Physics

A couple of months ago I wrote here about the first observation of a process called "diboson production", a quite rare occurrence in hadronic collisions: for the first time, the CDF collaboration could observe that rare process in events containing hadronic jets, which are usually riddled by enormous backgrounds. The significance of that result, which added no real information to our knowledge of subnuclear physics, was stressed in my article to be the demonstration that similar kinds of events can indeed be mined for rare signals despite the large backgrounds. One of these rare signals which…

"Full many a gem of purest ray sereneThe dark unfathomed caves of ocean bear;Full many a flower is born to blush unseen,And waste its sweetness in the desert air." Thomas Gray, "Elegy Written in a Country Churchyard", vv. 53-56. I have always loved these lines, and besides, as I wrote a few years ago, "The relevance of these verses to the general melancholy of the Higgs hunter at the Tevatron is obvious… Suffices to say that the Tevatron is currently producing of the order of 20 Higgs bosons per day in CDF and D0, and yet they blush unseen, born by dark unfathomed caves of billion-event…

Scientists at the University of California, Berkeley, and Lawrence Berkeley National Laboratory in the US, have performed sophisticated laser measurements to detect the subtle effects of one of nature's most elusive forces - the "weak interaction", and in the process also found the largest effect of the weak interaction ever observed in an atom. Along with gravity, electromagnetism and the strong interaction that holds protons and neutrons together in the nucleus, the weak interaction is one of the four known fundamental forces. It is the force that allows the radioactive decay of a neutron…

The Principle of Maximal Aging - Capturing the Essence of Relativity Ever wondered what is the longest path from A to B? I will give you a definite answer in a minute. Stay tuned.  We first need to go back in our memories and remind ourselves what we learned in physics class. Remember Newton's first law? Newton's first law: “A free particle moves in a straight line and with constant velocity” Einstein was not afraid to overhaul our most basic notions of space and time, but he carefully avoided touching Newton's first law. Rather he extended its application…

The hunt for dark energy is on and ways to find it, such as weak gravitational lensing and baryon acoustic oscillation, hold great promise but are as yet unproven.   Supernovae studies, which depend on measuring the redshift and brightness of distant Type Ia supernovae, are the most reliable. Beginning in the 1980s, methods for finding Type Ia supernovae "on demand" were developed by the international Supernova Cosmology Project (SCP), based at Berkeley Lab and headed by Perlmutter, and adopted in 1994 by a rival team, the High-Z Supernova Search Team. In the fall of 1997 the SCP…

Robert Wald has formulated QFT in curved space time in terms of it's algebra of observables on a manifold.  In doing so he has, perhaps unintentionally, provided framework in which very different theories of quantum gravity look very similar.  Schrodinger, Heisenberg, Feynman...there is more than one formal development of quantum physics.  The problem of this day is integrating quantum physics with gravitational physics.  The Algebraic construction described by Robert Wald in a recent paper could be a fourth such formalism.  The well constructed theories of quantum…

Readers familiar with this blog know that I am a die-hard skeptic on the issue of physics beyond the Standard Model. However, today I am wearing my fluctuation-enthusiast hat, and I will be trying to argue in favor of the possible signal of new physics that is coming out of the Tevatron data. Please do not get confused: everything is still in order. Maybe. The notitia criminis is a new search for resonances in the dielectron mass spectrum, recently published by the DZERO collaboration. The results of the DZERO analysis had a roller-coaster effect on me today. So, in the absence of other…

Call it irreversibility, call it time's arrow, call it the second law of thermodynamics. Fact is that everything evolves in such a way that things get more messy. Disorder rises. Entropy increases. We do not observe the opposite happening. Heat flows from from hot to cold, not the other way around. Fluids mix but don't unmix. Shattered pieces of crystal don't reassemble into a vase. Yet the laws of physics tell us that when studying the evolution of physical systems in all its microscopic details, there is no preferred 'direction of time'. The fundamental laws of physics obey time…

Detailed balance is a simple and powerful rule to describe the dynamics of two-state systems. If you know the probability of a transition from a state A to the other state B of a physical system (in some appropriate time unit), and you also know the probability of the reverse reaction , then you automatically know what is equilibrium condition for N bodies distributed in the two states: . The above equation, together with the hypothesis (for a given total N), provides the "occupation numbers"  and of the two states at equilibrium. Since there are many physical systems in Nature…

Previously thought to be indivisible, with negative charge for all, the electron is one of the fundamental building blocks of nature. A new experiment, however, has shown that electrons, if crowded into narrow wires, are seen to split apart. The electron is responsible for carrying electricity in wires and for making magnets. These two properties of magnetism and electric charge are carried by electrons which seem to have no size or shape and are impossible to break apart. However, what is true about the properties of a single electron does not seem to be the case when electrons are brought…