Talk:Bose–Einstein condensate

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"Original Einstein Manuscript Discovered". The Associated Press. August 20, 2005.

Pro Big Bang causal condensate theory

Describe it analytically. It concerns a very old and cold universe. It is a condensate of Planck noise which becomes important when temperature is almost none (zero). — Preceding unsigned comment added by 2A02:587:4109:BF00:C4A2:387E:F301:C52F (talk) 19:16, 3 August 2016 (UTC)[reply]

Read 37.157.173.110 (talk) 16:35, 23 September 2024 (UTC)[reply]

Discussion

In Einstein's non-interacting gas, what is μ? μ is a variable that has different meanings in different contexts and I'm not familiar enough with this one to know what it is and these are the only sentences that reference mu... In Bose–Einstein statistics distribution, μ is actually still nonzero for BECs; however, μ is less than the ground state energy. Except when specifically talking about the ground state, μ can be approximated for most energy or momentum states as μ ≈ 0.

— Preceding unsigned comment added by Drd0013 (talk • contribs) 23:46, 22 October 2015 (UTC)[reply]

To anyone that cares. The first sentence of the article is incorrect. BEC is not made up of bosons. Bosons are the particles that mediate forces, like photons. Should be fermions instead.

— Preceding unsigned comment added by 70.89.162.2 (talk) 22:50, 25 October 2012 (UTC)[reply]

I took the liberty of removing "LOLOL" from the second paragraph, it seems as though someone wanted to deface the website. The person's IP is logged in the history. Asrrin29 (talk) 01:09, 17 October 2009 (UTC)[reply]

I'm not a physicist, but the first two sentences give me a headache:

hey 131.111.243.37, please make sure to sign you posts. In answer to you issue though, I looked at the first two sentences, and they are basically the text book answer to what Bose-Einstein condensate (BEC) is, without invoking a complex mathematical understanding of the Stat. Mech. of Fermons and Bosons. Now, there is minor issue that the phrase "of dilute gas" right now suggests that BEC is a new gaseous phase of matter, when in reality BEC is not a gas but a different phase of matter and it just happens right now that technology used to make BEC starts with the element being in a sometime dilute gaseous form--- a literally in a tank of Rb Gas that hocked up or sprayed into a MOT. However, I am not sure how to properly generalize that concept that they go from a gas and then go down in temperature skipping liquid and solid, and all the other phases till they reach BEC phase, which is what I feel the edit was probably trying to get across when they mentioned "of dilute gas".Physics16 (talk) 17:26, 10 May 2010 (UTC)[reply]

Dimension error

I'm no quantum physicist but surely exp(energy/temperature) doesn't make sense? If your measuring temperature in eV or something similar then it should be stated (because your not actually measuring temperature really). I dare not edit to E/kT or E/RT but i'm very dubious. 131.111.243.37 (talk) 15:06, 10 May 2010 (UTC)[reply]

Hmm, well basically this (E/kBT) seems to be taking about the Boltzmann_factor term in the Bose–Einstein statistics that the Einstein derivation is using. Looking at it though, I do see why its confusing since the k is missing a "B" so that its e^(E/kBT) I am not sure how to at a subscript B though >>; . Physics16 (talk) 15:34, 16 June 2010 (UTC)[reply]

I have corrected find an minor error the same section that talks about the part about chemical potential exactly = 0, which I mentioned on Talk:Bose–Einstein statistics Physics16 (talk) 15:34, 16 June 2010 (UTC)[reply]

"A Bose–Einstein condensate (BEC) is a state of matter of bosons... Under such conditions, a large fraction of the atoms collapse..." Um... bosons are atoms?

Bosonic statistics allows for many particles to have the same quantum numbers. However, at normal temperatures, the distribution of particles is shared over many energy levels. Bose condensation occurs when a macroscopic (from a thermodynamic point of view) number of particles are in the ground state. A superconductor can loosely be thought of as a bose condensed state of electrion pairs, but this is heuristic only. Superfluidity does not necessarily occur with bose condensation. The easiest way to see this is that in bose condensation the ground state is at zero momentum. Superfluidity is the absence of viscosity, where, if given an initial velocity, there is no mechanism for the degredation of this velocity. Landau realized that the extra ingredient needed was a minimum in the energy dispersion relation, where the particles could then exists at finite velocity in a macroscopically coherent state.

In the first paragraph, in the parenthetical statement about Fermi-Dirac Statistics, the word "pearl" is used. Is this a typo? Should it be "particles?"

yes i think so, i just made this change

"A Bose-Einstein condensate was not actually created in a lab until June 5, 1995,"

Isn't Helium II a Bose-Einstein condensate? This has been created much earlier. If anyone knows in what way a superfuid is not considered a BEC it would be a good idea to clarify this statement.

AFAIK the major difference is that BEC occurs without any interactions between the particles, and is due to a rather simple balance between entropy and single particle energies. In He II the interactions are crucial to the phase transition. It would be nice to have an explanation of the opiginal Bose-Einstein derivation of the transition temperature.

I might try to write one up later on.

Helium II is, by the sound of it, an element/compound, BEC is simply the state of the matter, therefore it may have been created in another state. Thanks, George D. Watson (Dendodge). (talk) 16:20, 14 February 2008 (UTC)[reply]

The theory of a BEC as described by the work of Bose and Einstein is for a gas of non-interacting bosons. The superfluid Helium of P.Kapitsa can only be seen as an (strongly) interacting analogon for BEC. In Helium there is something like a 10% of the particles that can become superfluid, while non-interacting Bose-gas BEC's have no depletion whatsoever and interacting Bose-gas BEC's have only a very small depletion. To make life complicated bare in mind is that an interacting bose-gas condensate has superfluid(N.N. Bogoliubov proved this in 1947 IIRC) properties, but this doesn't mean a superfluid is a BEC. A BEC is caused by the statistics and only influenced by the interactions.

The derivation of the transition temperature isn't that hard(in a uniform potential). In D-dimensions one finds for the amount of particles (N) allowed to live in excited states:

$N=({\frac {L^{2}2\pi mk_{B}T_{c}}{h^{2}}})^{D/2}\sum _{k=1}^{\infty }{\frac {1}{k^{D/2}}}$

in 3D this gives a critical temperature

$T_{c}=({\frac {n}{\zeta ({\frac {3}{2}})}})^{2/3}{\frac {h^{2}}{2\pi mk_{B}}}$

with n=particle density

h=planck's constant

$k_{B}$ =Boltzman constant

$\zeta$ = the Rieman zeta-function

Usually BEC is observed in modern experiments using dilute atomic gasses, where the atoms are confined to a harmonic potential. For the case of non-interacting atoms confined by a harmonic potential the critical temperature is

$k_{B}T_{c}=\hbar {\bar {\omega }}\left({\frac {N}{\zeta (3)}}\right)^{1/3}\approx 0.94\hbar {\bar {\omega }}N^{1/3}$

where ${\bar {\omega }}=(\omega _{x}\omega _{y}\omega _{z})^{1/3}$ is the geometric average of the oscillator frequencies, and $N$ is the average number of atoms in the trap. I believe that this article should use this, more usefull, criticle temperature.

The moment I start the Dutch article about BEC, I'll add some things here.

Disagree. The BEC is a name for phenomenum when bose-particles get accumulated in the base state in macroscopic quantities (as written in Landau-Lifshitz, vol. V, paragraph 62). The wave function of the condensate is supefluid and parameter of order. I don't undestand why you think that BEC is something can happen only with noninteracting gas. OK, suppose BEC is for gases only - then how do you call accumulation of particles in the base state? --GS 02:57, 7 May 2005 (UTC)[reply]

(only second arrow is my opinion) Yes you are right when you say BEC is a phenomenon where a macroscopic amount of particles reside in the groundstate. And you are also right when you say that a BEC has the superfluid property...but I believe it is wrong to conclude the other way around: namely that a system that is superfluid is a BEC, this is not necessarily true.(something like saying: birds can fly => everything that can fly is a bird).

I also didn't say a BEC is only something that can happen in a noninteracting gas. What I wrote was that the work of Bose and Einstein predicted BEC for a non-interacting gas. It is quite simple to show that this specific quantum phasetransition is caused purely by the used statistics, not the interactions. The interactions influence the transition by causing a depletion of the groundstate, but this depletion is very small(only a few % at most).

I only said that superfluid HeII isn't a BEC, this is because the transition happens at temperatures wich are much to high (eg order 1000x higher then expected), with hugh depletions(>90%) and in a strongly interacting system. The cause of the "condensation to the groundstate" is different that is why it shouldn't be called BEC.(Dutch article)--Shade² 12:23, 12 May 2005 (UTC)[reply]

There is no 'cause', there is only possibility to condensate. Temperature (in other words - energy per molecule) works against the tendency. Interaction... could work both directions depending on. The attraction between He atoms, most likely, is responsible for the critical temperature 'too high'. The depletion of 90% - I don't know what you mean, AFAIK density of superfluid in He goes to 0 as T goes to 0 (see google://"He superfluid normal component density").

You do agree with you that there is a "condensation to the groundstate" of the Bose-particles of He-4. --GS 18:14, 12 May 2005 (UTC)[reply]

Depletion of 90% means that at most 30% of the particles in He can become superfluid, while there are no restrictions(ie all particles condense) in the classical non-interacting theory and with interactions only a few percents remain in the excited states.

Is not in agreement with experiments. See, f.e. http://mxp.physics.umn.edu/s03/Projects/S03He/theory.htm --GS 17:36, 13 May 2005 (UTC)[reply]

Superfluid HeII isn't only in He-4(bosons) but also in He-3(fermions)...I do agree that there is a condensation to the groundstate but the underlying mechanism is different as far as I know. BEC=statistics, superfluid HeII=interactions. So, though the endresults look the same they might be considered different things.--Shade² 11:34, 13 May 2005 (UTC)[reply]

'If one substitutes data pertaining to liquid He-4 in the formula for the critical temperature of an ideal Bose gas, one obtains a value of about 3.13 K which is not too far from the observed transition temperature of the liquid'. Contradicts 'transition happens at temperatures wich are much to high (eg order 1000x higher then expected)' above. Quote is from Jagdish Mehra's biography of Feynman, section 17.3. 82.16.105.62 (talk) 21:24, 1 November 2008 (UTC)[reply]

The second paragraph contains this statement: "the many overlapping atoms can be considered to be a single super-atom". I don't think this is a very precise way of describing it. The atoms are all in a single state, but they have not formed one particle ("super" or otherwise) in any way. Could someone come up with a better way of putting this?

Though there does not seem to be an entry in this encyclopedia for it, "Superatom" is used interchangably with "Bose-Einstein condensate" to mean the same thing, so i think "superatom" is a very appropriate term.

Temperature error

Why does the 50 pK temperature given in the second sentence in this article, and repeated later on, conflict with the 450 pK "lowest temperature ever" given in the 1 E-12 K article?

Especially when the value here is for the first activity in this field, back in 1995.

Is it just that somebody didn't know the difference between "one twenty-billionth of a Kelvin" (in that improperly capitalized name originally in this article) and "twenty billionths of a kelvin"? The former is 0.05 nK; the latter is 20 nK. I suspect that those two appearances in this article should read 20 nanokelvins. Gene Nygaard 03:20, 17 Dec 2004 (UTC)

Could the problem have been the ambiguous meaning of "billion"? (Different meanings in American and International English). We should use metric prefixes for everything....

Something is Missing!?

can anybody add what is meant by Tc and m, just to be precise. look at the formula. you will know what i mean. --212.202.37.226 23:49, 5 Jun 2005 (UTC)jan girke

ok, its fixed. PAR 01:27, 6 Jun 2005 (UTC)

Slowing light?

I think this section of the wiki should be removed, as it reflects the naivete of the author, and not modern physics. Claiming it's new science is not a great excuse for propagating wrong science. Photons never slow down. Ever. At the very least, clarification is necessary in this topic on the difference between an electromagnetic waveform and "light itself", or perhaps the distinction between phase velocity and group velocity. This is the same fallacy that leads people to believe that light can move faster than c (which is a universal constant, and the largest velocity it is physically possible to record). No respectable physicist would endorse the wording of this section as it stands.

The comments above show a clear mis-understanding of the effects of the Bose Einstein Condensate. It has been empirically demonstrated that bursts of light 'fired' through a BEC slow. A photon beam measuring 1km will shorten to approximately 5mm as it passes through the Condensate and as it emerges from the other side it lengthens to its original dimension. The wrighter should consider that whilst the speed of light cannot be exceeded - it does not follow that it always travels at maximum velocity. —Preceding unsigned comment added by 86.165.106.152 (talk) 23:49, 9 June 2008 (UTC)[reply]

In general, I find wikipedia's science pages to be inaccurate, mutually contradictory, and (like everything else on this God damned website) constantly in a battle of revision between two equally wrong versions of different slants. This website proves once again that the collective intelligence of humanity -- even internet-going humanity -- is significantly lower than "average". Which is exactly why important projects that need to be accurate to be useful (like, oh, a fucking encyclopedia) cannot be community-edited. All Of Us is far dumber than Some Of Us.

And where in the article, pray, does it state that photons are slowing down? -- CYD

Understandible statement but years and years ago we also used to teach that light couldent bend, and that pluto was a planet. Many new sciences are not believeable but that dosen't mean that they are impossible. We as humans are not even near the peak of understanding the universe and that why people gather together to discover new things. If you dislike this website, and how the pages contradict themselves you do not need to include yourself in the processing of the information given.

I see a person above (in the primary comment), regardless of perceived "intelligence" that doesn't have enough integrity to respect people. Your comments offend while using vulgarity to try and emphasize your point. It shows that, though you may have knowledge, you lack wisdom!

Many different ideas are the reality of condensed thought. Where else do you think the ideas of today came/come from? The ideas of many distill to actuality through trial and error. Even Thomas Edison needed 1000 tries before he finally tagged the real process to make an incandescent light bulb.

You can ridicule all you want, and even threaten an individual, yet you must understand that many ideas come from very radical and often hotly disputed topics! We must question and explore every possible answer to all ideas unless we want to lend deference to complacent thought. I expect a professional physicist would lend respect to others and still allow them to work out their own ideas while learning in the process.

Many of us “little minds” don't have the ability to incorporate all knowledge in a singular moment, and it takes walking through our own challenging mental hurdles. Please allow us to make mistakes, learn and grow, and please continue to coach us, but do not insult the “little minds”. You express impuned personal arrogance that undermines your personal integrity and credibility. We don’t care how much you know, if you treat people like they are less than you, your comments hold no weight.

Next time maybe your comments could be less pointed and focused on your displeasure of the Wiki system and more focused in helping us discover the truth. We feel it is arrogance and selfish pride to hold knowledge from all who are intently seeking the truth. That is what the middle ages were about, and I think we are past that. --DARRING_STUDENT 07:03, 26 February 2008 (UTC)

The person insulting all of humanity above may have knowledge, like someone else said, but surely not enough to realize he is not an elite member of humanity. Besides, why do many people commenting on his pathetic ranting consider him intelligent or having knowledge? He did not make not one scientific statement, he was just aggressive. Just because he redicules ignorance does not mean he's not ignorant himself, which I am sure he is or else he would provide us with the science that we are missing. Stop bashing wikipedia, it's a great way to introduce beginners to a subject, but a responsible researcher who wants to dig deep in a certain topic must use refereed journal publications on the topic and/or established books in the field. On a different note, someone above said photons never slow down. That's plain wrong. If you want to define photons classically, then they are the flow of energy of the electromagnetic wave, and they are defined as the Poynting vector. These photons do slow down and light does not always travel at c. c is only the speed of light in vacuum. These photons will travel at c/Re(n) in a material of refractive index n and they will decrease in number (i.e. the beam intensity decreases) by e^(-l*Im(n)), where l is the distance they propagate in the medium of refractive index n. —Preceding unsigned comment added by 138.246.7.156 (talk) 12:19, 2 February 2010 (UTC)[reply]

I suspect this is wrong many places in WP, and outside. Yes, photons always travel at c. But the interaction of large numbers of photons, with electrons (usually) can result in something that seems to move slower. When light goes through a dielectric, it isn't that photons slow down, but new photons are created as electrons move in response. The result, then, is a wave packet with a slower group velocity. Gah4 (talk) 08:30, 5 January 2024 (UTC)[reply]

5th State of Matter

The caption says "...new phase of matter..." so wouldn't the BEC be the 5th, after Solid, Liquid, Gas, and Plasma?

More like the 50th... (see phase) -- CYD

Restored some text from vandalism

Some text was removed during the vandalism that happened on 24/10/05, so I put it back. Tcb Beany 21:54, 20 November 2005 (UTC)[reply]

As far as I know, BEC is the 5th state of matter. —Preceding unsigned comment added by 75.47.111.227 (talk) 22:23, 27 October 2009 (UTC)[reply]

Removed "slowing light" section

I've made some changes to the article, the main one being that I removed the "slowing light" section. This was for a number of reasons:

1) It took up a disportionate amount of space, which made it seem that this was a big part of the research into Bose-Einstein condensation. While the experiments are very nice and have received a lot of media attention, this isn't really true. IMHO other topics have been more important.

2) The phenomenon isn't confined to Bose condensates- it has been observed in non-Bose condensed gases too.

3) I thought it was a bit confusing as it was written. This can be a confusing topic for many people (not least because it relies on knowing the distinction between phase velocity and group velocity) so I felt that this needed to be explained more carefully and in more detail in order to be useful and not to propagate this confusion.

I have mentioned it briefly in a new section titled "Current research" which discusses a few other things. If it's kept, I will add some external links and references a little later when I have more time.Brian Jackson 14:17, 15 December 2005 (UTC)[reply]

Note added: I've just noticed that there is an article on EIT, so I have linked to that instead.Brian Jackson 14:33, 15 December 2005 (UTC)[reply]

rewrite is erroneous

Bosenovas are not current research but the property of BECs, are an unexplained characteristic of BECs. Rewrite is erroneous and sounds uneducated. My link to Gravastars was also taken out even though Los Alamos National Laboratories is searching for them: [Government lab website]--Voyajer 04:46, 2 January 2006 (UTC)[reply]

Bose condensation of magnons

I have added a brief mention of the Bose condensation of magnons in antiferromagnets. From the viewpoint of statistical mechanics this is the same phenomenon as condensation of atomic bosons. Historically, the first successful observation of magnon condensation predates the experiment of Cornell and Wieman. Oleg Tchernyshyov 03:46, 26 January 2006 (UTC)[reply]

The introduction...

- "with properties that are currently not completely understood"

Is this true? Especially since it goes on to give an explanation... Simply put that viscosity drops to zero. Does it have other, magical properties? Apocryphite 01:34, 28 April 2006 (UTC)[reply]

Apparently not. Superfluidity in an interacting Bose gas has been understood for half a century. Oleg Tchernyshyov 10:54, 28 April 2006 (UTC)[reply]

Boulder Group is not the only one!

Although among the first 2 or 3, Boulder Group is not absolutely the first to obtain BEC. More than one research teams obtained it in 1995. Enough credit should be given to others too. (Check Science 269, 198 (1995); Phys. Rev. Lett. 75, 1687 (1995) and Phys. Rev. Lett. 75 3969(1995).)

Dash in title?

Why is there an en-dash in the title? Wouldn't a hyphen be fine (and more grammatically correct) here? — 75.35.38.237 04:11, 30 September 2006 (UTC)[reply]

I agree with you, but I don't particularly feel like potentially getting involved in a revert war right now. Someone else want to make the change? Anonymous 57 05:25, 30 September 2006 (UTC)[reply]

En dashes are properly used to separate names in lists of collaborators because sufficiently many academics have hyphenated names. For instance, Nash-Williams would refer to work by Crispin Nash-Williams, but Nash–Williams could indicate a collaboration between John Forbes Nash and somebody named Williams. Michael Slone (talk) 19:41, 1 October 2006 (UTC)[reply]

This is currently being discussed at Wikipedia talk:Manual of Style (dashes)#Clarification re dashes separating surnames in page names. Note that this article has already come up in the discussion there. Gene Nygaard 02:54, 9 October 2006 (UTC)[reply]

Bose-Einstein Condensation: A Network Theory Approach

Assuming it's legitimate, shouldn't this other article be merged into this one? Clarityfiend 03:17, 7 March 2007 (UTC) Honestly I too am semi-skeptical that the second argument really is legitimate considering its an on going research problem and topic to moving BECs effectively from one magento optical trap to another across. However, my experience of network theory and its relation to quantum computing is not 100% accurate. My personal opinion is that you could e-mail someone like Dr. Michael Chapman of Georgia Institute of Techonology or even those in physics forums to get there weight on your particular issue. Physics16 (talk) 01:04, 27 October 2011 (UTC)[reply]

BEC vs superfluidity (SF)

Unfortunately, the article almost equates Bose-condensation and super-fluidity. These are in fact very different and unrelated fenomena. BEC is about a state of weakly interacting particles in an external field. SF is about excitation spectrum of a strongly interacting self-bound system. Most BECs are dilute gases and most SFs are dense fluids. Most BEC are not FS and most FS are not BECs. For example, He3 becomes superfluid, but it is not even a bosonic system.

BEC is a simple and well understood phenomenon. SF is complicated and not understood.

with respect, BEC and superfluidity are related. BECs have clearly shown superfluid behaviour. For example PRL 99, 260401 (2007) (preprint available here. Also, He3 becomes a superfluid through forming bosonic pairs. BEC can be strongly interacting - see the Bosenova; BEC in chromium, a dipolar gas; and molecular BECs. For this reason a BEC doesn't need an external field - it's own self-interaction is sufficient. BEC is about off-diagonal correlation functions ... superfluidity, the same. griff (talk) 17:22, 21 February 2008 (UTC)[reply]

Supercooled

The introductory paragraph uses "supercooled" as a synonym for a temperature near absolute zero. However, that article says "Supercooling is the process of chilling a liquid below its freezing point, without it becoming solid", without mentioning any other meaning of "supercool" -ed or -ing. The coldest temperature named in that article is 150K, but the warmest temperature named in this Bose–Einstein condensate article is 14K. Several dictionaries agree with the supercooling article. So which is the correct definition, or does it mean both? In either case, the link to supercooling is unhelpful because it leads to an unrelated discussion. Art LaPella (talk) 06:25, 22 November 2007 (UTC)[reply]

The idea of supercooling is applicable here, as the atoms do not coalesce and form a solid or liquid; they are in their gaseous state until they collapse into a condensate. Torsionalmetric (talk) 02:19, 28 January 2008 (UTC)[reply]

The super in supercooling means that the temperature has been reduced below the phase transition temperature without the transition taking place. Therefore the conditions in the introductory paragraph are just cooled, not supercooled.82.16.105.62 (talk) 21:02, 1 November 2008 (UTC)[reply]

Bose-Einstein condensation: a network theory approach

Anyone know what the hell Bose-Einstein condensation: a network theory approach is? Does this belong on Wikipedia? --Xyzzyplugh (talk) 06:13, 18 January 2008 (UTC)[reply]

Velocity Distribution Graph

I find the explanation of the velocity distribution graph confusing. Would it help if each axis is explicitly described. I am also confused by the term "false colors". The explanation may be accurate but this layman cannot easily figure it out. 75.16.138.165 (talk) 16:44, 19 January 2008 (UTC)[reply]

False color means that if you looked at the actual experiment you would not see those colours. The cameras that take the images of atoms are greyscale and only return a single number for each pixel on the camera, corresponding to how much light hits the pixel. So in reality the experimenter sees a black-and-white image. For presentation and interpretation it is usually easier to recolour the image using a computer. Here the image uses red as no atoms and white as many atoms. It's purely an aid to the eye. Another point here is that the images taken are 2D, so the 'height' of each image again represents how many atoms there are at that point in the 2D image from the camera.

The velocity distribution is not at all intuitive. These are time of flight images. Each image shows a position distribution, but if we know how long the atoms have been in flight (and the experimenters do) then they can extract the velocity. So in the image on the far right the atoms have a very small range, or distribution, of velocities Frure (talk) 17:43, 21 February 2008 (UTC)[reply]

Error converting 170 nanokelvin to Celcius?

The article equates 170 nK with -273.150000017 °C, which is absolute zero minus 0.000000017 K. First, 0.000000017 is 17 nK, not 170 nK. Second, it should be -273.15 plus 170 nK. By my calculations, that comes to -273.14999983 °C. 72.145.240.148 (talk) 14:18, 21 January 2008 (UTC)[reply]

I concur with this; I opened to the discussion page to see if someone else noticed this error. I'll make the change now.Torsionalmetric (talk) 02:06, 28 January 2008 (UTC)[reply]

Exclusively bosons?

In the very first sentence it says that Bose-einstein condensate is a state of matter of bosons. I was wondering if it could be achieved in fermions such as deuterium and carbon-13 (at least my understanding is that they are fermions) or if it is exclusive to bosons? —Preceding unsigned comment added by 68.158.66.56 (talk) 22:59, 24 January 2008 (UTC)[reply]

Fermions need to pair into bosons order to Bose Einstein condense, otherwise the exclusion principle prevents them from stacking up in the same state. If the pairing is tight, meaning the typical distance between the partners in the pair is much smaller than the distance between pairs, the result is a Bose-Einstein condensate (BEC) of the pairs, which can be treated as a unit. If the pairing is loose, meaning that there are many fermions in the volume occupied by a "pair" (the word pair is in quotes, because in this limit the pairing is not a property of just two electrons, but a nonlocal phenomenon in the whole Fermi gas), the condensed state is called a BCS state. There is a lot of research now focusing on exactly how a BCS state turns into a BEC state when the interaction is increased.Likebox (talk) 00:43, 25 January 2008 (UTC)[reply]

Maybe this comes from the fact that Einstein did not speak English at all. So how in the world did he translate the paper from English to German "himself"? Celsius conversions appear to be lost in translation, so to speak... —Preceding unsigned comment added by 199.230.203.254 (talk) 13:04, 11 December 2009 (UTC)[reply]

Where are the missing atoms from a bosenova explosion?

Could it be that a micro black hole is created in the bosenova explosion? --LF1975 (talk) 13:01, 27 February 2008 (UTC) Could this possibility be added in the article?--LF1975 (talk) 09:46, 29 February 2008 (UTC)[reply]

Are there any sources that address the possibility that this was MBH (micro black hole) creation at lower than predicted energies and a failure of Hawking Radiation to evaporate it? See LF1975 above for Nobel Prize Laureate response "Probably not a black hole" [also implying probably not evidence of Hawking Radiation failure]. How probable against, this has implications for the safety expectations for the LHC (Large Hadron Collider) due to go on-line May 2008. --Jtankers (talk) 06:11, 4 March 2008 (UTC)--Jtankers (talk) 05:41, 4 March 2008 (UTC)[reply]

Dubious Claim?

I'm having trouble with this statement in the introduction.

"If a system is at such a low temperature that it is in the lowest energy state, it is no longer possible for it to reduce its energy, not even by friction. Without friction, the fluid will easily overcome gravity because of adhesion between the fluid and the container wall, and it will take up the most favorable position, all around the container"

How could a system lose energy by friction? Even worse, how can a particles "overcome gravity" and give themselves more potential energy by distributing themselves around a container?

This statement will be subject to my deletion, unless someone can convince me that it belongs in the article.--MaizeAndBlue86 (talk) 01:09, 28 February 2008 (UTC)[reply]

Since Bose-Einstein condensates exhibit quantum characteristics on a larger scale, it's not very surprising that it will spontaneously gain potential energy, seemingly violating our current understanding of the laws of physics (It even says in the article that they are not well understood). Also, friction always causes an energy loss. Think about it in terms of kinetic energy, if you push a wooden block, it has kinetic energy, after a couple seconds it will stop due to friction, and thus will have no kinetic energy due to friction. While I have never seen this property of the Bose-Einstein condensate demonstrated, I have read about it in several places before, and I am almost certain that it is not a dubious claim.76.233.4.209 (talk) 01:51, 17 April 2008 (UTC)[reply]

2 questions

I wondered

If the universe expands and, 'cools down for ever', will it then in then end be a large einstein-bose condensate ?

It is said that atomes act like waves, in einstein-bose condensates; is that similair to strings, as in string theory ? —Preceding unsigned comment added by 82.217.115.116 (talk) 21:39, 9 April 2008 (UTC)[reply]

Depends on if the universe condenses to a boson —Preceding unsigned comment added by 204.60.106.206 (talk) 17:48, 25 June 2008 (UTC)[reply]

Apparent Vandalism

Someone had recently altered the Introduction to state that the fluids "cannot" easily overcome gravity, which I believe to be erroneous, and a different IP changed the caption of a simple illustration to claim that the illustration was, in fact, a photograph -- another "dubious" claim (cough, cough). I restored the original text in both cases. 168.9.120.8 (talk) 12:43, 23 April 2008 (UTC)[reply]

If the universe does not have enough mass, then it will continue to expand, however being a BEC is not even logical since the universe is not even mater in itself. Instead most of the matter will cease to exist (do to antimater-matter collision and other matter destroying events like black holes). Also the matter in BEC behaves in WAVELIKE patterns and not actually waves. I quote from someone but i forgot who it was "The matter in BEC looses its identity and is uncertain who it is". also a super atom would have more mass than BEC since in BEC the matter itself all exists in the same place itself and you cannot identify one from the other.

Sign Error?

There is something bothering me about the section titled Einstein's Argument. Surely, if K is the number of particles in the |0> state then P(K) should be an increasing function of K, since larger K means less particles in the higher energy |1> state. I suspect there may be a sign error somewhere. Watgaanhieraan (talk) 21:14, 10 May 2008 (UTC)[reply]

"Diagram"

There seems to be a really terrible diagram on the page claiming to show the difference in atoms between the condensate and normal matter. It looks like someone did it in MS Paint. Delete? —Preceding unsigned comment added by 209.112.170.134 (talk) 23:11, 3 June 2008 (UTC)[reply]

We need some sort of diagram or photo. Liquid, gas, and plasma do. 75.118.170.35 (talk) 21:18, 10 January 2009 (UTC)[reply]

Yes, but we do have a very good figure now which shows the velocity distribution before and after B-E condensation. The comment about the "terrible diagram" was made last June, and seems to refer to another figure in the section "Unusual characteristics" which was removed 12 June 2008 by Drake Unlimited as "misrepresenting the process". I agree with that description. Dirac66 (talk) 22:24, 10 January 2009 (UTC)[reply]

Fahrenheit

I recently added the Fahrenheit measure to the top. Think anyone cares enough about Rankein for it to be added?

No. In fact, Fahrenheit is probably already distracting enough. No scientific papers will specify the temperature in Fahrenheit, and I don't think that it will help laymen to understand how cold that is by providing as many temperature units as possible. If one cares, one can find the conversion elsewhere. Zoltán (talk) 20:08, 29 November 2008 (UTC)[reply]

Misleading introduction and other remarks

I just would like to mention that, if the dimension of the system is larger than 2, the external potential is not a prerequisite for the occurrence of BEC. In this regard, the first sentence of the introduction is quite misleading. (And it is refuted by the discussion on theory: why would anyone bother to write down the transition temperature for a uniform, i.e., not trapped, gas, if BEC can only occur in a trap?) It just so happens that it is much easier to conduct a BEC experiment in a confining potential, but it is not required. I think, that sentence should be yanked. Also, since the transition temperature depends on the mass of the particles (amongst other things), it is not true that the temperature must be close to absolute zero. In fact, recent experiments on polaritons proved that BEC is possible at temperatures in the vicinity of 100 K, and there is evidence that this can be improved that brought to the room-temperature range. See also the discussion on "Some subtleties". Moreover, in a laser, at arbitrary temperature, quantum effects are apparent. I think, the overture to this article is rather poor.

The section titled "Introduction" doesn't really say anything about BEC, but gives a somewhat loose discussion of superfluidity, perhaps. It's not clear what purpose it serves.

The section titled "Theory" kicks out with the sentence "The slowing of atoms etc.". However, no one says that BEC can occur only for atoms. There are many other bosons, photons, phonons, excitons, polaritons etc.

By reading the article, I can't but observe that it's is rather unstructured. It's obvious that many people wrote it, and it's diverted from the main subject on a number of occasions. What is also a problem is the fact that the article is not self-consistent: it contains contradictory statements, without specifying the conditions.

These were my general remarks, and I would like to hear the opinion of others. Zoltán (talk) 20:08, 29 November 2008 (UTC)[reply]

I think the introduction is trying to explain to those unfamiliar with the terminology the difference between condensation, condensed matter physics and exotic condensates of which the Bose-Einstein condensate is an example. But it doesn't do it very well. I think you should rewrite it as you seem to knwo what you are talking about. SpinningSpark 20:14, 29 November 2008 (UTC)[reply]

Why is there a section on the GP equation?

I am just wondering what the purpose of the section on the Gross-Pitaevskii equation might be: there is a full-fledged article with that title, and the author of this section stops immediately after writing down the equation. It doesn't really help understanding, I believe. This should be yanked altogether, and only a link to the relevant article should be kept. Zoltán (talk) 20:18, 29 November 2008 (UTC)[reply]

BECologist

What do you call an expert in the feild of BEC? (cf. plasmologist) 75.118.170.35 (talk) 17:55, 30 December 2008 (UTC)[reply]

Since BEC is usually at low temperature, it seems low-temperature physicist would be likely. Otherwise, I might go for quantum physicist. Gah4 (talk) 05:50, 7 January 2024 (UTC)[reply]

Some Subtleties

It could merely be my own skewed reading of this section, but it seems to be more akin to a personal tirade than a paragraph in an encyclopedia entry. Anyone care to rewrite this? —Preceding unsigned comment added by 97.113.111.198 (talk) 23:50, 31 December 2008 (UTC)[reply]

I think part of the problem is that this section reads like a commentary on a missing history section. For example, this section explains why He-4 is not the best example of a BEC, but nowhere in the article at present is it mentioned that He-4 was the only known example, even though imperfect, for almost 60 years.

This made me wonder if there had ever been a history section in this article, so I used the Revision History Search tool to search for "Kapitsa" (who discovered the superfluid properties of He-4 in 1937), and found that there was a well-written (I think) section called Discovery which was removed without explanation by a numbered editor on 11 January 2008. I will restore the Discovery section today to its former place in the article. This may provide background for revision of the Some Subtleties section. Dirac66 (talk) 01:47, 1 January 2009 (UTC)[reply]

Transfered from article superatom, merged into here

Merge this. 205.170.14.251 (talk) 18:52, 5 April 2008 (UTC)[reply]

Hold On

Rather than merge, I strongly suggest keeping the article, but editing it to reference non BEC's. These are vaporized metal atom clusters. See [1]. Tmangray (talk) 17:09, 1 July 2008 (UTC)[reply]

I agree, do not merge it. It will become a bigger topic once science finds out more about those neat atoms. --Svenstaro (talk) 22:59, 7 July 2008 (UTC)[reply]

Don't merge. Expand the article. Rreagan007 (talk) 20:17, 23 July 2008 (UTC)[reply]

Please remove the Merge proposal. The referenced article has nothing to do with BEC's. If anything, this should be merged with Superatom —Preceding unsigned comment added by 137.138.93.189 (talk) 13:16, 29 August 2008 (UTC)[reply]

The nature of the containers

When the word 'container' is use doesn't that somewhat imply a container made out of materials, instead of entrapment with lasers.(And maybe other methods) 82.169.255.79 (talk) 14:41, 23 June 2009 (UTC)[reply]

about this article

A four dimension "ideal gas" does go BEC when t < T_c, why did this article not write ? —Preceding unsigned comment added by 218.164.99.31 (talk) 11:15, 7 July 2009 (UTC)[reply]

Solid state BEC

A lot of this article mentions only atomic BEC should it not also deal with BEC in solid state. Room temeperature condensates have been achived in exicton-polariton system - should this not be mentioned? —Preceding unsigned comment added by 131.111.184.70 (talk) 11:43, 20 January 2010 (UTC)[reply]

"Blowing off"??

What does this term mean as used in this article? There is a general chatiness of tone in the article besides this.--Jrm2007 (talk) 22:20, 17 March 2010 (UTC)[reply]

Well I think they literally means that the 10,000 atoms where expelled forcibly and violently from the trap. However, after thinking about the phrase "blowing off" outside in the modern context, I realize how this might be considered offensive. Therefor I change the word to expelling. If you can find any other comments that you feel are offensive or catty in this article, please feel free to post them. Physics16 (talk) 15:17, 16 June 2010 (UTC)[reply]

There is either a wrong word here or a missing comma

"Lithium has attractive interactions which causes the condensate to be unstable to collapse for all but a few atoms." Comma after unstable? Stringing infinitives is always confusing. —Preceding unsigned comment added by 4.230.117.176 (talk) 11:10, 15 October 2010 (UTC)[reply]

"Very close to absolute 0"

You must be approximately 1/1 000 000 of a degree above absolute 0 to attain Bose-Einstein condensation, perhaps this should be added instead of saying very close? —Preceding unsigned comment added by 206.45.178.143 (talk) 02:57, 8 December 2010 (UTC)[reply]

The first BCE was created at a temperature of 170-billionth of a degree above absolute zero. Do you have a citation for the warmer figure of 1/millionth of a degree, and is this a good figure for all elements? J JMesserly (talk) 03:38, 16 December 2010 (UTC)[reply]

Layperson's overview needed- any volunteers?

Wolfgang Ketterle gave a talk at MIT in 2001 that had sections which were directed at a lay audience. A recent Nova episode also made the subject much more accessible to a laypeople than the treatment given in the current version of this Wikipedia article. I certainly do not advocate "dumbing down" or subtracting any of the precise and technical content whatever. What I am advocating is that there be a section of the article devoted to the lay audience. Examples of the material included might include ways of visualizing a BEC such as those given in the recent Nova program "Absolute Zero". For example:

DANIEL KLEPPNER (Massachusetts Institute of Technology, Department of Physics): Matter can exist in various states: atoms at high temperature always form gases; if you cool the gas, it becomes a liquid; if you cool the liquid, it becomes a solid. But, under certain circumstances, if you cool atoms far enough, to extremely low temperatures, they undergo a very strange transformation; they undergo an identity crisis.
So let me show you what I mean by an identity crisis. When you go to low temperatures, the quantum mechanical properties of the atoms become important. These are very strange, very unfamiliar to us, but, in fact, each one of these atoms starts to display wave-like properties. So instead of points, like that [draws dots on whiteboard], you have little wave packets, like that [draws s shaped waves], moving around. It's really difficult for me to explain just why that is, but that's the way it is.
Now, as you go to very low temperatures, the size of these packets gets longer and longer and longer. And then suddenly, if you get them cold enough, they start overlapping [draws s shaped waves with multiple overlaps]. And when they overlap, the system behaves, not like individual particles, but particles which have lost their identity. They all think they're everywhere. This little wave packet, over here, can't tell whether it's this one, or that one, or that one, or that one, or that one, or that one. It's there and it's there and it's there. They're all in one great big quantum state. They're all overlapping, overlapping.
They're all doing the same thing. And what they're doing, to a good approximation, is they're simply sitting at rest. This Bose-Einstein condensate is very difficult to imagine or to visualize. I could imagine what it's like to be an atom, running around gaily, freely, bouncing into things, sometimes going fast, sometimes going slow. But in the Bose condensate, I'm everywhere at once. I've lost my identity. I don't know who I am anymore. I'm at rest, and all the other atoms around are at rest. But they're not other atoms around; we're all just one great big quantum system. (source

Now, there may be better visualizations or analogies than Dr. Kleppner's, but the point is that there is a place for this sort of lay person's description in the current article. This is certainly not my field, so it would be best if the section is crafted by someone with a firm grasp of this field of physics. If no such improvement is attempted in the next few months, I shall take a stab at it by cribbing together illustrations such as the one quoted above. J JMesserly (talk) 03:30, 16 December 2010 (UTC)[reply]

Proposed merge of Bose–Einstein condensation: a network theory approach

Absolutely not - The network theory analog of Bose-Einstein condensation is mathematically identical, and therefore can give insight into certain aspects of the physics of Bosons, but it is a completely different discipline and should in no way be confused with the physics of Bosons. PAR (talk) 16:08, 12 April 2011 (UTC)[reply]

pronunciation

As bose is pronounced Boshū, I was wondering if the pronunciation should be included in the article too. But I assume most people pronounce it as Bose–Einstein and not as Boshu–Einstein. --helohe (talk) 01:41, 12 December 2011 (UTC)[reply]

And how are we supposed to pronounce boson? Gah4 (talk) 05:56, 7 January 2024 (UTC)[reply]

Could we add a banner about the article being too technical?

...for non-physicists? I've the feeling that quite a few people's eyeballs are spinning in multiple directions (at the same time) at reading this. And then they go elsewhere.

Nevertheless, this is an important concept that needs to be understood. It would help if the article were less technical.

Thank you, and Happy Trails! Dr. Entropy (talk) 23:42, 29 March 2012 (UTC)[reply]

Spinor BEC

I have noted that there is no mention of spinor BEC in this article, only scalar BEC topics. This is a large and active area of research in BEC, maybe large enough to have its own article, but should at least be linked from from this article. 130.207.141.143 (talk) 19:55, 4 July 2013 (UTC)[reply]

New Source

I dont know if this helps anything, but I'll leave this here: [2].-19:35, 3 December 2013 (UTC)

Recent unsourced edits

Arnaud Migres (talk), no matter how interesting or informative your recent good faith edits, it is important to provide reliable and verifiable WP:VERIFY sources WP:SOURCES or references for material added to Wikipedia articles. This will enable users to verify that the information given is supported by reliable sources, thus improving the credibility of Wikipedia while showing that the content is not original research. Please revise your recent edits by providing the source(s) of your information. Thanks in advance. Coldcreation (talk) 07:11, 12 February 2014 (UTC)[reply]

Assessment comment

The comment(s) below were originally left at Talk:Bose–Einstein condensate/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Could it be that a micro black hole is created in the bosenova explosion? Could this possibility be added in the article?

--LF1975 (talk) 09:48, 29 February 2008 (UTC)[reply]

Please guys remember to sign you post ^^, Physics16 (talk) 14:51, 16 June 2010 (UTC)[reply]

Last edited at 14:51, 16 June 2010 (UTC). Substituted at 10:06, 29 April 2016 (UTC)

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Requested move 12 May 2017

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: Not moved. See MOS:HYPHEN#Dashes. Materialscientist (talk) 05:12, 12 May 2017 (UTC)[reply]

Bose–Einstein condensate → Bose-Einstein condensate – A hyphen is to be used here [instead of a dash] according to the standards of correct typography. Liuthar (talk) 21:11, 11 May 2017 (UTC)[reply]

This is a contested technical request (permalink). Anthony Appleyard (talk) 05:07, 12 May 2017 (UTC)[reply]

Not uncontroversial. Besides, this proposed move would violate MOS:DASH. SkyWarrior 00:29, 12 May 2017 (UTC)[reply]
@Materialscientist, Liuthar, and SkyWarrior: Queried move request Anthony Appleyard (talk) 05:07, 12 May 2017 (UTC)[reply]

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

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convergence of g.

The section Ideal Bose gas says that $g_{3/2}$ is only convergent on [0,1]. It seems to me that it should also converge on [-1, 0]. Could someone confirm that, and update the text accordingly? LachlanA (talk) 04:48, 15 September 2021 (UTC)[reply]

Plasma

The state consists of super energetic and super excited particles . This particles are in the form of ionized gas. the fluorescent tube and neon sign verbs consists of Plasma inside a Neon size bulb there is neon gas and inside a fluorescent tube their is helium gas or some other gas the gas get ionized that is gets chat when electrical energy flows through it this charging up create a plasma glowing inside the tube or bulb the plasma close with the special colour depending on the nature of the gas the sun and the stars glow because of the presence of Plasma in them the plasma is created in stars because of very high temperature 2402:8100:259A:AC48:D1E1:71A1:F24A:4810 (talk) 03:49, 16 May 2022 (UTC)[reply]

Article issues and classification

Reassess article. The article fails the B-class criteria with section "needs additional citations" tag, and unsourced sentences, paragraphs, and subsections. -- Otr500 (talk) 00:23, 27 February 2023 (UTC)[reply]

External links

There are 15 entries in the "External links". Three seems to be an acceptable number and of course, everyone has their favorite to add for four. The problem is that none is needed for article promotion.

ELpoints #3) states: Links in the "External links" section should be kept to a minimum. A lack of external links or a small number of external links is not a reason to add external links.
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WP:ELMIN: Minimize the number of links. -- Otr500 (talk) 00:27, 27 February 2023 (UTC)[reply]

On the origin of the term 'condensation'

I did some research on the origin of the term Bose-Einstein condensation: The condensation part seems to have been introduced by Kahn and Uhlenbeck in 1938 (https://verga.cpt.univ-mrs.fr/pdfs/Kahn-1938uq.pdf). They compared recent results for the condensation of vapour to liquid by Mayer et al (https://doi.org/10.1063/1.1749933) and Einstein's study of the degenerate Bose gas and noted the similarities. The full term came together when London published an article entitled On Bose-Einstein condensation the same year. (https://journals.aps.org/pr/pdf/10.1103/PhysRev.54.947). This still needs secondary sources for verification before it is added to the article. Jähmefyysikko (talk) 14:24, 20 December 2023 (UTC)[reply]

Read the translation of the 1925 Einstein paper. Already features there. Jähmefyysikko (talk) 20:15, 20 December 2023 (UTC)[reply]

He-4 and He-II

The article seems to indicate that He-II is, and then isn't, a BEC. Statements like: The quest to produce a Bose–Einstein condensate in the laboratory was stimulated by a paper published in 1976 seem to suggest that superfluid helium from many years earlier isn't a BEC. Is it the difference between a liquid and gas that needs to be indicated? Gah4 (talk) 08:39, 5 January 2024 (UTC)[reply]

Yes, or perhaps more fundamentally, it is the interactions which make the phenomenology more complicated. If you have access, see Annett, Superconductivity, Superfluids, And Condensates, pp. 21,27. Jähmefyysikko (talk) 11:54, 5 January 2024 (UTC)[reply]

Need better intro for non-physicists

As an engineer who reads science widely, I understood nothing from the intro about what, exactly, a BEC is, what makes it different/distinct from other states of matter, and observable effects or characteristics. From most Wikipedia articles for terms which can appear in news articles, a smart layman can grasp at least the basics. 98.97.33.216 (talk) 15:40, 7 June 2024 (UTC)[reply]

minor dark mode visual problem.

the condensed matter physics photo in dark mode does not change the text color in that photo so you get slightly more black words on a dark blue background and hard to see. making the letter the same color as the rest on the page would fix it. but adding a white background to the photo would partially defeat the purpose of the dark mode.

also feels weird to click the report a problem button and have no pop up to explain what the problem is. at least until i found the help page and was told to use the talk panel instead. 67.63.77.40 (talk) 14:20, 5 August 2024 (UTC)[reply]

specifically the "Report an issue with dark mode" button. i like dark mode. i want to improve dark mode. 67.63.77.40 (talk) 14:25, 5 August 2024 (UTC)[reply]