example of a need to remain at least somewhat skeptical about theoretical models that have not yet been validated by...

This may be of special interest to mathematicians, physicists, and anyone who is skeptical of the various "social sciences." The book is The End of Theory: Financial Crises, the Failure of Economics, and the Sweep of Human Interaction, by Richard Bookstaber; 2017, Princeton U. Press. I've only...

Homework Statement The Pacific halibut fishery has been modeled by the differential equation. \displaystyle\dfrac{dy}{dt}=ky\left(1-\dfrac{y}{M} \right) where y(t) is the biomass (the total mass of the members of the population) in kilograms at time t (measured in years), the carrying...

I know that early oscillating models of the universe fail due to the second law of thermodynamics. One thing that I am unclear about is since as far as i know the laws of physics break down in a singularity can the second law of thermodynamics break down also? When I see comments to the...

Hi there, I am wondering if you have any suggestions how to draw these simple engineering models? Thank you in advance.

Hi All, When a query is made in SQL , it is transcribed into FOL in the back end , and, if the transcription is a wff , the models, if any, are returned as the answer to the query. I have an idea of how the transcription works for basic statements, but, does anyone know the actual "...

I'm opening this thread for discussion on the latest debate over inflationary cosmology as outlined over at scientific american the original article on inflation was Scientific American published an article by Ijjas, Steinhardt and Loeb https://www.cfa.harvard.edu/~loeb/sciam3.pdf then a...

Reading some of the critics and defenders of inflation in various papers, one thing I note they have in common is that both seem to agree the plateau models of inflation are favoured by Planck. According to one of the critics of inflation "The plateau-like potentials selected by Planck2013 are...

Open access news article from Science magazine news. I found this interesting, but it is really beyond my ability to provide a short explanation.

I am aware that according to the Standard Model of Particle Physics, fundamental particles such as electrons and quarks are treated as point-like particles. However, if fundamental particles are indeed 0-dimentional points with no spatial extent, it creates problems (i.e. fundamental particles...

I have extensively searched the internet but failed to find any exhaustive literature on the different collapse models of quantum mechanics.It would be really helpful if someone who knows can guide me on some exhaustive resources for the same.

So it was mentioned that one should ignore data driven models because this could inflate the type 1 error as a result of overfitting. So the model should be decided even before looking at the data set. But at the same time, other sources say we should look at the scatterplot matrix to determine...

Hello, I was wondering if two models show the same S matrix by a direct relation between their parameters, does that necessarily mean that both models are exactly equivalent? My idea is that this is true, but would like to know about a solid argument about it if possible, thank you!

Hi :) im wondering if there is a video where a calculated model and the same situation in reality gets compared ? :) e.g. water drop, or something crashing with a certain speed :) thanks for any help :)

Although it is definitely not simple, there are many reasons to consider that baryon number can be violated, for example: - while baryogenesis there was created more matter than antimatter, - hypothetical Hawking radiation can finally turn any matter (mainly baryons) into massless radiation...

So on the left is a circuit which shows a voltage source and 2 coupled inductors in a parallel magnetic circuit shown on the right (transformer with a parallel core). Can someone tell me if I am modelling it correctly with the following equations? Rc1,Rc2,Rc3 are the reluctance of each branch of...

Hi guys, Based on what I know about the status of modern cosmology the question whether the universe is infinite or finite in extent is still open. Are there any plausible models in which the universe is finite and closed, despite the curvature being close to flat? Thanks in advance.

Specifically:

Hello, I am doing a non-linear analysis in ANSYS. I have curve for the strain,stress curve for the material in tension, however, in the problem I'm working on I'm compressing the material. Does anyone know, if ANSYS just mirrors the material curve about origo as I have not given it data for...

In his seminal paper on Special Relativity: On the Electrodynamics of Moving Bodies, Einstein derives a formula for the Relativistic Doppler effect. See this section: § 7. Theory of Doppler's Principle and of AberrationThe formula is: In this Wiki article, the same formula is derived. The...

Hi all, I fairly basic question about spin foam models in loop quantum gravity. I just want to verify that spin foams represent effectively represent all of spacetime (in a quantum form), and that the idea is that general relativity can be obtained in the classical limit? Not sure if that's...

Hi, i am studying Simplified Models for the search of Dark Matter at colliders. In particular there are 2 different kind of models that i am studying that are s-channel and t-channel models. Now, there is something that i don't understand related to the mono-jet process. Here is a paper that...

I want to make my own set of molecular models with balls representing atoms and links representing bonds. Anyone knows of a good software to do this? As for the physical model, what bond angles, bond lengths and ball sizes should I create? I could for example leave atoms as round balls and...

from https://www.physicsforums.com/threads/world-made-up-of-2nd-3rd-gen-particles.883560/#post-5555878 quoting ohwilleke Have you come across this paper in peer reviewed Physical Review D... http://www.sciencedirect.com/science/article/pii/0370269379906671 or...

Hi everyone, I got the basic ideas quintessence (minimally coupled) and derived the KG equation for scalar field: $$ \ddot{\phi} + 3 H \dot{\phi} + \frac{\partial V(\phi)}{\partial \phi} = 0 $$ where $$H=\frac{\dot{a}}{a}$$ and $\phi$ is the scalar field. There are various models depending...

I know that there are several models of the real numbers, some where the Continuum Hypothesis holds, others where it does not. I would like to understand why the usual definition of the reals, limits of Cauchy sequences of rational numbers under the usual absolute value norm, isn't one of these...