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. ohwilleke

    I Domain of Applicability of Post-Newtonian Formalism

    The parameterized post-Newtonian formalism is an approximation of general relativity that is easier to calculate with that applies in "weak" gravitational fields where objects are "slow" moving. My question is: "What is the approximate domain of applicability of the post-Newtonian formalism?"...
  2. Biscuit

    Average velocity when the interval has a domain

    Homework Statement If a ball is thrown into the air with a velocity of 40 ft/sec, its height (in feet) after t seconds is given by s(t) = 40t -16t^2. Find the average velocity, vAV (t), of the ball over the time interval (t, 2), for 0 < t < 2. Homework Equations change of x/change of...
  3. Math Amateur

    MHB The Integers as an Ordered Integral Domain .... Bloch Theorem 1.4.6 ....

    I am reading Ethan D. Bloch's book: The Real Numbers and Real Analysis ... I am currently focused on Section 1.4: Entry 2: Axioms for the Integers ... In this section Bloch defines the integers as an ordered integral domain that satisfies the Well Ordering Principle ... rather than defining the...
  4. Math Amateur

    I Integers as an Ordered Integral Domain .... Bloch Th. 1.4.6

    I am reading Ethan D. Bloch's book: The Real Numbers and Real Analysis ... I am currently focused on Section 1.4: Entry 2: Axioms for the Integers ... In this section Bloch defines the integers as an ordered integral domain that satisfies the Well Ordering Principle ... rather than defining the...
  5. Oats

    I Must functions really have interval domains for derivatives?

    Nearly every analysis reference I come across defines the derivative for functions on an open interval ##f:(a, b) \rightarrow \mathbb{R}##. I understand that, in constructing the definition of ##f## being differentiable on a point ##c##, we of course want it to first be a point it's domain, so...
  6. M

    MHB Domain of Function Involving Roots

    Section 3.1 Question 2dFind the domain of the function. Let CR = CUBE ROOT s = CR{3t + 12} Because it is a cube root, I say the domain is ALL REAL NUMBERS.
  7. esha

    The graph of sin inverse (sin x) after the domain of (- pi/2, pi/2)

    the graph of sin inverse (sin x) between the domain of ( -pi/2,pi/2) is y = x. but after it crosses that domain of course the expression won't be the same anymore because sin inverse has its principle value as ( - pi/2, pi/2) due to sin x many to one natured function. now the way these...
  8. M

    MHB What is the domain for variables with cube roots?

    Specify the domain of each variable. 1. ax + b Here x can be any integer. In that case the domain is R, where R is ALL REAL NUMBERS. 2. ax^(1/3) + b Let x^(1/3) be the cube root of x. Let D = domain x^(1/3) is > or = 0 [x^(1/3)]^3 > or = 0^(1/3) x > or = 0 D = {x| x > or = 0} Is any...
  9. M

    MHB Why Restrict the Domain for Certain Functions?

    Why must we restrict the domain of certain functions to solve the problem?
  10. M

    MHB Domain of Rational Function: What is the domain of the given rational function?

    Find the domain of the rational function. y = (6x^2 + 11x + 4)/(3x + 4) Solution: Let denominator = 0 and solve for x. 3x + 4 = 0 3x = -4 x = -4/3 This means the domain is any real number except for x = -4/3. When x = -4/3, the denominator becomes 0, which is undefined. Correct?
  11. Saracen Rue

    B Domain of Derivatives: Is f'(x)<=f(x)?

    Just a quick question - Is it true that the domain of ##f'(x)## will always be less than or equal to the domain of the original function, for any function, ##f(x)##?
  12. M

    MHB What is the domain for the expression 4/[(t - 1)•sqrt{t}]?

    Precalculus by David Cohen, 3rd Edition Chapter 1, Section 1.3. Question 5b Specify the domain. 4/[(t - 1)•sqrt{t}] Solution: Set (t - 1) = 0 and solve for t. t - 1 = 0 t = 1 For sqrt{t}, the radicand cannot be negative. Domain: t can be any number except 1; t > or = 0. Yes?
  13. M

    MHB What is the domain for ax^(1/3) + b?

    Precalculus by David Cohen, 3rd Edition Chapter 1, Section 1.3. Question 3b. Specify the domain. ax^(1/3) + b Solution: x^(1/3) means the cube root of x. Since there is a radical here, I will say the domain is the radicand > or = 0. So, x > or = 0. Yes?
  14. T

    Magnetic alignment of steel question

    Hi, I have a question about steel, for instance, silicon steel used in magnetic cores. I was wondering about how Iron magnetises: can you align the grains/domains and heat treat it [or anything], so that it responds differently to flux one way then the other direction? For example, say you...
  15. binbagsss

    A Valence formula- fundamental domain- why truncation height?

    In the proof of the valence formula you integrate ##f'(t)/f(t)## around the boundary of the fundamental domain, with some modifications such as : - omitting the points ##i, \omega ## - since equivalence is allowed on the boundary, modifying as needed to ensure such points that are equivalent...
  16. Vital

    Find the domain of arccsc(e^2x)

    Homework Statement Hello! Seems I have forgotten how to work with such values. Please, help me to find the correct approach to this type of exercises. Homework Equations The task is to find the domain of the function: f(x) = arccsc(e2x) The Attempt at a Solution The answer in the book is [0...
  17. R

    MATLAB Frequency domain filtering in Matlab

    I am trying to implement several filters in Matlab for Fourier domain filtering. They are the cosine, Shepp-Logan, and Hann/Hamming window filters. These filters are defined as multiplying the ramp filter by the cosine function, sinc function, and Hann/Hamming windows respectively. This is how...
  18. Mr Davis 97

    Showing that a ring is an integral domain

    Homework Statement Show that ##\mathbb{Z} [\sqrt{d}] = \{a+b \sqrt{d} \ | \ a,b,d \in \mathbb{Z} \}## is an integral domain Homework EquationsThe Attempt at a Solution Do I have to go through all of the axioms to do this? For example, do I have to show that it is an abelian group under...
  19. Mr Davis 97

    In an integral domain deg(pq) = deg(p) + deg(q)

    Homework Statement Let ##R## be an integral domain and ##p_1(x),p_2(x) \in R[x]## with neither equal to ##0##. Show that the degree of ##p_1(x)p_2(x)## is the sum of the degrees of ##p_1(x)## and ##p_2(x)##. Homework EquationsThe Attempt at a Solution Here is my attempt. Let ##p_1(x) = a_n...
  20. F

    I D'Alembert's Solution – Domain of dependence

    When considering the Wave equation subject to initial conditions as follows… …then D'Alembert's solution is given by (where c is wave speed): I'd like to understand physically how this formula allows us to know the value of u (where u is the height of the wave, say) at some point (x0,t0)...
  21. M

    MHB Why is the domain of ax^(1/3) + b equal to all real numbers?

    Find the domain. ax^(1/3) + b I understand that a and b are constants here. I also know that x^(1/3) is equivalent to cube root{x}. What I do not understand is why the answer is ALL REAL NUMBERS.
  22. R

    A Converting Partial Differential Equations to Frequency Domain

    Hello All, I would like to convert a partial diff equation in time domain into frequency domain, however there is a term of the form: Re(∇(E1.E2*) exp(j[ω][/0]t)) where E1 and E2 are the magnitudes of the electric field and [ω][/0] is the angular frequency. Can someone please help me to...
  23. Arceus74

    How does an magnetic domain align?

    I have these assumptions please correct me if they are wrong:) 1)A particle has mass,electric charge and magnetic moment. 2)Somehow in a atom the net magnetic moment of all the particles including protons and electrons get canceled out and becomes neutral.However for half-filled electron shells...
  24. L

    Interval notation of function's domain question

    Homework Statement find domain f(x)= ## \frac{\sqrt{x^2-x-6}}{x-5} ## Homework EquationsThe Attempt at a Solution [/B] Well, one sees that x ≠5 and then we further investigate the dividend portion where the under-the-root expression ≥ 0 We can graph the parabola, and find the zeroes. Then...
  25. SSequence

    B Probability Distributions (Countably Infinite domain)

    Suppose we have a "particle" which can be at some position x∈N (where N={0,1,2,...}). The probability that the particle is at position x can be written as: P(x) = 1/(2x+1) Now suppose we have two particles p1 and p2.To keep things simple, assume that the individual probability distribution for...
  26. Cocoleia

    Frequency domain and mesh currents

    Homework Statement Homework EquationsThe Attempt at a Solution So far I was able to transform each element into the frequency domain: I am just unsure how to work with the dots to find the mesh currents. Can someone explain? Thanks.
  27. Math Amateur

    MHB Understanding Irreducible Elements in Integral Domains - Peter's Questions

    Joseph A. Gallian, in his book, "Contemporary Abstract Algebra" (Fifth Edition) defines an irreducible element in a domain as follows ... (he also defines associates and primes but I'm focused on irreducibles) ... I am trying to get a good sense of this definition ... My questions are as...
  28. Math Amateur

    I Definition of an irreducible element in an integral domain

    Joseph A. Gallian, in his book, "Contemporary Abstract Algebra" (Fifth Edition) defines an irreducible element in a domain as follows ... (he also defines associates and primes but I'm focused on irreducibles) ... I am trying to get a good sense of this definition ... My questions are as...
  29. ntran26

    A Inversion of Division of Bessel Functions in Laplace Domain?

    Hello all, I am trying to take the inversion of this function that is in Laplace domain. I've tried using a wolfram alpha solver, and I know I can probably use stehfest algorithm to numerically solve it but wanted to know if there was an exact solution. the function is...
  30. H

    A scalar on a semi-infinite domain with source and sink

    Hi everyone, I've been looking at a problem that seems simple at first, but appears to be deceptively difficult (unless I'm missing something). 1. Homework Statement I've been looking at a problem that involves the diffusion of a scalar quantity, ##q(x)##, on the semi-infinite domain, ##\leq...
  31. J

    A Boltzmann's constant validity domain

    Boltzmann's constant appears in many distributions of statistical physics, and I have been left confused whether it is always the same constant with certainty. For example, suppose we define the Boltzmann's constant so that it is the constant that works with certainty for gases, i.e. it gives...
  32. cathal84

    Determining the domain and range of multi-variable function

    Homework Statement f(x,y) = 1/y^2-x find the domain of f. Given c ∈ R \ {0} find (x, y) ∈ R 2 such that f(x, y) = c. Finally determine the range of f. Homework Equations I know that the domain of the function is anywhere that the function is defined. The Attempt at a Solution in the case of...
  33. N

    I Electron Spin vs Domain Creation in Permanent Magnets

    I am having difficulty thinking through how a ferromagnetic substance is permanently magnetized. I think I understand that when for example a sample of iron is heated above it curie temperature and then exposed to an external magnetic field , the sample will become permanently magnetized. The...
  34. Z

    MHB How to find the Domain , Range , matrix for the relation R

    can anyone help me ? i have a homework and i did't find any answer for it the question is find the Domain , Range , matrix and the digraph for the relation R a ) A = { 1,2,3,4,8 } = B , aRb if and only if a=b b) A = { 1,2,3,4,6 } =B , aRb if and only if a multiple of b
  35. C

    Converting phasor to time domain

    Homework Statement Homework EquationsThe Attempt at a Solution I am extremely confused. Everywhere I go to look on how to convert phasors into time domain I get a different answer. I am trying to convert -j to the time domain. My notes says to find the Im(phasor). I have explained in the...
  36. G

    I Domain of single-valued logarithm of complex number z

    Hello. Let's have any non-zero complex number z = reiθ (r > 0) and natural log ln applies to z. ln(z) = ln(r) + iθ. In fact, there is an infinite number of values of θ satistying z = reiθ such as θ = Θ + 2πn where n is any integer and Θ is the value of θ satisfying z = reiθ in a domain of -π <...
  37. jtbell

    Using own domain name for e-mail

    I'm switching my personal e-mail to an address @ the domain name that I use for my web site, so that in the future I can switch e-mail providers by pointing the address to the new provider instead of having to tell everyone a new address. Of course, this time I still have to tell everyone, but...
  38. B

    Understanding N-Stages of FFT & DFT Formula for Frequency Domain

    1) How many stages are in N numbers for a FFT? I know N=8 has 3 stages and N=4 has 2 stages ? 2) The DFT formula converts a signal from the time domain into the frequency domain. Is this done by comparing x[n] against signals known as sinusoidal basis functions? are e-j2 pi kn/N sinusoidal...
  39. D

    Fatigue analysis in the frequency domain

    Assuming that a TLP platform is examined and the wave forces acting on the tendons of the mooring lines are presented in RAOs (as a function of wave frequency). Using Jonswap spectra for North sea (i.e peakness factor equal to 3.3) we can obtain Hs (significant wave height); Tp (peak period) and...
  40. C

    Converting phasor back into time domain

    Homework Statement Find Amplitude of Steady-state voltage across capacitor Homework EquationsThe Attempt at a Solution I'm at the very last step of changing it back into the time domain to obtain my ampltiude. I was planning on getting it into the form a + bj, then using trigonometry and...
  41. C

    What is the Domain of ln(x^2 + y^2)?

    Homework Statement for the domain of ln (x^2 + y^2 ) , it it given in my notes that the ans is x ≠ 0 and y ≠ 0 IMO , it's wrong to give x ≠ 0 and y ≠ 0 , because the meaning of x ≠ 0 and y ≠ 0 is that x and y can't be 0 all the times so just leave the ans (x^2 + y^2 ) > 0 , will do ...
  42. C

    Domain of ln(x+y) | x ≠ 0, y ≠ 0 or (x,y) ≠ (0,0)?

    Homework Statement in my notes , it's stated that the domain of ln(x+y) is x+y> 0 ... Can i write it as x ≠ 0 , y ≠ 0 ? Or should i write it as (x,y) ≠ (0,0) ?(x,y) ≠ (0,0) represent x , and y can be 0 at the same time ? Whereas x ≠ 0 , y ≠ 0 only represent x can't be equal to 0 ? for...
  43. C

    Domain of z= ln ( (x^2) + (y^2) )

    Homework Statement the given ans is x ≠ 0 , y ≠ 0 , the ans given is x ≠ 0 , y ≠ 0 . I don't understand the ans , why the author leave the ans like this ? IMO , x can be 0 as long as y not = 0 y also can be 0 , as long as x not = 0 ,by giving the ans in x ≠ 0 , y ≠ 0 , the author just rule out...
  44. A

    Sketch Domain of F(x,y)

    Homework Statement Suppose we have f(x,y) = ∑(x/y)^n , n goes from 0 to infinity. What is the domain on the xy plane? Sketch it. 3. Attempt I was thinking to look at the scenario if x/y is less than 1, or bigger than 1. If the ratio is less than 1, then I can use an idea from geometric series...
  45. T

    I Equations for functions in the complex domain

    When working in the complex domain (##z = x + iy##), how does one write the equation of a line? I have attached a problem I was working on (and have the solution), but am curious as to why the definition of a line is given by ##ax + by = c##. Are not ##x## and ##y## also variables that take on...
  46. S

    MHB Find the domain and range of the following function f(x)=x-2/sqrt(10-2x)

    Hello, I'm sorry for registering to the the boards and immediately posting a new thread. I did use the search function to try and find a similar thread that addresses the issue I'm having but nothing jumped out at me and frankly I'm so green that I wouldn't know what to look for. This is my...
  47. Jezza

    Domain of a discrete fourier transform

    Homework Statement The (computing) task at hand is to take a function f(x) defined at 2N discrete points, and use the Discrete Fourier Transform (DFT) to produce F(u), a plot of the amplitudes of the frequencies required to produce f(x). I have an array for each function holding the value of...
  48. caters

    What is the Domain of the Area Function for a Rectangle on a Parabola?

    Homework Statement A rectangle has one vertex in quadrant I at the point (x,y) which lies on the graph of y = 2x^2 and another vertex at the point (-x, y) in the second quadrant and the other vertices on the x-axis at (-x, 0) and (x, 0) What is the domain of the area function? y = 2x^2 = w l...
  49. R

    Understanding Electromagnetic/X-Ray Pulse in Time and Frequency Domain

    Dear All, Suppose we have a electromagnetic/x-ray pulse with fixed energy with finite line width. I want to know the schematic of a plot how it looks in time- and frequency-domain? I think I understand in time domain: there will a straight vertical line on plotting intensity vs time in x-axis...
  50. J

    Is there physics knowledge hidden to public domain?

    I was wondering if our governments hide us some knowledge. Military industry for sure, but What about physics? Is all the knowledge public? I include in my question biology. I am sure that the richest people in this planet are investing right now hundreds or thousands of billions researching...
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