Running Citizenship

Today's historical referendum in Scotland gives me the opportunity to talk about something I have in mind since I came back from the U.S. earlier this year. It's actually a very trivial concept that originates from the fact that:

When outside Europe, I feel European. When within Europe, I feel Southern European/ Mediterranean. When in Southern Europe, I feel Italian and, finally, when in Italy I definitely feel Sardinian. 

There is actually no contradiction in this Matrioska-like sense of belonging and I'm sure most people who happen to live abroad (which is already a rather subjective concept....) share the same feeling.

Anyway, this is interesting because in physics there is a much deeper and far-reaching concept that is (vaguely) related to the one above: that of the running couplings. In a quantum field theory, the coupling "constants" that define the strength of the couplings among quantum fields are not really constant, but actually their values depend on the energy scales.

As an example, take the most famous coupling constant, Newton's gravitational constant G that appears in the gravitational force law

F= G*mass1*mass2 / distance^2

which simply means that the intensity of the gravitational force between two masses (mass1 and mass2) is proportional to the masses and inversely proportional to the square of the distance. The proportionality factor is nothing but what we use to call Newton's constant and its value is G~6.673×10^{-11} N·(m/kg)^2. Now, Newtonian gravity is a classical theory and there is no such thing like a running G (although the situation might be different in alternative theories of gravity, such as scalar-tensor theories, but this is another story...). Indeed, G is a constant no matter how close the two masses are or how massive the objects are. In a quantum field theory, G would depend on the energy involved, for example on the typical distance of the interaction.

If you think about that, this is a beautiful and elegant concept: it teaches us there's no such thing like "the ultimate theory", but each theory (if consistently quantized) would be different at different energy scales. For example, a theory like electromagnetism (or QED in its quantum version) becomes more strongly coupled as the energy increases. The QED coupling constant (the fine structure constant α) is about α ≈ 1/137 at low energies, whereas one measures α ≈ 1/127 at the scale of the Z boson, about 90 GeV. A theory like quantum chromodynamics (QCD) behaves exactly in the opposite way and it becomes more weakly coupled at high energies. This phenomenon is called asymptotic freedom (because the interaction between particles becomes zero at infinite energy) and its discovery  (by Frank Wilczek, David Gross and David Politzer) was worth the Nobel prize in 2004.

What does this have to do with Scotland? (if anything...) The idea that can be borrowed from particle physics is that of a "running citizenship". In other words, each person changes her/his sense of belonging to some country/community accordingly to the "characteristic scale of the problem". It's something that European people are already experiencing given that economy in Europe is mainly governed on European scales, whereas local regulations are governed by state laws. Something similar also happens for federal countries, although the idea of running citizenship that i'm trying to describe has more to do with sense of belonging than with politics (politics often tries to change the sense of belonging and to tailor it accordingly, though).

In physics, the theory that studies the running couplings is called renormalization group and the running is usually called "flow". In most theories, the coupling either grows or decreases with energy, but for some special theories it asymptotes a constant value, a "fixed point".

As for the running citizenship, my impression is that we better try to have a fixed point for that, because the other two cases are quite catastrophic. The analog of a theory like QED would be a sense of citizenship that becomes smaller and smaller as smaller scales are approached, eventually terminating in individuals that do not belong any community. This would imply a sort of total isolation for each individual. The other case would be funny: an individual would become more and more aware of the global nature of Mankind and would feel like more and more part of the entire Universe as smaller scales are approached (this sounds like a nice outcome but perhaps a bit too Hippie for these times....). The most natural solution would be approaching a limit, a minimum size of the community (which we can perhaps identify with the family or hopefully with something larger than that) and then having each person feeling as a part of a larger community dependending on the context and the environment.

In which category does the running citizenship flow of the Scottish people fall? We shall discover this quite soon and the outcome has probably very little to do with physics.....

Greetings from Mons

Some of the participants of the Mons Meetings 14 held this week at Mons, Belgium, and greatly organized by my colleague and friend Terence Delsate (the guy wearing glasses in the group picture...)

Jordi on Dark Matter @ FameLab 2014

Fame Lab is a competition to find new voices of science across the world. In these events various speakers compete for the best popular science short talk. The events are hosted in various countries and there are competitions at regional, national and international level.

This year Jordi Casanellas (former PhD student in IST-Lisbon and now postdoc at the Albert Einstein Institute near Berlin) attended Fame Lab Germany. As the video below shows, in the first stages of the competition speakers cannot use blackboards (not to mention slides or projectors) and their talk has to be ~3 mins long.

Jordi talked about his field of research, Dark Matter, and in fact did a great job: he passed the regional competition and went to the national finals (see video below), where he placed second!

So, if you want to have an idea of what Dark Matter exactly is (or what scientists actually think it should be...) you don't have to do anything but listen to Jordi's speeches. Enjoy!

Pull back: "Scientist: Four golden lessons" by Steven Weinberg

Just came across this brilliant essay by Nobel Laureate Steven Weinberg, writing about his experience as a young scholar, his first steps in research and the connection between science and epistemology.

The essay is so short and clear that I could have copied it here in its entirety, but I'll just give you one inspirational paragraph:

[...]
Look back 100 years, to 1903. How important is it now who was Prime Minister of Great Britain in 1903, or President of the United States? What stands out as really important is that at McGill University, Ernest Rutherford and Frederick Soddy were working out the nature of radioactivity. This work (of course!) had practical applications, but much more important were its cultural implications. 
[...]

and leave the rest for the original

Vita dura per i neutrini sterili e non solo

Si è appena conclusa a Boston la conferenza NEUTRINO2014 dedicata, così come vuole il nome, ai nuovi risultati sperimentali e teorici che provengono dal mondo di queste elusive e misteriose particelle, per l’appunto, i neutrini.

Ci sono parecchie novità interessanti e volevo quindi fare un piccolo riassunto sulle cose più sfiziose.

Partiamo dalla ricerca dei cosiddetti neutrini sterili, e cioè di quelle particelle ipotetiche che sono state introdotte per spiegare alcune anomalie riscontrate nel corso degli anni da alcuni esperimenti che non si inquadravano nel modello delle oscillazioni a tre neutrini. Il primo esperimento a riscontrare un’anomalia è stato LSND (Liquid Scintillator Neutrino Detector) a Los Alamos, in cui è stato registrato un eccesso di antineutrini elettronici, con significatività di 3.8 sigma, su un fascio pressoché puro di antineutrini muonici. Se interpretati in uno schema di oscillazione a due neutrini, per la particolare configurazione della baseline, L, (la distanza tra sorgente di neutrini e rivelatore) e l’energia, E, da cui dipendono la probabilità di oscillazione di un neutrino muonico ad uno elettronico \[ P_{\nu_{\mu}\rightarrow\nu_{e}}\left(L,\, E\right)=\sin^{2}2\vartheta_{e\mu}\sin^{2}\left(1.267\:\frac{\Delta m_{41\,}^{2}L}{E}\right) \] questo eccesso sarebbe indicativo di un'oscillazione con una piccola ampiezza e un grande \(\Delta m^{2}\sim1\) \(\textrm{eV}{}^{2}\). Appare chiaro che un \(\Delta m^{2}\sim1\) \(\textrm{eV}{}^{2}\), non può essere incorporato in un modello a tre soli neutrini (elettronico, muonico e tauonico) in cui esistono solamente due differenze di masse al quadrato indipendenti. Infatti deve valere la relazione \[\Delta m_{21}^{2}+\Delta m_{32}^{2}+\Delta m_{31}^{2}=m_{2}^{2}-m_{1}^{2}+m_{3}^{2}-m_{2}^{2}-m_{1}^{2}-m_{3}^{3}=0\,\] e dal momento che la differenza di massa al quadrato dei “neutrini solari” è \(\Delta m_{SOL}^{2}=\Delta m_{21}^{2}=7.58_{-0.26}^{+0.22}\times10^{-5}\) \(\textrm{eV}{}^{2}\) e di “quelli atmosferici” è \(\Delta m_{ATM}^{2}=\left|\Delta m_{31}^{2}\right|\simeq\left|\Delta m_{32}^{2}\right|\simeq2.35_{-0.09}^{+0.12}\times10^{-3}\) \(\textrm{eV}{}^{2}\), non vi è spazio per una differenza di massa al quadrato dell'ordine dell'\(\textrm{eV}{}^{2}\), se non in uno schema in cui sia presente almeno un nuovo stato di neutrino massivo \(\nu_{4}\) sterile, per cui possa essere interpretata la differenza di massa al quadrato come \(\Delta m_{\textrm{new}}^{2}\equiv m_{4}^{2}-m_{1}^{2}=\Delta m_{41}^{2}\). Questo neutrino però deve essere sterile, e quindi non deve partecipare a nessuna delle interazioni (tranne quella gravitazionale) in quanto esistono delle misure effettuate al LEP sul decadimento del bosone Z in neutrini, che indicano che il numero di neutrini “attivi” (e cioè quelli che interagiscono per forza debole) deve essere esattamente tre.

"Science in the era of Facebook and Twitter – get used to it" by Heino Falcke

Astronomer Heino Falcke has recently wrote a nice post on the relation between science, dissemination of scientific results and social media.

The post was triggered by the recent debate on the BICEP2 results and contains interesting advices on the new role that scientists and journalists should learn to have in the era of Facebook.

“Science is wrong, most of the time” – I am not sure who said that first, but I am sure someone did so well before me. This is a banality for those who do science at the forefront of our knowledge, yet sometimes it seems very difficult to also accept that view in the public discourse. Well, in the days of Facebook and Twitter it is plain obvious to everyone.


Continue reading on Heino Falcke's blog

Recommended by us: "Is BICEP wrong?"

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Blockbuster Big Bang Result May Fizzle, Rumor Suggests

The biggest discovery in cosmology in a decade could turn out to be an experimental artifact—at least according to an Internet rumor. The team that reported the discovery is sticking by its work, however.

Eight weeks ago, researchers working with a specialized telescope at the South Pole reported the observation of pinwheel-like swirls in the polarization of the afterglow of the big bang, or cosmic microwave background (CMB). Those swirls are traces of gravitational waves rippling through the fabric of spacetime a sliver of a second after the big bang, argue researchers working with the Background Imaging of Cosmic Extragalactic Polarization 2 (BICEP2) telescope. Such waves fulfilled a prediction of a wild theory called inflation, which says that in the first 10^-32 seconds, the universe underwent a mind-boggling exponential growth spurt. Many scientists hailed the result as a "smoking gun" for inflation.

However, scientists cautioned that the result would have to be scrutinized thoroughly. And now a potential problem with the BICEP analysis has emerged, says Adam Falkowski, a theoretical particle physicist at the Laboratory of Theoretical Physics of Orsay in France and author of the Résonaances blog. The BICEP researchers mapped the polarization of the CMB across a patch of sky measuring 15° by 60°. To study the CMB signal, however, they first had to subtract the "foreground" of microwaves generated by dust within our galaxy, and the BICEP team may have done that incorrectly, Falkowski reports on his blog today.

To subtract the galactic foreground, BICEP researchers relied on a particular map of it generated by the European Space Agency's spacecraft Planck, which mapped the CMB across the entire sky from 2009 until last year. However, the BICEP team apparently interpreted the map as showing only the galactic emissions. In reality, it may also contain the largely unpolarized hazy glow from other galaxies, which has the effect of making the galactic microwaves coming from any particular point of the sky look less thoroughly polarized than they actually are. So using the map to strip out the galactic foreground may actually leave some of that foreground in the data where it could produce a spurious signal, Falkowski explains. "Apparently, there is something that needs to be corrected, so at this point the BICEP result cannot be taken at face value," he tells Science.

Continue to read on Science 

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See also http://resonaances.blogspot.fr/2014/05/is-bicep-wrong.html