Continuity Definition and 908 Threads

In fiction, continuity is a consistency of the characteristics of people, plot, objects, and places seen by the reader or viewer over some period of time. It is relevant to several media.
Continuity is particularly a concern in the production of film and television due to the difficulty of rectifying an error in continuity after shooting has wrapped up. It also applies to other art forms, including novels, comics, and video games, though usually on a smaller scale. It also applies to fiction used by persons, corporations, and governments in the public eye.
Most productions have a script supervisor on hand whose job is to pay attention to and attempt to maintain continuity across the chaotic and typically non-linear production shoot. This takes the form of a large amount of paperwork, photographs, and attention to and memory of large quantities of detail, some of which is sometimes assembled into the story bible for the production. It usually regards factors both within the scene and often even technical details, including meticulous records of camera positioning and equipment settings. The use of a Polaroid camera was standard but has since been replaced by digital cameras. All of this is done so that, ideally, all related shots can match, despite perhaps parts being shot thousands of miles and several months apart. It is an inconspicuous job because if done perfectly, no one will ever notice.
In comic books, continuity has also come to mean a set of contiguous events, sometimes said to be "set in the same universe."

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  1. C

    Uniform Continuity: Showing f*g Is Uniformly Continuous on Bounded X

    Homework Statement suppose f and g are uniformly continuous functions on X and f and g are bounded on X, show f*g is uniformly continuous. The Attempt at a Solution I know that if they are not bounded then they may not be uniformly continuous. ie x^2 and also if only one is bounded...
  2. C

    Proving Uniform Continuity for f+g on X

    Homework Statement if f and g are 2 uniformly continuous functions on X --> R show that f+g is uniformly continuous on X The Attempt at a Solution I tried showing that f+g is Lipschitz because all Lipschitz functions are uniformly continuous. So i end up with d(x_1,x_2) <...
  3. C

    Uniform Continuity: Example of f*g Not Being Uniformly Continuous

    Homework Statement If f and g are uniformly continuous on X, give an example showing f*g may not be uniformly continuous. The Attempt at a Solution i think if the functions are unbounded the product will not uniformly continuous. Is there a specific example of this function..?
  4. K

    Proving Continuity for h(x) = x^x = e^xlnx, Given f(x) = e^x and g(x) = lnx

    Homework Statement f(x)=e^x g(x)=lnx h(x)=x^x=e^xlnx If f and g are continuous prove h(x) is continious for x>0 Homework Equations The Attempt at a Solution Ok this confuses me, because I would think that it wouldn't be too bad too do if h(x)=f(g(x)). Maybe the book had a typo?
  5. K

    Proving Continuity of a Polynomial Function at a Zero of Another Polynomial

    Homework Statement Let p and q be a polynomial and x0 be a zero of q of multiplicity m. Prove that p/q can be assigned a value at x0 such that the function thus defined will be continuous there iff x0 is a zero of p of multiplicity greater than or equal to m. Homework Equations The...
  6. S

    Solve Tricky Continuity Homework Statement

    Homework Statement 1. show there is some point x in the interval [0,pi/2] so that x = cos(x)^2 2. let f:R-> be continuous at c and suppose f(c) =1. show that there is some a > 0 such that f(x) > 1/2 whenever |x-c| < a Homework Equations intermediate value theorem. maximum minum...
  7. A

    Ensuring Continuity: Finding the Sum of a and b for a Continuous Function

    Homework Statement f(x) = x^2 - 4x + a g(x) = \lim_{n\rightarrow\infty} \frac {2|x-b|^n + 1}{|x-b|^n + 1} let h(x) = f(x)g(x) Find the sum of a+b that makes h(x) continuous for all x. Homework Equations Power Series? Derivation to test continuity? The Attempt at a Solution...
  8. C

    Show Pointwise Convergence of g_n to Zero Function

    Homework Statement Let f: [0,1] -> R (R-real numbers) be a continuous non constant function such that f(0)=f(1)=0. Let g_n be the function: x-> f(x^n) for each x in [0,1]. I'm trying to show that g_n converges pointwise to the zero function but NOT uniformly to the zero function...
  9. I

    Proving Continuity and Linearity of a Function

    Homework Statement Given that f(x + y) = f(x) + f(y), prove that (a) if this function is continuous at some point p, then it is continuous everywhere (b) this function is linear if f(1) is continuous. Homework Equations definition of continuity The Attempt at a Solution (a) I...
  10. S

    Real Analysis: Properties of Continuity

    Homework Statement Suppose f is continuous on [0,2]and thatn f(0) = f(2). Prove that there exists x,y in [0,2] such that |y-x| = 1 and f(x) = f(y) Homework Equations The Attempt at a Solution I got the following 1 line proof. Suppose g(x) = f(x + 2) - f(x) on I = [0,2]...
  11. N

    [QM] Finding probability current from Hamiltonian and continuity equation

    Homework Statement Given the Hamiltonian H=\vec{\alpha} \cdot \vec{p} c + mc^2 = -i \hbar c \vec{\alpha} \cdot \nabla + mc^2 in which \vec{\alpha} is a constant vector. Derive from the Schrödinger equation and the continuity equation what the current is belonging to the density \rho...
  12. 3

    Is Uniform Continuity a Property of Bounded Functions?

    Homework Statement Show that if a function f:(0,1) --> lR is uniformly continuous, f is bounded. Homework Equations - The Attempt at a Solution Really don´t know. I started thinking about Weierstrass Thereom but I am not sure that it´s ok. Now I think that may be is something...
  13. M

    Help with calculus problem- differentiability, continuity, with variables

    Homework Statement y= y= {1+3ax+2x^2} if x is < or = 1 {mx+a} if x>0 what values for m and a make x continuous and differentiable at 1? Homework Equations n/a The Attempt at a Solution i solved for when x=1. i got 3+3a. this is also the right hand...
  14. M

    Is the Graph of a Function Compact if the Function is Continuous?

    X, Y metric spaces. f:X-->Y and X is compact. How do I prove that f is continuous if and only if G(f)={(x,f(x)):x in X} C X x Y is compact. I think for the forward direction, since f is continuous and X is compact, then f(X) is compact. Hence, G(f)=X x f(X) is compact as a cross product of...
  15. T

    Another Analysis question: continuity and compactness

    Let I = [0,1] be the closed unit interval. Suppose f is a continuous mapping from I to I. Prove that for one x an element of I, f(x) = x. Proof: Since [0,1] is compact and f is continuous, f is uniformly continuous. This is where I'm stuck. I'm wondering if I can use the fact that since...
  16. E

    Continuity in Normed Vector Spaces

    Homework Statement Let V and V' be real normed vector spaces and let f be a linear transformation from V to V'. Prove that f is continuous if V is finite dimensional. The attempt at a solution Let v_1, v_2, \ldots, v_n be a basis for V, let e > 0 and let v in V. I must find a d such that...
  17. E

    Continuity on Restrictions Implies Continuity Everywhere

    Homework Statement Let (E, m) and (E', m') be metric spaces, let A and B be closed subsets of E such that their union equals E, and let f be a function from E into E'. Prove that if f is continuous on A and on B, then f is continuous on E. The attempt at a solution I have approached this...
  18. J

    Proof regarding property of continuity

    Homework Statement Prove that if f(x) satisfies the functional equation f(x+y) = f(x) + f(y) and if f is continuous then f(x) = cx for some constant c. Homework Equations N/A The Attempt at a Solution Assume |f(a)| > |ca| for some a in the domain of f. Since f is continuous at...
  19. J

    Is Every Continuous Function on a Compact Subset of \mathbb{R}^n Bounded?

    (Problem 62 from practice GRE math subject exam:) Let K be a nonempty subset of \mathbb{R}^n, n>1. Which of the following must be true? I. If K is compact, then every continuous real-valued function defined on K is bounded. II. If every continuous real-valued function defined on K is...
  20. 1

    Proving C1 Continuity of a Person's Path in a 2D Environment

    Dear all, I would appreciate if you could help me with the following problem: A person is standing still on a 2D environment and let's assume that its initial position Xo is given. The person is moving by applying a force function over time say f(t). As a result, using numerical integration we...
  21. J

    Please check proof on continuity

    The question seemed simple enough, but something feels funny about my proof. I would appreciate if someone could please check it. Question: Prove that if f(x) is monotonic on [a,b] and satisfies the intermediate value property, then f(x) is continuous. Proof: Let e denote epsilon and d denote...
  22. A

    Lipschitz function and uniform continuity

    A function f:D\rightarrowR is called a Lipschitz function if there is some nonnegative number C such that absolute value(f(u)-f(v)) is less than or equal to C*absolute value(u-v) for all points u and v in D. Prove that if f:D\rightarrowR is a Lipschitz function, then it is uniformly...
  23. M

    Derivation of continuity equation

    Homework Statement Hi. I have a problem in fluid mechanics that is asking me to derive the conservation of mass equation using an infinitesimal control volume. My problem is I do not know if I should be treating this problem as a fixed element or if the element is a parcel and its...
  24. R

    Can a U-tube with a moving piston maintain continuity in fluid flow?

    Please consider a U-tube filled with an incompressible fluid as in the attached figure. Piston P divides the fluid in two segments. When P moves, the fluid particles on immediate vicinity of either face (points marked 1 and 2) will have same velocity. Does this mean, they may considered to be...
  25. S

    LIMITS, continuity piece defined function

    The question asks to find a value for a and b that makes f continuous everywhere. f(x)= \frac{x - 4}{x-2} , where x<2 ax2 - bx + 3 , where 2<x<3 2x - a +b , where x > or = 3 I know that in order for a function to be continuous the limit as x approaches 2 must be equal from...
  26. C

    Eqn of Continuity: Incompressible & Compressible Fluids

    does eqn of continuity apply to only incompressible fluids?is there an eqn for compressible fluids?
  27. S

    Proof of continuity of convex functions

    Homework Statement Let a function f : R => R be convex. Show that f is necessarily continuous. Hence, there can be no convex functions that are not also continuous. Homework Equations The Attempt at a Solution F is continuos if there exist \epsilon >0 and \delta>0 such that |x-y|<...
  28. J

    Continuity equation from Stress-Energy tensor

    It is true that \frac{\partial}{\partial x^\beta} T^{0 \beta} = \gamma^2 c \left( \frac{\partial \rho}{\partial t} + \vec{\nabla} \bullet \left[ \rho \vec{v} \right] \right) = 0 but, how do we arrive at this point? What is in T^{ \alpha \beta} and how do we compute it for any...
  29. N

    Continuity and periodic functions

    Homework Statement We have a piecewise continuous function and T-periodic function f and we have that: F(a) = \int_a^{a + T} {f(x)dx} I have to show that F is diferentiable at a if f is continuous at a. My attempt so far: I have showed that F is continuous for all a. If we look at one...
  30. F

    Limit & Continuity of f(x) = sqrt(x+3), -3 < x < -1

    f(x) = sqrt(x+3), x > -3 3 x2-5, x < -3 first question would be limit x -> -3-, limit x -> -3+, limit x -> -3 the answer would be [-1, 1, undefined] But, i only got the 3rd answer correct, the first two are wrong?? but i don't get it why, the previous similar...
  31. G

    Continuity Equation: Is It Independent of Pipe Radius?

    For the continuity equation (Q= Av, A is cross sectional area, v is velocity), is it independent of the radius of the pipe? If so, why?
  32. B

    Is h(x) Continuous at x=5 Given Conditions on f(x) and g(x)?

    Can anyone help me with this problem? Say f(x) & g(x) are cont. at x=5. Also that f(5)=g(5)=8. If h(x)=f(x) when x<=5 and h(x)=g(x) when x>=5: prove h(x) is cont at x=5.
  33. E

    Prove Continuity of g: A Continuity Problem Homework Statement

    Homework Statement Let f be a function with the property that every point of discontinuity is a removable discontinuity. This means that \lim_{y\to x} f(y) exists for all x, but f may be discontinuous at some (even infinitely many) numbers x. Define g(x) = \lim_{y\to x} f(y). Prove that g is...
  34. E

    Continuity Problem: Show f is Continuous at a

    Homework Statement Suppose f(x + y) = f(x) + f(y) and f is continuous at 0. Show that f is continuous at a. The attempt at a solution Since f is continuous at 0, for any e > 0 there is a d > 0 such that |f(x) - f(0)| < e for all x with |x - a| < d. Writing 0 as -a + a, |f(x) - f(0)| =...
  35. C

    Why are neither sin(x^-1) nor xsin(x^-1) continuous at x=0?

    How come sin(x^-1) is not continuous and xsin(x^-1) is?
  36. N

    Differentiability implies continuity proof (delta epsilon)

    1. The problem statement. Give a complete and accurate \delta - \epsilon proof of the thereom: If f is differentiable at a, then f is continuous at a. 2. The attempt at a solution Known: \forall\epsilon>0, \exists\delta>0, \forall x, |x-a|<\delta \implies \left|\frac{f(x) - f(a)}{x-a}...
  37. T

    Deriving the continuity equation from the Dirac equation (Relativistic Quantum)

    So I am trying to derive the continuity equation: \frac{\partial}{\partial x^{\mu}}J^{\mu} = 0 From the Dirac equation: i\gamma^{\mu} \frac{\partial}{\partial x^{\mu}}\Psi - \mu\Psi = 0 And its Hermitian adjoint: i\frac{\partial}{\partial x^{\mu}}\overline{\Psi}\gamma^{\mu} -...
  38. P

    Is the Lebesgue-Integral Continuous with Respect to the L^\infty Norm?

    Hi, I was wondering if the Lebesgue-integral is continuos with respect to the L^\infty norm. More precisely, assume there is a space of functions \mathcal{P}=\{f\in L^1 :||f||_{L^1}=1\}\cap L^\infty endowed with the essential supremum norm ||\cdot||_{L^\infty}. If there is then a Cauchy...
  39. T

    Prove Continuity at a: f(x+y)=f(x)+f(y) & f(0) Continuous

    Homework Statement Suppose that "f" satisfies "f(x+y)=f(x)+f(y)", and that "f" is continuous at 0. Prove that "f" is continuous at a for all a.Homework Equations In class we were given 3 main ways to solve continuity proofs. A function "f" is continuous at x=a if: a.) Limit of f(x) as x->a...
  40. C

    Trouble understanding Continuity

    Hey folks, I have this one problem that seems unclear to me: Show that the function f is continuous at (0,0) for f(x,y) = ysin(1/x) if (x,y) do not equal (0,0)...and 0 if (x,y) = (0,0) I'm thinking though, as with single variable calc, f is continuous at...
  41. A

    Limits, Continuity and Calculus in 3D Space

    Ok, i am hoping we can (owing to the large amounts of questions in the homework help on stuff like this) create a nice guide for Calculus in 3D including definitions, practise questions and general examples. Firstly, i know something i really do not like is Limits. My textbook gives the...
  42. V

    Continuous Problem: Show f(x) > 0 on [r,s] of [a,b]

    Homework Statement Let f be a function which is continuous on a closed interval [a,b] with f(c) > 0 for some c\in[a,b]. Show that there is a closed interval [r,s] with c\in[r,s]\subseteq[a,b] such that f(x) > 0 for all x\in[r,s]. Homework Equations Hint let epsilon = f(c)/2 and find...
  43. R

    Proving Continuity of Power Series Function

    Homework Statement Show, from the definition of continuity, that the power series function f(x)=sum(a_n*x^n) is continuous for its radius of convergence.Homework Equations Definition of continuityThe Attempt at a Solution Must show that for any |a| < R, given e>0 there exists d>0 such that...
  44. O

    Continuity of an inverse function

    Homework Statement Prove that the a continuous function with compact domain has a continuous inverse. Also prove that the result does not hold if the domain is not compact. Homework Equations The Attempt at a Solution I tried using the epsilon delta definition of continuity but...
  45. R

    Continuity & Properties of functions

    Homework Statement Let f:R->R be a continuous function where limit as x goes to positive/negative infinity is negative infinity. Prove that f has a maximum value on R. Homework Equations None The Attempt at a Solution I tried to use the definition of infinite limits but I'm not...
  46. S

    Continuity of |f|: Examples w/ Discontinuity at 0

    Give an example of a function f which is discontinuous at 0 yet abs(f ) is continuous at 0 i have tried for an hour or so trying to think of one, even hints would be helpful
  47. M

    Show Continuity of F(x) in Lebesgue Integrable f [a,b]

    Let F(x) = Integral from a to x of f dt (a belongs in [a,b]) How do we show that F(x) is continuous? (f is Lebesgue integrable on [a,b] )
  48. B

    Continuity of f(x) at Rational and Irrational Points

    Homework Statement f(x) = {x^2 x \in Q -x^2 x \in R/Q At what points is f continuous? Homework Equations continuity: for every \epsilon > 0 there exists \delta > 0 d(f(x),f(p)) < \epsilon for all points x\inE for which d(x,p) < \delta The Attempt at a...
  49. R

    How to Prove that l is the Least Upper Bound of a Set S of Real Numbers?

    Let l \in R be the least upper bound of a nonempty set S of real numbers. Show that for every \epsilon < 0 there is an x \in S such that x > l - \epsilon I don't understand this question very well, I appreciate it if you could give me some hints. l is the l.u.b on S, therefore...
  50. R

    I'm trying to show a function has non-uniform continuity

    I'm trying to show a function has non-uniform continuity, and I can't seem to think of 2 sequences (xn) and (yn) where |(xn) - (yn)| approaches zero, where f(x) = x3. Can anyone think of two sequences?
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