Sunday, February 28, 2010

Light Gains AND Loses Momentum At The Same Time

Well, it is only appropriate since we're dealing with quantum optics some time! :)

Just when you thought that the issue has been resolved and one side won, the same problem comes back into center stage. And in the latest twist of the story, it turns out to be a dead tie - BOTH sides are correct. That is, assuming that the latest theoretical explanation present is itself correct.

The question is about the momentum of light going through a dense medium with an index of refraction n.

It is well known than when light enters a material medium it slows down in proportion to the refractive index, n, of that medium. Minkowski and Abraham wanted to know how light's momentum changes as a result. Abraham calculated that the momentum of a single photon within the light is also reduced by a factor n, a result which agrees with our experience of everyday objects – as their speed drops, so too does their momentum. Indeed, a number of powerful arguments have been put forward over the years in support of this position. Prominent among these has been a simple proof based on Newton's first law of motion and Einstein's equivalence of mass and energy, which considers what happens when a single photon travels through a transparent block and transfers some of its momentum to the block, given that the motion of the system's centre of mass-energy must remain constant.

Minkowski's formulation, on the other hand, seems more natural from the point of view of quantum mechanics. As light slows down inside a medium its wavelength also decreases, but quantum mechanics tell us that shorter wavelengths are associated with higher energies, and therefore higher momenta. In fact, Minkowski's approach suggests that the momentum of a single photon of light increases by a factor n as it passes through a medium. This result can also be supported by strong theoretical arguments, among them one that considers what happens when an atom moving at some speed through a medium absorbs a photon and experiences an electronic transition.

Lately, it is thought that the Minkowski's version was pulling ahead, especially with the latest set of results. But hold on to your horses.

According to Barnett, however, both formulations are correct. He says that the one put forward by Abraham corresponds to a body's "kinetic momentum" – its mass multiplied by its velocity. Minkowski's momentum, on the other hand, is a body's "canonical momentum" – Planck's constant divided by its de Broglie wavelength. "These two formulations reflect the fact that in different situations momentum does different things," he adds. "In free space they coincide, but not when inside a medium."

Hum... I think I need to think a little bit more about this one.


Saturday, February 27, 2010

Foreign-Born Scientists At Oak Ridge Lab

This is an enlightening article on some of the "obstacles" of being a foreign-born scientist working at a US National Laboratory, and especially at laboratory such as Oak Ridge National Lab that deals with classified stuff.

Despite the international flavor, ORNL is less welcoming to foreigners than universities and even some of the other national labs, such as Argonne in Illinois and Lawrence Berkeley in California, Pennycook said. That's because they don't have the same security concerns as Oak Ridge, he said.

Most Oak Ridge facilities are dedicated to open science. That includes a powerful stable of supercomputers, featuring the Cray XT5 "Jaguar" - currently the fastest machine in the world. But about a hundred yards from the computing center is another modern, three-story brick building that houses the lab's national security program, which includes classified projects for the military and intelligence agencies, and it's strictly off-limits to foreign nationals.

"We work pretty hard to keep things separate," said Mason, who became ORNL director in 2007, barely a year after becoming a U.S. citizen. "We don't want the open, international world to get into our national security space. We also need to make sure that the national security way of doing things doesn't impede our ability to be players in science in the world."

I'm guessing that the security concerns are similar at Los Alamos, Sandia, and Lawrence Livermore labs.


Friday, February 26, 2010

New Revolutions in Particle Physics - Part 7

The surprisingly entertaining series of lectures by Leonard Susskind continues. Part 7 of this lecture series is now available online. I've updated the original blog page to include this latest part.


Thursday, February 25, 2010

Cosmic Rays, Climate, And The Origin Of Life

Wow. That's a really fully-loaded topic, isn't it? But that's the title of a very informative article in the March 2010 issue of Cern Courier.

This phenomenon has a possible relevance to the origin of life on Earth. The current favourite models for this origin are either on comets in outer space, as Fred Hoyle and Chandra Wickramasinghe suggested, or in the black smokers or alkaline vents that result from volcanic activity in the deep oceans. However, another possibility follows from the famous early experiments of Stanley Miller and Harold Urey, in which they passed a spark through a mixture of liquids (water, methane, ammonia, etc) – the “prebiotic soup". This resulted in the appearance of the basic building blocks of life, such as amino acids, RNA and monomers. One problem, however, was that the available spark energy, from lightning, was thought to be inadequate.

This is where the long-term variability of EAS rates may have relevance. We have shown that there should have been periods during which the EAS rate was higher by orders of magnitude than at present (Erlykin and Wolfendale 2001). Our theory is based on the statistical nature of supernova explosions, which are thought to be the originators of high-energy cosmic rays. Figure 3 shows how, from time to time, periods of high cosmic-ray intensity of tens of thousands of years will occur, as a nearby supernova explodes. This will lead to high lightning rates. One of these, occurring at around 4 Gy before the present (a not unlikely occurrence), could have led to the formation of the building blocks of life via the Miller-Urey mechanism. Life could then have evolved from such a start.

There ya go! You and could have been initiated by cosmic rays! :)


Wednesday, February 24, 2010

The Tevatron in 2009

This Symmetry Breaking article gives a very good summary of a very good year at the old dame of experimental high energy physics - the Tevatron at Fermilab. This workhorse of a collider has had a banner year in 2009, producing a number of significant results and refinement, even if it did not find one of the Holy Grail of elementary particle physics - the Higgs boson.

The experiments have made good use of the torrent of data. In 2009, they published over 100 scientific papers and presented more than 150 new results at physics conferences all over the world. Major highlights include the discovery of the production of single top quarks in the first observation of this extremely rare process. The collaborations made the world’s most precise measurement of the top-quark and W-boson masses with a precision of less than one per cent and one per mille, respectively; and they observed and studied new particles containing b quarks. By combining their data, the CDF and DZero experiments also reached important new conclusions on the possible mass of the proposed Higgs particle, now excluding a mass range near that of twice the mass of the W boson (162-166 GeV/c2).

For people who are not familiar with high energy physics experiments, note one very important thing. The Tevatron isn't just a one-purpose experiment. In other words, even though one of the main reason for its operation is to search for the Higgs, it also provides results in many other important studies of elementary particle physics. No one, and certainly no govt. agency, would fun a multi-billion dollar facility JUST to look for one thing. That's insane and not something anyone can justify spending.

So the same can be said about the LHC. While it certainly would like to hunt for the Higgs, it has a rich set of physics that it can do. And that's just what is expected! No one would be surprise if the LHC produces a lot of unexpected results and observations. That, in itself, is why high energy physicists are excited, regardless of whether they find the Higgs or not.


Tuesday, February 23, 2010

The Invariance of the Speed of Light

I don't normally highlight a preprint on ArXiv, especially if it is still waiting for acceptance for publication (I do make some exceptions, especially by well-known authors). However, this is way too much fun to ignore. Besides, I want to keep a record of it here so that I can find it easily next time some crackpot point to me one of the papers as "evidence".

Early on, I came across this preprint that proclaimed to have found a variation in the speed of light that depends on the motion of the light detector. As is the case with any of these things, I wanted to wait until it gets accepted before mentioning anything about it. After all, there are many of these things that popped up regularly and went nowhere. As far as I know, this has not been published yet.

Still, a rebuttal to this work appeared on ArXiv today. And it's a good one! Read the conclusion:

In conclusion, because of the error we point out above, the claim in [1] that the velocity of light as measured by a moving detector does not equal c is wrong. It is particularly striking that the so called ‘measured’ discrepancy of 200 m/s between the light speed as calculated in the two frames does not depend at all on the measured time of flight of the laser pulse. That is, using the procedure of [1] to find cO, any random number put in for the time of flight T would give a result that is v0 larger than cS. Since the claimed anomalous result does not depend on the recorded time of flight, this experiment has, in fact, measured nothing.

I love it! :)

I think that actually, the original paper might be a good exercise for an advanced level physics course to pick apart and figure out what went wrong.

Now that this criticism has appeared, I wonder what is the fate of the submitted manuscript. Would the author write a response? Would the editor and/or referee of the journal be aware of this criticism?


Topological Insulator

Topological insulators seem to be the latest hot topic of study in condensed matter physics. This review, which presumably will soon appear in Rev. Mod. Phys., provides a comprehensive review of our understanding of this complex and rich system.

Abstract: Topological insulators are electronic materials that have a bulk band gap like an ordinary insulator, but have protected conducting states on their edge or surface. The 2D topological insulator is a quantum spin Hall insulator, which is a close cousin of the integer quantum Hall state. A 3D topological insulator supports novel spin polarized 2D Dirac fermions on its surface. In this Colloquium article we will review the theoretical foundation for these electronic states and describe recent experiments in which their signatures have been observed. We will describe transport experiments on HgCdTe quantum wells that demonstrate the existence of the edge states predicted for the quantum spin Hall insulator. We will then discuss experiments on Bi$_{1-x}$Sb$_x$, Bi$_2$Se$_3$, Bi$_2$Te$_3$ and Sb$_2$Te$_3$ that establish these materials as 3D topological insulators and directly probe the topology of their surface states. We will then describe exotic states that can occur at the surface of a 3D topological insulator due to an induced energy gap. A magnetic gap leads to a novel quantum Hall state that gives rise to a topological magnetoelectric effect. A superconducting energy gap leads to a state that supports Majorana fermions, and may provide a new venue for realizing proposals for topological quantum computation. We will close by discussing prospects for observing these exotic states, a well as other potential device applications of topological insulators.


Edit: This review has now appeared on Rev. Mod. Phys. The exact reference is: M.Z. Hasan and C.L. Kane, Rev. Mod. Phys. v.82, p.3045 (2010).

UK Funding For Homeopathy Should Be Cut

I seldom make reference to another blog, but this is one of the few times I will, because it is such an excellently-written blog article.

This blog entry reports on the recent recommendation, in the UK, to cut public money from being spend on research on homeopathy. The recommendation is contained in the report titled "Evidence Check 2 - Homeopathy". It was produced by the House of Commons' Science and Technology Committee. I'm guessing it is a recommendation for the MPs over there to stop such funding.

As the blogger has said, for once, the politicians are getting it right, and getting the right advice. To fund something that, for such a long time still cannot clearly established its existence, is futile. It is not the sign of a valid phenomenon. Yet, people buy into it based entirely on anecdotal evidence.


Phonon Lasers

Amazing advancement this week in the area of producing phonon lasers. Two new papers published by two different groups have made significant progress in producing such a thing.

Despite all the similarities between photons and phonons, no phonon lasers have been developed up until now. The difficulty, ironically, can be traced to the same fact that makes phonon lasers so desirable [4]—the comparatively short wavelength of sound, which causes spontaneous emission processes to dominate over stimulated emission unless one modifies the density of phonon states by employing high-quality acoustic resonators.

You also can get the actual papers for free from that link.


Monday, February 22, 2010

More "Rate of Speed"

I did my rant about the erroneous use of the phrase "rate of speed", when the person using it simply means "speed". This is the latest use of it by the Orange Country Register:

An initial investigation indicates that the Cadillac SRX was traveling at a high rate of speed southbound in the carpool lane when the driver lost control, veered across all lanes and struck the sound wall along the on-ramp, said officer Denise Quesada of the CHP.

So look at the INTENTION of what the report is trying to say. It is trying to convey the message that the vehicle was traveling VERY FAST, i.e. "high speed". So instead of saying what it should say, i.e. high speed, it got cute by writing "rate of speed", which in this case, since the vehicle is moving linearly, means ACCELERATION!

They'll never learn!

But what was funny is that one of the comments listed with this story was someone pointing to my blog entry on this bad usage! :)


Heinrich Rudolf Hertz

A rather concise biography of Hertz on Wired today.

Hertz devised an oscillator made of two polished brass knobs separated by a tiny gap. Each one was wired to an induction coil. With the juice on, sparks jumped the gap between the two knobs. Those sparks, Hertz hypothesized, would — if Maxwell was right — generate electromagnetic waves. It was the first designed transmitter.

For a receiver, he made a wire loop with tiny knobs on opposite sides of a small gap. He placed this device a few yards away. The two devices were not wired to each other, but sure enough, sparks in the transmitter produced sparks in the receiver.

Hertz had demonstrated that Maxwell’s waves exist. He went on to time them, demonstrating that their speed of transmission is, as Maxwell had also predicted, the speed of light.

It is on his shoulder, and the shoulders of so many others, that we stand today with our progress and knowledge. What we accept now as "obvious" were not so, and took the ingenuity of people like him to discover and innovate.


Saturday, February 20, 2010

Traveling at Warp Speed Would Kill You

... but not due to what you might think!

William Edelstein, a professor at Johns Hopkins University’s School of Medicine, has thought of another scenario on why those people on the Starship Enterprise would not have survived traveling through space at close to the speed of light. And it has nothing to do with the contortions of warped spacetime either. It is more basic and more well-known that that.

“I put in the Star Trek thing cause it would be dramatic,” he explains. The point of the paper was to really look at the impact of radiation at high speeds, he said. When you travel at high speeds in space “you are basically plowing through hydrogen,” he explained. “What actually happens as soon as they encounter the ship, the atoms split into protons and electrons and the protons mainly go through you and do damage.”

Edelstein said in an interview with the Star that the problem is when travelling in space at close to light speed hydrogen turns into “intense radiation” that kills humans and destroys electronic instrumentation. Even a ship’s hull of 10 centimetres in thickness would do nothing in terms of preventing damage.

In his presentation he said that a fatal dose of radiation for humans is six sieverts. And with his calculations a crew would receive a dose of more than 10,000 sieverts within a second.

So forget about the stuff that we barely know of. Just simple rudimentary high energy collisions that we already know of, and its radiation effects, which we also know of quite well, can already kill you.

Tough luck, space travelers!


5 Minutes With Brian Cox

Here's a 5-minute interview with Brian Cox.


Friday, February 19, 2010

New Revolutions in Particle Physics - Part 6

Part 6 of this lecture series by Leonard Susskind is now available. You may watch it, and the first 5 video of the lecture series, at my earlier blog entry.

There ARE some funny moments in these videos that made me chuckle a few times! :)


Ernst Mach

Here's a short history lesson on Ernst Mach.

Mach’s name was not coined as a term until 13 years after his death in 1916. A Swiss engineer named the variable after Ernst Mach in a 1929 paper to honor the Austrian’s work on the understanding of supersonic flow.

Mach is perhaps most well-known in the aviation community, and in particular the aviation community that flies very fast jets. A Mach number is a dimensionless number that represents the speed of an object moving through a fluid (most commonly air), divided by the speed of sound in that fluid. Mach 1.0 represents the speed of sound in any given fluid.


Thursday, February 18, 2010

The Science of Liberty

That is the title of Timothy Ferris latest book, which I haven't read yet, so let's get that out of the way.

This is a news article on Ferris's book that makes quite a provocative claim: that science and democracy go hand in hand.

"I'm trying to draw attention," said Ferris, "to what I think has always been a fundamental connection between science and liberal democracy, that the reason we had an Enlightenment -- and the democratic revolution that everyone agrees followed from the Enlightenment -- was because of the discovery of science."

I also find it rather fascinating that, towards the end, he mentioned that his most ardent critic are the post-modern left. I can't believe this group of people are still making such noise after being thoroughly embarrassed by the Sokal hoax, and Sokal's continued revelation of what fraud these people are!


Wednesday, February 17, 2010

Gravity’s Effect On Time Confirmed

Another aspect of GR's equivalent principle gets confirmed to a higher precision. This time, it is the "time dilation" due to gravity.

In the experiment each of the atoms was exposed to three laser pulses. The first pulse placed the atom into a superposition of two equally probable states — either leaving it alone to decelerate and then fall back down to Earth under gravity’s pull or giving it an extra kick so that it reached a greater height before descending. A second pulse was then applied at just the right moment so as to push the atom in the second state back faster toward Earth, causing the two superposition states to meet on the way down. At this point the third pulse measured the interference between these two states brought about by the atom’s existence as a wave, the idea being that any difference in gravitational redshift as experienced by the two states existing at difference heights above the Earth’s surface would be manifest as a change in the relative phase of the two states.

The virtue of this approach is the extremely high frequency of a caesium atom’s de Broglie wave — some 3x1025 Hz. Although during the 0.3 s of freefall the matter waves on the higher trajectory experienced an elapsed time of just 2x10-20 s more than did the waves on the lower trajectory, the enormous frequency of their oscillation, combined with the ability to measure amplitude differences of just one part in 1000, meant that the researchers were able to confirm gravitational redshift to a precision of 7x10-9.

But what's more interesting, at least to me, is the name of one of the author of this paper. Someone by the name of "Steven Chu"! :)

This is the 2nd paper that has been published by him after he has assumed his role at the Secretary of DOE. Still, unless I missed something, this must be the first time an active DOE Secretary published a paper in something as prestigious as Nature. The other one appeared in PRL, which is nothing to sneeze at either!


100 Years of Quantum Weirdness

This is actually a rather sensible account of QM and the struggle to deal with the "weirdness" that comes with it. I do have a bit of a disagreement towards the end, though.

So how does culture absorb this fact?

The first wave of reaction appears to have been the New Age movement of the 1960s and 1970s. New Age enthusiasms embraced quantum physics as proof that consciousness was more important than matter and that the world was imbued with spiritual realities of great and grand potential. It seemed very exciting. Unfortunately it was wrong, missing the essential point that quantum mechanics doesn't really "say" anything. It raises questions. It does not answer them. The New Age movement with movies like the infuriating "What the Bleep Do We Know" just inserted its own pictures into a theory that does not allow them.

Good argument against the "What the Bleep..." movie. However, I disagree that QM doesn't really "say" anything, and that it just raised questions. The "description" that QM gives DOES say something. It tells you what to do, where to do, and how to do it. It may not tell you WHY it does it that way, but that's far from saying that it says nothing. Furthermore, the "why" statements are a bit disingenuous. This is because if one examines even classical physics, it also doesn't tell you why. Can someone explains why the classical field works? Why does an electron feels a tug on it when it is in an electrostatic field? Do the Maxwell equations tell you why instead of just how? Why pick on QM only when physics, and science, essentially tells you only the how at the most fundamental level?


Tuesday, February 16, 2010

Using Leftover Valentine's Day Candy To Measure The Speed Of Light

Here's a creative thing to do with leftover candy from Valentine's Day - use it and your microwave to measure the speed of light! :)

Well, actually, you measure the wavelength of the microwave. Then, using the frequency, you get the speed.


Monday, February 15, 2010

Hot Quark Soup Produced at RHIC

A rather neat simulation and explanation of what they are looking at at RHIC. Here's the brief explanation that came with the video:

The Relativistic Heavy Ion Collider (RHIC) is a 2.4-mile-circumference particle accelerator/collider that has been operating at Brookhaven Lab since 2000, delivering collisions of heavy ions, protons, and other particles to an international team of physicists investigating the basic structure and fundamental forces of matter. In 2005, RHIC physicists announced that the matter created in RHICs most energetic collisions behaves like a nearly perfect liquid in that it has extraordinarily low viscosity, or resistance to flow. Since then, the scientists have been taking a closer look at this remarkable form of matter, which last existed some 13 billion years ago, a mere fraction of a second after the Big Bang. Scientists have revelaed new findings, including the first measurement of temperature very early in the collision events, and their implications for the nature of this early-universe matter.

Edit: here's a news article on this from Reuters, and another from the NY Times.

The departure from normal physics manifested itself in the apparent ability of the briefly freed quarks to tell right from left. That breaks one of the fundamental laws of nature, known as parity, which requires that the laws of physics remain unchanged if we view nature in a mirror.


High-Tc Superconductors Are Very Kinky - Update 8

Looks like the cuprate high-Tc superconductors are kinkier than we originally thought!

In the compilation that I've done so far, we first discovered the 70 meV "kink", or band dispersion renormalization. Later on, came another kink at a significantly higher energy scale, at ~350 meV. Now comes news of another kink. This time, due to improved resolution using laser-based ARPES, a lower energy kink has been observed at about 8 meV below the gap.

Two publications/preprints have reported on this. The first one[1] reports that this kink seen in optimally-doped Bi2212 is tied to the optical phonon mode. The second one[2] appears to be reporting the nature of this kink over a wide doping range, and showing that it becomes stronger in the underdoped range. I said "appears", because I couldn't see the PDF document of this preprint on ArXiv. It won't open for me.

So now there are THREE kinks in the band dispersion of these cuprates! Anyway, both of these have been added to my original blog entry.


[1] J.D. Rameau et al. Phys. Rev. B v.80, p.184513 (2009)

Saturday, February 13, 2010

Courtney Love Is Into Quantum Physics?

Say it isn't so!

I thought it was fascinating that actress Anne Hathaway likes reading about physics. The news that Courtney Love, the widow of former Nirvana frontman Kurt Cobain, is into quantum physics kinda scares me a little! :) Look at what she follows:

She also said Robert Graves was her favourite author, that she would take Mozart's music to a desert island and that the work of poet Rilke, along with watching quantum physics videos on YouTube, had affected her music.

Oh dear! She probably watched "What the Bleep do we know!"


Assessing the State of US Science and Engineering

This is a short interview with the chairman of the board’s Science and Engineering Indicators committee Louis Lanzerotti about the latest report on the 2010 Science and Engineering Indicators. It is interesting that, whether it was abbreviated or not, his analysis of the public support for science doesn't go that deep.

What did you find out about the public perception of science?

The interesting thing is that the perception of science and of engineering remains really very high in the United States.… Those who think it’s a very positive element of our American life … the percentage of the population who believes that is very high. It’s of the order of 75 to 80 percent, versus those who think that it’s a detriment for society, which are 10 percent or less. There have been some blips in that trend up and down by a few percent over the years, but if one does a sliding mean through all that data, one finds that that trend is basically a constant. The American public has a very strong view of the importance of science and engineering for our country. I think a very important point is that scientists rank as high in public respect as do firefighters. They’re second only to firefighters.

Now compare that to the analysis done by Chris Mooney, which goes a lot deeper than that. I still don't see anything here to change my perception that the public's support for science is not based on an understanding of what it is that they are supporting, but based on a PERCEIVED importance of what science is doing.


Friday, February 12, 2010

New Revolutions In Particle Physics - Part 5

Part 5 of the lecture series by Leonard Susskind has now appeared. I've updated all the video available from this lecture series in the relevant blog entry. So don't miss it if you haven't checked it out yet.


New Delay at the LHC and More Questions for the Tevatron

Looks like the LHC will not run at 10 TeV as originally anticipated during this run. It will continue at 7 TeV through 2011, and then go on a year-long repair hiatus with the hope of ramping to its maximum design energy when it gets back in 2012.

Strangely enough, those working at the Tevatron aren't gung-ho on trying to push for the Tevatron to run on into 2012.

Curiously, though, Fermilab physicists did not immediately clamor to run their 27-year-old Tevatron collider for an extra year through 2012. That contrasts to last year, when in response to a delay to the LHC, Fermilab scientists pushed hard to run the Tevatron through 2011, a move the U.S. Department of Energy (DOE) supports (Science, 20 February 2009, p. 993). This time, Fermilab physicists say an extra year's worth of data might not be worth the expense. "It's not like we're rushing out and saying ‘We want to run in 2012!’" says Fermilab's Dmitri Denisov, co-spokesperson for the 510-member team working with the D0 particle detector. "But we want to keep the possibility open."

Even at 7 TeV, there's plenty of physics to be done at the LHC. Already there are indications that they are seeing a few unexpected things. So there's plenty to be done in the next couple of years at this energy scale.


Thursday, February 11, 2010

Martin Rees Tackles Space, Politics and Scientific Advice

Lord Martin Rees, President of the Royal Society and the UK's Astronomer Royal, tackles several issues on space, politics, and science advice in this video interview.


Lise Meitner

This is a nice, short article on Lise Meitner and her contribution not only to physics, but to our world as well. She certainly and fully would have deserved the Nobel Prize, and I would think that if the Nobel committee looks back on some of the people they missed giving the award to, Meitner would be way on top.

Having read a few of her biographies and life story, I am not only amazed at her dedication and skill as a scientists, but also her resolve considering all the obstacles she faced as a woman working in this field at that time. She is one tough woman, and someone that I truly admire as a person.


The Big Bang, Modern Cosmology and the Fate of the Universe: Impacts Upon Culture

This is the text of the lecture given by Lawrence Krauss at the UNESCO/IAU Meeting titled "The Role of Astronomy in Society and Culture" this past Jan. 2009. There are several issues brought up in this lecture that, by themselves, can be the subject of whole lectures themselves.

Suffice to say that this is quite an article to read.


First Physicist in US Congress Retiring

Vern Ehlers, the first physicist to serve in the US Congress, is retiring at the end of his term. One of only 3 physicists currently serving in the US Congress, he has always been a strong supporter of science funding.


Wednesday, February 10, 2010

Quantum Tunneling Composite

Chalk this up for another direct application of QM. This new technology that makes use of quantum tunneling could introduce a "third dimension" to your 2D touchscreen that is so prevalent in many smart phones (i.e. iPhone lookalike) and upcoming tablets like iPad.

The composite works by using spiky conducting nanoparticles, similar to tiny medieval maces, dispersed evenly in a polymer.

None of these spiky balls actually touch, but the closer they get to each other, the more likely they are to undergo a quantum physics phenomenon known as tunnelling.

Tunnelling is one of several effects in quantum mechanics that defies explanation in terms of the "classical" physics that preceded it.

Simply put, quantum mechanics says that there is a tiny probability that a particle shot at a wall will pass through it in an effect known as tunnelling.
QTC-enabled handset

Similarly, the material that surrounds the spiky balls acts like a wall to electric current. But as the balls draw closer together, when squashed or deformed by a finger's pressure, the probability of a charge tunnelling through increases.

When I first read this, my first reaction was "oh, they finally found an application for that!" Let me explain. I did my Ph.D research in tunneling spectroscopy, or more precisely, in point-contact tunneling spectroscopy. What I had was this sharp, pointy tip, and this tip was pushed onto the sample that we want to study. The native oxide barrier on the sample acts as an insulator, and thus, the potential barrier. So one sets up a tunnel junction consisting of the tip-oxide insulator-sample. One can measure the I-V curve if one so desires due to the tunneling current. The more one pushes the tip into the insulating layer, the larger the junction conductance, and consequently, the larger the tunnel current.

{Of course, there is a limit to how hard one can push the tip into the material. At some point, you'll either get an Ohmic contact, i.e. a short, or you break the sample.}

The same can be said about STM system, but here, the vacuum between the tip and the sample acts as the insulating barrier. How much one varies the distance between the tip and the sample surface dictates the conductance and the amount of tunneling current.

So in essence, this new device, the QTC, is the application of what many of us in condensed matter have already known and made use. I guess with the new nanoparticles, they finally managed to find an application for it.


Tuesday, February 09, 2010

Science of the Winter Olympics

With the Vancouver Winter Olympics looming, NBC Learn has launch an educational website on the Science of the Winter Olympics. It has a collection of videos discussing the various physics (mechanics) aspects of the various sports in the Winter Olympics.

The site also has a bunch of other educational items and videos suitable at almost any level.


Monday, February 08, 2010

The First Lasers

In light of the 50th anniversary of the laser (pun intended), the AIP has a wonderful historical account of the birth and development of the laser. This is an opportunity not only to read about how the laser came to be what it is today, but also be aware of all the important figures in its history, and not just those who got the Nobel prizes for it.


Job Outlook for Theoretical High Energy Physicists Sucks

In case you missed Peter Woit's blog entry, or Erich Poppitz latest data, you might want to read a summary of it here.

I've always stressed the issue of "employability" when students asked me about majoring in various areas of physics. While this is not an issue when students first get into grad school, it will be a huge issue when they graduate and looking for jobs. This doesn't mean that one shouldn't go into areas such as theoretical high energy physics. It means that one needs to be aware of the challenges when doing such a thing and be prepared for not finding the job that one wants. There has to be a backup plan in anything, and more so when one is specializing in an area with very limited employability.


Sunday, February 07, 2010

Steven Chu Plays "Not My Job"

If you haven't listened to this, you ought to, because it is hysterical. Steven Chu plays "Not My Job" on NPR's "Wait, wait, don't tell me".

You also get to learn a little bit about Steven Chu, but more than anything, this is rather entertaining and utterly funny. Too bad he didn't do as well as George Smoot on "Are You Smarter Than a 5th Grader?" game show, but this is to be expected since the questions were "not his job"! :)


Friday, February 05, 2010

Teaching and Understanding of Quantum Interpretations in Modern Physics Courses

We all know that teachers and instructors can have a profound influence in the way a student not only understands a subject, but also how he/she thinks about how to view something. This notion is further reinforced by this study on how students interpret the complexity of quantum mechanics. {Note that you can get full access to the paper}

Abstract: Just as expert physicists vary in their personal stances on interpretation in quantum mechanics, instructors vary on whether and how to teach interpretations of quantum phenomena in introductory modern physics courses. In this paper, we document variations in instructional approaches with respect to interpretation in two similar modern physics courses recently taught at the University of Colorado, and examine associated impacts on student perspectives regarding quantum physics. We find students are more likely to prefer realist interpretations of quantum-mechanical systems when instructors are less explicit in addressing student ontologies. We also observe contextual variations in student beliefs about quantum systems, indicating that instructors who choose to address questions of ontology in quantum mechanics should do so explicitly across a range of topics.

It appears that if the students were left to their own devices, i.e. the instructor made no explicit interpretation, they tended to adopt a realist view of QM.

I've yet to read this paper fully and more closely (hey, I have a lot of things to do this week! :)). But you're welcome to it. If you are, or have been, an instructor in a similar class, I would be very interested to hear what you have to say, and especially on your approach for such a class.


AAAS 2010 Annual Meeting

Hey, is anyone reading this will be attending the upcoming AAAS Annual Meeting in San Diego? If you are, I would be so grateful if you could contact me. You may e-mail me, or if you don't have my e-mail address, please leave a comment to this blog with your contact info. Don't worry, this blog is moderated, and your comment will NOT appear in public (I PROMISE!), so your contact info will be kept private and will be deleted.

Thanks a bunch!


Thursday, February 04, 2010

Weinberg Says That Obama Gets Space Funding Right

In light of the new proposed 2011 budget and the Obama Administration decision to cut spending on the human spaceflight to the moon and Mars, Steven Weinberg wrote an opinion piece that praised this step.

The manned space flight program masquerades as science, but it actually crowds out real science at NASA, which is all done on unmanned missions. In 2004 President George W. Bush announced a new vision for the space agency: a return of astronauts to the moon followed by a manned expedition to Mars. A few days later NASA's office of Space Science announced major cutbacks in its important Beyond Einstein and Explorer programs of unmanned research in astronomy. The explanation was that they "do not clearly support the goals of the President's vision for space exploration."

Soon after Mr. Bush's announcement I predicted that sending astronauts to the moon and Mars would be so expensive that future administrations would abandon the plan. This prediction seems to have come true.

The cost-to-benefit ratio, at least in terms of science output, is just not there for human spaceflight, and even the ISS for that matter. Decisions to do this have been based predominantly on politics, and funding appropriate home constituents. When one argues that such cutbacks can hurt science, and then to hear very prominent scientists disagree with that assessment, it kinda throw that claim into question.


Wednesday, February 03, 2010

Cycling Physics

If nothing else, this physics teacher is certainly very resourceful, and not to mention, probably in a very good physical shape as well!

On Thursday Davis will be trying a new kind of demonstration: he will spend the entire teaching day — 7 hours — pedaling his bicycle on rollers. The purpose is to give his students a visual lesson in work, power, energy, angular momentum, torque, and other topics.

Good luck to him, and hopefully, his students do learn a bit of physics from all this.


Tuesday, February 02, 2010

High-Tc Superconductors Are Very Kinky - Update 7

A new preprint appearing on ArXiv today adds another argument for the phonon mode (or modes) as being responsible for the kink in the band dispersion of high-Tc superconductors observed from ARPES measurement. The work studied the heavily-overdoped (Bi,Pb)2Sr2CuO6 and used a very high resolution, laser-based ARPES technique.

Abstract: Super-high resolution laser-based angle-resolved photoemission spectroscopy measurements have been carried out on a heavily overdoped (Bi,Pb)2Sr2CuO6 (Tc> 5 K) superconductor. Taking advantage of the high-precision data on the subtle change of the quasi-particle dispersion at different temperatures, we develop a general procedure to determine the bare band dispersion and extract the bosonic spectral function quantitatively. Our results show unambiguously that the 70 meV nodal kink is due to the electron coupling with the multiple phonon modes, with a large mass enhancement factor Lamda= 0.42 even in the heavily over-doped regime.

I've updated my original blog entry on this topic to reflect this new preprint.


The Story Behind RealD 3D Technology

A rather nice "historical" account of RealD's emergence in the movie industry. Certainly, if you've seen any 3D movies within the past few years, and certainly if you've seen "Avatar", you would have experienced the more pleasant way of viewing 3D movies than those nasty bi-colored glasses.

The history of RealD's Boulder brain trust stretches back to work at the University of Colorado in the 1980s.

In 1987, CU received a federal award to establish the Center for Optoelectronics Computing Systems, which initially had strong focuses in physics and liquid crystal technologies, said Kate Tallman, director of technology transfer for CU-Boulder.

The center spawned a number of inventions related to color display technology and color projection technology and would be the incubator for a spin-off launched by two of its CU scientists.

I think that it is extremely important to make sure the public realizes where the seed money came from and from what initial research effort. Too often, what we get today is never connected to the original work that spawned off so many direct applications, so much so that the public doesn't see their tax dollars at work when it was invested into science and technology.