Continuous Definition and 1000 Threads

In mathematics, a continuous function is a function that does not have any abrupt changes in value, known as discontinuities. More precisely, a function is continuous if arbitrarily small changes in its output can be assured by restricting to sufficiently small changes in its input. If not continuous, a function is said to be discontinuous. Up until the 19th century, mathematicians largely relied on intuitive notions of continuity, during which attempts such as the epsilon–delta definition were made to formalize it.
Continuity of functions is one of the core concepts of topology, which is treated in full generality below. The introductory portion of this article focuses on the special case where the inputs and outputs of functions are real numbers. A stronger form of continuity is uniform continuity. In addition, this article discusses the definition for the more general case of functions between two metric spaces. In order theory, especially in domain theory, one considers a notion of continuity known as Scott continuity. Other forms of continuity do exist but they are not discussed in this article.
As an example, the function H(t) denoting the height of a growing flower at time t would be considered continuous. In contrast, the function M(t) denoting the amount of money in a bank account at time t would be considered discontinuous, since it "jumps" at each point in time when money is deposited or withdrawn.

View More On Wikipedia.org
  1. evinda

    MHB How Does Continuity of T(n) for n≤2 Impact Asymptotic Bounds?

    Hello! (Wave)I am given some recurrence relations $T(n)$ and I have to give asymptotic upper and lower bounds for $T(n)$. We assume that $T(n)$ is continuous for $n \leq 2$. How can we use the fact that $T(n)$ is continuous for $n \leq 2$? (Thinking)
  2. rayne1

    MHB Expected value of a continuous random variable

    Given the PDF: f(x) = 1/12 , 0 < x <= 3 x/18, 3 < x <= 6 0, otherwise find the expected value, E(x). I know how to find the expected value if there was only one interval, but don't how to do it for two.
  3. A

    4 in lift mechanism using a continuous servo?

    Hi, I need to design a lift mechanism that is powered by a small continuous servo. It needs to lift a plate up at least 4 inches, and be totally powered by this servo...
  4. H

    Normal modes of continuous systems

    Homework Statement A room has two opposing walls which are tiled. The remaining walls, floors, and ceiling are lined with sound-absorbent material. The lowest frequency for which the room is acoustically resonant is 50Hz. (a) Complex noise occurs in the room which excites only the lowest two...
  5. A

    Heating a metallic rod from one end by continuous heat flux

    What is the solution of heat transfer equation when there is continuous heating ( flux of energy) to one end of a metal rod? what will be the temperature profile before reaching the steady state? when I try the boundary condition where one end (x=0) is kept at T1, I got the general solution of...
  6. L

    MHB Value to make function continuous

    Hello, I have this exercise that I can't solve: when x<3 the function f is given by the formula f(x)=$\frac{4{x}^{3}-12{x}^{2}+10x-30}{x-3}$ when 3 < or =x f(x)=$3{x}^{2}$-2x+a What value must be chosen for a in order to make this function continuous at 3? I think that I will have to equate...
  7. kelvin490

    Differentiability implies continuous derivative?

    We know differentiability implies continuity, and in 2 independent variables cases both partial derivatives fx and fy must be continuous functions in order for the primary function f(x,y) to be defined as differentiable. However in the case of 1 independent variable, is it possible for a...
  8. evinda

    MHB Cardinality of continuous real functions

    Hi! (Wave) Find the cardinal number of $C(\mathbb{R}, \mathbb{R})$ of the continuous real functions of a real variable and show that $C(\mathbb{R}, \mathbb{R})$ is not equinumerous with the set $\mathbb{R}^{\mathbb{R}}$ of all the real functions of a real variable. That's what I have tried: We...
  9. Z

    Is decay spectrum continuous or discrete?

    For a definite particle,the decay mode is determinant,finite kind,which embody the characteristic of quantum mechanics. But for a specific mode of a definite particle's decay,the decay spectrum,ie,energy of products,continuous,or discrete? Decay is a process which has unique initial...
  10. J

    Mounting a small ultrasonic sensor to a continuous rotation servo

    I'm an Arduino electronics hobbyist I'm not a professional electrical engineer. How would I mount a small ultrasonic sensor on a continuous rotation servo, without tangling the wires? How would I fix this problem easily and what's the most common way to mount electronics in a rotating object...
  11. nomadreid

    Continuous set of eigenvalues in matrix representation?

    Let's see if I have this straight: Observables are represented by Hermitian operators, which can be, for some appropriate base, represented in matrix form with the eigenvalues forming the diagonal. Sounds nice until I consider observables with continuous spectra. How do you get something like...
  12. B

    MHB Advanced Calculus - Continuous Functions

    I'm really stumped on how to do these proofs… I would really appreciate any help or insight!
  13. Julio1

    MHB Showing Connexity of $f(K)$ for Continuous $f$ on Connexe $K$

    Let $f: K\subseteq \mathbb{R}^n\to \mathbb{R}$ continuous, $K$ an connexe subset. Show that $f(K)$ is connexe.
  14. M

    Is Decoherence a Continuous Process?

    When a particle decoheres, or its component states get entangled with the ``environment``, surely this is not a final eigenstate. The particle is interacting ( becoming entangled etc) with other particles and systems constantly. Therefore, isn't decoherence a continuous process?
  15. M

    MHB Show that there is a continuous g with compact support

    Hey! :o If $f$ is a measurable complex function (that means that it doesn't take the values $\pm \infty$) with compact support, then for each $\epsilon >0$ there is a continuous $g$ with compact support so that $m(\{f\neq g\})<\epsilon$. Could you give me some hints how I could show that...
  16. D

    Is this function x/sinx continuous?

    Can we judge about continuity of function x/sinx?? Many examples in Google about sinx/x or xsinx but nothing about this function? Is there any special case? Regards
  17. T

    PDF of a continuous random variable

    Homework Statement Let X denote a continuous random variable with probability density function f(x) = kx3/15 for 1≤X≤2. Determine the value of the constant k. Homework Equations I'm not sure if this is right but I think ∫kx3/15 dx=1 with the parameters being between 2 and 1, The Attempt at a...
  18. I

    Expectation of Continuous Random Variable [word problem]

    Homework Statement Here's the problem with the solution provided: Homework Equations Fundamental Theorem of Calculus (FToC) The Attempt at a Solution So I understand everything up to where I need to take the derivative of the integral(s). Couple of things I know is that the derivative of...
  19. DavideGenoa

    Identical Fourier coefficients of continuous ##f,\varphi\Rightarrow f=\varphi##

    Hi, friends! Let ##f:[a,b]\to\mathbb{C}## be an http://librarum.org/book/10022/173 periodic function and let its derivative be Lebesgue square-integrable ##f'\in L^2[a,b]##. I have read a proof (p. 413 here) by Kolmogorov and Fomin of the fact that its Fourier series uniformly converges to a...
  20. TrickyDicky

    Is Space-Time a Continuum or a Physical Object?

    GR models of the universe describe it as a continuum, a smooth manifold, on the other hand the universe contains matter and matter is considered discrete.
  21. W

    Proof showing that if F is an antiderivative of f, then f must be continuous.

    Homework Statement Show that if F is an antiderivative of f on [a,b] and c is in (a,b), then f cannot have a jump or removable discontinuity at c. Hint: assume that it does and show that either F'(c) does not exist or F'(c) does not equal f(c). 2. The attempt at a solution I attempted a proof...
  22. N

    Making a piecewise function continuous everywhere

    Homework Statement Given the piecewise function f(x) = \left\{ \begin{array}{lr} \frac{(2-x)^2-p}{x} &: x < q\\ r(x+6) &: q \leq x <2 \\ x^3-p &: x \geq 2 \end{array} \right. Find the values of p,q,r such that f(x) is continuous everywhere and f(2) = p The Attempt at a Solution Since f(2)...
  23. S

    Continuous Functions - Apostal's One-Variable Calculus

    Homework Statement A function f is defined as follows: ƒ(x) = sin(x) if x≤c ƒ(x) = ax+b if x>c Where a, b, c are constants. If b and c are given, find all values of a (if any exist) for which ƒ is continuous at the point x=c. Homework EquationsThe Attempt at a Solution I was unsure of how to...
  24. rayne1

    MHB Find the values of a and b so the function is continuous everywhere.

    Find the values of a and b that make f continuous everywhere. f(x) = (x2 − 4)/(x − 2)...if x < 2 ...ax2 − bx + 3... if 2 ≤ x < 3 ...4x − a +b....if x ≥ 3 This is a piece-wise function. So I know that to be continuous everywhere, the function has to be one solid line. But I have no idea how to...
  25. ecoo

    Continuous Compounding Interest

    Hello So from what I understand, the continuous compound formula finds out the most you can get from interest no matter how many times you compound the interest in a set amount of time. So how come when I plugin in a big number into the regular compounding formula for the rate, the end amount...
  26. B

    Simple continuous back-and-forth linear movement

    I need to purchase a device that will push something forward and backward continuously, in order to make wings flap like a bird. Linear actuators seem to be the right thing to buy, except these require pressing buttons to go forward and then back. What can I buy/what can I do that will allow a...
  27. Astronuc

    Oldest cities, with continuous habitation

    I've actually been through Plovdiv. The area is quite interesting. I would love to visit Turkey, and Lebanon and Syria, once is becomes stabilized. https://www.yahoo.com/travel/the-oldest-cities-in-the-c1412019813265.html
  28. G

    Continuous function and definition

    If a function is continuous (nothing else specified), is it defined over R? Continuity means a function's value being the same as the limit for that point IIRC, but I don't know if it being continuous (over R presumably) means that it is also defined over R, or just that it's continuous wherever...
  29. A

    A problem about virtual work principle for continuous system

    dear all, the virtual work pinciple can be used to derive the equilibrium equations for the mechanical systems. however, when I want to apply it to a continuous system, I found it can not give out the simple equilibrium equations. there should be something wrong with my thinking. I expect some...
  30. I

    Find the value of a and b for which the function is continuous at 2

    Homework Statement u(x) = \begin{cases} \frac{3x+b}{4} & \text{if } x \geq 2 \\ \frac{(3-x)^n-a}{x-2} & \text{if } x < 2 \end{cases} find the value of a and b for which the function is continuous at 2 The Attempt at a Solution I tried to proof that lim(3x+b)/4 = lim (3-x)^n-a/x-2 = f(2)...
  31. D

    Statistics: mean/expected value of an continuous distribution

    So, the exercise is to find the expected value of following distribution: f(x) = 0,02x 0<x<10 answer in the book says 6,67 As far as I knowe, the expected value is calculated by the Integral of x * f(x) between 0 and 10, in this case! It looks like this won't give the result 6,67! what am...
  32. arivero

    Continuous symmetries as particles

    I am not sure if I recall all the ways for a symmetry to appear as some particle in a Quantum Field Theory. - The Lagrangian and the vacuum is invariant under the generators of a global symmetry/gauge group. Then the particles in the theory are classified according representations of such...
  33. A

    Semicircular Permanent Magnet Rail Gun - continuous motion?

    Doubtless you are all familiar with a rail gun made by using permanent magnets. An example is given here: http://sci-toys.com/scitoys/scitoys/magnets/gauss.html Assuming the railgun could me made curved, won't it be possible to build a curved track to transport the projectile - assume...
  34. N

    Why do multiparticle states present continuous in spectral function?

    I have learned the fact from Peskin QFT book,that one-particle state presents a delta function form in spectral function at s=m^2,while multiparticle states present a continuous form begin at s=4m^2,but i don't really understand the reason.What cause the difference between one-particle state and...
  35. afcsimoes

    Is Ultimate Reality Continuous or Discontinuous?

    Considering: a) The logical foundation of Mathematics and Mathematics as the foundation of Physics. b) The principle of excluded middle (nothing can be simultaneously something and its opposite). c) The ultimate physical reality: It must be discontinuous or continuous; it can neither be...
  36. johann1301

    Is tan(x) continuous when x = pi/2?

    Is the tangents function tan(x) continuous when x = 90 degrees or x = pi/2?
  37. X

    Electric Fields - continuous charge distributions

    Homework Statement A plastic rod of finite length carries an uniform linear charge Q = -5 μC along the x-axis with the left edge of the rod at the origin (0,0) and its right edge at (8,0) m. All distances are measured in meters. Determine the magnitude and direction of the net electric...
  38. DavideGenoa

    Continuous functional s.t. $f(x_0)\ne 0$

    I read that in any locally convex topological space X, not necessarily a Hausdorff space but with linear operations continuous, for any ##x_0\ne 0## we can define a continuous linear functional f:X\to K such that f(x_0)\ne 0. I cannot find a proof of that anywhere and cannot prove it myself...
  39. S

    Integration involving continuous random variable

    Homework Statement please refer to the question, i can't figure out which part i did wrongly. i 'd been looking at this repeatedly , yet i can't find my mistake. thanks for the help! the correct ans is below the question. where the c= 283/5700 , q = 179/5700 Homework Equations The...
  40. D

    Theorem on continuous function crossing x-axis

    I think this is a theorem, and I'm telling myself that I've proved it. Just a shout out for any possible counter-examples: If a function f(x) is continuous on some interval and has non-zero derivatives at its root(s) (where f(x')=0 ) then there is some interval around the roots where there are...
  41. M

    Prove that [itex]f: X \rightarrow Y[/itex] is a continuous function.

    My question is: Let f:\bigcup_{\alpha}A_{\alpha} \rightarrow Y be a function between the topological spaces Y and X=\bigcup_{\alpha}A_{\alpha}. Suppose that f|A_{\alpha} is a continuous function for every \alpha and that {A_{\alpha}} is locally finite collection. Suppose that A_{\alpha} is...
  42. atyy

    Naimark extension for continuous variables

    For discrete variables, a POVM on a system can be thought of as a projective measurement on the system coupled to an apparatus. This is called the Naimark extension. Is this also true for continuous variables? http://arxiv.org/abs/1110.6815 (Theorem 4, p10)
  43. M

    Lead-lag test for discrete variable vs continuous variable

    Let's say I'm applying electrical currents to a certain part of a human test subject and measuring certain deflections in his heart readings during this period. Before I increase the electrical currents, which could be dangerous, I'm interested to see if the changes in electrical currents are...
  44. T

    Fourier analysis and continuous spectra

    So I've been self-studying from Griffiths Intro to QM to get back in shape for graduate school this fall, and I guess I'd just like some confirmation that I'm on the right track... So while I am sure there are many other applications, the one I am dealing with is eigenfunctions of an operator...
  45. T

    Calculating a probability given a point for a continuous distribution?

    I thought I understood all the theory quite well and sat down to begin coding until I realized that calculating a probability at a point within a normal distribution in the application of bayes' rule you can't simply plug the point into the normal distribution and get the value since the...
  46. W

    Continuous Charge Distributions

    Homework Statement A charge lies on a string that is stretched along an x-axis from x = 0 to x = 3.00 m; the charge density on the string is a uniform 9.00 nC/m. Determine the magnitude of the electric field at x = 8.00 m on the x axis. Homework Equations \int_0^3 kλ/(8-x)^2\,dx...
  47. kq6up

    Continuous (non-discrete) Quantum States

    I am watching James Binney's QM lectures on iTunes University, and also going through his free textbook. He is a tough teacher, but I love how many misconceptions he points out, and some of the points he makes are very subtle and mind blowing when the lightbulb comes on. I am confused on...
  48. D

    MHB Continuous joint probability density functions

    Consider the following joint probability distribution function of (X , Y): a(x + y^2) {0<=x<=2, 0<=y<=2} 0 otherwise Calculate the value of the constant a that makes this a legitimate probability distribution. (Round your answer to four decimal places as appropriate.) And then, For the...
  49. D

    MHB Expected value/variance of continuous random functions?

    For the following probability density function: f(x) = [(x^2)/9] between 0 <= x <= 3 0 otherwise calculate the expected value E(X) of this distribution, and also calculate the variance I know I have to integrate the function but I don't know what else. Thanks!
  50. M

    How to check if this function is continuous

    Hello. The question is in the attached, together with my attempt. As you can see, I found the limit, but I don't know what each value means. If I have calculated the limits correctly, how do I know know if f(z) is continuous at 0 or not?
Back
Top