What is Extension: Definition and 293 Discussions

A filename extension, file extension or file type is an identifier specified as a suffix to the name of a computer file. The extension indicates a characteristic of the file contents or its intended use. A filename extension is typically delimited from the filename with a full stop (period), but in some systems it is separated with spaces.
Some file systems implement filename extensions as a feature of the file system itself and may limit the length and format of the extension, while others treat filename extensions as part of the filename without special distinction.

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  1. 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)
  2. S

    Maximum Extension of a Massless Rod After Impact with a Falling Ball

    A ball of mass 'm' drops from a height 'h'. Which sticks to a massless hanger after striking it .. Neglect overturning. Find out maximum extension in rod, assuming that the rod is massless..
  3. @

    Extension in spring with unequal forces acting on its two ends

    Two masses m1 and m2 are connected by by spring of spring constant k. If two forces F1 and F2 acts on the two masses respectively in mutually opposite direction (i.e. outwards) what would be the extension in the spring and the acceleration of the two masses. I think that if assuming F1>F2 then...
  4. O

    So, what is the inductor from the extension cord?

    We used to buy these cheap outlet strips that came with really long wires, wound up. They said to unwind them before use because they caused fires. I thought it was inductance. But now that I think about it, there's not just a single conductor with AC in there. There's also ground and...
  5. E

    Hooke's law - Natural Extension of Spring

    Can I find out the natural extension of a spring if I am only given the mass of a block that can be put on it and the value of the spring constant? I have found x ( from the formula F = -kx ) when the block is on it but I now need to find the extension of the spring with no mass on the end. It...
  6. X

    Wave equation and odd extension with constant IC

    Solve U_xx=U_tt with c=1. Dirchlet boundary conditions U(x,0)=1 for 5<x<7 U(x,0)=0 for everywhere else U_t(x,0)=0 I know that by taken an odd extension I can get rid of the boundary condition and then solve the initial value problem using the d'alembert solution and only care for x>0...
  7. B

    MHB Continuous extension of homomorphism

    Let $T$ be a bounded normal operator and let $x$ be a member of the spectrum. Consider the homomorphism defined on the set of polynomials in $T$ and $T^{*}$ given by $h(p(T,T^*))=p(x,x^*)$ Prove that this map can be continuosly extended to the closure of $P(T,T^*)$
  8. Math Amateur

    MHB Tensor Products - D&F - Extension of the scalars

    I am attempting to understand Dummit and Foote exposition on 'extending the scalars' in Section 10.4 Tensor Products of scalars - see attachment - particularly page 360) [I apologise in advance to MHB members if my analysis and questions are not clear - I am struggling with tensor products! -...
  9. Math Amateur

    MHB Extension and contraction of I to D^-1R

    At the bottom of page 708 in Dummit and Foote (Chapter 15, Section 15.4 Localization) we find the definition of the extension and contraction of ideals. The notation is similar to I^e and I^c except that the superscripts e and c occur before the I. Can someone please help me with the latex...
  10. P

    How to determine extension of a pseudo-Riemannian manifold

    Broad title, but really a specific question that I thought should be straightforward, but got stuck. Consider the geodesics of form t=contant, r>R, in exterior SC geometry in SC coordinates. These are spacelike geodesics. If we consider this geometry embedded in Kruskal geometry, it is easy to...
  11. J

    An extension of Dot and Cross Product

    I was thinking, if exist a product (cross) between vectors defined as: \vec{a}\times\vec{b}=a\;b\;sin(\theta)\;\hat{c} and a product (dot) such that: \vec{a}\cdot\vec{b}=a\;b\;cos(\theta) Why not define more 2 products that result: \\a\;b\;sin(\theta) \\a\;b\;cos(\theta)\;\hat{d} So, for...
  12. Mandelbroth

    Sanity Check for Simple Extension Proof

    This was an exercise out of Garling's A Course in Galois Theory. Suppose ##L:K## is a field extension. If ##[L:K]## is prime, then ##L:K## is simple. I've developed a habit of checking my work for these exercises religiously (the subject matter is gorgeously elegant, so I want to do it...
  13. L

    Proving Uniformly Continuous Extension of Function ##f## in Metric Space ##E'##

    Homework Statement Let ##S\subset E## where ##E## is a metric space with the property that each point of ##S^c## is a cluster point of ##S.## Let ##E'## be a complete metric space and ##f: S\to E'## a uniformly continuous function. Prove that ##f## can be extended to a continuous function...
  14. C

    Velocity Vs. Time Graph Extension Help

    [b]1. The problem statement So I am currently working on an velocity/acceleration lab. My physics teacher requires each lab group to find an extension that goes above and beyond the question that we are supposed to answer with the lab. Each group also needs evidence to prove the extension...
  15. M

    Dense subset and extension of uniformly continuous function

    1. Homework Statement . Let ##(X,d)## be a metric space, ##D \subset X## a dense subset, and ##f: D→ℝ## a uniformly continuous function. Prove that f has a unique extension to all ##X##. 3. The Attempt at a Solution . I have some ideas but not the complete proof. If ##x \in D##, then...
  16. R

    Finding the Max Extension of a Spring: A Step-by-Step Guide

    Problem An ideal spring with spring constant 'k' is hung from the ceiling and a block of mass 'M' is attached to its lower end. The mass is released with the spring initially unstretched. Then the maximum extension in the spring is? Please tell how to do it and the final answer.
  17. G

    Potential of a dipole with actual physical extension?

    I think everybody here knows the equation that gives the potential of a point like dipole, but how does the field look like if you have e.g. a metal sphere with radius $R$ and a certain dipol moment, how does this potential look like?
  18. K

    MHB Liouville's extension of Dirichlet's theorem

    What is liouville's extension of dirichlet's theorem ? and where can I use such a theorem ? Can I apply Integration like this ? \int_0^{\frac{\pi}{2}} \cos^2(x)\sin^2(x)\,dx
  19. caffeinemachine

    MHB Degree of extension invariant upto isomorphism?

    Let $K$ be a field and $F_1$ and $F_2$ be subfields of $K$. Assume that $F_1$ and $F_2$ are isomorphic as fields. Further assume that $[K:F_1]$ is finite and is equal to $n$. Is it necessary that $[K:F_2]$ is finite and is equal to $n$?? ___ I have not found this question in a book so I don't...
  20. E

    Finding the max. extension in the spring

    finding the max. extension in the spring...! Okkay so i have to calculate the max. extension in a spring attached with two blocks of mass m and M. The box of mass M is pulled with a force F. The system (blocks of masses m1 and m2 and the mass less spring) is placed on a smooth surface...
  21. N

    Mathematics to be simply an extension of logic

    Hello, I read that many people believe mathematics to be simply an extension of logic and therefore some or all of math to be reducible to logic. I thought this was an obvious fact for the longest time. I was wondering if there was any flaw with such an argument or what else there is which...
  22. AJKing

    Young's Modulus; Extension of a wire

    Homework Statement This is from A.P. French, Vibrations and Waves, Problem 3-7 A wire of unstretched length l0 is extended by a distance of 10-3l0 when a certain mass is hung from its bottom end. If this same wire is [turned to be horizontal] and the same mass is hung from the midpoint of...
  23. S

    Proving No Solution in Extension Field

    Homework Statement Let \beta=\omega\sqrt[3]{2}, where \omega=e^{2\pi i/3}, and let K=\mathbb{Q}(\beta). Prove that the equation x^{2}_{1}+\cdots+x^{2}_{k}=-1 has no solution with x_{i} in K.Homework Equations The irreducible polynomial f is the monic polynomial of lowest degree in F[x} that...
  24. B

    Stress and Strain, load and extension

    Firstly, does a stress vs. strain graph for a material always take the same general shape as its load vs. extension graph (with the same important points, e.g. UTS, having the same shape and corresponding to the same thing)? Secondly, what do the stress-strain and load-extension graphs look...
  25. A

    How to calculate the extension of a spring?

    I usually have problems regarding Hooke's law and stuff. Please help me with the question below.. I came across it when I was doing my revision. An explanation will be appreciated. Thanks!
  26. J

    Field extension that is not normal

    I want to come up with an example of a field extension that is not normal, and seems to be difficult. All extension constructed in some obvious way tend to turn out normal.
  27. C

    Degree of a field extension

    Homework Statement Let ζ=e^((2*\pi*i)/7), E=Q(ζ), \xi=ζ + ζ^6. Show that [Q(ζ):Q(\xi)]=2. Find the generator of the galois group Gal(Q(ζ):Q(\xi)). What is the minimal polynomial of \xi. Homework Equations The Attempt at a Solution I know that [Q(ζ):Q]=6 and that Gal(Q(ζ):Q) is the cyclic...
  28. C

    MHB Find Extension of Springs: $\vec{r}$, $T$, and $x_E$

    Second question I am stuck on: A spring of natural length l with modulus of elasticity λ has one end fixed to the ceiling. A particle of mass m is attached to the other end of the spring and is left to hang in its equilibrium position under the influence of gravity. (i) Find the extension...
  29. Q

    A hint on a field extension problem?

    *** This is *not* homework. All I'd like is a push in the right direction.*** Homework Statement Let K / F be an algebraic field extension and R a ring such that F \subset R \subset K. Show that R is a field. Homework Equations (none) The Attempt at a Solution I know that every element in R...
  30. Fernando Revilla

    MHB Esteban's question at Yahoo Answers (Field extension)

    Here is a link to the question: Let E be an extension field of F and let a, b be elements of E. Prove that F(a,b)=F(a)(b)=F(b)(a)? - Yahoo! Answers I have posted a link there to this topic so the OP can find my response.
  31. Z

    Extension Spring Force Calc: Diam/Len for 5lb Proj 25-30ft

    I need to determine the correct diameter and length of a combination of 4 extension springs to use in a projectile device. The springs must be able to extend to approx 3ft, and generate enough force to propel a set of objects that are 3ft in length and have an overall weight of approx 5lbs. The...
  32. P

    MHB Integral closure in finite extension fields

    Let $K=\mathbb{Q}[\omega]$ where $\omega^2+\omega+1=0$ and let $R$ be the polynomial ring $K[x]$. Let $L$ be the field $K(x)[y]$ where $y$ satisfies $y^3=1+x^2$.Which is the integral closure of $R$ in $L$, why?
  33. FeDeX_LaTeX

    Can the Beta Function be Extended to Real Powers?

    I was looking at some integration problems the other day and I came across this identity: \int_{0}^{\frac{\pi}{2}} \sin^{p}x \cos^{q}x dx = \frac{1}{2} \mbox{B} \left( \frac{p+1}{2},\frac{q+1}{2}\right) where B(x,y) is the Beta function, for Re(x) and Re(y) > 0. From the way in which the above...
  34. A

    Open MSI File on Mac - Download Now

    I am using a MAC and have a download with a .msi file extension. Since I do not use Microsoft for my operating system, I can't open the file. Is there a download for this that I can get to open these files?
  35. O

    Prove that the extension is Normal

    Prove that the field Q(√2,√3,u) where u^2=(9-5√3)(2√2) is normal over Q. I'm supposed to show that this field is the splitting field of some polynomial over Q. u is clearly algebraic over Q. Do i just take the higher powers of u and try to find the minimal polynomial over Q or is there a...
  36. L

    Proving Finite Extension is Algebraic & Example of Converse

    Hi everyone I 'm having difficulty in proving the following theorem theorem: If L/K ( L is a field extension of K) is a finite extension then it is algebraic. Show, by an example, that the converse of this theorem is not true, in general. Can you help me to find an example in this case? Thanks...
  37. H

    Maximum Extension of a Hanging Spring

    Homework Statement A perfectly elastic spring is attached to the ceiling and a mass m is hanging from the spring. he mass is in equilibrium when the spring is stretched a distance x(o). The mass is carefully lifted and held at rest in the position where the string is nether stretched nor...
  38. T

    Find Maximum extension in the spring-Work Energy Problem

    Homework Statement The spring block system lies on a smooth horizontal surface.The free end of the spring is being pulled towards right with constant speed v_{0}=2m/s.At t=0 sec the spring of constant k=100 N/cm is unstretched and the block has a speed 1m/s to left.Find the maximum...
  39. B

    MHB Automorphisms of an extension field

    Hello, I found this question, and I was able to do the easier parts, but I'm really not comfortable with automorphisms in fields. Let f(x)=x^2 + 1 = x^2 - 2 \in Z_3[x]. Let u= \sqrt{2} be a root of f in some extension field of Z_3. Let F=Z_3(\sqrt{2}). d)List the automorphisms of F which leave...
  40. A

    Is cosmic muon lifetime extension a valid test of relativity?

    Experiments show that cosmic ray muons reach Earth surface in greater numbers than they should, unless relativistic time dilation is taken into consideration. It also seems to confirm the SR formula mathematically. However, looking at a lot of different experiment records, I have some doubts...
  41. T

    Showing a finite field has an extension of degree n

    Homework Statement Suppose F is a finite field and n > 0. Show that F has a field extension of degree n Homework Equations Tower Law. The Attempt at a Solution Let p^m be the size of F It's trivial to note by characterization that there exists a finite field G' of size...
  42. B

    Extension of Binary Connectives to n-valued Logic?

    Hi, All: Just curious as to whether there is some sort of canonical extension of the standard binary connectives: and, or, if, iff, etc. , to n-valued logic. I imagine this may have to see with Lattices, maybe Heyting Algebras, and Order theory in general. Just wondering if someone...
  43. A

    What is the best way to size an extension spring with specific requirements?

    I'm in need of an extension spring with some specific requirments: Material: Stainless Steel Diameter 0.75inch Rest Length: 5 1/2inch inside the hooks At 7 inches a forcle of 10lbs At 10 inches (full extension) a force of no more than 20lbs (As low as possible) Any idea on how to size...
  44. C

    Finding the Indefinite Integral Extension Questions

    Homework Statement ∫8x3e-cos(x4+4)sin(x4+4)dx Homework Equations Let u = cos(x4+4) The Attempt at a Solution I know the answer does not have the sin in it and only the e remains, because when the integral is found e stays unchanged. I could find somewhere online to calculate it...
  45. E

    Is (a+b)^n - (a^n + b^n) Always Less Than Zero in the Binomial Theorem?

    Thank you in advance, I need help proving or disproving this. In the binomial theorem, with a power (a+b)^n, I need to prove that a^n + b^n is greater than the rest, or in other words, (a+b)^n - (a^n + b^n).
  46. E

    Galois Theory: Degree of Q(ω)/Q & Why 6 Basis Vectors?

    So if we have an extension of E of F, then we can consider E as a vector space over F. The dimension of this space is the degree of the field extension, I think most people use [E:F]. This is correct in most people's books, right? Defining \omega = cos (2\pi /7) + i sin (2\pi / 7) Why...
  47. S

    Exploring Axiom of Extension: Naive Set Theory by P.R Halmos

    I am reading Naive set theory by P R Halmos. He says that "The axiom of extension is not just a logically necessary property of equality but a non-trivial statement about belonging." The example for that is "Suppose we consider human beings instead of sets, and change our definition of...
  48. C

    Can an Extension Spring Reach 32 Inches While Unloaded and Support 30-40 lbs?

    Is it possible for an extension spring to be 20 inches long while unloaded, 32 or so inches long fully extended(12" max displacement), and have an initial load of 30-40 lbs? All other properties are virtually not important. If so, where could I buy them?
  49. I

    Field extension, properties,proof

    Let F be a field of characteristic 0. Let f,g be irreducible polynomials over F. Let u be root of f, v be root of g; u,v are elements of field extension K/F. Let F(u)=F(v). Prove (with using basic polynomial theory only, without using linear algebra and vector spaces): 1) deg f = deg g (deg f...
  50. K

    Picard-Vessiot Extension over a Differential Field?

    Given a differential field F and a linear algebraic group G over the constant field C of F, find a Picard-Vessiot extension of E of F with G(E/F)=G: This isn't homework, just something I saw in a book that I was curious about. The author says that this can be shown but doesn't illustrate how...
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