A new result for the production cross section of Z boson pairs in proton-antiproton collisions at the 2-TeV Tevatron collider is now public, thanks to the efforts of the CDF collaboration. The measurement, in a nutshell, confirms Standard Model predictions nicely: the cross section is determined to be 1.45 picobarns, with an asymmetric error bar of of +0.60-0.51. The Standard Model, on the other hand, predicts that the cross section is 1.21 picobarns. The agreement of the two numbers, within uncertainties, says that all is well in the searched final state, and no unforeseen effects are at work.
Birth of the Universe from the Zero Energy State
1) There was a pair creation of positive and negative energy in the early universe.
2) The total energy of universe is 0.
Stephen Hawking and Alan Guth et al. argued that gravitational potential energy is negative energy, and that such gravitational potential energy can offset all positive mass energy during a period of inflation.
3) The acceleration in the expansion of the universe observed suggests the existence of positive energy out of mass energy, and alternatively, it corresponds to what the overall gravitational potential energy of the universe has positive value, indicating that gravitational potential energy will not able to offset positive energy.
In the past weeks I have been writing a piece about the Large Hadron Collider for a science popularization magazine, and I found myself squeezing my brain for a good analogy to the work of particle hunters. The idea I had was to convey the importance of energy and intensity, two parameters which must both be maximized by a particle accelerator in order to reach deeper in the structure of matter.
Teaching a subnuclear physics course is a quite refreshing experience.
In general, much of the stuff that one has learned through years of sweating on books slowly degrades and becomes "fuzzy". That fuzzy stuff still give you a warm feeling that you have grasped the important concepts and that you have acquired the necessary culture. But much better than the ignorance of culture is the precise knowledge that a continuous study provides. So when one is forced to re-study what one has forgotten, because of the need to teach a course, the result is pleasing.
I have been again teaching two subjects where electric and magnetic phenomena are important (atomic physics and solid state physics) and met naturally new students. I always tell about the SI system and its history, but ask the students to use "for thinking" the Gaussian-like system (Carl Friedrich Gauss 1777 – 1855, portrait from Wikipedia) , where there is either a strength constant, or the units of charge are defined so that one gets the force as product of the two charges divided by distance. Potential, field energy density and all that are then simply expressed through the field strength, charge, etc, there is definitely no
Everyone has heard of "Fahrenheit 451", the classic novel where big government gets its agenda by increasingly taking away rights in order to mandate fairness.
This article has nothing to do with that. Instead, it is about measurement of the viscosity of a gas at a few billionths of a degree Kelvin, or -459 degrees Fahrenheit. Researchers have used lasers to contain ultra-chilled atoms and measured the viscosity or stickiness of a gas often considered to be the sixth state of matter. The measurements verify that this gas can be used as a "scale model" of exotic matter, such as super-high temperature superconductors, the nuclear matter of neutron stars, and even the state of matter created microseconds after the Big Bang.
This is PART III of the four part series about the Edge discussion between Lee Smolin and Leonard Susskind. After criticizing Smolin the last time in PART II, it is now time to turn on Susskind.
Leonard Susskind is well read, certainly enough to know about the measure (not “measurement”) problem in modern quantum physics (introduced in PART I).
Our present understanding of fundamental physics implies the existence of three generation of matter particles, which we consider structureless and "elementary", both in the sense that they cannot be divided into smaller entities, and in the sense that they are the building blocks of all observed manifestations of matter.
Why is there anything? It is kind of conceivable that there could be no thing 'existing' at all – no world, no universes, no consciousness. However, there is at least something.
The opposite of “there is something” is “there isn’t anything (e.g. observed)” but not “there is (e.g. observed) some nothing”. This is important to avoid much ado about nothing. “Nothing” refers to the absence of anything. “Nothing” is not another something.
H0 charge "clouds" in |4,3,1> state.
In about 1985, while considering a banal problem of scattering from atoms, I occasionally discovered the positive-charge (second) atomic form-factors
describing effects of interaction of a charged projectile with the atomic nucleus :