Bose Einstein Condensate

[BenSon]

Ok I've been reading up on these things and I've got a few questions that I can't find the answer too. For example the atoms in these state are bosons right? And I was taught that Bosons are force carrying particles, so can atoms in BEC state act as force carrying particles such as photons? Also I read that no matter how many photons you put in a box (say its totaly reflective) you would always be able to add more could somone please explain to me how this is possible, Thanks

 

Scott

[timo]

The "bosons are force carriers"-statement is only true for elementary particles of the standard model. It does not apply to particle compounds such as atoms.

What exactly is your problem with the photons in the box?

[Severian]

All the force carriers are bosons, but bosons don't have to be force carriers. Even in the SM this is true because the Higgs boson isn't a force carrier. Of course, exchaning a boson (of any kind) between two particles will transmit momentum from one to another, so it really depends on your definition of 'force carrier'. Usually the expression is meant in technical terms:a "force carrier" is the gauge boson which makes the symmetry of the force local.

 

You can add as many photons into the box as you like, but the pressure on the sides of the box will get larger because you are reflecting more and more phtons off the sides.

[timo]

Even in the SM this is true because the Higgs boson isn't a force carrier.

Oops, I almost knew I overlooked something.

[swansont]

Also I read that no matter how many photons you put in a box (say its totaly reflective) you would always be able to add more could somone please explain to me how this is possible' date=' Thanks

[/quote']

 

 

Since they are Bosons, they aren't subject to the Pauli exclusion principle - you can put as many in a given state that you want. (practical limits aside)

[BenSon]

Since they are Bosons, they aren't subject to the Pauli exclusion principle - you can put as many in a given state that you want. (practical limits aside)

 

But don't they take up space? There must be a physical limit in how many there are in the box.

 

Scott

[5614]

Hence he said "practical limits aside".

[swansont]

But don't they take up space? There must be a physical limit in how many there are in the box.

 

Scott

 

Eventually you will destroy the mirrors doing the confining, but that's a limitation of not having 100% reflective mirrors. That's not a space issue.

[BenSon]

Ok, does a photon take up space? and if it does there must be a limit to how many you can put in a (100%) reflective box. So what im asking whether or not it is possible just considering the space issue.

 

Scott

[swansont]

Ok' date=' does a photon take up space? and if it does there must be a limit to how many you can put in a (100%) reflective box. So what im asking whether or not it is possible just considering the space issue.

 

Scott[/quote']

 

 

That's actually a separate issue. In a reflective box, the wavelength must be a multiple of L/2 (i.e. you need to fit a standing wave in it) so a wavelength longer than L/2 will not "fit." But as long as you fulfill the standing wave condition, you can keep adding photons. Classically it's just a higher amplitude, which means that the field strength is higher.

 

I suppose a high enough energy density will eventually have GR implications, but no quantum mechanical restrictions I know of.

[BenSon]

That's actually a separate issue. In a reflective box, the wavelength must be a multiple of L/2 (i.e. you need to fit a standing wave in it) so a wavelength longer than L/2 will not "fit." But as long as you fulfill the standing wave condition, you can keep adding photons. Classically it's just a higher amplitude, which means that the field strength is higher.

 

I suppose a high enough energy density will eventually have GR implications, but no quantum mechanical restrictions I know of.

Ok thanks. Hey I see your a physics expert you don't have to answer this if you don't want to but I'm just deciding what to do at uni and I was just wanting to know if you do research and if so what? Also would you reccomend physics as a career choice or if you could choose another area of science? Actually this question is to other professional scientists as well. Thanks.

 

Scott

[swansont]

Ok thanks. Hey I see your a physics expert you don't have to answer this if you don't want to but I'm just deciding what to do at uni and I was just wanting to know if you do research and if so what? Also would you reccomend physics as a career choice or if you could choose another area of science? Actually this question is to other professional scientists as well. Thanks.

 

Scott

 

We physicists are generally pretty smart (and modest as hell), so we can be trained to do lots of things. The trick is, if you end up working outside of physics, getting an employer to recognize that. Intelligence, problem-solving and trainability are skills, but not all bosses want that - some want a specific skill set in hand vs. the ability to acquire new skills.

 

I recently read that an advanced degree in physics, gained to do academic research, is one of the worst training-for-compensation payoffs out there. So if you are thinking of that, do it because you like it - work will be interesting - not because you expect to get rich, because you probably won't.