Physics

At the outset, let me  begin with some preliminaries: Consider an evolving spherically symmetrical fluid and divide it into concentric spheres in such a manner that, despite evolution, the number of particles (or baryons) remain fixed for each sphere.  This fixed number for a given sphere could be proportional to a symbol  `r' and which can be a  `co-moving' radial  coordinate. At the surface of such a sphere, let there be a clock tied to the fluid. The time recorded by such a tagged clock ``t'' is co-moving time. The surface area of the sphere, in curved space-time,…

Particle physics experiments usually invest a considerable part of the time used to produce a measurement in the task of determining the corresponding uncertainty on the estimate, or -when a new effect is observed (say a quantity is measured away from zero, when zero would be the "null hypothesis", predicted by the current model)- estimating the statistical significance of the observation. The technology is quite advanced, as physicists have gradually lost their typical autharchy ("statistics is trivial, so I will figure it out by myself") and progressively inherited sound procedures from…

Another confirmation of correct evaluation of controversial HEP measurements awaited me just after the Higgs evidence was presented at CERN. I am sort of embarassed by this compulsory self-promotion, but this is my blog so I will excuse myself ;-) So the story is the following... Some of you might still remember the controversy over the Omega b discovery, at the Tevatron a couple of years ago. The Omega_b, in case you asked, is a very interesting particle, made up by a bottom quark and two strange quarks. Its decay gives rise to a spectacular chain, but the rarity of production and of…

So much sound and fury over the Higgs Boson, signifying what? A complete understanding of the fundamental constituents of the world in which we live? Of the universe of which we are an integral part? No … and yes. High-energy physicists at CERN, the European Center for Nuclear Research, announced this week they are closer than ever to detecting the apparently hallowed boson — or possibly it is called God Particle merely for mass consumption. Its quantification would at once provide breathtaking insights into the infinitesimal domain affecting Earthly life and to the composition of the entire…

Quantum physics describes a universe that is profoundly mysterious. Einstein, arguably the most revolutionary thinker of modern times, struggled greatly with quantum theory. This groundbreaking new perspective, ironically triggered by his own early work, simply didn't fit his views on physical reality. Would quantum theory not have been as successful as it was, Einstein could have brushed it aside. But from the early days, the theory was immensely successful. And no one around him seemed to have any problems with it. Einstein must have felt lonely at times, but he was convinced enough in the…

Eilam Gross is a professor of Physics at the Weizmann Institute of Science of Rehovot, Israel, and a distinguished member of the ATLAS collaboration. That makes him a competitor, since I work for the other experiment around the ring, CMS. But Eilam is also a colleague, especially since we are members of the Statistics Committees of our respective experiments and we cooperate in a joint group to try and converge on common practices for statistical procedures in data analysis at the LHC. Ah, and- I forgot to mention he is the convener of the ATLAS Higgs group| So I am very pleased to feature…

Firm evidence for the discovery of a Higgs particle has now been officially announced. This means the "Higgs ether" exists. But did not Einstein tell us that there is no ether? Poor Albert is getting punched hard these days. We just survived the faster than light neutrino hysteria, and now this. Although in a sense not fundamentally important (physicists hedged their bets and the multiverse allows no Higgs to be true simultaneously), there are dire consequences of the discovery of the "God particle". Some of the more crack pottery science bloggers will be very disappointed about the Higgs…

News like today's new evidence for a standard model light* (~125 Gev) Higgs particle does much for theoretical physics.  In one fell swoop many theories can be ruled out.  While at the same time other theories gain direct support.  Still other theories, and the theorist who propose them, are vindicated for putting their faith in the standard model.  This model that has worked perfectly in every test it has had for 30 or so years.  One area which this will affect in the latter way is that of quantum gravity. Loop quantum gravity (LQG), casual dynamic…

Updates:- Philip Gibbs does a great job, as always, at combining -albeit approximately- the results of different experiments in the Higgs search. He now has even a full combination of LEP II + Tevatron + CMS + ATLAS, where the signal strength, in SM units, fits absolutely bang on for a Higgs mass of about 125 GeV. Please see his article at the link above; but I cannot resist from stealing his most intriguing picture (sorry Phil!): If Phil did his homework correctly, the combination fits well the signal hypothesis and is over three sigma away from the no-Higgs hypothesis at that mass.... This…

The spin 2 story unfolds much like that for spin 1. The stories are so similar, I want to take a step back and take a big picture view. Higgs digression>QED works so darn well because Maxwell's theory works so well. In Maxwell's EM, action happens at a distance. Working instantaneously is a great approximation. It is only when people make refined measurements that something goes amiss. It is QED that provides the corrections. This can be done because the coupling constant for EM is small. A Feynman diagram is a visual way of keeping track of the corrections that need to be made to…