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DanP
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Can a photon gas undergo a Bose Einstein condensation ?
sokrates said:Bose-Einstein condensate is a well-defined term
Phrak said:How do you define it?
Dono. Do you make sense in some way ? Its a physics forum, for god's sake. If you don't understand the terms, don't bother to answer.Phrak said:First: does the question make sense in some way? What's a Bose-Einstein condensate?
Cthugha said:There are well defined differences between lasers and BECs. For example the BEC is supposed to be a macroscopic population of the ground state in thermal equilibrium, while lasers need population inversion and are therefore completely out of equilibrium.
In my opinion the closest thing to a BEC of photons is the topic of nonequilibrium polariton condensation, which is an "in-topic" since 2006 (see for example Nature 443, 409-414 (2006) by Kasprzak et al. http://www.nature.com/nature/journal/v443/n7110/abs/nature05131.html). Here you have a microcavity resonant with some quantum well exciton transition. If you are in the strong coupling regime you get a dressed quasiparticle with mixed excitonic and photonic content. The photonic and excitonic content can be tuned by changing the detuning between cavity and bare exciton. Therefore you can get quasiparticles with a photonic content (and extremely light mass) of 50% to condense. However, this also means extremely short lifetimes of this quasiparticle so that you do not get equilibrium with the lattice, but only an equilibrium of the quasiparticles. As it is basically a 2D-system this is not a "complete" BEC, but rather a Kosterlitz-
Thouless phase transition. Nevertheless it shows some of the essential features of the BEC like macroscopic population of the ground state, spontaneous build-up of coherence and linear polarization, a linear Bogoljubov (Goldstone) mode, quantized vortices and half-vortices and a second order intensity correlation function differing from the value expected for a laser.
However, whether this should be called BEC is still a debate in the scientific community. However, at the moment those in favour of BEC write the "heavier" papers.
Cthugha said:There are well defined differences between lasers and BECs. For example the BEC is supposed to be a macroscopic population of the ground state in thermal equilibrium, while lasers need population inversion and are therefore completely out of equilibrium.
In my opinion the closest thing to a BEC of photons is the topic of nonequilibrium polariton condensation, which is an "in-topic" since 2006 (see for example Nature 443, 409-414 (2006) by Kasprzak et al. http://www.nature.com/nature/journal/v443/n7110/abs/nature05131.html). Here you have a microcavity resonant with some quantum well exciton transition. If you are in the strong coupling regime you get a dressed quasiparticle with mixed excitonic and photonic content. The photonic and excitonic content can be tuned by changing the detuning between cavity and bare exciton. Therefore you can get quasiparticles with a photonic content (and extremely light mass) of 50% to condense. However, this also means extremely short lifetimes of this quasiparticle so that you do not get equilibrium with the lattice, but only an equilibrium of the quasiparticles. As it is basically a 2D-system this is not a "complete" BEC, but rather a Kosterlitz-
Thouless phase transition. Nevertheless it shows some of the essential features of the BEC like macroscopic population of the ground state, spontaneous build-up of coherence and linear polarization, a linear Bogoljubov (Goldstone) mode, quantized vortices and half-vortices and a second order intensity correlation function differing from the value expected for a laser.
However, whether this should be called BEC is still a debate in the scientific community. However, at the moment those in favour of BEC write the "heavier" papers.
DanP said:Dono. Do you make sense in some way ? Its a physics forum, for god's sake. If you don't understand the terms, don't bother to answer.
Phrak said:How does one ignore a member?
DanP said:You focus on a point somewhere between Mars and Jupiter and concentrate. Repeat to yourself "I'm ignoring him" between 414 and 481 times.
Phrak said:I'm sorry to have insulted your intelligence. Really, I mean it. I was attempting to ask "does this question make sense?" Scrolling down through unanswered threads, I thought--and still think, that your question deserved a bump. It's a good one. In fact, it was Einstein who asked himself, can massive bosons behave like coherent light (also bosons) in indistinguishable energy states?
DanP said:No harm done,man. I didn't perceived your lines as a insult on my intelligence. Late last night I went through some of your posts and certainly you do know what you are talking about. Id like to make amends, and I present you my apologies.
Photons are particles of light that are the fundamental unit of electromagnetic radiation. They have zero mass and travel at the speed of light. They are related to light as they are responsible for carrying electromagnetic energy and are the building blocks of light.
Bose Einstein Statistics is a statistical distribution used to describe the behavior of particles with integer spin, such as photons. It was developed by Satyendra Nath Bose and Albert Einstein and is based on the idea that particles with the same properties can occupy the same quantum state.
Photons are affected by Bose Einstein Statistics as they are particles with integer spin and therefore follow the principles of this statistical distribution. This means that multiple photons can occupy the same energy state, leading to phenomena such as stimulated emission and the formation of laser light.
Bose Einstein Statistics is significant in quantum mechanics as it provides a framework for understanding the behavior of particles with integer spin, such as photons. It also helps explain phenomena such as superfluidity and superconductivity, and has implications in fields such as condensed matter physics and cosmology.
No, Bose Einstein Statistics can only be applied to particles with integer spin. For particles with half-integer spin, a different statistical distribution called Fermi Dirac Statistics is used to describe their behavior. This includes particles such as electrons and protons.