Cosmic Order and the Higgs Force

by Nicholas Mee on August 9, 2017

Tracking down the Higgs boson took almost fifty years, so the announcement of its discovery by the Large Hadron Collider (LHC) in 2012 was a momentous occasion. Strange as it may seem, the theory that predicted the existence of this elusive particle was devised to explain one of the great mysteries of the world around us — how the universe froze!

The Day the Universe Froze

In the earliest moments of the universe a single unified force controlled the behaviour of matter. But as the universe expanded and cooled below about one trillion degrees some of its symmetry was lost, or at least hidden. Ever since, the electroweak force has been divided in two parts — the electromagnetic force and the much feebler weak nuclear force — both of which are vital for forming the universe as we know it. The electromagnetic force holds atoms together and comes in handy for running our smart phones and other gadgets, the weak force is essential for the creation of atoms in stars and supernova explosions. How this could happen is difficult to comprehend, but fortunately there are more familiar transitions that can guide our intuition.

Left: The Great Wave by Hokusai. Right: The Sea of Ice by Caspar David Friedrich.

The most familiar example is the freezing of water. As water cools it suddenly changes from a sloppy flowing material to a hard jagged material, spontaneously transforming from a liquid to a solid when the temperature reaches zero degrees Centigrade (at atmospheric pressure). It is only our familiarity with the freezing of water that makes it less surprising than other amazing transformations that materials undergo when they reach a critical temperature. These dramatic metamorphoses are known as phase transitions. They were studied by solid state physicists, most notably the Russian physicist Lev Landau, long before particle physicists borrowed some of their ideas.

Navigating the World’s Oceans

Magnetic compasses enabled mariners to navigate the world’s oceans for many centuries. Iron, nickel, cobalt and a few other metals undergo a remarkable transformation at their Curie temperature, which is 1043 degrees for iron. Above this temperature iron shows no sign of magnetism, but below this temperature it spontaneously magnetizes.

Iron atoms each carry a small magnetic field. Above the Curie temperature all the atoms are jostling about so the fields all point in different directions, with the direction of each field constantly changing, and the total field averages to zero. Below the Curie temperature the magnetic fields of the atoms align themselves and the thermal vibrations are no longer strong enough to disrupt these alignments. The result is that the tiny atomic magnets add together to produce a very large magnetic field — the piece of iron has been spontaneously transformed into a permanent magnet. This is similar to what happens to the Higgs field when the electroweak force is broken.

Left: The disordered atoms of a ferromagnet above the Curie temperature. Right: The aligned atoms below the Curie temperature.


Superfluidity

The Fountain Effect

Helium condenses into a liquid at 4.2 degrees above absolute zero. When cooled further, to just 2.17 degrees, it undergoes a marvellous transformation into a superfluid, a liquid with no viscosity that flows without any resistance. A container that holds normal liquid helium perfectly well will suddenly spring numerous leaks when cooled below this temperature as superfluid helium seeps out through ultramicroscopic pores in the container.

Superfluid helium has many strange and wonderful properties. One of the most dramatic is the fountain effect. A tiny amount of heat applied to the superfluid will cause it to surge out of the top of its container.

It was for applying his theory of phase transitions to superfluid helium that Landau received the Nobel Prize in Physics in 1962.

Scanners, Trains and Particle Accelerators

Many materials lose all electrical resistance when cooled to sufficiently low temperatures. These superconductors have many applications and are now widely used in the manufacture of powerful electromagnets. The Central Japan Railway Company has developed a magnetic levitation or maglev railway system where the trains ride on on a magnetic cushion produced by superconducting magnets. On 21 April 2015, a manned seven-car train reached a world record breaking speed of 375 mph. Services have been running on a twenty kilometre test track for the last twenty years. Now construction of a mainline track between Tokyo and Nagoya is underway with services expected to begin by 2027.

Japanese superconducting maglev trains.

Superconducting magnets were first developed by particle physicists for use in the Tevatron particle accelerator at the American Fermilab laboratory near Chicago. They are now used to focus and steer the proton beams around the LHC. These magnets operate at a temperature of 1.9 degrees above absolute zero and are cooled by superfluid helium. The magnetic coils are composed of niobium-titanium alloy and generate a field of 8.3 Tesla, which is over 100,000 times more powerful than the Earth’s magnetic field. Development is under way of new superconducting magnets composed of a niobium-tin alloy that will increase the magnetic field strength by 50% in an LHC upgrade scheduled for 2026.

The beam pipe of the LHC during maintenance.

The most wide-spread application of superconducting magnets is in MRI scanners in hospitals around the world. You may well have been inside one.

The Crystal Maze

According to the ancient mythologies the universe originated in a state of chaos and our world was born when order spontaneously arose out of chaos.

This is not so far from the cosmology of today. The universe began in a highly symmetric state, but much of the symmetry is now hidden. In its place we have the order and structure that gives us a universe fit to live in.

The formation of crystals breaks translational symmetry.

 

The theory that predicted the existence of the Higgs boson was devised by Peter Higgs and independently by two other groups of physicists in the 1960s. It is known as the Higgs mechanism and is now a key part of the Standard Model — the particle physics equivalent of the Periodic Table. By 2012 the Higgs boson was the last missing piece of the Standard Model. Its discovery was celebrated with the award of a Nobel Prize. There is more information here: Nobel Prize for Higgs and Englert.


Further Information

If you would like to know more about the intriguing story of the Higgs and its role in symmetry breaking, take a look here: Higgs Force: Cosmic Symmetry Shattered.

Further information illustrated with computer generated animations is available on the CD-ROM companion: Higgs Force Interactive.

The following link is to a video that illustrates many of the amazing properties of superfluid helium-4: http://www.alfredleitner.com/superfluid.html

 

 

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