Tuesday, December 29, 2009

Change Blindness

Video of a dumbfounding Harvard experiment on "change blindness".


Here's another video on Youtube along the same lines.

Saturday, December 26, 2009

Parity Invariance

The Mystery of Parity
"And should I not take pity on Nineveh, that great city, with more than a hundred and twenty thousand inhabitants who do not know their right hand from their left, and many beasts besides?" [Jonah 4:11]
In this article we shall be concerned with microscopic parity invariance and a mystery which it presents. This consists of a marriage of internal and space-time symmetries, forbidden when the space-time symmetry consists of the whole Poincare group but permitted in this case because of the discrete nature of the parity transformation. We will argue that this marriage could point to regularities underlying the nature of quarks and leptons, and to extensions of particle interactions beyond those known today.

time reversal invariance violation

Large scale physical effects of T violation in mesons
An increasing number of experiments at the Belle, BNL, CERN and SLAC accelerators are confirming the violation of time reversal invariance (T). The violation signifies a fundamental asymmetry between the past and future and calls for a major shift in the way we think about time. Here we show that processes which violate T symmetry induce destructive interference between different paths that the universe can take through time. The interference eliminates all paths except for two that represent continuously forwards and continuously backwards time evolution. Evidence from the accelerator experiments indicates which path the universe is effectively following. This work resolves the long-standing problem of modeling the dynamics of T violation processes. It shows that T violation has previously unknown, large-scale physical effects and that these effects underlie the origin of the unidirectionality of time. It also provides a view of the quantum nature of time itself.

Missing Baryons

The Baryon Content of Cosmic Structures
We make an inventory of the baryonic and gravitating mass in structures ranging from the smallest galaxies to rich clusters of galaxies. We find that the fraction of baryons converted to stars reaches a maximum between M500 = 1E12 and 1E13 Msun, suggesting that star formation is most efficient in bright galaxies in groups. The fraction of baryons detected in all forms deviates monotonically from the cosmic baryon fraction as a function of mass. On the largest scales of clusters, most of the expected baryons are detected, while in the smallest dwarf galaxies, fewer than 1% are detected. Where these missing baryons reside is unclear.

Flavor Physics

Brief Introduction to Flavor Physics
We consider the standard model (SM) quark flavor sector. We study its structure in a spurionic, symmetry oriented approach. The SM picture of flavor and CP violation is now experimentally verified, hence strong bounds on beyond the SM flavor structure follow. We show how to parametrically derive such bounds, in a model independent manner, via minimal flavor violation power counting. This min-review summarizes lectures given at the ISSCSMB '08 international school. It aims to give basic tools to understand how flavor and CP violation occur in the SM and its extensions. It should be particularly useful for non-expert students who have mastered other aspects of the SM dynamics.

Note: A spurion is the name given to a "particle" inserted mathematically into an isospin-violating decay in order to analyze it as though it conserved isospin. --- Wikipedia

Friday, December 25, 2009

Proton Spin

Understanding the proton's spin structure
We discuss the tremendous progress that has been towards an understanding of how the spin of the proton is distributed on its quark and gluon constituents. This is a problem that began in earnest twenty years ago with the discovery of the proton ``spin crisis'' by the European Muon Collaboration. The discoveries prompted by that original work have given us unprecedented insight into the amount of spin carried by polarized gluons and the orbital angular momentum of the quarks.

Thursday, December 24, 2009

Quantum Leaps

I just read the book Quantum Leaps by Jeremy Bernstein. He is an entertaining writer. The book discusses the history of the "Quantum Measurement" problem and also his expereiences as a physics student and journalist - he met many of the key historical figures over the years.
However, he did not actually meet the personalities in this ancedote (my paraphrase follows).
Beria was put in charge of the Soviet nuclear program. He complained to Stalin that the scientists were using quantum techniques, which were held to be in conflict with Marxism. Stalin allegedly told Beria "Leave my physicists alone. We can always shoot them later."

Wednesday, December 23, 2009

Modified Gravity

New Physics at Low Accelerations (MOND): an Alternative to Dark Matter
I describe the MOND paradigm, which posits a departure from standard physics below a certain acceleration scale. This acceleration as deduced from the dynamics in galaxies is found mysteriously to agree with the cosmic acceleration scales defined by the present day expansion rate and by the density of `dark energy'. I put special emphasis on phenomenology and on critical comparison with the competing paradigm based on classical dynamics plus cold dark matter. I also describe briefly nonrelativistic and relativistic MOND theories

Quantum Measurements and General Relativity

There are sticky issues when trying to understand how quantum measurement and general relativity might work together. Relativistic Model for Gravity-Induced Quantum State Reduction
A Lorentz invariant model for gravity-induced quantum state reduction is presented, which is mainly developed from the physical argument that the time translation operator in a superposition of macroscopic states is ill-defined. The model leads to a new approach how to overcome the basic problem of relativistic reduction models, the conflict between relativistic covariance and the assumption that state reduction leads to an abrupt change of the wave-function on a space-like hyperplane. Reductions are understood in the model as events on whole space-time regions instead on hyperplanes only. This view enforces a radical change for the formulation of the system's dynamics. A stochastic time flow running quasi orthogonal to the deterministic time evolution inside the four-dimensional space-time is proposed. It is shown that it is possible to formulate on the basis of this new view a meaningful physical model. The model is also checked for possible higher order effects, which provide new starting points for experimental research.

Tuesday, December 22, 2009

Dive Pictures




I went scuba diving in Grand Cayman last week - there were lots of turtles.

Reading the Mind in the Eyes

Reading the mind in the eyes is a test to determine how well can you tell what a person is thinking or feeling from a photograph of their eyes. I scored 28 out of 36. The typical range is 22-30 with over 30 indicating that you are exceptionally good at reading people and under 22 indicating that isn't one of your strengths. I would have guessed that I was about average at reading people's expressions, which this test confirms.
I took the test again on another web site, with a different format (you got immediate feedback after each question instead of at the end). This time I improved to 32/36 which isn't too surprising since they appeared to be the same pictures.

Thursday, October 29, 2009

Baryon Acoustic Oscillations

Baryon Acoustic Oscillations
Baryon Acoustic Oscillations(BAO) are frozen relics left over from the pre-decoupling universe. They are the standard rulers of choice for 21st century cosmology, providing distance estimates that are, for the first time, firmly rooted in well-understood, linear physics. This review synthesises current understanding regarding all aspects of BAO cosmology, from the theoretical and statistical to the observational, and includes a map of the future landscape of BAO surveys, both spectroscopic and photometric.

Monday, October 26, 2009

Monty Hall and John Von Neumann walk into a bar ...

I recently read The Monty Hall Problem: The Remarkable Story of Math's Most Contentious Brain Teaser .
Here's my version of the Monty Hall Problem.
The Basic Situation is as follows. There are two individuals: Monty Hall and Alice. There is a car; there are three closed curtains; and the car is behind one of the curtains, which hides it completely. There is nothing behind the other two curtains. The action proceeds as follows:
1. Monty hides the car behind one of the curtains (H); Alice has no idea which one.
2. Alice chooses a curtain (C), but it is left closed. Alice doesn't know yet whether she chose the car or not.
3. Monty opens one of the curtains (S) showing Alice what's behind it.
3a. Monty is not permitted to open curtain Alice's curtain C; S cannot equal C.
4. Alice finally chooses another curtain (F) which can be different than C or the same. Alice gets what's behind the curtain she finally chose. If F=H, Alice wins the car, otherwise Alice gets nothing.

We can nail this down so that it is an exercise in pure logic and probability for Alice by further specifying what Monty does at steps 1 and 3. Here are the Additional Stipulations.
1a. Monty chooses where to hide the car (H) by randomly picking one of the three curtains: each of the three curtains is equally likely.
3b. Monty will only show Alice an empty curtain in step 3. Monty never opens the curtain with the car. S cannot equal H.

Given these Additional Stipulations. the consequences of the Alice's choice in step 4 are completely unambiguous - however the results surprise many people. Alice's two main strategies are Stay (F=C) and Switch (F≠C≠S) Many people guess that Stay and Switch are equivalent and that Alice wins 1/2 the time either way. Surprisingly Stay only wins 1/3 of the time while Switch wins 2/3's of the time.

Suppose Alice elects to follow the following strategy: always choose curtain #1 in step 2 and always Stay with curtain #1 in step 4.
In step 1. Monty hides the car behind curtain #1 1/3 of the time.
In step 2. Alice always chooses curtain #1.
In step 3. Monty will open either curtain #2 or curtain #3. Note that this does not change the actual location of the car, it's still behind curtain #1.
In step 4. Alice will always choose curtain #1 again. Alice wins the car.

In step 1. Monty hides the car behind curtain #2 or curtain #3 2/3's of the time.
In step 2. Alice always chooses curtain #1, which is empty.
In step 3. Monty will open either curtain #2 or curtain #3. Note that this does not change the location of the car, curtain #1 is still empty.
In step 4. Alice will always choose curtain #1 again, which is empty. Alice gets nothing.

So we see that by following the strategy of always chosing curtain #1 both times, Alice only wins the car 1/3 of the time.

Suppose on the other hand Alice uses another strategy: in step 2. she always chooses curtain #1; in step 4. shes always Switches to the only other curtain which is still closed.

In step 1. Monty hides the car behind curtain #1 1/3 of the time.
In step 2. Alice always chooses curtain #1.
In step 3. Monty will always open curtain #2 or curtain #3. Note that this does not change the actual location of the car, it's still behind curtain #1.
In step 4. because Alice always switches she will choose either curtain #2 or curtain #3. But the car is still behind curtain #1 and Alice gets nothing.

In step 1. Monty hides the car behind curtain #2 1/3 of the time.
In step 2. Alice always chooses curtain #1, which is empty.
In step 3. Monty must open curtain #3 - because it is the only door which is empty and is not Alice's. That of course does not change the location of the car - which is still behind curtain #2.
In step 4. Alice always switches to curtain #2 - because it is still closed. Alice wins.

In step 1. Monty hides the car behind curtain #3 1/3 of the time.
In step 2. Alice always chooses curtain #1, which is empty.
In step 3. Monty must open curtain #2 - because it is the only door which is empty and is not Alice's. That of course does not change the location of the car - which is still behind curtain #3.
In step 4. Alice always switches to curtain #3 - because it is still closed. Alice wins.

So Alice always wins if Monty hid the car behind curtain #2 or curtain #3 and Alice always loses if Monty hid the car behind curtain #1. Perhaps suprisingly Alice wins 2/3's the time when she always switches.


There's another formulation of the problem which only uses the facts in the Basic Situation. The Additional Stipulations are not included. Surprisingly Alice can guarentee the same favorable outcome in the Basic Situation that was achievable with the Additional Stipulations! Monty is permitted to choose where to hide the car (H) in step 1. any way he likes. In step 3. he is permitted to choose which curtain to open (S) by any method, as long as he doesn't open curtain C (still forbidden by 3a). It doesn't matter how Monty makes his choices (as long as he obeys 3a), Alice can still win the car surprisingly often.

Here's a paper (in pdf) which explains the Game Theory approach to the Monty Hall Problem: Probabilistic and Game Theoretic solutions to The Three Doors Problem

Friday, October 23, 2009

Quasars

Pending problems in QSOs
Quasars (Quasi Stellar Objects, abbreviated as QSOs) are still nowadays, close to half a century after their discovery, objects which are not completely understood. In this brief review a description of the pending problems, inconsistencies and caveats in the QSO's research is presented. The standard paradigm model based on the existence of very massive black holes that are responsible for the QSO's huge luminosities, resulting from to their cosmological redshifts, leaves many facts without explanation. There are several observations which lack a clear explanation, for instance: the absence of bright QSOs at low redshifts, a mysterious evolution not properly understood; the inconsistencies of the absorption lines, such as the different structure of the clouds along the QSO's line of sight and their tangential directions; the correlation of redshifts between QSOs and galaxies; and many others.

Nonrelativistic Quantum Gravity

Aspects of nonrelativistic quantum gravity Physics preprint.
A nonrelativistic approach to quantum gravity is studied. At least for weak gravitational fields it should be a valid approximation. Such an approach can be used to point out problems and prospects inherent in a more exact theory of quantum gravity, yet to be discovered. Nonrelativistic quantum gravity, e.g., shows promise for prohibiting black holes altogether (which would eliminate singularities and also solve the black hole information paradox), gives gravitational radiation even in the spherically symmetric case, and supports non-locality (quantum entanglement). Its predictions should also be testable at length scales well above the "Planck scale", by high-precision experiments feasible with existing technology.

Tuesday, October 20, 2009

Monday, October 19, 2009

Quantum Effects in Biology

Some quantum weirdness in physiology
Quantum mechanics seems alien to physiology. Alarm bells go off in our heads when we hear even people of such genius as Sir Roger Penrose (1) invoke the weird coherence of quantum mechanical wave functions to explain biological function. Of course, it is only some of the “weirder” parts of quantum mechanics that bother us. Structural biochemistry is founded on the rigid geometrical relationships involved in chemical bonding that arise from quantum mechanics; the α-helix could only have been discovered by Pauling by acknowledging the power of quantum mechanical resonance to flatten the peptide bonding unit (2). Nevertheless, most modern biomolecular scientists view quantum mechanics much as deists view their God; it merely sets the stage for action and then classically understandable, largely deterministic, pictures take over. In this issue of PNAS Ishizaki and Fleming (3), by combining experimental and theoretical investigations, demonstrate that quantum coherence effects play a big role in light energy transport in photosynthetic green sulfur bacteria under physiological conditions. Quantum coherence allows a nonclassical simultaneous exploration of many paths of energy flow through the many chromophores of a light-harvesting complex, thereby significantly increasing the efficiency of the energy capture process, presumably helping the bacteria to survive in low light.

Cosmic Reionization

Reionization and Cosmology with 21 cm Fluctuations
Three major stages in the evolution of our universe are written in the phases of hydrogen. After nucleosynthesis the universe was an ionized plasma of hydrogen and helium. As expansion cooled the universe, hydrogen went through a phase transition, rapidly becoming neutral and releasing the Cosmic Microwave Background light at a redshift of ~1089. High energy photons produced by the firrst stars and quasars later reionized the hydrogen in the inter galactic medium (IGM), forcing the universe back through a second extended and patchy phase transition referred to as the epoch of reionization (EoR).

Saturday, October 17, 2009

Morning Glory

Rhyolitic volcanoes

Rhyolitic volcanoes: the ones to watch in Nature.
The Chaitén volcano in Chile erupted unexpectedly and explosively on 1 May 2008, and it is still erupting. The eruption has displaced over 5,000 people, and resulted in millions of dollars of lost revenue in Chile. It has also provided geophysicists the rare opportunity of directly observing a rhyolite magma fuelled eruption — the cause of some of Earth's largest explosive volcanic eruptions. Jonathan Castro and Donald Dingwell present petrological and experimental evidence to show that the hydrous rhyolite magma at Chaitén ascended very rapidly, with velocities of the order of a metre per second. Such rapid ascent, contrasting markedly with the behaviour of most silicic magmas, implies a transit time from storage depths greater than 5 km to the near surface of only 4 hours, leaving little warning time for such eruptions. This work suggests that rhyolitic volcanoes that have been active during the Holocene — the past 10,000 years or so — should be closely monitored, especially those near major centres of population.

Clovis Era Impact Fails to be Confirmed

Impact theory under fire once more in Nature.
Independent studies are casting more doubt on a controversial theory that a comet exploded over North America nearly 13,000 years ago, wiping out the Clovis people and many of the continent's large animals.

Thursday, October 15, 2009

Fractional quantum Hall Effect Observed in Graphene

Fractional quantum Hall effect and insulating phase of Dirac electrons in graphene
In graphene, which is an atomic layer of crystalline carbon, two of the distinguishing properties of the material are the charge carriers two-dimensional and relativistic character. The first experimental evidence of the two-dimensional nature of graphene came from the observation of a sequence of plateaus in measurements of its transport properties in the presence of an applied magnetic field. These are signatures of the so-called integer quantum Hall effect. However, as a consequence of the relativistic character of the charge carriers, the integer quantum Hall effect observed in graphene is qualitatively different from its semiconductor analogue. As a third distinguishing feature of graphene, it has been conjectured that interactions and correlations should be important in this material, but surprisingly, evidence of collective behaviour in graphene is lacking. In particular, the quintessential collective quantum behaviour in two dimensions, the fractional quantum Hall effect (FQHE), has so far resisted observation in graphene despite intense efforts and theoretical predictions of its existence. Here we report the observation of the FQHE in graphene. Our observations are made possible by using suspended graphene devices probed by two-terminal charge transport measurements. This allows us to isolate the sample from substrate-induced perturbations that usually obscure the effects of interactions in this system and to avoid effects of finite geometry. At low carrier density, we find a field-induced transition to an insulator that competes with the FQHE, allowing its observation only in the highest quality samples. We believe that these results will open the door to the physics of FQHE and other collective behaviour in graphene.

Physics from Pure Geometry

Matter from Space
General Relativity offers the possibility to model attributes of matter, like mass, momentum, angular momentum, spin, chirality etc. from pure space, endowed only with a single field that represents its Riemannian geometry. I review this picture of `Geometrodynamics' and comment on various developments after Einstein.

Monday, October 12, 2009

Gogol Bordello

Here's a goofy video by the band >Gogol Bordello - Supertheory of Supereverything - liberally sprinkled with physics jargon.

Saturday, October 10, 2009

Unseen expressions trigger emotional reactions

Unseen facial and bodily expressions trigger fast emotional reactions
Facial reactions were recorded using electromyography, and arousal responses were measured with pupil dilatation. Passive exposure to unseen expressions evoked faster facial reactions and higher arousal compared with seen stimuli, therefore indicating that emotional contagion occurs also when the triggering stimulus cannot be consciously perceived because of cortical blindness. Furthermore, stimuli that are very different in their visual characteristics, such as facial and bodily gestures, induced highly similar expressive responses

Learning about Odors Requires Generating New Neurons

Olfactory perceptual learning requires adult neurogenesis in PNAS
Perceptual learning is required for olfactory function to adapt appropriately to changing odor environments. We here show that newborn neurons in the olfactory bulb are not only involved in, but necessary for, olfactory perceptual learning. First, the discrimination of perceptually similar odorants improves in mice after repeated exposure to the odorants. Second, this improved discrimination is accompanied by an elevated survival rate of newborn inhibitory neurons, preferentially involved in processing of the learned odor, within the olfactory bulb. Finally, blocking neurogenesis before and during the odorant exposure period prevents this learned improvement in discrimination. Olfactory perceptual learning is thus mediated by the reinforcement of functional inhibition in the olfactory bulb by adult neurogenesis.

How can we measure Galaxy distances?

Cosmology: Dark is the new black in Nature.
Rival experimental methods to determine the Universe's expansion are contending to become the fashionable face of cosmology. Fresh theoretical calculations make one of them the hot tip for next season.

It's difficult to determine distances in astronomy. Distances to galaxies have been measured using three techniques: Type 1a supernova; gravitational lensing; baryon acoustic oscillations - sound waves from the big bang.

Color Blindness Cure in Monkeys

Vision: Gene therapy in colour
Replacing a missing gene in adult colour-blind monkeys restores normal colour vision. How the new photoreceptor cells produced by this therapy lead to colour vision is a fascinating question.

The Monty Hall Problem: A New Book

Two Doors and a Goat is a review in Science Magazine of The Monty Hall Problem: The Remarkable Story of Math's Most Contentious Brain Teaser by Jason Rosenhouse.

Thursday, October 08, 2009

Measurement-based quantum computation

Measurement-based quantum computation
Quantum computation offers a promising new kind of information processing, where the non-classical features of quantum mechanics can be harnessed and exploited. A number of models of quantum computation exist, including the now well-studied quantum circuit model. Although these models have been shown to be formally equivalent, their underlying elementary concepts and the requirements for their practical realization can differ significantly. The new paradigm of measurement-based quantum computation, where the processing of quantum information takes place by rounds of simple measurements on qubits prepared in a highly entangled state, is particularly exciting in this regard. In this article we discuss a number of recent developments in measurement-based quantum computation in both fundamental and practical issues, in particular regarding the power of quantum computation, the protection against noise (fault tolerance) and steps toward experimental realization. Moreover, we highlight a number of surprising connections between this field and other branches of physics and mathematics.

The Flyby Anomaly

Earth Flyby Anomalies
In a reference frame fixed to the solar system's center of mass, a satellite's energy will change as it is deflected by a planet. But a number of satellites flying by Earth have also experienced energy changes in the Earth-centered frame -- and that's a mystery.

Tuesday, October 06, 2009

Phoenix Universe?

Title: The Return of the Phoenix Universe: physic preprint.
Georges Lemaitre introduced the term "phoenix universe" to describe an oscillatory cosmology with alternating periods of gravitational collapse and expansion. This model is ruled out observationally because it requires a supercritical mass density and cannot accommodate dark energy. However, a new cyclic theory of the universe has been proposed that evades these problems. In a recent elaboration of this picture, almost the entire universe observed today is fated to become entrapped inside black holes, but a tiny region will emerge from these ashes like a phoenix to form an even larger smooth, flat universe filled with galaxies, stars, planets, and, presumably, life. Survival depends crucially on dark energy and suggests a reason why its density is small and positive today.

Monday, October 05, 2009

The Deep Ocean was Oxygenated Late

Anoxygenic photosynthesis modulated Proterozoic oxygen and sustained Earth's middle age in PNAS.
Molecular oxygen (O2) began to accumulate in the atmosphere and surface ocean ca. 2,400 million years ago (Ma), but the persistent oxygenation of water masses throughout the oceans developed much later, perhaps beginning as recently as 580–550 Ma. For much of the intervening interval, moderately oxic surface waters lay above an oxygen minimum zone (OMZ) that tended toward euxinia (anoxic and sulfidic).

Economic Downturns are Good for Your Health?

Life and death during the Great Depression in PNAS.
Recent events highlight the importance of examining the impact of economic downturns on population health. The Great Depression of the 1930s was the most important economic downturn in the U.S. in the twentieth century. We used historical life expectancy and mortality data to examine associations of economic growth with population health for the period 1920–1940. We conducted descriptive analyses of trends and examined associations between annual changes in health indicators and annual changes in economic activity using correlations and regression models. Population health did not decline and indeed generally improved during the 4 years of the Great Depression, 1930–1933, with mortality decreasing for almost all ages, and life expectancy increasing by several years in males, females, whites, and nonwhites. For most age groups, mortality tended to peak during years of strong economic expansion (such as 1923, 1926, 1929, and 1936–1937). In contrast, the recessions of 1921, 1930–1933, and 1938 coincided with declines in mortality and gains in life expectancy. The only exception was suicide mortality which increased during the Great Depression, but accounted for less than 2% of deaths. Correlation and regression analyses confirmed a significant negative effect of economic expansions on health gains. The evolution of population health during the years 1920–1940 confirms the counterintuitive hypothesis that, as in other historical periods and market economies, population health tends to evolve better during recessions than in expansions.

Cosmic Rays - mysteries of the sources

IceCube: The Rationale for Kilometer-Scale Neutrino Detectors
At a time when IceCube is nearing completion, we revisit the rationale for constructing kilometer-scale neutrino detectors. We focus on the prospect that such observatories reveal the still-enigmatic sources of cosmic rays. While only a "smoking gun" is missing for the case that the Galactic component of the cosmic-ray spectrum originates in supernova remnants, the origin of the extragalactic component remains a mystery. We speculate on neutrino emission from gamma-ray bursts and active galaxies.

Supernova Cosmology

Foundations of Supernova Cosmology
This is a brief sketch of the use of supernovae to measure cosmological parameters. It traces the early work, the events surrounding the discovery and verification of cosmic acceleration using SN Ia, and the efforts today to make sound inferences about the nature of dark energy. The prospects for minimizing systematics by using near-infrared observations in the supernova restframe are emphasized. This could be an important point in the design of a JDEM that employs supernovae to measure the history of cosmic expansion.

Tycho's Nova

The Periodic Table and Group Theory

From the Mendeleev periodic table to particle physics and back to the periodic table
We briefly describe in this paper the passage from Mendeleev's chemistry (1869) to atomic physics (in the 1900's), nuclear physics (in the 1932's) and particle physics (from 1953 to 2006). We show how the consideration of symmetries, largely used in physics since the end of the 1920's, gave rise to a new format of the periodic table in the 1970's. More specifically, this paper is concerned with the application of the group SO(4,2)xSU(2) to the periodic table of chemical elements. It is shown how the Madelung rule of the atomic shell model can be used for setting up a periodic table that can be further rationalized via the group SO(4,2)xSU(2) and some of its subgroups. Qualitative results are obtained from this nonstandard table.

Friday, October 02, 2009

Anxiety

Understanding the Anxious Mind an article in the New York Times profiling the research of Harvard psychologist Jerome Kagan.

Thursday, October 01, 2009

Value at Risk

Simon Johnson discusses the Value at Risk (VAR) financial analysis technique and other issues in financial modelling in The Economics of Models

A Harvard Critique

The 'Veritas' About Harvard
Harvard has consistently admitted around 1600 undergraduates per year since 1990. The article argues that some of Harvard's wealth might be better spent by increasing undergraduate enrollment.

Tuesday, September 29, 2009

Fashion illustrator Kareem Iliya

Kareem Iliya, fashion illustrator, images can be found here and here.

Monday, September 28, 2009

The Hurt Locker

The Hurt Locker directed by Kathryn Bigelow is quite an intense film about an army bomb disposal unit in Iraq.

Juliette Binoche

French actress Juliette Binoche and English choreographer Akram Khan performed their dance/drama piece In-I at BAM. I saw the closing night peformance, which wound up with a spectacular finale.
She also recently published a book of her paintings "Juliette Binoche, Portraits In-Eyes". The book contains a series of side-by-side pairs of paintings inspired by each of her films. Each pair consists of a painting of the film's director and then a self portrait of herself "in character". Cool. The text is in both French and English.

William Blake at the Morgan Library

William Blake's World: "A New Heaven Is Begun" an exhibit at the Morgan Library in New York. At that link there's a nice reading of "The Tyger" and other poems by Jeremy Irons.
William's Blake's illustrations to the Book of Job can be found here. I was quite surprised by Blake's depiction of Satan: he's rather physically attractive and was not usually shown as particularly "evil looking".

Thursday, September 24, 2009

Massive Violation of Bell's Inequality

Violation of Bell's inequality in Josephson phase qubits in Nature.
The measurement process plays an awkward role in quantum mechanics, because measurement forces a system to 'choose' between possible outcomes in a fundamentally unpredictable manner. Therefore, hidden classical processes have been considered as possibly predetermining measurement outcomes while preserving their statistical distributions1. However, a quantitative measure that can distinguish classically determined correlations from stronger quantum correlations exists in the form of the Bell inequalities, measurements of which provide strong experimental evidence that quantum mechanics provides a complete description2, 3, 4. Here we demonstrate the violation of a Bell inequality in a solid-state system. We use a pair of Josephson phase qubits5, 6, 7 acting as spin-1/2 particles, and show that the qubits can be entangled8, 9 and measured so as to violate the Clauser–Horne–Shimony–Holt (CHSH) version of the Bell inequality10. We measure a Bell signal of 2.0732 0.0003, exceeding the maximum amplitude of 2 for a classical system by 244 standard deviations. In the experiment, we deterministically generate the entangled state, and measure both qubits in a single-shot manner, closing the detection loophole11. Because the Bell inequality was designed to test for non-classical behaviour without assuming the applicability of quantum mechanics to the system in question, this experiment provides further strong evidence that a macroscopic electrical circuit is really a quantum system7.

Genetic Structure of India

Indian ancestry revealed in Nature.
"The mixing of two distinct lineages led to most modern-day Indians."

Ultra-Cold Microscale Optomechanical Oscillator

Demonstration of an ultracold micro-optomechanical oscillator in a cryogenic cavity
Preparing and manipulating quantum states of mechanical resonators is a highly interdisciplinary undertaking that now receives enormous interest for its far-reaching potential in fundamental and applied science. Up to now, only nanoscale mechanical devices achieved operation close to the quantum regime. We report a new micro-optomechanical resonator that is laser cooled to a level of 30 thermal quanta. This is equivalent to the best nanomechanical devices, however, with a mass more than four orders of magnitude larger (43 ng versus 1 pg) and at more than two orders of magnitude higher environment temperature (5 K versus 30 mK). Despite the large laser-added cooling factor of 4,000 and the cryogenic environment, our cooling performance is not limited by residual absorption effects. These results pave the way for the preparation of 100-um scale objects in the quantum regime. Possible applications range from quantum-limited optomechanical sensing devices to macroscopic tests of quantum physics.

Observation of strong coupling between a micromechanical resonator and an optical cavity field
Achieving coherent quantum control over massive mechanical resonators is a current research goal. Nano- and micromechanical devices can be coupled to a variety of systems, for example to single electrons by electrostatic or magnetic coupling, and to photons by radiation pressure or optical dipole forces. So far, all such experiments have operated in a regime of weak coupling, in which reversible energy exchange between the mechanical device and its coupled partner is suppressed by fast decoherence of the individual systems to their local environments. Controlled quantum experiments are in principle not possible in such a regime, but instead require strong coupling. So far, this has been demonstrated only between microscopic quantum systems, such as atoms and photons (in the context of cavity quantum electrodynamics) or solid state qubits and photons. Strong coupling is an essential requirement for the preparation of mechanical quantum states, such as squeezed or entangled states, and also for using mechanical resonators in the context of quantum information processing, for example, as quantum transducers. Here we report the observation of optomechanical normal mode splitting, which provides unambiguous evidence for strong coupling of cavity photons to a mechanical resonator. This paves the way towards full quantum optical control of nano- and micromechanical devices.

Nature 460, 724-727 (2009)
DOI: 10.1038/nature08171

Wednesday, September 23, 2009

Cool Airship Video


The Lockheed P-791.

Gravity Insulators??


I noticed this stone a long time ago on the Tufts campus. A couple of older ladies with pronounced Irish accents read it and pronounced it "a lovely idea", haha.
I wondered at the time how such an outlandish monument ended up at a reputable university. Well Wikipedia Knows All: Gravity Research Foundation

Supersymmetry and Division Algebras

There's a surprising connection between supersymmetry , a hot topic in theoretical physics, and division algebras: the real, complex, quaternion and octonion number systems. Supersymmetry only works in 3,4,6 and 10 space time dimensions. That's because there's a cute little trick which allows us to represent an n+2 dimensional spacetime vector using one number from a division algebra and two additional real numbers. There are only four division algebras - which just happen to have 1,2,4 and 8 dimensions. John Baez Explains It All To You here.

Monday, September 21, 2009

Equal Temperament: Music Meets Mathematics

Generalized continued fractions and equal temperament
It would be nice if we could divide an octave into equal notes and then be able to have an interval close to a perfect fifth (which raises the frequency by 3/2). That's how equal temperament works: it divides an octave into twelve equal notes and then it turns out that an interval of seven notes is close to a perfect fifth. That's actually why this particular scale was chosen and a reason it has been so successful.

Antigravity

Antigravitation
We discuss why there are no negative gravitational sources in General Relativity and show that it is possible to extend the classical theory such that repulsive gravitational interaction occurs.

Interesting, but as the author points out in a previous preprint which provides more details of the theory: A Bi-Metric Theory with Exchange Symmetry "As this example shows, the bi-metric model is not causal ..."

Sunday, September 20, 2009

A Previous Yale Murder, Still Unsolved

Murder Most Yale a 1999 article in Vanity Fair about the murder of Suzanne Jovin a talented and beautiful Yale student - one of her professors was a suspect.

Fractal Cosmology

Fractal Cosmology is a theory of cosmology which models the universe as fractal: the universe is similar to itself at different scales.
Robert L. Oldershaw has published a series of papers in which he conjectures that certain types of stars are may be similiar to ... atoms of corresponding elements.
I would be very surprised if this turned out to be a fruitful approach, but it's a cool concept nonetheless.

Mandelbrot set: an example of a fractal - click for more info, more images

Inconstant Moon

Inconstant Moon is an episode of the Outer Limits American television show. It's based the short story (also titled Inconstant Moon) by Larry Niven. Many of Niven's stories have a basis in science fact, including this one.

Mike Murphy's reaction to the show was something like this "Absolute maximum horror: the world is ending so let's get married - then the world doesn’t end."

Friday, September 18, 2009

Optical Levitation

Cavity optomechanics using an optically levitated nanosphere
Recently, remarkable advances have been made in coupling a number of high-Q modes of nano-mechanical systems to high-finesse optical cavities, with the goal of reaching regimes where quantum behavior can be observed and leveraged toward new applications. To reach this regime, the coupling between these systems and their thermal environments must be minimized. Here we propose a novel approach to this problem, in which optically levitating a nano-mechanical system can greatly reduce its thermal contact, while simultaneously eliminating dissipation arising from clamping. Through the long coherence times allowed, this approach potentially opens the door to ground-state cooling and coherent manipulation of a single mesoscopic mechanical system or entanglement generation between spatially separate systems, even in room temperature environments. As an example, we show that these goals should be achievable when the mechanical mode consists of the center-of-mass motion of a levitated nanosphere.

Wednesday, September 16, 2009

Your Hippocampus Remembers More than You Do

Remembering Without Knowing It
In a memory task in which the subject was shown a photograph and then later asked to pick out that photo among several others, the subject's hippocampus activated when they were seeing the correct photo, even when they ended up choosing the wrong one!

Cosmology Review

Cosmology at a Crossroads
A fundamental question in cosmology is, "How did the universe begin?" The two pivotal ideas of inflation and cold dark matter (CDM), combined with extensive observational results, including the unpredicted accelerated expansion of the universe, underpin a new standard model of cosmology

Neanderthals were more Carnivorous than early modern Humans

Isotopic evidence for the diets of European Neanderthals and early modern humans
Neanderthals mainly fed on big-game, while early modern humans had a more varied diet, sometimes including lots of fish.

Genetics of the Human Expansion Out of Africa

Explaining worldwide patterns of human genetic variation using a coalescent-based serial founder model of migration outward from Africa
It seems that modern humans may have expanded out of Africa without mixing much with the descendants of earlier waves of migration.

Larvae and Adults are Hybrids??

Caterpillars evolved from onychophorans by hybridogenesis
I reject the Darwinian assumption that larvae and their adults evolved from a single common ancestor. Rather I posit that, in animals that metamorphose, the basic types of larvae originated as adults of different lineages, i.e., larvae were transferred when, through hybridization, their genomes were acquired by distantly related animals. “Caterpillars,” the name for eruciforms with thoracic and abdominal legs, are larvae of lepidopterans, hymenopterans, and mecopterans (scorpionflies). Grubs and maggots, including the larvae of beetles, bees, and flies, evolved from caterpillars by loss of legs. Caterpillar larval organs are dismantled and reconstructed in the pupal phase. Such indirect developmental patterns (metamorphoses) did not originate solely by accumulation of random mutations followed by natural selection; rather they are fully consistent with my concept of evolution by hybridogenesis. Members of the phylum Onychophora (velvet worms) are proposed as the evolutionary source of caterpillars and their grub or maggot descendants. I present a molecular biological research proposal to test my thesis. By my hypothesis 2 recognizable sets of genes are detectable in the genomes of all insects with caterpillar grub- or maggot-like larvae: (i) onychophoran genes that code for proteins determining larval morphology/physiology and (ii) sequentially expressed insect genes that code for adult proteins. The genomes of insects and other animals that, by contrast, entirely lack larvae comprise recognizable sets of genes from single animal common ancestors.

I would be surprised if this were true, but it's an interesting and novel hypothesis.

Sanction Threats reduce Reciprocity

Neural responses to sanction threats in two-party economic exchange
Sanctions are used ubiquitously to enforce obedience to social norms. However, recent field studies and laboratory experiments have demonstrated that cooperation is sometimes reduced when incentives meant to promote prosocial decisions are added to the environment. Although various explanations for this effect have been suggested, the neural foundations of the effect have not been fully explored. Using a modified trust game, we found that trustees reciprocate relatively less when facing sanction threats, and that the presence of sanctions significantly reduces trustee's brain activities involved in social reward valuation [in the ventromedial prefrontal cortex (VMPFC), lateral orbitofrontal cortex, and amygdala] while it simultaneously increases brain activities in the parietal cortex, which has been implicated in rational decision making. Moreover, we found that neural activity in a trustee's VMPFC area predicts her future level of cooperation under both sanction and no-sanction conditions, and that this predictive activity can be dynamically modulated by the presence of a sanction threat.

Jumping Robot

Video: Precision Urban Hopper leaps over fences, makes enemies cringe

Yow.

Tuesday, September 15, 2009

Palindromes on the Y Chromosome

New Clues to Sex Anomalies in How Y Chromosomes Are Copied
Most chromosomes come in pairs, which helps in detecting and repairing errors when DNA is copied. However, there's only one copy of the Y chromosome (found only in males) but many of its genes occur in palindromes (sequences which read the same forward and backward e.g. Madam Im Adam). When the Y chromosome is copied, the palindromic regions are folded over, so they can be compared for errors.

Sunday, September 13, 2009

The Simple Art of Murder

The Simple Art of Murder by Raymond Chandler (1950). An essay on the art and practice of the murder mystery.
See also The Simple Art of Murder a 1995 book review by Joyce Carol Oates about Raymond Chandler and an overview and critique of genre fiction.

Thursday, September 10, 2009

The Origin of Farming in Europe: Cultural Diffusion or Migration?

Ancient DNA Says Europe's First Farmers Came From Afar

Dogs and Infants make similiar errors, wolves don't

Like Infant, Like Dog
"The infants apparently believed believed adult instruction more than they believe their own eyes." Dogs behaved similarly.
Dogs: Kids in Fur Coats?

Erasing Fear Memories

Erasing Fear Memories
Memories of stressful events can be extinguished in young animals but are resistent to complete erasure in adults. New research hints at the neurobiological basis for these observations.

Photosystem genes in viruses

Photosystems at the double
Marine cyanobacteria viruses contain genes for both photosystems used in host photosynthesis.

Nano storage scheme which doesn't wear out

Nanotechnology: A gentle jackhammer
A futuristic method of data storage depends on the 'write–read' action of a multitude of tiny silicon tips. The concept of dynamic superlubricity offers a way to avoid the wear that would otherwise cripple them.

The History of Oxygen

Early Earth: Oxygen for heavy-metal fans
Chromium isotopes provide an eyebrow-raising history of oxygenation of Earth's atmosphere. Not least, it seems that oxygen might have all but disappeared half a billion years after its initial rise.

Sex Determination in Birds

Sex determination: Birds do it with a Z gene
The gene that determines sex in birds has eluded scientists for a decade. Now this all-important locus is revealed as a gene on the Z chromosome known for its proclivity for determining sex in all kinds of animals.

In mammals, males have XY chromosome pairs and females are XX, so the Y chromosome determines maleness and sex. In particular the SRY gene found on the Y chromosome determines testis.
In birds it's the other way around: males have ZZ chromosome pairs and females are ZW. However in birds the key gene is again for maleness and it resides on the Z chromosome.

Wednesday, September 02, 2009

Skateboard Park London




Sundial in Westminster London

Sundial at Saint Maragret's Church Westminster London. Also the correction curve to get civil time.

Arcadia by Tom Stoppard

Last night I saw Arcadia a play by Tom Stoppard in London. Ed Stoppard, the playwright's son, performs. The play discusses chaos theory, fractals, the second law of thermodyamics, romance versus rationality, poetry and academic rivalries - all in the format of a drawing room comedy.
I also saw the 1995 New York production directed by Trevor Nunn at Lincoln Center, which was absolutely brilliant.

The poet Lord Byron is a constant but never seen presence in the play which quotes the following lines from one of his poems:

She walks in beauty, like the night
Of cloudless climes and starry skies,
And all that's best of dark and bright
Meets in her aspect and her eyes;
Thus mellow'd to that tender light
Which Heaven to gaudy day denies

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.