John Archibald Wheeler murió el año pasado mientras se celebraba en Alemania el “Quantum Gravity: challenges and perspectives” y la revista General Relativity and Gravitation ha decidido dedicarle un número especial a la gravedad cuántica en su honor con los artículos presentados en dicho evento (“Special issue on quantum gravity,” Volumen 41, Número 4, abril de 2009). Los artículos son de acceso gratuito (open access).

Disfrutarás conociendo el estado actual de la teoría de supercuerdas (”Superstring perturbation theory,” Ido Adam y “String theory as a theory of quantum gravity: a status report,” Matthias Blau and Stefan Theisen), de la cosmología basada en la gravedad cuántica de bucles (”Loop quantum cosmology: an overview,” Abhay Ashtekar), de la supergravedad y la teoría M (”Supergravity and M-theory,” Bernard de Wit and Maaike van Zalk), o de la correspondencia AdS/CFT para explicar la información almacenada en agujeros negros (”dark holes, AdS, and CFTs,” Donald Marolf). 

Obviamente los artículos están dirigidos a físicos, pero el nivel, aunque alto, es razonable para un físico teórico no especializado en gravedad cuántica. Que los disfrutéis.

Fue noticia en todos los medios. En este blog lo contamos en “El cronón – cuanto del tiempo – puede haber sido detectado por primera vez,” 12 Noviembre 2008 y llegó a portada en Menéame como “Un extraño ruido detectado por el GEO 600 podría probar que vivimos en un holograma,” 23 Febrero 2009. ¿Qué ha pasado con dicho ruido? El ruido ha desaparecido al utilizar un nuevo algoritmo de análisis de los datos. Todo indica que el ruido era un artefacto, un error sistemático. ¿Universo holográfico? Sí o no, depende de tus gustos teóricos, GEO 600 no tiene nada que decir al respecto. Ha pasado muchas veces y seguirá pasando, un error en la interpretación de los datos de un experimento lleva a una noticia en todos los medios. Cuando se descubre el error, casi nadie se entera. Casi nadie… nos lo cuenta Bee, ya emigrada a Suecia desde Canadá, en ”Update on the GEO 600 “Mystery Noise”,” Backreaction, Sept. 21, 2009, y para los amantes de las fórmulas matemáticas en Sabine Hossenfelder, “Antigravitation,” ArXiv, Submitted on 18 Sep 2009. Los alemanes de GEO 600 nos muestran el nuevo análisis del ruido en “The Sensitivity of GEO600.” 

Craig Hogan sugirió que el ruido de fondo en el detector de ondas gravitatorias GEO 600 era un efecto de la gravedad cuántica, de lo que llaman el universo holográfico. Hartmut Grote, de la colaboración GEO 600, nos cuenta el estado actual del asunto. ”En GEO 600 hemos demostrado que no hay ruido extraño alguno en la región entre 150 y 300 Hz, gracias al uso de un nuevo algoritmo para interpretar (readout) los datos experimentales. Todo indica que el ruido observado a principios de año era debido al algoritmo que se utilizaba entonces y no tiene nada que ver con el principio holográfico en física fundamental.”

Obviamente, Grote no le va a llevar la contra a Hogan, políticamente correcto como es. “La discusión de Hogan al respecto de que la sensibilidad de GEO 600 está limitada por el ruido holográfico sigue abierta. La colaboración GEO 600 no ha realizado un estudio específico al respecto. Lo único que se puede afirmar es que el ruido extraño observado en la región de 150-300Hz, ha desaparecido. La existencia de ruido holográfico por debajo de la sensibilidad actual de GEO 600 no se puede descartar. Futuras mejoras en la sensibilidad de GEO 600 podrían reafirmar o refutar las predicciones de Hogan.”

One more video of cathode rays. Alastair Wright has a number of great “old-school” science equipment videos.

Cathode ray tube emitting negatively charged electron and being deflected by a magnet. Nice nerdy video demo

see more at www.magnetportal.deI am still looking for a more standard Cathode Ray tube experiment similar to the one shown in your text, but this sure demonstrates the effect of magnets on a CRT.

Take Module #1 Test.  It is due at the beginning of class on the 28th.  Finish Experiment 1.2 report.  Read pp. 37-50.  I encourage you to do the On Your Own questions as you read.  You may get started on the Practice Problems.  They will be due the following week.

“พวกมึงใครใช้ให้เดินว่ะ เสือกซิบหาย” คำพูดนี้ถ้าไม่บอกไม่รู้ว่าผู้พูดเรียนจบป.ตรีมา แถมจบครูมาด้วย

เรื่องจริงที่ อาจารย์ฝ่ายปกครองของโรงเรียนแห่งหนึ่งในจังหวัดปัตตานี
ที่โรงเรียนอยู่ใกล้สะพานข้ามแม่น้ำปัตตานีอยู่ตรงข้ามที่ทำการเทศบาลฯ
อาจารย์ฝ่ายปกครองท่านนี้พูดผ่านไมค์ ใช่ครับเด็กทั้งโรงเรียนที่เข้าแถวอยู่ได้ยินหมด
คนที่ขับรถผ่านหน้าโรงเรียนได้ยินหมด ชาวบ้านที่อยู่รอบๆโรงเรียนได้ยินเช่นกัน

การพูดเช่นนี้ไม่ได้ครั้งแรกแน่ๆ สงสัยพูดมาตั้งแต่เริ่มหัดเดิน
เป็นครูแล้วมีสิทธิ์พูด ขึ้น “มึง”หรือ”กู” กับนักเรียนได้หรือ
เป็นผช.ฝ่ายปกครองแล้วพูดได้งั้นหรือ
ผู้บริหารโรงเรียนได้ยินแล้วทำเฉย หรือเพราะไม่เกี่ยวกับงบประมาณเลยเฉยๆไว้

ถ้าให้เหตุผลว่าต้องการให้เด็กเกรง มันมีหลายวิธีที่จะทำไม่ใช่ทำตัวเหมือนพวกที่ไม่มีการศึกษา หรือหลงยุคคิดว่าตอนนี้คือสมัยพ่อขุนรามคำแหง

เด็กจะดีจะร้าย พวกเขาก็คือเด็ก ปัญหาแนวร่วมที่ไม่จบไม่สิ้น ก็เพราะมีครูห่วยๆอย่างนี้ คอยแต่จะเบ่งกับเด็ก

ถามจริงว่าถ้า “เด็กนักเรียนเป็นลูกคุณ” คุณจะพูดอย่างนี้มั้ย
ถามจริงว่าถ้าเด็กนักเรียน ขึ้น”มึง”หรือ”กู”กับคุณบ้าง คุณจะรู้สึกอย่างไร

อำนาจ, สมอง, ความคิด หัดใช้ให้เป็นอย่างให้ใครต้องสอน เพราะมีตำแหน่งเป็นถึงผช.ฝ่ายปกครองคิดว่าคงไม่ได้มาเพราะเขียนเรียงความถึงนายกแน่ๆ
แต่เอ่…หรือว่าใช่

ไปดูหน้ากันเอาเองนะครับว่าสมควรที่จะใส่ชุดที่เรียกว่า “ข้าในฝ่าพระบาท”ได้หรือไม่

คลิ๊กเมนูทำเนียบผู้บริหาร

by Tom Pashby

“[T]he fact that the problem of the reduction of the wave mechanics-packet has remained baffling for so long, and that we lack any clue at present to its solution, seems to me no reason at all either for despair, or for embracing … glib and inadequate pseudo-solutions. Real problems are not always ripe for solution.” Howard Stein, ‘On the Present State of the Philosophy of Quantum Mathematics’ (1982)

“Information? Whose information? Information about what?” John S. Bell, ‘Against Measurement’ (1990)

This paper concerns Carlo Rovelli’s proposed solution to the measurement problem he calls Relational Quantum Mechanics (1996, 2005, 2007, 2008). Following Brown (2009) I distinguish between the interpretative and reconstructive projects Rovelli commences in (1996), and argue that his pursuit of the interpretative project alone since then indicates that he regards it as standing independently. This project amounts to an attempt to answer the question ‘What is quantum mechanics trying to tell us?’, rather than ‘Why the quantum?’.

I begin with an analysis of Rovelli’s argument for the radically relativist position he adopts which concerns what he calls `the third person problem’ i.e. the ‘Wigner’s friend’ paradox of Wigner (1961). I argue that even if we accept the very high value he places on definiteness, the radical conclusion (that there is no observer independent description of reality) does not follow due to the availability of a similarly perspectival, but modal interpretation of Dieks (2005, 2009). The similarity of the incompatible value ascriptions allowed by these accounts is compared with the incompatibility of attributions of tense to events in Special Relativity, and a better analogy is found with Dieks’ interpretation.

The consideration that Rovelli might offer in preferring his scheme to Dieks’ – its ability to accommodate non-ideal measurements involving partial correlations – is shown to conflict with the defense offered on his behalf by Brown, where it is claimed that certain relations are invariant between observers. It is argued that this picture is inconsistent with Rovelli (1996, 1998) and that if Rovelli’s (2005, 2007) view of the quantum state as containing probabilities for certain ‘quantum events’ is taken into account, then the claimed consistency between accounts is almost entirely vacuous.

A key concept Rovelli employs is that of ‘information’. He takes care to distinguish two uses, one of which he claims corresponds to the technical concept of Shannon information. Following Timpson (2008), I point out that the technical concept is inalienably tied to the practical problem of communication and so argue that his use of the term ‘information’ cannot avoid being associated with the everyday, epistemic, concept closely linked to knowledge. As such, he faces Timpson’s potentially fatal dilemma for information-based accounts of measurement, implicit in Bell’s third rhetorical question: ‘Information about what?’ Timpson claims that the information in any such interpretation must either be about the values that a quantity takes prior to measurement (hidden variables), or the measurement outcomes themselves (i.e. instrumentalist).

Rovelli’s ontology of quantum events, and his assertion that his account is non-anthropocentric, indicates an attempt to avoid the second horn of this dilemma and the associated charge of instrumentalism. However, I argue that this attempt fails on three counts: a failure to take into account the epistemic character of ‘everyday’ information and the nature of communication, an inability to meaningfully distinguish the quantum events of Rovelli’s ontology from measurement results, and the failure of RQM to meet a key requirement for the naturalization of an observer within a theory: that it allow a representation of observers within the description of reality provided by the theory.  These complaints entail that in Rovelli’s interpretation the probabilities contained within the quantum state refer only to the relative frequencies of measurement outcomes, hence the charge of instrumentalism is unavoidable.  Furthermore, I argue on this basis that his position is unavoidably solipsistic.

Finally, it is suggested that the information-based approaches of Fuchs’ Quantum Bayesianism, where the probabilities are associated with subjective degrees of belief, and Bub’s reconstructive project (with Clifton and Halvorson), whose interpretation by Bub (2005) is essentially communication driven, are to be preferred. Markopoulou’s causal quantum histories approach is discussed as an alternative, or perhaps complimentary, event-based account that would provide some objective relations between events.

Thanks to all who managed to attend the talk on Friday.  Apologies for the ridiculous quantity of slides I had managed to churn out (62 in case you’re wondering) which meant I ended the talk with a whimper half way through the argument.  This actually helped concentrate my attention somewhat on what I was really trying to say.  The above is the product of that reflection. I would be happy to add more detail if anyone is interested, hopefully at a level in between quick-and-dirty abstract and tedious-and-endless presentation.

Dave and I had a wonderful and intimate celebration when he got home. And it was a double celebration. Not only had I gotten the gig with WKRV, but he had landed a great contract to do graphical digital design for a gaming company in Northbrook. He was ecstatic—the 2 things he loved most of all (next to me, of course) was computer games and digital graphics, and they were going to pay him to do both. What more could a guy want?

Now with the lovemaking over and my husband sleeping contentedly next to me, I lay staring at the ceiling unable to sleep. The doubts that had been in my mind since the interview at the radio station, were now nibbling at me with their little rat teeth. How could I even think I could do this? I had to be crazy. I couldn’t do readings on the fly—not unless I just “faked it”, as Katy (my best friend) so quaintly put it. I hadn’t signed the contract yet. Maybe I should just send them a “sorry to have bothered you” note.

I rolled over and propping myself up on one elbow, I gazed at Dave’s quiet, restful face. His lips were curved up in his trademark quirky smile, and I could hear his voice telling me that I would be just fine. Earlier he had reassured me when I voiced my doubts, telling me that I had obviously gotten through the interview just fine, so I would do just fine with the actual show, too.

I traced a finger across his smile, and he murmured something in his sleep. I kissed two of my finger tips and placed them against his lips, then I silently slipped out of bed. I wasn’t going to be able to sleep, I knew that. So, rather than wake him, I decided to try to do some of the readings that were piling up.

Although, I’m more of a daylight dweller—I love sunshine and often contemplate dragging Dave off to live in some place like Arizona or Florida—night time has its own specialness.

At night most people are asleep, so the noise level drops significantly—and I’m not referring to the ambient noise that people hear with their ears, though that does drop, too. The noise I’m referring to is the type created and felt through your aura. Every thought, emotion, idea, movement, comes out in your aura, and this energy pulses outward affecting everyone around you.

An aura is a large (sometimes a very large) bubble of energy that surrounds you. Auras can sometimes lie close to a person like a second skin, or they can be as a full and flowing as a hot air balloon. Most are somewhere in between. And, just because you hide in a house, your energy, your aura, can surround the house and overflow into your neighbor’s yard or apartment, and their aura can be in your vicinity. So, imagine millions of people all moving around thinking, planning, shifting emotions, and you can see how a normal day can be very noisy for those of us perceptive enough to “hear” it.

Of course, most people aren’t sensitive enough so don’t “hear” a thing (sometimes I just can’t help thinking how lucky they are). But people like me, we ‘hear’ all that noise. In fact, focusing in on just one person’s ‘noise’ or aura is one way to do a reading. You’d be surprised at the information everyone carries around in their auras.

Besides the superficial noise of immediate surface thoughts (“Wonder what I should make for dinner?” “Did he just look at my breasts? What a sleaze.” “I hope I’m not getting a cold.”), there are emotions (anger, love, fear, envy, depression) that are changing sometimes from minute to minute, ideas (such as musical or artistical compositions, mechanical or mathematical insights) that are at a deeper level of cognition. There are also memories stored in each person’s aura (memories of skills used in previous lives, and even memories of fears (drowned in 12 other lives, therefore, water is bad).

When people sleep, a lot of the surface thoughts and emotions are shut down, so the noise levels drop significantly. It makes it a lot easier for me to do what I do, which is read their auras and relay the information back to them. See, most people don’t know how to read their own auras anymore—I think at one time it was an easy and common thing to do, but nowadays, most people don’t even have time to read a book, let alone read their own auras—therefore, they seek out people like me.

There’s another reason I like the night, though. I love seeing the lights. By focusing on the physical world with my inner vision—my third eye, if you will—I can see the webbing of energies that link every object in our world. Each part of the world—every person, plant, object (chairs, sofas, cars, buildings, etc.), animal, insect, etc.—is linked to every other part of the world. And at night, those links glow, creating a beautiful light display.

It’s like a gorgeous glowing tapestry of light. Golds twined with silver, and outlined with purples and blues. There are oranges and greens, reds and yellows, and they’re all woven together creating a picture that changes every second. It swirls and ripples, and sometimes I can almost make out the overall pattern of it, but then it shifts and another pattern surfaces, only to be replaced by another, and another. It’s almost hypnotic in its beauty.

I padded out to the small desk in the corner of the living room where I kept my laptop computer, and I joined the small contingent of people who were enjoying the quiet of the night.

I did four readings, two of which were extremely long, and by the time I finished typing them up, I knew I’d be able to sleep. I closed down my computer, and crept back into the bedroom. Boxr, our 10-pound Russian blue cat, was sprawled across my half of the bed.

I pushed the box-loving cat toward the foot of the bed, and slid beneath the covers. I scrunched over and snuggled against my husband’s back and was soon sound asleep.

All too soon, the alarm clock buzzed, and I pulled the blankets over my head in an effort to negate the fact that I had to get up. I heard Dave in the shower—he loves to sing, but he really shouldn’t. He can’t carry tune to save his life—so, I grudgingly pushed the covers down.

Grumpily I got out of the nice warm bed, and headed to the kitchen to make coffee. I put together lunch for Dave, found his missing keys, and wave mechanicsd him down the driveway on his way to the train. I then, with only a few pangs of guilt, went upstairs and crawled back into bed.

Within moments of falling back to sleep, I found myself planing.