## Archive for the ‘Physics’ Category

### 97 per cent of climate scientists agree…

Monday, May 20th, 2013
 John from wikipedia A study of 4000 abstracts of peer-reviewed papers published in the past 21 years that state a position on global has revealed an astonishing consensus; 97% of these endorsed the position that we are seeing anthropogenic global warming (AGW)[1].

Warning Science is not a democracy in the sense that if most scientists agree, then it must be correct.

Also note;

• 66.4% of abstracts expressed no position on AGW.
• 32.6% endorsed AGW.
• 0.7% rejected AGW.
• 0.3% were uncertain about the cause of global warming.

Reference
[1]John Cook et al (2013), Quantifying the consensus on anthropogenic global warming in the scientific literature, Environ. Res. Lett. 8 024024

Friday, May 17th, 2013
 http://animatedcliparts.net/ Hofstadter’s butterfly is a fractal pattern that describes the behavior of electrons in a magnetic field. Such a fractal was predicted by Douglas Hofstadter, which he described in 1976 [1]. It is a very rare example of a fractal arising from quite fundamental physics.

However, all earlier attempts to experimentally observe see this pattern were unsuccessful. The wonder material graphene, first made by Andre Geim and Kostya Novoselov from the University of Manchester in 2004, came to the rescue…

For the first time ever a teams from Columbia University, the University of Manchester and MIT have experimentally observed this pattern [2,3,4].

Plot of electron density (horizontal axis) versus magnetic-field strength from data obtained by the Columbia team. (Courtesy: C R Dean et al. Nature 10.1038/nature12186)

Hofstadter’s butterfly spotted in graphene, PhysicsWorld.com

References
[1] Douglas R. Hofstadter (1976). “Energy levels and wavefunctions of Bloch electrons in rational and irrational magnetic fields”. Physical Review B 14 (6): 2239–2249.

[2] C. R. Dean et. al, Hofstadter’s butterfly and the fractal quantum Hall effect in moiré superlattices, Nature (2013) doi:10.1038/nature12186

[3] L. A. Ponomarenko et. al, Cloning of Dirac fermions in graphene superlattices, Nature (2013) doi:10.1038/nature12187

[4] B. Hunt et. al, Massive Dirac fermions and Hofstadter butterfly in a van der Waals heterostructure, arXiv:1303.6942 [cond-mat.mes-hall]

### Quantum physics and heavy metal

Tuesday, May 14th, 2013
 I’m a middle-aged professor of physics and I love heavy metal. Professor Philip Moriarty.

Professor Moriarty of the University of Nottingham just loves heavy metal. In physicsfocus he explains that the quantum uncertainty is a byproduct of the inescapable fact that atoms have wave-like properties.

### Renaming the Higgs boson

Tuesday, April 23rd, 2013
 Peter Higgs was treated as something of a rock star and the rest of us were barely recognised. It was clear that Higgs was the dominant name because his name has become associated with the boson. Prof Carl Hagen Rochester University, New York (BBC World News)

As you are all probably aware, on the 14th of March 2013 the ATLAS and CMS collaborations at CERN’s Large Hadron Collider (LHC) presented new results that further support the discovery of the so called Higgs boson [1].

This has all reignited the debate on the naming of the standard model scalar boson, as “Higgs” only reflects one of the physicists who made early contributions to the generation of mass within the standard model.

In 1964 Robert Brout & François Englert [2], Peter Higgs [4] and Gerald Guralnik , Carl Hagen & Tom Kibble [4] published papers proposing similar, but different mechanisms to give mass to particles in gauge theories, such as the standard model. All of the six physicists were awarded the 2010 J. J. Sakurai Prize for Theoretical Particle Physics for their work on spontaneous symmetry breaking and mass generation.

2010 Sakurai Prize Winners – (L to R) Kibble, Guralnik, Hagen, Englert, and Brout

The trouble now is that the nomenclature Higgs boson has been around for a while now and remaining it could probably course unnecessary confusion. Also, it is not clear who should decide the new name. Nomenclature in physics, and indeed mathematics, arises largely due to popular usage. The initial name may come from the discoverer, but it still takes the community to use this nomenclature before it becomes standard. Thus, the community would have to change nomenclature and this cannot really be imposed from “outside”.

Naming the particle after the six physicists as BEHGHK-boson, which would be pronounced “berk-boson” is one one possible solution, but not a very nice one!

Pallab Ghosh (Science correspondent, BBC News) discusses this further here.

References
[1] New results indicate that particle discovered at CERN is a Higgs boson, CERN press office 14th March 2013.

[2] Englert, F.; Brout, R. (1964). “Broken Symmetry and the Mass of Gauge Vector Mesons”. Physical Review Letters 13 (9): 321.

[3] Higgs, P. (1964). “Broken Symmetries and the Masses of Gauge Bosons”. Physical Review Letters 13 (16): 508.

[4]Guralnik, G.; Hagen, C.; Kibble, T. (1964). “Global Conservation Laws and Massless Particles”. Physical Review Letters 13 (20): 585.

### Lee Smolin in London

Monday, April 22nd, 2013

Lee Smolin is to mark the publication of his new book, “Time Reborn: From the Crisis of Physics to the Future of the Universe” [1] by giving a talk in London, hosted by the Institute of Physics. The talk will he held at the Institute’s offices in London from 6pm, 22 May 2013.

 In his new book Smolin suggests the laws of physics are not fixed, but rather they evolve in time. This hypothesis maybe a way of resolving some of the open questions in physics, such as the nature of the quantum mechanics and its unification with space-time and cosmology.

A poster for the talk can be downloaded from here (opens PDF)

If interested in attending, you need to register online here.

 Lee Smolin is a theoretical physicist who has been since 2001 a founding and senior faculty member at Perimeter Institute for Theoretical Physics. His main contributions have been so far to the quantum theory of gravity, to which he has been a co-inventor and major contributor to two major directions, loop quantum gravity and deformed special relativity Read more at Smolin’s homepage here.

Reference
[1]Lee Smolin, TIME REBORN: From The Crisis in Physics to the Future of the Universe, April 23, 2013

### Crackpot science at conferences

Thursday, April 18th, 2013
 There is an interesting article on the BBC website about crackpots at scientific conferences. The likes of Bayard Peakes are mentioned, as is the interesting case of Prof Schwartz who won a Nobel prize.

I have fortunately, not seen many crackpots at conferences that I have attended, but I have seem some…

### Einstein’s spooky action at a distance in space.

Wednesday, April 10th, 2013

The International Space Station, image courtesy of NASA

Scheidl, Wille and Ursin [1] have proposed using the International Space Station to test the limits of spooky action at a distance. These experiments could help develop global quantum communication systems.

Part of their plans include a Bell test experiment which probes the theoretical contradiction between quantum mechanics and classical physics. A pair of entangled photons would be generated on the Earth. One of these would then be sent to a detector aboard the International Space Station, while the other photon would be measured locally on the ground for comparison.

According to quantum physics, entanglement is independent of distance. Our proposed Bell-type experiment will show that particles are entangled, over large distances — around 500 km — for the very first time in an experiment…

Professor Ursin

It is also not really known if gravity plays any role in quantum entanglement. These experiments would be the first to really probe the potential effects of gravity.

References
[1] T Scheidl, E Wille and R Ursin, Quantum optics experiments using the International Space Station: a proposal, 2013, New J. Phys. 15 043008 (online here)

“Spooky action at a distance” aboard the ISS IOP News

### Newton lecture 2012: Martin Rees

Wednesday, April 10th, 2013
 The Newton lecture 2012 is now available to watch on the IOP website. Professor Martin Rees, the winner of the 2012 Newton medal, gave the lecture entitled Form Mars to the multiverse.

### 60 years of DNA

Saturday, April 6th, 2013
 This month marks the 60th anniversary of the discovery of deoxyribonucleic acid, or DNA to most of us. In the USA, there is DNA Day, which is a holiday celebrated on the 25th of April. The holiday commemorates the day in 1953 when James Watson and Francis Crick published their paper in Nature on the structure of DNA. It is also the 10th anniversary of the first sequencing of the human genome.

Knot theory
One area of mathematics that has been rather useful in the study of DNA, and in particular how it tangles is knot theory. DNA is tightly packed into genes and chromosomes. This packing can be thought of as two very long strands that have been intertwined many times and tied into knots. Before the DNA can replicate it needs to be arranged much neater than that and so needs to be unpacked. Thus knot theory is important in understanding this “unknotting” of DNA.

The way the knots were classified had nothing to do with biology, but now you can calculate the things important to you.

Nicholas Cozzarelli, in [1].

A knot is just a embedding of a circle in 3d.

The knot diagram of the Trefoil knot

The classification of knots has been a harder problem that one might expect. The general idea is to construct ways to see if two knots are equivalent, meaning they are the same knot. More mathematically two knots are equivalent if they can be transformed into each other via a special kind of transformation known as an ambient isotopy. Such transformations are really just “distortions” of the knot without any cutting.

A powerful way of deciding of knots are the same or not, is to calculate their Jones polynomial [2]. Interestingly, there is a relation between the Jones Polynomial and Chern-Simons gauge theory, which was first discovered by Witten [3].

References
[1] David Austin, That Knotty DNA, Feature Column of the AMS.

[2] Jones, V.F.R. (1985),A polynomial invariant for knots via von Neumann algebra, Bull. Amer. Math. Soc.(N.S.) 12: 103–111

[3]Edward Witten, Quantum field theory and the Jones polynomial, Comm. Math. Phys. Volume 121, Number 3 (1989), 351-399

### Planck backs the ideas of an inflationary epoch

Friday, March 22nd, 2013

The Planck space telescope has produced the most detailed picture yet of the cosmic microwave background radiation (CMBR) [1].

NASA/JPL-Caltech/ESA

Detailed analysis supports the idea that $10^{-32}s$, or there about, the Universe went into a phase of rapid expansion known as inflation. This rapid growth of the Universe explains why the Universe is so big and nearly flat, as well as providing an explanation as to why the CMBR temperature is uniform. More than this, the small anisotropies in the temperature are well explained by tiny quantum fluctuations in the early Universe that get blown-up by the inflationary phase. These small differences seeded the large scale structure of the Universe we see today.

ESA/PLANCK COLLABORATION

Hubble constant
From Planck we also know that the Universe is expanding today at a slightly lower rate than previous estimates have given. The Hubble constant is now revised to 67.3 kilometers per second per megaparsec, which makes the Universe about 80 million years older than WMAP data suggests.

Make up of the Universe
The new data has meant a revision in the proportions of “stuff” in the Universe:

Dark Energy – 68.3%
Dark Matter – 26.8%
Normal matter < 5%

Oddities in the CMBR
WMAP found and Planck has now confirmed, that there is an asymmetry between opposite hemispheres of the sky in the anisotropies of the CMBR. This suggests the rather unnatural possibility that there is a preferred direction in the cosmos. This does rule out some specific models of inflation, but the generic idea is still sound.

The cold spot

The CMBR cold spot is another strange feature that Planck has confirmed. This colder region of the CMBR, 70 µK colder that the average 2.7K was first discovered by WMAP. It is thought a possibility that the cold spot and the asymmetry maybe connected.

Planck telescope peers into the primordial Universe, Nature, 21 March 2013

References
[1] Planck Collaboration, Planck 2013 results. I. Overview of products and results, submitted to Astronomy & Astrophysics, 2013.