Wednesday, December 31, 2008

Classical Gauge Theory Genesis

In the beginning God created the heaven and the earth.

God designed the matter Hamiltonian H(p,x).

And the earth was without form, and void; and darkness was upon the face of the deep. And the spirit of God moved upon the face of the waters.


Something seemed missing, God pondered.

And God said, Let there be light.      

 Let p → p - qA

And there was light.


Kerson Huang, Fundamental Forces of Nature - The Story of Gauge Fields, World Scientific, 2007

Sunday, June 15, 2008

La nostalgie n'est plus ce qu'elle était *

(Rafael Rosende, excerpt from a conversation with Rodrigo Rojas)

Con el tiempo el pasado
se va nos va alejando y deformando.

Las sensaciones y emociones
se van desvaneciendo.

De un lugar entrañable
-lo que llamamos pasado-
se ha ido convirtiendo,
paulatinamente,
en algo extraño y lejano
del cual tenemos
un vago recuerdo
por lo que se requiere
de cierto voluntarismo
para traerlo al presente.

Los elementos que hoy nos lo recuerdan
están cada vez más distorsionados y degradados
-cuando no han desaparecido simplemente-.

Tenemos que hacer un esfuerzo
de imaginación y fe,
para creer que los espacios perdidos,
de aquellos tiempos, realmente existieron.

Lo confirmamos, las más de las veces,
cuando volvemos a encontrarnos
con algún ser querido
a quien no hemos visto por largo tiempo,
o cuando volvemos a pasar
por lugares que nos recuerdan otros tiempos,
aunque con una cierta extrañeza;
una sensación de 'Déjà vu', más parecida
al rastro que dejan los sueños,
o una foto que encontramos
en algún cajón olvidado.

Por otra parte,
el presente es algo tan fugaz
que casi no deja rastro.

Tal vez tenga que ver
con el hecho de que mientras
más rápido incorporamos información,
más rápido olvidamos,
o probablemente ya no registramos como antes,
ni conservamos de forma tan intensa
las impresiones de lo que nos está ocurriendo.

Nos hemos convertido
en procesadores más o menos eficaces
de la contingencia personal, familiar y global,
recurriendo inconscientemente
al cúmulo de experiencias pasadas
de las cuales extraemos,
ciertos patrones o regularidades,
alguna enseñanza,
o en el mejor de los casos,
algunas gotas de sabiduría.

Si nos mostraran
a nosotros mismos,
tal cual fuimos
hace treinta o cuarenta años,
tal vez no nos reconoceríamos.

Einstein dijo
-cuando tenía unos sesenta años-
que a esa edad
uno no está en condiciones
de comprender cabalmente
quién era uno cuando tenía 18.

Lo está viendo desde el futuro
-cuando las cosas ya ocurrieron-
lo que cambia radicalmente
la perspectiva de quien uno era
cuando el porvenir, su devenir,
con la necesaria incertidumbre
y providencial esperanza
estaba por desenvolverse.

Lo que a uno más le interesaba
en aquel momento,
hoy en día tal vez
no le llame la atención.

Aunque, igual,
pienso que encontraríamos
ciertos rasgos reconocibles en uno
así como en nuestros familiares y amigos,
que revelarían el vínculo indisoluble
que nos confiere una identidad
en permanente proceso de elaboración.

Tal vez sea,
como dijo alguien por ahí,
que el desarrollo de una vida
sea un permanente ensayo
y preparación para abandonarla.

Cada vez que algún ser querido parte,
estamos enviando parte de nuestro equipaje
(los recuerdos y afectos compartidos)
con los que emprendieron el viaje.

Disculpa, Rodrigo, este tono melancólico
del texto, me debe estar ocurriendo
-guardando las distancias-
lo que mencionaba Roberto Merino
en un artículo reciente:
que el que escribe agarra vuelo
con un cierto tema,
independientemente del estado de ánimo;
una palabra lleva a la otra,
y en una de esas,
el resultado no tenga nada que ver
con el estado de ánimo de uno
o lo que 'realmente' está sintiendo...


* Este é o título da autobiografia de Simone Signoret (RR a FS)

Saturday, June 14, 2008

Tres de las Máximas de François de La Rochefoucauld

(Sent to me by Rafael Rosende)

• Lo que más debería humillar
a los hombres que
han merecido grandes elogios
es el afán con que aún aspiran
a sobresalir por pequeñeces.

• Los enemigos se acercan más a la verdad
al opinar sobre nosotros mismos
de lo que nos acercamos nosotros mismos.

• El acento de la tierra donde se nació
permanece pegado a la mente y al corazón
lo mismo que la lengua.


Tres más:

• A veces somos tan diferentes
de nosotros mismos
como de los demás.

• Prometemos según nuestras esperanzas
y cumplimos según nuestros temores.

• Pocos saben ser viejos
hay que esforzarse
por dominar tan difícil disciplina.
Nos falta experiencia
a pesar de que los años se acumulan.

Tuesday, May 13, 2008

Smyrna, 1922

I can't sleep, thinking about Smyrna, about the suffering of the its people tortured and killed and the sudden end of a world that seemed to be made to last forever. All those modern buildings in what is now called Izmir are just monuments to one the greatest hypocrisies of humankind.

http://www.economist.com/books/displaystory.cfm?story_id=11288325

Monday, April 28, 2008

Peleas de Poetas

Carla Cordua recuerda en un reciente artículo
las peleas entre poetas, entre las que
vale la pena recordar una de Ezra Pound.

Enfurecido desafió a duelo a un poeta menor,
Lascelles Abercrombie, porque, como explicó Pound:
"La estupidez llevada más allá de cierto punto
se convierte en una amenaza pública".

El derecho a elegir las armas
correspondía a Abercrombie,
que propuso "apedrearse mutuamente
con los ejemplares no vendidos de sus libros..."

Rafael Rosende

Sunday, February 17, 2008

Computer Science as a way to explore the universe

Vilson Vieira has called my attention to Scott Aaronson MIT course 6.080 Great Ideas in Theoretical Computer Science. In his Lecture 1 we find the following very interesting characterization of computer science:

2 What is computer science?

Computer science is not glorified programming. Edsger Dijkstra, Turing Award winner and extremely opinionated man, famously said that computer science has as much to do with computers as astronomy has to do with telescopes. We claim that computer science is a mathematical set of tools, or body of ideas, for understanding just about any system—brain, universe, living organism, or, yes, computer. Scott got into computer science as a kidbecause he wanted to understand video games. It was clear to him that if you could really understand video games then you could understand the entire universe. After all, what is the universe if not a video game with really, really realistic special effects?
OK, but isn’t physics the accepted academic path to understanding the universe? Well, physicists have what you might call a top-down approach: you look for regularities and try to encapsulate them as general laws, and explain those laws as deeper laws. The Large Hadron Collider is scheduled to start digging a little deeper in less than a year.

Computer science you can think of as working in the opposite direction. (Maybe we’ll eventually meet the physicists half-way.) We start with the simplest possible systems, and sets of rules that we haven’t necessarily confirmed by experiment, but which we just suppose are true, and then ask what sort of complex systems we can and cannot build.

Wednesday, December 12, 2007

Airbuses, rain, short runways, poor training and budget maintenance

During the flare at thrust reduction, select all thrust levers to IDLE

To sum up, when approaching at 20 ft radio altitude, only thrust lever 1 was
pulled back and the "Retard" warnings was neglected as thrust lever 2 was not pulled back to "Idle" position. The aircraft's landing speed was not decreased efficiently as a result of inactivation of ground spoilers and auto braking system after touchdown. Meanwhile, because the thrust output of engine 2 was remained at EPR 1.08 and the wet runway became slippery, the aircraft was not able to achieve substantial speed reducing on the residual runway and overrun the runway though the maximum manual braking was applied.
From: http://www.asc.gov.tw/acd_files/189-c1contupload.pdf

It is impressive how the Report on the Runway Overrun During Landing On Taipei Sungshan Airport TRANSASIA AIRWAYS FLIGHT 536 fits well A 320 TAM flight 3045 tragedy.

La belleza matematica...

Los matemáticos disipan,
a cualquier precio,
las huellas de sus pasos.

Disponen señuelos a lo largo del camino
y a poco andar la pista se pierde.

Al presentarse,
la teoría omite vacilaciones,
desvíos, callejones sin salida.

Existe desde siempre, diríase,
tal como luce en libros y artículos.

Gian-Carlo Rota observó
el subsuelo de su propio saber
y describió en límpida prosa
la tiniebla que florece
alrededor de lemas y axiomas.

Propongo algunos asertos y acertijos
acerca de los conceptos de belleza,
de verdad y de prueba en la matemática.

Extractado del libro Shaftesbury o la Vacilación
Godofrefo Iommi Amunátegui
Ediciones Universitarias de Valparaíso
Pontificia Universidad Católica de Valparaíso.

Lo que viene a continuación tiene como
fuente el libro de Gian-Carlo Rota,
Indiscrete Thoughts,
Birkhäuser, ed. F. Palombi, 1997,
textos citados en el primer libro:

La belleza de la matemática
prescinde de la estética.

E incluso del rigor.

No obstante es un propiedad objetiva.

Que no cabe buscar o enseñar.

A veces sólo un paso,
apenas perceptible,
de un teorema es bello
y la secuela deja de serlo
debido a la vehemencia de la deducción.

Elegancia y belleza difieren.

La primera se despliega
en la presentación de una teoría.

A los matemáticos les cuesta admitir
que buena parte de su labor consiste
en pulir y afinar resultados conocidos.

El trabajo original rara vez es bello.

A menudo la gente del oficio
alude a la redundancia y a la oscuridad.

Y en tales ocasiones suele inquirir:
"¿Para qué sirve todo esto?"

Curiosa cavilación
puesto que la matemática pura
-la mayoría de las veces-
no sirve para nada.

Esclarecer el alcance de esta pregunta
permite atisbar el sentido de la belleza matemática
cuya clave se esconde en una falacia:
olvidando penurias y esfuerzos dedicados
a captar el quid de una prueba,
la belleza se define como súbita iluminación.

En un instante desaparece de la memoria
toda dificultad, todo contratiempo.
Sólo permanece el destello.

La expresión: "¿Para qué sirve todo esto?" manifiesta perplejidad.

De ningún modo indica que los matemáticos se hayan extraviado
en una demostración o que ignoren posibles aplicaciones.

Por el contrario la exclamación surge cuando ha concluido
el desarrollo de la prueba y se ha verificado su validez lógica. ¿Entonces?

Algo falta. La verdad de un resultado no muestra su significado.

Una prueba es bella
cuando desvela
el secreto del teorema
y le otorga sello inevitable.

Tal claridad se oculta tras la pregunta
y fundamenta la matemática.

La belleza es una figura del lenguaje
construida para indicarla.

De manera oblicua y desde lejos...

Rafael Rosende

Leer y caminar

Leer y caminar son dos caras
de una misma adicción.

El que tiene vocación de caminante
posee una mezcla muy rigurosa
de determinación y azar.

Caminar a ciegas
es una manera
de leer sobre la marcha
los signos de una ciudad cambiante,
y por ende perpetuamente
desconocida y ajena,
aunque con un aire de déjà vu.

Dejarse llevar,
vagabundear sin término,
llegar incluso a perderse...

Leer con los pies
lo que en la ciudad
sólo puede sobrevivir
en calidad de ruina.

Hacerla brillar por última vez
con la mirada melancólica
de un anacronismo.

El resplandor fugaz, casi póstumo,
que envuelve dichos rincones
que acogieron el paraíso de la infancia
y que en el presente se encuentran
en acelerado proceso de extinción,
momentos antes que en su ocaso
desaparezcan para siempre...

..............................

[Saqueo y adaptación de unos textos
de Alan Pauls, escritos teniendo a Borges en mente.]

Rafael Rosende

Consecuencias de la aceleración a pequeña y gran escala

Las noticias relativamente recientes
(de los últimos diez años)
acerca del estado de situación
de la expansión de Universo,
el cual estaría evidenciando
una fase de aceleración
en su ritmo de expansión,
tiene como una de sus
consecuencias más estremecedoras,
el hecho de que en un futuro lejano
(desde nuestra perspectiva temporal)
el universo comenzará a desaparecer
del horizonte visible,
comenzando por las galaxias más lejanas.
El ritmo de expansión impedirá
que la luz de aquellos lejanos faros
lleguen hasta nosotros.

Paulatinamente nos iremos
quedando aislados
y reducidos al grupo
local de galaxias
-nuestro vecindario astronómico-
como en una especie
de agujero negro
sin poder obtener
información de
lo que se encuentra
un poco más allá.

Cuando ello ocurra
las dos principales galaxias
del Grupo Local:
la majestuosa Andrómeda
y la no menos espectacular
Vía Láctea, donde residimos,
habrán trabado contacto
"fundiéndose" y confundiéndose
en una sola galaxia...

¿No nos estará pasando
algo parecido a nuestra escala,
en que la aceleración
de la vida contemporánea,
nos va paulatinamente aislando
-por falta de tiempo-
del contacto y comunicación
con nuestros seres queridos,
comenzando por nuestros
parientes lejanos,
pasando por nuestros amigos
hasta llegar a nuestra
propia familia inmediata?

Rafael Rosende

The role of impossibility

Universes that are complex enough
to give rise to consciousness
impose limits on what can be known
about them from within.

There is more to impossibility
than first meets the eye,
its role in our understanding
of things is far from negative.

We will gradually come to appreciate
that the things that cannot be known,
that cannot be done, and cannot be seen,
define our Universe more clearly,
more completely, and more sharply
than those that can.

John D. Barrow

(sent by Rafael Rosende)

Lo cortés no quita lo valiente, y viceversa

Como afirmara un columnista recientemente:
lo cortés no quita lo valiente y viceversa.

Un ideal al que hay que tratar de acercarse.

Es sabio, además de bueno,
el estar abierto a escuchar,
respetando a los que piensan distinto
y no confundir
la legítima indignación moral
frente a la injusticia atroz,
con la furia ante lo que,
simplemente, nos disgusta.

Es cierto que
hay que armarse de paciencia
para soportar ciertas diatribas,
pero en algunos casos,
es más cuestión de desarrollar la sensibilidad
para apreciar al que da la lata con estilo,
así como como puede ser una experiencia interesante
escuchar al que vende su pomada con fundamento...

Rafael Rosende

Cultura Ambiental

El tema del cumplimiento
de la normativa ambiental,
tiene efectos tanto para la vida humana
como para la vida silvestre
y la estabilidad de los ecosistemas.

Aunque en Chile se habla mucho del tema,
en la práctica no hemos incorporado
a nuestra cultura y costumbres
el respeto por las normas mínimas
de salud ambiental para el país.

Esto ocurre a todo nivel.

Si el problema fuera de falta de recursos
pero existiera la buena disposición,
aunque no fuera excusa para
no cumplir con la norma ambiental,
uno podría, en principio, comprender la situación.

Pero si esto se da
-como informa la prensa en el día de hoy-
en una empresa de envergadura mundial
con recursos y tecnología, como es Codelco,
que tuvo cinco años para adecuar
sus procesos productivos a la norma
de protección del medio ambiente chileno,
y no las cumple, que se espera para el resto.

Cuatro de sus divisiones:
Andina, El Teniente, El Salvador y Ventanas
contaminan con residuos líquidos (riles) ríos y mar
en porcentajes altísimos.

Un par de ejemplos:

Codelco División Andina tiene 14 puntos de descargas,
de los cuales 7 no cumplen con las normas del Decreto 90
que hace cumplir la Superintendencia de Servicios Sanitarios.

Medición Río Blanco, afluente del Río Aconcagua
Fecha Octubre 2006
Aguas botaderos minas

Valor límite Concentración % sobre la norma

Aluminio 5 mg/l 263 mg/l 5.260,0 %
Boro 0,75 mg/l 1,86 mg/l 248,0 %
Cadmio 0,01 mg/l 0,14 mg/l 1.400,0 %
Cobre 1 mg/l 777 mg/l 77.700,0 %
Hierro Disuelto 5 mg/l 42,9 mg/l 858,0 %
Niquel 0,2 mg/l 0,63 mg/l 315,0 %
Sulfatos 1.000 mg/l 4.544 mg/l 454,5 %
Zinc 3 mg/l 23,6 mg/l 786,6 %
Ph 6,0-8,5 3,03


Estos metales contaminantes en el agua
se incorporan al utilizarse parte
de dicho caudal, corriente más abajo
del río Aconcagua, para el riego de
hortalizas, verduras...o al descargarse
en el mar, en la contaminación
de mariscos y pescados,
con grave daño a la salud humana.

En Ventanas, Quintero, en la V Región,
se detectó en octubre de 2006
que la norma de coliformes fecales
de 1.000 Nmp/100 ml llegó a 170.000 Nmp/100 ml,
es decir, 170 veces sobre lo permitido,
según constata la Superintendencia
de Servicios Sanitarios
en resolución del pasado 1 de octubre.

Lo más que se obtiene es imponer
unas multas de entre 5 a 15 millones de pesos
(US$10.000 a US$30.000)
monto absurdamente bajo
para la gravedad del problema
(y que además pagan
o dejan de percibir, al final de cuentas,
todos los chilenos
por el carácter estatal de estas empresas).

Lo ocurrido con Celco (Planta de Celulosa privada)
en Valdivia, o Codelco (Corporación Nacional del Cobre),
no es un incidente nuevo para Chile ni para Codelco,
y no se requiere de mucha perspicacia
para percatarse de que se trata
de la punta del iceberg del problema
y habla de cómo falla
toda la institucionalidad nacional al respecto,
desde la fiscalización oportuna
con sanciones efectivas, pero por sobre todo,
por la falta de cultura y conciencia ambiental
que no es un discurso ideológico histérico
que pretenda destruir todo el aparato productivo
sino que apunta a llamar la atención
acerca de factores clave que inciden
en la salud de la población y de nuestro
entorno natural, y que deben ser incorporados
a la ecuación costo-beneficio, para que el desarrollo
tenga alguna posiblilidad de sustentabilidad
en el mediano y largo plazo.

No basta que estas empresas
expongan lo que han realizado
para mejorar sus estándares ambientales,
si estos esfuerzos son tan insuficientes
y no siquiera se acercan a cumplir con la norma.

Rafael Rosende

Incomprensible

El relato de la historia y el destino del universo
es una rama de la literatura fantástica,
un género ideal para abarcar lo incomprensible.

Rafael Rosende

Tuesday, July 31, 2007

Raul Guenther

Com grande pesar soube somente hoje da tragédia que assolou o meu caro amigo Raul Guenther, de quem eu lembro pelo sorriso, a quem eu admirava por sua competência e ideais, como engenheiro, professor da UFSC, pela luta no PT e no Forum Catarinense de Ciência e Tecnologia. Que sua memória permaneça entre nós, que seu filho José Raul se recupere.

NotíciasTrânsito | 23/07/2007 19h57min
Duas pessoas morrem em acidente no trecho Sul da BR-101 Três veículos e onze passageiros foram envolvidos; duas pessoas estão em estado grave

Um acidente grave na BR-101, no trecho em duplicação, interrompeu a viagem de duas famílias. Três veículos e 11 pessoas foram envolvidas, com saldo de dois motoristas mortos e dois passageiros gravemente feridos.

A colisão frontal entre uma camionete D-20, placas de Joinville, e um veículo Toyota Corolla, de Florianópolis, ocorreu às 13h30min desta segunda-feira, em Araranguá, no Sul do Estado.

A tragédia ocasinou o congestionamento do tráfego em pelo menos cinco quilômetros nos dois sentidos da rodovia até as 16h. De acordo com os patrulheiros da Polícia Rodoviária Federal de Araranguá (PRF), a trágica colisão frontal ocorreu no KM 410, no Bairro Barranca, numa curva dois quilômetros distantes da ponte sobre o rio Araranguá.

O veículo Corsa Sedan, com placas de Turvo, seguia de Araranguá em direção a Criciúma. O motorista Éder Natanael Vieira, de 28 anos de idade, perdeu o controle da direção em razão de problemas mecânicos e invadiu a pista contrária, mas consegiu retornar para a pista e caiu num barranco, no acostamento.

Vieira estava acompanhado de um caroneiro, mas os dois saíram ilesos do acidente. Para tentar desviar do Corsa, o motorista do Corolla que seguia em direção ao Sul do Estado, Raul Guenther, 54 anos, bateu de frente contra uma camionete Chevrolet D-20, que seguia logo atrás do Corsa, e capotou na pista.
Além do motorista do Toyota, que morreu no local da tragédia, estavam no veículo o filho José Raul Guenther, de 16 anos - internado em estado grave na Unidade de Terapia Intensiva (UTI) do Hospiotal Regional de Araranguá - e a mulher Ariane Girondi, 55 anos, que sofreu lesões leves.

A família viajava a Porto Alegre (RS). Família retornava para casa Na camionete, havia seis pessoas da mesma família. Eles retornavam para casa, em Joinville. O motorista, Vagner Leal de Quadros, de 62 anos, recebeu atendimento no local do acidente, mas morreu a caminho do Hospital Regional de Ararnguá.

A caroneira, sua mulher, Lucimar Cruz de Quadros, 43 anos, fraturou o braço e passa bem. Ainda no veículo estavam o filho do casal, Vitor de Quadros, 12 anos, que sofreu ferimentos leves, e outros trê jovens, entre filhos e sobrinhos do casal, que nada sofreram.
DIÁRIO CATARINENSE

Caminhonete D-20, de Joinville, ficou destruída - Ulisses Job / Agência RBS
Caminhonete D-20, de Joinville, ficou destruída
Foto: Ulisses Job / Agência RBS


Monday, June 11, 2007

After a certain age years don't make much sense any more

Rafael Rosende has sent me by mail this comment. He has allowed me to post it here.

«After a certain age years don't make much sense any more.»


Fernando Deeke Sasse
Comment on his Blog,
Flooded Mind
-Thoughts and Questions about Minds,
Classical & Quantum Information Theory,
Special & General Relativity-


After certain age,
we began to perceive,
a perhaps fictitious sensation
that our planet is spinning faster
and that the annual period
of its orbit around the sun
is getting briefer as time
and life goes by.

Others, have a more pessimistic view:

Los años primero pasan, después pesan y al final pisan.
[Comentario de un cura, según leí por ahí hace bastante tiempo.]

We must stop rushing...
or as a journalist from Newsweek
wrote some time ago,
«Everything today happens faster,
including how fast we forget»

Citas rápidas de un libro que no he leído todavía
(solamente hojeado por encima)

E.M. Cioran, «El Ocaso del Pensamiento»
Tusquets Editores (Barcelona)


El hombre es el camino más corto entre la vida y la muerte

Sufrir es la manera de estar activo sin hacer nada.

La palidez es el color
que cobra el pensamiento
en el rostro humano.

Un hombre que practica
todo su vida la lucidez,
se convierte en
un clásico de la desesperanza.

La música es tiempo sonoro.

La infelicidad es el estado poético por excelencia.

Sólo como fuente de infelicidad
la mujer es revelación de lo absoluto.

¿Has visto cómo se les marcan
las venas a los glaciares?

Nada puede reducirse a la unidad.
El caos acecha al mundo en todos los rincones.

El amor nos muestra
hasta donde podemos estar enfermos
en los límites de la salud.

El estado amoroso
no es una intoxicación orgánica
sino metafísica.

Si el amor no fuera
la irresoluble mezcla
de crimen premeditado
e infinita delicadeza,
¡qué fácil sería reducirlo
a mera fórmula!

El amor no cabe en la vida.

La profundidad del amor
se mide por su potencial de soledad.

En Shakespeare hay tanto crimen y tanta poesía
que sus dramas parecen concebidos por una rosa demente.

El alma de una catedral gime
en el agotamiento vertical de la piedra.

La nostalgia de la muerte
eleva todo el universo al rango de la música.

La soledad no te enseña a estar solo, sino a ser único.

Hasta el hecho de beber agua es un acto religioso.

La desesperanza es la vitalidad de la Nada.

La palidez nos muestra hasta donde
el cuerpo puede entender el alma.

Un pensamiento seca mares
pero no puede enjugar una lágrima.

El vacío interior
es como una música sin sonidos,
una canción sin voz.

¿Será Dios algo distinto
a un intento de satisfacer
mi infinita necesidad de Música?

Cuando los ojos se me cierran
y se extienden mis límites
hasta los del mundo,
¿qué misterioso oído
me filtra en el horizonte
un coro de niños locos?

Un arquitecto desarraigado de la tierra
podria construir con nuestras amarguras
un monasterio en el cielo.

El espíritu florece sobre las ruinas de la vida.

Cuando llevas tanta música
en un mundo sin melodía.

La infelicidad no tiene sentido
en el universo de las palabras.

La eternidad no es otra cosa
que la carga de ausencia de tiempo.

¿Por qué las nubes flotan
más fácilmente en el cerebro que en el cielo?

La vida y yo somos dos líneas paralelas
que se encuentran en la muerte.

Un pensador que oyera pudrirse una idea...

La locura es la introducción de la esperanza en la lógica.

Si no hubiésemos tenido alma,
nos la habría creado la música.

Hace mucho
que ya no vivo en la muerte,
sino en su poesía.

Todo lo que no es felicidad es una falta de amor.

Thursday, March 29, 2007

Dirac and religion

S. Schweber wrote about Dirac and religion [1]:
“I do not know when Dirac became an atheist, but Heisenberg (1971) recalls that in 1927 during a discussion on religion among the younger members who were attending the Solvay Congress, the twenty-five year old Dirac asserted that "If we are honest--and scientists have to be--we must admit that religion is a jumble of false assertions, with no basis in reality. The very idea of God is a product of the human imagination .... I can't for the life of me see how the postulate of an Almighty God helps us in any way. What I do see is that this assumption leads to such unproductive questions as why God allows so much misery and injustice, the exploitation of the poor by the rich and all other horrors He might have prevented. If religion is still being taught, it is by no means because its ideas still convince us', but simply because some of us want to keep the lower classes quiet. Quiet people are much easier to govern than clamorous and dissatisfied ones. They are also easier to exploit .... Hence the close alliance between those two great public forces, the State and the Church." The ensuing heated discussion was capped by Pauli's observation that actually "our friend Dirac, too, has a religion, and its guiding principle is 'There is no God, and Dirac is His prophet."

It interesting to note that in our days it is religious fanaticism one of the biggest obstacles that USA faces in their endeavor to conquer the world.

[1] Les Houches , session XL ,1983
Relativity, Groupes et topologie II
Bryce S. DEWitt et Raymond Stora
Some chapters for a history of quantum field theory:1938-1952
S. S. Schweber , Brandeis University ,Waltham, MA 02254, USA

Tuesday, October 25, 2005

Complexity, Dissipation, Information and Organization

Charles Bennet in his paper [1] addresses the following questions belonging to both statistical mechanics an the theory of computation:
- What is the proper measure of intrinsic complexity to apply to states of a physical system?
- What role does thermodynamic irreversibility play in enabling systems to evolve spontaneously toward states of high complexity?

The paper is technical, but its first part is very helpful for the basic understanding of concepts like organization, complexity and information content.

A fundamental problem of statistical mechanics is why dissipative systems (those in which entropy is continually being produced and removed to the surroundings) tend to undergo “self-organization”, a spontaneous increase of complexity, of which the most extreme example is the origin and evolution of life. The converse principle, stating that nothing interesting is likely to happen in a system at thermal equilibrium, is called “heat death”.

One could try to use thermodynamic potentials to characterize complexity and organization but, I spite of the well known ability of dissipative systems to lower their entropy at the expense of their surroundings, organization cannot be directly identified with thermodynamic potentials such as entropy or free energy: the human body is intermediate in entropy between a crystal and a gas; and a bottle of sterile nutrient has higher free energy, but lower subjective organization, than the bacterial culture it would turn into if inoculated with a single bacterium. This difference in free energy means that, even without the seed bacterium the transformation from nutrients to bacteria (albeit an improbable case of spontaneously biogenesis) is still vastly more probable than the reverse transformation, from bacteria to sterile, high free-energy nutrients. Another example is the crystallization of a long-lived supersaturated solution: although crystallization without the catalytic assistance of a seed crystal may be so slow as to be unobservable in practice, it is not thermodynamically forbidden, and is, in fact, overwhelmingly more probable than the reverse process.

Subjective organization seems to obey a “slow growth law” which states that, except by a lucky accident, organization cannot increase quickly in any deterministic or probabilistic process, but it can increase slowly. It is this law which forbids sterile nutrient form turning into bacteria in the laboratory, but allows a similar transformation over geological time. If the slow growth law is to be obeyed, the rapid multiplication of bacteria after inoculation must not represent much increase in organization, beyond that already present in the seed bacterium. This means that subjective organization is not addictive: 1 bacterium contains much more organization that 0 bacteria, but 2 sibling bacteria contain about the same amount as 1.

The apparent non-additivity of “organization” suggest another definition for it, namely as information content. The information content of an object can be defined as the number of bits required to specify it uniquely. For example, two large message-like objects (e.g. DNA molecules), if they happen to be identical, do not together contain significantly more information than one alone. Different definitions of information content that may or may not be useful to define organization in biological molecules are developed in the article.

[1] C. H. Bennett "Information, Dissipation, and the Definition of Organization", in Emerging Syntheses in Science David Pines ed., Santa Fe Institute, pp 297-313 (1985), Addison-Wesley (Reading, Massachusetts 1987). Scanned PDF File

Monday, October 24, 2005

Landauer's Principle

IN 1961 Rolf Landauer (1927-1999) applied thermodynamic reasoning to digital computers, providing a bridge between information theory and physics. There are many publications regarding this subject. Here I just want to present, according to [2], a simple and quick way to state Landauer’s principle, regarding classical (non-quantum) information in classical systems.

In his original paper [1] Landauer had the important insight that there is a fundamental asymmetry in the way Nature allows us to process information. Copying classical information can be done reversibly and without wasting any energy, but when information is erased there is always an energy cost of kT ln2 per classical bit to be paid. For example, as shown in fig. 1, we can encode one bit of information in a binary device composed of a box with a partition.
Fig1 We erase the information of the position of the atom. First we extract the wall separating the two halves of the box. Then we use a piston to shift the atom to the left side of the box. After the procedure, the atom is on the lefthand side of the box irrespective of its intial state. Note that the procedure has to work irrespective of whether the atom is initially on the right (a) or on the left side (b).

The box is filled with a one molecule gas that can be on either side of the partition, but we do not know which one. We assume that we erase the bit of information encoded in the position of the molecule by extracting the partition and compressing the molecule in the right part of the box irrespective of where it was before. We say that information has been erased during the compression because we will never find out where the molecule was originally. Any binary message encoded is lost! The physical result of the compression is a decrease in the thermodynamical entropy of the gas by kln2. The minimum work that we need to do on the box is kT ln2, if the compression is isothermal and quasi-static. Furthermore an amount of heat equal to kT ln2 is dumped in the environment at the end of the process. Landauer’s conjectured that this energy/entropy cost cannot be reduced below this limit irrespective of how the information is encoded and subsequently erased – it is a fundamental limit.

It can be shown that Landauer’s principle can be deduced from the second law of thermodynamics and is in fact equivalent to it [3]. Earman and Norton have argued that since it is not independent of the Second Law, it is either unnecessary or insufficient as an exorcism of Maxwell’s Demon. A response to this objection was given by Bennet [5].

In practice, almost all data processing is done on macroscopic apparatus, dissipating macroscopic amounts of energy far in excess of what would be required by Landauer’s principle. Nevertheless, some stages of biomolecular information processing, such as transcription of DNA to RNA, appear to be accomplished by chemical reactions that are is reversible not only in principle but in practice.

[1] R. Landauer, Irreversibility and heat generation in the computing process. IBM J. Res. Dev. 5, (1961) pp.183-191 [pdf].

[2] M. B. Plenio and V. Vitelli, The physics of forgetting: Landauer’s erasure principle and information theory, arXiv:quant-ph/0103108 v1 19 Mar 2001.

[3] B. Schumacher, Relative entropy in quantum information theory, arXiv:quant ph/0004045 10 Apr 2000.

[4] John Earman and J. D Norton, "Exorcist XIV: The Wrath of Maxwell's Demon." Studies in the History and Philosophy of Modern Physics, Part I "From Maxwell to Szilard" 29(1998), pp.435-471; Part II: "From Szilard to Landauer and Beyond," 30(1999), pp.1-40. Download Part I Download Part II.

[5] Charles H. Bennet, Notes on Landauer’s Principle, Reversible Computation, and Maxwell Demon, Studies in History and Philosophy of Modern Physics, 34, (2004) pp. 501-510, arXiv : physics/0210005 v2 9 Jan 2003.

Sunday, October 02, 2005

Daniel Dennet, Marvin Minsky and Consciousness

Two of my favorite thinkers are Daniel Dennet, and Marvin Minsky, mainly because of their great ideas about consciousness as expressed, for example, in the books [1] and [2].

How life appeared on Earth is not exactly known, but we have a reasonable pretty good general idea, provided by chemistry. Existence also has some explanations, based, for example on Barrow and Carter’s Anthropic Principle or on the multiverse theory of Tegmark. On the other hand, consciousness remains as deep mystery. Marvin Minsky and Daniel Dennet have given some light on the subject. According to Dennet, our powerful subjective impression that we are conscious of sensory perceptions in real time is actually an illusion. We don’t take the world in at a glance and keep a copy of it to compare to the next glance. We take in just a very limited amount of material, so things are not as they seem. For example, it is known that the order in which we perceive things is not always the order in which the sensory data arrives in the brain. We are not conscious of anything at precisely the time we imagine. What we experience is generated a little after the fact, as a result of a competition among multiple patterns of mental activity propagating within the brain. Awareness comprises a small fraction of those mental events whose influence will persist and so alters beliefs about what just happened. According to this view,
  • Consciousness is the product of a virtual machine running in the brain.

  • Consciousness and will are wholly due to material, which is designed by evolution (or people) to serve useful functions.
So, Dennet introduced what it seems to be a very useful concept: intentional stance. The key to understand behavior, human and otherwise, is adopting the “intentional stance”. Just as the best way of predicting a chess-playing computer next move is to – rather than try to study its circuitry – assume it “intends” to win, so the best way to predict the behavior of an animal is to suppose that it has beliefs and desires. Organisms can be understood as natural selection’s solutions to evolutionary problems.

[1] Daniel Dennet, Darwin's Dangerous Idea, Simon &Schuster, 1995.

[2] Marvin Minsky, The Society of Mind, Simon & Schuster, 1988.

Monday, September 26, 2005

Librarything

The suggestion given by Elio Gaspari, on his Sunday (09/25/2005) column in “O  Globo”, to use librarything (http://www.librarything.com) to catalog a personal library was great. The system created by Tim Spalding could be viewed as  as an orkut with brains, but it is much more than that. I am producing my catalog (http://www.librarything.com/profile.php?view=fsasse), transferring data from my (incomplete) bibtex datafile (http://members.fortunecity.es/lamb/books1.html).  The only problem is that many of my technical books  are in Portuguese or were published by the deceased Mir, and therefore don’t have entries in the Library of Congress or Amazon. Their data must be entered manually.

Thursday, September 22, 2005

About Sim Worlds

Some questions about life in a sim world:

  • Is it possible for a sim to realize that he is living in a virtual world [1]? Could he do that by verifying that the physics laws of his world do allow a mathematically elegant or coherent formulation ?

  • Is it possible for a sim to realize that his world doesn’t conform with the anthropic principle¹ [2] ?

  • Is it possible to build a virtual world inhabited by intelligent sims, who perceive their world in such a way that they can model it by a physical theory completely different from ours ?

[1] Hans Moravec, Pigs in Cyberspace, 1992, http://www.cni.org/pub/LITA/Think/Moravec.html
[2] John Barrow and Frank J. Tipler, The Anthropic Cosmological Principle, Oxford University Press, Oxford, 1988.

¹ The Anthropic Principle was proposed in Poland in 1973, during a special two-week series of synopsia commemorating Copernicus’s 500th birthday. It was proposed by Brandon Carter, who, on Copernicus’s birthday, had the audacity to proclaim that humanity did indeed hold a special place in the Universe, an assertion that is the exact opposite of Copernicus’s now universally accepted theory. In his contribution "Large Number Coincidences and the Anthropic Principle in Cosmology" Carter remarks: "Although our situation is not necessarily central, it is inevitably privileged to some extent" (IAUS 63 (1974) 291).
Proponents of the anthropic principle suggest that we live in a fine-tuned universe, i.e. a universe that appears to be "fine-tuned" to allow the existence of life as we know it. If any of the basic physical constants were different, then life as we know it would not be possible. Papers have been written arguing that the anthropic principle would explain the physical constants such as the fine structure constant, the number of dimensions in the universe, and the (an arbitrary constant in Einstein’s equations of general relativity theory) cosmological constant. The two main forms of the anthropic principle are [2]:
Weak anthropic principle (WAP): "The observed values of all physical and cosmological quantities are not equally probable but they take on values restricted by the requirement that there exist sites where carbon-based life can evolve and by the requirements that the Universe be old enough for it to have already done so."
Strong anthropic principle (SAP): "The Universe must have those properties which allow life to develop within it at some stage in its history."

Tuesday, September 20, 2005

Word Processing

John D. Barrow in p. 13 of  [1], writes about the influence of computers in our life. He says that even a mundane  computer-based activity, like word processing, has done more than just making writing and editing more efficient: it has altered  the way in which writers think. They used to write because they had something to say; now they write in order to discover if they have something to say. I confess  that I am still thinking if this is really true and, if so, if this contributes to production of  better or worse literature… I suspect that the relations are more intrincate. For sure, the amount of  garbage in our bookstores is growing.
[1] John D. Barrow, Impossibility, Oxford University Press, 1998.

Monday, September 19, 2005

Silicon Heaven

From Red Dwarf quote generator:

" Causality? Well, OK, you know, one event causes another, OK, but sometimes, you just gotta say, the laws of time and space? Who gives a smeg!' " - Kryten, Tikka to Ride

" No silicon heaven? Preposterous! Where would all the calculators go? " - Kryten, The Last Day

Thursday, September 15, 2005

The Power of Quantum Computers and Entanglement

In the Section 4.2, entitled Quantum Algorithms of [1], R. Jozsa argues that the property of entanglement is the key property for the power of quantum computers. In quantum theory it is possible to represent a superposition of 2^n states using n 2-level systems, because of the phenomenon of entanglement. A general superposition of this kind requires only a linear amount of physical resources to represent it, since at most each of the n systems needs to be separately excited. Hence, although superposition occurs in classical systems, the phenomenon of quantum entanglement leads to an exponential saving of physical resources needed to represent large superpositions.

“Natural quantum physical evolution may be thought as a processing of quantum information. Thus the viewpoint of computational complexity reveals a new bizarre distinction between classical and quantum physics: to perform natural quantum physical evolution Nature must process vasts amounts of information at a rate tha cannot be matched in real time by any classical means, yet at the same time, most of this processed information is kept hidden from us. However, it is important to point out that the inherent inaccessibility of quantum information does not cancel out the possibility of exploiting this massive information capability for useful computational purposes. Indeed, small amounts of information may be extracted about the overall identity of the final state which would still require an exponential effort to obtain by classical means.’’

[1] Dirk Bouwmeester, Artur Ekert and Anton Zeilinger (Eds.) The Physics of Quantum Information, Springer, 2001.

Friday, August 26, 2005

Quantum Artificial Intelligence


I have started reading the book The Quest for the Quantum Computer, by Julian Brown, and so far it seems to be very good. The author is not a professional scientist but writes with scientific precision, brings quality information and doesn't treat the reader like an idiot, a very irritating practice in this kind of literature (Mickey Mouse accounts of science) . A good science divulgation text can entertain even specialists on the subject. The first chapter starts by describing the nonusual (for non-scientists) daily life of David Deutsch. This brilliant physicist is an example of what Ahtekhar meant in his quotation of the preceeding post. In the 80’s David Deutsch dared to try solving problems that great physicists, mathematicians and computer scientists would consider either too difficult or nonsensical. One of his early ideas was about the possibility of building an artificial mind working at a quantum level. Such mind would then be able to tell us if there are many universes bifurcating at each moment or not. I wonder if such thing would be possible, since our own brains cannot figure out how they work. A very convincing way of explaining many aspects of our brains uses Marvin Minsky’s concept of the society of mind. A manager doesn’t need to know the inner workings of each machine under his supervision. It would be possible to conceive a mind that could understand and be aware of all its levels ? The drawing above was made by Stanislaw Lem (A depressed, hunchbacked robot).

Ashtekar I

There is a kind
of innocent arrogance
when one is young,
about working
on the most difficult problems.

Abhay Ashtekar

Thursday, August 25, 2005

The Starting Point

I want to express here some of my thoughts and ignorance mainly about Science, biased to Physics. It is safer to write here than in a notebook and I also need to show something from myself to others, specially friends and family. By writing these lines I want to preserve a bit of my present and past so, maybe not everything will be forgotten. I guess that new uses for this blog may show up along the way.

The name used in this blog address was inspired by the recollections of the great times I have spent with my friend Vinicius Moll, the real Moonlit Knight.