What is Bell: Definition and 226 Discussions

A bell is a directly struck idiophone percussion instrument. Most bells have the shape of a hollow cup that when struck vibrates in a single strong strike tone, with its sides forming an efficient resonator. The strike may be made by an internal "clapper" or "uvula", an external hammer, or—in small bells—by a small loose sphere enclosed within the body of the bell (jingle bell).
Bells are usually cast from bell metal (a type of bronze) for its resonant properties, but can also be made from other hard materials. This depends on the function. Some small bells such as ornamental bells or cowbells can be made from cast or pressed metal, glass or ceramic, but large bells such as a church, clock and tower bells are normally cast from bell metal.
Bells intended to be heard over a wide area can range from a single bell hung in a turret or bell-gable, to a musical ensemble such as an English ring of bells, a carillon or a Russian zvon which are tuned to a common scale and installed in a bell tower. Many public or institutional buildings house bells, most commonly as clock bells to sound the hours and quarters.
Historically, bells have been associated with religious rites, and are still used to call communities together for religious services. Later, bells were made to commemorate important events or people and have been associated with the concepts of peace and freedom. The study of bells is called campanology.

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  1. M

    FInding distance from top of diving bell to lake surface

    Homework Statement A cylindrical diving bell with open bottom and closed top 12.0m high is lowered into a lake until water within the bell rises 8.0m from the bottom end. Determine the distance from the top of the bell to the surface of the lake. Homework Equations I actually solved this...
  2. jk22

    Bell theorem without hypotheses?

    i found the following proof of Bell's theorem : we measure spin in 3 different directions a b c we can note the counting of events N1=n(a+,b+,c+) N2. + + - N3. + - + N4. + - - N5. - + + N6. - + - N7. - - + We have N3+n4<=n7+n3+n4+n2 With n3+n4=p(+a,-b)...
  3. jk22

    Quantum Measurement Operator and Results: Exploring the Inverse Bell Theorem

    if we consider a separable measurement operator $$(A+A')\otimes (B-B')$$ then quantum mechanics predict the result is in [-2;2] Whereas going to classical results would give in [-4;4] This could indicate that going from measurement operator in the quantum realm to measurement results is maybe...
  4. A

    Why is the integrated information of a Bell state = 0?

    In section IIIA (p11) Max Tegmark tries to prove that the integrated information Φ of a bell state is zero. The definition of Φ that Tegmark uses is given by the mutual information I minimized over all possible factorizations. The bell state has I=2 when written in the usual basis. Tegmark...
  5. 1977ub

    Clocks Within Each Ship in Bell Spaceship Paradox

    I believe length contraction always makes more sense when integrated with reminders of relativity of Simultaneity. Let's say the engines are at the back end of each rocket. For the viewer "A" in the initial frame, they begin moving and continue accelerating simultaneously, and clocks next to...
  6. R

    Random switch setting in bell theorem

    I was trying to understand Bells theorem and I found this site http://www.upscale.utoronto.ca/PVB/Harrison/BellsTheorem/Analogy.html easy to understand. I found the "The Second Analogy: More Boxes" in it easy to grasp. But one thing I didn't understand in it, where it uses the word random...
  7. P

    Binney's interpretation of Violation of Bell Inequalities

    Although he is primarily an astrophysicist, Dirac medal-winning Oxford Professor James Binney has taught a Quantum Physics course to second-year students at the university for years. A series of 27 of his lectures for the course is featured on the university's official website. Binney's take on...
  8. Nick666

    Arxiv: No Bell, no collapse, no spooky, no nonlocality

    http://arxiv.org/pdf/1308.5290v2.pdf I'll just highlight some stuff " "We submit: Doesn’t quantum theory itself, which is a local theory, account for its own predictions? As the authors of this quote know very well, experi- mental data contradict Bell’s theorem [22,23], which im- plies that —...
  9. edpell

    Progress on Explaining Bell's Inequality

    Is here any progress on explaining Bell's Inequality? I do not mean explaining what it is, I mean how it works.
  10. Elroy

    Visually representing entangled qubits (i.e., Bell state)

    Hi All, I'm in the beginning stages of writing a quantum computer emulator, primarily to get all the concepts down. I've got an excellent Bloch sphere with a Bloch vector that I can duplicate as many times as I like. However, I'm now tackling entangled states. I'm struggling with identifying...
  11. jerromyjon

    Understanding the Bell Inequality and its Impact on Quantum Mechanics

    I went through a paper last week about the Bell inequality and how it is incompatible with QM. Something along the lines of probability in classical regards being 1/3 but in quantum mechanics it is 1/4. It went into some basic principles of how this is determined through quantum entanglement to...
  12. T

    MHB Stats question about a bell curve

    Hey I am new here and not exactly sure how it works. I am stuck on this problem from my professor and would love any help anyone has!When one thinks of the normal distribution the first thing that comes to mind is the bell curve and grades. While this is one example of a normal curve that is...
  13. J

    Unraveling the Mysteries of Bell Jar Experiment Equations

    Are there any equations you can use for the bell jar experiment? Any answer would be appreciated thanks
  14. D

    A variation of the Bell experiment

    If we start with a Bell state 1/Sqrt(2)(|00>+|11>) and (after moving the second qbit a significant distance away) apply the interferometer transformation |0> -> 0.5(|0>+|1>) |1> -> 0.5(|0>-|1>) to the first qbit, we get 0.5/Sqrt(2)((|0>+|1>)|0>+(|0>-|1>)|1>) =0.5/Sqrt(2)(|00>+|10>+|01>-|11>)...
  15. jk22

    Polarization, Bell, and spin of photons

    i have the following questions: Bell inequalities use spin 1/2 matrices and experiments use photons. Is then the electric field horizontal or vertical after the measurement with a polarizer in other words can we assimilate the orientation of the field with a vector in the hilbert space ? How...
  16. J

    Question from a 5 year old: Bell and Black Holes

    Seriously, a 5 year old asked me whether entanglement information survives/escapes a black hole. Specifically, he asked me (in only slight paraphrase) whether if one of the particles (headed in different directions) fall into black holes on either end, does the other one know it?
  17. d_morales97

    Solve Diving Bell Problem: Find Height of Water Rise in Bell

    A cylindrical diving bell 3.4 m in diameter and 4.5 m tall with an open bottom is sub- merged to a depth of 148 m in the ocean. The temperature of the air at the surface is 22C, and the air’s temperature 148 m down is 6.3C. How high does the sea water rise in the bell when the bell is...
  18. J

    Analyzing Innsbruck Bell experiment raw data sample

    Raw data sample source: http://people.isy.liu.se/jalar/belltiming/ 999 detections parsed in .txt format: http://www.mediafire.com/download/1pi64hrydzs7r7h/bell999.zip This below is the first 99 detections. It's unmatched raw data, so A-B pairs on the right are going to be different once the...
  19. B

    Polarization and Bell measurments

    There have been quite a few Bell threads lately, so I have been looking at them and various other sources. I'm missing something... any guidance appreciated. Per Dr. Chinese's, "Once any photon passes through a polarizer lens, its polarization will be aligned exactly with the lens thereafter...
  20. L

    Exploring the Bell Paradox: Observers, Acceleration, and Infinite Possibilities

    There are several threads on the Bell paradox, plus the article in the FAQ forum, but I must be missing something here. Forget for a moment about 2 ships. Let's take one ship, which an observer at the front and the other at the rear. The ship is undergoing a constant 1G acceleration. The...
  21. Entanglement

    Bell shape like of Planck's distribution

    As a high schooler, what I can deduce from Planck's distribution's bell shape is that the majority of the atoms of a body above 0k possesses a certain K.E which is the average K.E which leads to the presence of a peak point in the distribution. While the minority posses higher or lower K.E...
  22. C

    What is the Bipolar coordinate system used for in the DSM manual?

    I was searching the internet for information on Bell tests, when I found an article entitled "Taco Bell tests grilled stuffed nacho." Does anyone know how the stuffed nachos are used in Bell tests? http://www.huffingtonpost.com/2013/10/11/taco-bell-grilled-stuft-nacho_n_4086345.html...
  23. morrobay

    What Interpretation/Model of QM Predicts Bell Inequality Violations ?

    Are there any modern interpretations of QM that predict the correlations in a Bell Inequality violation ? Preferably a local non realistic model based on mechanisms.
  24. G

    Bell experiment: Rotate measurement device 180°

    Hi, I was just writing another thread when I stumbled upon something strange: What if I now make a slight change and replace ##\bf{b}\rightarrow-\bf{b}##? The expectation values containing ##\bf{b}## change signs and I get $$\left|\frac{1}{\sqrt{2}}-0\right|=\frac{1}{\sqrt{2}}\leq...
  25. morrobay

    Is Superposition the Explanation for Bell Inequality Violations ?

    This form of a Bell inequality: n[x-y+] + n[y-z-] ≥ n[x+z+] is derived from spin measurements at A and B when detector settings are aligned. If it is correct that when a particle is measured at detector A and is spin up in the y direction , then its entangled twin at B is in superposition...
  26. Zafa Pi

    Hidden variables - Bell - The Law of Malus?

    Invariably in the lay literature when it comes time to show that EPR hidden variables are incompatible with QM, Bell's Theorem is invoked (e.g. Greene's "Fabric of the Cosmos", Zeilinger's "Dance of the Photons", Rosenblum's "Quantum Enigma", ...). I don't see why a simple application of...
  27. bohm2

    Simultaneously testing the Kochen-Specker and Bell theorems

    Kochen-Specker rules out non-contextual hidden variable theories and Bell's theorem rules out local theories. I thought this was an interesting paper, particularly the authors' conclusions: Simultaneously testing the Kochen-Specker and Bell theorems http://arxiv.org/pdf/1308.6336.pdf
  28. naima

    Are There Only 4 Bell States According to Wikipedia's Definition?

    I look at wikipedia.org/wiki/Bell_state and use the same notations. The article says that there are just 4 Bell states. Is not |\xi^+\rangle = \frac{1}{\sqrt{2}} (|0\rangle_A \otimes |+\rangle_B + |1\rangle_A \otimes |-\rangle_B) another maximally entangled state? The Schmidt decomposition...
  29. N

    What can we say about Bell theorem?

    Bell theorem say that there is a contradiction between the locality principle in special relativity theory and quantum mechanics.So one theory must be incomplete describable theory.Then which theory(special relativity or quantum theory) is incomplete describable theory?
  30. Demystifier

    Do Bell and PBR together point toward nonlocal reality?

    The Bell theorem (and its variations) suggests that either locality or reality is wrong. The PBR (Pusey-Barrett-Rudolph) theorem (and its variations) suggests that quantum state is real (ontologic). So what do they tell us together? Do they suggest that eventually it is only locality which...
  31. X

    What's the difference between Bell curve and Gaussian distribution

    I was looking to the definition of the Bell curve, and the Gaussian distribution, but I don't see any difference when we represent them in a graph. Both have the same Bell curve. What is the difference between the Bell curve and the Gaussian distribution?
  32. V

    Spin singlets and the Bell states

    Given two spin-1/2 particles, the overall spin of the pair decomposes into a spin singlet and a spin triplet. Using the Clebsch-Gordon series and referring to the z-axis, we find the spin singlet is: ##|\Psi^- \rangle = \frac{1}{\sqrt{2}}(|\uparrow_z \downarrow_z \rangle - |\downarrow_z...
  33. M

    Bell Proof Against Hidden Variables in EPR

    I have a question regarding the paper by John Bell (www.drchinese.com/David/Bell_Compact.pdf‎ ) in which he shows that a certain hidden variable approach cannot reproduce the expectation values predicted by QM for a pair of particles in the singlet state. After eqn 15 on page 4, I don't...
  34. O

    Need help understanding question regarding Bell states

    Homework Statement Basically, in a homework question, I'm presented with the definition of bell states and asked to show some elementary properties. I've been able to show they form an orthonormal basis, and express them in terms of the usual basis, |00>, |01> |10> |11>. I am then asked...
  35. P

    Density matrix for bell states

    Hi I have three states (I believe bell states) and want to find the density matrix, am I right in thinking: 1) \frac{|00> + |11>}{\sqrt{2}} \rightarrow \rho = \left( \begin{array}{cc} \frac{1}{\sqrt{2}} & 0 \\ 0 & \frac{1}{\sqrt{2}} \\ \end{array} \right) (because it is pure) 2)...
  36. M

    Bell State of two non-orthogonal modes

    Is this possible? If I have, say a photon and two non-orthogonal polarizations \mid0\rangle and \mid1\rangle, can I create a Bell state \mid10\rangle+\mid 01\rangle If not, what is the reason? Thank you :)
  37. M

    Another question about bell inequality

    I imagine that some topics and questions keep reappearing since it is hard to track through all past posts even with the query tool. So apologies if this has been covered before (as it probably has). I just want to check my intuitive understanding of the Bell experiment, having heard an...
  38. DrChinese

    Realism in the vein of EPR and Bell

    Morrobay suggested we split off this discussion from another thread. I will post my summary of the EPR definition a bit later today.
  39. G

    Why do experiments violating Bell's inequality matter?

    I keep looking at these experiments that demonstrate violation of Bell's inequality and I really can't figure out why anyone cares. The scenario always seems wrong in some way. For example the EPR paradox. The argument goes like this, if you start out with a source of entangled "photons"...
  40. I

    Entangled photons in bell experiment: transfer phase or angular momentum?

    Regarding the polarization correlation studies generated using parametric down conversion. All the studies appear to be done correlating the polarization of linearly polarized photons. Has any experiment been done showing the same effect with circularly polarized light? 1) If this...
  41. J

    Bell Paradox Questions - Diagram help

    Consider the following thought experiment. Two spaceships are initially floating in a region of space far removed from other matter. They are at rest with respect to each other, and with respect to some inertial reference frame F. There is a distance L between them. At some time, t=0, as...
  42. L

    Equivalence Relations in A={a,b,c,d}: Proving the Bell Number Theorem

    Our math Teacher asked us to find how many equivalence relations are there in a set of 4 elements, the set given is A={a,b,c,d} I found the solution to this problem there are 15 different ways to find an equivalence relation, but solving the problem, i looked in Internet that the number of...
  43. I

    'Toy' universe complying with Bell experiments

    After reading a bit about Bell's theorem and various hidden variable theories, I thought a little about the detection loophole, and how it gets around Bell's theorem while still allowing a pretty much 'local' Universe. The main argument against this, as I understand it (correct me if I'm wrong)...
  44. Killtech

    Deriving Measurement Operators for Realistic Detectors

    Lately I was studying the Bell and CHSH inequalities on Wikipedia (it has proven to be a good source to get an quick idea about everything). The articles are detailed and even provide the core of the proof in a mathematical derivation that is easy to understand. But it leaves me still with a...
  45. A

    Electric bell description help

    describe how an electric bell operates (HINT: the make break contact dose not move; the hammer, however, moves bath and forth very quickly as it rings the bell) my solution An electric bell is a mechanical bell that functions by means of an electromagnet. When an electric current is...
  46. M

    What does a Bell measurement mean in quantum teleportation?

    Hi, I have a question regarding quantum teleportation. I understand that Alice starts of with a photon A whose state she wants to teleport. Alice and Bob share an entangled pair of photons, B and C. Then Alice does something called a Bell measurement which entangles A and B and the result...
  47. U

    Water bell; got answer but shape's weird?

    Homework Statement This question is about finding the smallest bowl to contain all the water being spurt out of a water spray head. They used the lagrange multipliers to solve it which I understand, but the the envelope doesn't look like a parabola to me?? Isn't the envelope...
  48. D

    Nonregular icosahedral die approximating a bell curve

    Can somebody provide a solution for creating a nonregular icosahedron whose facets are sized in such a way that, when used as a die, the probability distribution of the 20 sides would approximate a (stepped) bell-curve??
  49. A

    Minus sign in Bell derivation

    Hello, I am trying to reproduce Bell's calculation for the expectation value of paired spin measurements on particles in the singlet state. For unit vectors \hat{a} and \hat{b} we want to calculate P(a,b)=<\psi|(\hat{a}\cdot\vec{\sigma})(\hat{b} \cdot \vec{\sigma})|\psi> where...
  50. M

    Bell Spaceship Paradox: A and B's Viewpoint

    Hello, Suppose, A and B spaceships are moving with constant acceleration. There is a string tied to spaceships center to center. A is on left of B and B is on right of A. C is outside observer. As speed increase, A sees that B going further ahead, and B sees A going further behind. So, from...
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