Thursday, June 25, 2009

Valentini's Critique of Quantum Theory

Is Quantum Mechanics Tried, True, Wildly Successful, and Wrong?
A skeptical physicist charges that his field has been wandering in a philosophical wilderness for 80 years. The good news: He thinks he knows the way out.

Many of Antony Valentini's other papers can also be found at arXiv by clicking on the author's name in this link: Quantum Theory at the Crossroads: Reconsidering the 1927 Solvay Conference
We reconsider the crucial 1927 Solvay conference in the context of current research in the foundations of quantum theory. Contrary to folklore, the interpretation question was not settled at this conference and no consensus was reached; instead, a range of sharply conflicting views were presented and extensively discussed. Today, there is no longer an established or dominant interpretation of quantum theory, so it is important to re-evaluate the historical sources and keep the interpretation debate open. In this spirit, we provide a complete English translation of the original proceedings (lectures and discussions), and give background essays on the three main interpretations presented: de Broglie's pilot-wave theory, Born and Heisenberg's quantum mechanics, and Schroedinger's wave mechanics. We provide an extensive analysis of the lectures and discussions that took place, in the light of current debates about the meaning of quantum theory. The proceedings contain much unexpected material, including extensive discussions of de Broglie's pilot-wave theory (which de Broglie presented for a many-body system), and a "quantum mechanics" apparently lacking in wave function collapse or fundamental time evolution. We hope that the book will contribute to the ongoing revival of research in quantum foundations, as well as stimulate a reconsideration of the historical development of quantum physics. A more detailed description of the book may be found in the Preface. (Copyright by Cambridge University Press (ISBN: 9780521814218), expected publication date 2007.)

Cosmic Reionization

Computer Simulations of Cosmic Reionization
The cosmic reionization of hydrogen was the last major phase transition in the evolution of the universe, which drastically changed the ionization and thermal conditions in the cosmic gas. To the best of our knowledge today, this process was driven by the ultra-violet radiation from young, star-forming galaxies and from first quasars. We review the current observational constraints on cosmic reionization, as well as the dominant physical effects that control the ionization of intergalactic gas. We then focus on numerical modeling of this process with computer simulations. Over the past decade, significant progress has been made in solving the radiative transfer of ionizing photons from many sources through the highly inhomogeneous distribution of cosmic gas in the expanding universe. With modern simulations, we have finally converged on a general picture for the reionization process, but many unsolved problems still remain in this young and exciting field of numerical cosmology.

Tuesday, June 23, 2009

Graphene

Graphene: Status and Prospects
Graphene is a wonder material with many superlatives to its name. It is the thinnest material in the universe and the strongest ever measured. Its charge carriers exhibit giant intrinsic mobility, have the smallest effective mass (it is zero) and can travel micrometer-long distances without scattering at room temperature. Graphene can sustain current densities 6 orders higher than copper, shows record thermal conductivity and stiffness, is impermeable to gases and reconciles such conflicting qualities as brittleness and ductility. Electron transport in graphene is described by a Dirac-like equation, which allows the investigation of relativistic quantum phenomena in a bench-top experiment. What are other surprises that graphene keeps in store for us? This review analyses recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.

The Evolution of Sex

On the Origin of Sexual Reproduction
Sexual reproduction is costly, so what are the benefits? One of the hypotheses has a catchy name: the Red Queen theory - from the Lewis Carroll character who tells Alice she must keep running faster just to stay in the same place. In biology it's the theory that organisms have to keep changing to keep ahead of their parasites. The recombination of characteristics in sexual reproduction may help.
The widespread system of sexual reproduction found in humans and many other eukaryotes alternates haploid and diploid stages. In humans the gametes (egg and sperm) are hapolid, they only have one copy of each chromosome, while embryos and adult forms are diploid, they have two copies of each chromosome. There's an elaborate mechanism, meiosis, which converts the diploid form into the haploid form. There's another mechanism, ferilizaton, which goes from two haploid forms (the egg and sperm) to the diploid form.

The Evolution of Meiosis From Mitosis
... if there is one event in the whole evolutionary sequence at which my own mind lets my awe still overcome my instinct to analyse, and where I might concede that there may be a difficulty in seeing a Darwinian gradualism hold sway throughout almost all, it is this event—the initiation of meiosis. W. J. HAMILTON (999, p. 419)
THE origins of meiosis in early eukaryotic history have never been satisfactorily explained. Since the reduction-division process in meiosis is essential for sexual life cycles, discussion of the origins of meiosis has been closely tied to debates about the evolutionary value of sex itself and the selective pressures for its maintenance. Yet the cytological events involved in the origins of meiosis are as puzzling as the question of selective pressures. While meiosis almost certainly evolved from mitosis, it has not one but four novel steps: the pairing of homologous chromosomes, the occurrence of extensive recombination between non-sister chromatids during pairing, the suppression of sister-chromatid separation during the first meiotic division, and the absence of chromosome replication during the second meiotic division. This complexity presents a challenge to any Darwinian explanation of meiotic origins. While the simultaneous creation of these new features in one step seems impossible, their step-by-step acquisition via selection of separate mutations seems highly problematic, given that the entire sequence is required for reliable production of haploid chromosome sets. Both Maynard Smith (1978) and Hamilton (1999) regarded the origins of meiosis as one of the most difficult evolutionary problems.


This article discusses something which always bothered me. In meiosis, the chromosomes are replicated first, resulting in four copies of each homolog chromosome. But each gamete requires only one copy. Why not seperate into two gametes directly, without the initial replication - it seems simpler. Apparently, since meiosis evolved from mitosis, and the initial replication is very similiar to what happens in mitosis, it is a relatively simple evolutionary change.
Thus, and perhaps counterintuitively, the evolution of two-step meiosis requires fewer new events than the seemingly simpler one-step process


This article proposes that the main benefit of meiosis is prevention of damage during recombination. Recombination itself is helpful for repairing damaged chromosomes.

Monday, June 22, 2009

Wavefunction Uncollapse

Uncollapsing the wavefunction by undoing quantum measurements
We review and expand on recent advances in theory and experiments concerning the problem of wavefunction uncollapse: Given an unknown state that has been disturbed by a generalized measurement, restore the state to its initial configuration. We describe how this is probabilistically possible with a subsequent measurement that involves erasing the information extracted about the state in the first measurement.

Thursday, June 18, 2009

Fool's Gold

Fool's Gold: How the Bold Dream of a Small Tribe at J.P. Morgan Was Corrupted by Wall Street Greed and Unleashed a Catastrophe. Author Gillian Tett follows the staff of J.P. Morgan as they developed new financial instruments (various kinds of derivatives) to better manage risk - and which ended up being used in very risky ways that significantly contributed to the current financial meltdown.

Tuesday, June 16, 2009

Carlos Castenada

Carlos Castenada was a UCLA anthropology student who wrote a popular series of books in the 1970's about his research into the practices of native Mexican "sorcerers" which included the consumption of psychoactive plants. As it turns out, he also had a cult, based in Los Angeles, largely of women devotees, some of whom were supposed to be witches. When Castenada died of cancer in the late nineties, five of the women disappeared without a trace - it is assumed they committed suicide. A skeleton found in Death Valley was identified as one of the "witches" in 2006. See The dark legacy of Carlos Castaneda in Salon and The Sorcerer's Apprentice: My Life with Carlos Castaneda by Amy Irving.

Isotope Separation

SWU for U and Me by Jeremy Bernstein. Urananium isotope seperation has been in the news of late because of Iran's efforts in this arena. This paper explains some of the theory behind gas centrifuges and some of the fascinating history as well. If equations aren't your cup of tea, try skipping past those sections to the ancedotes.

Wednesday, June 10, 2009

The Evolution of Cell membranes

Cell membranes are largely composed of phospholipids. Phospholipids in turn are built on a glycerol phosphate. The are two different glycerol phosphates in use, glycerol-1-phosphate (G1P) and glycerol-3-phosphate (G3P). The archaea use G1P and the eubacteria and the eukaryotes use G3P. The two phospholipids are synthesized in entirely different ways. The mystery is, how did two such different systems evolve, and what was the nature of the common ancestor? Compounding the mystery, eukaryote transciption and translation is similiar to the archea, while eukaryote cell membranes are similar to bacteria. See Ancestral lipid biosynthesis and early membrane evolution and archea cell membranes.

Tuesday, June 09, 2009

Julian Schnabel

The Nerve and the Will is a beautiful review of the work of Julian Schnabel, in the New York Review of Books.

Wednesday, June 03, 2009

Machiavellian Monkeys

Never Trust a Hungry Monkey
Monkeys give false alarms and then take food when the other monkeys run off.

Mechanical Entanglement

Quantum mechanics: Entanglement goes mechanical
A neat experiment shows that the mechanical vibration of two ion pairs separated by a few hundred micrometres is entangled — their motions are intrinsically and inseparably connected in a quantum way.

Entangled mechanical oscillators
Hallmarks of quantum mechanics include superposition and entanglement. In the context of large complex systems, these features should lead to situations as envisaged in the 'Schrödinger's cat'1 thought experiment (where the cat exists in a superposition of alive and dead states entangled with a radioactive nucleus). Such situations are not observed in nature. This may be simply due to our inability to sufficiently isolate the system of interest from the surrounding environment2, 3—a technical limitation. Another possibility is some as-yet-undiscovered mechanism that prevents the formation of macroscopic entangled states4. Such a limitation might depend on the number of elementary constituents in the system5 or on the types of degrees of freedom that are entangled. Tests of the latter possibility have been made with photons, atoms and condensed matter devices6, 7. One system ubiquitous to nature where entanglement has not been previously demonstrated consists of distinct mechanical oscillators. Here we demonstrate deterministic entanglement of separated mechanical oscillators, consisting of the vibrational states of two pairs of atomic ions held in different locations. We also demonstrate entanglement of the internal states of an atomic ion with a distant mechanical oscillator. These results show quantum entanglement in a degree of freedom that pervades the classical world. Such experiments may lead to the generation of entangled states of larger-scale mechanical oscillators8, 9, 10, and offer possibilities for testing non-locality with mesoscopic systems11. In addition, the control developed here is an important ingredient for scaling-up quantum information processing with trapped atomic ions

Giant Neutrinos from the Big Bang

Quantum physics: Attack of the giant neutrinos
Quantum Coherence of Relic Neutrinos

Tuesday, June 02, 2009

What is the entropy of the universe?

What is the entropy of the universe?
Standard calculations suggest that the entropy of our universe is dominated by black holes, whose entropy is of order their area in Planck units, although they comprise only a tiny fraction of its total energy. Statistical entropy is the logarithm of the number of microstates consistent with the observed macroscopic properties of a system, hence a measure of uncertainty about its precise state. Therefore, assuming unitarity in black hole evaporation, the standard results suggest that the largest uncertainty in the future quantum state of the universe is due to the Hawking radiation from evaporating black holes. However, the entropy of the matter precursors to astrophysical black holes is enormously less than that given by area entropy. If unitarity relates the future radiation states to the black hole precursor states, then the standard results are highly misleading, at least for an observer that can differentiate the individual states of the Hawking radiation.