Archive for the ‘Books’ Category

Needle in a haystack

May 7, 2006

I’m well on my way reading Penrose’s Road to Reality, and (as you may expect) having a great time. The first part, devoted to maths, was just delicious and, to me, an excellent refresher that has prompted me to dust from the shelves some books on rediscovered topics like complex analysis (“Visual Complex Analysis” (Tristan Needham)) or fiber bundles &co. (“Gauge Theory and Variational Principles” (David Bleecker)).

As for the physics chapters afterwards, i find their quality more uneven. In general, my impression is that one needs a pretty good basis on the topics discussed by Penrose to really appreciate and fully understand many a discussion in the book. I’d even say that pretty good means a university background in a technical area. Albeit, admittedly, it’s hard to judge from my standpoint, i don’t buy the claim (made at the preface) that even someone don’t getting rational numbers can understand (parts of) the book. For instance, i’ve found that the chapters on Relativity provide an insightful overview for people in the know, but, in my opinion, will fail to convey the deep principles of the theory to newbies. This impression was reinforced after reading the chapters on Quantum Field Theory: i’ve already forgotten most of what i learned about QFT at the university, and, besides, i never really understood it in depth. As a result (i think), those chapters of the book devoted to QFT have been frequently hard to understand to me, and i’ve finished them with a strong feeling of being missing many important points. Oh well, maybe it’s just me.

GodDespite the above knit-picks, the book is absolutely worth reading. In particular, i’ve enjoyed immensely the chapters dedicated to Cosmology and the problem of the low entropy of the Big Bang. If we are to believe in the second law of thermodynamics, the entropy in the universe has been increasing since its origin some 13 thousand million years ago. In other words, its path through the phase space has been traversing regions of greater and greater volume, where a region stands for a set of microscopic configurations giving rise to the same macroscopic behaviour (for instance, there are virtually an infinite number of possible positions and velocities for the atoms in the air of my room which gives raise to macroscopic values for pressure, temperature or smell that are indistinguishable by means of macroscopic measurements). Taking into account that the most entropic objects in the current universe are black holes (using the famous Bekenstein-Hawking relationship between a black hole’s entropy and the area of its horizon; see here and here for details) and an estimation of the number of black holes in the current universe, Penrose concludes that the volume of the phase space compatible with our Big Bang is about one part in 10^{10^{123}} of the total available. As shown in the figure, god must have had a hard time finding the exact point to start all this! If you don’t have Penrose’s book (or want to read a nice summary), you can read about these intriguing issues in his excellent survey (Space-time and Cosmology (PDF), part of the freely available Tanner Lectures on Human Values from the University of Utah [1], or hear and see his three lectures at Princeton University. There you’ll find why inflation and the anthropic principle, fashionable cures to everything as they may be, are not a solution to this conundrum (at least according to Penrose; you may find amusing to think about it a bit before reading the answer ;-)). Enlightening.


[1] As an aside, you’ll find lots of other interesting Tanner Lectures in their site, including this one by Richard Dawkins on Science and Religion.

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Cosmic Variance’d

May 3, 2006

To my great surprise and pleasure, Sean has been so kind as to mention physics musings in his last post at Cosmic Variance. First of all, I just wanted to say thanks: i’m sure that in many cases reading Cosmic Variance is one of the reasons one starts thinking of writing a physics blog in the first place. At least it was for me. I’m also happy because i’m fond of Sean’s writings in more than a way. A few months ago, i spent some weeks getting up to speed, again, in General Relativity, and carried home several textbooks. Some from my university days, and others published in the interim. And of all those books, the only one that i finally read (and enjoyed) from cover to cover was Sean’s “Spacetime and Geometry: An Introduction to General Relativity”. I’m sure it needs no presentation or recommendation, but, just in case, you can get a feeling of how good it is by reading the notes it’s based on or visiting the book’s website.

Sean’s post has also enlarged my list of monitored blogs with several interesting new entries. Among them, there’s one i’ve been enjoying specially during the last couple of hours. Lest you miss it in the post’s comments, here’s my recommendation: Alejandro’s Reality Conditions is just excellent. He has a lot to say about quantum gravity and the interpretation of quantum mechanics (two of my favourite areas), but also frequently touches more philosophical themes i find absorbing, like cognitive science and the problem of consciousness. With a dose of humor and many interesting links for a good measure. Highly recommended!

The music of emergence

May 2, 2006

I just stumbled upon a beautiful site, The Music of the Quantum, whose (apparent) main theme is a peculiar composition by Jaz Coleman. It was commissioned by the Institute for Complex Adaptive Matter (ICAM) as a public outreach event, first performed in New York at Columbia University in 2003. The event was performed by the Sporcl quintet from Prague, and narrated by Robert Laughlin and Piers Coleman (yes, it was that 1998 Nobel laureate Laughlin, for his theory of the fractional quantum Hall effect). According to the site,

The piece was written to bring out, musically, some of the themes of the quantum emergent world. The melody of this unique piece is carried between a violin and an accordion, the idea being to capture the duality of quantum mechanics between these two contrasting instruments.

Besides hearing to the (pretty good, to my taste) music, you can see three nicely done video clips of its perfomance, and an interview with Coleman. But that’s not all.

As it happens, the site has a sort of double agenda, and is full of information on what one may call the emergent viewpoint of physics, championed (among many others) by Laughlin, the ICAM and friends. I first read more or less seriously about this viewpoint a few months ago, via Laughlin’s very interesting “A Different Universe: Reinventing Physics from the Bottom Down”, which was a bit of an eye opener to me. As a theoretical physicist, i’ve had a reductionist upbringing. When i was in high school, a dear maths prof of mine’s used to tell me that i was what Einstein called (in this classic article) a tamed metaphysicist:

I believe that every true theorist is a kind of tamed metaphysicist, no matter how pure a “positivist” he may fancy himself. The metaphysicist believes that the logically simple is also the real. The tamed metaphysicist believes that not all that is logically simple is embodied in experienced reality, but that the totality of all sensory experience can be “comprehended” on the basis of a conceptual system built on premises of great simplicity. The skeptic will say that this is a “miracle creed.”

… and i felt i really was (and probably still am) one of those beasts. From that stance to reductionism there’s just a tiny step: to me, physics was the pursue of ultimate causes, the art of reducing complex systems to its constituents and explaining everything in terms of the interactions between those constituents. A very naive philosophy, if you like, but one that is reinforced by many science books and academic curricula, and which is implicit in much of the research in fundamental physics even these days (for instance, Steven Weinberg’s “Dreams of a Final Theory” is a perfect exponent of this ideology). In my experience, there are still many theoretical physicists that look at colleagues in experimental physics, biology or chemistry over their shoulders, feeling like some sort of priesthood in search of the ultimate truth. But, hopefully, maybe i’m just overreacting, as usual.

Anyway, people like Laughlin have a very different worldview, and are all for explaining natural phenomena in terms of emergent behaviours, that is, properties that appear, as a consequence of organizational principles, when great numbers of, say, atoms are put together. Take, for instance, metals: according to this view, there’s nothing in a gold atom that explains its macroscopic qualities, which appear only when you put many of these little pieces together and let them interact. The laws according to which these swarms of subsystems organize themselves are not to be viewed as a direct consequence of their structure, and in fact the claim is that the behaviours come from organizational laws that are independent of the detailed structure of those constituents (or is, at least, compatible with many different ones). The website contains several (short) clips where these ICAM guys give a far better explanation of these and similar ideas. I find them very refreshing and a good antidote against narrow-mindedness. Which does not mean, by the way, that one has to accept all this emergent worldview uncritically. Laughlin likes to call reductionism an ideology, but, to be fair, reading his book now and then i felt he was close to making emergency an ideology too (in the sense that, according to him, everything seems to be explainable in terms of emergentism)! It must be the reductionist in me.

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Lost causes in physics

April 30, 2006

Before you start your brand new research programme, you may be interested in at least skim over R.F. Streater‘s twenty-six lost causes in physics, if only to have a laugh at some of them (like, e.g., number seventeen, converting R. Penrose to the Copenhagen view). But make no mistake: the list is not intended as a humorous compendium and many of its entries come with a quite detailed rationale and pointers to the literature, which make it an interesting, if highly opinionated, reading. On a more positive note, in Regained Causes in Theoretical Physics, Streater gives advice on research topics, according to him, worth pursuing.

In case you need a refresher, Streater, now seventy, besides having Erdös number 3, wrote his thesis under Abdus Salam‘s supervision, and is the coauthor (with A. S. Wightman) of the classic book “PCT, Spin and Statistics, and All That”. Most of his almost five decades long research career has been devoted to axiomatic quantum field theory. Not that bad for getting an advice, i think. He has also a bit to say about many, many physicists, present and past. Pretty interesting.

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The philosophy of space and time

April 16, 2006

Isaac NewtonWith this brief post, i just want to draw your attention to a site i stumbled upon while writing my previous entry: the Philosophy of Space and Time pages at Kyoto University’s Philosophy and History of Science homepage. Despite the occasional sections in Japanese, most of the texts there are in English, very well written and usually accompanied by beautiful diagrams: their author, Prof. Soshichi Uchii, has a soft spot for painting and notable talent, as shown for instance in his portraits gallery). But, as i said, it’s Uchii’s essays and studies what’s really interesting in that site. I already mentioned the series on the Genesis of General Relativity, but there is much more, too much to list in here. For instance, the latest addition is an amazing collection of commented excerpts from the Clarke-Leibniz correspondence, which somehow commenced the still on-going debate between the relational and substantivists views of space-time. Definitely recommended reading, accessible to both experts and laymen.

Also worth noting are Uchii’s PHS Newsletters, which, among other things, contain carefully written book reviews: for instance here is the one devoted to two books that you may find interesting: Brian Green’s The fabric of the Cosmos and Lee Smolin’s Three Roads to Quantum Gravity, which describe the two ‘mainstream’ competitors in the race for a quantum theory of gravity (and, sometimes, everything). Also interesting is his review of Julian Barbour’s The End of Time, a provocative, to say the least, new way of bringing Mach’s principle to the forefront of our physical theories. Happy reading!

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Gravity’s shadow

April 12, 2006

Ordering a book online is always an excellent excuse to order another one in the same pack, on the basis of amortizing the packing and sending expenses. Thus, Rovelli’s book came with good company: Harry Collins’ “Gravity’s Shadow : The Search for Gravitational Waves”, an awesome history of the search for gravitational waves from Weber to LIGO. Interestingly, it’s written by a sociologist, but a well-informed one: Collins has spent the last 30 years among physicists, so i expect he got the science right. Of course, by awesome, i mean that it looks awesome, since i haven’t read it yet (albeit it’s been inserted near the top of my growing reading queue). But i’m confident it will live up my expectations, specially after reading Lee Smolin’s opinion on it. One can also read some chapters available at the book’s site.
Weber and his detectorBy the way, you don’t need to be an expert to read this book, only have an interest in gravitational waves and/or the sociology of science serious enough to swallow around 900 pages. Unfortunately, i’m not aware of any other popularization on gravitational wave physics, but you can read this little introduction from ESA’s site (with links to the projects i work on, LISA and LISA Pathfinder) as a quick start, take a brief yet nice course at Caltech, read about them in the BBC, visit a museum, learn about the strong (albeit indirect) evidence on their behalf, bet on their discovery, or participate in it via Einstein@Home (the site also contains useful information about what GW are and how we try to detect them). You can also get a little more serious and go for this living review of GW detection or follow Kip Thorne’s course on Gravitational Waves (videos of the lectures included).

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The sooner, the better

April 12, 2006

Rovelli’s “Quantum Gravity” arrived today (well, yesterday actually), sooner than i expected. And, albeit my plans were to finish Penrose (see reviews, specially this one) before starting this one, i’ve just read the first chapter and am hooked. This first chapter is an overview of Loop Quantum Gravity, a roadmap of what’s in store in the rest of the book. Basically, it’s an extended version of the essay i mentioned in my previous post, and is, i think, quite readable by non-specialists. The good news is that a draft version of the book is available online, so you don’t need to spend money to read it. I’ll try to keep (the two of) you posted on my readings.

Skimming the first chapter’s bibliography, i’ve remembered a couple of ‘popular-science’ books on QG i own: “Three Roads to Quantum Gravity” (Lee Smolin) and “Physics Meets Philosophy at the Planck Scale: Contemporary Theories in Quantum Gravity”. I read them 3 or 4 years ago, and they may be a good companion while commuting to work, and an alternative for those of you with a moderate interest in these matters.

If you have a bit of mathematical background, this introductory article is also a good way to get acquainted with the basics of LQG and one of its central results, the quantization of space. Have fun!

The Chymistry of Isaac Newton

April 9, 2006

When i was young(er), i had the immense fortune of having a mentor, Dr. Fidel Antonio Alsina, who guided me into discovering the wonderful world of physics. His lessons (by letter at first and later, when he came to Barcelona, in person) were mostly centered on relativity, but there were lots of opportunities to talk about physics and epistemology as well. He taught me to keep an open and critic mind, and not to accept arguments on the grounds of authority alone: he was fond of remembering that Newton believed sunspots were windows used by the inhabitants of the Sun. But, at the same time, he warned me against becoming a crackpot (“sages are silly, but not that silly”), and to study hard and respectfully the writings of great physicists, like Newton himself. I remember Fidel recommended me reading Newton’s Queries at the end of his Optiks to get a glimpse of how Newton’s mind worked, an advice that i can’t but pass on to all of you with a serious interest in science. As it comes, i can do even better, and point you directly to the Questiones quaedam Philosophiae, which are available online as part of The Newton Project, an ambitious initiative to put online all of Newton’s manuscripts. A related project is The Chymistry of Isaac Newton, which is publishing Newton’s alchemical works. I’m not specially interested in the later, except for their publication of Newton’s most complete laboratory notebook, which includes many of his optics experiments. A great way of seeing a great mind in action.

If you have not yet read any biography of Newton, of course the canonical reference is Westfall’s awesome Never at Rest : A Biography of Isaac Newton, but let me also recommend (for those of you with less time in your hands, and a library at hand, since it seems to be out of press) Gale E. Christianson’s In the presence of the Creator: Isaac Newton and his times, a book i enjoyed immensely.

Quantum Gravity

April 6, 2006

My research has always trodden the classical realms of General Relativity. As a result, my knowledge of advanced quantum field theories is shaky to say the least. Not that i wasn’t interested in foundational questions or in the quest for unification, or that i didn’t read something about those issues. Now i’d like to learn a bit more.

I’ve always found the fixed-background approach taken by QFT and (to my limited knowledge) String theory at odds with General Relativity’s spirit. In my opinion, gravitation is not just another force to be quantized, but rather a description of the background were other forces live in geometrical terms. If anything is to be quantized to obtain quantum gravity, it’s geometry. And since we seem to live in a world where every relevant quantity is discrete, the idea of a granular structure of space-time itself is, to me, all but natural. Although i read (without really understanding) that String theory predicts a quantized, relational space-time, the repeated affirmations of people like Witten about our not yet (?) understanding M-theory, together with the dismal multiverse speculations i’ve read recently (Lee Smolin explains exactly how i feel about it), have turned my attention, again, to Loop Quantum Gravity as an appealing subject of study. These days, i’ve been skimming several introductory and review articles, including the delicious Quantum Gravity Seminar by John Baez, and Smolin’s PI Course. The latter will be specially useful when my copy of Rovelli’s Quantum Gravity arrives in a couple of weeks, which will be about time to start studying LQG seriously, most probably guided by Christine Dantas’ excellent reading list on the subject.

Roger PenroseIn the meantime, i plan to end Roger Penrose’s The Road to Reality, which i’m sure i don’t need to review for you. In my case, this amazing book is being an excellent way of reviewing and relearning a lot of stuff i was supposed to know from the old times, and then discovering a lot of new things. I respect Penrose opinions immensely, and after seeing these recent lectures (half-way the page), i’m specially curious about his critiques of both String theory and Loop Quantum Gravity.

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Physics fiction

April 6, 2006

Just to start on the light side, i like to read novels and fiction featuring scientists, provided they present convincing, well-documented characters and situations. An excellent example of such a work i read recently (and wholeheartedly recommend) is Neal Stephenson‘s Quicksilver, where you’ll find Newton, Leibniz and the whole Royal Society playing an important part in the (otherwise fictional) history. Quicksilver’s sequels, which conform the so called Baroque Cycle, are awaiting in my shelves.

My other physics-fiction all time favourite is Gregory Benford‘s Timescape. Benford is a theoretical physicist, and it shows: this history about time travel is as sound as modern physics can make it.

I’m not much of a comic reader, but today this post captured my attention. Matt Fraction shares a sneak-preview of his forthcoming graphic novel, The Five Fists of Science, starring Mark Twain and Nikola Tesla in a race to save the world from Thomas Edison and J.P Morgan. The PDF preview looks pretty nice, with a charming nineteenth century atmosphere all around. Surely, not as good as Stephenson or Benford, but worth a look nonetheless.

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