Tetraquarks are hypothetical particles made up by four quarks (two quarks and two antiquarks). Unlike mesons (quark-antiquark pairs) and baryons (three-quark or three-antiquark systems), the quarks in a tetraquark are quite loosely bound within their confinement volume by strong interactions, as can be calculated with the help of quantum chromodynamics. Their tendence to separate into two quark-antiquark systems should yield a very short lifetime, making their observation quite difficult. However, some tentative evidence for their existence exists.
In Italy the debate over the escape of brilliant young scientists to foreign countries has been going on for decades now. Italians like to debate, much less to solve their own problems. So although the problem is clearly identified and a recipe to solve it is evident, nobody does anything to implement the solution. Which, of course, would be to raise salaries to researchers and allow for quicker and easier ways to access a career for young post-docs.

I will try to keep my Newtonian wig on. Digressions will be in well-defined sidebars. Time to serve the meat and potatoes.

The Action for the Newtonian Gravitational Field

Two things go into this action: a mass density and a scalar field:

The Z machine at Sandia National Laboratories is moving us toward a fusion future by stepping into the past - in this case using a 19th century device called a Helmholz coil, which is a pair of circular coils on a common axis with equal currents flowing in the same sense and that produces a nearly uniform magnetic field when electrified. 

In recent experiments, two Helmholz coils, installed to provide a secondary magnetic field to Z's huge one, unexpectedly altered and slowed the growth of magneto-Rayleigh-Taylor instabilities, an unavoidable, game-ending plasma distortion that usually spins quickly out of control and has sunk past efforts to achieve controlled fusion.

Today the Baryon Oscillation Spectroscopic Survey (BOSS) Collaboration announced that they have measured the scale of the universe to an accuracy of one percent.   

At the 1962 Rochester conference in Geneva, the prediction that a particle later called the Omega minus should exist, already proposed in a paper by Glashow and Sakurai, was not considered important enough to be mentioned in any invited or contributed talk. It was mentioned in a comment from the floor by Gell-Mann. The paper proposing the existence of quarks was accepted by Physics Letters only because it had Gell-Mann's name on it. The editor said, "The paper looks crazy, but if I accept it and it is nonsense, everyone will blame Gell-Mann and not Physics Letters. If I reject it and it turns out to be right, I will be ridiculed."

Harry Lipkin, "Quark Models and Quark Phenomenology", in "The Rise of the Standard Model", Cambridge UP 1997
In a guest post written three years ago Giorgio Chiarelli told us the story of how the CDF detector saw its first proton-antiproton collisions, during the night of October 13th 1985. It was a very important moment for the history of the collaboration, the start of a data collection campaign that would last over a quarter of a century. Below I wish to tell you the story of one of the worst radiological incidents in the history of the experiment, which happened a few months after those first collisions were recorded.


A newly discovered system of two white dwarf stars and a superdense pulsar, all packed into a space smaller than the Earth's orbit around the sun, could allow astronomers to tackle the very nature of gravity itself.

The pulsar is 4,200 light-years from Earth and is spinning nearly 366 times per second – it was found to be in close orbit with a white dwarf star and the pair is in orbit with another, more distant white dwarf. 

The three-body system is scientists' best opportunity yet to discover a violation of a key concept in Albert Einstein's theory of General Relativity: the strong equivalence principle, which states that the effect of gravity on a body does not depend on the nature or internal structure of that body.

This blog is straight old Newtonian gravity. A goal is to understand where the three kinds of masses in Newton's Universal Law of Gravity live in the context of the action.

I been having nightmares (a little exaggeration) on trying to contemplate if the arguments stated in EPR paper may have been correct. It is not clear to me whether Bell really did disprove the hidden variables theory.
Is the reality of Quantum Entanglement still an open question?

If we have two entangled particles A and B as an example, has there been any experiment measuring particle A's and freezing that state for a time and measuring B's value anytime later? Most of the experiments I see are continuous streams of photons or particles, split-ted and fed to detectors. But not two isolated systems clearly showing that "spooky action at a distance".