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. C

    Mathematica Symbolic computation: Mathematica help

    Hi, I need to get a simplified equation by setting the determinant of the following expression to zero: exp(j.omega.dt). [I] - [G] Here, I is an 18x18 identity matrix and G is an 18x18 matrix that I got by doing some symbolic computation in Mathematica (in fact G is huge). Can anyone...
  2. P

    Differential geometry:2-form computation on a pair of tangent vectors

    Homework Statement I am given a one form Psi = zdx -xydy and two vectors v(1,1,-2) and w(-2,1,1) both tangent vectors of R3 at point P(2,-1,0). I am asked to find dPsi(v,w). Homework Equations Lie bracket? The Attempt at a Solution I know how to computer Psi(v) at p but this...
  3. somasimple

    Cylindrical Capacitor Computation

    Hi All, from this page (Cylindrical Capacitor) => http://www.phys.uri.edu/~gerhard/PHY204/tsl105.pdf What happens when L is <= b? Does the computation change? and from this page http://www.physics.umd.edu/perg/abp/TPProbs/Problems/E/E52.htm The capacitor is simplified to a plane...
  4. C

    Quantum Computation: 2 Interesting Qs

    I have 2 questions about quantum computation that I find interesting. 1. I understand that because the qubits are in a superposition and therefore do not have defined values that they perform all the possible calculations at once therefore making it the most powerful and parallel processor...
  5. Amith2006

    Understanding Elementary Gates For Quantum Computation

    Homework Statement With reference to a research paper on "Elementary gates for Quantum computation", I'm unable to understand certain concepts given in it. I am providing a link to this paper which is: http://arxiv.org/PS_cache/quant-ph/pdf/9503/9503016v1.pdf Lemma 5.1 For a unitary 2x2...
  6. H

    Computation in nuclear engineering

    To what extent is computation used in nuclear reactor design? For example in aerospace CFD and FEM softwares are frequently used in the design process; the days of wind tunnel testing is limited to its absolute minimum. What are major softwares used in NE? Are there softwares such as NX, that...
  7. C

    Researching DNA Computation: Questions & Answers

    I have a problem with DNA computation that is currently being researched. Currently all the research is being done because cells are so parallel but how is that even useful. I keep thinking if you have this so called cell computer calculate every possible addition problem possible for a 32 bit...
  8. W

    Computation & Modeling: 10 Programs Used in Physics

    What are 10 big programs that are used today(in industry) for computation and modeling of physical sciences, specifically physics.
  9. Amith2006

    Physics Top Universities in UK for Quantum Computation

    I hope to pursue a research career in Quantum computation. Could anyone suggest some good universities in UK where active research is going on in this field?Any information is most welcome.
  10. Amith2006

    Quantum Computation: A Single Qubit's Infinite Possibilities

    A qubit state can be represented geometrically by Bloch sphere. A Bloch sphere has infinite points and so a single qubit can represent infinite number of states. Qubit state is represented by, Ipsi> = cos(theta/2)I0> + exp(i(phi))sin(theta/2)I1> It is said in the Book on Quantum...
  11. A

    Graduate Research in Quantum Computation

    What graduate schools are the best if I want to pursue research in Quantum Computation? I know MIT has a good program and I am going to apply there but what other schools would you recommend? I would prefer to stay on this side of the Atlantic.
  12. M

    What is quantum computation about?

    Hi, I'm new graduate student and I need to know what is the quantum computation about? My second question is the same as above for "particles physics". is anyone to help me? thanks
  13. Somefantastik

    Verifying u ∇²w via Direct Computation

    u,w are scalar functions of 3 variables the book says you can verify by direct computation: u\nabla^{2}w = \nabla \bullet\left(u\nabla w\right) - \left(\nabla u\right)\bullet\left(\nabla w \right) and \nabla^{2}w is \Delta w, the Laplacian operator. Every time I've worked this, I just can't...
  14. G

    What is Computational Finance?

    Hello, I'm in my last year of a B.Sc with a double major in math and physics. I was somewhat interested in becoming an actuary, and was discussing it with a friend of mine when he brought up computational finance as an alternative. I did some 'googling' about it, and i seems pretty...
  15. Amith2006

    Physics Choosing the Right Field of Study for a Career in Quantum Computation

    Hi guys. I’m a graduate student in physics. I’m interested in quantum computation. In what field of physics should I take up my further studies to get into this area? Any information is most welcome.Thanx in advance.
  16. H

    MATLAB [Matlab] How to obtain the computation time of a function

    Hi, all. I have a function in Matlab. I'd like to calculate the computation time of the function. How can I obtain the time? I think Matlab must include related functions as its internal functions. Thanks in advance.
  17. H

    Undergrad thesis on quantum computation (or LQG)

    Hello, I'm a 4th year physics undergrad, so I'm about to decide what to do in my undergrad thesis. I'll do pure theoretical work, but I'd like to avoid copy-paste stuff and come up wityh something quite original, however I'm not sure what topic are available, maybe someone here will help...
  18. MathematicalPhysicist

    Computation of an integral (Use of Resdiue theorem).

    I need to compute the integral: \int_{0}^{\infty}dx\frac{cos(x)}{cosh(x)} so obviously i need to use the residue theorem here and evaluate the contour integral of the complex function (cos(z)/cosh(z)) the singularity point here is z=i\pi/2 the intervals i decided to do the are...
  19. B

    Integral square error computation

    Hi, I am struggling computing the integral square error between two square waves. one is ideal and the other is assymetric. the equation for the assymetric is: x(t)= A for |t|<=To/4+ε/2 and -A for (To/4)+(ε/2)<|t|<=To/2 we were asked to plot the ideal( without the ε) and actual (or...
  20. B

    Vector calculus - line integral computation

    Compute the line integral \int_{C} F\cdot dr where F = -y i + x j. The directed path C in the xy-plane consists of two parts: i) a left semicircle from (0, -1) to (0, 1) with center at the origin, and ii) a straight line segment from (0,1) to (2,1). i) r(t) = cos t i + sin t j [pi/2 <=t<=...
  21. P

    Help about the numerical computation on the following equations

    Dear every memeber, I encountered the numerical computation on the following differential equations. I use four-step Runge-Kutta methods to integrate, but the result is not converge, even if I take the time step (t=0.0001). please help me why so? Could you please tellme which Fortran...
  22. J

    Fortran Double precision computation time in fortran

    I've written a program that repeats a calculation a certain number of times in single precision, then in double precision. The times are recorded by the cpu_time(real t1) subroutine. (Specifically, the calculation is aReal/(aReal+0.01) .) It seems that the time for the double calculation is 1.20...
  23. T

    Computers, computation and heat

    There is a computer forum and a brain forum. I don't know which to choose. But I'll go here. Computers made more progress in the last ten years than cars did in the last hundred. But Blue Gene still falls short of the speed attributed to three pounds of goo in my head (20 quadrillion ops per...
  24. P

    How to include disorder in the numerical computation?

    For example, in tight binding model, the site energy is random I want to have 100 disorder realizations, then I have the following two questions: 1. Do different realization needs different seed in the random number generation subroutine? 2. When all realizations are completed, the...
  25. E

    Understanding Liouville Space Super-Operators: A Simple Computation?

    "straightforward computation..." Hello. I am reading a paper that discusses moving from a regular NxN dimensional Hilbert space into and N^2 X N^2 dimensional Liouville space. The density matrix can be re-written as a 1 X N^2 vector by stacking the rows and the Liouvile equation can be...
  26. V

    Symbolic computation of gradient

    I'm wondering if there are any convenient symbolic "shortcuts" (i.e. abuse of notation) that enable one to compute the gradient with respect to a certain vector, without decomposing the computation into the vector's individual elements and differentiating with respect to each element. For...
  27. MathematicalPhysicist

    Integrating Tricky Functions: Solving and Proving Integrals

    i need to solve/prove the next two integrals: \int\frac{dx}{u^2+u+4} and i need to show that: \int_{0}^{\pi}\sqrt{1+sinx}dx=4 the problem is that i have a clue to substitute u=sinx and then sin(pi)=0=sin0 so the integral should be equal zero, is it not? ofcourse the integrand becomes...
  28. -Job-

    Human Computation: Google Tech Talk

    The following tech talk at google discusses using humans to collect useful information for things such as images, using games. It's an interesting approach, which certainly makes a lot of sense. http://video.google.com/videoplay?docid=-8246463980976635143&q=techtalk&hl=en
  29. S

    Feynman's; Path Integral formalism on Quantum Computation

    I have a nutty feeling that I can apply the Feynman Path Integral approach to calculate the efficient Quantum Computation paths on a Poincare or a Bloch sphere, can anyone help me with a formal introduction to teh path integral approach of QM, so that I can see ways I can apply it to Quantum...
  30. S

    What computer skills are required for physicists working in the field?

    I thought this might be a well-used thread if I asked the following: What computer skills do physicists use in their work? Please tell me what technology you have learned for whatever job you do. This questions mostly geared toward those of you guys out in the field, not fellow undergrads...
  31. H

    Master Theory of Computation: Models, Properties, and Equivalences

    I am taking this course this semester and i don't have enough idea about what this is all about...like i want to have a clearcut view in mind like how this coyrse helps...please i appreciate your comments.. Syllabus runs as:: Theory of Computation Course Contents: Models of computation...
  32. H

    Introduction to Quantum Computation

    Nice lectures describing the theory of Quantum Computation. I'm currently watching them. http://www.quiprocone.org/Protected/DD_lectures.htm
  33. G

    Quantum Computation and Quantum Information

    Hey all, I'm a beginner of the Quantum Computation and Quantum Information. For a long time, I feel very confuse about the question bellow. Could you do me a favor and show me the proof? Many thanks! Question: Show that any qubit can be expressed as psi=exp(iγ)[cos(θ/2)0+exp(iΦ)sin(θ/2)1]...
  34. P

    The Deutsch problem in quantum computation

    I'm doing a research paper on the deutsch problem in QC. My google inquiries have turned up numerous papers on solutions to the problem, but I am having difficulty finding a clear formulation of the problem itself. Can someone point me in the direction of this information?
  35. K

    How Does Counterfactual Computation Work?

    I hope this news isn't moved to another forum - many of our readers would be interested in this: Quantum computer solves problem, without running http://www.news.uiuc.edu/news/06/0222quantum.html "It seems absolutely bizarre that counterfactual computation – using information that is...
  36. A

    Quantum Computation: Finding a Community

    So, as I have found out through my exhaustive search for a solid grad program, it is hard to find a close-knit group of quantum-computation-ers. After tossing a coin 3 times, I found the best place to look for anyone interested in the field is in this group rather than Computers or Engineering...
  37. MathematicalPhysicist

    Can You Help Me Compute These Limits as X Approaches Infinity?

    i need to compute the lim of (1+2/x)^x or (1-1/x)^x and (1+1/x)^(x+3) when x approaches infinity. if you can provide a steady method to compute it, it will be appreciated. btw i know that lim (1+1/x)^x as x->inf is "e", but does it have any correlation to here.
  38. N

    How to do computation in Liberty Basic

    I am trying to write a very simple program in Liberty Basic. The last step in the program gives me a answer in inches, and I want to convert it to feet. So I figured I would simply divide the answer in inches by 12, then multiply ONLY the decimal value by 12, and then I would have the value in...
  39. H

    Logic & Computation: Same Coin? How?

    Is logic & computation two sides of the same coin.?if yes,How?
  40. E

    Computer Programs & Systems for Calculating Cosine Values for Large Numbers

    Are there any computer programs, or computer systems out there that can compute trigonometric values for cosine for large numbers like cos((pi)*t) = cos((pi)*2.34579^2000) to an accuracy of three decimal spaces? Where pi is the number 3.1415...n If so, what systems are available, how might...
  41. B

    Finding Eignevalues & Eigenvectors of A⁻¹ Without Direct Computation

    Hi, I need help for this problem: Find the eignevalues and eingenvectors for the matrix below. DO NOT compute them directly by computing the matrix: A-1 We need to find some kind of demonstration to see if the eignevalues of A-1 are the same, opposite or inverse (or whatever) as those of...
  42. B

    ONUS: Limit Computation: Evaluating xy/(x^2+y^2) at Origin

    Hi , I have difficulty to find the folowing questions about limit computation. IF lim xy/(x^2+y^2) ( when (x,y)---(0,0)) Evaluate the limit as (x,y) approaches the origin along: a) The spiral r=0, θ >0 b) The differentiable curve y=f(x), with f(0)=0 c) The arc r=sin(θ ) Thank you B
  43. Q_Goest

    Reversible Computation: Feasible?

    This regards an article found in the journal of Nature, 26 Aug. '04. I thought it might be interesting, not so much for the physics it presents (although they are certainly fascinating) but because of the implications. I think a discussion around the questions provided at the end of this essay...
  44. A

    Course called scientific and engineering computation

    course called "scientific and engineering computation" I am taking a course called "scientific and engineering computation" using the MATLAB program and I was just wondering where should I post questions on this topic?
  45. C

    How to find a short-term Visiting Position in Quantum Computation?

    How to find a short-term Visiting Position in the area of Quantum Computation? I interesting to collaboration with other research groups. One of my results is Probabilistic Simulation of entangled states and Quantum Computation. I have the computer's program for simulation of Qubits in Pascal...
  46. R

    NP-Problems and molecular computation

    Ten years ago (Science 1994;266:1021-4), Adelman built the first DNA based computer to solve the so-called Hamilton Path problem for seven nodes. SAT problems were solved with similar approaches by Lipton (Science 1995;268:542-5), with a DNA-based algorithm and Faulhammer (PNAS 2000;97.1385-9)...
  47. D

    Explain Algorithmic Cooling: "Redemption Ark" by Alastair Reynolds

    can someone explain algorithmic cooling to me? (i think that's what it's called.) in a work of fiction i am presently reading, an interior space is cooled by a quantum-computational device engaged in ongoing calculations. the book is 'redemption ark' by alastair reynolds and the technology is...
  48. O

    Quantum Field Computation: Beyond Quantum Computing?

    Quantum mechanics allows one to compute in a way fundamentally different from any way to compute classically, at least in theory. Will quantum field theory allow new kinds of computing that go beyond quantum computing? I would have suspected not, but for example this paper argues that it may...
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