What is Computing: Definition and 730 Discussions

Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both hardware and software. It has scientific, engineering, mathematical, technological and social aspects. Major computing disciplines include computer engineering, computer science, cybersecurity, data science, information systems, information technology and software engineering.

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  1. Physics Monkey

    Sanity check: Kitaev's quantum computing book

    I was flipping through Kitaev's quantum computing book today and noticed something really strange. I thought it might be fun to post it here and figure out what's going on. See...
  2. Astronuc

    Computational Physics and Advanced Computing in Nuclear Engineering

    We occasionally get questions related to codes and computational methods. There have been considerable advances in computational methods and computational systems in the field of nuclear energy and nuclear engineering. This thread serves to address previous developments and follow current...
  3. O

    Computing arc length in Poincare disk model of hyperbolic space

    I am reading Thurston's book on the Geometry and Topology of 3-manifolds, and he describes the metric in the Poincare disk model of hyperbolic space as follows: ... the following formula for the hyperbolic metric ds^2 as a function of the Euclidean metric x^2: ds^2 = \frac{4}{(1-r^2)^2} dx^2...
  4. A

    Why this relation is true when computing the Gaussian integral?

    \int_0^\infty e^{-x^2}dx \int_0^\infty e^{-y^2}dy = \int_0^\infty \int_0^\infty e^{-(x^2+y^2)} dxdy Under what conditions we could do the same for other functions? I don't get how Poisson (or Euler, or Gauss, whoever that did this for the first time) realized that this is true. It looks...
  5. J

    Many questions about qubit (quantum computing)

    Hello! I am new here and I will try my best to clarify my questions and not violate the forum rules. Just for the record, I am not particularly good at understanding equation-saturated explanations because I am not an expert. However, I did a lot of searching and I still don't understand...
  6. H

    Calculating Riemann Curvature Tensor: Faster Methods?

    I've been trying to calculate the Riemann Curvature Tensor for a certain manifold in 3-dimensional Euclidean Space using Christoffel Symbols of the second kind, and so far everything has gone well however... It is extremely tedious and takes a very long time; there is also a high probability...
  7. D

    Computing competitive equilibrium( plus consumption rivalry)

    Homework Statement Consider two agents (Pascal and Friedman) in a pure exchange economy with two goods and no free disposal. Pascal has a preference relation give by the utility function $$u^P(x_1^P,x_2^P)=a\ln (x_1^P)+(1-a)\ln(x_2^P-bx_2^F)$$ while Friedman's preferences are...
  8. T

    Computing irradiance at a point

    I'm having trobule trying to work out the solution to a quite simple radiometry problem I've found in the book Physically Based Rendering. The problem is this one a) Compute the irradiance at a point due to a unit-radius disk h units directly above its normal with constant outgoing radiance...
  9. Y

    Computing a surface integral with polar coordinates

    Homework Statement Show that ##\iint_{S}(x^2 + y^2)d\sigma = \frac{9\pi}{4}## where ##S = \{(x,y,z): x > 0, y > 0, 3 > z > 0, z^2 = 3(x^2 + y^2)\}## Homework Equations ##\iint_{S}f(x,y,z)d\sigma = \iint_{R}f(r(x,y))\sqrt{[r_x(x,y)]^2 + [r_y(x,y)]^2 + 1}## where ##r : R → ℝ^3, R \in ℝ^2##...
  10. F

    MATLAB Computing Integral with Gauss-Chebyshev Quadrature in MATLAB

    Hello, anyone knows where y can find a program to compute the integral ∫ ( from -1 to 1) f(x)/ √(1-x^2) using the Gauss-Chebyshev quadrature, on matlab? Thanks!
  11. R

    Computing Curvature: 2D Plane & Axi-Symmetric Surfaces

    I'm having a really hard time working with non-standard expressions for the curvature. This deals with two expressions for the curvature, one for a 2D plane curve, and the other for an axi-symmetric surface in 3D. The plane curve Suppose we have a plane curve given by x = h(y) for both x...
  12. I

    Is there a quantum computing model that allows you to add different states?

    I want to know if a quantum computing model exists where you can prepare two different states on n qubits and interfere (i.e. add) them together. For example, for two qubits, consider the states (|00> + |01>)/√2 and -(|00> + |10>)/√2 (both pretty easy to prepare in most quantum computing...
  13. O

    Understanding the Ideal Class Group of Q(√-17)

    I have a pretty urgent question concerning the calculation of the class group, so any help will be very much appreciated:) I'd like to illustrate my question with an example: Calculate the ideal class group of Q(√-17), giving a representative ideal for each ideal class and a description of the...
  14. A

    Computing a differential from plotted data

    I have a differential that depends only on \cos{\theta} \frac{\operatorname{d}\sigma}{\operatorname{d} \Omega} = f(\cos{\theta}) I am numerically solving this differential equation for \sigma, which physically is a cross section, for 0 \leq \theta \leq \pi. The differential contains a...
  15. A

    Computing a kronecker product of two matrices

    Does anyone know an algorithm for computing kronecker products of two matrices? It's probably not that hard, but I feel like my head is about to explode ATM, so if you can help me out that'd be cool. I want to implement this in fortran... I'll give you an example; Say I want compute the...
  16. J

    Computing Fourier transforms with exponentials

    Homework Statement Compute the Fourier transform of f(x)=exp(-b|x|), b>0 Homework Equations F(k)=1/2pi(integral[inf,-inf]f(x)exp(ikx)dx) The Attempt at a Solution F(k)=1/2pi(integral[inf,-inf]exp(ikx-b|x|) How do I solve this? I've tried to solve it but can't get to a solution...
  17. S

    Computing Integration of Bessel Function

    I tried to compute this exact solution, but faced difficulty if the value of η approaching to ζ . Let say the value of ζ is fix at 0.5 and the collocation points for η is from 0 to 1. θ(η,ζ)=e^{-ε\frac{η}{2}} \left\{ e^{-η}+\left(1-\frac{ε^2}{4}\right)^{1/2} η \int_η^ζ...
  18. R

    Biology, Economics, Computing or French

    I'm not really sure what I want to do after A level yet but I've sort of narrowed it down to Physics, EE, ChE, or Materials Sci. (OK its not that narrowed down) I've worked out that if I take: Maths Further Math Physics Chemistry That I should be covered for any of those 4 courses...
  19. J

    Quantum Computing: Attosecond Double-Slit Phenomena

    What are you guy's thoughts on constructing a quantum computer from attosecond double-slit phenomena?
  20. MathWarrior

    Programs Scientific Computing / Simulation and Modeling Degrees?

    I just was wondering if anyone here has pursued a degree in scientific computing / high performance computing / computational simulation and modeling, type of degree. For example Georgia Tech's Computational Science and Engineering degree or Computational and Mathematical Engineering degree, or...
  21. A

    Need some beginner info on Beowulf and paralell computing?

    Say I can get some used MB with CPU and RAM on it at a very low price, and a DMA 33 hard drive, home made powersource, how am I going to get all thoese MB connected? Using PCI slots? AGP slots? Or para. Ports? USB ports? Does Beowulf even support HD farm? That would be mind-blowing advance...
  22. F

    Drawing Phase planes, and computing the Poincare index

    Here is what I've done so far How do I draw the Phase portrait for this system? Have I done everything correct so far? Thanks
  23. A

    Computing normal probability analyticallyis this possible?

    Hey guys. I'm sure some of you are aware of how to analytically integrate e^(-x^2) dx from - infinity to infinity using polar coordinates. I have taken that logic and showed that the integral of the normal distribution( not necessarily standard) integrates to 1 over the entire domain...
  24. C

    Can't understand technique for computing transformation matrix

    My linear algebra textbook presents a technique for computing the transition matrix from an old basis B' to a new basis B. Apparently if you set up an augmented matrix with B on the left and B' on the right, then put B into RREF, the resulting matrix on the right after those row operations will...
  25. P

    Computing partial (conditional) correlation

    I wanted to compute the conditional pearson correlation (CPC). First, I wanted to make sure if it is OK to use the absolute pearson correlations in the computation of CPC. Becuase I think only the strength of pairwise correlations should be considered in computing CPC, and not the sign. Second...
  26. S

    0.2 percent offset for computing the yield point

    I need to compute the yield point for an experimental true stress vs true strain plot of a material as attached in the screenshot. See attached; I have true stress vs true strain plot. I took some initial points on the curve and fitted a straight line which gives me the elastic part of the...
  27. I

    Programs Quantum computing: major & job prospects?

    I'm having a hard time assessing the reality of job prospects in quantum computing research. The research seems mostly limited to schools I wouldn't dream of getting into and the companies pursing the technology seem limited as well. I'm currently undeclared and taking the basic math...
  28. S

    Trouble computing ∂^2 f/∂x^2 (1,1)

    Homework Statement Question: "Given that the surface x^4 * y^7 + y^6 * z^8 + z^7 * x^9 + 4xyz = 7 has the equation z = f(x,y) in a neighborhood of the point (1,1,1) with f(x,y) differentiable, find the derivatives. Find: a) ∂f/∂x(1,1) b) ∂f/∂y(1,1) c) ∂^2 f/∂x^2" Answers...
  29. S

    Computing the Mean of a Geometric Distribution

    Homework Statement Problem H-10. We will compute the mean of the geometric distribution. (Note: It's also possible to compute E(X^2) and then Var(X) = E(X^2)−(E(X))^2 by steps similar to these.) (a) Show that E(X) = (k=1 to infinity summation symbol) (k *q^k−1* p) where q = 1−p. (b)...
  30. T

    Solving Permutations with Multiple Sets: A Guide

    Homework Statement The problem says to compute the expression shown for the permutations σ, τ, and μ. My problem in particular says to compute |{σ}| for σ= (1 2 3 4 5 6; 3 1 4 5 6 2) The Attempt at a Solution My attempt to solve this problem was by first trying to change σ into σ^2...
  31. F

    Quantum Computing gate matricies

    Hi there I am working through a quantum gate section of my course and I am a bit puzzled on how to calculate a matrix for consecutive quantum gates. I understand how to generate a matrix for |q0⟩--------[H]------- |q1⟩------------------ Which is simply the tensor product of the hadamard...
  32. H

    Computing integrals on the half line

    Hi, In my fluids work I have come to integrals of the type: \int_{0}^{\infty}\frac{e^{ikx}}{ak^{2}+bk+c}dk I was thinking of evaluating this via residue calculus but I can't think of the right contour, any suggestions? Mat
  33. T

    Computing stress in hollow shaft

    Homework Statement An alloy steel shaft has an outside diameter of 100 mm. A central hole of 60 mm diameter is bored in part of its length as shown. Compute the shearing stress in the hollow section if the stress in the solid section is 200 MPa. Homework Equations angle = TL/GJ t = torque L...
  34. J

    Computing for Electric Field given cylindrical coordinates of v.

    Homework Statement If the scalar electric potential v in some region is given in cylindrical coordinates by v (r, \phi, z) = r^2 sin \phi e^{\frac{-3}{z}} , what is the electric field \vec{E} in that region? Homework Equations E = -\nabla v The Attempt at a Solution So...
  35. J

    Computing for magnetic force. Please check my answer.

    Homework Statement Find the magnitude and direction of the magnetic force on a charged particle with charge -4nC and velocity \vec{v} = (2.5\times 10^{4}) \hat{i} + (1.1 \times 10^{4}) \hat{j} (m/s) if the magnetic field in the region is given by \vec{B} = (1.2\times...
  36. V

    Computing Arc Length and Cannot Solve the Integral

    Homework Statement Find the length of the polar curve. Complete the cardioid r=1+cosθHomework Equations L=∫αβ√[f(θ)2+f'(θ)2] dθ The Attempt at a Solution Given f(θ)2 is equal to cos2θ+2cosθ+1 and f'(θ)2=sin2θ I arrive at the integral ∫αβ√[2cosθ+2] dθ which I cannot for the life of me...
  37. J

    Determining Charge on Insulated Balls in Equilibrium

    Physics Help Computing Force Homework Statement Two insulated balls with a mass of 0.8g each are suspended on 25 cm threads from the same point on the ceiling. Each ball has a equal positive charge. The angle formed between the two threads is 36 degrees. What is the charge on each ball...
  38. S

    Computing the period of a meteor using two ways.

    Computing the period of a meteor using two ways. I'm looking at code that computes the orbit found for a meteor. It computes the period of the meteor as: a = 13.07 # semi-major axis in AU P = m.sqrt(a*a*a) # From the program which yields P = 47.2512586393 Years If I use the...
  39. R

    Chemistry vs Biology vs Computing for Electrical engineering?

    I have to decide on what subjects I want to continue on for A level and was just wondering what I should pick as my last slot. I want to do Electrical Engineering at uni when I leave school. I'm really interested in either really big applications of EE like large HV plant stuff but also I'm...
  40. N

    Computing antiderivatives (integration)

    Homework Statement integrate 4e^(2x)^(1/2) - 1/7e^(-pix) using a guess and check method (haven't learned many rules of integration) Homework Equations The Attempt at a Solution i'm not really sure how to do this integral... i tried 4/(2x)^(1/2)[e^(2x)^(1/2)] using a table of...
  41. J

    Computing the Galois Group of a Univariate Polynomial (Irreducible or reducible)

    Is it possible to compute the Galois Group of a polynomial manually (without a computer)? If so, can someone please explain how? I can't seem to find any information (aside from computer algorithms) on how to find a Galois Group or how to factor a polynomial modulo a prime. If it helps to...
  42. B

    Computing parabolic orbital trajectory

    I wrote a game with a rocket that orbits a planet, and you can change the orbit with thrusters. As part of it I draw the predicted orbit for the rocket. To do this I compute the eccentricity vector, then the eccentricity e, then the major and minor axis of the ellipse or hyperbola as...
  43. N

    Superposition in quantum computing

    What of importance of superposition in quantum computing? What I understood is we have two states |0> and |1> which represent logical 0 and 1 . So the mixed state can be given by the combination of logical operators like OR, AND and NOR Etc. For example 1/3 |0>+2/3 |1> The particle...
  44. T

    Scientific computing and efficient memory usage

    Hi! I wonder if it is possible to get some book recommendations on the subject of efficient data structures and memory management in scientific computing? I do a bit of parallel programming in C/C++ with MPI, and I'm now considering trying my hand at some GPU programming as well. When...
  45. I

    Computing Heisenberg Uncertainty Value

    Homework Statement Consider a particle in a one dimensional box of length L, whose potential energy is V(x)=0 for 0<x<L, and infinite otherwise.Given the wave function at ground state ψ=sqrt(2/L)sin (pi*x/L) Compute ΔxΔp where Homework Equations Δx=sqrt(<x^2>-<x>^2) and...
  46. R

    Plancherel formula and integral computing

    My task is to 1) compute the Fourier transform of the function \frac{x}{1+x^2} 2) compute the integral \int_{-\infty}^{\infty}\frac{x^2}{(1+x^2)^2}dx 1) I can write my function as x \cdot \frac{1}{1+x^2} and by using the formula we let f(x)=\frac{1}{1+x^2}...
  47. J

    Quantum Computing: Superpositon of states problem

    Hey, I'm learning about quantum computing for a project and I'm a bit stumped about a concept: They say in quantum computing you can have the superpostion of all possible states, then perform an operation on that wavefunction, and thus have all possible states processed in one operation...
  48. S

    Simplest algorithm for computing the resultant of a boolean expression?

    hi, let's take something simple, for example: (a>b) && ((b>c) && c>d) || (d > c) Intuitively, it's easy to work out given the values of a, b, c and d and just evaluating the brackets in order of precedence. i.e. Is b > c?? then is c > d Then in addition to the above answer being...
  49. D

    Computing the line integral of the scalar function over the curve

    Homework Statement f(x,y) = \sqrt{1+9xy}, y = x^{3} for 0≤x≤1 Homework Equations The Attempt at a Solution I don't even know how to start this problem. I thought about c(t) since that's all I have been doing, but there isn't even c(t). I only recognize domain. Can anyone help me...
  50. P

    Computing Thermal Average for a Free Real Scalar Field

    Homework Statement Homework EquationsHi! I read a book where a free real scalar field with Hamiltonian H = \int \dfrac{\mathrm{d}^{3}p}{(2 \pi)^{3}} \, E_{\vec{p}} a_{\vec{p}}^{\dagger} a_{\vec{p}} is beeing discussed. Note that: E_{\vec{p}} = \sqrt{\vert \vec{p} \vert^{2} + m^{2}}...
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