History and Background

Unit 9

Check your comprehension

High-energy Large Hadron Collider results published

Unit 8

Check your comprehension

~ In what way does Medvedev’s plan differ from Soviet central planning approach?

~ Why do the bureaucrats prefer Russia to stay unintelligent?

By Jason Palmer

Science and technology reporter, BBC News (http://news.bbc.co.uk/2/hi/8505203.stm)

The results from the highest-energy particle experiments carried out at the Large Hadron Collider (LHC) in December have begun to yield their secrets.

Scientists from the LHC's Compact Muon Solenoid (CMS) detector has now totted up all of the resulting particle interactions. They wrote in the Journal of High Energy Physics that the run created more particles than theory predicted.

However, the glut of particles should not affect results as the experiment runs to even higher energies this year.

The LHC is designed to smash together particles and atoms circling its 27km-tunnel in a bid to find evidence of further particles that underpin the field of physics as it is currently formulated.

The December announcement of particle beam energies in excess of one trillion electron volts made the LHC the world's highest-energy particle accelerator.

That makes the new results a unique look at the field of high-energy physics. The experiments, smashing protons into each other, produced a few more subatomic particles known as pions and kaons than the team was expecting.

"The level is somewhat higher than the most popular models had predicted, and it looks like it is going to increase with energy a little bit more steeply than we expected," said Gunther Roland, a CMS collaboration scientist from the Massachusetts Institute of Technology in the US.

"I think it's not going to be a problem, but it is one of the many things that we need to know as we move toward searches for the most rare particles and new physics," Professor Roland told BBC News.

He added that the "extra" particles will be more of an issue when, later in 2010, the LHC dedicates itself to collisions involving ions of the element lead, a markedly heavier pair of targets resulting in an even larger array of particles on impact.

"We'll know much more about that in two or three months when we look at the next higher energy of 7 TeV (trillion electron volts)."

~ What is the LHC designed for?

~ What are “pions” and “kaons”?

The Millennium Prize for resolution of the Poincaré conjecture

In the latter part of the nineteenth century, the French mathematician Henri Poincaré was studying the problem of whether the solar system is stable. Do the planets and asteroids in the solar system continue in regular orbits for all time, or will some of them be ejected into the far reaches of the galaxy or, alternatively, crash into the sun? In this work he was led to topology, a still new kind of mathematics related to geometry, and to the study of shapes (compact manifolds) of all dimensions.

The simplest such shape was the circle, or distorted versions of it such as the ellipse or something much wilder: lay a piece of string on the table, tie one end to the other to make a loop, and then move it around at random, making sure that the string does not touch itself. The next simplest shape is the two-sphere, which we find in nature as the idealized skin of an orange, the surface of a baseball, or the surface of the earth, and which we find in Greek geometry and philosophy as the "perfect shape." Again, there are distorted versions of the shape, such as the surface of an egg, as well as still wilder objects. Both the circle and the two-sphere can be described in words or in equations as the set of points at a fixed distance from a given point (the center). Thus it makes sense to talk about the three-sphere, the four-sphere, etc. These shapes are hard to visualize, since they naturally are contained in four-dimensional space, five-dimensional space, and so on, whereas we live in three-dimensional space. Nonetheless, with mathematical training, shapes in higher-dimensional spaces can be studied just as well as shapes in dimensions two and three.

In topology, two shapes are considered the same if the points of one correspond to the points of another in a continuous way. Thus the circle, the ellipse, and the wild piece of string are considered the same. This is much like what happens in the geometry of Euclid. Suppose that one shape can be moved, without changing lengths or angles, onto another shape. Then the two shapes are considered the same (think of congruent triangles). A round, perfect two-sphere, like the surface of a ping-pong ball, is topologically the same as the surface of an egg.

In 1904 Poincaré asked whether a three-dimensional shape that satisfies the "simple connectivity test" is the same, topologically, as the ordinary round three-sphere. The round three-sphere is the set of points equidistant from a given point in four-dimensional space. His test is something that can be performed by an imaginary being who lives inside the three-dimensional shape and cannot see it from "outside." The test is that every loop in the shape can be drawn back to the point of departure without leaving the shape. This can be done for the two-sphere and the three-sphere. But it cannot be done for the surface of a doughnut, where a loop may get stuck around the hole in the doughnut.

Дата добавления: 2014-10-31