Angel "Java" Lopez en Blog

Ciencia


Publicado el 9 de Agosto, 2020, 19:53

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Marcel Grossmann and his contribution to the general theory of relativity
http://inspirehep.net/record/1269392/plots?ln=en

History: Einstein was no lone genius
https://www.nature.com/news/history-einstein-was-no-lone-genius-1.18793

Einstein's 1912-1913 struggles with Gravitation Theory: Importance of Static Gravitational Fields Theory
https://arxiv.org/ftp/arxiv/papers/1202/1202.2791.pdf

General Covariance
https://en.wikipedia.org/wiki/General_covariance

Caminos cuánticos fuertemente correlacionados simulados usando 12 cúbits
https://francis.naukas.com/2019/05/27/caminos-cuanticos-fuertemente-correlacionados-simulados-usando-12-cubits/

Una colisión con un planeta enano para explicar el misterio de la cara oculta de la Luna
https://danielmarin.naukas.com/2019/05/27/una-colision-con-un-planeta-enano-para-explicar-el-misterio-de-la-cara-oculta-de-la-luna/

Cuantizando el mundo - Alberto Aparici | OGMIOS 2019
https://www.youtube.com/watch?v=1nwe0TlB95Q

¿Qué hay dentro de un agujero negro?
http://cienciaclip.naukas.com/video/dentro-agujero-negro/

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Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 8 de Agosto, 2020, 20:50

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The Jaguar and the Fox
https://www.theatlantic.com/magazine/archive/2000/07/the-jaguar-and-the-fox/378264/
Hard as he tried, Murray Gell-Mann could never make himself into a legend like his rakish colleague and collaborator, Richard Feynman -- even if he was probably the greater physicist

Big Bounce Simulations Challenge the Big Bang
https://www.quantamagazine.org/big-bounce-simulations-challenge-the-big-bang-20200804/

Ask Ethan: What Is The Fine Structure Constant And Why Does It Matter?
https://www.forbes.com/sites/startswithabang/2019/05/25/ask-ethan-what-is-the-fine-structure-constant-and-why-does-it-matter

COVID-19 Is Raging. How Safe Is Your Backyard Party?
https://www.quantamagazine.org/covid-19-is-raging-how-safe-is-your-backyard-party-20200806/

Quanta Magazine Topics
https://www.quantamagazine.org/topics

Extra DNA May Make Unlikely Hybrid Fish Possible
https://www.quantamagazine.org/extra-dna-may-make-unlikely-hybrid-fish-possible-20200805/

Creating Neanderthal 'Mini-Brains' With Ancient DNA, CRISPR
http://discovermagazine.com/2019/january/ancient-brains#.XOqYoEW8B4M.twitter

Pay attention, Albert Einstein!
https://www.newscientist.com/article/mg13718543-900-pay-attention-albert-einstein/

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Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 2 de Agosto, 2020, 10:06

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Murray Gell-Mann Building Dedication Ceremony
https://www.youtube.com/watch?v=8bOl0i1OORA&feature=youtu.be

La geometría del potencial que confina un electrón en un punto cuántico
https://francis.naukas.com/2019/05/25/l
a-geometria-del-potencial-que-confina-un-electron-en-un-punto-cuantico/

How to Design (or at Least Model) Mixed Dog Breeds
https://www.quantamagazine.org/puzzle-answers-about-sexual-inheritance-and-mixed-dog-breeds-20200731/

LOG#245. What is fundamental?
http://www.thespectrumofriemannium.com/2020/07/26/log245-what-is-fundamental/

An Alternative to Dark Matter Passes Critical Test
https://www.quantamagazine.org/modified-gravity-theory-passes-a-critical-test-20200728/

An integrated encyclopedia of DNA elements in the human genome
https://www.nature.com/articles/nature11247

Why Are Plants Green? To Reduce the Noise in Photosynthesis.
https://www.quantamagazine.org/why-are-plants-green-to-reduce-the-noise-in-photosynthesis-20200730

Our Genes May Explain Severity of COVID-19 and Other Infections
https://www.quantamagazine.org/our-genes-may-explain-severity-of-covid-19-and-other-infections-20200727/

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 26 de Julio, 2020, 14:13

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The Brain Reshapes Our Malleable Senses to Fit the World
https://www.quantamagazine.org/the-brain-reshapes-our-malleable-senses-to-fit-the-world-20200324

He Found "Islands of Fertility" Beneath Antarctica"s Ice
https://www.quantamagazine.org/john-priscu-finds-life-in-antarcticas-frozen-lakes-20200720/

Viruses Can Scatter Their Genes Among Cells and Reassemble
https://www.quantamagazine.org/viruses-can-scatter-their-genes-among-cells-and-reassemble-20190521

Sometimes, physics is pretty darn cool
https://www.instagram.com/p/B1bOFbfgaYx/?utm_source=ig_web_copy_link

Jupiter"s Iconic Red Spot is Shrinking, What Could Happen Next?
https://www.youtube.com/watch?v=fW-YrNaxJFU

A history of the electron: JJ and GP Thomson
https://www.chemistryworld.com/culture/a-history-of-the-electron-jj-and-gp-thomson/6090.article

Reseña: «Mi vida en la ciencia» de Sydney Brenner
https://francis.naukas.com/2019/05/19/resena-mi-vida-en-la-ciencia-de-sydney-brenner/

We're sorry to announce the passing of @NobelPrize Laureate and complexity giant Murray Gell-Mann, one of the 20th Century's greatest physicists – pioneer, SFI co-founder, prophet of the quark
https://twitter.com/sfiscience/status/1131969981686665216

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Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 19 de Julio, 2020, 15:16

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A Gentle Kiss: How the Kuiper Belt Object Ultima Thule Was Born
https://www.space.com/ultima-thule-birth-new-horizons-first-science.html

El 11 de diciembre de 1998, un cohete despegaba de Cabo Cañaveral. A bordo viajaba el Mars Climate Orbiter, un satélite meteorológico con destino a Marte.
https://twitter.com/ValeArvejita/status/946395150238015488

El primer candidato a estrella de neutrones producto de la fusión de dos enanas blancas
https://francis.naukas.com/2019/05/21/el-primer-candidato-a-estrella-de-neutrones-producto-de-la-fusion-de-dos-enanas-blancas/

How Your Heart Influences What You Perceive and Fear
https://www.quantamagazine.org/how-your-heart-influences-what-you-perceive-and-fear-20200706/

Flatten the Curve of Armchair Epidemiology
https://medium.com/@noahhaber/flatten-the-curve-of-armchair-epidemiology-9aa8cf92d652

Nature Versus Nurture? Add "Noise" to the Debate.
https://www.quantamagazine.org/nature-versus-nurture-add-noise-to-the-debate-20200323

Boris Johnson: why you must stay at home
https://www.spectator.co.uk/article/full-text-boris-johnson-announces-lockdown

Coronavirus Datos de España
https://twitter.com/jnikitas/status/1242494861984530432

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Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 18 de Julio, 2020, 17:08

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Bubonic Plague Strikes In Mongolia: Why Is It Still A Threat?
https://www.npr.org/sections/goatsandsoda/2019/05/07/721167330/bubonic-plague-strikes-in-mongolia-why-is-it-still-a-threat

The Scientist Leading the World"s Aurora Hunters
https://www.quantamagazine.org/liz-macdonald-leads-the-worlds-aurora-hunters-20200709/

We need to talk about this Hydroxychloroquine + Azithromycin thing
https://twitter.com/jpogue1/status/1241138975802359813

Why Is Glass Rigid? Signs of Its Secret Structure Emerge
https://www.quantamagazine.org/why-is-glass-rigid-signs-of-its-secret-structure-emerge-20200707/

Spotting Quantum Black Holes in the Lab
https://www.quantamagazine.org/john-preskill-quantum-computing-may-help-us-study-quantum-gravity-20200715/

A Paradox of Parasite Prolonging the Life of Its Host. Pearl Mussel Can Disable the Accelerated Senescence Program in Salmon
https://link.springer.com/article/10.1007/s10525-005-0112-4

Why the Tiny Weight of Empty Space Is Such a Huge Mystery
https://www.quantamagazine.org/why-the-dark-energy-problem-spawned-the-multiverse-hypothesis-20180312/

Willem Einthoven (1860-1927)
https://www.historiadelamedicina.org/einthoven.html

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Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 10 de Julio, 2020, 13:47

Un tema que tengo pendiente de estudiar con cierta profundidad en física, es el de las teorías de campos. Debería comenzar con alguna teoría clásica, como el elctromagnetismo de Maxwell. Pero no hay que olvidarse que los campos se fueron extendiendo hasta llegar de uso prácticamente indispensable en física cuántica. Yq estuve escribiendo sobre las causas de esa extensión en la serie de posts La necesidad de una teoría cuántica de campos. Uno de los puntos tratados ahí fue que no hay un claro predominio epistemológico (podríamos decir) entre campos y partículas, y que los campos cuánticos justamente se cuantifican, llegando a expresar partículas como campos.

En estos días leo el magistral libro de Steven Weinberg: "Quantum Theory of Fields, Fundations, Volume I":

I have tried in this book to present the quantum theory of fields in a logical manner, emphasizing the deductive trail that ascends from the physical principles of special relativity and quantum mechanics. This approach necessarily draws me away from the order in which the subject in fact developed. To take one example, it is historically correct that quantum field theory grew in part out of a study of relativistic wave equations, including the Maxwell, Klein-Gordon, and Dirac equations. For this reason it is natural that courses and treatises on quantum field theory introduce these wave equations early, and give them great weight. Nevertheless, it has long seemed to me that a much better starting point is Wigner's definition of particles as representations of the inhomogeneous Lorentz group, even though this work was not published until 1939 and did not have a great impact for many years after. In this book we start with particles and get to the wave equations later.

Recuerdo vagamente estas ideas de Wigner: pero en general, son ideas que no se tratan en los libros clásicos de estudio (en carreras de ingeniería, por ejemplo) sobre física cuántica. Muchas veces los textos se concentran en el desarrollo de la MECANICA cuántica, desde Rutherford y Bohr, hasta de Broglie, Heisenberg, Schrodinger, Born, Jordan y Dirac. Prácticamente no se trata en esos casos de las teorías cuánticas de campos, salvo alguna mención esporádica. Y entonces, Wigner pasa desapercibido (de paso, Dirac se casó con la hermana de Wigner, eran cuñados). El tema a estudiar está tratado someramente en el artículo de la Wikipedia:

Particle physics and representation theory

En este blog, comenzó a aparecer el tema en la serie

Teoría de Grupos y Partículas Elementales

Ver también:

The 'Useless' Perspective That Transformed Mathematics sobre teoría de la representación
Los conceptos de campo, partícula, partícula virtual y vacío donde se mencionan representaciones lineales y simetrías

Sirva esta nota como recordatorio para estudiar este intesante tema.

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
https://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 9 de Julio, 2020, 15:04

El teorema de Noether, probado en 1915, publicado en 1918 junto con otro teorema, tiene un cualidad: consigue aunar distintos aspectos de la matemática y de la física, de los siglos XIX y XX, de una forma tan particular, que su estudio termina derivando en la comprensión de otros temas, desde teorías de relatividad a cuántica, desde campos hasta teorías gauge, y así.

De esta forma, su estudio es como una excusa para sumergirse en funciones, funcionales, lagrangianos, hamiltonianos, acciones, principio de minima acción, corrientes conservadas. Quería compartir en esta serie de posts algunas notas sobre el tema.

También espero poder compartir notas biográficas sobre Emmy Noether, que tanto hizo por el avance de las matemáticas abstractas (desde teoría de invariantes, a anillos e ideales). Siendo mujer, entre los siglos XIX y XX, no le fue fácil integrarse al mundo académico, pero hoy es reconocida no solo por el teorema que nos ocupa, sino por sus avances en matemáticas, especialmente en algebra conmutativa.

Mi primera referencia para compartir, es el libro "Emmy Noether's Wonderful Theorem" de Dwight E, Neuensshwander. El autor describe al principio un panorama del libro, de los temas que trata. Y una de los más interesantes aportes iniciales, es dar una lista de preguntas primarias:

What is "symmetry"
What is "invariance"
What are "conservation laws"
Who was "Noether" of Noether"s theorem?
How are symmetry, invariance, and conservation laws related?
What are Lagrangians and Hamiltonians? Which is more
fundamental?
What are generalized coordinates and their velocities?
What are "canonically conjugate" variables?
What are continuous symmetries?
What are discrete symmetries?
What are "tensors"?

Luego añade preguntas auxiliaries

What is "gauge invariance"
What is "minimal coupling"
What are "covariant derivatives"
What is the role of Hamilton—]acobi theory?
What is the "]acobian" of a transformation?
What is "phase space"? Why does anyone care?
Why are complex variables used to describe wave functions?
Why is the Lagrangian for mechanics kinetics minus potential energy?
What are "unitarity" and "Hermitian" operators? Why do we need them?
Why does Noether"s theorem consider only infinitesimal transformations?
Where does Hamilton"s principle come from? Is it related to Fermat"s principle?
Why do the Lagrangians of complex scalar fields drop the factor of 1/2 that appears with real scalar fields?
Why do we need two kinds of vector in spacetime, some with
upper indices and some with lower indices?
What are "equations of continuity" and how do they describe
conservation locally?
What are the symmetry groups SU(N) and why are they used?
How can "space inversion" be relevant to the real world?
Are positrons really electrons going backward in time?

Ya solamente leyendo estas preguntas, temenos una idea de lo profundo que pueden ser los temas que abarca tratar de comprender estos teoremas de Noether. Notablemente, la fama del teorema se acrecentó con el tiempo: al comienzo, solo captó la atención de especialistas, como el propio Einstein. Fue con los años, con la aparición de nuevas teorías de campos, más allá del electromagnetismo clásico, que los aportes de Emmy Noether cobraron mayor difusion e importancia.

Algunos post relacionados:

Notas sobre Lagrangianos y Hamiltonianos (serie)
Simetría, primeros pasos
Ideales en Anillos

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Angel "Java" Lopez
http://www.ajlopez.com
https://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 5 de Julio, 2020, 12:35

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Australopithecus africanus
https://twitter.com/cepitadenaranja/status/1242592257917833223

Machine Learning Takes On Antibiotic Resistance
https://www.quantamagazine.org/machine-learning-takes-on-antibiotic-resistance-20200309/

Black, Hot Ice May Be Nature"s Most Common Form of Water
https://www.quantamagazine.org/black-hot-superionic-ice-may-be-natures-most-common-form-of-water-20190508/

Ventilator Project Update: March 21th, 2020
https://medium.com/@brucefenton/ventilator-project-update-march-21th-2020-bd2ef9d587e0

The British govt is saying let the virus spread so 60% of Brits become infected and herd immunity is reached
https://twitter.com/DoctorYasmin/status/1238815504669671429

Alibaba"s new AI system can detect coronavirus in seconds with 96% accuracy
https://thenextweb.com/neural/2020/03/02/alibabas-new-ai-system-can-detect-coronavirus-in-seconds-with-96-accuracy/

When Good Scientists Go Bad
https://thenib.com/when-good-scientists-go-bad

Memes, Genes, and Sex Differences—An Interview with Dr. Steve Stewart-Williams
https://quillette.com/2019/05/14/memes-genes-and-sex-differences-an-interview-with-dr-steve-stewart-williams/

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 4 de Julio, 2020, 13:00

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Cuestión de tamaño: por qué no es buena idea fabricar mascarillas caseras
https://twitter.com/deborahciencia/status/1243115286670303234

Cosmic Rays May Explain Life"s Bias for Right-Handed DNA
https://www.quantamagazine.org/cosmic-rays-may-explain-lifes-bias-for-right-handed-dna-20200629/

Imperial College report on COVID-19
https://twitter.com/jeremycyoung/status/1239975682643357696

What Is the Geometry of the Universe?
https://www.quantamagazine.org/what-is-the-geometry-of-the-universe-20200316/

"Knitting Is Coding" and Yarn Is Programmable in This Physics Lab
https://www.nytimes.com/2019/05/17/science/math-physics-knitting-matsumoto.html

Scientists Have Confirmed a New DNA Structure Inside Human Cells
https://www.sciencealert.com/scientists-have-confirmed-a-new-dna-structure-inside-living-cells-i-motif-intercalated

Kinds of Ice
http://math.ucr.edu/home/baez/diary/november_2015.html#november_10

Coronavirus: ¿aumentar los tests es la receta para moderar el derrumbe de la economía?
https://www.clarin.com/economia/coronavirus-aumentar-tests-receta-economia-derrumbe-_0_S9MG14gff.html

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 28 de Junio, 2020, 13:00

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Blaschko's lines
https://en.wikipedia.org/wiki/Blaschko%27s_lines

The (but I"m Not a) Crackpot Style Guide
https://4gravitons.com/2016/07/01/the-but-im-not-a-crackpot-style-guide/

The mystery of the true coronavirus death rate
https://www.ft.com/content/f3796baf-e4f0-4862-8887-d09c7f706553

New physics discovery from the Microsoft Quantum team: topology with a twist
https://cloudblogs.microsoft.com/quantum/2020/03/27/new-physics-discovery-microsoft-quantum-topology-with-a-twist/

Viruses Can Scatter Their Genes Among Cells and Reassemble
https://www.quantamagazine.org/viruses-can-scatter-their-genes-among-cells-and-reassemble-20190521/

Impact of non-pharmaceutical interventions (NPIs) to reduce COVID19 mortality and healthcare demand
https://www.imperial.ac.uk/media/imperial-college/medicine/sph/ide/gida-fellowships/Imperial-College-COVID19-NPI-modelling-16-03-2020.pdf

Un informe advierte de que las medidas de distanciamiento social podrían ser necesarias hasta 18 meses
https://elpais.com/ciencia/2020-03-17/un-informe-advierte-de-que-las-medidas-de-distanciamiento-social-podrian-ser-necesarias-hasta-18-meses.html

Method of estimating the number of infected people from the number of deaths
https://twitter.com/wtgowers/status/1242823142088851456

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 27 de Junio, 2020, 13:06

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John Hopkins Coronavirus
https://coronavirus.jhu.edu/map.html

A multiplanet system of super-Earths orbiting the brightest red dwarf star GJ 887
https://science.sciencemag.org/content/368/6498/1477

Stem Cells Remember Tissues" Past Injuries
https://www.quantamagazine.org/stem-cells-remember-tissues-past-injuries-20181112/

Coronavirus: cómo funcionan los respiradores y por qué la desesperada carrera por fabricar más es clave en la batalla contra covid-19
https://www.bbc.com/mundo/noticias-52060716

Respiratory virus shedding in exhaled breath and efficacy of face masks
https://www.nature.com/articles/s41591-020-0843-2

Astrophysics Signal Does What The LHC Cannot: Constrain Quantum Gravity And String Theory
https://www.forbes.com/sites/startswithabang/2020/04/03/astrophysics-signal-does-what-the-lhc-cannot-constrain-quantum-gravity-and-string-theory/#695ed2252507

The proximal origin of SARS-CoV-2
https://www.nature.com/articles/s41591-020-0820-9#ref-CR20
https://twitter.com/pmarsupia/status/1246891625630048256

The outbreak that invented intensive care
https://www.nature.com/articles/d41586-020-01019-y

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 21 de Junio, 2020, 13:36

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Males Are the Taller Sex. Estrogen, Not Fights for Mates, May Be Why.
https://www.quantamagazine.org/men-are-the-taller-sex-estrogen-not-fights-for-mates-may-be-why-20200608

Sorry, Astronomers: Practically All Of The Universe's Matter Is Still Missing
https://www.forbes.com/sites/startswithabang/2020/06/04/sorry-astronomers-practically-all-of-the-universes-matter-is-still-missing/#4c22e6393942

"It opens up a whole new universe": Revolutionary microscopy technique sees individual atoms for first time
https://www.nature.com/articles/d41586-020-01658-1

COVID-19 Projections
https://covid19.healthdata.org/projections?sfns=mo

Neil Ferguson on Covid
https://twitter.com/neil_ferguson/status/1243294815200124928

The Environment and Disease: Association or Causation?
https://fermatslibrary.com/s/the-environment-and-disease-association-or-causation

Solution: "Is It Turtles All the Way Down?"
https://www.quantamagazine.org/puzzle-solution-is-it-turtles-all-the-way-down-20200327/

Milky Way Dark Matter Signals in Doubt after Controversial New Papers
https://www.scientificamerican.com/article/milky-way-dark-matter-signals-in-doubt-after-controversial-new-papers/

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 20 de Junio, 2020, 12:22

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Aniversario de Alan Turing
https://www.microsiervos.com/archivo/ordenadores/aniversario-de-alan-turing.html

Why Gravity Is Not Like the Other Forces
https://www.quantamagazine.org/why-gravity-is-not-like-the-other-forces-20200615/

Beth nació en 1941 en Brooklyn. Tres meses antes de la fecha prevista. La única opción sería llevarla al Luna Park.
https://twitter.com/ValeArvejita/status/1273401243898195968

The Trouble with Counting Aliens
https://www.wired.com/story/the-trouble-with-counting-aliens/

How to Breed a Pomsky and Other Questions About Dogs and Sex
https://www.quantamagazine.org/how-to-breed-a-pomsky-and-other-questions-about-dogs-and-sex-20200618/

Literature Search, Inspire, Most Cited
https://inspirehep.net/literature?sort=mostcited&size=25&page=1&q=topcite%201000%2B

A Model of Leptons
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.19.1264

The Large N Limit of Superconformal Field Theories and Supergravity
https://arxiv.org/abs/hep-th/9711200

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 15 de Junio, 2020, 11:14

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Is the alien chunk Oumuamua actually a hydrogen iceberg?
https://www.syfy.com/syfywire/is-the-alien-chunk-oumuamua-actually-a-hydrogen-iceberg

If A and B are observables AB is not, but it's made of i(AB-BA) and AB+BA
https://twitter.com/johncarlosbaez/status/1268571813170176000

Quantum Journal
https://quantum-journal.org/

A Surprise Discovery Points to the Source of Fast Radio Bursts
https://www.quantamagazine.org/a-surprise-discovery-shows-magnetars-create-fast-radio-bursts-20200611/

Graph-theoretic Simplification of Quantum Circuits with the ZX-calculus
https://quantum-journal.org/papers/q-2020-06-04-279/

La tabla periódica que conoces no es la única que existe
https://www.larazon.es/ciencia/20200605/buwlukrmhnb5nlsh22ojzohsqy.html

What Came Before the Big Bang?
https://www.discovermagazine.com/the-sciences/what-came-before-the-big-bang

Nuevos resultados que apoyan la conjetura AdS/CFT de Maldacena
https://francis.naukas.com/2020/06/07/nuevos-resultados-que-apoyan-la-conjetura-ads-cft-de-maldacena/

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 6 de Junio, 2020, 15:27

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My Quantum Experiment
https://blogs.scientificamerican.com/cross-check/my-quantum-experiment/

Why Sleep Deprivation Kills
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Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 31 de Mayo, 2020, 18:00

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Angel "Java" Lopez
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Angel "Java" Lopez
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Por ajlopez, en: Ciencia

Publicado el 23 de Mayo, 2020, 12:28

En estos días vuelvo a leer a Max Jammer, a quien mencioné en:

Uhlenbeck, Goudsmit y el spin del electron
Max Jammer y el Formalismo de la Mecánica Cuántica

Estoy leyendo su excelente libro "The Conceptual Development of Quantum Mechanics", edición 1966. Leo:

It is the purpose of this study to trace the conceptual development of  quantum mechanics from its inception to its formulation as a full-fledged theory of atomic physics, from its status as a rather doubtful ad hoc hypothesis to that of an imposing intellectual structure of great beauty.

Trata de la mecánica cuántica no relativista de una cantidad finite de grados de libertad, que abarca los primeros desarrollos exitoso, digamos, hasta parte de la tercera década del siglo XX. Las primeras preguntas que nos aparecen son: ¿qué es el desarrollo conceptual? ¿es necesario en este tema?.

All the great theories in the history of physics—from Aristotelian mechanics and its medieval elaborations, through Newtonian dynamics with its Lagrangian or Hamiltonian modifications, to Maxwellian  electrodynamics and* Einsteinian relativity—have been subjected repeatedly to historico-critical investigations, and their conceptual foundations have been thoroughly analyzed. But no comprehensive scholarly study of the conceptual development of quantum mechanics has heretofore appeared. The popular or semiscientific publications available hardly skim the surface of the subject. And the few, though important, essays on the topic written by the originators of the theory themselves are mostly confined to a  particular aspect or to the defense of a specific philosophical position. The publication of a comprehensive and coherent analysis of the conceptual development of quantum mechanics, the only consistent theory of atomic processes, and hence a foundation of modern science, seems therefore to fill an important lacuna in the literature on the history and philosophy of physics.

Primero, es un libro sobre el desarrollo de las ideas. No es un libro de texto para APRENDER mecánica cuántica, sino para entender cómo se fue desarrollando. Por otro lado, no es un libro solamente con el desarrollo histórico: habrá ocasiones donde Jammer se concentra en el desarrollo de una idea, sin importar que ese desarrollo se superponga en años históricos con otro desarrollo de otra idea.

Such a study, however, should not be regarded as an end in itself. Never before has a theory been treated in so many excellent texts within so short a period of time. Since every additional text, as is natural in a developing branch of science, attempts to construct the theory on the basis of an ever more concise logical structure, the traditional texts presenting the material in the order of its historical development are gradually losing ground. Students, it is rightfully claimed, may be saved much trouble "if they are not led through all the historical pitfalls, and instead acquainted from the very beginning with concepts, such as the spin, that cannot be grasped except by quantum mechanical means." [cita 1] Admittedly, a good working knowledge, even a high standard of efficiency and competence in applying the theory to physical problems may be obtained by this method of instruction. But as long as it is true that "however far the phenomena transcend the scope of classical physical explanation, the account of all evidence must be expressed in classical terms," [cita 2] a profound comprehension of quantum mechanics requires more than a study of the subject in its shortest possible logical formulation. "It is impossible to understand the methods of modern quantum mechanics without a knowledge of the way in which the theory has been developing." [cita 3] Indeed, some knowledge of the dramatic struggle of ideas that preceded the formation of quantum  conceptions and of the intricate ways of reasoning that led to the generally accepted formulation of the theory is indispensable for a profound comprehension of its physical significance, for an intelligent appreciation of its philosophical implications, and even for an enlightened understanding of its logical structure. Duhem's statement "faire l'histoire d'un principe physique, c'est en meme temps en faire l'analyse logique" is particularly meaningful for the science of quantum mechanics.

Hoy aprendemos física clásica, digamos la mecánica newtoniana, sin estudiar ni su desarrollo histórico ni conceptual (¿cómo surgió el concepto de energía? ¿y el de momento angular?). Pero en cuántica, y en especial en mecánica cuántica, pasa que si bien se puede aprenderla sin necesitar de la historia o el desarrollo, sus conceptos, operaciones y formalismos son tan extraños a la intuición que para realmente comprenderla, atraparla en su esencia, puede que no haya otro camino que el emprendido por Jammer: el desarrollo de las ideas, para explicar fenómenos que no cuajan en el marco "clásico". Es cierto que hay muy buenos libros para comenzar a entender la mecánica cuántica (y luego la física cuántica) desde algunos principios, sin tener que seguir todo el desarrollo ni histórico ni conceptual. Pero es como que se pierde algo. Un excelente libro que recuerdo ahora, que sigue un desarrollo histórico, más que conceptual, es el Física Cuántica, de Eisberg y Resnick, que era un clásico en mis días de estudiante universitario.

La cita 1 es F.A.Kaempffer, Concepts in Quantum Mechanics. La cita 2 es de Niels Bohr, "Discussion with Einstein on epistemological problems in atomic physics". La cita 3 es A.March, Quantum Mechanics of Particles and Wave Fields.

Seguiré citando y comentando algunos temas de este libro. Es interesante, por ejemplo, cómo plantea que los desarrollos de Jordan y de Dirac, a partir de 1925, son como un contrapunto: mientras el primero se concentra en teorías de campo, el segundo prefirió una vision desde el modelo de partículas.

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
https://twitter.com/ajlopez

Por ajlopez, en: Ciencia

Publicado el 22 de Marzo, 2020, 13:00

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Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
http://twitter.com/ajlopez

Por ajlopez, en: Ciencia

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