# What is Bec: Definition and 51 Discussions

The Bachelor of Economics (BEc or BEcon) is a four-year undergraduate degree in economic theory, econometrics and applied economics;
other titles are Bachelor in Economic Sciences (B.Econ.Sc.) and Bachelor of Applied Economics.
Specialized economics degrees are also offered as a
BA (Econ),
BSc (Econ),
BCom (Econ), BSocSc (Econ);
these degrees may span three years.
The curriculum is (substantially) more theoretical and mathematical than the major in economics available generally (BBA, general BCom or BA).

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1. ### B Are BEC vortex lattices individual atoms?

Can anyone tell me what are those vortex lattices in Bose-Einstein condensates (BEC)? Images of these vortex lattices in BEC can be seen here http://www.iap.tu-darmstadt.de/fileadmin/apq/apq_teaching/apq_teaching_ws1213/GESPERRT_moderne_optik/Ketterle_Vortex_Lattices_Science.pdf. Are those...
2. ### A Quantum vacuum fluctuation in BEC

Hi, I have some problems with visualization (I'm trying to understand Jeff Steinhauer's experiment, but my questions are general). Why the quantum vacuum fluctuations are guaranteed by the underlying pointlike atoms composing a BEC? And if vacuum fluctuations generate excitations (i.e...
3. ### I Why in BEC we must separate number of particles of ground state?

In BEC, why do we separate the number of particles of ground state(E=0) from the integral(total number of particles) when temperature below critical temperature. Why is the overall integral wrong while the index of sum of number of particle can be considered as continuous? Is it correct that...
4. ### Energy of a single vortex in BEC

I am trying to solve for the density variation due to a single vortex. The order parameter looks like. \Psi_0(\vec{r},t)=\sqrt{n}f(\eta)e^{i(s\phi-\mu t)} where f satisfy the ODE \frac{1}{\eta}\frac{d}{d\eta}\left(\eta\frac{df}{d\eta}\right)+\left(1-\frac{s^2}{\eta^2}\right)-f^3=0 I realized...
5. ### I Why does a BEC manifest no atom bunching?

Hello. I have asked Andrew Truscott of the Australian National University on why do lasers not manifest photon bunching like incoherent light does and BEC not manifest any atom bunching. His e-mail reply contains an answer that is a it confusing to me. Can you explain it to me please...
6. ### A Incorrect Hybrid Polariton Dispersion Results

I am trying to verify the results of the hybrid polariton case with the following hamiltonian, but cannot seem to verify the results in various published papers. Can someone please explain what is wrong and how to get the a similar dispersion graph? I'm solving for the eigenenergies for the...
7. ### I Photon BEC: Hypothetical Universe End-State

If we pose a hypothetical universe end-state very cold, where only very low energy photons are left. Could these photons undergo a phase transition into something like a BEC? Would they gain invariant mass if they did (become a condensate) Could someone show why this would/would not happen...
8. ### I Does slowing light with a BEC change any of its properties?

So I understand that scientists have been able to slow light to extremely low speeds using Bose-Einstein Condensates and even without them (https://physics.aps.org/story/v3/st37) and if I understand this correctly they slow light the same way water or air does; atoms absorb the photons and...
9. ### A Decoherence-free phononic BEC quantum devices?

Howl et al. 2016, Quantum Decoherence of Phonons in Bose-Einstein Condensates Anyone in the field of quantum information/quantum computation wish to comment on such an approach for building a quantum computer?
10. ### B Can Phonon Excitations in BECs Revolutionize Gravitational Wave Detection?

Ivette Fuentes and her group are attempting to use phonon excitations in BECs to detect gravitational waves. Their GW-detector is called MAGA, which stands for Micrometre Antenna for Gravitational-wave Astronomy. Here's a video of her explaining it: More from their blog:
11. ### I Maximum practical size of a BEC

It's technically very difficult to create BEC's of atoms, using lasers to cool the atoms to near absolute zero, in a vacuum chamber, and it was only first accomplished in 1995, despite being predicted many decades before that. The atom, or molecule, BEC's so far created are, from what I've...
12. ### A Can BEC Occur in a 2D Harmonic Trap but Not in Free 2D Bosons?

hi is there any physical reason why BEC can happen in 2d harmonic trap while not for free bosons in 2d? thanks
13. ### Refractive Index of BEC: Exploring Its Potential for X Rays and Gamma Rays

Does a BEC still have a very large refractive index for X Ray's and gamma rays?
14. ### Any difference between BEC correlations and entangled states

On Wikipedia, an article appear from which I quoted below. Here is something called Bose-Einstein correlation due to interference of wave character that I confuse with quantum entanglement. I want to know if these BEC correlations are entangled or separable states...
15. ### Can Water Exist in Bose-Einstein Condensate Form?

Is it possible for a molecule like water to exist in BEC form?
16. ### BEC Paper Q: Eigenvectors & Eigenvalues of Operator

http://bec.science.unitn.it/infm-bec/papers/preprints/becenc.pdf It's in regards to expression (4) I don't understand why the eigenvectors and eigenvalues of this operator happen to be the single particle eigenstates and the occupation numbers as they mention just below this expression. I do...
17. ### BEC question about number of excited particles

Assuming no interactions, and the energy levels ##\epsilon_j## for a single particle state, the occupation number for this state for a system of particles is given by: à ##n_j=\frac{1}{exp(\frac{\epsilon_j-µ}{kT}) - 1}## (1) (Here comes argument 1) We conclude that the maximal value that µ...
18. ### How BEC being described by the single-particle density matrix?

Hello everybody, this is my first time being here. I am a beginner learning some introductions on Bose-Einstein Condensation (BEC) on my own. Often times in the literature (say, [1], [2] (p.409) ) it comes the one-body(single-particle) density matrix, as...
19. ### Intro to BEC: An Accessible Guide for Undergrads

I'm a Junior-year physics major and I've just gotten an invitation to do some theoretical research with a couple of the professors at my school, which I'm really excited about. They're looking at Bose-Einstein condensation of molecules with electric dipole interactions, so although I get the...
20. ### BEC condenstate thermal statistics vs. coherence

Hi. I'm reading an introductory section on the Bose-Einstein condensation of a non-interacting, spinless boson gas. I'm confused by the claim that the ground state is in a coherent state with eigenvalue sqrt(N0) exp(i theta), where N0 is the expected number of particles in the ground state. The...
21. ### Regarding BEC: Bose distribution and probabilities

Hello PF. I won't just lurk around today, I will pose a question. I was looking at a dilute ultracold bosonic gas and was trying to see how one can predict the existence of a BEC and got stuck on this: I was comparing probabilities between finding the system in the lowest state...
22. ### BEC Help: Annihilation & Creation Operators, S Wave Scattering

Hey guys, im currently doing some stuff on bec's and was wondering if there were any good textbooks out there in general to help be understand annihilation and creation operators, s wave scattering, Hamiltonians of dilute BEC's, Gross-Pitaevskii equation and so forth.
23. ### Why is Rb one of the only things that a BEC can be made from?

I was wondering I have heard scientists recently made bose-einstein condensates from mostly alkali metals. My question is why? Why can't copper, gold or something else work?
24. ### Is BEC still considered a viable dark matter candidate.

There were proposals that dark matter might be ultra-light scalar particles in Bose-Einstein condensation phase, but the idea doesn't seem to have caught on. What are the advantages / disadvantages of this model?

What would happen if we send Free electrons in A BEC cloud? will it get destroyed because of the positrons? or will it just get compressed. please explain because i have a project that has something to do with it. i want an explanation that it is possible to send electrons in a BEC to get them...
26. ### What Temperature Initiates Bose-Einstein Condensation in a Gravitational Field?

Homework Statement For an ideal Bose gas in a uniform gravitational field, at what temperature does Bose-Einstein condensation set in. Gas is in a container of height L.Homework Equations Normal BEC temperature of an ideal Bose gas not under the influence of gravity is T = \frac{h^2}{2 \pi m...
27. ### Does superfluidity imply BEC? (+ other BEC questions)

Hello, I have to do a basic presentation about BEC (for a course on "Scientific Communication") and I had a question or two: How come there are many youtube clips of superfluidity and none of BECs? Is it wrong to consider superfluid 4He as a weakly-interacting BEC? (as I understand, a BEC is...
28. ### Creating Photonic BEC: What Possibilities & Applications Arise?

Researchers have for the first time managed to create a Bose-Einstein Condensate from photons: http://www.nature.com/news/2010/101124/full/news.2010.630.html What possibilities then arise from such a creation? What practical applications can be made from this work? I'd really like to know...
29. ### Can BEC experiments shed light on the mysteries of quantum gravity?

Might BEC give insight into how quantum gravity works? comment? Laura
30. ### Silly idea of BEC in any temperature

Hi, all, as the title mentioned, its a really silly idea: A box of fermions,at any give temperature, theoretically, and occasionally, number of particles might have zero velocities due to collisions in a very short time period. Then in this time period, (although its short, let's put it...
31. ### Difference between 1D lattice and 2D lattice on BEC

I studied in AMO physics. nowaday, I study about BEC. I'm wonder, Difference between 1D lattice and 2D lattice on BEC. In the web, they just explain what they do using that. Maybe just short word, or sentence, give me a huge knowledge. Thanks you, and Have a nice day!
32. ### How does they check the number of atoms in BEC?

In wikipedia, I read about BEC. so I just wonder in that articles, so I write in this page. Adopt that article, " They did this by cooling a dilute vapor consisting of approximately two thousand rubidium-87 atoms to below 170nK using a combination of laser cooling and magnetic evaporative...
33. ### Can Bose-Einstein condensates be created with decaying isotopes?

So this is a very novice but sincere question. I've just done a bit of reading about Bose-Einstein condensates, and the question that I immediately had was, What happens if one creates a BEC out of an isotope which is subject to radioactive decay? Would the atoms all necessarily remain in the...
34. ### Superfluidity & BEC: Connected Phenomena

Hi... reading Landau (statystical physics part2, second chapter) I see that in a first moment he explains superfluidity simply observing the spectrum of quasi-particles... no word about BEC... then all of a sudden in a paragraph ("wave function of the condensate")... he talks aboout...
35. ### Optical dipole trap for bec

optical diple trap is used to trap spinor bec i have a question why are the three different atomic internal levels feel the same shift? To calculate the energy shift of a specific internal level, we need to find out the coupling between this level to higher levels. For different levels...
36. ### Reaching absolute zero and BEC

Why are we finding it so difficult to reach absolute zero and if at all we are able to achieve it then what are the implications of such a feat? What relation does a bose einstein condensate have with absolute zero? (i know that we have achieved it but how does it happen as we lower temperatures)
37. ### What Does a Bose-Einstein Condensate Look Like to the Naked Eye?

What exactly does a Bose-Einstein Condensate look like with the naked eye? Is there any special about what it looks like through the optical part of the spectrum? What are the electromagnetic properties of a BEC as a whole?
38. ### Is the density of a bec larger or smaller than the air?

is there any anyone doing experiments?
39. ### Exact definitions of BEC for real gases-liquids?

While reading papers on various topics in physics i have become very embarrassed with the meaning of such a word as BEC. Even in peer-reviewed papers i can't find any attempt to give exact definition of BEC for real gases. For such topics as: Electron (pair-ed, superfluid) gas, 2D (! do you...
40. ### Why spinor bec is called ''spinor bec''?

what does spinor means? why do not just call it a multicomponent bec? Ho's paper does not explain why.
41. ### Cooper Pairs: Non-Ideal Gas Behavior & BEC Comparisons

Repulsive interactions are an attribute of Cooper Pairs, which mean that Cooper Pairs don't behave like an ideal gas . Are these the only attributes that prevent Cooper pairs to behave like an "ideal" boson? How could we show that the two superconductors of a JJ behave just like two BEC's?
42. ### I need some detailed information about Polaritons, and their 32K BEC.

I need some detailed information about Polaritons, and their 32K BEC.
43. ### Using BEC to Propel a Solar Sail - What Do You Think?

This is kind of a weird question, so I'll just throw it out there. So I was talking to my mate about BEC a couple of weeks ago and he proposed an interesting idea. I was telling him how BEC was used to slow down light to 38mph, what he suggested was using this concept to move a solar sail. So...
44. ### Polariton BEC, Polariton Laser - Applications?

Hi, This latest announcement on the development of something resembling a BEC using polaritons seems interesting: http://physorg.com/news98645866.html http://physicsweb.org/articles/news/11/5/17/1 So I'd like to know what the implications of this development are. Could this...
45. ### Can Mean Particle Numbers Be Negative in BEC Transition?

Homework Statement So the transition temperture is defined when at a given temperture the mean number of particles in the lowest state is 0. So does that imply there are tempertures where the mean value is a negative number? The Attempt at a Solution If not than surely at 1000k, the...
46. ### What is a Bragg Point: Exploring BEC of Triplet States

Can someone please explain to me what a Bragg point is? I can't find any information anywhere as to what this is. I'm going through an article about BEC of triplet states and it mentions Bragg point. For some reason, I have not encountered this before and would appreciate any help. Thanks.
47. ### Can One Star Alone Prevent BEC on a Planet? Explained

If there was a planet and there was no real energy source near it (say like our sun) would a few stars around 100million light years away on all sides of the planet(like our stars) be enought to keep atoms on the planet moving enough to stop BEC, or would BEC occur. Also if there was only one...
48. ### Bose-Einstein Condensate & Relativity: Experiments & Results

From a few days I was thinking that the fifth state of matter Bose-Einstein Condensate will obey the rules of Relativity! ...if practicals have been done on that please, tell me the results that were found.:confused:
49. ### Why do all experimental realizations of BEC use alkali metal gases?

I just read a review paper on Boson-Einstein condensation for the first time. I have 2 questions. 1.Can anyone tell me why all experimental realization of BEC are done in alkali metal gas, like Na, Cs? Can the interaction between atoms be totally neglected? 2.A facinating property of BEC gas...
50. ### Anyone knows maybe what are the BEC used for?

Anyone knows maybe what are the BEC used for? Thanks.