Instigating a Bosenova

[Moontanman]

Originally Posted by KALSTER

Oh, that's ok then It is just that Buffy is an administrator. Thanks for your comments, I share your enthusiasm (obviously), it is a phenomena that defies explanation using current theory. How often does that happen? My take? Well my take would mostly consist of uneducated speculation, hence my misguided post here. Being uneducated I naturally do have my own little hypothesis that might (in my mind) explain a lot of things. I have an idea that forces might be distinct fractal disturbances of an Einsteinian aether, the magnetic field (consisting of its own brand of fractals) being tuned to destructively interfere with the intermolecular forces of the BEC, but as I said, it is not based on current theory or understanding, which I am after on this thread. You?

Well, I'm not exactly a PHD either but I am impressed by it's connection or similarity to larger more real world type systems. How close does it simulate a real Nova? Real world applications would be very interesting but I can't think of any right now. It is fascinating to be sure, I hope more information is forthcoming.

[KALSTER]

Unfortunately, while it does resemble a supernova, it does not yield much energy. Learning the details behind the curtain of uncertainty might yield some surprising discoveries about the nature of matter though

[Moontanman]

Originally Posted by KALSTER

Unfortunately, while it does resemble a supernova, it does not yield much energy. Learning the details behind the curtain of uncertainty might yield some surprising discoveries about the nature of matter though

I wonder what would have happened if the BEC had been made of helium3 or deuterium or a mixture of both(assuming it could have been made of them) What might have happened then?

[KALSTER]

I am not sure, but it can't be sustainable IMO. The BEC is cooled to 3 billionths of a degree Kelvin, so any heat gained would destroy the conditions necessary for the Bosenova to occur in the first place. Since I have received no answers to my questions in the OP, I am guessing that the induced switch to an exclusively attractive intermolecular force would not be possible in non-BEC conditions, as the exact required modulation for each molecule would have to be administered individually. This is not a problem for the BEC, as the whole condensate can be thought of as one giant molecule, having collapsed into the same wave function.

[Moontanman]

Originally Posted by KALSTER

I am not sure, but it can't be sustainable IMO. The BEC is cooled to 3 billionths of a degree Kelvin, so any heat gained would destroy the conditions necessary for the Bosenova to occur in the first place. Since I have received no answers to my questions in the OP, I am guessing that the induced switch to an exclusively attractive intermolecular force would not be possible in non-BEC conditions, as the exact required modulation for each molecule would have to be administered individually. This is not a problem for the BEC, as the whole condensate can be thought of as one giant molecule, having collapsed into the same wave function.

I know it takes special atoms to make a BEC I was just wondering if either helium3 or deuterium were one of them. If they were and you crowded them together close enough no matter what the temp you should get a reaction that releases large amounts of energy. They did say the core of the BEC was contracted to vanishing. I don't really know enough to really be making any assumptions about this, it was just a stray thought passing through what little gray matter I have floating around in my head

[modest]

Originally Posted by KALSTER

They change the properties of the magnetic field trapping the BEC, but how does that affect the forces present in between the constituent atoms? Do they simply tune the field so that it cancels out repulsive forces by destructively interfering with them? Can this only be done with BEC’s because of the uniformity of the wavefunction the atoms collapsed to? Does it mean that the virtual force-carrier particles of each field (van der Waal?) interfere with each other and cancels out? What happens to the energy then, or does it simply revert to the ground zero point energy?

It is called Feshbach resonance.

When comparing the magnetic field to the scattering length of two atoms (near the Feshbach resonance):



the scattering length (a) can be negative or positive. The original Bose-Einstein condensates were done with rubidium-87 which naturally has a positive atom-atom scattering length. This makes for a stable condensate as is described below. Newer experiments including the Bosenova is done with rubidium-85 which has a negative atom-atom scattering length. By controlling the magnetic field containing the BEC, the condensate can be tuned near the Feshbach resonance, and to either side. This is called BEC-BCS crossover and it is described some here:

Feshbach Resonances and the BEC-BCS crossover

From BEC to BCS
The interaction between two atoms can be described by the scattering length, shown on the right versus magnetic field close to a Feshbach resonance. On the side where the scattering length is positive, the molecular energy level is lower in energy than the energy of two unbound atoms. The molecular state is thus "real" and stable, and atoms tend to form molecules. If those atoms are fermions, the resulting molecule is a boson. A gas of these molecules can thus undergo Bose-Einstein condensation (BEC). This side of the resonance is therefore called "BEC-side". On the side of the resonance where the scattering length is negative, isolated molecules are unstable. Nevertheless, when surrounded by the medium of others, two fermions can still form a loosely bound pair, whose size can become comparable to or even larger than the average distance between particles. A Bose-Einstein condensate of these fragile pairs is called a "BCS-state", after Bardeen, Cooper and Schrieffer. This is what occurs in superconductors, in which current flows without resistance thanks to a condensate of electron pairs ("Cooper pairs").

Relevant to the Bosenova: If the scattering length is positive (see pic above) then it will make up diatomic molecules with a self-repulsive effect. Conversely, if the scattering length is negative there is an attractive interaction. The theory behind this is complicated. If you’re looking for particulars you can look here:

http://www.tcm.phy.cam.ac.uk/~fmm25/...i_LECTURE4.pdf

Originally Posted by KALSTER

What do they mean when they say that “this procedure caused the BEC to implode and shrink beyond detection”?

The method used to image a condensate has only a finite resolution. I assume it imploded to a size which was under the detectable resolution of the equipment. This does not mean it really 'disappeared', nor did the missing rubidium 'disappear' in the sense that it surely is still in the universe following the first law of thermodynamics. The missing condensate probably escaped the magnetic trap - which I gather is odd considering the energy needed to accomplish that.

I'd like to thank you Kalster for posting this topic which is very interesting. I am very uneducated when it comes to all things quantum and I enjoy topics such as these that peak my curiosity on that topic. From everything I just read, there is no satisfactory theory or explanation for why this 'explosion' happens. There are many proposals as one can see here, but nothing too solid. Hopefully solving this mystery will provide insights into other things quantum mechanical.

~modest

[Moontanman]

Originally Posted by modest

It is called Feshbach resonance.

When comparing the magnetic field to the scattering length of two atoms (near the Feshbach resonance):



the scattering length (a) can be negative or positive. The original Bose-Einstein condensates were done with rubidium-87 which naturally has a positive atom-atom scattering length. This makes for a stable condensate as is described below. Newer experiments including the Bosenova is done with rubidium-85 which has a negative atom-atom scattering length. By controlling the magnetic field containing the BEC, the condensate can be tuned near the Feshbach resonance, and to either side. This is called BEC-BCS crossover and it is described some here:

Feshbach Resonances and the BEC-BCS crossover



Relevant to the Bosenova: If the scattering length is positive (see pic above) then it will make up diatomic molecules with a self-repulsive effect. Conversely, if the scattering length is negative there is an attractive interaction. The theory behind this is complicated. If you’re looking for particulars you can look here:

http://www.tcm.phy.cam.ac.uk/~fmm25/...i_LECTURE4.pdf



The method used to image a condensate has only a finite resolution. I assume it imploded to a size which was under the detectable resolution of the equipment. This does not mean it really 'disappeared', nor did the missing rubidium 'disappear' in the sense that it surely is still in the universe following the first law of thermodynamics. The missing condensate probably escaped the magnetic trap - which I gather is odd considering the energy needed to accomplish that.

I'd like to thank you Kalster for posting this topic which is very interesting. I am very uneducated when it comes to all things quantum and I enjoy topics such as these that peak my curiosity on that topic. From everything I just read, there is no satisfactory theory or explanation for why this 'explosion' happens. There are many proposals as one can see here, but nothing too solid. Hopefully solving this mystery will provide insights into other things quantum mechanical.

~modest

I think it's agreat thread too, too bad Buffy thought it was about a dance

[KALSTER]

Yes, thanks modest for the info and interest. I'll have lots of interesting stuff to rumage through now!

[Buffy]

Originally Posted by Moontanman

I think it's agreat thread too, too bad Buffy thought it was about a dance

Well, it should have been!

But seriously, I reserve my impertinent hit and run posts *only* for those topics that are really interesting (the ones that are silly ravings of madmen do not deserve the attention )...

So anyway, back on topic, it would seem to me that BEC's actually have "normal" (i.e. easily obtainable) densities: in fact my understanding of the process of forming BEC's is to reduce the pressure on the system in order to obtain lower temperatures. What I'm confused about is that it would seem that attaining "nova-like" properties would require very high density, and the given ambient pressure along with the miniscule gravitational force provided by a handful of atoms could not possibly produce any outward rebounding force.

The near absolute-zero temperatures might allow some weakening of the electromagnetic repellent force allowing the nuclei to come into closer proximity than would be seen at normal temperatures as the system "collapsed" but in theory this should not be "over-balanced" by a stronger outward push once some minimum radius was attained.

Thus, my question really surrounds Modest's last post:

Originally Posted by Modest

The missing condensate probably escaped the magnetic trap - which I gather is odd considering the energy needed to accomplish that

Where indeed is this force coming from? Is it really a case of some minimum radius causing some geometrical increase in electromagnetic repulsion, or is there possibly some evidence of "string-like" behavior that is being exposed in this experiment?

Not as vacuous as she looks,
Buffy

[Moontanman]

Good save Buffy