Sunday, December 31, 2006

Happy New Year!

Dear Fellow Readers:

I wish you all a good start into the year 2007, whether you are with your family or on your own, whether you are on a sunny beach or stuck in snow knee-deep.


Most interesting posts of the year (as measured by number of comments):

    "You only see what your eyes want to see
    How can life be what you want it to be
    You're frozen
    When your heart's not open

    You're so consumed with how much you get
    You waste your time with hate and regret
    You're broken
    When your heart's not open

    Love is a bird, she needs to fly
    Let all the hurt inside of you die
    You're frozen
    When your heart's not open"

~Madonna, Frozen

Friday, December 29, 2006

Cracked Pots

"An elderly Chinese woman had two large pots, each hung on the ends of a pole, which she carried across her neck. One of the pots had a crack in it while the other pot was perfect and always delivered a full portion of water, at the end of the long walk from the stream to the house, the cracked pot arrived only half full.

After two years of what it perceived to be bitter failure, it spoke to the woman one day by the stream. “I am ashamed of myself, because this crack in my side causes water to leak out all the way back to your house.”

The old woman smiled, “Did you notice that there are flowers on your side of the path, but not on the other pot’s side? That’s because I have always known about your flaw, so I planted flower seeds on your side of the path, and every day while we walk back, you water them. For two years I have been able to pick these beautiful flowers to decorate the table. Without you being just the way you are, there would not be this beauty to grace the house.”

Each of us has our own unique flaw. But it’s the cracks and flaws we each have that make our lives together so very interesting and rewarding. You’ve just got to take each person for what they are and look for the good in them."

I'm having a slow time... so today I just wanted to share this beautiful story that I found on Tommaso's blog.

Flower graphics from Juelie's State Flower Garden of Gifs.

Tuesday, December 26, 2006

Anomalous Alignments in the Cosmic Microwave Background

I just answered a phone call for my parents. A very distant relative somewhere from the Northsea coast, who I vaguely remember having met sometime middle of the last century. She apologized that we didn't get a Christmas card this year (not that anybody had noticed) because her husband broke an arm (a-humm). When asked, I told her I turned 30 this year, upon which she exclaimed: OH MY GOD!

Now I feel really old. What helps in such a situation is to look at a picture of something even older. Like the cosmic microwave background (CMB). Since we've lately heard a lot about the high angular moments that allow us to determine the parameters of the LambdaCDM model, and since I'm already feeling low, let me instead tell you something about the low angular moments.


Back then when the universe was young and only 300,000 years old, radiation decoupled from matter and since then, photons could travel almost undisturbed. The CMB shows the temperature, or the inverse wavelength, of the microwaves that we receive on earth from this early times. This afterglow carries information about the conditions in the early universe which can help us understand the origin of the structures that we see today, and the processes that were important in this era.

We can draw the temperature of the received microwave signals on a map similar to how we draw a map of the earth. However, for the CMB, the orientation of the map is chosen such that the plane of the Milky Way falls on the equator.

The top figure to the right shows the temperature in a scale in which blue is 0 Kelvin and red is 4 Kelvin. What we see is the mean temperature of the CMB of 2.725 Kelvin. On this rough scale it looks very uniform. DMR sky map1

The middle image is the same map displayed in a finer scale such that blue corresponds to 2.721 Kelvin and red is 2.729 Kelvin. The "yin-yang" pattern is the dipole that results from the motion of the sun relative to the rest frame of the CMB.
DMR sky map2
The bottom figure shows the microwave sky after the subtraction of the dipole. On this map, the hot regions, shown in red, are only 0.0002 Kelvin hotter than the cold regions, shown in blue. The red band in the middle is dominated by emissions from the Milky Way.

DMR sky map3

What is usually shown in the CMB pictures is thus not the absolute temperature, but the differences between measurements taken in different directions, this is also called anisotropy - the deviations from isotropy.

An useful orientation in these maps is the ecliptic, that is the apparent path of the sun. If you draw it onto the sky map, the ecliptic will look like a lying S. The maximum and the minimum on that curve the are the equinoxes*. On the days when the sun is on the equinox, there are 12 hours each of daylight and dark.


The temperature anisotropies in the CMB have been measured with very high accuracy by the WMAP mission (Wilkinson Microwave Anisotropy Probe). The full map contains a lot of very small structures, you find a picture here (notice the scale!).

If one wants to analyse this data, one takes all these fluctuations apart in less messy shapes, called multipole moments. This is a procedure that essentially decomposes the whole picture into simpler ones that add up to the full one. For scientific purposes one uses very specific shapes that are defined though functions, the so called spherical harmonics. These are labeled by two numbers one of which is called the multipole, and usually denoted with l. The first multipole is the monopole, followed by the dipole, the quadrupole, the octopole, and here I've exhausted my Latin.

The lower the multipole moment is, the simpler is its shape. You can look at a picture of the lowest multipole moments here. To describe how you have decomposed the full picture into the multipoles, you will need to specify the axis of these things. The higher the moment is, the more axis you have to specify.

The pretty picture below shows the octopole moment that is extracted from the CMB (the three year Internal Linear Combination map ILC123). Again, red indicates the hotter, and blue the colder areas.

The solid line is the ecliptic plane and the dashed line is the supergalactic plane. Also shown are the directions of the equinoxes (EQX), the dipole due to our motion through the universe, the north and south ecliptic poles (NEP and SEP) and north and south supergalactic poles (NSGP and SSGP).


The dipole moment is defined through one axis that intersects the sky sphere. For the quadrupole moment one needs to specify two axis. These span a plane, the plane has a normal which defines another axis (its the cross-product of the other two). The octopole comes with three further axis, and correspondingly three normals.

In the above figure, the quadrupole vectors are plotted as the solid red symbols. (Different symbols are results from different maps, the ILC123 analysis is shown as triangles.) The octopole vectors are plotted as the solid magenta symbols for each map. The open symbols of the same shapes and color are for the normal vectors for each map (see here for what the other symbols mean).

As you can see in the figure, the normals of the quadrupole and the octopole are quite close together and clump in the South-South-West. This anomalous alignment is unlikely at the 99.9% CL [3]. But even more puzzling is that they are aligned with the direction of the cosmological dipole and the the equinoxes at a level inconsistent with Gaussian random, statistically isotropic skies at 99.95%CL [3]. To put it it less technical, this means the probability that this happens just by coincidence is very small.

Also remarkable is how the ecliptic plane carefully separates the weaker power in the northern ecliptic hemisphere from the stronger power in the southern ecliptic hemisphere. This is known as the north-south asymmetry. The confusing thing about these results is that there is absolutely no reason why the CMB - if we understand it correctly - should be correlated with any features of our local solar system. These correlations have been confirmed in three year WMAP data[2].

There are several attempts to explain these anomalies, e.g. instead of using the standard Friedmann-Robertson-Walker metric, one can consider anisotropic or inhomogeneous models, foreground effects, lensing effects, quantum gravitational imprints, non-trivial topologies of the universe, modifications of the gravitational potential that the background photons might experience (Rees-Sciama/Integrated Sachs Wolfe effect), scattering of the CMB (Sunyaev-Zel'dovich effect), etc.

So far, it is not clear how the measurements can be convincingly explained...


I've learned quite a lot while writing this post. Maybe getting older isn't all that bad.

    People like you and I, though mortal of course like everyone else, do not grow old no matter how long we live...[We] never cease to stand like curious children before the great mystery into which we were born.

~Albert Einstein, in a letter to Otto Juliusburger

Further reading

[1] On the large-angle anomalies of the microwave sky
Authors: C. J. Copi, D. Huterer, D. J. Schwarz, G. D. Starkman

[2] Can extragalactic foregrounds explain the large-angle CMB anomalies?
Authors: Aleksandar Rakic, Syksy Rasanen, Dominik J. Schwarz

[3] Mysteries on Universe's Largest Observable Scales
Author: Dragan Huterer

[4] The axis of evil
Authors: Kate Land, Joao Magueijo

See also: Multipole Vector Information

Footnote: Is there somebody who could explain me why these are the extrema on the curve when the equatorial plane is defined through the Milky Way? Is this just coincidence?

TAGS: , ,

Sunday, December 24, 2006

Christmas Broadcast

Whatever Bee may think about the German public radio Deutschlandfunk, it is indeed my favourite radio station, with lots of interesting programmes. One special gem is the daily Kalenderblatt, a five-minute feature about some historical event related to the current date. This morning, the programme looked back on the first radio broadcast, 100 year ago on Christmas Eve 1906. You can listen to the programme (in German) here.

The early wireless communication technology invented and pushed by Guglielmo Marconi was based on electrical sparks creating bursts of radio waves. This was fine for transmitting Morse codes, but the signals used a very broad spectral range - it was not possible to tune in to a specific station as we are used to today - and could not be modulated to carry music or voice. The German word Rundfunk for radio broadcasting goes back to this technology: Funken is the German word for spark.

Reginald Fessenden, Radio Pioneer and Christmas Broadcaster (source)

The Canadian engineer Reginald Fessenden had the idea to use a continuous radio wave of a specific frequency as a carrier to transmit a signal. He constructed a high-frequency alternator that produced frequencies up to about 100 kHz, and experimented with this technology in 1905/06. His original idea was to build a wireless telephony system, to offer some alternative to the monopoly of the dominating telephone companies. He had to cope with some problems and drawbacks, but then, to cite from this paper:

Fessenden's greatest success took place on Christmas Eve 1906, when he and his colleagues presented the world's first wireless broadcast. The transmission included a speech by Fessenden and selected music for Christmas. Fessenden played Händel's Largo on the violin. That first broadcast, from his transmitter at Brant Rock, MA was heard by radio operators on board US Navy and United Fruit Company ships equipped with Fessenden's wireless receivers at various distances over the South and North Atlantic, and in the West Indies.
Fessenden and Marconi: Their Differing Technologies and Transatlantic Experiments During the First Decade of this Century, by John S. Belrose; International Conference on 100 Years of Radio, September 1995.

100 years is a long time ago, and for me today, used to sit comfortably on a sofa with my notebook and connected to the internet via WLAN, its is hard to imagine the world before radio broadcasting. But then, I remember my grandparents, my father's parents, who were just kids in 1906. They grew up in a world very different from today, to see so many things happen and change. What will be in 100 years from now?

Merry Christmas to all of you!

The Satire strikes back

It's always nice to be back home. Your family does so kindly remind you of your biggest faults, mine being that I can't keep my mouth shut.

Even though I was stuck in a boeing, I couldn't avoid noticing Scott Aaronson's offer

"I have therefore reached a decision. From this day forward, my allegiances in the String Wars will be open for sale to the highest bidder. Like a cynical arms merchant, I will offer my computational-complexity and humor services to both sides, and publicly espouse the views of whichever side seems more interested in buying them at the moment."

and so, here's my comment:

For those readers who don't know what the fuck he's talking about, let me briefly summarize the status Christmas 2006:

Physics can roughly be divided in experimental and theoretical physics. There's a sub-field of the theoretical part which is looking for the unification of the forces that we observe in nature. This unification is generally expected to also solve the question of how to quantize the gravitational sector. A sub-field of that sub-field of that part has an approach based on one-dimensional objects rather than, as currently used, pointlike objects. This sub-field of a sub-field of a part of the physics community has gotten a lot of attention over the last decade, you might have heard of them, they call their approach 'string theory'.

Since funding in scientific research, especially on the theoretical side, is far too short in Europe as well as in North America, it matters a big deal where that money goes, because people go where money goes. And besides chalk, notepads, and coffee, people is what theoretical physics is made of. Therefore, there's always discussion about who gets what amount of money. Presently, there are fairly many people working on string theory, and considerably less on other approaches, esp. regarding the holy grail of quantum gravity. On no front though, there's noticeable progress. Therefore, we found it's a good idea to start accusing each other of having failed, as to distract us from our every day work which isn't going anywhere.

In a time when public advertisement of research has come to play a role in the distribution of financial support, it is unfortunately quite common to point out the successes, and keep quiet of drawbacks. This doesn't only apply for string theory, but also for many other sub-fields of sub-fields, and I'd call that a consequence of capitalism infiltrating science. A mixture that imho is mutually incompatible, potentially fatal for both sides, and unsurprisingly far more advanced in North America. Look, there's a reason why academics have often been pictured as sitting in an ivory tower. That's because you can't just put your stupid equation on the stock market, advertise it, and if sufficiently many people buy your idea then you're on the cover of Times magazine and made it! Nature decides whether you're right, or you're wrong, and let's not forget, theoretical physics is not about the researcher - it's about understanding the universe.

Now it happened in 2006, that a well known blogger with the name Peter Woit published a book which gives a brief introduction into our quest for the theory of everything, and summarizes some weaknesses of the string theory approach. Overall seen I found the book kind of depressing, you can read my review here.

Only some months later, another guy with the name Lee Smolin published another book, which is less depressing on the scientific side, because he smartly advertises his own pet theories that have later been thrown together and dubbed 'alternatives'. On the sociological side, his book attempts to analyze the reasons for the present lack of progress, and comes to the conclusion that the current policy of financial support doesn't sufficiently guarantee independence of researchers. Which is of course absolutely right, the problem here being that hardly anyone read more of the book than the subtitle which contains the word 'string theory' in connection with 'fall of a science'.

The result of that then being a big fuzz about whether or not string theory is science, religion, or merely media entertainment. Some highlights of the discussion are definitely over on Clifford's blog, look for the teacup series. Repeatedly, string theorists have been pictured as a community blinded by science, suffering from 'group think' that makes them immune against criticism, with charismatic leaders that do little than ingeniously advertising themselves in the media. On the other side, repeatedly the very existence of 'alternatives' has been doubted, and people working on it have been called crackpots. The latter word being one of the most frequently used ones in this debate, so keep it in mind if you want to comment on something. Other words that are of importance here are: predictions, metaphysics, glub-glub-glub, falsifiability, and mountain climbing. As Sean over at Cosmic Variance proudly points out, he has given this debate the name 'string wars' which stuck.

As I've tried to communicate previously, it is of course complete nonsense that string theorists are somehow different from other theoretical physicists. Overall seen, in my experience, they are as smart, stupid, or stubborn as the rest of us, see e.g. my post about the inverse problem. To come back to the reason of this writing, Scott has met some of this species in person and, to his surprise, noticed that indeed they are fairly reasonable and some of them even nice. Now he's confused and wrote a post about his confusion, which contains the quotation above. As one might have expected, his post resulted in several responses, over at Cosmic Variance, at Not Even Wrong, and obviously at Lubos' blog.

Where I think Lubos took Scott's writing too serious, Scott himself maybe wasn't serious enough. I admit that his offer to support whoever bids the highest amount of money did upset me as well. This type of thinking is exactly what will kill science, and I don't find such a statement particularly amusing. Whether or not we support a research branch should not be based on the amount of money they are able offer. If you are a theoretical physicist, your decision to work on a theory should instead be based on a well qualified opinion on the status of that theory.

I have a lot of understanding for people who are in need of a job, and therefore agree to work on other peoples ideas, in many cases this is the bare necessity of life (especially when with family). The way the hiring process is dealt with right now is one place where I locate the problem: researchers are most often selected for a certain task rather than for their qualities. Especially when it comes to postdoctoral researchers, there is the constant need to work on a field where positions are, and a field that gives you the chance to find a position afterwards. In many cases this means you better do what your supervisor finds interesting, or you'll end up without a helpful letter of recommendation, or without prominent co-authors, or both.

However, there is another place where I locate the problem. It is definitely true that people go where money goes, but to a less degree - and with an unfortunate time delay - money goes where people go. Therefore, I have absolutely no understanding for people who sell their scientific opinion for money easily. If anything, then this is my indicator that ethics in science seriously needs to be thought over.

Each time you nod when you want to shake your head you kill a piece of science, each time you say 'interesting' when you want to say 'bullshit' you kill a piece of science, each time you sell your opinion for money, you push us deeper into the dead end. If you don't have an opinion, then say so, or keep your mouth shut.

Merry Christmas.

NORAD tracks Santa

In 1955, a Sears store somewhere in Colorado Springs run an advertisement for children to call Santa on a special "hotline". Unfortunately, the telephone number was misprinted. Instead of Santa, kids reached the Commander-in-Chief of the Continental Air Defense Command (CONAD ). The CONAD staff kindly provided dozens of children with their latest update on Santa Claus' appearance on their radar.

In 1958, the governments of Canada and the United States created a bi-national air defense command for the North American continent called the North American Air Defense Command (NORAD) which inherited the Santa Claus tradition from CONAD.

In 2006, you can track Santa online on their website!

(Click to watch video)

Thanks to Andi for sending the link :-)


Saturday, December 23, 2006

Home for Christmas

I was supposed to help my mother decorate the Christmas tree, but I sneaked away to tell you something about the Christmas tradition in Germany (version: how I know it).

Unlike in North America, in Germany Christmas is not celebrated on Dec. 25th, but on the evening of Dec. 24th. The German word 'Weihnacht' is better translated as 'Holy Night'. The official holidays though are the two following days.
(Figure: My mum decorating the Christmas tree. She's complaining they don't sell any longer tinsel made of tin or lead, but only aluminium which is too lightweight to hang properly. Originally, tinsel was made of silver.)

The maximal disaster is when the Holy Night falls on a Sunday, which means you are stuck with your family over the weekend and two more days during which shops are closed, restaurants are overbooked, and there is an endless amount of bad movies on TV (like usually all parts of 'Gone with the Wind' and the like). On the other hand, this means you might actually read the books you found under the tree about Feng Shui for your new apartment or something.

On the 24th, families often attend mass in the afternoon. Even those who usually don't, because it's kind of fun to see the children act the Christmas story. There, you meet all the neighbors and people you know from around town (who will inevitably tell you how you almost burned down the church when you were 6, or do you remember how you painted the school yard in 19-eighty something?)

Back from church, parents will have to occupy the children until 6pm. Presents are not brought by Santa Claus, but by the Christkind (see Lubos' nice post) and are put under the tree. I have no idea why, but for most people I know the Christkind comes at 6pm straight, and before this, grandparents are supposed to read stories, or children have to play Christmas songs on the piano (the only thing I can still play on a piano are these stupid Christmas songs that I had to practice from Easter on or something).

There is no real traditional dinner for Holy Night. My mum says, this year we'll have fondue. For lunch on Dec. 25th it's pretty common to have duck with red cabbage and dumplings.


Friday, December 22, 2006

Stuck in a Boeing


As Stefan already mentioned, JFK was a mess yesterday. Here's how I killed time while sitting on board of a flight that was #10 in line for take-off.

To be sung to the tune of 'Stuck in a Moment' by U2
(see here for original lyrics)

    "I'm not afraid
    Of any plane in this world
    There's no scary story

    That I haven't already heard

    I'm just trying to find
    A decent window seat
    A neighbor who's quiet
    And something to read.

    I never thought you were a fool
    Now you need to use the loo
    You've gotta stand up straight
    Shift your own weight
    This flight is going nowhere, baby

    You've got to get your bags together
    You've got stuck in a boeing
    And now you can't get out of it

    Don't say that later will be better
    Now you're stuck in a boeing
    And you can't get out of it

    I will not forsake
    The meals that they bring
    Since Chicken or Pasta
    Is still better than nothing

    I am still enchanted
    By the movies they brought to me
    Though the headphone was broken
    And the screen I couldn't see

    And you are such a fool
    To book flights like you do
    I know it's tough
    It's been more than enough
    Of what you don't really need now
    More delay

    You've got to get your bags together
    You've got stuck in a boeing
    And you can't get out of it

    Oh love, look at you now
    You've got yourself stuck in a boeing
    And you can't get out of it

    But I will certainly never again
    Book a trip with American

    I've got to run, which one is my gate,
    It's a long way to go, and I'm far too late.

    You've got to get your bags together
    You've got stuck in a boing
    And you can't get out of it

    Don't say that later will be better
    Now you're stuck in a moment
    And you can't get out of it

    And if the night runs longer
    And if the day won't last
    And if your bag got lost
    Along the stony pass

    And if the night runs over
    And if the day turns to past
    You'll earn bonus miles
    Along this stony pass

    It's just a moment
    This flight will pass"



She is here! The metal box from Toronto has brought Bee safely to Frankfurt. And I was amazed by this quite recent, fancy feature of real-time online tracking of flights. I could see that her plane was delayed and just crossing the Irish Sea when I was about to leave home for the airport, so I knew I had to wait one more hour before finally seeing her...

Since all shops in Germany will be closed over the holidays, from Saturday evening until Wednesday morning, we had to do some shopping this afternoon, food etc. Among the typical sweets one can get before Christmas are the Schokoladen-Nikoläuse, small Nikolaus figures made out of chocolate. They are wrapped in coloured tinfoil and have the classical red coat/white beard design.

So, we were quite surprised to see this funny Nikolaus, eh, figure, in a Manga-Look. I know that Mangas have become quite popular in Germany recently, but that they ever would take the job of Nikolaus? And, by the way, we were asking ourselves, is there anything similar to Christmas in Japan right now?

Thursday, December 21, 2006


I was tagged by Clifford in a chain-process with the following instructions:
  • Grab the book closest to you.
  • Open to page 123, go down to the fifth sentence.
  • Post the text of the next 3 sentences on your blog.
  • Name the book and the author.
  • Tag three people.

The book closest to me, believe it or not, is Albert Einstein's 'Über die spezielle und die allgemeine Relativitätstheorie'. The number on the last page of the index is 112. Will you allow I take the next book? Let me try. It has more than 123 pages! Here we go:

    "He was amazed. 'How can it be? I passed through three magic gates. I talked with Uyulala, then I fell asleep. But I can't possibly have slept that long.'

    'Space and time,' said Engywook, 'must be different in there'. "

From 'The Neverending Story' by Michael Ende.

Ah, now who do I tag? Let's see... I'll have to tag Alejandro, who's destined to have an interesting book near him... Then, oh yeah, lets take Tomasso and Lubos. Merry Christmas :-)

The Longest Night of the Year

Today is the shortest day of the year, followed by the shortest night, also called 'winter solstice'. The sun appears at its lowest point in the sky, and its noontime elevation appears to be the same for several days before and after the solstice. The word is derived from the Latin word solstitium, which combines sol for 'sun' and -stitium, for 'a stoppage' or 'stand still'. Thus, solstice means sun-stand-still.

The exact date of this years winter solstice is Dec 22nd 00:22, Greenwich Mean Time.

Folks, this means that from tomorrow on, days will get longer again!

It will be a very short night for me though, since I'm flying eastwards and loose a couple of hours.

It is generally believed that our date for the Christmas celebration, as well as many traditions are linked to ancient celebrations around the date of winter solstice. At least I can't recall the bible says something about hanging shiny stuff on evergreen trees, or kissing the poor guy who didn't notice the mistletoe. And for me, the days getting longer is a good reason to celebrate!

"In pre-historic times, winter was a very difficult time for Aboriginal people in the northern latitudes. The growing season had ended and the tribe had to live off of stored food and whatever animals they could catch. The people would be troubled as the life-giving sun sank lower in the sky each noon. They feared that it would eventually disappear and leave them in permanent darkness and extreme cold. After the winter solstice, they would have reason to celebrate as they saw the sun rising and strengthening once more. Although many months of cold weather remained before spring, they took heart that the return of the warm season was inevitable. The concept of birth and or death/rebirth became associated with the winter solstice. The Aboriginal people had no elaborate instruments to detect the solstice. But they were able to notice a slight elevation of the sun's path within a few days after the solstice -- perhaps by DEC-25. Celebrations were often timed for about the 25th. [...]

CHRISTIANITY: Any record of the date of birth of Yeshua of Nazareth (later known as Jesus Christ) has been lost. There is sufficient evidence in the Gospels to indicate that Yeshua was born in the fall, but this seems to have been unknown to early Christians. By the beginning of the 4th century CE, there was intense interest in choosing a day to celebrate Yeshua's birthday. The western church leaders selected DEC-25 because this was already the date recognized throughout the Roman Empire as the birthday of various Pagan gods.[...]

Many symbols and practices associated with Christmas are of Pagan origin: holly, ivy, mistletoe, yule log, the giving of gifts, decorated evergreen tree, magical reindeer, etc." (source)

One tradition though remained a mystery for me for a long time. Why do people put an angel on top of their trees? Well, here's why (from

Xmas -- The tree angel tradition

Santa was very cross. It was Christmas Eve and NOTHING was going right. Mrs Claus had burned all the cookies. The elves were complaining about not getting paid for the overtime they had while making the toys. The reindeer had been drinking all afternoon and were dead drunk. To make matters worse, they had taken the sleigh out for a spin earlier in the day and had crashed it into a tree.
Santa was furious. "I can't believe it! I've got to deliver millions of presents all over the world in just a few hours - all of my reindeer are drunk, the elves are on strike and I don't even have a Christmas tree!

I sent that stupid Little Angel out HOURS ago to find a tree and he isn't even back yet! What am I going to do?"

Just then, the Little Angel opened the front door and stepped in from the snowy night, dragging a Christmas tree. He says "Yo, fat man! Where do you want me to stick the tree this year?"
And thus the tradition of angels atop the Christmas trees came to pass........

See also this interesting article about The Ancient Origins of the Winter Solstice, and the Wikipedia Entry on Solstice.

Wednesday, December 20, 2006

This and That

Some random things put together:
  • The arxiv will change its identifier scheme for new submissions beginning January 1st 2007. For more info, see here.

  • The well known German radio station 'Deutschlandfunk' (DLF) had a long report on Dec. 17th about 'Strings in the Crisis' (Strings in der Krise). This information was kindly provided by my husband, who actually listens to DLF. I like to call this station 'Depri-Funk', because no matter what they talk about, it's always depressing.

    If you know German, you can read the transcript on this site

    Strings in der Krise -- Physiker streiten um den rechten Weg zur Weltformel

    And if you really want, you can listen to the mp3 here.

    Be warned, if you do so, you'll have to endure a female voice intoning poems of the form "A Cosmos of slowness, Time is creeping, [...] Living in slow-motion. Dying in slow-motion [...] A Cosmos in reverse. The end is the beginning. Zebras are spitting grass to the ground. Men are dying [...] A cosmos of darkness [...]"

    ('A Kosmos der Langsamkeit.Zeit kriecht [...] Leben in Zeitlupe. Sterben in Zeitlupe [...] Ein Kosmos im Rückwärtsgang. Das Ende ist der Anfang [...] Zebras spucken Grashalme auf den Boden [...] Menschen sterben [...] Der Anfang ist das Ende [...] Ein Kosmos der Dunkelheit.')

    Jan Loius and Hermann Nicolai come to briefly express their excitement about string theory, and it is reported that: 'The Canadian physicist Lee Smolin finds in his book 'Zee Trobble Wiz Physiks' that strings are a failed thought experiment'. Later Nicolai says about the string debate caused by Smolin and Woit: "I wouldn't call that trouble, I perceived it somewhat as an amusement" ('Als Ärger würde ich das nicht bezeichnen. Ich habe das zum Teil etwas amüsiert zur Kenntnis genommen.') There is also the to-be-expected mentioning of L. Susskind and the anthropic principle, which is summarized stating that for Susskind it is 'a logical result of the mysterious six extra dimensions' ('eine logische Folge jener ominösen sechs Extradimensionen') that there exist 'universes that are inhabited only by speaking plants'.

    Quite interesting though is Thomas Thiemann's contribution in the end, where he briefly talks about his work on Loop Quantum Gravity. 'To describe the area of an A4* paper, it would take 1068 of these loops'. ('[...] um z. B. den Flächeninhalt von einem DIN-A4-Blatt zu beschreiben, bräuchte man 1068 von diesen Schleifen.')

    Since it is Depri-Funk, they finally come to the conclusion 'The situation [in LQG] is similar as it is in string theory. Researchers were able to properly write down the theory mathematically, but they aren't able to explain the world consistently. Both theories - strings as well as loops - are pure constructs. And both might remain speculations forever'

    ('Die Situation ist wie bei den Strings: Den Forschern ist es zwar gelungen, eine Theorie mathematisch sauber aufzuschreiben. Aber beide Theorien scheinen noch längst nicht in der Lage, die Welt schlüssig zu erklären. Beide Theorien - Strings wie Loops - sind bislang pure Konstrukte. Und beiden droht das Schicksal, für immer spekulativ zu bleiben.')

  • Weird Google searches that lead people to this blog:

    I also noticed with astonishment that my blog is currently the 4th hit for 'Peter Woit'. How did that happen?

  • Tomorrow morning, I'm stepping into a metal box in Toronto. It will make funny noises for too many hours, and when I step out of it, I'm hopefully in Frankfurt. That is, you are facing a slow-motion time on this blog.

  • And in the absence of anything more interesting to say, I'd like to point you towards this interesting blog, which I stumbled across today:

    Aaron in Afrika

* For the US visitors: A4 paper is used in the rest of the world, but is roughly the same size as letter format.

Tuesday, December 19, 2006

Naval Amphibious Base, Coronado

Today on Google Earth I saw...

"The Naval Amphibious Base (NAB) Coronado is located just across the bay from San Diego, CA. The base is situated on the Silver Strand, between the San Diego Bay and the Pacific Ocean. NAB Coronado is a major shore command, supporting 27 tenant commands, and is the West Coast focal point for special and expeditionary warfare training and operations. The amphibious base houses Commander Naval Surface Force, US Pacific Fleet, responsible for the training, maintenance and crews of the approximately 90 ships of the Pacific Fleet and Commander Naval Special Warfare Command, US Pacific Fleet. Also located there are most of the Naval Expeditionary and Naval Special Warfare units of the Pacific Fleet as well as the famed Navy Parachute Team, the Leap Frogs."

And here's the design the architect chose for the building:

You find it also on Google Maps.

Source: Google tracks Hitler to San Diego, and my office mate.


Monday, December 18, 2006

The Lion sleeps tonight

Look at this cute video that my mum just sent me!

Isn't this just a totally amazing animation? (Google video has a version with slighly better quality, see here -- it's not exactly the same version as I just noticed).

Also nice is the string backlash, and the joke of the day :-).

The name of the guy who made the videos is Pierre Coffin. You find some more info on this website. You can stop that site from quacking by clicking on the ouch-button...

Sunday, December 17, 2006

300 years ago: Émilie du Châtelet born in Paris

In case you are French and want to read Newton's Principia in your language instead of the obscure Latin, you can resort to a translation, Principes mathématiques de la philosophie naturelle, that has been prepared by a very remarkable woman, Emilie du Châtelet, who was born 300 years ago, on December 17, 1706.

Emilie was the daughter of an aristocrat at the court of the Sun King, Louis Nicolas Le Tonnelier de Breteuil, and had the chance of being educated at home, instead of spending the time until her marriage in a convent, as it was then the custom for girls of her family background. She was very interested in mathematics and the sciences, and managed to get lessons by a young académicien named Maupertuis, of later fame for the formulation of the principle of least action.

Gabrielle-Émilie Le Tonnelier de Breteuil, Marquise du Châtelet (

For a long time, she has been known mainly as the companion and lover of the philosopher and writer Voltaire, with whom she shared many interests, literature, drama and opera, and - physics. Indeed, Voltaire had spent some time in England before, where he had learned about Newton's work and became fascinated by the simplicity of the universal law of gravitation and Newton's laws of motion. He had written about this, among many other things, in his lettres philosophiques, and was about to prepare a long, popular exposition of Newtonian physics, the Elémens de la philosophie de Neuton, when he met Émilie.

The frontispiece to Voltaire'’s Elémens de la philosophie de Neuton, with Émilie du Châelet illuminating Voltaire with the light of insight coming from Newton (Rare Books Division, New York Public Library). The Elémens saw 26 editions between 1738 and 1785 and contributed enormously to the popularization of Newtonian physics in France.

Praise of England in the letters philosophiques had stirred some trouble for Voltaire in Paris, so he was especially happy when Émilie invited him to her husbands manor, the Château de Cirey, far away from the capital, and close to the border of Lorraine, which was not part of France at that time.

At Cirey, they spent happy and very creative and productive years together. They established a small theatre in the castle, and a physics laboratory. Here, they conducted experiments on the nature of fire, preparing contributions to a contest organized by the French Academy of Sciences.

The Château of Cirey-sur-Blaise in eastern France ((

Émilie continued her studies of maths and physics, under the guidance of Clairault and the German mathematician König. She started to write a textbook on physics intended for the education of her 12-year old son. The result, the Institutions de physique, was praised as an excellent exposition, but over the head of most of its potential readers. It contained a discussion of Leibniz ideas and his concept of vis viva, the living force, which we know today as the kinetic energy. It's hard to imagine now that it took several decades of intense debates before the concepts of conservation of linear momentum and kinetic energy in simple mechanics were neatly formulated and firmly established. Anyway, Émilie's exposition of what we now call kinetic energy, the quantity proportional to the square of the velocity - is the reason that she is marketed sometimes as a direct precursor of Einstein and his famous formula E = mc2.

In 1745, she embarked on her largest scientific project - the translation of Newton's Philosophiae naturalis principia mathematica, based on the third Latin edition from 1726. She managed to finish this tedious work just days before her death, too early and under quite dramatic circumstances in September 1749.

I find it difficult to gauge her scientific achievements, not the least because of the big time lag since the days of the enlightenment. She didn't contribute lasting original research, it seems, but her expositions and writings most probably was instrumental in the shift of the center of gravity in mathematics and physics from Newton's England to France - Laplace, one of the most prominent of the French mathematicians of that time, was born in the year she died. Anyway, La Marquise du Châtelet was a very remarkable woman, and her life demonstrates in a wonderful way how science can be and should be part of general culture.

In France, at least, it seems that she has become kind of a celebrity at last, honored at her tricentennaire as the first woman scholar - there is even a nice children's book about her.

There are several places on the Web to read more about Émilie du Châtelet, e.g.

Passionate Minds by David Bodanis is a recent biography about her.

About the vis viva controversy, there was an article in the October 2006 issue of Physics Today, see e.g. here.

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Saturday, December 16, 2006

The National Data Book

The US Census Bureau has released the 2007 statistical abstract. "The Statistical Abstract of the United States, published since 1878, is the authoritative and comprehensive summary of statistics on the social, political, and economic organization of the United States."

The full report with all tables has roughly 1,400 pages, and is available online. You find the abstract on this website.

Some interesting statistics:

  • The 2005 population of US residents is ~ 296,410,000 (Table 2).

  • The number of admitted immigrants increased from 2004 to 2005 and exceeded the level from 2001, after a significant drop in 2003 (Table 6).

  • 15.7% of US citizens (11.2% of children) have no health coverage (numbers from 2004). The rate of non-covered persons is the highest in Texas (25% total /21.4% children), followed by New Mexico (21%/15.3%) and Florida (19.9%/15.1%) (Table 145).

  • The most dangerous home furnishing item is the bed. In 2004 it caused 518,441 injuries. Also interesting: 121,094 people suffered injuries caused by their footwear. The statistic counts emergency room treated cases nationwide in 2004 (Table 173).

  • The number of reported cases of AIDS decreased slightly from 2003 to its 2004 value of 44,108 (Table 175).

  • South Dakota is the only state that did not report any case of Syphilis in 2004 (Table 176).

  • The percentage of current cigarette smokers decreased from 2000 to 2004, the average value in 2004 was 20.8%. From the listed groups, black women have the lowest percentage (16.0%) of smokers (Table 191).

  • 7.9 % of US citizens age 12 and older classify themselves as 'current users of illicit drugs'. The caption says 'Current users are those who used drugs at least once within month prior to this study'. (Table 194)

  • 65.3 % of US citizens are overweight. The statistics I printed has a chocolate smear. (Table 198).

  • 2004 in the land of plenty: 13,494,000 households in the US were food insecure. The number of households with hunger among children raised from 0.5 % in 2003 to 0.7 % in 2004 (Table 2004). Though recently the department of agriculture has defined hunger as a non-existent state, see also 'Very low food security'.

  • The average US citizen consumed 24.6 gallons of coffee, and 25.2 gallons of beer in 2004 (Table 201).

  • 74.1% of doctorates in physical sciences (astronomy, physics and chemistry) are male, 42.0% are foreign citizens, 79.1% are white (status 2004, Table 789).

  • In the last quarter of 2005, 22.5% of flights arrived late (more than 15 min) at major US airports. The worst airport is Newark International with 41.9% (Table 1055).

  • 6,894 people filed consumer complaints against US airlines in 2005 (Table 1056).

  • The number of alternative fueled vehicles in use increased slightly from 2003 to 2004 (Table 1075).

  • 42,636 people died in, or as a cause of car accidents in 2004 (Table 1083).

  • The median income of households in 2004 was US$ 38,453. The median income White only was $40,469, Black only $23,372. 15.5% of all households have an income under $15.000, and 15.7% have an income over $100.000. (Table 671 and 672).

  • The medium household income is the highest in Connecticut with $60,528, and the lowest in West Virginia with $31,504 (Table 687).

  • 36,997,000 people (12.7%) live below poverty level, status 2004 (Table 692).

  • The US counts 3,510,000 top wealth holders with net worth of $ 1 Million or more. Most of which live in California, followed by New York and Florida (Table 700).

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Friday, December 15, 2006

Beauty in Physics

As a postscriptum to my earlier post about The Beauty of it All, here is a photo of my latest painting. I made it after a sketch I took from Chanda's back during a seminar.

[Click to enlarge]

Yes, the lady on the photo is the same Chanda who also wrote the guest post at CV, see also my post about Diversity in Science.

The painting is 20'' x 24'', acrylic on canvas.

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Thursday, December 14, 2006

Global Cooling

Exactly one year ago, I visited Waterloo for the first time. I was standing in snow knee-deep, and the outside temperature was -15 C. Yesterday, when I went to work, the thermometer showed 8 C. How could I not be interested in climate change?! Here's what I read yesterday:

If you follow the news above, you'll see how the content gets gradually diminished. None of the articles above links to the actual meeting, nor do they properly reference the original paper they are talking about (the first one does at least mention the title and the journal). If you are interested, here is

The website of the AGU 2006 Fall meeting

And here is the original paper:

Climatic consequences of regional nuclear conflicts
Atmos. Chem. Phys. Discuss., 6, 11817-11843, 2006

A. Robock, L. Oman, G. L. Stenchikov, O. B. Toon, C. Bardeen, R. P. Turco

We use a modern climate model and new estimates of smoke generated by fires in contemporary cities to calculate the response of the climate system to a regional nuclear war between emerging third world nuclear powers using 100 Hiroshima-size bombs (less than 0.03% of the explosive yield of the current global nuclear arsenal) on cities in the subtropics. We find significant cooling and reductions of precipitation lasting years, which would impact the global food supply. The climate changes are large and long-lasting because the fuel loadings in modern cities are quite high and the subtropical solar insolation heats the resulting smoke cloud and lofts it into the high stratosphere, where removal mechanisms are slow. While the climate changes are less dramatic than found in previous "nuclear winter'' simulations of a massive nuclear exchange between the superpowers, because less smoke is emitted, the changes are more long-lasting because the older models did not adequately represent the stratospheric plume rise.


Wednesday, December 13, 2006



Want more? Click here to get one million and a quarter digits of Pi!

Yesterday, I read that the bible says Pi equals 3. Consequently I thought, gosh, somebody will insist to replace Pi with three in all schoolbooks, so they are in agreement with the bible. It didn't take me long to find out this was hardly a new concern, and has already status of an urban legend.

For the basics: Pi is the ratio of a circle's circumference to its diameter (in Euclidean geometry). It is named "π" because it is the first letter of the Greek words περιφέρεια 'periphery' and περίμετρος 'perimeter', i.e. 'circumference'. And it's not equal to three. In fact it's roughly equal to the long number shown above, the essential thing being the dots in the end.

But some more interesting info: Pi is a transcendental number, which means it can not be written as the solution (root) of a polynomial with coefficients in the integer numbers. This also implies that the number of digits after the point is infinite, they do never repeat, and every possible sequence appears at some point* (see here for the probability of finding some, and here for searching them).

Since this so far only explains what Pi is not, it seems some people are still concerned whether it actually exists. Well, this might sound somewhat philosophic, but I mean, you can't just write it down and say, there it is. The definition that I recall is that Pi/2 is the first zero of the sinus function. Which seems to me quite easy to prove that it exists (the function being smooth and having a sign change and all). If you don't want to use Euler's number for the sinus (another transcendental number), the sinus function can be defined as an infinite polynomial, which I would write down here, if latex could speak on my blog...

See also:

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Monday, December 11, 2006

A Tribute to my Granny

One of my favourite cookies are Kokosmakronen, not only because they taste good, but because they are quite easy to make. This is baking for the non-expert. For the sophisticated advises, I recommend Clifford's blog. For a recipe of a completely different kind see also: a paper recipe.


  • 6 egg whites
  • 400 g shredded coconut (unsweetened)
  • 300 g fine, white sugar
  • 1 pg vanilla sugar
  • 1 teaspoon salt


  1. make sure oven works1
  2. cut finger nails
  3. download Bing Crosby's White Christmas
  4. turn on iPod player
  5. turn off BlackBerry

The Making Of:

Collect ingredients. While doing so, smash an egg and bump your head on the cabinet when wiping up the floor. Also, make sure the digital camera is farther away than the average interaction distance of cookie dough (some meters).
Separate eggs. It's not as difficult as they told you. And it's not a cheese cake, so it's not so crucial. If shell drops in, don't worry. For reasons I don't fully understand I always find the shell pieces on the bowl rim later and can pick them out.
Beat egg whites thoroughly and patiently, until inscribed Greek symbols remain clearly visible. Keep in mind what my Granny used to tell me: back then in 19 twenty-something, they had to beat roughly one hour by hand. Those were the days...
Fold in vanilla, salt, coconut and sugar. If the result looks suspiciously liquid, add some teaspoons of flour or so. While the sky over Waterloo is covering your car with several inches of white stuff you'll have to scrape off tomorrow, whistle with Bing Crosby to I'll be home for Christmas.
Preheat oven to something in the middle range, but not too hot. Try to get the stuff on a baking sheet in small lumps. I recommend using two teaspoons. Leave at least 1 inch to each side. Oops, forgot to mention, better use some non-stick spray or something.
Make sure to put the pan lid on the front right plate, because it isn't tight and the oven looses hot air. Open a bottle of wine2. Put cookies into oven. Go to answer some comments on your blog, let cookies burn, get drunk and repeat procedure the next day.
Baking time is roughly 20 minutes, depending on your stove, the eggs, and the fine-structure constant. Kokosmakronen aren't really baked, but rather dried. Result should be light gold brown on the outside. If they got too hard or dry, put them in a plastic bag for some days. If they burn, break off burnt rim and use plenty of chocolate coating.


This post is dedicated to my Granny who tought me how to separate eggs, and who died at age 95 six months ago. Reaching such high age is definitly due to eating excellent Kokosmakronen each Christmas.


The author of this blog is neither responsible for potential hangovers, nor damage of stoves, mixers, digital cameras or other kitchenware.

Footnote 1: But don't touch the buttons.
Footnote 2: The white wine was a VQA Jackson-Triggs, 2004 Grand Reserve Chardonnay, Niagara Peninsula, which was fairly decent and recommendable.

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Sunday, December 10, 2006

Did you know... (III)

... why the toast is a toast?

Yesterday, I went to the groceries store and was greeted by an ad saying: It's the toast season! Okay, I wondered, what kind of a tradition is this? Do Canadians toast maple leaves on their bread or what? Upon second inspection however, (I think I need new glasses) the sign turned out to stand in front of the wine department.

So here is why the toast is called toast:

"The word derives from the Latin word 'tostare' (to scorch or roast - i.e. toast ). From Classical times it was common to flavour wine by floating small pieces of toasted bread in it. Sometimes these sippets would be flavoured with spices; at other times the carbon alone would mellow the wine."

Wikipedia clarifies appropriate toasting behaviour in the US and Canada, apparently written by someone who was tired of endless toasty speeches while he had to hold a glass of wine in mid air:

"The following guidelines apply specifically to toasting in Canada and the United States:

  • Most people will lightly touch glasses when giving a toast, often saying "toast", "cheers" or a short phrase such as "to us". Toasting without touching glasses is increasingly popular and is regarded by some as a slightly more sophisticated mode of behavior.
  • Except during formal occasions [...] it is not very common to "propose a toast" in the more formal sense. However, when someone does make such an gesture, it is almost invariably met with approval regardless of the setting or the occasion.
  • If someone wants to "propose a toast as well", this second toast should have a different focus than the first [...] Ideally, this toast is briefer than the first so as not upstage it. Subsequent toasts, if any, should even more succinct.
  • Americans and Canadians typically toast only once per gathering, if at all. Even lifting one's glass and saying "cheers" each time a new drink is poured isn't in line with local etiquette and, while not impolite, may be seen as a bit tedious."

Also: since it's the toast season, have a close look at your breakfast before you eat it. It might turn out to have heavenly messages on it. One of the most absurd stories I've heard about eBay is certainly that of the toast with the Virgin Mary face that has been sold for $28.000. Even though a bite is missing from it. What's even more absurd than this toast being sold for such an amount is that it was bought, not by a religious nutcase, but by an internet casino saying the toast had become a "part of pop culture".


See also: Make a toast in 50 different languages



Saturday, December 09, 2006

Deformed Special Relativity

My prediction about the number of comments on Joe Polchinski's review of Peter Woit's and Lee Smolin's books over at CV wasn't so bad, and they are still coming. I would like to use the opportunity to write about a topic I have been working on for some while, and which I believe was mentioned in the discussion, namely deformations of special relativity (DSR).

In May, I gave a seminar at UCSB about my recent work on the topic, which I have briefly summarized in the post The Minimal Length Scale. Since I recall that Joe Polchinski was present that day, I sadly conclude that the seminar wasn't very illuminating, so I'll try to clarify some things. In the beginning though, I should add a note of caution since my work on DSR is not in complete agreement with what the standard approach is. You find further details in my papers

To set the context, in the review Joe Polchinski writes:

    Smolin addresses the problem of the Planck length (“It is a lie,” he says). Indeed, Planck’s calculation applies to a worst-case scenario. String theorists have identified at least half a dozen ways that new physics might arise at accessible scales [6], and Smolin points to another in the theories that he favors [7], but each of these is a long shot. [...]

With reference to the footnotes:

    [6] The ones that came to mind were modifications of the gravitational force law on laboratory scales, strings, black holes, and extra dimensions at particle accelerators, cosmic superstrings, and trans-Planckian corrections to the CMB. One might also count more specific cosmic scenarios like DBI inflation, pre-Big-Bang cosmology, the ekpyrotic universe, and brane gas cosmologies.

    [7] I have a question about violation of Lorentz invariance, perhaps this is the place to ask it. In the case of the four-Fermi theory of the weak interaction, one could have solved the UV problem in many ways by violating Lorentz invariance, but preservation of Lorentz invariance led almost uniquely to spontaneously broken Yang-Mills theory. Why weren’t Lorentz-breaking cutoffs tried? Because they would have spoiled the success of Lorentz invariance at low energies, through virtual effects. Now, the Standard Model has of order 25 renormalizable parameters, but it would have roughly as many more if Lorentz invariance were not imposed; most of the new LV parameters are known to be zero to high accuracy. So, if your UV theory of gravity violates Lorentz invariance, this should feed down into these low energy LV parameters through virtual effects. Does there exist a framework to calculate this effect? Has it been done?

There is a reply to that question in comment #20 by Brett:

    I wanted to answer the question the question posed in [7].
    In short, this is a significant problem for any theory that predicts Lorentz violation. [...]

    The most explicit calculation of this that has been published is, I believe, in Collins, et al. Phys. Rev. Lett. 93, 191301 (2004). They take a Lorentz-violating cutoff and show how it affects one low-energy function. [...]

Which refers to this paper:
There follows a comment by Jaques Distler on Lorentz violation, some other comments, and comment #30 by Robert comes back to the question

    IIRC the way Lorentz violation is supposed to show up in loopy physics is that the dispersion relation is violated and the speed of light depends on energy (showing up in early or late arrival of ultra high energy gamma ray burst photons compared to ones of lower energy). The idea is that even if the relative effect is quite small the absolute size could be measurable as these photons have traveled across half the universe. Does anybody have an understanding of how this effect arises? [...] Which calculation this referes to? What do I have to compute to get this energy dependent speed of light?

Then, in comment #43, Joe Polchinski partly answers his own question:

    Brett #20,22: Thanks for the reference, this is certainly what I would expect. I understand that there is the hope for a `deformed algebra’ rather than a simple violation, but to an outsider it seems that what is being done in LQG is to return to pre-covariant methods of QFT, cut things off in that form, and hope for the best. It would be good to see some calculations.

Now let me add my comments:

The idea of deforming special relativity is to allow two invariant parameters of the transformations between reference frames. The one invariant is the speed of light, the other one is the regulator in the ultra violet, alias a maximal energy scale. This energy scale is usually identified with the Planck energy ~ 1019GeV. If one believes that the Planck energy acts as a maximal energy scale, then all observers should agree on this scale to be maximal. Since usual Lorentz transformations do not allow this (one can always boost an energy to arbitrarily high values), one needs a new type of transformations. These turn out to be non-linear in the momentum variables, which is the reason why they usually do not show up in standard derivations of Lorentz transformations, where one assumes linearity.

The construction of such transformations that respect the upper bound on the energy scale is possible, and they can be explicitly written down. The approach has been pushed forward notably by Giovanni Amelino-Camelia, who has written an enormous amount of papers on the topic. Unfortunately, I find his papers generally very hard to read and confusing. A very readable and clear introduction that I can recommend is e.g.

These theories do not break Lorentz invariance in the sense that they do not single out a preferred restframe. Instead, the Lorentz transformations (as functions of the boost parameter), are modified at high values of the boost parameter. This allows the maximal energy to be an invariant quantity. You can find an explicit example for such transformations e.g. in gr-qc/0303067, Eq. (19). What is deformed in this approach, as far as I understand it, is not the algebra itself, but the action of the generators on the elements of the space.

A deformation of Lorentz invariance consequently leads to a new invariant scalar product in momentum space, which means one has a modified dispersion relation. Under quantization, the approach is also known to imply a generalized uncertainty principle, which stems from the modified commutation relations. Theories of this type can but need not necessarily have an energy dependent speed of light (for details about these relations see e.g. hep-th/0510245).

In contrast to this, the paper mentioned by Brett in comment #20 by Collins et al explicitly examines a scenario with violation of Lorentz invariance. As they state already in the abstract "Here, we explain that combining known elementary particle interactions with a Planck-scale preferred frame gives rise to Lorentz violation at the percent level, some 20 orders of magnitude higher than earlier estimates[...]" I am reasonably sure this was not the scenario Lee Smolin is referring to in his book. I vaguely recall he actually writes something about Giovanni -- it implied a knife being put on somebodies throat or so. Unfortunately, I lent the book to my office mate, so I can't look it up.

If one introduces a hard cut-off in a momentum integration without making use of a modified Lorentz-symmetry one runs of course intro problems. With the use of deformed transformations however, this problem can be circumvented. A good way to think about it is in my opinion to picture momentum space not as being a flat, but a curved space. In this case, the integration over the volume in one or more directions can be finite. The non-flatness of the space shows up in the volume element via the square root of the determinant of the metric tensor, which can improve the convergence of loop integrals. By construction, the integration is invariant under the appropriate transformations in that space. In this approach, it is exactly the additional factor (square root of g) in the volume element that makes the integration invariant.

Another way to think about it is to consider a non-linear relation between wave-vector and momentum, in which case the role of the convergence-improving factor is played by the Jacobian determinant of the functional relation between both, see e.g. hep-ph/0405127.

A quantum field theory with DSR can be formulated as a theory with higher derivatives in the Lagrangian (see e.g. hep-th/0603032, or gr-qc/0603073). In fact, as I like to point out, in a power series expansion one needs arbitrarily high derivatives, since a finite polynomial could never reproduce an asymptotic limit. If one writes down a series expansion to get an effective theory, one has corrections in higher order interactions suppressed with powers of the Planck mass as one would expect. Each of these terms is Lorentz invariant, provided the quantities are transformed appropriately. However, in my opinion, such an expansion is not so very helpful, since the important thing is the convergence of the full series. These higher order terms come with the usual constraints on the interactions. I also don't see a point in examining them in great detail, since we don't know anyhow what other funny things might happen to the particle content at GUT or Planck scale energies.

The status of a full quantum field theory with DSR is presently unfortunately still very unsatisfactory. It is a topic I am working on myself, and I am very optimistic that there will be some progress soon. It is however possible to make some general predictions, using kinematic arguments, or just by applying the modified transformations. As mentioned by Robert above, the time of flight being energy dependent (in the case of DSR with an energy dependent speed of light) is an example for such a prediction. Some details about this can be found in

My interest in DSR arises from the fact that it is based on a very general expectation that we have about quantum gravity, which is that the Planck energy acts as a regulator in the ultra violet. In my works, I have mainly examined in how far it is possible to include this property into standard quantum field theories as an effective description of what should actually be described by a full theory of quantum gravity. I am not an expert as to how DSR is related to LQG, and how strictly this connection can be established.

Update: See also what the expert says.

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