Here you go! Enjoy!
CERN has called for a press conference today (July 4th) for an important announcement. It turns out that they are reporting the claim of the discovery of a new particle “consistent” with the Higgs boson. It has been a search of 45 years for an explanation of how matter acquires mass. And the search is not yet over with this announcement: more work is needed to be certain that this is indeed the Higgs boson.
Peter Higgs was present in the audience in the conference theatre at CERN, Geneva. He was prompt to congratulate the team for their achievement. The famous boson is named after him and this was really a momentous event for him.
The CMS team, at the Large Hadron Collider (LHC), report that they have seen a signature in the data for a particle weighing 125.3 GeV, which is about 133 times heavier than the proton. If actually confirmed, this will be one of the biggest scientific discoveries in my lifetime, but even more exciting is the fact that this does not close the chapter, it may even open other avenues of research and understanding. And as such, the physicists at CERN say that, currently, the data they have is compatible with the Standard Model Higgs boson…
- What Finding the Higgs-Boson Means (wired.com)
- Higgs boson discovered? Live coverage of the Cern announcement (guardian.co.uk)
- Higgs boson video leaks to Cern website (guardian.co.uk)
Yes, indeed this post is about repulsive polarons, but that does not mean that they are repulsive because they cause revulsion or anything of the sort. We are talking about quasiparticles which are predicted to occur when ‘impurity’ fermionic particles interact repulsively with a fermionic environment. And it turns out that these quasiparticles have now been detected.
Ok, “what is a quasiparticle?” I hear you say. Well, a quasiparticleis a perturbation or disturbance in a medium, whose behaviour is that of a particle and thus for all intent and purposes can be regarded as one. Their study is important in relationship to solid-state physics, condenses matter and nuclear physics as they help us in determining the properties of matter.
Rudolf Grimm (Innsbruck) and a team of physicists have experimentally realised the observation of a repulsive polaron in an ultracold quantum gas. The results have been publised in Nature.
Varios phenomena from condensed matter physics can be experimentally simulated using ultracold quantum gases. In these system, the control that can be achieved over the many-body interactions is grater and this is always helpful.
In order to observe repulsive polarons the physicists used an ultracold quantum gas of lithium and potassium atoms and they control the atomic interactions using electromagnetic fields and RF pulses. The potassium atoms are dirven into a state where they repulse the surrounding lithium atoms. This interaction can be seen as a particle with modified properties – a quasiparticel. Once the researchers analyse the energy spectrum of the system, they were able to demonstrate repulsive polarons.
The observation of these polarons is important as it demonstrates that they can indeed be observed. In condensed matter quasiparticles decay very quickly and this poses the problemof studying them. In this experiments, the researchers say, the polarons showed an almost ten times increased lifetime compared to earlier experiments in similar systems. This opens up the possibility of having a platform for a more detailed analysis of many-body systems that rely on repulsive interactions.
Surely you are familiar with measures of frequency such as the hertz, which tells us about the number of cycles of a wave in a second. This SI unit is named after the German physicist Heinrich Hertz and it so happens that today, 22nd of Feburary it would have been his birthday.
- Heinrich Rudolf Hertz celebrated in a Google doodle (guardian.co.uk)
In 2005, the International Year of Physics, there were a number of events to celebrate the coolness of physics. In that same year the Nature Publishing Group launched Nature Physics.
And so this October Nature Physics celebrates its fifth anniversary and with that they have come up with an anniversary ‘focus’ — a compilation of the material they have published “on the hottest topics over the past five years”, including ‘exotic matter’ and ‘ultracold matter’.
I liked this cartoon in the New Yorker, the original can be found here.
The days of the videotape are long gone; these days Compact Discs (CDs) and Digital Versatile Discs (DVDs) are the technologies of choice not only in the entertainment industry in particular, but also in the world of data storage in general.
Nowadays it is not surprising to be able to store around 4GB of data in a single DVD using equipment that has become ubiquitous in offices and even households. Nonetheless, there is a very vivid interest for increasing the amount of data that can be stored in these media.
In recent years, new advances in optical technology have become promising new avenues to improve data storage. In particular super-resolution seems to be a viable way to increase the density of data that can be stored in a disc without having to change the architecture of existing appliances.
To explain how super-resolution helps in this task let us imagine that our media is a simple A4 page and that data is written using an ordinary pen. For the sake of argument let us imagine that on average 800 words per page cab generally be written. We are now faced with the question of fitting more words per page without having to change the size of our A4 standard. One way of achieving this is to change the size of the font. If we keep on making the size smaller and smaller we finally come across two problems. On the one hand, the tip of our pen has to be small enough to let us write small letters and on the other hand, we should still be able to read what is written on the page. In the optical equivalent of this situation a laser beam takes the place of the pen and a disc that of A4 page.
The resolution in an optical system is limited by the colour of the light used (characterised its wavelength) and the capacity of the system to accept that light (the numerical aperture of the system). In this fashion, by changing the traditional red laser for a blue-violet one, Blu-Ray discs are able to hold 25-50 GB. Super-resolution techniques try to address these problems by exploiting the changes in the optical properties of the disc under the influence of the light, giving rise to nonlinear optical effects that have to be better understood.
There is no doubt that the development of ideas in physics, as well as in many other sciences, has been enriched by the extraordinary elucidation that some familiar concepts in one area can be transferred to another one, and thereby gain new insights into either or both of them.
Analogies are a powerful cognitive tool that allow us to make inferences and learn new aspects from the comparison of two things by highlighting their similarities. In general, the reasoning behind this process involves the abstraction of details from a particular set of problems and the resolution of structural resemblance between previously distinct problems. In the book entitled “Quantum-Classical Analogies” by Dragoman and Dragoman we are presented with an extensive number of analogies drawn between the two seemingly dissimilar worlds of classical and quantum physics. Many of these links are more than mere curiosities as it is patently shown in the book with the discussion of a number of recent developments in different areas of physics. The book is divided in 10 different chapters ranging from analogies between ballistic electrons and electromagnetic waves to analogies in phase space, passing through acoustics and particle optics.
Writing a book like this one is an arduous and ambitious task and as such it is hardly surprising that the final product is somewhat unbalanced in the depth in which the different subjects are treated or in the way the subjects are introduced. In many cases, for instance, the authors jump without warning from discussing a classical system in the light of the quantum case to the opposite point of view, making it difficult for the reader to follow their arguments. It is important to mention that the book is intended to be a catalogue of phenomena shared between classical and quantum physics, rather than a textbook about them. Taking that into consideration, the reader must be aware that most sections contain mathematical statements about the subject under discussion, together with appropriate references. In some cases the mathematical formulation is of great help, specially if the reader has some experience in that particular area, however if the reader is new to the subject, it might be more difficult to grasp the full significance of the analogy. In such cases, the references given are an invaluable asset. Personally, I believe that the later chapters of the book accomplish much better the original aim of the authors.
Finally, as a warning for the interested reader, I would like to point out that the book does not discuss any philosophical or epistemological arguments about the quantum-classical correspondence principle. Similarly, the authors make it quite clear that they do not treat any classical-classical or quantum-quantum analogies and that they concentrate in analogies that imply formal similarities. This book is therefore a very good choice for those interested in bridging ideas from classical physics into the quantum world or visce versa, bearing in mind that only the shades are delineated here, the full picture will have to be sought elsewhere.