What is Domain: Definition and 741 Discussions

A domain name is an identification string that defines a realm of administrative autonomy, authority or control within the Internet. Domain names are used in various networking contexts and for application-specific naming and addressing purposes. In general, a domain name identifies a network domain, or it represents an Internet Protocol (IP) resource, such as a personal computer used to access the Internet, a server computer hosting a website, or the web site itself or any other service communicated via the Internet. In 2017, 330.6 million domain names had been registered.Domain names are formed by the rules and procedures of the Domain Name System (DNS). Any name registered in the DNS is a domain name. Domain names are organized in subordinate levels (subdomains) of the DNS root domain, which is nameless. The first-level set of domain names are the top-level domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains com, info, net, edu, and org, and the country code top-level domains (ccTLDs). Below these top-level domains in the DNS hierarchy are the second-level and third-level domain names that are typically open for reservation by end-users who wish to connect local area networks to the Internet, create other publicly accessible Internet resources or run web sites.
The registration of these domain names is usually administered by domain name registrars who sell their services to the public.
A fully qualified domain name (FQDN) is a domain name that is completely specified with all labels in the hierarchy of the DNS, having no parts omitted. Traditionally a FQDN ends in a dot (.) to denote the top of the DNS tree. Labels in the Domain Name System are case-insensitive, and may therefore be written in any desired capitalization method, but most commonly domain names are written in lowercase in technical contexts.

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  1. tworitdash

    A Spectral domain double integral with singularities

    The integral looks like Y_{mut, mn} = -j^{m+n}nm \int_{-\infty}^{\infty}\int_{-\infty}^{\infty} \frac{2 ab (k^2 - k_x^2) \sin^2(\frac{k_yb}{2}) \cos^2(\frac{k_xa}{2})}{\omega \mu k_z (\frac{k_yb}{2})^2 [(n\pi)^2 - (k_xa)^2][(m\pi)^2 - (k_xa)^2]} dk_x dk_y Here, k_z = -1j \sqrt{(-(k_0^2 -...
  2. S

    [AC Circuit] How do we convert from the time domain to the phasor domain?

    In this example, We need to covert e2 & e5 to a form with imaginary number . we will obtain e2=j10 & e5=20 Can anyone explain how we got this?
  3. E

    B Showing that formulae are invariant for all values in the domain

    I was just thinking about this and couldn't decide whether it was a silly question or not, so naturally I thought I might ask. It was partly prompted by one of the questions asked in the homework section. Every physical law I can think of is "self-correcting" if you substitute negative values...
  4. V

    Python Phase shifting a measured signal directly in time domain

    I need to perform a phase shift for a measured time domain signal. The signal consists of around 1000 points. I wrote an algorithm for this in Python a while ago and it seems to work as intended, but now I noticed that the algorithm is actually unexpectedly slow. Is it so that phase shifting is...
  5. opus

    Using the Law of Sines - Getting a Domain Error on my Calculator

    So we'd like to find leg C. But we can't use Law of Cosines yet so we will use Law of Sines. We can easily find the length of A and this is ##\sqrt{13}##. With some geometry we can see that ##\angle a = 53.1##. We can now use Law of sines. $$\frac{\sin(a)}{A} = \frac{\sin(b)}{B}$$ We want to...
  6. D

    Double integral domain with absolute value

    D={(x,y)∈ℝ2: 2|y|-2≤|x|≤½|y|+1} I am struggling on finding the domain of such function my attempt : first system \begin{cases} x≥2y-2\\ -x≥2y-2\\ x≥-2y-2\\ -x≥-2y-2 \end{cases} second system \begin{cases} x≤y/2+1\\ x≤-y/2+1\\ -x≤y/2+1\\ -x≤-y/2+1\\ \end{cases} i draw the graph and get the...
  7. D

    I The domain of a multivariable function

    hey there I'm struggling on finding the domain of the following function log (xy2)+x2y) I then do xy(y+x)>0 but then i don't know what to do with xy one attempt \begin{cases} y+x>0\\ x>0\\ y>0 \end{cases} union \begin{cases} y+x<0\\ x<0\\ y<0 \end{cases} but this doesn't lead to the...
  8. P

    MHB Infinite Natural Numbers: First-Order Logic Formula Explained

    There are an infinite number of natural numbers. Why is that? Well this follows from the following facts: (i) There is at least one natural number. (ii) For each natural number there is a distinct number which is its successor, i.e., for each number $x$ there is a distinct number $y$ such that...
  9. S

    MHB Maximizing Probability of Finding Explosive Device in Bounded Domain

    I am trying to solve the following problem. Let us take a bounded domain $S$ in which an explosive device is located. A team is deployed to locate and disable the device before a certain time T (when the device explodes). There are several criteria to be satisfied: 1. The domain $S$ is...
  10. baldbrain

    Range of f(x): Intersection of h(x) and g(x) Ranges

    ## Let~~f(x)=h(x)+g(x) , where~~h(x)=10^{\sin x}~~and~~g(x)=10^{\csc x}## ##Then,~~D_f = {D_h}\cap {D_g}## ##Clearly,~~D_h=ℝ~~and~~D_g=ℝ-\{nπ|n∈ℤ\}## ##∴~~D_f =ℝ-\{nπ|n∈ℤ\}## After considering the new domain, the range of ##\sin x## in ##10^{\sin x}## is ##[-1,1]-\{0\}## Therefore, the range of...
  11. Van Ladmon

    I Conflict of domain and endpoints in Noether's theorem

    In the derivation of energy conservation, there is the transformation ##q(t)\rightarrow q'(t)=q(t+\epsilon)##, whose end points are kind of fuzzy. The original path ##q(t)## is only defined from ##t_1## to ##t_2##. If this transformation rule is imposed, ##q'(t_2-\epsilon)=q(t_2)## to...
  12. karush

    MHB 6.2.15 Find the domain of each function.

    $\textsf{6.2.15 Find the domain of each function.}$ (a) $f(x)=\dfrac{1-e^{x^2}}{1-e^{1-x^2}}$ set the denominator to zero and solve $1-e^{1-x^2}=0$ then $x=1,-1$ from testing the domain is $(-1,1)$(b) $f(x)=\dfrac{1+x}{e^{ \cos x}}$ set $e^{\cos x}=0$...
  13. M

    I What if the Jacobian doesn't exist at finite points in domain of integral?

    Consider a one to one transformation of a ##3##-##D## volume from variable ##(x,y,z)## to ##(t,u,v)##: ##\iiint_V dx\ dy\ dz=\int_{v_1}^{v_2}\int_{u_1}^{u_2}\int_{t_1}^{t_2} \dfrac{\partial(x,y,z)}{\partial(t,u,v)} dt\ du\ dv## ##(1)## Now for a particular three dimensional volume, is it...
  14. TytoAlba95

    How many amino acid residues are there for the transmembrane domain?

    Total no. of amino acid in each transmembrane domain = 4 nm/ 0.15 nm +1 =27.66 Total no. of amino acids in 7 transmembrane domains = 27.66 x 7 = 193.62 ≈ 190 Hence option d. Is my approach correct?
  15. J

    Finding the range of a function when checking if it is bijective

    To check if it is injective : ##h'(x) = 3(x^2-1)## ##\implies h'(x) \geq 0## for ##x \in (-\infty, -1]## Thus, ##f(x)## is increasing over the given domain and thus is one-one. To check if it is surjective : Range of ##f(x) = (0, e^4]## but co-domain is ##(0, e^5]## thus the function is into...
  16. F

    B Domain and imaginary numbers

    Consider the function sqrt(x). What is the domain of this function? Is it all real positive numbers? This is what I was taught in high school, but I was also taught that plugging in -1 would give an answer of i. So if the function takes negative inputs, shouldn’t they be part of the domain?
  17. Behrouz

    A Finding a specific amplitude-frequency in the time domain

    Hello, I have a signal and got the FFT result of that. I have shown them both below along with the MATLAB code. May I ask if there is any method to find the time zone(s) in the signal that a specific frequency has(have) happened? The reason I'm asking this is that I want to specify the time...
  18. V

    A Function and its Domain, Codomain and Image

    Homework Statement Find a function where the domain is integers, codomain is real numbers, and image isn't equal to codomain. Homework EquationsThe Attempt at a Solution I know that it means that when I plug in an integer I will obtain a real number, but how do I make it so that the image is...
  19. G

    Modeling a mass hanging by a spring: motion in 3D time/freq domain

    Hello everyone, I am new here, and wondering if anyone would have some knowledge on a current problem I have been working on. I am trying to create time- and frequency domain 3D models of an object hanging using a spring from a fixed point within a shell. I am trying to figure out how the...
  20. Telemachus

    MPI: domain decomposition strategy

    Hi. I'm trying to parallelize my code. I am new at MPI, I'm learning the basics. I want to use a domain decomposition strategy in my code. I've been reading a bit, and wanted to use this subroutine to exchange points between neighbors. I've started by trying to modify a code presented by Gropp...
  21. H

    Harmonics in the "electrical" domain

    There is some controversy as to why the spectral content of vinyl records contain frequency "information" above what the analog tape recorder was capable of capturing. A thought experiment: If I have a piano that has a key which plays 15khz (primary freq. of that key's piano string), what...
  22. jedishrfu

    Public Domain and Copyrights of 1923

    ArsTechnica on Copyright expiration and the legal pitfalls around it: https://arstechnica.com/tech-policy/2019/01/a-whole-years-worth-of-works-just-fell-into-the-public-domain/
  23. D

    Determine a transfer function in the `s` domain and the response to a ramp input

    1. A process can be represented by the first order equation ##4\frac{dy(t)}{dt}+y(t)=3u(t)## Assume the initial steady state is steady (y=0 at t=-0) (a) Determine the transfer function of this process in the s domain (b) If the input is a ramp change in u(t)=4t, determine the value of...
  24. M

    Mathematica Plotting 0.3 on ListPlot with Variable Domain

    Hi PF! I type the following into Mathematica: domain = -10; ListPlot[{0.3}, PlotMarkers -> {{"\[LongDash]", Large}}, PlotRange -> {{0, 5.5}, {-10, 200}}] And notice we see the plot 0.3. But, now let domain = 0. Notice now we can't see 0.3. Does anyone know how to fix this?
  25. Krushnaraj Pandya

    The minimum of a function in a given domain

    Homework Statement The operating cost of a truck is 12+(x/6) per km, when the truck travels x km/hr. If the driver earns 6 rupees (*or whatever currency your country has) per hour, what is the most economic speed to operate the truck on a 400 km road? Also, due to weather, the truck can travel...
  26. md nabil

    A Solving the Laplace equation over a trapezoidal domain

    can anyone help me on how I can map an isosceles trapezoid onto a rectangular/square domain.Actually I need to solve Laplace equation(delta u = 0) over this isosceles trapezoidal domain. Schwarz Christoffel mapping may help me. But can anyone give me any hint on this mapping procedure?
  27. karush

    MHB What are the domain and range for the inverse function $f^{-1}$ of $f$?

    Find the inverse function $f^{-1}$ of $f$. Find the range of $f$ and the domain and range of $f^{-1}$ $$f(x)=5 \sin x +2; \quad -\frac{\pi}{2}\le x \le \frac{\pi}{2}$$ exchange x for y and solve for y \begin{align*}\displaystyle x&=5\sin y + 2 \\...
  28. K

    Find Domain of f(x,y)=sqrt(5xy-2y^2)

    Homework Statement Find the domain of f(x,y)=sqrt(5xy-2y^2) Homework EquationsThe Attempt at a Solution As far as I understand it's all about solving inequalities when you have this kind of problem. The problem doesn't state it is in ℝ2 but I'm pretty sure it is. So no negative numbers under...
  29. R

    MHB Finding Domain for Natural Log with Exponent f(x)=ln(x^2−5x)

    I just asked a similar question, but I got help for that one, and now I am stumped again. I need to find the domain for f(x) = ln(x^2-5x) What's confusing me is how to deal with the exponent. I can't think of a way to get around it.
  30. R

    MHB Finding the Domain of a Logarithmic Function f(x) = log_5(8 - 2x)

    I need to find the domain of f(x) = log5(8 - 2x). I am not sure if I could find this by doing a inequality equation, but I think my professor wants us to do it on a number-line anyway. I'm sorry, but I am not sure where to start.
  31. T

    MHB Domain & Range: Find It on a Graph

    How do you find the domain and range of a graph?
  32. jedishrfu

    Domain of Science on Quantum Computing

    In this DOS video, he talks about 5 common misconceptions on QUantum COmputing:
  33. Math Amateur

    MHB Definition of a Euclidean Domain ....

    In the book "The Basics of Abstract Algebra" Bland defines a Euclidean Domain using two conditions as follows: In the book "Abstract Algebra"by Dummit and Foote we find that a Euclidean Domain is defined using only one of Bland's conditions ... as follows:What are the consequences of these...
  34. binbagsss

    I Modular Forms-Fundamental Domain

    Apologies if this is a stupid question, but is the fundamental domain unique? And what exactly is the definition of a cusp- a quick google tells me it is 'where two curves meet', so looking at the fundamental domain,I would say ##\omega=\exp^{\frac{2\pi i}{ 3}} ## and ##\omega*## are? thanks
  35. jedishrfu

    Great Domain of Science Video on Movie Sci Fi

    Domain of Science reviews science in sci fi movies: The reviewer talks about how physics is misused in movies and cringes at some of the funny movie moments where they got physics wrong.
  36. A

    MHB What is the Numerical Domain of an Algorithm and How is it Determined?

    Hi everyone. My book (Smith's "An Introduction to Goedel's Theorems") defines the numerical domain of an algorithm as the set of naturals that, when input individually to the algorithm, result in its "working", that is to terminate and output some result. In the book it is also stated that any...
  37. binbagsss

    Modular Forms, Fundamental Domain Question

    Homework Statement My question is below it makes more sense there, after I have gave my interpretation of the definition of the fundamental domain to confirm my understanding Homework Equations The fundamental domain is defined as: 1) Every point in H is equivalent to a point in F. 2)...
  38. opus

    Domain and Range of a Function and Its Inverse- Polynomials

    Homework Statement Consider the function ##f\left(x\right)=\sqrt {x+2}##. Determine if the function is a one-to-one function, If so, find ##f^{-1}\left(x\right)## and state the domain and range of ##f\left(x\right)## and ##f^{-1}\left(x\right)## Homework Equations N/A The Attempt at a...
  39. SemM

    I How to find admissible functions for a domain?

    Hi, in a text provided by DrDu which I am still reading, it is given that "the momentum operator P is not self-adjoint even if its adjoint ##P^{\dagger}=-\hbar D## has the same formal expression, but it acts on a different space of functions." Regarding the two main operators, X and D, each has...
  40. S

    A Heat equation on infinite domain

    Hi everyone, I'm reading this paper about the solution of the heat equation inside an infinite domain: https://ocw.mit.edu/courses/mathematics/18-303-linear-partial-differential-equations-fall-2006/lecture-notes/fourtran.pdf 1) Please let me know if the following discussion is correct. The...
  41. SemM

    A How to find the domain of functions of an operator

    Hi, I have a strange nonlinear operator which yields non-Hermitian solutions when treated in a simple ODE, ##H\Psi##=0. It appears from a paper by Dr Du in a different posting, that an operator can be non-self-adjoint in one domain, but be self-adjoint in another domain defined by the interval...
  42. D

    B Domain and the codomain of a composite function

    So, I'm a bit confused. The thing is, basically, all elementary functions are of the form ƒ:ℝ→ℝ. So the domain is ℝ and so is the codomain. However, if we have a function ƒ:ℝ→ℝ, given with f(x) = √x, it's domain is now x≥0. So, is the domain of this function ℝ or [0,+∞>? Also, let's say we have...
  43. lawsonfurther

    A A bit of clarification on the domain of a composite function

    Recently when I reviewed something about the composite function for my calculus exam, I remembered I had been thinking a question for quite a long time (maybe I was going into a dead end) since I was in high school. I was thinking whether f(x)=1/(1/x) and g(x)=x are the same function or not. It...
  44. D

    I Domain of the identity function after inverse composition

    Hi, I'm struggling to understand something. Does domain restriction work the same way for composition of inverse functions as it does for other composite functions? I would assume it does, but the end result seems counter-intuitive. For example: If I have the function f(x) = 1/(1+x), with...
  45. M

    MHB What is the domain of the rational function f(x) = 2/(x - 3)?

    Find the domain of f(x) = 2/(x - 3). 1. Are we looking for the domain of f or f(x)? 2. Solution Set x - 3 = 0 and solve for x. x - 3 = 0 x - 3 + 3 = 3 x = 3 Let D = domain D = ALL REAL NUMBERS except for x = 3. Yes? P.S. Does x = 3 mean there is a hole at the point (3, 0) for this...
  46. shihab-kol

    B Why Does tan x Have This Domain?

    I found in a book that the domain of tan x was {(2n+1)π/2 , n∈I} The graph however shows that for every value of x , the function takes on a value .So, why is the domain like this?
  47. M

    Transforming Piecewise Functions

    Homework Statement The piece wise function is -x-2, x<-1 x^2-3x, -1≤ x ≤5 3x+5, x>5 The problem is to transform the function with...
  48. M

    I Measuring Thickness and Refractive Index with Fourier Domain OCT

    Hi, I would like to know how one can simultaneously measure the thickness and refractive index of a sample using Fourier Domain OCT. I have a glue layer on a glass microscope slide and I've calculated the thickness of the glue layer, but I'm unsure of how to the refractive index of the glue. Any...
  49. R

    MHB Find the domain of the function .

    1) Given that the range of function f(A) = \frac{1 + sinA}{1 - sinA} is { 0,1,3} . Find the domain of the function .
  50. C

    A Laplace equation- variable domain

    Hi, I need to solve Laplace equation ## \nabla ^2 \Phi(z,r)=0## in cylindrical coordinates in the domain ## r_1<r<r_2 ##, ## 0<z<L ##. The boundary conditions are: ## \left\{ \begin{aligned} &\Phi(0,r)=V_B \\ &\Phi(L,r)=V_P \\ & -{C^{'}}_{ox} \Phi(x,r_2)=C_0 \frac{\partial \Phi(x,r)}{\partial...
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