Models Definition and 400 Threads

What is meant by "Early atomic models predicted...noble gas...stable" Hello, I am troubled by the following statement "Early models of atomic structure predicted that atoms and ions with noble gas electron arrangements should be stable" Is this referring to the Niels Bohr model or am I...

As an understanding exercise in my general relativity course my professor recommended proving to ourselves that all Robertson-Walker models are conformally flat. However, I am unsure of how to approach such a proof. Thanks in advance for any help.

Spice Models -- LM5111 & LM5112 Hello Everyone, I am looking Spice model for the MOSFET Gate Drivers (LM5111 & LM5112). If anyone have this models please forward to me.

If we were to assume that in a Robertson-Walker model that the cosmological constant was less than zero, would this imply that at a finite time in the future the universe would undergo a "big crunch"? More importantly, would this imply the scale factor a(t) is equal to zero at that time?

Homework Statement I will use an example to showcase my confusion: Suppose a person watches show A 2/3 of the time, show B 1/2 of the time, and both show A and show B 1/3 of the time. For a randomly selected day, what is the probability that the person watches only show A? For a randomly...

The normalized wave function for a particle in a 1D box in which the potential energy is zero between x= 0 and x= L and infinite anywhere else is normalized wave function = sqrt(2/L)*sin(npix/L) What is the probability that the particle will be found between x= L/4 and x= L/2 if the...

hey everyone... i am working on an assignment of cosmological models and beginning and ending of the universe but unable to find something that is compact and describe it all.. can anyone help me in making of this assignment please

For a general family of dynamic models, xk+1=f(xk), oscillation can occur; for example, the function xk+1=xn2-1 experiences oscillation under the starting value 0: (x2=x12-1=x2=02-1→x2=-1→x3=x22-1=x3=-12-1→x3=0) This type of oscillation must be capable of detection before actually pluggin...

Say we have 2 models: ln(y) = \beta_0 + \beta_1 x_1 + \cdots + \beta_nx_n with a known R^2 and y = \beta_0 + \beta_1 x_1 + \cdots + \beta_nx_n with a known R^2 Now I know that we can not compare the R^2's from these 2 models to determine goodness-of-fit and I am also aware of how we can...

Does anybody know what is the status of supersymmetric inflation model after latest results of LHC concerning SUSY? Have some models been excluded? or do you know some review papers talk about that issue?

Homework Statement Prove that (\mathbb{R}, <) and (\mathbb{R} \backslash \{0\}, <) are elementary equivalent using the fact that there exist countable models (A, <_0) and (B, <_1) which are elementary equivalent with (\mathbb{R}, <) and (\mathbb{R} \backslash \{0\}, <) respectively...

Hi As I understand it there are several attmepts to explain the low entropy configuration of the universe at the big bang. Is seems to me the choices on the table that I am aware of are a mutliverse as in the Caroll/Chen model . A cyclic universe as in the CCC model or some hybrid of the two...

where can i get Solidworks models of spur gears? I have Solidworks student edition, and it doesn't include the toolbox that you can use to create gears. thanks

An interesting and well presented new paper by Kumar and Xu: "Observational constraints on a cosmological model with variable equation of state parameters for matter and dark energy" http://arxiv.org/abs/1207.5582 The idea of a variable equation of state for matter and dark energy is not...

Dear All, Appreciate if you can guide me on understanding the ultimate pressure of vacuum pump. I have two models for review. One has ultimate pressure of 1 x 10^-4Torr the other has 2 x 10^-3Torr. From this can it be said that the vacuum capability of the first pump (1 x 10^-4)...

Hi, I was going through the concept of R parity in SUSY. In the case of SUSY we do not have Baryon and Lepton number conservation instead we have R parity conservation defined by, R-parity= (-1)^2s+3B+L which is required for the proton to be stable. But it has been found that...

I have been acquiring some nice molecular models of graphene, buckyballs, and things like the model below. http://www.indigo.com/images/product/172.jpg One thing I have not been able to find are crystal models with the different orientations like face-centered cubic, body-centered cubic...

This might seem like a naive question from someone who doesn't know a whole lot about economics/government: Do governments have 'unified' computer models of the countries they govern, including for example energy generation, agriculture, transport etc.. A bit like simcity or civilisation games...

I have a question as to the actual nature of cyclic models of the universe (e.g. Roger Penrose's Conformal Cyclic Cosmology or the Ekpyrotic universe) - essentially where the universe has no beginning or end it simply goes through cycles eternally in both time directions. So in these situations...

Must all models of ZFC (in a standard formulation) be at least countable? Why I think this: there are countably many instances of Replacement, and so, if a model is to satisfy Replacement, it must have at least countably many satisfactions of it. Does my question only apply to first-order...

I have some questions about this paper: http://arxiv.org/abs/1102.1994v2 The author computes the entropy of the classical simulator using the Shannon entropy, then computes the entropy of the quantum simulator using von Neumann entropy and gets a smaller number, thus concluding that quantum...

Hi, First of all i apologies if this topic already exists I was wonder how the particle model of light and wave model of light compare in regards to energy distribution, amplitude, and frequency? I am having a hard time wrapping my head around this. I have a decient understanding of the...

Weih's data: what "ad hoc" explanations do local and non-local models give? From the thread on Nick Herbert's proof: harrylin: The more I become aware about the tricky details and the impressive experimental attempts to disprove "local realism", the more I am impressed by - to borrow some...

From http://www.lsbu.ac.uk/water/models.html, I see that are many models of water that can "explain" one or some properties of water but no model is accurate enough to explain all the properties of water. From what I understand, all models assume classical mechanics interactions...

3 generation is required for anomaly cancellation, then the 4th generation seems redundant. But there are still papers about the 4th generation, what is the reason? Thanks

Homework Statement I'm working on a project to find evolution equations for a cosmological model, where the following propagations equations are known, \dot{\mu}=-\Theta\mu \dot{\Theta}=-\frac{1}{3}\Theta^{2}-2\sigma^{2}-\frac{1}{2}\mu...

Does anyone know of a COMPLETE derivation of the Hubbard Model and then the Heisenberg model from it. What I mean by complete is pedagogical including all (or at least most) steps. Books like Assa Auerbach's and Altland and Simons are worthless for these kind of things (in fact IMHO those...

Hello everyone. I'm trying to do a homework in digital integrated electronics class and feel like I can finish it only if I had a good set of notes. I have problems like comparing the input capacitance of a Mosfet to a wire of certain length, getting RC time loss in a wire, power...

Inflaton Field and Bounce Models In traditional inflation, there is a field known as the inflaton which a boson of the same name. Hybrid models of inflation , if I've understood correrctly(?) have a field to start inflation and a field to stop it. However recent work on bounce mdoels such as in...

This seemed like the least inappropriate place for this. Feel free to move it if I am wrong. Generally speaking, two computational models are equivalent if they recognize the same class of languages. In the case of models that can run indefinitely, we also have the problem of decidability...

Hi guys, I am currently writing my dissertation on Graphene and I am investigateing how graphene remains stable, contradicting existing well established theory which states 2D materials cannot exist independently. With the main area of investigation looking at possible lattice distortions...

I'm halfway through the Selfish Gene, and was intrigued by his talk of strategies. Are there any good books that talk about this development in human behavior?

At another thread under Special and General Relativity the following question was asked: "Why isn't stellar aberration considered to be a one way measurement of c? If the angle of aberration (θ-θ0) is -20.5 arc seconds and the Earth's orbital speed is 29.79 Kilometers/second normal to the...

As far as I have seen, all physical models begin with space, and then put matter that live in space and modify it somehow. Basically the models works fine and describe reality farily well. But at some point they arrive to problems, as infinite curvatures, that prevents them to be unified. It...

I know the default library of LTspice don't have vacuum tube model. Does anyone know where I can get one. If not, any other free spice program have vacuum tube models? The only one I find so far is: http://www.duncanamps.com/technical/ltspice.html I tried to follow the instruction and...

There's a new paper dealing with constraint algebra and Gupta-Bleuler quantization in LQG and SF models. http://arxiv.org/abs/1012.1738 Complex Ashtekar variables and reality conditions for Holst's action Authors: Wolfgang Wieland (Submitted on 8 Dec 2010) Abstract: From the Holst action...

I'm guessing if Quantum Mechanics get modified to allow for physical collapse, the Schrodinger equation is modified. But whatever has already verified Quantum Mechanics thus far, the new theory needs to account for those results but, I would assume, make different predictions in other areas that...

Homework Statement I only need help with problem 16 but included problem 15 because it is referenced in problem 16. 16. Suppose that the growth-rate parameter k = 0.3 and the carrrying capacity N = 2500 in the logistic population model of Excercise 15. Suppose p(0) = 2500. (a) If 100...

Hello all, I'm an amateur interested in nuclear structure. I'm interested in the (by now) age old questions of "Why is alpha radiation so much more prevalent than simple neutron or proton emission?" and "Why aren't nuclear isomers like Tantalum a lot more common or identified?" and especially...

Hi, I was wondering what you guys thought of these models. Is the model on plank's length correct? Have you seen these types of models before (especially model C + D)? If so, do you have a link to something like it online? Also I am wondering how I can include 'ENERGY' and 'C' (velocity?)...

Hi, I have currently been thinking about laser-plasma interaction and I have a simple model in mind. I am going to look for a cylindrically symmetric solution of a cylindrically symmetric laser beam (of radius R) hits a initially charge neutral plasma creating an electron beam in the plasma...

Hi, if anyone can help on this issue it is much abliged... Homework Statement Here are the model parameters... VTH0 (VTH NMOS) = 0.7 to get everything even... U0 (NMOS un) = 533 cm^2 / V sec or 533000000 um^2 / V sec t0x = 1.41 * 10^-8 m or 0.0141 um eox = 3.97 * 8.85 aF/um or...

To my intuition, I find more easy to believe that the universe is infinitely old and the big bag was just one of an infinite number of similar events in a larger universe, rather then the universe had a beginning. However, after watching many documentaries, and reading a lot of popular...

I will be entering university in an aerospace engineering program next year but I want to get a head start on it right now. What I mean by that is start building basic rockets and planes, or even more basic than that, I don't know. Why I am here is to ask for guidance on where to start. I...

Hello. I have three questions that I would like to ask.1. Could someone provide me with a resource containing examples of arbitrary parameters in theoretical physics. E.g. a modern example, yet to be varified, is dark energy. A historical example, one which has since been discredited, is the...

Are physics laws (even the laws) mathematical models of reality? Or they describe reality as it is? Are those laws just models, like for example a population's growth mathematical model (just an example that I remembered)? A maths teacher told me that in physics everything are...

Hi everyone, I'm trying to solve a problem concerning steady state and dynamic models of chemical reactor. I attached the problem statement for better understanding. Please disregard part (a). Here's what I have come up with so far: For part (b) I have the following From Mass Conservation...

Question 1: What is the status of string random matrix models (~ triangulated random surfaces) with c>1? In my limited search, I have just come across a few papers by Frank Ferrari (in 2000-2002) on this. But, they applied, if I understand correctly, to a few cases with some specific kind of...

Does anybody know about a comprehensive list of cosmological models and their properties? E.g. FRW, dS, AdS, ... Goedelspacetime, ... with metrics g, Christoffel symbols, Riemann tensors, Ricci, Ricci scalar, Kretschmann scalar, ... Tom

Hi, I am interested in grand unification with extra dimensions. Especially the case when extra dimensions are broken by orbifolding. Now I am trying to understand how the Goldstonebosons appear in the spectrum of a theory with global (for example SU(N)) symmetry. From the...