Physics

Tomorrow - that is, November 8th, at 8AM GMT - I am chairing a session titled "Artificial Intelligence for Physics Research, and Physics Research for Artificial Intelligence" at the Vth USERN Congress. The event takes place in Tehran, and is broadcast via zoom. If you are interested in the talks, of which I give some detail below, you will be able to connect through this link.The agenda of the workshop is as follows (those shown are are Tehran times): 11.30-11.55 Tommaso Dorigo, “Artificial intelligence and fundamental physics research” 12.00-12.25 André David, “How we discovered the Higgs…

Every time I lecture my students about the static quark model I find that the construction of hadrons from their constituents is really entertaining. Probably I have more fun than my students as I explain the details, but today you get to be the judge - I am going to explain it here, and test your patience and skills as a matter builder. Hadrons are composite particles made of quarks. The word "hadron" comes from ancient Greek αδρος, which means "thick, bulky". The two hadrons we know best are protons and neutrons, which make up atomic nuclei; but there exist literally hundreds more, which…

For some reason today I remembered that 11 years ago (wow time flies) I wrote a two-parts piece on advices for PhD students doing a thesis in experimental particle physics. As I checked it out, I found that I mostly share the views I had back then (TBH that's not necessarily a good thing - consistency requires you to be as ignorant as you were earlier on). Since I think that stuff I posted over 10 years ago are otherwise lost in oblivion and not picked up by generic google searches, I decided it is time to recycle that text - here it is below, unamended but collated into a single longish…

Particle Physics deals with the study of the elementary constituents of matter, and the interactions that they withstand. When non-insiders hear of elementary particles and the experiments that study them, probably their mind goes to experiments at the Large Hadron Collider, CERN's giant accelerator of protons and heavy ions that produced the collisions used by the ATLAS and CMS experiments in 2012 to discover the Higgs boson. The association with LHC and the Higgs particle is very likely because that discovery took the media by storm when it was announced, and rightly so. Regardless of the…

In large systems of interacting particles in quantum mechanics, groups of particles can begin to behave like single particles. Physicists refer to such groups of particles as quasiparticles and while they live, they are useful in helping us understand superconductivity and superfluidity. But many quasiparticles die after less than one second.  What kills them? How do quasiparticles die? A new paper goes beyond the usual suspect - quasiparticle decay into lower energy states - and identifies a new culprit: many-body dephasing. Over time, many-body dephasing kills the quasiparticle's…

W bosons, what are they? To answer this question, let me first tell you that our world is made of matter held together by forces. If you look deep within, you will realize that matter is essentially constituted by "fermions": quarks and leptons, particles that possess a half-integer unit of spin, in a certain meaningful system of measurement units. Forces, on the other hand, are the result of fermions exchanging different particles called "bosons", particles that possess integer units of spin. But what is spin? Spin, for a macroscopic object, is connected to the rotation of a body around an…

"Anti-scientific thinking" is a bad disease of our time, and one which may affect a wide range of human beings, from illiterate fanatics such as anti-vaxxers and religious fundamentalists on one side, to highly-educated and brilliant individuals on the other side. It is a sad realization to see how diversified and strong has become this general attitude of denying the usefulness of scientific progress and research, especially in a world where science is behind every good thing you use in your daily life, from the internet to your cell-phone, or from anti-cavity toothpaste to hadron therapy…

Sound levels in water often appear to be much higher than in air. It is, however, misleading to compare them directly. This has consequences for understanding important issues in ecology, in particular the impact of humans on marine wildlife, such as whales. Whales regularly have sound pressures in excess of 160 dB. It sounds like a lot, because in air such sound pressures are harmful, but it corresponds to just under 100 dB in air. This is still a high sound pressure, but it is no longer so dangerous. The numbers are different for two reasons. The first is that the reference levels are…

Muons are very special particles. They are charged particles that obey the same physical laws and interaction phenomenology of electrons, but their 207 times heavier mass (105 MeV, versus the half MeV of electrons) makes them behave in an entirely different fashion. For one thing, muons are not stable. As they weigh more than electrons, they may transform the excess weight into energy, undergoing a disintegration (muon decay) which produces an electron and two neutrinos. And since everything that is not prohibited is compulsory in the subnuclear world, this process happens with a half time of…

Have you ever behaved like an a**hole? Or did you ever have the impulse to do so? Did you ever use your position, your status, your authority to please yourself by crushing some ego? Please answer this in good faith to yourself - nobody is looking behind your shoulders. Take a breath. I know, it's hard to admit it. But we all have. It is, after all, part of human nature. Humans are ready to make huge sacrifices to acquire a status or a position from which they can harass other human beings. Perhaps we have the unspoken urge to take revenge of the times when we were at the receiving end of…