Monday, August 31, 2009

Saturday, August 29, 2009

Le Boudoir et sa Philosophie

I'm in Paris today: a shop in 3e. Click on picture for larger image.


Wednesday, August 26, 2009

Self Enforcing Protocols

Self Enforcing Protocols at Schneier on Security.
Here’s a self-enforcing protocol for determining property tax: the homeowner decides the value of the property and calculates the resultant tax, and the government can either accept the tax or buy the home for that price. Sounds unrealistic, but the Greek government implemented exactly that system for the taxation of antiquities. It was the easiest way to motivate people to accurately report the value of antiquities.

String Theory: 25 Years after the Revolution

Here's a post from Peter Woit's Not Even Wrong Blog 25 Years On ... summarizing the disappointing state of string theory research.

Saturday, August 15, 2009

Krakow Jewish Quarter: Words on the Street

Click on Photos for Larger Image







Weird Flash Effect

I was taking a tour of a salt mine near Krakow Poland. I was using a Nikon D200 camera and a Nikon SB800 flash triggered remotely. The first shot came out rather strangely and at first I didn't know why. I happened to take a second shot (8 seconds later) which came out more or less normally.


A "normal" photo of a tableaux illustrating work at the salt mine.
Apparently the explanation is this: I might have accidently twisted the zoom ring while I was taking the first photo.

Thursday, August 13, 2009

St. Mary's Basilica, Krakow, Poland



St. Mary's Basilica
, Krakow, Poland is gorgeous and naturally by-and-large rather solemn.
However this particular bird figure seemed to me to be just a little bit funky and out of place. Is it really supposed to be the Polish Eagle?

Krakow Sundial


This is a nodus-based sundial on the wall of St. Mary's Basilica in Krakow Poland. It was taken on August 12th - this type of sundial is supposed to indicate the date as well as the time. The astrological signs are depicted on the sundial, the shadow seems to fall within Leo (July 23 to August 23) but I'm not sure which part of the shadow is supposed to indicate the exact date, etc. Click on the picture to see a larger version.

Monday, August 10, 2009

The Meeting of Minds

Click on a picture for a slightly larger and (hopefully) more humorous view.









While I was shooting these I overheard a tourist ask her boyfriend "Why does he keep taking the same picture over and over again?"

Lidia in Warsaw

Lidia Berger and some of her wonderful friends have been introducing me to Warsaw the past few days. Click on a picture for a slightly larger view.





Wednesday, August 05, 2009

Quantum Measurement Processes

The Measurement Process in Local Quantum Theory and the EPR Paradox
We describe in a qualitative way a possible picture of the Measurement Process in Quantum Mechanics, which takes into account: 1. the finite and non zero time duration T of the interaction between the observed system and the *microscopic part* of the measurement apparatus; 2. the finite space size R of that apparatus; 3. the fact that the *macroscopic part* of the measurement apparatus, having the role of amplifying the effect of that interaction to a macroscopic scale, is composed by a very large but finite number N of particles.
The conventional picture of the measurement, as an instantaneous action turning a pure state into a mixture, arises only in the limit where N tends to infinity, T tends to zero, R tends to infinity.
The limit where N tends to infinity has been often discussed as the origin of decoherence. We argue here that, as a consequence of the Principle of Locality, before those three limits are taken, no long range entanglement between the values of observables which are spacelike separated far away can be detected (although entangled states for such observables are well known to exist in local theories, simple examples are given in an Appendix). In order to detect correlations, one of the observers has to wait until he enters the future causal shadow of the region employed by the apparatus of the other. Accordingly, in this picture of the measurement process there would be no Einstein Podolski Rosen Paradox. (Similar views had been proposed already [6], [22]). A careful comparison with the growing experimental results of the recent decades might settle the question

The EPR Paradox is one of the most spectacular and disturbing consequences of Quantum theory and Special Relativity. But maybe if we really pay close attention to the microscopic details of the quantum measurement process, the paradox will disappear. This paper doesn't completely resolve these issues, but it does point out some of the idealizations of standard quantum theory that may be contributing to the EPR paradox.

Quantum Gravity

Quantum Gravity: Motivations and Alternatives
The mutual conceptual incompatibility between GR and QM/QFT is generally seen as the most essential motivation for the development of a theory of Quantum Gravity (QG). It leads to the insight that, if gravity is a fundamental interaction and QM is universally valid, the gravitational field will have to be quantized, not at least because of the inconsistency of semi-classical theories of gravity. If this means to quantize GR, its identification of the gravitational field with the spacetime metric has to be taken into account. And the resulting quantum theory has to be background-independent. This can not be achieved by means of quantum field theoretical procedures. More sophisticated strategies have to be applied. One of the basic requirements for such a quantization strategy is that the resulting quantum theory has GR as a classical limit. - However, should gravity not be a fundamental, but an residual, emergent interaction, it could very well be an intrinsically classical phenomenon. Should QM be nonetheless universally valid, we had to assume a quantum substrate from which gravity would result as an emergent classical phenomenon. And there would be no conflict with the arguments against semi-classical theories, because there would be no gravity at all on the substrate level. The gravitational field would not have any quantum properties, and a quantization of GR would not lead to any fundamental theory. The objective of a theory of 'QG' would instead be the identification of the quantum substrate from which gravity results. - The paper tries to give an overview over the main options for theory construction in the field of QG. Because of the still unclear status of gravity and spacetime, it pleads for the necessity of a plurality of conceptually different approaches to QG.

Tuesday, August 04, 2009

Horse Dung and Telescopes

I'm reading The Age of Wonder: How the Romantic Generation Discovered the Beauty and Terror of Science by Richard Holmes. It's about science and culture in the late eighteenth and early nineteen century - mostly British. I just finished the section about William Herschel, the German/English discoverer of the planet Uranus. He was an innovative telescope maker and he employed horse dung to make the moulds which he used to cast the metal mirrors for his telescopes. The book says that horse dung was used for this purpose until the early twentieth century. Herschel was also a professional musician and that's how he made his living until he became famous for discovering the planet.

Distribution of Stars at the Center of the Galaxy

High angular resolution integral-field spectroscopy of the Galaxy's nuclear cluster: a missing stellar cusp?
The distribution of stars near the center of the galaxy isn't what is expected from a model of a supermassive black hole.

Ward Cunningham Interview

Here's a really nice interview with computer programmer Ward Cunningham the originator of the term "Wiki" as in Wikipedia.

Monday, August 03, 2009

The baryonic Tully-Fisher relation

The baryonic Tully-Fisher relation and its implication for dark matter halos
The baryonic Tully-Fisher relation (BTF) is a fundamental relation between baryonic mass and maximum rotation velocity. It can be used to estimate distances, as well as to constrain the properties of dark matter and its relation with the visible matter. In this paper, we explore if extremely low-mass dwarf galaxies follow the same BTF relation as high-mass galaxies. We quantify the scatter in the BTF relation and use this to constrain the allowed elongations of dark matter halo potentials. We obtained HI synthesis data of 11 dwarf galaxies and derive several independent estimates for the maximum rotation velocity. Constructing a BTF relation using data from the literature for the high-mass end, and galaxies with detected rotation from our sample for the low-mass end results in a BTF with a scatter of 0.33 mag. This scatter constrains the ellipticities of the potentials in the plane of the disks of the galaxies to an upper limit of 0-0.06 indicating that dwarf galaxies are at most only mildly tri-axial. Our results indicate that the BTF relation is a fundamental relation which all rotationally dominated galaxies seem to follow.

Sunday, August 02, 2009

Honesty - Will or Grace?

Patterns of neural activity associated with honest and dishonest moral decisions
What makes people behave honestly when confronted with opportunities for dishonest gain? Research on the interplay between controlled and automatic processes in decision making suggests 2 hypotheses: According to the “Will” hypothesis, honesty results from the active resistance of temptation, comparable to the controlled cognitive processes that enable the delay of reward. According to the “Grace” hypothesis, honesty results from the absence of temptation, consistent with research emphasizing the determination of behavior by the presence or absence of automatic processes. To test these hypotheses, we examined neural activity in individuals confronted with opportunities for dishonest gain. Subjects undergoing functional magnetic resonance imaging (fMRI) gained money by accurately predicting the outcomes of computerized coin-flips. In some trials, subjects recorded their predictions in advance. In other trials, subjects were rewarded based on self-reported accuracy, allowing them to gain money dishonestly by lying about the accuracy of their predictions. Many subjects behaved dishonestly, as indicated by improbable levels of “accuracy.” Our findings support the Grace hypothesis. Individuals who behaved honestly exhibited no additional control-related activity (or other kind of activity) when choosing to behave honestly, as compared with a control condition in which there was no opportunity for dishonest gain. In contrast, individuals who behaved dishonestly exhibited increased activity in control-related regions of prefrontal cortex, both when choosing to behave dishonestly and on occasions when they refrained from dishonesty. Levels of activity in these regions correlated with the frequency of dishonesty in individuals.

Some people were always honest and they showed no special brain activity, other people were sometimes dishonest and they did display increased brain activity. This doesn't really seem surprising. Which isn't to say that this experiment is trivial, far from it - it's fascinating. It would be interesting to see if there are unusual people who can perform dishonestly without registering any special brain activity. Presumably these people would be naturally good spys, poker players, etc.
See the web page of the Moral Cognition Lab at Harvard.
There's a discussion of the paper at this blog post: Angels and Demons.

Statistics - Levy Laws and 1/f noise

A unified and universal explanation for Lévy laws and 1/f noises
Lévy laws and 1/f noises are shown to emerge uniquely and universally from a general model of systems which superimpose the transmissions of many independent stochastic signals. The signals are considered to follow, statistically, a common—yet arbitrary—generic signal pattern which may be either stationary or dissipative. Each signal is considered to have its own random transmission amplitude and frequency. We characterize the amplitude-frequency randomizations which render the system output's stationary law and power-spectrum universal—i.e., independent of the underlying generic signal pattern. The classes of universal stationary laws and power spectra are shown to coincide, respectively, with the classes of Lévy laws and 1/f noises—thus providing a unified and universal explanation for the ubiquity of these classes of “anomalous statistics” in various fields of science and engineering.

Cosmic Impact at the Younger Dryas Boundary

Shock-synthesized hexagonal diamonds in Younger Dryas boundary sediments
The long-standing controversy regarding the late Pleistocene megafaunal extinctions in North America has been invigorated by a hypothesis implicating a cosmic impact at the Ållerød-Younger Dryas boundary or YDB (≈12,900 ± 100 cal BP or 10,900 ± 100 14C years). Abrupt ecosystem disruption caused by this event may have triggered the megafaunal extinctions, along with reductions in other animal populations, including humans. The hypothesis remains controversial due to absence of shocked minerals, tektites, and impact craters. Here, we report the presence of shock-synthesized hexagonal nanodiamonds (lonsdaleite) in YDB sediments dating to ≈12,950 ± 50 cal BP at Arlington Canyon, Santa Rosa Island, California. Lonsdaleite is known on Earth only in meteorites and impact craters, and its presence strongly supports a cosmic impact event ...

Helitrons

Structure-based discovery and description of plant and animal Helitrons
Helitrons are recently discovered eukaryotic transposons that are predicted to amplify by a rolling-circle mechanism. They are present in most plant and animal species investigated, but were previously overlooked partly because they lack terminal repeats and do not create target site duplications.

Plant genomes: Massive changes of the maize genome are caused by Helitrons
Helitrons are eukaryotic transposable elements recognized only recently by computer analysis of repetitive DNA sequences of Arabidopsis, rice and Caenorhabditis elegans (Kapitonov and Jurka, 2001). Helitrons are quite large (>10 kbp) but unlike virtually all other classes of transposable elements, Helitrons lack terminal repeats and do not duplicate host sequences during the insertion process. They insert within the host dinucleotide, AT.

Living Fossils?

Nine exceptional radiations plus high turnover explain species diversity in jawed vertebrates
The other main deviations from our constant-rate model are the prototypical ‘‘living fossil’’ lineages, old lineages with few extant species (17, 18). In our study, 3 living fossil lineages are notable for both their low rate of speciation and extremely low rates of extinction. These groups stand out in stark contrast to the rest of the vertebrate tree, which is characterized by high rates of both speciation and extinction (Fig. 2). This highlights one of the key challenges presented by living fossils to molecular based studies of extant diversity: although young species-rich groups can be explained by a transient increase in net diversification rates for a relatively short period, older species-poor groups require negligible rates of both speciation and extinction over tremendously long periods of time to explain their persistence. We note that all 3 slowly evolving lineages were historically more diverse than they are today.

Why are these groups called "living fossils"? They diverged a long time ago and they have few surviving species. Why does that lead anyone to believe that the modern organisms are similiar to ancient ones?

Sirtuins - enzymes which regulate lifespan?

Recent progress in the biology and physiology of sirtuins
The sirtuins are a highly conserved family of NAD+-dependent enzymes that regulate lifespan in lower organisms. Recently, the mammalian sirtuins have been connected to an ever widening circle of activities that encompass cellular stress resistance, genomic stability, tumorigenesis and energy metabolism. Here we review the recent progress in sirtuin biology, the role these proteins have in various age-related diseases and the tantalizing notion that the activity of this family of enzymes somehow regulates how long we live.

Electricity from Kites

Wind power: High hopes in Nature.
A vast supply of energy is racing around the planet far above the surface. Erik Vance meets the engineers trying to bring the power of high-altitude wind down to earth.

Helical Dirac fermions

A tunable topological insulator in the spin helical Dirac transport regime
Helical Dirac fermions—charge carriers that behave as massless relativistic particles with an intrinsic angular momentum (spin) locked to its translational momentum—are proposed to be the key to realizing fundamentally new phenomena in condensed matter physics

First observation of spin-helical Dirac fermions and topological phases in undoped and doped Bi2Te3 demonstrated by spin-ARPES spectroscopy
Electron systems that possess light-like dispersion relations or the conical Dirac spectrum, such as graphene and bismuth, have recently been shown to harbor unusual collective states in high magnetic fields. Such states are possible because their light-like electrons come in spin pairs that are chiral,which means that their direction of propagation is tied to a quantity called pseudospin that describes their location in the crystal lattice. An emerging direction in quantum materials research is the manipulation of atomic spin-orbit coupling to simulate the effect of a spin dependent magnetic field,in attempt to realize novel spin phases of matter. This effect has been proposed to realize systems consisting of unpaired Dirac cones that are helical, meaning their direction of propagation is tied to the electron spin itself, which are forbidden to exist in graphene or bismuth.

X Rays from Nanotubes

Nanotubes sharpen X-ray vision
Mini X-ray tubes could revolutionize radiotherapy — and airport baggage scanners.

Is the Toucan's Bill primarily a Heat Exchanger?

Heat Exchange from the Toucan Bill Reveals a Controllable Vascular Thermal Radiator
The toco toucan (Ramphastos toco), the largest member of the toucan family, possesses the largest beak relative to body size of all birds. This exaggerated feature has received various interpretations, from serving as a sexual ornament to being a refined adaptation for feeding. However, it is also a significant surface area for heat exchange. Here we show the remarkable capacity of the toco toucan to regulate heat distribution by modifying blood flow, using the bill as a transient thermal radiator. Our results indicate that the toucan's bill is, relative to its size, one of the largest thermal windows in the animal kingdom, rivaling elephants’ ears in its ability to radiate body heat.

Polarized Signalling in Animals

Many animals create striking visual effects not with pigments but with intricately structured materials. See how some scarab beetles produce their colorful appearence in Evolutionary Photonics with a Twist.

Pathological Science

Pathological Science is when investigators trick themselves into believing false results. There was a classic talk PATHOLOGICAL SCIENCE given by Irving Langmuir in 1953.

Did the Immune System Originate with a Virus?

The immune system has the incredible ability to create a vast number of very specific antibodies. In Immune System: Success Owed to a Virus? the author conjectures that the recombination process which generates so much variety may have originated with a virus.

Rare Venomous Mammal

The Solenodon is a very rare and strange little mammal, it is the only mammal that injects venom through its teeth like snakes. See Saving a Venomous Ghost in Science. The are kind of cute too, see Venomous mammal caught on camera.

Saturday, August 01, 2009

Phonon Lasers

Phonon laser action in a tunable, two-level photonic molecule
The phonon analog of an optical laser has long been a subject of interest. We demonstrate a compound microcavity system, coupled to a radio-frequency mechanical mode, that operates in close analogy to a two-level laser system. An inversion produces gain, causing phonon laser action above a pump power threshold of around 50 $\mu$W. The device features a continuously tunable, gain spectrum to selectively amplify mechanical modes from radio frequency to microwave rates. Viewed as a Brillouin process, the system accesses a regime in which the phonon plays what has traditionally been the role of the Stokes wave. For this reason, it should also be possible to controllably switch between phonon and photon laser regimes. Cooling of the mechanical mode is also possible.

Nuclear Astrophysics

Massive stars as thermonuclear reactors and their explosions following core collapse
Nuclear reactions transform atomic nuclei inside stars. This is the process of stellar nucleosynthesis. The basic concepts of determining nuclear reaction rates inside stars are reviewed. How stars manage to burn their fuel so slowly most of the time are also considered. Stellar thermonuclear reactions involving protons in hydrostatic burning are discussed first. Then I discuss triple alpha reactions in the helium burning stage. Carbon and oxygen survive in red giant stars because of the nuclear structure of oxygen and neon. Further nuclear burning of carbon, neon, oxygen and silicon in quiescent conditions are discussed next. In the subsequent core-collapse phase, neutronization due to electron capture from the top of the Fermi sea in a degenerate core takes place. The expected signal of neutrinos from a nearby supernova is calculated. The supernova often explodes inside a dense circumstellar medium, which is established due to the progenitor star losing its outermost envelope in a stellar wind or mass transfer in a binary system. The nature of the circumstellar medium and the ejecta of the supernova and their dynamics are revealed by observations in the optical, IR, radio, and X-ray bands, and I discuss some of these observations and their interpretations.

Musical Numerology

Why the Kirnberger Kernel Is So Small discusses some interesting numerical coincidences in the most commonly used musical scale.

Open Problems in HadronPhysics

Confinement & Chiral Symmetry Breaking: The fundamental problems of hadron physics
Some of the difficulties arising when one tries to understand confinement as well as dynamical and anomalous chiral symmetry breaking are reviewed. Criteria to be fulfilled by a successful and complete picture of these phenomena are presented, and a few of the suggested explanations are listed.