Solitary waves that travel long distances without losing their shape or dying out are a special type of wave called solitons. Although these infinite waves are quite exotic, some theorists believe that there is another type of solitons that is even more special.
Solitary waves that travel long distances without losing their shape or dying out are a special type of wave called solitons. While these infinite waves are quite exotic, theorists from the Quantum Research Institute (JQI), in collaboration with the National Institute of Standards and Technology (NIST), the University of Maryland, and Indian scientists, believe there may be another type of solitons that are even more special.
Expect to find them in certain ultracold gases. The new solitons are not only about rare waves in low-temperature atoms, they will also provide deep insight into other physical systems, including the early universe.
Solitons can form anywhere. In 1830, a Scottish scientist named John Scott Russell first discovered them when he was riding along a narrow canal, where he saw a wave that kept its shape over a great distance, instead of dying out and disappearing. The "singular and beautiful" phenomenon, as Russell described it, has since been observed, created, and exploited in many systems, including light waves in optical telecommunications fibers, vibrational waves that pass through atomic crystals, and even waves created by Bose-Einstein condensation (BEC), an ultracold state of the substance that causes several particles to be in the same ground state. Atoms in a Bose-Einstein condensate can clump together and form a single large wave that travels through the gas. In addition, atomic waves in the Bose-Einstein condensate can split and perform constructive or destructive interference with each other. In Bose-Einstein with weak interactions between the atoms, "dark-solitons" are created, long-range waves that represent the gaps of the atoms that are scattered in the gas, and "bright" solitons (those that really carry matter).
Using a new theoretical method in the researchers' work, they predict a third type of soliton, even more exotic and "immortal", which has never been observed in a physical system. The new soliton can occur in a Bose-Eisenstein condensation created by "hard bosons" - atoms that repel each other strongly and therefore influence each other strongly - they are organized in an egg carton-like structure that is also known as an "optical lattice".
In 1990, one of the study's authors, Radha Balakrishnan of the Institute of Mathematical Sciences in India, wrote a mathematical description of these new solitons, in the context of Bose-Einstein condensation behavior in a gas of strongly interacting atoms. Through observations of Bose-Einstein condensation, the scientists recently realized that Balakrishnan's equations present an almost perfect description of BA condensation in strongly interacting atoms, and they also discovered that this special type of solitons really exists. While all solitons known to date die when their speed approaches the speed of sound, this soliton survives, maintaining its amplitude even at the speed of sound.
If scientists discover a way to create such an "immortal" soliton, this could provide a new window of opportunity for investigating the behavior of quantum systems with strong interaction behavior, which, among other things, could be high-temperature superconductors and magnets. When atoms cool to the Bose-Einstein state they exhibit a transition phase (like the phase transition between ice and water), the new solitons can also serve as an important tool for a better understanding of phase transitions, including those that took part in the early universe, during the expansion and cooling.
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Yael
Definitely acceptable to me. And don't get me wrong, I'm not trying to argue, I just have no knowledge on the subject and I'm trying to ask questions at a level where I can understand the answers.
In any case, I must praise your explanations like his lawyer's and like Ehud's, I won't pretend to say that I understood, but there is no doubt that you know how to explain well what you understand and indeed I learned a little from your explanations. Good job.
Ghost,
Your questions are important, but I prefer not to go in and quibble about topics I'm not knowledgeable about, so as not to mislead.
Yael
In semiconductors, electrons can be either in the "valence band" or in the "conduction band" when there is an "energy gap" between them. The valence band is the lower energy domain so that at zero temperature all the electrons will be at low energy, za in the valence band, and the MLM is actually isolated. When the temperature rises, the electrons have energy, so they have a chance to jump over the energy gap to the conduction band, when the "free space" of the electron is called a "hole", and it behaves in a similar way only with a negative charge. At this point the MLM starts to conduct when the electron and the hole conduct current. The idea is that you need a certain amount of electrons to be excited to the conduction band (and produce electron-hole constants) for conduction to be significant.
Breeze:
I'm not familiar with the expression "particle-hole", and as far as I know Fermi (a little weak on the subject) is meant to explain "electron-positron", but from the expression imbalance it sounds like there is more than one of the two states, unlike the other solitons in the Einstein Bose condensation.
What is a value band?
Is a hole-particle like an electron-positron? And the new soliton the properties of its hole-particle are different from the other solitons? (sorry if the description sounds a bit silly)
Ghost
From the first paragraph of the article it appears that the idea is new and currently only theoretical, it usually takes some time before they or someone else decides to try to demonstrate it in practice.
By the way, in my opinion one of the more beautiful types of solitons (which appear in a variety of different wave types) is a cloud that exhibits solitonic properties, and you can find amazing pictures of it by searching for: morning glory cloud
rationalize
Thanks for the details from the article itself, it does create an impression of being very interesting.
to a ghost
You should not have taken my words literally the soliton is a moving wave without change of shape in this sense it is only similar
For a classical particle that also moves without changing its shape compared to a wave (for example at a given frequency/wavelength) that performs ups and downs during its movement. Although these are waves, they are not electromagnetic waves, so it is not correct to talk about radiation
These are material waves. By analogy you can think of a water wave made up of drops, when we look at the wave we don't notice that it is made up of drops. When talking about holes and atoms the story is more complex. A hole is a lack of a particle in what is known as a Permian sea and is a phenomenon that I find it difficult to explain simply. I will give an example that I hope will not confuse you when you excite a semiconductor an electron from the full valence band rises to the conduction band and pairs of electron holes are formed (the holes are the lack of electrons needed to complete the full band).
When Yael talks about unbalanced relationships between particles and holes, this is an unusual situation because usually for all
An exciting particle is the hole he left behind.
I will try to explain with an analogy that should not be taken for granted. So put the wave composed of drops because you can take a drop out of the center of the wave (without filling the void it left behind) put the drop on the surface of the wave the drop (analogous to a particle) and the hole it left behind are analogs to particles and holes.
I hope I didn't add to the confusion, there are things that are easier to explain with a drawing.
Avi Blizovsky
Is there a possibility that this site will have a translation for certain words as soon as you move the mouse over the word (as there is in all kinds of other sites)?
rationalize
A: What I understood from your words (and also from Ehud's words) is that the new soliton you predicted exists only "on paper", yes?
B: The soliton "behaves" like an atom (both radiation and matter will answer) and when you say "relations between particles and holes" do you mean relations between matter and its own radiation? I understand it right?
Well then, according to the article in "Physical Rabio", they found a way to describe the equation of motion of the immortal soliton. The article is more mathematical than practical - after all, they did not create the soliton in the laboratory, but showed theoretically how a soliton with these characteristics is possible.
The key to the creation of the soliton is to take care of imbalance relationships between the particles and the particle-holes.
The initial conditions are that two bosons cannot occupy the same place in space, (and by using field operators that are anti-commutative for the same place, and commutative for different places, this makes the equation similar to a system of particles with half spin - this contributes algebraically).
In this equation of motion there are two types of densities: the condensation density and the particle density. And unlike what happens in normal solitons, in this case the two densities are not the same.
And finally, unbalanced relations between the particles and holes is what creates the independence of the equation quickly. Therefore, the changes in speed do not destroy the soliton, but only change its properties (amplitude for example).
Thank you attorney
Ghost
As mentioned, solitons are wave packets that manage to maintain their shape and do not undergo dispersion (as far as I know as a result of a non-linear medium), one of their most interesting characteristics is that they have properties that are usually attributed to particles and not to waves, such as their form of dispersion and reflection (as a result of a collision).
You can find an article, which for technical reasons is only partially readable, but gives structured explanations here:
http://physicaplus.org.il/zope/home/he/3/Segev
Trust me Ehud, you know how to explain, you can see that you understand something
Life
Thanks for the compliment, I'm sure there are many other people who understand what it is about on different levels. I try from time to time if I have knowledge on a certain subject to share it.
Ghost
It is difficult for me to determine from the article whether you are wrong in any way ultra-cold gas in the Bose Einstein condensation state
It has existed since 1995 and since then it has been used as a laboratory service. Condensed gas is currently found in at least three universities in Israel. So, in my opinion, there is nothing new in the gas that the scientists used, unless they managed to condense gas particles of a different element that they have not yet managed to condense (I don't think this is the case).
Regarding the wave equation, I assume that you are right, they found a new solution and probably succeeded in producing it in an experiment.
A soliton is not like a laser beam but more like a projectile or particle. A laser beam basically consists of radiation at a given frequency
(For the sake of abstraction we will call it a given color) A soliton is a wave packet (a collection of different colors) for each color its own frequency of oscillation and yet the wave packet moves together. There is a difference between solitons in physical systems and the latter mathematical solitons can move through each other without scattering.
Ehud, I follow comments. You are one of the few who understand what this is about.
The rest are chatterboxes.
sympathetic
Correct me if I'm wrong, this is what I understood: that the scientists used an ultra-cold gas (which they hadn't used before) and succeeded with the help of a wave equation (thanks to the same gas) to predict a new soliton? (Sorry for the "rough" wording, I just have no knowledge of it).
And is the soliton (roughly speaking) like a very strong laser beam that does not break even for very long distances?
It's a shame indeed. If I have time I will try to delve into the original article published in "Physical Rabio Letters" and collect interesting pieces of information regarding the new solitons.
Yael
It's a shame that the article (also in the original one) is not more detailed about the nature of the new type of soliton. Bose Einstein condensed solitons have been predicted and observed for many years. In Israel there are several international experts on the subject: Prof. Boris Melamed from Tel Aviv University and Prof. Ami Vardi from Ben Gurion University, both theorists. At Bar-Ilan University there is an experimentalist named Dr. Lev Haikovitz who did famous work in his postdoc in France on solitons in the Einstein Bose condensation.
Incidentally, the fact that Einstein's Bose condensation fulfills the non-lyar Schrödinger equation or by its other name Gross Pitavsky makes it possible to carry out experiments in optics on matter waves!
I added a few more words in the article about Bose-Einstein condensation, thanks Ami Bachar.
Ghost,
Wikipedia states that solitons are waves (with a non-linear description), in which the explosion of the wave balances (or rather offsets) its non-linear elements.
Ghost
No there is no connection between the two. First, a sufficiently low temperature is needed so that all the particles of the gas are in one quantum state and can be described by the Schrödinger equation. The point is that the Schrödinger equation suitable for particles in a condensed state (of Bose-Einstein) is a non-linear Schrödinger equation. Nonlinear wave equations often have solitonic solutions. The soliton is a kind of wave packet when the dispersion relation tends to "spread" them as we are used to seeing and nonlinearity wants to shrink them when these two opposing "forces" balance each other a soliton is created. A soliton is a traveling wave without shape change.
In short, the low temperature allows a description using a (non-linear) wave equation. The wave equation allows solotonic solutions of a progressive wave without shape change.
This time you outdid yourself. The LINK given by Itzik is also an excellent article. The article on a small black hole is also good.
Can someone explain to me if I understood correctly that as the temperature is close to absolute zero the wave maintains stability and thus it can "lengthen"?
Bose Einstein condensation occurs when particles are pushed to the elementary energy level at low temperatures. (It must be bosons and not fermions because there is Pauli's law of prohibition that prevents a large number of fermions from being found at the elementary level at the same time)
An article from the magazine "Galileo"
Explains the above concepts in a popular way
http://www.snunit.k12.il/heb_journals/galileo/005013.html
And Ami, don't let the matter keep you awake next time
The article uses the Bose-Einstein condensation concept a lot and does not even give a hint as to what this concept means. The reader must search in external sources and it is not good that way. Of course, it is not possible to explain every word or sentence and get down to the details of physics, but at the very least a basic concept that repeats itself quite a few times and much of the explanation refers to it and uses it - deserves to be addressed in even one sentence that will give a general background to the uneducated reader.