What is Pair: Definition and 399 Discussions

An au pair (; plural: au pairs) is a helper from a foreign country working for, and living as part of, a host family. Typically, au pairs take on a share of the family's responsibility for childcare, and receive a monetary allowance for personal use. Au pair arrangements are often subject to government restrictions which specify an age range usually from 18 - 26 years of age, both male (BroPair) and female AuPairs are avaliable. The au pair program is considered a form of cultural exchange that gives the family and the au pairs a chance to experience and learn new cultures.
Arrangements differ between Europe, where the concept originated, and North America. In Europe, au pairs are only supposed to work part-time, and they often also study part-time, generally focusing on the language of the host country. In the United States, they may provide full-time childcare. In 1969, the European Agreement on Au Pair Placement was signed, and it came into force in 1971. Au pair companies in the United States have significant non-refundable fees once the au pair arrives in the country. The contract does not guarantee childcare, despite many families' reliance on the program.
Unlike many other types of domestic assistants, the au pair is considered a part of the host family and not merely an employee. In some countries the au pair wears a uniform, but more commonly the au pair only follows the host family's dress code and wears attire appropriate for the work description, typically including a protective apron.

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  1. A

    Find the tension force in each pair

    Homework Statement You are presented with a circumstance in which three children are playing on a frozen pond. The three small children of mass 20.00 kg, 24.00 kg, and 16.00 kg, respectively, hold hands, and are pulled across a smooth frozen pond by a larger boy on skates, who pulls a...
  2. T

    A Lower limit in pair production

    In pair production, if the photon has an energy greater than 1.02 MeV, why can't a lower energy photon remain after creation of the electron-positron pair? For example, if you have a 10 MeV photon interacting with a carbon nucleus, why are the stated products of pair production the carbon...
  3. haushofer

    A Hawking radiation: pair production?

    Dear all, I'm trying to understand the firewall controversy and the role of Hawking radiation in this. To make things concrete, I'll use the desciption of the firewall controversy of John Preskill here...
  4. T

    A Pair production without nucleus

    As far as I'm aware, pair production always involves the initial energetic photon interacting with another body (e.g. nucleus) to conserve momentum when creating the matter/antimatter products (e.g. electron and positron). Although "secondary" high-energy photons (e.g. ## e^+ + e^- \rightarrow...
  5. mark!

    I Requirements for pair production

    Pair production only occurs with high energetic photons (gamma rays rather than infrared rays, because a photon needs to have a higher energy than the sum of the rest mass energies of the electron and the positron). Where (on Earth and/or in space) does this occur? And why don't ALL gamma rays...
  6. V

    Constrained Motion of a Pair of Rods

    Homework Statement Homework Equations ## v = r \omega## The Attempt at a Solution Velocity of point B= ##v_B = 4 \times \omega = 4 ## m/s Since the separation between B and C is constrained to be a constant, Velocity of B along rod = Velocity of C along the rod ## \Rightarrow v_B \cos \theta...
  7. S

    Co-located pair of Phased Array Antennas

    I have been debating with a friend about a thought experiment that evolved out of an entirely unrelated discussion, but which has now become a subject of argument. Consider a "dual" phased array antenna that has every odd-numbered radiating element driven from input port 1 and every...
  8. M

    A Proton anti-proton pair and CP eigenstate

    p\bar{p} pair is a CP eigenstate? As p and \bar{p} are fermions (the pair is assumed to be at S-state), the pair seems to be C's eigenstate with eigenvalue of -1. As they have opposite intrinsic parity, the pair state seems to be P's eigenstate with eigenvalue -1. Then isn't it CP eigenstate...
  9. C

    B Particle pair creation probability

    I know that a high frequency light beam is more likely to generate a virtual electron-positron pair than a low frequency one. Can this probability depend on the reference frame? It seems there is a paradox. How do we explain it?
  10. L

    Simple gear pair: efficiency and output torque

    Hi. I have a question about output torque and efficiency of a simple gear pair as shown on the picture. So, I have a pinion and a gear. I give an input torque Tp in the clockwise direction. Therefore, the pinion will rotate with ωp angular velocity in clockwise and the gear ωg in...
  11. W

    Photon-photon collision - pair creation

    Homework Statement Two photon (wavelengths 1pm, 2pm) collide, decaying into a pair positron-electron find the velocities of these particles Everything happens in the x axisHomework Equations The system hc(1*1012+0.5*1012)=E++E- h(1*1012-0.5*1012)=P+-P- E=sqrt(c2P2+m2c4)The Attempt at a Solution...
  12. ikihi

    Pair Production Velocity Calculation

    Homework Statement [/B] A proton and anti-proton are created by a photon with wavelength λ= 6.607×10−7 nm. What is the magnitude of the velocity of the newly created proton and anti-proton pair? Note, the mass of a proton/anti-proton is mp= 1.673×10-27 kg = 938.3M MeV/c2. Homework Equations...
  13. Eclair_de_XII

    Bijective function between an ordered pair and a scalar?

    Homework Statement "Prove that ##S = \{(a, b) : a, b ∈ ℕ## and ##b ≥ 2a\}## is denumerable." Homework Equations Basically, my aim is to find a bijection ##f: ℕ→S##. The Attempt at a Solution Define ##f: ℕ→S## by ##f(x)≥2x##. Then suppose that there exist ##x_1∈ℕ## and ##x_2∈ℕ## such that...
  14. W

    Photon-electron collision with pair production

    Homework Statement photon collides with an electron producing a electron-positron pair, the three particles ( two electrons and one positron) move together in the same direction of the original photon. calculate the energy of each particle. Homework Equations photon: Ep=hf...
  15. Albert1

    MHB How Many Pairs of (x,y) Satisfy the Given Equation?

    $x,y\in N$ $\dfrac {1}{x}+\dfrac {1}{y}=\dfrac {1}{2010}---(1)$ How many pairs of $(x,y)$ we may get to satisfy (1)
  16. G

    Proving Mobius Behaving Pair with Möbius Function μ(n)

    Hello friends from afar. Given the Möbius function μ(n), prove that if , then . (The upper bound for both sums is the integer floor of x.) I've done the proof and it seems sound, but it also seems that the converse statement is true, implying that f and g should behave similar to a Mobius...
  17. Stoney Pete

    I Can an ordered pair have identical elements?

    Hi guys, Here is a wacky question for you: Suppose you have a simple recursive function f(x)=x. Given the fact that a function f(x)=y can be rewritten as a set of ordered pairs (x, y) with x from the domain of f and y from the range of f, it would seem that the function f(x)=x can be written...
  18. N

    B Is the Heisenberg Uncertainty Principle Equivalent to One Bit of Information?

    In information theory, one bit is typically defined as the uncertainty of a binary random variable that is 0 or 1 with equal probability,[4] or the information that is gained when the value of such a variable becomes known.[5] https://en.wikipedia.org/wiki/Bit That sounds a lot like...
  19. C

    Electron Hole Pair Production (EHPs)

    Homework Statement I'm taking a module in Solid State Electronics and in the first chapter we went through energy band diagrams, conduction band, valence band, fermi energy level, forbidden gap, etc. Now in the notes it starts to derive some formulae for electron and hole current densities Jn...
  20. J

    A Vacuum pair creations on the light-cone

    When a field is quantized on the light front, there is no possible pair creation from the vacuum energy. This is because kinematic operator P^+ generates only a positive spectrum ( https://en.wikipedia.org/wiki/Light_front_quantization#Spectral_condition ). So there is no "particles popping out...
  21. S

    A Electron-positron pair annihilation

    Consider the following u-channel diagram (on the right) in the link below. https://www.physicsforums.com/attachments/diphoton-png.95147/ Let the polarization vectors of ##k_1## and ##k_2## be ##(\epsilon^{\mu}_{1})^{*}## and ##(\epsilon^{\mu}_{2})^{*}## respectively. Do you label the incoming...
  22. S

    B Where Does the Charge Come From in Electron-Positron Pair Production?

    Where do the charge comes in electron-positron pair production
  23. G

    I Splitting Angular Momentum into Spin and Orbital Parts

    Does anyone know how close a photon needs to be to a nucleus (an ion really, no shielding from electrons) for pp to occur? I assume it's a probability as a function of distance, any ideas/equations? Thanks
  24. H

    Probability of a single pair poker hand

    Homework Statement How many one-pair 5-card poker hands are there in a standard 52-card deck? Homework Equations {}^nC_k = \frac{n!}{(n-k)!} 3. The Attempt at a Solution I've seen the following solution in several different places: n = {}^{13}C_1 \cdot {}^{4}C_2 \cdot {}^{12}C_3 \cdot...
  25. M

    MHB Construct a pair of simultaneous equations

    The students in a hostel are to get new uniforms. Each girl is to receive a blouse and a skirt , each boy is to receive a shirt and a pair of trousers.1 meter of white material is required to sew a blouse and $1\frac{1}{2}$ meters of blue material is required to sew a shirt . Moreover...
  26. B

    MHB Finding the Measures of Angles in a Linear Pair

    <1 and <2 form a linear pair. If m<1 = 5x + 9 and m<2 = 3x + 11, find the measures of both angles.
  27. Dr. Manoj

    How does the inert pair effect affect atoms?

    What exactly is inert pair effect? Please explain how is character shown by atoms increase/decrease along group and periods. What has to be done to increase this effect on an atom?
  28. P

    A Metric for Circular Orbit of Two Bodies

    I finally found a result I believe for the the asymptotic metric (valid for large r) of a pair of bodies in a circular orbit emitting gravitational waves. I use spherical coordinates, ##[t, r, \theta, \phi]##. If we let the linearized metric ##g_{\mu\nu}## be equal to the sum of a flat metric...
  29. C

    A Are neutrinos created by pair production

    Assume just for this question that a neutrino has a mass of 1 ev. That is about the energy of an infrared photon with a wavelength of 1 micron. Is it possible for a visible light photon, or a more energetic photon, to create a neutrino-antineutrino pair?
  30. Davephaelon

    I Calculating Cooper Pair Density in Niobium/YBCO

    Is it possible to calculate the average number of Cooper-pairs, existing at any given moment, per cubic centimeter of niobium (or YBCO), at their critical temperatures? I realize that Cooper pairs form and dissolve continuously, and constantly change partners, so perhaps its not easy to...
  31. Alltimegreat1

    I Seeing the Martian moons with a pair of $60 binoculars

    Is it possible?
  32. S

    I If pair of polynomials have Greatest Common Factor as 1 ....

    NOTE: presume real coefficients If a pair of polynomials have the Greatest Common Factor (GCF) as 1, it would seem that any root of one of the pair cannot possibly be a root of the other, and vice-versa, since as per the Fundamental Theorem of Algebra, any polynomial can be decomposed into a...
  33. Davephaelon

    B Can Cooper Pairs Have Different Orientations in a Superconductor?

    Can Cooper pairs have any spatial orientation within a superconductor? In most graphical depictions of a Cooper pair they are both on the same axis (moving through the same channel within the lattice), and parallel with the current direction. Is there any reason the pair cannot be at a right...
  34. R

    I Hawking radiation and energy-negative energy pair production

    A black hole evaporates through hawking radiation, what I don't get is the requirement for an energy-negative energy pair production. Since it's the black hole's gravitational energy that's responsible for the pair production, even if one of them escapes, the black hole would lose energy anyway...
  35. Titania

    Why Do Centrioles Exist in Pairs?

    I notice that centrioles always exist in pair. May I know why?
  36. W

    Importance of Fermi Surface in Cooper Pair Formation

    Hello, This problem is about cooper pair formation and what happens with the calculations if there is an attractive potential between electrons but it is not in the presence of a filled fermi surface. 1. Homework Statement Two electrons just above the filled Fermi Surface of a material can...
  37. E

    Magnetic field and gradient along axis of antihelmholtz pair

    Homework Statement An anti-Helmholtz pair consists of two circular coaxial current loops each with radius R and spaced a distance R apart from each other. The loops carry current I in opposite directions. 1) Calculate the magnetic field and the magnetic field gradient along the axis at the...
  38. Korbid

    Normalization of a pair distribution function

    Hi, i'm performing a simulation about this potential http://motion.cs.umn.edu/PowerLaw/ I calculated the radial distribution function succesfully but i don't know how these guys are normalized the other pair distribution function, as a function of time to collision. Could anyone help me? Thanks!
  39. Korbid

    Parametrizing a Pair Distribution Function

    Hi!, If we have a bidimensional system of N particles. How can i parametrize a radial distribution function g(r) in another single variable ? This variable is the "time to collision", which we define as the duration of time for which two particles could continue at their current velocities...
  40. A

    Decay into electron-positron pair in Yukawa theory

    Homework Statement I have a question regarding exercise 48.4-b in Srednicki's QFT book (the chapter is related to Yukawa theories). I have the official solution + explanation to the problem but I still do not fully understand the reasoning used in it, so perhaps you can help me. In the...
  41. Ryan Reed

    Quark Overproduction in the Big Rip Theory

    In the big rip theory, the force of dark energy isn't constant and increases over time. This causes first galaxies to fly apart, then solar systems, then planets, then stars, then atoms, then the atom nuclei. If it keeps increasing, it would start pulling the quarks inside protons and neutrons...
  42. DiracPool

    Pair Production and gamma ray

    Pair Production questions: 1) When a gamma ray photon pair produces an electron and a positron, do the two particles always have the opposite spin? That is, one always has +1/2(h-bar) spin and the other has -1/2(h-bar) spin? 2) Other than charge and spin, what are some other notable...
  43. A

    Axiom of Pair and Axiom of Union?

    So I've been learning Set Theory by myself through Jech and Hrabeck textbook, and I'm having trouble understanding some axioms. 1. Homework Statement What exactly is the difference between the axiom of pair and axiom of union? From what I understood, the axiom of pair tells us that there is a...
  44. M

    Photoelectron to electron hole pair doubts

    Hi, I have a couple of questions on photoelectrons. When a photoelectron of about 3-eV (varies) interacts within 0.2-um depletion region of silicon, what happens? I know, it will generate an electron-hole pair with an efficiency of 1 for 3.6-eV photoelectron. But what happens if the...
  45. J

    Proton-Antiproton colliding to produce top-antitop pair

    Homework Statement Suppose a proton and an antiproton collide producing a pair of top-antitop quarks. What would be the minimum required momenta of both proton and antiproton in order for this pair creation to occur? p + \bar{p} \rightarrow t + \bar{t} (Answer: 173 \frac{GeV}{c^2}, 59.9...
  46. ghaleb hamdan

    Does Pair Production proving quantum nature?

    Hi I have started studying Quantum Mechanics on my own and I had a question that I am stuck on. I apologize if it's too basic or if someone else asked it I understand what Pair Production is, but the source I am learning it from is saying that Pair production, is another way to prove the Quantum...
  47. grandpa2390

    Fourier Transform deduce the following transform pair

    Homework Statement I'm supposed to be using the similarity theorem and the shift theorem to solve: cos(πx) / π(x-.5) has transform e^(-iπs)*Π(s) Homework Equations similarity theorem f(ax) has transform (1/a)F(s/a) shift theorem f(x-a) has transform e^(-i2πas)F(s) The Attempt at a Solution...
  48. H

    Pair instability supernova pressure and temperature question

    I read a scientific journal article that discusses pair instability supernova - I am puzzled about something discussed in the article. If the collision of atomic nuclei and energetic gamma rays produces electron and positron pairs which reduces the pressure inside a supermassive star's core -...
  49. Ryan Reed

    How do quarks determine which quarks to pair with?

    Quarks join up with other quarks to form composite particles like protons and neutrons, but in the center of something like a nucleus, how do they know which quarks are in THEIR proton or neutron? When all the quarks are together and it becomes a "soup" of quarks, why doesn't it form things like...
  50. N

    Base current and Darlington pair

    Hi guys and gals, Here's a simple circuit mostly just an LED circuit with a Darlington pair. My question relates to the base current to the probe. If the probe is connected to an unearthed metal toaster (not plugged in), the LED glows briefly then goes out. If the probe is connected to the...
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