Your brain on the edge of chaos

No news to me. I’ve always suspected that. Now, seriously:

Though much of the time it [the brain] runs in an orderly and stable way, every now and again it suddenly and unpredictably lurches into a blizzard of noise.

Neuroscientists have long suspected as much. Only recently, however, have they come up with proof that brains work this way. Now they are trying to work out why. Some believe that near-chaotic states may be crucial to memory, and could explain why some people are smarter than others.

Read whole article by the New Scientist magazine:

Disorderly genius: How chaos drives the brain

A little bit of cosmographic sanity

Finally, an interesting paper on dark energy.

Cosmographic analysis of dark energy [http://arxiv.org/abs/0906.5407]

Authors: Matt Visser (Victoria University of Wellington), Celine Cattoen (Victoria University of Wellington)

Abstract: The Hubble relation between distance and redshift is a purely cosmographic relation that depends only on the symmetries of a FLRW spacetime, but does not intrinsically make any dynamical assumptions. This suggests that it should be possible to estimate the parameters defining the Hubble relation without making any dynamical assumptions. To test this idea, we perform a number of inter-related cosmographic fits to the legacy05 and gold06 supernova datasets, paying careful attention to the systematic uncertainties. Based on this supernova data, the “preponderance of evidence” certainly suggests an accelerating universe. However we would argue that (unless one uses additional dynamical and observational information, and makes additional theoretical assumptions) this conclusion is not currently supported “beyond reasonable doubt”. As part of the analysis we develop two particularly transparent graphical representations of the redshift-distance relation — representations in which acceleration versus deceleration reduces to the question of whether the relevant graph slopes up or down.

Smolin against the timeless multiverse

There is a new article by Lee Smolin at Physicsworld.com, “The unique universe“, where he exposes his metaphysical position on the multiverse and the notion of time as fundamental, not emergent.

My thoughts are close to Smolin on those issues, see my previous post on the multiverse here:

The Universe

and, in a funny side, my cartoon here:

Universes Everywhere

Concerning the question whether time is fundamental or not, my philosophical position is that it is fundamental, although there is a facet of it which can be made artificially emergent. See my essay on concurrent time here .

Favorite Prefaces IV

Classical Mathematical Physics: Dynamical Systems and Field Theories
by Walter Thirring [son of Hans Thirring, who was the co-discoverer of the Lense-Thirring frame effect in general relativity]
(Preface to the second edition).

Since the first edition already contained plenty of material for a one-semester course, new material was added only when some of the original could be dropped or simplified. (…) This involved not only the use of more refined mathematical tools, but also a reevaluation of the word fundamental. What was earlier dismissed as a grubby calculation is now seen as the consequence of a deep principle. Even Kepler’s laws, which determine the radii of the planetary orbits, and which used to be passed over in silence as mystical nonsense, seem to point the way to a truth unattainable by superficial observation: The ratios of the radii of Platonic solids to the radii of inscribed Platonic solids are irrational, but satisfy algebraic equations of lower order. These irrational numbers are precisely the ones that are the least well approximated by rationals, and orbits with radii having these ratios are the most robust against each other’s perturbations, since they are the least affected by resonance effects.

Click-the-Links!

Dear Readers,

Forgive my long delay in writing here. I spent the last few months wondering whether I would shutdown this blog or not. Well, I have decided that I will not, at least, not yet. So here are a few interesting links that I came across recently:

1) From the [PhilPhys] e-mail list, a talk by Stephen Summers (University of Florida).

“Yet More Ado About Nothing: The Remarkable Relativistic Vacuum State”

Abstract: An overview is given of what mathematical physics can currently say about the vacuum state for relativistic quantum field theories on Minkowski space. Along with a review of classical results such as the Reeh-Schlieder Theorem and its immediate and controversial consequences, more recent results are discussed. These include the nature of vacuum correlations and the degree of entanglement of the vacuum, as well as the striking fact that the modular objects determined by the vacuum state and algebras of observables localized in certain regions of Minkowski space encode a remarkable range of physical information, from the dynamics and scattering behavior of the theory to the external symmetries and even the space-time itself. In addition, an intrinsic characterization of the vacuum state provided by the modular objects is discussed. [Foundations of Physics in Greater Paris]

2) A new issue of Philosophia Mathematica is available online [June 2009; Vol. 17, No. 2], in special:

- Mark Balaguer, Fictionalism, Theft, and the Story of Mathematics

- Francesco Berto, The Gödel Paradox and Wittgenstein’s Reasons

3) New edition of Edge:

What’s Next? Dispatches on the Future of Science (Edited by Max Brockman): “A preview of the ideas you’re going to be reading about in ten years.”

FQXi prizes: not my time…

FQXi announced the prizes for the Essay Contest on the Nature of Time. Results are here.

My essay was not awarded.

Favorite Prefaces – III

Theory of Relativity
W. Pauli

(…) I do not conceal to the reader my scepticism concerning all attempts of this kind which have been made until now, and also about the future chances of success of theories [unified field theories] with such aims. These questions are closely connected with the problem of the range validity of the classical field concept in its application to the atomic features of Nature. The critical view, which I uttered in the last section of the original text with respect to any solution on these classical lines, has since been very much deepened by the epistemological analysis of quantum mechanics, or wave mechanics, which was formulated in 1927. On the other hand Einstein maintained the hope for a total solution on the lines of a classical field theory until the end of his life. These differences of opinion are merging into the great open problem of the relation of relativity theory to quantum theory, which will presumably occupy physicists for a long while to come. In particular, a clear connection between the general theory of relativity and quantum mechanics is not yet in sight.

(…)

There is a point of view according to which relativity theory is the end-point of “classical physics”, which means physics in the style of Newton-Faraday-Maxwell, governed by the “deterministic” form of causality in space and time, while afterwards the new quantum-mechanical style of the laws of Nature came into play. This point of view seems to me only partly true, and does not sufficiently do justice to the great influence of Einstein, the creator of the theory of relativity, on the general way of thinking of the physicists of today. By its epistemological analysis of the consequences of the finiteness of the velocity of light (and with it, of all signal-velocities), the theory of special relativity was the first step away from naive visualization. The concept of the state of motion of the “luminiferous aether”, as the hypothetical medium was called earlier, had to be given up, not only because it turned out to be unobservable, but because it became superfluous as an element of a mathematical formalism, the group-theoretical properties of which would only be disturbed by it.

By the widening of the transformation group in general relativity the idea of distinguished inertial coordinate systems could also be eliminated by Einstein as inconsistent with the group-theoretical properties of the theory. Without this general critical attitude, which abandoned naive visualizations in favour of a conceptual analysis of the correspondence between observational data and the mathematical quantities in a theoretical formalism, the establishment of the modern form of quantum theory would not have been possible. In the “complementary” quantum theory, the epistemological analysis of the finiteness of the quantum of action led to further steps away from naive visualizations. In this case it was both the classical field concept, and the concept of orbits of particles (electrons) in space and time, which had to be given up in favour of rational generalizations. Again, these concepts were rejected, not only because the orbits are unobservable, but also because they became superfluous and would disturb the symmetry inherent in the general transformation group underlying the mathematical formalism of the theory.

I consider the theory of relativity to be an example showing how a fundamental scientific discovery, sometimes even against the resistance of its creator, gives birth to further fruitful developments, following its own autonomous course.

Note: This preface was written in 1956, two years before Pauli’s death. That edition is a book made from his original paper “Relativitätstheorie”, in Encyklopädie der mathematischen Wissenschaften, Vol. VI9, (B. G. Teubner, Leipzig 1921), written when he extremely young (about 20 years old), and only six years after the publishing of Einstein’s General Relativity theory.

Favorite Prefaces – II

Conceptual Foundations of Quantum Mechanics
by Bernard d’Espagnat

A few words are here in order concerning the guiding idea that inspired this book. It is that quantum mechanics can be formulated axiomatically, that, for clarity sake, it is of course quite appropriate to do so, but that the axioms in question then have to take the form of (precise and general) “rules of the game,” serving to predict what will be observed. This is a difference with classical mechanics, the axioms of which (Newton’s laws and the rest) are most simply expressed as statements bearing on the structure of some mind-independent reality. It is a fact that attempts at doing the same in quantum physics quickly lead to conceptual muddles (”Are wave functions real?,” “Is collapse real?,” etc.), while, in contrast, viewed as a set of observational predictive rules, quantum mechanics is crystal clear. The rules in question must therefore be considered as being—by far—what is most solid in quantum physics. And it is for this matter-of-fact reason—and not because of any a prior allegiance to positivism, empiricism or what not!—that it was here found advisable to begin by just stating these predictive rules and investigating their consequences. Since no allegiance to phenomenalism is made, the question of the possible interpretation of the said rules in terms of some underlying reality of course remains significant. In fact such a study constitutes, in a sense, the very purpose of the present book. But the corresponding analyses must—-and do, here—come in only in a second stage, after the rules have been duly stated and examined.

Note that the just explained standpoint is precisely the one that gives us maximal freedom concerning interpretation problems, since it bars out any a priori prejudice relative to what constitutes reality. Within it, we are not, right at the start, forced to conceive of reality in terms, either of waves, or of particles, or of “wavicles,” or etc. Any way of thinking of it is a priori admissible, provided only that, in the end, it turns out to be compatible with the observational predictions yielded by the basic quantum rules. But, as will be seen, this condition proves to be a demanding one. It does not leave many vistas open. Indeed the book shows that such an approach gently leads to quite definite ideas concerning the conceptual foundations of the incredibly powerful science that is called quantum mechanics.

News on Gravity Probe B

Interesting results coming from Gravity Probe B, including a better understanding of the discrepancies between the four gyroscopes, leading to better data on geodetic effect and frame dragging effect in all four gyroscopes.

Also, a complete document “Gravity Probe B Science Results—NASA Final Report” is now available from their site.

Favorite prefaces – I

This is the first of a series of posts with short excerpts of prefaces/introductions of books that I find interesting or curious. This is just for fun, but hopefully will lead to a collection of memorable sentences or ideas that compels us further on the subject.

PCT, Spin and Statistics, and All That
by Raymond F. Streater and Arthur S. Wightman

In the beginning, when Dirac, Jordan, Heisenberg, and Pauli created the quantum theory of fields, it was not expected that it would provide a consistent description of Nature. After all, it was only a quantized version of the classical theory of Maxwell and Lorentz, a theory which was well known to be afflicted with diseases arising from the infinite electromagnetic inertia of point particles. Many physicists were of the opinion that any project to make the theory’s mathematical foundation more rigorous was probably ill-advised; first the classical foundation should be set right. Such alterations might so change the basis of the theory that a mathematically rigorous discussion of any preceding version would be entirely irrelevant. More recently, it has been suggested that the trouble is that the theory is too modest; it is not designed to predict the masses of the elementary particles or the values of the coupling constants, and should be fundamentally changed with this in view.

However, attempts to go beyond the theory foundered again and again. What successes were achieved were either phenomenological, or were due to systematic developments of the original formalism. But the quantum theory of fields never reached a stage where one could say with confidence that it was free from internal contradictions–nor the converse. In fact, the Main Problem of quantum field theory turned out to be to kill it or cure it: either to show that the idealizations involved in the fundamental notions of the theory (relativistic invariance, quantum mechanics, local fields, etc.) are incompatible in some physical sense, or to recast the theory in such a form that it provides a practical language for the description of elementary particle dynamics.

The last ten years have seen a number of attempts to meet the situation head on. (The physicists who have engaged in this kind of work are sometimes dubbed the Feldverein. Cynical observers have compared them to the Shakers, a religious sect of New England who built solid barns and led celibate lives, a non-scientific equivalent of proving rigorous theorems and calculating no cross sections.) These efforts have not yet led to a solution of the Main Problem, but they have yielded a number of by-products, very general insights into the structure of a field theory. The present book is devoted to an exposition of some of these general results, the physical ideas they embody, and the mathematics necessary for their proofs.

Lakatos Award 2008

[Via PhilPhys - Philosophy of Physics Mail Group]

The London School of Economics and Political Science announces that this year’s Lakatos Award, of £10,000 for an outstanding contribution to the philosophy of science, goes to:

Richard Healey (University of Arizona), for his book Gauging What’s Real: The Conceptual Foundations of Contemporary Gauge Theories (Oxford University Press, 2007).

He will visit LSE to receive the Award and give the Award Public Lecture during summer term, 2009.

Gauge theories have provided our most successful representations of the fundamental forces of Nature. How though do such representations work to tell us what kind of world our gauge theories reveal to us? Professor Healey’s book describes the representations provided by gauge theories in both classical and quantum physics. He argues that evidence for classical gauge theories of forces (other than gravity) gives us reason to believe that loops rather than points are the locations of fundamental properties. As well as exploring the prospects of extending this conclusion to the quantum gauge theories of the Standard Model of elementary particle physics, the book assesses the difficulties faced by attempts to base such ontological conclusions on the success of these theories.

The Lakatos Award is given for an outstanding contribution to the philosophy of science, widely interpreted, in the form of a book published in English during the previous five years. It was made possible by a generous endowment from the Latsis Foundation. The Award is in memory of the former LSE professor, Imre Lakatos, and is administered by an international Management Committee organised from the LSE.

The Committee, chaired by John Worrall, decides the outcome of the Award competition on the advice of an international, independent and anonymous panel of Selectors.

Solvay Physics Conference 1927

Carver Mead: against Copenhagen

An interesting interview with Carver Mead, author of the (unconventional) Collective Electrodynamics: Quantum Foundations of Electromagnetism.

Weinberg on condensed matter matters

[Via Asymptotia]

Most of us do elementary-particle physics neither because of the intrinsic interestingness of the phenomena that we study, nor because of the practical importance of what we learn, but because we are pursuing a reductionist vision. All of the properties of ordinary matter are what they are because of the principles of atomic and nuclear physics, which are what they are because of the rules of the Standard Model of elementary particles, which are what they are because…well, we don’t know, this is the reductionist frontier, which we are currently exploring.

Weinberg, From BCS to the LHC

You cannot resist us

[Via Sophismata]

Trust yourself.

Unconventional computing

Just received.

…………………..

THE SCIENCE AND PHILOSOPHY OF UNCONVENTIONAL COMPUTING (SPUC09)

Cambridge (UK), March 23-25, 2009

SECOND CALL FOR PAPERS

We welcome submissions on topics normally classified under ‘natural computing’ or ‘unconventional computing’ or ‘hypercomputing’ including (but not restricted to) quantum computing, relativistic computing, biology-based computing, analogue computing, and also submissions on the philosophical implications of these new fields for topics including (but again not restricted to) philosophy of mind, philosophy of mathematics, the Church-Turing thesis.

Each presentation should last no more than 30 minutes; a further 10 minutes will be allowed for discussion.

Those wishing to make a presentation should submit by email a 250-word abstract of their paper to Mark Hogarth (mhogarth@cantab.net); enquiries to the same.

Registration fee (yet to be fixed) will be around £100.

Student bursaries are available.

Conference website: http://web.mac.com/mhogarth/Site/SPUC_Conference.html

ORGANISER

Mark Hogarth (Cambridge, UK)

CONFIRMED INVITED SPEAKERS

Selmer Brinsjord (New York, USA))

Jeff Barrett (Irvine, USA)

Philip Welch (Bristol, UK)

Tim Button (Harvard, USA)

Cristian Calude (Auckland, New Zealand))

István Németi (Budapest, Hungry)

Benjamin Wells (San Francisco, USA)

Hajnal Andréka (Budapest, Hungry)

Apostolos Syropoulos (Xanthi, Greece)

Susan Stepney (York, UK)

Bruce MacLennan (Tennessee, USA)

Peter Kugel (Boston, USA)

Mark Sprevak (Cambridge, UK)

Selim Akl (Kingston, Canada)

José Félix Costa (Swansea, UK)

ADVISORY PANEL

Mike Stannett (Sheffield, UK)

John Tucker (Swansea, UK)

Barry Cooper (Leeds, UK)

Sponsored by EPSRC through HyperNet (the Hypercomputation Research Network, EP/E064183/1)

Something I’d like to do if I were younger….

Just received.

…………………………………………………….

Dear Christine,

I am writing to ask for your assistance in drawing the attention of exceptional, highly motivated students to the Perimeter Scholars International (PSI) program.

PSI is an innovative, Masters level course designed to prepare students for cutting-edge research in theoretical physics. It provides a broad overview, allowing students to choose their preferred specialisation, and extensive tuition in formulating and solving interesting problems.

The due date for applications is February 1st: applications received after this date may still be considered but only as long as places remain available.

A number of outstanding lecturers have already signed up to teach, including for example Yakir Aharonov, Phil Anderson, Matt Choptuik, Nima Arkani-Hamed, John Cardy, Ruth Gregory, Michael Peskin, Sid Redner, Xiao-Gang Wen, and a number of Perimeter Institute research faculty. They will be supported by full-time tutors dedicated to the course.

All accepted students will be fully supported.

For further details, see www.perimeterscholars.org.

Thank you in advance for helping us to make this exciting opportunity known as widely as possible.

With my best wishes,

Neil Turok

Director
Perimeter Institute for Theoretical Physics
Waterloo, Ontario, Canada

Next talk at ILQGS

ILQGS

Tuesday, Jan 13th
Donald Marolf, UC Santa Barbara

Title: Unitarity and holography in gravitational physics

Selected papers of today (gr-qc) #2

Title: Transcending Big Bang in Loop Quantum Cosmology: Recent Advances
Authors: Parampreet Singh
[0901.1301]

Title: Black holes and entropy in loop quantum gravity: An overview
Authors: Alejandro Corichi
[0901.1302]

Sabine and Stefan in Brazil

It was a great pleasure and honor to meet on January 06 my blogger colleagues Sabine and Stefan (Backreaction), here in my city (São José dos Campos) while in their recent holliday trip to Brazil.

Here is a picture that my 9 years-old son took of us (from left to right: Sabine, Stefan, me and Fabiano, my hunsband):

We are standing at the border of the so-called “Banhado“, a large green preservation area on a low plateau, a turistic point of the city. (More pictures of the Banhado can be found here).

Thanks, Sabine and Stefan, for taking your time and energy to visit us! It was a pity, however, that your passage here was too brief to allow us further conversation in person…

[Sabine also reports on our brief meeting over at Backreaction].

Philosophy of Gauge Theory

Here is the preliminary program of the Philosophy of Gauge Theory workshop, to be held on Saturday-Sunday, 18-19 April 2009 at the Center for Philosophy of Science (University of Pittsburgh, USA):

Gauge Fields: What Isn’t There?
Speakers: Richard Healey, James Mattingly

Gauge Metaphysics
Speaker: Tim Maudlin
Comments: Gordon Belot

The Abelian Higgs mechanism
Speaker: Ward Struyve

New and Important Problems
Panel discussion
Speakers: Antigone Nounou, Oliver Pooley

Black Holes and Loop Quantum Gravity

I have just received this message from the International Loop Quantum Gravity Seminar mailing list:

Valencia, March 26-28, 2009

The Workshop on Black Holes and Loop Quantum Gravity will take place in Valencia, Spain, from the 26th to the 28th of March, 2009. The purpose of the workshop is to bring together researchers working on quantum aspects of black holes, with emphasis on ideas that have originated in loop quantum gravity. A partial list of topics to be covered is as follows:

– Black hole entropy in LQG
– Spin foam approach to black holes
– Singularity resolution and information loss
– Prospects for a detailed description of the Hawking radiation
– Comparison between results from LQG and other approaches

This will be a ‘Discussion Workshop’. Therefore a significant time will be set aside for a critical evaluation of ideas that are being pursued in current research and on finding fertile directions for future work.

Selected papers of today (gr-qc)

Title: Quantum field theory on a cosmological, quantum space-time
Authors: Abhay Ashtekar, Wojciech Kaminski, Jerzy Lewandowski
[0901.0933]

Title: Quantum Gravity on the Lattice
Authors: Herbert W. Hamber
[0901.0964]

Title: Quantum theory, noncommutative gravity, and the cosmological constant
problem
Authors: T. P. Singh
[0901.0978]

Title: Singular sources in gravity and homotopy in the space of connections
Authors: E. Gravanis and S. Willison
[0901.1079]

Unexplained signal at 3 GHz from ARCADE 2

This appears to be an interesting news coming from the ARCADE 2 experiment. I quote from their recent paper “Interpretation of the Extragalactic Radio Background”, M. Seiffert et al. 2008, ApJ, submitted (available here):

We have presented evidence for isotropic radio emission detected by ARCADE 2 beyond what can be explained by Galactic emission and the unresolved emission from the known population of discrete sources. The excess emission is consistent with a power law, with an index of −2.56, which is significantly flatter that what might be expected from an unidentified population of faint, diffuse, steep spectrum (index ∼ −2.7) radio sources associated with star-forming galaxies. We have also examined and placed limits on two classes of spectral distortions to the CMB. Such distortions are not supported by the data and cannot explain the excess emission (…)

and

We conclude that the three most important sources of error, Galactic emission, instrumental systematic errors, and radio emission from the faint end of the distribution of known sources, are unlikely to be sufficient to explain the excess emission presented here.

Two of the authors are Brazilian colleagues working at the Astrophysics Division at INPE (National Institute for Space Research, Brazil).

Dyson’s birds and frogs

[Via Peter Woit]

Interesting papers by Salisbury et al.

For my record, I list here some interesting papers by Salisbury et al. which cover fundamental questions of relevance on, should I say, “pre-” quantum gravity matters.

The lines of research are summarized as follows:

- preservation of general coordinate transformation and additional gauge symmetries in the transition from a Lagrangian to a Hamiltonian description;
- the nature of observables in classical general relativity, and their potential usefulness in the construction of an eventual quantum theory of gravity;
- construction of diffeomorphism invariants (observables) in general relativity;
- history of constrained hamiltonians.

The papers of relevance are the following:

- Realization in phase space of general coordinate transformations [Phys. Rev. D 27, 740, 1983];

- Gauge transformations in the Lagrangian and Hamiltonian formalisms of generally covariant theories [gr-qc/9612037 = PRDvol55,no2,658,1997]: establishes the general framework in which gauge variables are retained as canonical variables;

- Reduced phase space: quotienting procedure for gauge theories [math-ph/9811029]: describes an alternative algorithm to the Dirac-Bergmann constraint procedure for constructing a self-consistent Hamiltonian model;

- Gauge group and reality conditions in Ashtekar’s complex formulation of canonical gravity [gr-qc/9912085]: discusses Ashtekar’s complex connection approach to gravity;

- Gauge Transformations in Einstein-Yang-Mills Theories [gr-qc/9912086]: discusses gauge symmetries in Einstein-Yang-Mills models;

- The gauge group in the real triad formulation of general relativity [gr-qc/9912087]: discusses a real triad version of canonical gravity;

- Gauge symmetries in Ashtekar’s formulation of general relativity [gr-qc/0004013]: proposes a gauge averaging procedure modeled after an approach of Rovelli’s, though retaining gauge variables and recognizing the essential distinction between time evolution and realizeable canonical gauge symmetries;

- Quantum general invariance and loop gravity [gr-qc/0105097]: preliminary exploration into the construction of diffeomorphism invariants using dynamical field-dependent finite gauge transformations;

- Quantum General Invariance [Proceedings of the Ninth Marcel Grossmann Meeting held in Rome in 2000 ("Quantum general invariance", in Proceedings of the Ninth Marcel Grossmann Meeting, edited by V.G. Gurzadyan, R. T. Jantzen and R. Ruffini, (World Scientific, New Jersey, 2002), 1300-1301)]: continued the exploration of finite gauge transformations;

- The issue of time in generally covariant theories and the Komar-Bergmann approach to observables in general relativity [ gr-qc/0503013 = Phys.Rev. D71 (2005) 124012]: constructs local invariants through the use of intrinsic coordinates. This can be accomplished in the canonical framework in general relativity using Weyl curvature scalars, as was first suggested by Komar and Bergmann. One essential new observation in this work is the recognition that gauge variables become functionals of the non-gauge variables, and consequently in the quantum theory they become subject to fluctuations. In particular, in canonical quantum gravity the light cone is itself fluctuating [the authors supposedly show that there is no conceptual problem for the canonical formulation of generally covariant theories because the mathematical identification of the Hamiltonian as a gauge generator is erroneous (resolution of the time evolution versus gauge problem)];

- Rosenfeld, Bergmann, Dirac and the Invention of Constrained Hamiltonian Dynamics [physics/0701299]: In a paper appearing in Annalen der Physik in 1930 Leon Rosenfeld invented the first procedure for producing Hamiltonian constraints. He displayed and correctly distinguished the vanishing Hamiltonian generator of time evolution, and the vanishing generator of gauge transformations for general relativity with Dirac electron and electrodynamic field sources. Though he did not do so, had he chosen one of his tetrad fields to be normal to his spacetime foliation, he would have anticipated by almost thirty years the general relativisitic Hamiltonian first published by Paul Dirac.

Links will be added later [Edit: almost all included now]. It would be interesting to follow these matters in light of recent advances in canonical quantum gravity. Marcus over at Physics Forums have prepared a selection (actually, an invitation to a poll) of papers published in the arxiv in 2008 in canonical quantum gravity.

Searching for BWV 245 score

I am looking for the scores of Bach’s Saint John’s Passion BWV 245, vocal and piano, in particular, the soprano cantata “Zerfließe, mein Herze, in Fluten der Zähren”. Up to now, my search was in vain.

Also, I need a good translation of the lyrics. For the moment, my german is very poor, I must admit. Here is what I managed to do:

Zerfließe, mein Herze, in Fluten der Zähren
Dem Höchsten zu Ehren!
Erzähle der Welt und dem Himmel die Not:
Dein Jesus ist tot!

Dissolve, my heart, in tides of the ???
to the highest one in honours!
Tell to the world and the sky the emergency:
Your Jesus is dead!

Is there a soul out there that could help me? My email is christinedantas [arroba] yahoo [ponto] com. I would be very much grateful…

On the Nature of Time — essay competition

I have submitted an essay to the FQXi competition. If you are interested in reading it, click here.

Title: On the Nature of Time – Or Why Does Nature Abhor Deadlocks?

Essay Abstract

This essay aims at introducing a novel point of view on the nature of time, inspired by a synthesis of three seemingly unrelated concepts: Bergson’s notion of duration, Dijkstra’s notion of concurrency, and Mach’s notion of inertia.

Edit (June 9th 2009): Apparently, the essays on the nature of time are no longer available at the FQXi site. I have made a very few small corrections and modifications in my essay and a new version is available here (pdf file).

The most extraordinaire Brazilian soprano

I invite you to watch this video — be patient until the grand finale. What you will see is Niza de Castro Tank when she was 50+ years old, in the 80’s, singing an aria of the opera “Il Guarany” by the Brazilian composer Carlos Gomes. I had the opportunity to meet her in some occasions and in a few master classes. She is still singing. A truthful phenomenon. She is not very well-known outside Brazil. Enjoy.

Edit: if you would like to read some of the comments (some available in English) over at the youtube site, click here.

Click-the-Links! 2

Never Say Die: Why We Can’t Imagine Death

Does Nature Break the Second Law of Thermodynamics?

Seven of the greatest scientific hoaxes