In SUSY we trust: What the LHC is really looking for

In SUSY we trust: What the LHC is really looking for – physics-math – 11 November 2009 – New Scientist

Supersymmetry was a bold idea, but one with seemingly little to commend it other than its appeal to the symmetry fetishists. Until, that is, you apply it to the hierarchy problem. It turned out that supersymmetry could tame all the pesky contributions from the Higgs’s interactions with elementary particles, the ones that cause its mass to run out of control. They are simply cancelled out by contributions from their supersymmetric partners. “Supersymmetry makes the cancellation very natural,” says Nathan Seiberg of the Institute of Advanced Studies, Princeton.

That wasn’t all. In 1981 Georgi, together with Savas Dimopoulos of Stanford University, redid the force reunification calculations that he had done with Weinberg and Quinn, but with supersymmetry added to the mix. They found that the curves representing the strengths of all three forces could be made to come together with stunning accuracy in the early universe. “If you have two curves, it’s not surprising that they intersect somewhere,” says Weinberg. “But if you have three curves that intersect at the same point, then that’s not trivial.”

This second strike for supersymmetry was enough to convert many physicists into true believers. But it was when they began studying some of the questions raised by the new theory that things became really interesting.

One pressing question concerned the present-day whereabouts of supersymmetric particles. Electrons, photons and the like are all around us, but of selectrons and photinos there is no sign, either in nature or in any high-energy accelerator experiments so far. If such particles exist, they must be extremely massive indeed, requiring huge amounts of energy to fabricate.

Such huge particles would long since have decayed into a residue of the lightest, stable supersymmetric particles, dubbed neutralinos. Still massive, the neutralino has no electric charge and interacts with normal matter extremely timorously by means of the weak nuclear force. No surprise then that it is has eluded detection so far.

When physicists calculated exactly how much of the neutralino residue there should be, they were taken aback. It was a huge amount – far more than all the normal matter in the universe.

Beginning to sound familiar? Yes, indeed: it seemed that neutralinos fulfilled all the requirements for the dark matter that astronomical observations persuade us must dominate the cosmos. A third strike for supersymmetry.

Electrodinamica Cuantica QED pe înţelesul tuturor

QED pe înţelesul tuturor – partea 1
QED pe înţelesul tuturor – partea a 2-a
QED pe înţelesul tuturor – partea a 3-a

Special relativity passes key test

Special relativity passes key test – physicsworld.com

Scientists studying radiation from a distant gamma-ray burst have found that the speed of light does not vary with wavelength down to distance scales below that of the Planck length. They say that this disfavours certain theories of quantum gravity that postulate the violation of Lorentz invariance.

Light work wins Nobel for electronics pioneers

Light work wins Nobel for electronics pioneers – physics-math – 06 October 2009 – New Scientist

Fibre Optic

Kao’s work made communication through fibre optics possible over great distances. Glass has a higher refractive index than air, so most light travelling along a glass rod remains trapped inside – a phenomenon known as total internal reflection. But in the early 20th century, guiding light by refraction in this way was possible only over short distances – for instance, it found a role in the instruments used by medics to peer into a patient’s gastrointestinal tract.

Most people thought it was impossible to send light further through optical fibres because of attenuation – the loss of light from the fibre. State-of-the-art optical fibres available in the early 1960s lost light at a rate of 1000 decibels per kilometre. So, communications networks based around optical fibres seemed a remote possibility.

In 1965, Kao was working at Standard Telecommunications Laboratories in Harlow, UK, and suggested that attenuation was due to impurities within the glass of the optical fibre rather than the inherent physical properties of the silica from which the glass was made. With purified glass, he suggested that attenuation rates below 20 decibels per kilometre would be possible.

CCD

Boyle and Smith wondered if it was possible to do a similar job with electric charge: could small “buckets” of electrons be used to represent binary data in a microchip? And if so, how could the data be stored and then moved around to be read out?

The pair developed an ingenious way of doing this. They realised that they could deposit columns of closely spaced capacitors on a chip, each of which could be filled up with electrons when a “bit” of data was to be saved in it. Each capacitor had a “clocking” wire attached to it, and a pulse applied via this wire made the contents of each charge bucket tip into the next one. In this way, a series of “clock pulses” would allow a whole row of bits to be marched off to the edge of the chip, where they would be read as a sequence of ones or zeroes by a transistor.

As the charges were coupled – tipping into the next cell along – the devices became known as charge-coupled devices or CCDs. But because the way they worked was similar to the way low-tech firefighting teams pass buckets of water to each other, the devices also became known as “bucket brigade devices”.

Galaxy study hints at cracks in dark matter theories

Galaxy study hints at cracks in dark matter theories – space – 30 September 2009 – New Scientist

The study shows that there is always five times more dark matter than normal matter where the dark matter density has dropped to one-quarter of its central value.
Undiscovered force?

The finding goes against expectations because the ratio of dark to normal matter should depend on the galaxy’s history – for example, whether it has merged with another galaxy or remained isolated during its entire existence. Mergers should skew the ratio of dark to normal matter on an individual basis.

“There is absolutely no rule in physics that explains these results,” says study co-author Hong Sheng Zhao of the University of St Andrews in the UK.

Physicists Explain How Human Eyes Can Detect Quantum Effects

Physicists Explain How Human Eyes Can Detect Quantum Effects

(PhysOrg.com) — By greatly amplifying one photon from an entangled photon pair, physicists have theoretically shown that human eyes can be used as detectors to observe quantum effects. Usually, detecting quantum phenomena requires sensitive photon detectors or similar technology, keeping the quantum world far removed from our everyday experience. By showing that it’s possible to perform quantum optics experiments with human eyes as detectors, the physicists can bring quantum phenomena closer to the macroscopic level and to everyday life.

Superheavy Element 114 Confirmed: A Stepping Stone To The ‘Island Of Stability’

Superheavy Element 114 Confirmed: A Stepping Stone To The ‘Island Of Stability’

ScienceDaily (Sep. 25, 2009) — Scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory have been able to confirm the production of the superheavy element 114, ten years after a group in Russia, at the Joint Institute for Nuclear Research in Dubna, first claimed to have made it. The search for 114 has long been a key part of the quest for nuclear science’s hoped-for Island of Stability.

PHYSICIST AIMS TO CREATE A UNIVERSE, LITERALLY

PHYSICIST AIMS TO CREATE A UNIVERSE, LITERALLY – The New York Times

”The odd thing is that you might even be able to start a new universe using energy equivalent to just a few pounds of matter,” Dr. Guth said. ”Provided you could find some way to compress it to a density of about 10 to the 75th power grams per cubic centimeter, and provided you could trigger the thing, inflation would do the rest.” In the space of less than a microsecond the new universe would inflate to enormous size and create for itself all the matter and energy it would ever contain. In all respects, it would resemble our own universe. A Universe in a Basement

Physicist Proposes Solution to Arrow-of-Time Paradox

Physicist Proposes Solution to Arrow-of-Time Paradox

A new theory suggests that we don’t observe phenomena where entropy decreases because all evidence from these processes is erased when correlations are removed from the system. Image credit: cguu.com.

Plasmonic Laser Heralds New Generation of Computing

Technology Review: Blogs: arXiv blog: Plasmonic Laser Heralds New Generation of Computing

Stockman has an powerful vision for his device:

“One may envision ultrafast nanoplasmonic chips with a high degree of integration where spasers communicate and control each other through their near fields or are connected with nanoplasmonic wires. These can perform ultrafast microprocessor functions.”