What is Computation: Definition and 248 Discussions

Computation is any type of calculation that includes both arithmetical and non-arithmetical steps and which follows a well-defined model (e.g. an algorithm).
Mechanical or electronic devices (or, historically, people) that perform computations are known as computers. An especially well-known discipline of the study of computation is computer science.

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  1. J

    Solve the commutator relations

    Hello, I need to solve the commutator relations above. I found the equation above for the last one, but I am not sure, if something similar applys to the first one. I am a little bit confused, because I know there has to be a trick and you don't solve it like other commutator. Thanks for your help!
  2. Demystifier

    I Ontology is to quantum theory what hardware is to computation theory

    In interpretations of quantum mechanics there are two types of physicists: those who care about ontology and those who don't. The ontologists, or realists, want to know what is the world made of. The non-realists, on the other hand, think that this question is not relevant to physics. Usually...
  3. T

    Cubical Pressure Vessel - Maximum Pressure Computation

    Hello everyone - this is my first post on the forum and this would be for a real world application. I have no mechanical engineering experience. We plan to build a cubical aluminium (6082 grade) pressure vessel. The total external dimensions are 540mm x 400mm x 75mm. The aluminium wall...
  4. A

    App that converts a checklist to a text

    Hi, I am looking for an app that converts a checklist to text. The advantage of this app is to save time in writing professional reports. For example, suppose a professional uses a list of 10 possible variables to examine a case but finds only 4 variables match a pre-set quality criteria. In...
  5. C

    Comp Sci Regular Expression in Theory of Automata and Computation

    In first part,since every block of 4 consecutive symbol contain at least 2 a's The answer in notes is given (aa(a+b)(a+b)+a(a+b)a(a+b)+a(a+b)(a+b)a+(a+b)aa(a+b)+(a+b)a(a+b)a+(a+b)(a+b)aa)+ But this wont be true since if we choose aabbbbaa which is possible according to the above regular...
  6. C

    AI Computation (self study analysis, pointers welcome)

    In this thread I attempt to find a closed form solution to the gradient descent problem for a single sigmoid neuron using basic calculus. If you would like to give pointers feel free, if you see me make a mistake please let me know! Thank you!
  7. A

    I Counterfactual quantum computation on interferometer

    I watched a video on the topic by Sabine Hossenfelder. Now it is said by many that this proves the photon "knows" something in advance because a certain state of a certain beam splitter can be probed in theory without the photon ever encountering that beam splitter because it took another path...
  8. A

    I Quantum computation and entropy

    Quantum gates must be reversible. The usual justification for this is that in QM the time evolution of a system is a unitary operator which, by linear algebra, is reversible (invertible). But I am trying to get a better intuition of this, so I came up with the following explanation: In order to...
  9. J

    Preparing for a Quantum Computation Course: Superconducting Qubits

    Summary:: Looking for articles/books to prepare myself for the course: Quantum computation with superconducting qubits Hello everyone. I am about to take a course in Quantum computation with superconducting qubits and I am searching for material to prepare it. I took a first course on that...
  10. A

    I Question regarding actual computation of tensor at point (Self Study)

    Hello all, I am hoping to get some feedback on the manner in which I performed computations towards solving the following problem. There are a couple specific points which I am not confident of: 1. Did I properly account for the manifold structure in my computation of the nonzero components...
  11. G

    Numerical computation of the derivative

    I'm not sure if this is the correct forum to post this question, or should I post it in a math forum. But I was looking at some code when I found a 'strange' implementation to compute the derivative of a function, and I wanted to know if any of you has an idea of why such an implementation is...
  12. shivajikobardan

    Comp Sci DFA that accepts either ab or ba as substring?

    Attempt at solution-: Now this dfa will also accept abba which in my inituition it should not accept. But it does accept it. What is going here? Please guide
  13. MathematicalPhysicist

    I A computation of an integral on page 344 of Schutz's textbook

    On page 344 of "A First Course in GR" he writes the following: When I do the integration I get the following: ##\int_0^{\chi^2}d\chi^2= \int_0^{r^2}\frac{dr^2}{1-r^2}= \chi^2 = -\ln (1-r^2)##, after I invert the last relation I get: ##r=\sqrt{1-\exp(-\chi^2)}##, where did I go wrong in my...
  14. orochi

    Courses Learning Parallel Computation as a particle physicist

    I am starting my Master's Degree in Nuclear and Particle Physics, should i invest in taking a course in Parallel Computation? I know the role that Parallel Computation has in particle physics, but is there any use in a particle physicst learning about parallel computation, or could it be...
  15. F

    Neutron quantity normalization in an eigenvalue computation

    Dear Community, I am having a question. I have developed a simple code to perform iteration power algorithm and find the keff value of a system. However, it is not still totally clear in my mind if I have to normalize all my scores by the eigenvalue, i.e. multiply by the keff (fluxes, power...
  16. person123

    I Computing the Speed of Traveling Waves in 2 Dimensions

    I have a 2-dimensionsal smooth function ##f(x,y,t)##. There may be multiple traveling waves across the domain. None of them are precisely traveling waves (the shape of the wave changes as it travels). Here is how one of these waves would look in 1-dimension: I want to find the speed of these...
  17. person123

    I Computing the Density of a Point Cloud

    Hi. For some background, I am running molecular dynamics simulations of silica fracture in LAMMPS. Each point represents the location of a broken bond. I would like to find regions where many bonds are breaking, which I speculate would be locations of crack formation. These computations are...
  18. G

    A Can Data Travel Faster Than Light Computation?

    Hi bear with me I have a conundrum I want to ask you. If data traveled many times the speed of light could the results of decrypted cypher message be computed quicker than any system we currently have? For instance if we sent a burst of data at many times the speed of light across the solar...
  19. WMDhamnekar

    MHB Computation of the ratio of barometric pressure

    Hi, The Homestake gold mine near Lead,South Dakota is excavated to 8000 feet below the surface. Lead is nearly a mile high; the bottom of the Homestake is about 900 m below sea level. Nearby custer peak is about 2100 m above sea level. What is the ratio of barometric pressure on the top of the...
  20. O

    Problem in solving differential equation

    Hello everyone! I was studying chaotic systems and therefore made some computer simulations in python. I simulated the driven damped anhatmonic oscillator. The problem I am facing is with solving the differential equation for t=0s-200s. I used numpy.linspace(0,200,timesteps) for generate a time...
  21. WMDhamnekar

    MHB Computation of bond angles and other angles in tetrahedral

    Hello, I didn't understand the geometry of molecules in which central atom has no lone pairs of electrons. for example, in $CH_4, NH_4^+$ molecular shape is tetrahedral and bond angle is $109.5^\circ$. How is that bond angle computed? $CH_4$ stands for liquid methane and $NH_4^+$ is a...
  22. thaiqi

    Quantum Which books are good for learning spectrum computation?

    Hello everyone. I 'd like to learn how to calculate the spectrum for elements. Which books are recommended?
  23. thaiqi

    Are there articles on Classical computation of the Photoelectric Effect?

    photoelectric effect is now explained in quantum idea. Why the classical model fails? Are there articles computing it in detail using classical model?
  24. C

    I Rewriting a complex number for use in an analytic computation

    Consider an equation, $$\tilde{x_0} = \ln(X+ i\delta),$$ where X may be positive or negative and ##0< \delta \ll 1##. Now, if ##X>0## this evaluates to ##\ln(X)## in some limiting prescription for ##\delta \rightarrow 0## while if ##X<0##, we get ##\ln(-X) + i \pi. ## Now, consider...
  25. ronnie snooker

    B Does the Feynman diagram process actually exist, or is it just for computation?

    i want to known whether virtual particle exist or not , and does exchange of particle really happen in interaction.
  26. Quark Effect

    B What is the significance of 'i' in quantum computation notation?

    Hi guys, I am currently having some difficulties with this quantum state. I don't entirely understand what that letter 'i' means, where it comes from and why it appears in brackets [1, i]. Shouldn't there be a '0' instead? I am an absolute beginner in quantum computation. I've been following a...
  27. CrosisBH

    Trouble with Electric Potential Boundaries (Computational Physics)

    This is in python: #ELECTRIC POTENTIAL from mpl_toolkits.mplot3d import Axes3D from matplotlib import cm import numpy as np import matplotlib.pyplot as plt dx = 0.1 dy = 0.1 xrange=np.arange(-1,1,dx) yrange=np.arange(-1,1,dy) X,Y = np.meshgrid(xrange, yrange) max_dV = 10e-5 blockRadius = 3...
  28. G

    Programs Quantum Computation and Information Master's Degree

    I'm in a Physics BSc programme and I would like to delve into quantum computation and quantum information. There are two master's degree in Europe that I find interesting in particular: Quantum Engineering MSc at ETH Zurich and Applied Physics MSc at TU Delft (track in Quantum Devices and...
  29. S

    MHB Computation based on linear growth

    In 2000 the company had 300 customers. In 2015, this company already had 1200 customers. How many customers did the company have in 2008 if we know that the number of customers growing is linear?Just want to make sure, is 780 the correct answer?
  30. B

    Chemistry Computation of Liquid/Vapor Result during a Volume Expansion

    I am searching for the appropriate methodology/equation(s) to step beyond Boyle's Law to account for the phase change and solve this problem. All suggestions/guidance is greatly appreciated! Bruce
  31. DifferentialGalois

    Studying Value of learning the Theory of Computation and Automata

    This may be a somewhat disorderly, unplanned out question, but nonetheless, I don’t know whether or not there exist any suitable academic advising websites that would be suitable for posting such. Would it be worthwhile investing time into learning theory of computation and automata via Neso...
  32. Haorong Wu

    I Confusion about factoring in quantum computation

    Hi, I'm currently learning QC with Nielsen's QCQI. I've written a program in Matlab following the factoring algorithm in page 233 and 235. I run the program for factoring 15, 18, and 25. I got the proper results several times, but I also got error reports sometime, especially when factoring 18...
  33. T

    Speed usage in Lattice Boltzmann Method

    One thing that confuses me is the physical speed and sound speed. The lattice sound speed cs=1/sqrt{3} corresponds to the physical sound speed for isothermal flow (sqt{RT}). Why isn't the physical speed (e.g. inlet speed up of lid cavity) converted and use accoringly? $$c_p=\sqrt{RT}≈330m/s...
  34. Haorong Wu

    Quantum A book about problems of quantum computation?

    Summary: A book about problems of quantum computation? I remember that there is a book containing many problems of quantum computation, but I can't find the page or post now. I have hard time learning quantum computation. Thus, I want to try to solve problems in order to get a solid...
  35. Haorong Wu

    Schools Are there any good groups about quantum computation?

    Hi. After learning quantum computation for months, it fascinates me. Quantum computation expands my view about computational methods. I believe that many future achievements can be obtained from quantum computing, especially the combination of AI and quantum computation. Meanwhile, I think...
  36. Haorong Wu

    I How to understand the Bloch sphere in the quantum computation?

    I've read that ##\left | \psi \right > =cos \frac \theta 2 \left | 0 \right > + e^{i \phi} sin \frac \theta 2 \left | 1 \right >##, and the corresponding point in the Bloch sphere is as the fig below shows. I think ##\left | 0 \right >## and ##\left | 1 \right >## are orthonormal vectors...
  37. Haorong Wu

    Courses Is Griffiths' QM sufficient before studying quantum computation?

    Hello, again. My current interest is quantum computation. I've finished Griffiths' QM for the first time. Because it only takes me a month studying the book, I may have study it superficial, so I plan to study it again and complete all the problems after each chapter. Then is this book...
  38. Q

    I Will quantum computation lower energy requirements?

    According to this article, written by D-Wave's CEO, the advent of quantum computers will "change the way the world uses energy". However, on a first reading, it sounds like an advertorial that pushes nonsense. I'm no energy scientist (unless you put high energy physics in that category for some...
  39. W

    I Gravitational Jerk Computation

    I've seen much about jerk, and how it's generally nearly instantaneous, and for general acceleration, that's fine. However, if I lift at a constant acceleration upward slightly stronger than gravity is pulling me downward, the gravitation pull of the Earth will offset part of my force, so that...
  40. C

    MHB What are the DFA configurations for L={w:${n}_{a}$(w) mod3 < 1} on $\sum$={a,b}?

    Find dfa's for the following language on $\sum$={a,b}; c) L={w:${n}_{a}$(w) mod3 < 1;
  41. C

    I Explicit computation of mass counter term diagrams

    In most treatments of the mass renormalisation in dim reg, I see sources find the mass counter term by extracting the coefficient of e.g the ##m^2## term accompanied by a pole in epsilon. I know the mass counter term is found by placing an X on diagrams where there is usually a self energy...
  42. S

    Theory of Computation problem: Proving that L = L(A)

    Hello to everyone that's reading this. :) 1. Homework Statement (Theory of Computation) proof problem about proving that L = L(A) by proving that L ⊆ L(A) and that L(A) ⊆ L: https://www.docdroid.net/du7lLvh/theproblemanditssolution.pdf Homework Equations • Mutual simple induction • Formal...
  43. O

    Change of basis computation gone wrong....

    Homework Statement Consider the real-vector space of polynomials (i.e. real coefficients) ##f(x)## of at most degree ##3##, let's call that space ##X##. And consider the real-vector space of polynomials (i.e. real coefficients) of at most degree ##2##, call that ##Y##. And consider the linear...
  44. N

    I Computation of the left invariant vector field for SO(3)

    I am trying to improve my understanding of Lie groups and the operations of left multiplication and pushforward. I have been looking at these notes: https://math.stackexchange.com/questions/2527648/left-invariant-vector-fields-example...
  45. M

    I What is the Formula for Computing Surface Metric on a PF Surface?

    Hi PF! I'm trying to compute $$ \frac{1}{\sqrt g}\frac{\partial}{\partial u^\mu}\left( \sqrt g g^{\mu v} \frac{\partial \eta(s,\phi))}{\partial u^v} \right) $$ where I found $$ \sqrt g = \csc^2\alpha \sin s\\ g = \begin{bmatrix} \csc^2\alpha &0\\ 0 & \csc^2\alpha\sin^2 s \end{bmatrix}...
  46. V

    A Reducing computation for large power sets

    To illustrate my problem say I have the following table: Option, x , y A , 25 , 30 B , 5 , 12 C , 3 , 9 D, 12, 13 I want to create a graph of every possible combination in the set where the x values are added and the y values are added. For example say it was...
  47. peroAlex

    Computation of Thevenin Equivalent

    Hello! Recently I was going through some old exams and upon encountering this problem (which seemed pretty easy) I got stuck. Exams at my university are composed of individual tasks, each having three subquestions with four plausible answers respectively. Solution sheet gives results only, so...
  48. M

    Mathematica How can I optimize Mathematica computation time for functional definitions?

    Hi PF! I am using the following code in Mathematica mat = {{1, Cos[2], Cos[4], Sin[2], Sin[4}, {1, 1, 1, 0, 0}}; Li[x_] := Transpose[ NullSpace[ mat].{{1}, {Cos[x}, {Cos[ 2 x]}, {Sin[x]}, {Sin[2 x]}}]; Li1[x_] := Li[x].{{1}, {0}, {0}}; f[x_] :=...
  49. binbagsss

    QFT Klein Gordon Theory, momentum commutator computation

    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'...
  50. M

    Computation of maximum pressure in heated closed vessel

    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...
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