A source for learning GRT

Einstein's theory has amazed many people including the inventor himself. As he said, anyone who comprehends it could not help being charmed by its beauty. Unfortunately, this excitement is still not conveyed in a lot of college courses. Here is a link by which one may learn this theory himself.
http://math.ucr.edu/home/baez/gr/

... Thus consciousness becomes the source of what we call scientific reality. The entire creation of the universe(s) is a product of expanding human mind.

This is not true. Because science, as a creation of minds, cannot replace the objects it reflects on. Not only scientists, but also every human look at things in their own way. Despite various reflections upon it, the reality is one. Reflections, however many and ingenious they are, can by no means be called reality. Science is reflections of this kind that are scrutinized by reasoning.

Daily relativistic effects

Albert Einstein came up his special and general relativity theory in 1905 and 1915, respectively. They have withstood various experimental tests, most amongst which are performed at high energy or on huge scale. This is because the SRT has significance usually at high speed while the GRT for massive objects. But, this is not the case any more. Actually, modern technologies have counted SRT for much long time in GPS. While for GRT, the impacts seem much far from daily life. Nevertheless, this recent work [Science 329 (5999), 1676-b.] made a breakthrough. It made use of atomic clocks whose accuracy can be achieved of 10^(-17) second.

Due to the lack of an accessible optical transition in ²⁷Al⁺ for efficient laser cooling and state detection, precision spectroscopy of these ions uses techniques developed in quantum information science. Here, an Al⁺ ion is sympathetically cooled through its Coulomb interaction with an auxiliary "logic" ion that is simultaneously held in the same linear radio-frequency (RF) Paul trap (14). The logic ion also helps prepare and detect the internal state of the Al⁺ ion via quantum logic protocols. In this work, the two Al⁺ clocks used a beryllium (⁹Be⁺) ion (14) and a magnesium (²⁵Mg⁺) ion (11), respectively, as the logic ion. The Al^{+ 1}S₀³P₀ clock transition with frequency f₀ near 1.121 PHz has a narrow (f = 8 mHz) natural linewidth and a corresponding intrinsic quality (Q) factor of f₀/f = 1.4 x 10¹⁷ that permits high sensitivity for detecting small frequency-shifting effects. However, the observed linewidth for the clock transition is limited by the linewidth of the probe laser. We probed the clock transition with a subhertz linewidth laser referenced to a high-finesse optical cavity (15). In the Al-Mg clock, with 300 ms probe duration we obtained a narrow, Fourier transform–limited linewidth, realizing a Q factor of 4.2 x 10¹⁴ with nearly 80% contrast (Fig. 1). This high-Q line provides the basis for high-stability clock operation and sensitivity to small frequency shifts.

Attaching Basic Science To Physicians

The value of basic science plays crucial role in future physicians, as this study showed.

A basic science education establishes a foundational understanding on which medical practice is, or should be, based. Effective patient care increasingly requires that physicians keep pace with rapidly evolving technologies and treatments, continually assimilating a vast amount of new and complex information. Indeed, studies have shown that both experienced and novice physicians form more coherent, durable, and flexible understandings of diseases and their treatments when they can link conditions to basic science concepts.

But there is an even more compelling reason to make basic science education essential for all physicians: stimulating curiosity and creating the scientific habits of mind that are essential for continual learning. Basic science research is a portal to the next generation of medical care. Thus, it is critical that both medical students and residents gain experience in critically assessing and interpreting research, not just in terms of outcomes and clinical effectiveness, but also in the context of biological plausibility and mechanisms. In addition, physicians and physicians-to-be must become familiar with those emerging areas of biomedical science with a potential to affect patient care. Under what circumstances, for example, will personal genome sequences become important for patient care, and what problems and opportunities will they create for a physician?

Seaming is believing

http://www.nature.com/nature/journal/v467/n7314/full/467412a.html

Most of the modern understanding of chemistry, including the very notion of a well-defined molecular structure, rests on the concept of a potential energy surface (PES) — a 3N-dimensional 'landscape' that plots the total energy of a collection of N atoms as a function of the atomic positions. The PES can be used to determine several useful features, such as the most stable configuration of atoms, or the pathway along which atoms 'travel' during a reaction. Intersections of these surfaces (known as conical intersections) are thought to have an important role in transitions from excited states to ground states of molecules, but direct evidence of this has been hard to find. Reporting on page 440 of this issue, Polli et al.¹ use ultrafast optical spectroscopy to follow the motion of the molecule retinal — whose light-induced isomerization forms the basis of vision — through a conical intersection. This provides much-needed experimental evidence of the involvement of conical intersections in de-excitations.

Cosmic censorship violation in 5D

Singularities null the predictability of a physical theory. This issue may be avoided by positing the cosmic censorship, which states that, all singularities are hidden behind the horizons and can not be seen from the rest of space-time. However, this although seems comfortable, but no more than a proposal. Counter examples have already existed [http://en.wikipedia.org/wiki/Cosmic_censorship]. Here is another counter example found in 5D space-time [Phys. Rev. Lett. 105, 101102 (2010)].

Hysterisis loops and the motions of domians

A ferromagnet (or other like materials) exists usually in domains and their polarization makes a loop with varying external polling field. These domains reflect the microscopic symmetry of the systems. The formation of domains is due to long-range interactions, while the intra-domain texture is dominated by short-range behaviors, as expected by the definition. Without long range force, a single domain will be randomly selected, due to spontaneous symmetry breaking. Long range force then modifies this and result in richer structure, with all possible domains occurring conforming to the symmetry. Domains are separated by domain walls, which are usually very thin and allow the order parameter to change gradually from the value of one domain to that of another domain. Domains form randomly (usually think so), in the course of thermal fluctuations, but can be modified by applying external field. The behavior of domains is therefore history dependent. A very quantitative understanding of the dynamics of domains is not easy, especially in the presence of impurities and other factors. A recent study reveals more new aspects of this behavior: Phys. Rev. B 82, 104423 (2010).

NO dark matter detected, yet

Without a wisp of exaggeration, the greatest myth in present physics might be about the so-called dark matter and dark energy. Physicists, fairly speaking, for the moment have not even the slightest definite clue about them. They were motivated for two observations: (1) the rotation velocity of a typical galaxy does not follow the pattern based on Newton's theory; (2) the universe is expanding faster and faster. Fact (1) leads to proposal of dark matter while (2) to that of dark energy. Interestingly, the dark energy term was first hypothesized by Einstein, who later on dismissed it for Hubble's discovery, to find a static and stable universe. This energy never dilute in the course of expansion. It permeates everywhere. People don't know where it comes from, although some suggested it might be vacuum energy (calculations rejected this idea). As regards the dark matter, it is usually hypothesized as some undetected particles other than baryons. They interact extremely weakly with visible matter. Some suggest these might be the so-called Weakly Interacting Massive Particles that are predicted by supersymmetric theory. Detectors have been mounted to settle this issue. A latest survey reports a failure [Phys. Rev. Lett. 105, 131302 (2010) ].

Although the above dark matter idea is popular, it is quite dubious to some physicists, who don't like extra assumptions. In 2004, a German group did a study which reveals running gravitational constant that goes bigger at astronomical scales [Physical Review D 70: 124028 (2004)]. This study might null the necessity of dark matter.

Krauss talks of cosmology in PI

I like this talk on cosmology and how it has played out from the beginning !

Krauss tells students to find "inner scientist" at physics

This is a report about a symposium in The University of Alberta. Mr. Krauss gave a speech. He is a renowned physicist and authored popular science books. More on him: [1]http://en.wikipedia.org/wiki/Lawrence_M._Krauss
[2]http://krauss.faculty.asu.edu/#bio

"We have to be diligent. There are many forces in society working on behalf of ignorance," Krauss said. He also hoped that attendees would find their inner scientist. Part of his goal was to raise awareness of the issues and provide people with the tools to counter non-science in their own discussions.

Event co-ordinator Laura Mazzino said the symposium was created to promote awareness of the topics covered in physics research at the university, from astrophysics and nanotechnology, to geophysics and condensed matter. She hoped Krauss' expertise in the field and communication skills would inspire physics students to promote their work, and get other students and the public enthused about physics.

"We love physics; we are passionate about what we do. We don't do it for the money because we don't make any. We do it for the pleasure, and we would like to share this with everybody else," Mazzino said.

"We want to have more interdisciplinary research that will strengthen the university and also our personal careers," she said.

Two-sentence review of topological insulators

Creativity comes when one finds something interesting where the situation seems rather normal or when one makes a breakthrough where the difficulty seems so considerable that no progress can be made. The discovery of topological insulators is surely of the former type. It is just a combination of two factors:
(1) band structure invariant under time reversal operation;
(2) surface states that exist and cross and expand the whole bulk band gap.

A good article is: Liang Fu and C.L.Kane, cond-mat/0611341

An idea about why gravitational force is weak

The gravitational force is rather weak under usual conditions. This fact is simply accepted and not much inquired. Today, in a colloquium with a very small circle of friends, we came up with a very eccentric idea. Here I would like to make just a record. It is drastically different from the conventionally held view. Since it is very new, it is in its infant stage. However, it is very attractive for these reasons:

(1) Let's assume that, all fundamental fermion particles are spin half and with charges. But no primary mass shall be particularly imposed.

(2) The particles don't interact with each other directly, but rather via bosons. The charges directly couple to photons, as indicated by the common Feynman diagrams, which an incoming charge and an outgoing charge meet with a photon. Due to the conservation of spin, it is necessary that the photon has spin 1.

(3) As widely held, the quantum of the gravitational field, which is represented by a metric tensor, should have spin 2. Now if two spin half charges interacted with a graviton in a way similar to that with a photon, the conservation of spin would be breached. Therefore, it is worth thinking about a simple way out: let the charges couple directly to photons while the photons couple to graviton. In this case, the spin can be conserved.

(4) Now what interesting may be inferred ? First, the masses of the charges emerge rather than be endowed. Second, the gravitational force is higher order effects, explaining its fragility. Third, a connection between mass and electrons may be established.

The thus-described idea is ridiculous, and worth thinking more.

Lattice dynamics

Lattice dynamics are underlying the basics of some smart materials:
(1)Ferroelectricity: optical phonons at play;
(2)Piezoelectricity: interactions between strain (which can be related to acoustic phonons) and optical phonons at play;
(3)Ferroelasticity: acoustic phonons at play;
(4)Multiferroics: spin+optical+acoustic phonons.
(5)Flexoelectricity: interpreted as a secondary piezoelectricity in this Letter [PRL, 105: 127601(2010)]

It is definitely to my great surprise !!!!

You know, all women around me having something to do with science are unanimously repulsing by their looks. Actually, I even don't have any impression about a young and attractive female physicist. Now, thanks to a recent online nomination for attractive physicists initiated by Mr. Zapper in his blog, I'm able to see all the loopholes in my knowledge about women. This is surely regrettable. There thirteen female physicists are nominated and all are charming and young. Really fabulous ! They look like stars rather than scientists ! But they are ! And they are going very well with their jobs ! OK. I'll cite my two favorites among them:

1. Biography:
Dr. Mainzer is a Research Scientist at JPL. For her thesis, she built the First Light Camera for SOFIA (FLITECAM) and observed brown dwarfs with it. She joined the WISE team and JPL in 2003. As the WISE Deputy Project Scientist, she works to ensure that WISE will meet its science requirements. She is also the principal investigator of a project to enhance WISE's ability to find new asteroids. [http://www.cosmicdiary.org/blogs/nasa/amy_mainzer/]

2. Biography:Elisabeth Rieper (Born in 1984)
Appointment: CQT PhD Student
Office: S15-04-12
Phone: +65 6516 5628
Fax: +65 6516 6897
Email: elisabeth.rieper@quantumlah.org
[http://www.quantumlah.org/people/elisabeth]

Does cork bat gives a faster velocity?

I took this excerpt from Arxiv blog:

So-called "corked" bats have been hollowed out and filled with a lighter material, such as cork, to disguise the modification. They are illegal because they allow batters to hit the ball further, or so the anecdotal evidence suggestions. The question for science, of course, is whether this effect is real: do corked bats really send balls further?

The reason bats are modified in this way is to make them lighter. This allows the hitter to swing them faster. But if the goal is to give the ball the highest possible velocity as it leaves the bat, lighter is not necessarily better. In fact the collision efficiency, the ratio of ball velocities before and after being hit, is lower for a lighter bat.

There is another factor, the so-called trampoline effect in which the surface of a hollowed out bat deforms and reforms like a trampoline, thereby increasing the elasticity of the collision. This is known to occur in hollow metal bats but whether this holds true for wooden ones is still open.

How about in a real game ?

Today, we have an answer thanks to some intriguing work by Alan Nathan at the University of Illinois and a few buddies. They've built a cannon capable of firing baseballs in a highly controlled fashion. They've used their machine to send balls at baseball bats modified in various ways and then measured the speed at which the balls impact and rebound.

This they say has allowed them to settle the matter.

They have two results. First, they say the trampoline effect is negligible in corked bats. In other words, there is no increase in the elasticity of the bat-ball collision.

Second, they investigated the trade off between higher bat speed and lower collision efficiency and found no benefit to a corked bat.

"We conclude that there is no advantage to corking a bat if the goal is for the batted ball speed to be as large as possible, as is the case for a home run hitter," they say.

However, there is a caveat. Being able to swing the bat faster allows the hitter to delay the swing for a crucial extra fraction of a second. And this may allow more accurate hits. "So, while corking may not allow a batter to hit the ball farther, it may well allow a batter to hit the ball solidly more often," say Nathan and co.

That could be a significant effect. The study shows that corked bats don't allow balls to be hit any further but this has nothing to do with the question of whether corked bats allow home runs to be hit more often.

That's something that will require a carefully designed study to untangle. In the meantime, corked bats may still confer an advantage, just not in the way everyone thought.

Funny work !

Quantum collapse as obeserved

In the quantum world, there are two types of evolution of an isolated system. One is unitary and continuous in time, while the other is discontinuous and abrupt. Not only that, the latter can not even be predicted. This is sometimes called the random "quantum collapse". Although postulated as a fundamental principle of quantum physics, the direct observation of such discrete jumps has been a fascinating subject since the early times. The observation is very difficult, because it is not easy to maintain a long enough coherence of a system in environemental noise. In a latest work [NATURE|Vol 467|16 September 2010], such observation is rendered in a solid state qubit.

Special relativity comes to the help

In an ideal non-relativistic fluid without viscosity no circulation can be generated from none. This fact makes a challenge in cosmology: the genesis of the magnetic field ubiquitous to galaxies. In this Letter [PRL 105, 095005 (2010)], however, the authors were able to show how this theorem can break because of special relativity. They show that, even for an ideal dynamic fluid, circulation can arise naturally without the help of ad hoc commotions.

We demonstrate that a purely ideal mechanism, originating in the space-time distortion caused by the demands of special relativity, can break the topological constraint (leading to helicity conservation) that would forbid the emergence of a magnetic field (a generalized vorticity) in an ideal nonrelativistic dynamics. The new mechanism, arising from the interaction between the inhomogeneous flow fields and
inhomogeneous entropy, is universal and can provide a finite seed even for mildly relativistic flows.

NCCO and LSCO

These two are the stereotypes of electron-doped and hole-doped superconducting copper oxides, respectively. Although they display striking similarities, their differences may be equally crucial in spotting the fundamental mechanism explaining their exotic properties. The latter now receives more and more attention. Here is a latest study that employs dynamical mean field theory, which is a very newly developed powerful tool, in combination with ab initio compuations to explore the electronic properties of NCCO and LSCO.

Fermilab weighs adding 3 years running

Scientists at the last remaining U.S. particle physics lab have a shot at a major discovery. But pursuing that prize means delaying other projects that could enhance the lab's long-term viability. Should they still go for the glory?

That's the question facing Pier Oddone, director of Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois. Last week, an independent advisory committee urged him to run the lab's 25-year-old atom smasher, the Tevatron collider, for an additional 3 years through 2014. The extension would give Fermilab researchers a chance to beat their European rivals in spotting the most prized particle in physics, the Higgs boson. That chance, the panel concluded, is worth potential disruption in the schedules of other projects. Unfortunately for Oddone, however, it could also cause problems for the U.S. Department of Energy (DOE), which funds the lab, and jeopardize the lab's future.

http://www.sciencemag.org/cgi/content/full/329/5997/1266

Electrons on the surface of topological insulators

Topological insulators are featured with massless surface states that are protected from impurity scattering. Electrons in such states move on the surface, which are usually curved. How would this curvature affect the motions ? This article [Phys. Rev. B 82, 085312 (Published August 12, 2010)] shows that, the electrons shall feel gravity-like force.

Electron scattering in solids is normally associated with impurities, defects, lattice vibrations, and electron-electron Coulomb scattering. Now, in an article published in Physical Review B, Jan Dahlhaus and collaborators from the Instituut-Lorentz at the University of Leiden in the Netherlands show that for surface electrons on a topological insulator, electron scattering can be dominated by a completely different mechanism: geodesic scattering. Geodesics are the generalization of straight lines in curved space. In general relativity, gravitational fields curve four-dimensional spacetime, and particle motion follows geodesic lines shaped by gravity. Strong enough fields cause the phenomenon known as gravitational lensing, an observable deflection of massless particles such as photons.

The surface electrons of a topological insulator behave as massless particles and are constrained to move in a two-dimensional curved space. The curvature is caused by random surface deformations that appear naturally during the growth of the material. Such a bump on the surface acts like a gravitational lens for surface electrons, resulting in trajectories that are analogous to geodesic motion. Considering that due to the special nature of topological insulators these surface electrons are protected from the ubiquitous impurity backscattering, this article likely reveals a previously unsuspected and important contribution to the resistivity on the surface of these materials. – Athanasios Chantis

Unconventional paring in inversion-symmetry lacking crystal

Electrons pair to carry supercurrent in a crystal. The paring symmetry can be s-wave, p-wave, d-wave and so on, depending on the underlying crystal structure. Those paring possibilities have definite spatial parities: s- and d-wave don't change under inversion while p changes sign and they don't mix in a centrosymmetric crystal. Moreover, they pair constrained by Pauli principle, which requires them to be a singlet for even-parity but triplet for odd-parity. However, for a non-centrosymmetric crystal, mixing is possible:

Unconventional pairs

Unconventional superconducting phase in the weakly correlated noncentrosymmetric Mo₃Al₂C compound: E. Bauer, G. Rogl, Xing-Qiu Chen, R. T. Khan, H. Michor, G. Hilscher, E. Royanian, K. Kumagai, D. Z. Li, Y. Y. Li, R. Podloucky, and P. Rogl ,Phys. Rev. B 82, 064511 (Published August 17, 2010)

Structure and physical properties of the noncentrosymmetric superconductor Mo₃Al₂C: A. B. Karki, Y. M. Xiong, I. Vekhter, D. Browne, P. W. Adams, D. P. Young, K. R. Thomas, Julia Y. Chan, H. Kim, and R. Prozorov: Phys. Rev. B 82, 064512 (Published August 17, 2010)

In superconductors, the appearance of dissipationless current is related to the formation of electron pairs with opposite spin and momentum. The symmetry of these pairs, which is constrained by the symmetries of the underlying crystal structure, defines important aspects of the superconducting state. So what happens to superconductivity when electron pairing occurs in a crystal structure that has no center of inversion?

This interesting question has been investigated in detail theoretically, and it was realized that in such cases the superconducting pairing is unconventional. In conventional (centrosymmetric) superconductors there can only be either spin-singlet or spin-triplet electron pairing, but in the absence of space-inversion symmetry the two can mix by the action of spin-orbit interaction (a relativistic effect), leading to unusual superconducting behavior.

This theoretical prediction has been tested experimentally in two independent articles that appear in Physical Review B. Ernst Bauer and collaborators from the Vienna University of Technology, Austria, with collaborators from China and Japan in one group, and Amar Karki and collaborators from Louisiana State University, US, with collaborators from Iowa State University, US, in the other, successfully grow and characterize Mo₃Al₂C. This material crystallizes in a noncentrosymmetric structure and undergoes a superconducting transition at T_c~9 K. Both groups observe signs of unconventional pairing, hinting at a strong connection between noncentrosymmetry and unconventional superconductivity. – Athanasios Chantis

2D on the planck scale ?

Carlip, a cosmologist at University of California, in his just submitted preprint argued that, the universe at the imaginably smallest scale is perhaps 2D, one being space while the other being time. He called this dimensional reduction. In his scenario, this reduction is random and non-systematic, and thus indicating Lorentz invariance violation: going in different direction encounters distinct physics. He called for further investigations. Here I give a roster of some key concepts:

(1)Definition of dimension by random walk: "In particular, the return probability K(x, x, s) is
K(x, x; s) ∼ (4πs)−dS/2." Here ds is just the dimension, and K(x,x,s) gives the return probability of a random walker in space s.

(2)Some claimed evidences:

• Causal Dynamical Triangulations;
• Renormalization Group Analysis;
• Loop quantum gravity;
• High temperature strings;
• Anisotropic scaling models

(3)Wheeler-DeWitt equation, which is the Schodinger equation for metric tensor.
(4)Strong coupling limit.

At much smaller scales, on the other hand, the proper description is far less obvious.
While clever experimentalists have managed to probe some features down to distances close to the Planck scale [2], for the most part we have neither direct observations nor a generally accepted theoretical framework for describing the very small-scale structure of spacetime. Indeed, it is not completely clear that “space” and “time” are even the appropriate categories for such a description. But while a complete quantum theory of gravity remains elusive, we do have fragments:
approximations, simple models, and pieces of what may eventually prove to be the correct theory. None of these fragments is reliable by itself, but when they agree with each other about some fundamental property of spacetime, we should consider the possibility that they are showing us something real. The thermodynamic properties of black holes, for example, appear so consistently that it is reasonable to suppose that they reflect an underlying statistical mechanics of quantum states. Over the past several years, evidence for another basic feature of small-scale spacetime has been accumulating: it is becoming increasingly plausible that spacetime near the Planck
scale is effectively two-dimensional. No single piece of evidence for this behavior is in itself very convincing, and most of the results are fairly new and tentative. But we now have hints from a number of independent calculations, based on different approaches to quantum gravity, that all point in the same direction. Here, I will summarize these clues, provide a further piece of evidence in the form of a strong-coupling approximation to the Wheeler- DeWitt equation, and discuss some possible implications.

double exchange relevant for High Tc superconductivity

Last year there published a paper [Hai-Yao Deng 2009 J. Phys.: Condens. Matter 21 075702] in which a model was proposed to address the issues regarding the coexistence of Zhang-Rice singlet formation and the spin glass at very low doping in cuprates. This model contains not only itinerant charges but also localized spins. There is strong on-site anti-ferromagnetic coupling between them. This coupling is held responsible for the formation of ZRS and the formation of spin glass, as a result of double exchange. Now there came very latest studies [Phys. Rev. B 82, 045125 (2010);Phys. Rev. Lett. 105, 107004 (2010)] that held similar ideas in solving puzzles residing in iron-based pnictides. This should not be regarded as a simple coincidence. It may strengthen the idea that, high Tc SC is intimately connected with magnetic fluctuations. More likely, this model may serve as a unification for High Tc superconductors of both iron-based and copper-based.

A story of a scientist

My first laser

By Physics Today on August 12, 2010 1:58 PM | 1 Comment | No TrackBacks

When Theodore Maiman introduced the ruby laser on 16 May 1960, with pulses of bright, coherent red light from his laboratory at Hughes Research, I was an 11-year-old "Sputnik" kid playing dangerously with homemade rockets and radio circuits.

Although I was too young to pay much notice then, I got hooked on lasers two years later when I read an article in Popular Science magazine titled "The Incredible Ruby Ray" (scroll to page 89). It thoroughly captivated me—I just had to make a laser for myself!

The trouble with such a venture for a 13-year-old boy was the required equipment; a cigarette-sized ruby crystal and a high-energy flashtube far exceeded my discretionary funds. Cash from delivering papers and mowing lawns could keep a junior scientist stocked with chemicals and radio parts, but the components for a pulsed ruby laser would require a major bequest from a rich relative. I didn't have one.

After I had read the article in Popular Science, I started reading any article I could find on lasers and spending afternoons and weekends in the library of Philadelphia's Franklin Institute. I needed to find someone who would lend me the required ruby crystal. By 1963 a small number of companies in the United States were making those precisely grown crystals, but the price for the required two-inch-long specimen was well over $1000.

I wrote letters to every such company that I could identify, explained my plans, and inquired whether I could borrow a ruby crystal. To my delight, a research team at RCA's engineering research facility in Camden, NJ, wrote back and invited me for a visit. I took that to mean that they wanted to check me out before offering to help.

I left the RCA laboratory with not one but two laser crystals, in addition to lots of advice on how to build my first laser. The engineers I met during my first visit to RCA stayed in touch with me during what became my four-year venture as my lasers became increasingly sophisticated (and better working) and my ability to ask better questions matured.

My third laser, completed in 1965 (shown in the photo), was a reasonable scientific tool for the time. Making good use of a scientific tool for discovery is an important component of a scientist's education. While pondering what to do with my laser, another venture in letter writing served me well. I wrote to Hermann Muller, a professor emeritus at Indiana University who had won the 1946 Nobel Prize for Physiology or Medicine by showing that exposure to sufficient quantities of x rays causes damage to biological cells and eventually leads to mutations.

I asked Muller to speculate on whether the unique characteristics of laser light—spectral purity and ability to tightly focus—might have novel effects on biological systems. To this day I marvel at the three-page response he sent back to me, a 15-year-old high-school freshman at the time. Muller's letter included ruminations on my query, suggestions for my experiments, background tutorials, and a long list of suggested reading.

His recommendations led me to do a series of experiments with my model 3 laser that involved controlled exposures of frog eggs harvested from the backyard pond and onion roots dug up from the garden. My experiments won me some minor awards in the regional science fair in Philadelphia, but, more importantly, the experience taught me how to do experiments.

Ten years later with a freshly minted PhD in physics, and ever since, I have tried to be generous with my time whenever a young student sends me an inquiry or asks me for advice or for a loan of scientific gadgetry. I remember how the RCA engineers and Professor Muller took interest in me and how they influenced my career in a positive way.

Within every scientist is the drive to understand how things work and to discover new ways of doing things. Yet the fervor for discovery is cultivated by strong mentors who encourage, steer, and challenge the budding scientist until—and often long after—he or she becomes a professional scientist. My own fascination with science was fueled by the invention of the laser and guided by scientists who took a personal interest in my curiosity—mentors who had a tremendous impact on my life and career.

H. Frederick Dylla

More on the story of SC

Just came back from a short vacation. There is more on how the superconductivity was made by Onnes. An interesting story to read here !

Do you think so ?

It May Be Interesting, But Is It IMPORTANT?

I think that the fuzzy boundary between simply being a "student" of physics and a professional, practicing physicist is the ability to answer that question.

Again, as I've mentioned a few times in my journal, there are some skills that are not part of your physics curriculum. One such skill is the ability to determine if something is not just interesting, but also important. Strange as it may seem, those two are not always mutually inclusive. As a student, one doesn't have to figure out if something is "important" because hopefully, the wise guidance of the academic advisor would steer one onto the right area. However, when that line between a "student" and a "practicing physicist" is crossed, that question now becomes relevant.

What is considered to be interesting is mainly an individual preference. This is what you yourself want to do and what to spend time doing, without the need of any external impetus. However, what is important is usually determined by things outside of you. This may be the state of the field at the time, the research funding goals, the reason why you were hired, etc.

Now, in many instances, what is interesting and what is important overlap. However, any physicist can tell you this that this doesn't occur all the time. Personally, I've encountered a few situations where I find something quite interesting to study, but simply can't quite justify why it would be "important" to spend time and effort to study it. The real world in which physics is done involves money, time, effort, resources, etc. While a student is usually immune to such constraints, a practicing physicist isn't. There are many external considerations beyond just the physics to determine what gets done.

Of course, there are times when what was merely interesting becomes important, and what was important becomes merely an interesting curiosity. Unless we are also psychic (assuming such things are real), we can't predict such changes. Thus, it might sometime pay to keep some things in the back burner just in case while one continues working on those "important" stuff.

Zz.

What referees expect

What they expect from a manuscript is something they have never heard of, they have never seen anything resembling or analogous to, something that is completely novel, something that is counter-intuitive yet convincing.

So, a piece of work that is publishable should not only be fabulous in the eyes of the author himself, but also be fabulous in the eyes of his vast circle of fellow workers. His work has to be interesting and thus new to himself and also to his peers.

direct observation of ZRS

The existence and stability of Zhang-Rice singlet was predicted theoretically many years ago, as a key fact to modeling High Tc superconducting cuprates. Two years ago, an experiment directly observed them. The following is a description of this work:

Direct Observation of the Zhang-Rice Singlets in High-Temperature Superconductors

last modified 20-02-2007 09:38

More than a decade has passed since the discovery of high temperature (HTc) superconductors. However, despite an intense research effort the mechanism responsible for these phenomena is still not fully understood. In order to test the basic assumptions of HTc superconductivity theories, it is important to have experimental evidence for the electronic structure of these materials. In many mainstream theories, like the single band Hubbard model and the t ­ J model, the relevant states in the (CuO₂)^2­ planes are of local singlet spin character (two holes with antiparallel spins, S = 0). In the single-band t ­ J model these states are often referred to as Zhang-Rice singlets [1]. Singlet states are contrary to what would normally be expected from Hund's first rule (i.e. triplet states, two holes with parallel spins, S = 1). Calculations have also shown that the photoemission spectrum can be directly related to the ground state electronic structure of the doped material. Consequently, one would like to measure the spin-resolved single-particle excitation spectrum to derive the energies of the different spin-dependent electronic states close to the Fermi level. The observation of the singlet states would provide strong support for the existence of the Zhang-Rice singlets in HTc cuprates [1].

Recently the feasibility of this type of study was demonstrated for CuO [2]. The experiment is based on spin-polarised resonant photoemission measurements made using circularly polarised X-rays. In these new experiments we have studied optimally doped (T_c = 91 K) Bi₂Sr₂CaCu₂O₈₊ samples. The experiments were carried out on the helical undulator based beamline ID12B and the spectra were recorded using an electron analyser coupled to a spin polarimeter. The resonant photoemission measurements were achieved by tuning the photon energy to the peak of the Cu 2p_3/2 (L₃) photoabsorption white line (h = 931.5 eV).

In Figure 53a we show the spin integrated resonant photoemission spectra (full line) and in Figure 53b we show the spin polarisation given by the spin difference (using both helicities) normalised to the spin integrated spectrum. The spectrum results principally from Cu 3d⁸ final states and the peak at ~12 eV binding energy can be assigned to an atomic like ¹G state. This is completely analogous to the previous work on CuO [2]. The spin polarisation of this peak is ~80%. This value is consistent with an analysis of the selection rules which give for a 3d⁹ ion, neglecting the small 3d spin-orbit interaction, 5/6 (83.3%) for pure singlet states and ­1/3* 5/6 (-27.8%) for triplet states. The strong dip in the polarisation at ~9 eV binding energy indicates a significant triplet contribution to the spectra at this energy. Assuming these model values for the polarisation of singlet and triplet states, we can separate the spectra into the two contributions. These are shown by the symbols in Figure 53a.

We are principally interested in the electronic states close to the Fermi level. Although the intensity is extremely low, it is clear that the spin polarisation increases dramatically around the Fermi level (see Figure 53b). This is the first evidence that the states close to the Fermi level are mostly of singlet character. In Figure 53c we show the region close to the Fermi level taken with good statistical quality. The spectrum is separated into its singlet and triplet components. It is quite clear that the intensity closest to the Fermi level and over more than 1 eV is dominated by singlet states. Consequently, we can conclude that for the Bi₂Sr₂CaCu₂O₈₊ superconductor that the first ionisation state is of nearly pure singlet character. This provides compelling evidence for the existence and stability of the Zhang-Rice singlets in HTc cuprates [1].

References
[1] F.C. Zhang, T.M. Rice, Phys. Rev., B 37, 3759 (1988).
[2] L.H. Tjeng, B. Sinkovic, N.B. Brookes, J.B. Goedkoop, R. Hesper, E. Pellegrin, F.M.F. de Groot, S. Altieri, S.L. Hulbert, E. Shekel, G.A. Sawatzky, Phys. Rev. Lett., 78, 1126 (1997).

Authors
N.B. Brookes (a), G. Ghiringhelli (a), O. Tjernberg (a), L.H. Tjeng (b), T. Mizokawa (b) , T.W. Li (c), A.A. Menovsky (c).

(a) ESRF
(b) Solid State Physics Laboratory, Materials Science Centre, University of Groningen, (The Netherlands)
(c) Van der Waals-Zeeman Laboratory, University of Amsterdam (The Netherlands)

The Nobel lectures delivered last year

One may find these lectures by these links:
[1]http://rmp.aps.org/pdf/RMP/v82/i3/p2299_1
[2]http://rmp.aps.org/pdf/RMP/v82/i3/p2305_1
[3]http://rmp.aps.org/pdf/RMP/v82/i3/p2307_1

The first one, by Charles' wife, accounted for the story how Charles made his discovery concerning optical communications, which now have benefited the whole human race. His wife did this for him, since he is sick. It may be interesting to read how his wife thought about his science.

The second and the third are by the discoverers themselves, on the invention of CCD, namely, the charge coupled device. So, last year's physics prize went to technological innovations.

Ettore Majorana: a myth

I did not hear of his mysterious fate before, although I know a fermion bearing his name: majorana fermion, which now becomes a topical field in physics. He published only a few papers, but his genius cant be hidden, as Fermi put, "There are many categories of scientists, people of second and third rank, who do their best, but do not go very far. There are also people of first class, who make great discoveries, which are of capital importance for the development of science. But then there are the geniuses, like Galileo and Newton. Well, Ettore was one of these. Majorana had greater gifts than anyone else in the world; unfortunately he lacked one quality which other men generally have: plain common sense." [http://en.wikipedia.org/wiki/Ettore_Majorana]

Maybe in the rise of the fame of his fermion, there came a article in Review Of Modern Physics describing his life and his work. But this article mostly covers his contribution to auto-ionization. As a man immersed in physics, I cant help falling sad for his life. Such compassion is really very strong between true fellow workers.

Despite various investigations into his disappearance, what had occurred to him is still dubious. There are several guesses. His friends say he might commit suicide. Some hypothesized he had escaped to Argentina. Some say he had fleeted to a monastary. Even, some say he had become a beggar as an alighting. In those dark ages, anything might happen !