Computation Definition and 250 Threads

Homework Statement Homework EquationsThe Attempt at a Solution [/B] I think I understand part b) . The idea is to move the operator that annihilates to the RHS via the commutator relation. However I can't seem to get part a. I have: ## [ P^u, P^v]= \int \int \frac{1}{(2\pi)^6} d^3k d^3 k'...

I have a relatively simple design problem but my memories of thermodynamics are very rusty and I can't figure it out on my own. To make it short, I want to put a mix of solid, water and air in a 500mL pressure vessel and heat it all up to 250'C for several weeks. T and P are at room conditions...

Hello, and thanks in advance for taking a look at my question. Generally, I am trying to make a railgun force model. Since railguns depend on the magnetic field created around the rails (and the resulting Lorentz force) I need to model the magnetic field created by the current that flows...

I need to run some computations using an initial star. I could evolve one using MESA but it'd be very convenient if I could download a ready made profile/model of a star which details things like mass, dens, temp, etc, from core to surface. I've googled for a long time but I just keep getting...

Hi everyone, I am currently working on a subject that involves a lot of 4th order tensors computations including double dot product and inverse of fourth order tensors. First the definitions so that we are on the same page. What I call the double dot product is : $$ (A:B)_{ijkl} =...

A little question about the appropriateness of a certain research subject... Would it be useful to make a study of the computational effectiveness of equivalent codes written with Matlab, Mathematica, R Code, Julia, Python, etc. in a set of typical computational engineering problems like...

Hello, I'm having some trouble with my octave coding and would appreciate any input on where the issue lies. The coding is as follows: age = [0:1:100]; %this is the age matrix, represented by a time = [0:1:100]; %this is the time matrix...

Homework Statement Hi, I am trying to understand the attached: I know that if two functions have zeros and poles at the same point and of the same order then they differ only by a multiplicative constant, so that is fine, as both have a double zero at ##z=w_j/2## and a double pole at...

I'm having some problems understanding why my computation deviates from solutions. I thank in advance to anyone who can give me some tips where I've gone wrong. Homework Statement Compute real power on resistors ## R_1 ## and ## R_2 ## and reactive power on inductor ## L ##. Circuit is powered...

Hi, I am computing the anomalous dimension of a mass operator in the MSbar scheme, but i have a doubt. The following is the solution of an exercise given by a professor but i don't understand a passage. I have computed the counterterm ##\delta## and i have the formula $$\gamma=-\mu...

If input is 2: call int calculate(string exp) function. This function will return the computation of a string expression (exp). For example: calculate(“54321+222”) will return 54543 calculate(“120*20”) will return 2400 calculate(“235/3”) will return 78 calculate(“356-32”) will return 324My code...

Would it be possible to make a quantum computer with fluidic logic (https://en.m.wikipedia.org/wiki/Fluidics), using a superfluid, like liquid Helium-4, as the the "current"?

I realize this question may not have an obvious answer, but I am curious: I am using Gaussian and Eisenstein integer domains for geometry research. The Gaussian integers can be described using pairs of rational integers (referring to the real and imaginary dimensions of the complex plane). And...

So I'm currently a senior undergraduate nuclear engineer at a respected university and I've been considering getting my Ph.D for a while now. I'm having difficulty deciding on a specific research area, however. I'd like my research, optimally, to be applicable outside the nuclear sector as well...

Hello! (Wave) Could you suggest me other topics for a presentation in Theory of Computation other than the ones that were suggested by Evgeny Makarov to mathmari in this post: http://mathhelpboards.com/chat-room-9/computability-14368.html#post67959 ? Is for example the topic Algorithmic...

If I am performing simple arithmetic on numbers that extend 12 decimal places i.g; 12.1234567891011 +11.1234567891011 and this calculation occurs 1000+ times, will calculation i.g; 12.123+11.123 speed up computation time if so how much and how do you arrive at this?

Hi there, Apologize in advance if this is not the correct place to post my query. I've been googling didn't get it or maybe my input search parameter is not sufficient or irrelevant. I am recently doing my graduate in physics and my inclination towards computational physics makes me to do my...

I'm a mechanical engineering from Universidad Tecnologica de Bolivar(Cartagena Colombia) . Right know studying Computational mechanic material(more specific: Isogeometric analysis). I'm really newbie in this and hope than some on your can help me because is just the beginning of something more...

I have access to a nanoparticle that no one has done a computational study on. I want to know specifically what kind of computational studies i can do on it. e.g Ab initio calculations and m.d. simulations. I want to know what properties could be computed and how to go about it.

Say you wanted to heat up your room. You could choose between an electric heater that outputs 500W or a PC that draws 500W. In both cases, the amount your room would heat up by would be the same, but the second case is much more advantageous because the computer can process information before...

Hello! (Wave) According to the book of Michael Sipser: Introduction to the Theory of Computation we have the following: Could you explain to me why after having read the first 0, we can go to state $q_3$ ? I have drawn the tree and I find also an other result after having read the...

EXPLORING THE POSSIBILITY OF PERFORMING COMPUTATIONS WITH PLAYING CARDS I was listening to an interview with John Conway yesterday and the conversation turned to his "Game of Life". Conway mentioned that Life can be configured in such a way that it can perform arbitrary computations. This got...

I have to perform the following computation by hand to get a number within two decimal places: ##\displaystyle (120)(\frac{54.30}{194.79})##. The answer is 33.45, but how can I do this by hand?

Hi, I've done quite a bit of scientific computation at work, mainly related to molecular QM and dynamics of hyperelastic bodies... I've used C++ to write the code for those applications. I also do some other simulations at home in my free time, just for fun. My home laptop isn't exactly the...

NOTE: For the answers to all these questions, I'd like an explanation (or a reference to a book or internet page) of how the answer has been derived. This question can be presumed to be for the general eigenproblem in which [ K ] & [ M ] are Hermitian matrices, with [ M ] also being positive...

Hi, I have a FORTRAN code with an array called Chi that I want to run an inverse FT on. I have defined two spaces X and K which each consist of 3 vectors running across my physical verse and inverse space. My code (If it works??) is extremely slow and inefficient (see below). What is the best...

Hi, If I consider for instance N non interacting particles in a box, I can compute the energy spectrum quantum mechanically, and thus the number of (quantum) microstates corresponding to a total energy between $E_0$ and $E_0 + \delta E$. In the limit of large quantum numbers, the result is well...

Problem I would like to determine the combined standard measurement uncertainty for a mean mass ##\bar{m}## computed from a mean volume ##\bar{V}## and a constant density ##\rho## with $$\bar{m} = \bar{V} \, \rho.$$ I know the mean volume ##\bar{V}##, volume standard deviation ##\sigma_V##...

1st year, heading power side, should I do a unit in stats or "computational explorations"? My 2nd semester must needs consist of a foundations of EE unit, a foundations of ME unit, I've picked a unit for building IT systems (since a lot of power side these days involves SCADA and smart grids...

Hello everyone, Still working on my reading of Weinberg's Lecture notes on QM book. At one point, the following integral $$\int d^3 xd^3 x' V(\vec{x~}) V(\vec{x'}) / |\vec{x~} - \vec{x'}|^2$$ has to be computed in the case where ##V(r) = -e^{-r/R}/r##. This reminds me of retarded potentials...

I have a function of 2 variables [f(x,y)] where if there was an ellipse in the x-y plane, all values of the function are 1 inside the ellipse and 0 outside. I can plot this function as a surface in 3d where it looks like an elevated ellipse hovering over an elliptical hole in a sheet. My...

Hi, my problem: following the adiabatic theorem we get an equation for the coefficients: \dot{a}_{m}=-a_{m} \langle{\psi_{m}} | \dot{\psi}_{m}\rangle - \sum_{n \neq m} \frac{\langle \psi_{m} | \dot{H}| \psi_{m}\rangle}{E_{n}-E_{m}} exp(\int_ 0^t E_{n}(t')-E_{m}(t') \, dt') we start in an...

Consider the following integral that comes out of a loop calculation along with some fermionic propagators (e.g virtual one loop correction to a ##p \gamma^* \rightarrow p'## process such as in DIS): $$ \int \frac{\text{d}^d l}{l^2 (l-p)^2 (p+q-l)^2} \text{Tr}(\not p \gamma^{\nu} (\not p + \not...

I am trying to compute the density of argon given the following conditions: T = 7000 K P = 21331 Pa For typical gases, I do not believe the ideal gas law would hold for such a high temp&low pressure regime, but since Argon is largely non-reactive, do you guys think using the ideal gas law would...

Assume the following set of instructions: 1. i = 0 2. if i < n, goto line 6 3. if A [ i ] = = x, goto line 7 4. i++ 5. goto line 2 6. return false 7. return true Assume that line i take Ci time, where Ci is a constant. The worst case total time of running this block of code can be calculated...

Homework Statement I'm using python to calculate the age of the universe, by working out the distmodulus for a set of galaxys (using the V and I bands) then working out the distance in parsecs and then hubbles constant etc... I keep getting values that are 10s of magnitudes out which I assume...

The following is taken from page 5 of Peskin and Schroeder. It talks about the computation of ##\mathcal{M}## for the annihilation reaction ##e^{+}e^{-}\rightarrow \mu^{+}\mu^{-}##. Even for this simplest of QED processes, the exact expression for ##\mathcal{M}## is not known. Actually this...

Good day. I do not know much about cosmology, rather computer science, but the following theoretical question bothers me a little. Some scientists, like Tegmark, Wolfram, Zuse or Fredkin, support the idea that the Universe might be just computation. Computable means that something can be...

This seems to be a crucial detail that I just glossed over, but when finding the inertia tensor of an object, is the origin always situated at the object centre of mass? For example: In the link (http://hepweb.ucsd.edu/ph110b/110b_notes/node26.html ), is it necessary to do the integral from...

So I've delved into programming, and gotten experienced with the fundamentals. However, the more I learn, the more I question the central object of comp. science, computation, and its foundation. According to Wikipedia, "Computation is any type of calculation that follows a well-defined model...

I am going to be applying to grad schools in the coming months, and plan to apply to many schools. I'm looking for programs in quantum computation, quantum information, quantum optics, etc... (related research often falls under many different names). These programs generally are categorized in...

Hey there PF'ers. I'm looking for a nifty book or site on Quantum logic and Computation. The sort of book like that would cover digital logic - jumps over all the explanations of underlying working and goes straight to logic and computation. I know it's important, but I have done courses in...

And what are the methods? This was stimulated by This question could be rephrased as "use the method for finding square roots you were taught in school to find √7 to 6 decimal places". If you were taught at school. If you were not taught at school you were luckier than me, I was. It has had...

I was hitting against a wall for the last hours. I am not able to obtain the 1/2 terms in the eq. 5 of this paper and left all in terms of only ##N_i## and ##\overline{N_i}##,neither. Anyone could give me a tip? http://arxiv.org/pdf/hep-ph/0210271v2.pdf Thank you in advance.

Homework Statement Prove: In R3if a and b are orthogonal vectors, then for every nonzero vector u, we have proja(projbu)=0 Homework Equations I know the dot product of a and b is zero The Attempt at a Solution Based on the definition of projection I eventually got to (ab) in the numerator...

Hello, Thanks to all of you for the help that you provide so that we can move forward. I need help about the computation of the Kretschmann scalar without using software, I face to some difficulties on its computation for instance in the case of Schwarzschild metric. Could some one help me with...

Hello! (Wave) The prime number $p=67$ is given. Show that $g=2$ is a generator of the group $\mathbb{Z}_p^{\star}$. Compute the discrete logarithm of $y=3$ as for the base $g$ with Shanks-algorithm. Compute the same discrete logarithm using the Pohlig–Hellman algorithm. That's what I...

Hello everyone,Has anybody already did the computations to reach equations 10.41, 10.44 and 10.45 in Peskin's book? It would be very much appreciated and useful.

Homework Statement Homework Equations A=LU, U^-1 * L^-1= A^-1 , U^-1 * L^-1 * U^-1 * L^-1 = A^-2, The Attempt at a Solution I used MATLAB and the relations: U^-1 * L^-1= A^-1 , U^-1 * L^-1 * U^-1 * L^-1 = A^-2, to find a solution I found U^-1*L^-1 , let =B...

Homework Statement Water is poured into a container that has a leak. The mass m of the water is given as a function of time t by m = 4.9t.8 - 3.0t + 21, with t ≥ 0, m in grams, and t in seconds.(a) At what time is the water mass greatest, and (b) what is that greatest mass? What is the rate of...