Physics
vongehr |
From time to time and against strong resistance from the scientific establishment, inspired scientists come out of the closet and dare to publicly consider whether the future can influence the present. Is it in principle possible that we may be able to partially perceive the future say via evolved emotional responses? Future influence has been proposed by Roger Penrose in order to explain how certain crystals grow. So called quasi-periodic crystals avoid additions of atoms into places and orientations that are perfectly allowed while growing, but whose occupation would lead to future…
The following is an excerpt from a book I am working on intermittently. I do not know whether the project will ever see the light, and it just occurred to me that I could share a tiny bit of it with you in my blog. Enjoy!
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My office in the CDF portakamps is the second on the left after “the crossover”, a corridor which connects the two main aisles. The one next to mine was occupied during those years by Fotis Ptohos, who had been a Harvard University graduate student since tempus immemorabile. That was not such a peculiarity: it was generally understood that in Harvard, Ph.D. studies…
RETRACTION: I have decided to retract three blogs (Deriving … 4/5, 5/5, 6/5+1). I was unable to figure out a reasonable statement concerning gauge symmetry. When the blogs were initially written, I focused on the field equations, mainly the Gauss-like law, and ignored the force equations entirely. Finding a solution that works with the the field and force equations were not looked for. A consistent proposal should do all three things (fields, forces, and solutions) with grace. I have concluded it is not possible to achieve these goals with the Lagrangian as written, hence the retraction.The…
Europe is moving forward at high speed to build ELI (Extreme Light Infrastructure Ultra-High Field Facility), to be completed by the end of the century. The location for the facility will be announced next year, possibly at the opening ceremony of the summer Olympics. Three prototype lasers are being built in the Czech Republic, Hungary and Romania, scheduled to become operational in 2015.
ELI will be made up of 10 beams, each twice as powerful as the prototype lasers, allowing it to produce 200 petawatts of power – more than 100,000 times the power of the world's combined…
There is a certain amount of confusion on the relationship between Einstein's Theory of Relativity and the recent experimental results that seem to point towards neutrinos that are faster than light by an amount of about 7 km/s. So let me try to clarify things by answering to the following question:
If neutrinos travel faster than light by 7 km/s, do we need to modify Relativity?The answer is a clear-cut "Yes"; let me explain why.
Lorentz invariance, which is embodied in the theory of Relativity, has the unescapable consequence that there exists a precise relationship between a free particle'…
What is nothingness? It's a philosophical question, to be sure, but in physics the ground state of the universe can't be described by the absence of all matter, contend some theoretical physicists. There must be a 'quantum vacuum'.
The first theoretical consideration of the spontaneous decay of the quantum vacuum, believed to be a complex state of constantly fluctuating quantum fields with physical properties, dates back to the year 1931, but understanding is still in its infancy.
But it could soon happen that experimentalists are able to witness the spontaneous decay of the vacuum into pairs…
In the OPERA experiment, the distance between CERN and Gran Sasso was approximately 450 miles. The difference between the neutrino arrival and the calculated speed of light was approximately 60 nanoseconds.
If the results are confirmed by FERMI, it would mean the following:
From a satellite orbiting Earth at approximately 450 miles altitude, if you were able to fire both a neutrino and a photon at EXACTLY the same time, when the photon reached the ocean surface, the neutrino would be approximately 60 feet deep.
That would be a cool experiment. Even better, if the…
When we teach, and even communicate with people whom we assume to belong to some sort of common circle with ourselves, we simply assume that our audience knows or at least have heard about certain things.
For example, with people belonging in some sense to physics I would expect that my physics students would at least know about Bessel functions. I was wrong. One has heard the name, the others had not any idea. And they did not know practically how to plot functions on a computer. Two did know sort of, but only using "Origin". And so on. I do not want to complain. They are bright young…
A process which caught some of the LHC Higgs analysts by surprise in the recent run of analyses for summer 2011 conferences is the production of multiple-lepton events by a process called "internal photon conversion in Z events". What is it, and how can we size it up ?
The conversion of a real, energetic photon into a fermion-antifermion
pair readily occurs when the particle traverses a medium: the process is also known as "pair production", and is the leading form of energy loss of energetic photons in matter. It is thanks to it (and to the related process called "bremsstrahlung" of…
A routine check of the hep-ex preprints in the Cornell Arxiv revealed today some interesting papers worth giving a look. At least, they are interesting to me: don't expect me to publicize stuff I do not understand or care about! Also, I should mention that many more interesting papers are daily produced, but one cannot really follow everything...
So here is a short list with minimal commentary, for those of you willing to expand your knowledge with a half hour of paper browsing.
1110.5502 is titled "aMC@NLO Predictions for Wjj Production at the Tevatron", and authored by R. Frederix, S.…