On the Importance of Phenomenology

Quantum gravity has the potential to revolutionize our understanding of space, time, and matter and with it redefine our own place in the world. While my main interest is in finding the fundamental theory, I work on the phenomenology of quantum gravity because there is a need for it. The quest for a theory of quantum gravity is more than 75 years old, and though a lot has been learned along the way we are still waiting for a theory of quantum gravity that is connected to and confirmed by data. There is no way around phenomenology one way or the other; it is the necessary connection between theory and experiment. Here I want to reflect on the role phenomenological models have played in the history of physics and why they play an important role also in our search for a theory of quantum gravity.

If you know one thing about theoretical physics, it's Albert Einstein's name. While Einstein was inspired and guided by his contemporaries, both in theory as well as in experiment, his achievements are remarkable examples for the power of pure thought combined with mathematics. Einstein is not the only example; Dirac's equation that describes relativistic particles with spin 1/2 is another case where an axiomatic approach lead to predictions that were later confirmed by experiment, leaving us in awe of genius and the beauty of equations.

In the history of science these examples are however rare, and it is exactly because of their rarity that they impress us. An axiomatic approach towards the reconciliation of general relativity and quantum mechanics will, I am sure, if pursued vigorously, eventually lead to success. But the question remains if pure thought is sufficient to find the right starting point, for there might be more than one, some of which leading to theories incompatible with observations. And an axiomatic top-down approach brings with it a heavy load of developing mathematical tools along the way, detours to insight that can take a long time. In the history of science, physicists have often taken the freedom to go ahead and write down phenomenological models that were indeed not justified by any solid basis. And while rightfully met with skepticism, again and again they have been successful with it, thereby helping along the development of more and more fundamental theories.

The above mentioned example of Dirac's equation an instructive one. In the non-relativistic limit, Dirac's equation in the presence of an electromagnetic field reduces to the Pauli-equation which describes the coupling of electrons to electromagnetic fields with a gyromagnetic ratio of 2. It was derived by Dirac from his equation in 1928, but already in 1925 two Dutch graduate students, Samuel Goudsmit and Georg Uhlenbeg, had used a phenomenological model to describe the structure of atoms and the response of ions to magnetic fields. Their model did not make much sense since, classically, the gyromagnetic ratio should be one. Naturally, many physicists were not convinced by the model and Pauli even advised the students not to publish it. Yet, it described experiments well and Dirac's later derivation of their model from his equation served to document the validity of Dirac's theory.

Another example is Pauli's exclusion principle, according to which no two fermions can occupy the same state. It was postulated and used since 1925, among other things to explain the Zeeman effect. Yet it was not until the development of quantum field theory and an understanding of the properties of multi-particle states in 1940 that a derivation was achieved.

Coulomb's law, Ampere's law and Biot-Savart's law can be derived from Maxwell's equations, but they were known and in use long before that, significantly contributing to the development of the full theory of electrodynamics. Fermi's theory we know today is an approximation of the electroweak gauge theory, but was in use long before that, teaching us lessons in renormalizability. The Rahleigh-Jeans law and Wien's law for the spectrum of thermal radiation were combined in Planck's law. In 1900, Planck constructed a derivation for this radiation spectrum based on the, back then unfounded, assumption that the energy of photons is quantized and proportional to the frequency. It predated Einstein's explanation for the photoelectric effect by 5 years. The constant of proportionality that Planck introduced is now called Planck's constant and it was the starting shot for quantum mechanics.

Due to the difficulty to analytically describe the formation of bound states in Quantum Chromodynamics (QCD is asymptotically free, ie it's easier to deal with it the higher the energy) still today most of the models used are phenomenological and many predate the development of QCD. There is for example the the Nambu-Jona-Lasinio model, the Gell-Mann-Levy model or the String-Lund model, all of which have significantly contributed to our understanding of the structure of elementary matter.

One could at this point speculate which present day phenomenological models will turn out to have lead the way towards the now searched-for theory describing the fundamentals of space and time. It springs to mind String cosmology and Loop Quantum Cosmology, searches for deviations from Lorentz-invariance, extra dimensions, or signatures of space-time discreteness. The models currently in use are not derived from a fundamental theory. Instead, they aim to incorporate and allow tests for specific features the fundamental theory might have, like additional dimensions or modified Lorentz-invariance. But these models, even if they turn out to be incompatible with experiment, are guides on our search for the correct theory. Guides that, after 75 years, we have good use for.

Interna

Lara and Gloria are now five months old. They have made a lot of progress in coordinating their movements. They can now grab and hold things, including other peoples' noses and glasses, and they try to hold their bottles and spoons. We've bought some first picture books and they look with big eyes at the images while Stefan and I practice Swedish vocabulary: En elefant, två körsbär, tre ballonger, fyra muffins... Yesterday, Gloria rolled over for the first time.

Stefan makes an admirable stay-at-home daddy, who has even taken on the pretty much futile task of folding my T-shirts and pairing my socks. I meanwhile am back sitting in seminars, talking physics over coffee, sorting though piles of papers. Unfortunately, I still seem to spend a lot of time on the phone with the social insurance who still hasn't paid a single cent of my parental benefits. It turned out that they mistakenly believed I had moved out of country. The good news of the week is that I received a letter confirming I am indeed still insured with them and hope now things will finally be sorted out. It's about time since my account balance has been monotonically decreasing since October and the pain at the pump is substantial.

If you're a parent it is almost unavoidable that friends send you all sorts of baby-related information. Here are some of the more interesting articles that I came across: If your baby sleeps more than usual, expect a growth spurt, Statistically, mothers of twins live longer than other moms (it's a correlation, not a causation), for women with jobs that require a high skill level, having children significantly reduces their average lifetime income, and Nature Jobs reports that the gender divide in physics spans the globe:

"Balancing motherhood and work continues to be the biggest career challenge for women. Carola Meyer, an investigator at the Peter Grünberg Institute in Jülich, Germany, and vice speaker of the German Physical Society's gender-equality working group, says that although institutes and funding bodies provide career breaks for people who wish to have children, such schemes don't necessarily ease the balancing act. Women hold 17% of the 42 positions at her institute — a relatively large proportion, says Meyer. Yet all are under 40 and have no children. Those who want to rise within the scientific community can't consider having children until they are established, she says."

That stinks like a self-fulfilling prophecy. Let me clean up the stink by a quotation from the (otherwise cute but unremarkable) movie "Little Miss Sunshine" (that I watched on a flight on the way to some conference):

"Do what you love, and fuck the rest."

The cube of physical theories

Stefan has a lot of books. And most of them are about physics. The other day I picked a random book and opened a random page and saw myself faced with the "cube de théories physiques" (the cube of physical theories) in the book "De l'importance d'être une constante" by Jean-Philippe Uzan and Bénédicte Leclercq. You find a nice, though very French, illustration of that cube here. There is also an English translation of that book ("The natural laws of the universe: understanding fundamental constants") which has an English, though somewhat unsightly version of the cube on page 57. For your convenience, I've redrawn the illustration:



It shows a coordinate system with three axis that depict the values of three fundamental constants, G, ℏ, and 1/c – the coupling constant of gravity, Planck's constant and the inverse of the speed of light. To our best present knowledge these constants are indeed constant, but you can imagine varying them and ask what happens to the theory then. In many cases this corresponds to some physical limit. For example, if your theory contains terms in v/c, where v is velocity, then the limit of velocities small compared to c (i.e. non-relativistic) formally corresponds to taking c to infinity, ie 1/c to zero.

The cube seems to go back to Gamow, Ivanenko and Landau about a century ago, who allegedly cooked it up for a paper to impress a girl. It was rediscovered about 50 years later by some Russian guy named Okun, and then again by the Frenchmen who wrote above mentioned book. You can find here (PDF) a translation of the original paper by Gamow, Ivanenko and Landau, together with a comment by Okun.

You'd surprise me if you've seen that cube before. It is certainly not a particularly deep illustration, but it's inspirational and it gives you food for thought.

My trouble with popular physics books, though, is that in some cases you better not think about what you read because you might get terribly confused. That's what happened to me in this case.

To begin with it isn't clear to me what, physically, corresponds to varying G which is essentially the strength by which matter deforms the background geometry. It would seem more illustrative to e.g. take a constant with dimension of an energy density, so one could think of varying it as considering higher and lower energy densities. And taking the limit G to zero does decouple all the matter but doesn't actually give Special Relativity. Special Relativity is the limit of the vanishing of the curvature tensor or, equivalently, that of flat Minkowski space. Yet General Relativity has nontrivial vacuum solutions even in the absence of matter. These are Ricci-flat, but the curvature tensor doesn't necessarily also vanish. So there's something fishy about the front, lower left corner.

Also, it is to some degree of course a question of terminology, but what is usually referred to as the Newtonian limit of General Relativity is not the limit of velocities small compared to the speed of light. Instead, it is the limit of small distortions to the background, so there's something fishy about the back, upper left corner too.

What the nonzero value of all of these constants in the top, upper left corner has to do with a unification of all particle interactions is entirely unclear to me, and what the non-relativistic limit of that theory is good for I don't really know, though it arguably exists.

There is also the question whether taking these limits does actually commute, or if not approaching a corner does depend on the direction one is coming from. You can for example reach the corner with G and ℏ equal zero while keeping the ratio (the Planck mass) fixed. Or you can let them go to zero at a different pace so that the ratio goes to zero or infinity. It seems to me the difference should play a role, yet the diagram makes no distinction.

All together, the "cube of theories" is a very appealing representation. But do not wonder if it confuses you – it has to be taken with a large grain of salt.

Interna

So we've made it to Stockholm, but presently life is chaos. The plan was that I drive the household to Sweden by car and Stefan and the babies take a flight two days later so I can pick them up at the Arlanda airport. During packing however, we noticed the car was leaking oil and thought it was a good idea to have this checked in advance of a 1,500 km trip. Turned out the oil belongs to the servo steering and some broken hose would have to be replaced. I'm driving a Saab and the missing part had to be shipped from Sweden. By the time I wanted to leave, the hose was nowhere in sight. The mechanic advised us not to take longer trips. A cheerful Saab dealer however said not to worry, Autobahn is mostly straight driving anyway and who cares about the steering. I got a paper with the number of the broken part and a bottle of oil and he wished me good luck.

To his credit, I made it to Stockholm without problems. Problems started upon arrival. You see, I am living in a one bedroom apartment that's just about large enough for one person. The issue isn't so much lacking space as a lot of bulky, not to mention ugly, furniture of my landlord's wife that I can neither trow away nor sell nor move to the basement because the basement is full with her stuff too. The apartment has a second bedroom that the landlord told me last year he'd move out so we can use it as a nursery. Apparently he changed his mind about this some months ago and didn't bother telling me. The result is that now the four of us live in a clogged one bedroom apartment. One can't turn around without knocking something over and just hope that it doesn't hit a baby.

The internet wasn't working because the account hadn't been used for several months. The contract runs on my landlord's name and the company wouldn't give me the password. I tried to clean the apartment upon which my landlord's 20+ years old vacuum cleaner died with a small poof and a little black cloud and blowing a fuse. I sorted through a huge pile of mail that while consisting mostly of advertisement contains some serious looking påminnelse, and I know just enough Swedish to understand this means I should have done something long ago. I bought a new vacuum cleaner on the way to the airport.

The babies' first flight went well though Stefan reports Lufthansa staff wasn't very helpful. Since the baby seats don't fit on the baggage carts, he actually had to carry both babies and two bags to the gate. The apartment complex I live is gated and when we came back the gate was open. I dropped Stefan, the babies and the vacuum cleaner in front of the door and then found the gate locked on the way out. I noticed then that the key my landlord gave me didn't fit. I jumped upon the next person that came along, but she didn't speak English. After a considerable amount of time, I finally managed to find someone to let me out just to notice that I couldn't park the car in the garage because they were doing some repair. Stefan later found out that I did have a key to the gate, just that my landlord mixed up the labels and the key to the gate was labelled with 'basement.'

Inspecting the fuse box, Stefan reported he'd last seen these things in the late 70s. We spent a full hour searching for spare fuses and found them on the fuse box. Stefan drove to IKEA to get beds for the babies. I noticed that while they do sell in Sweden the formula we're using, they have different labels. Last time I tried to give Lara a different formula she actually refused to drink it, so I meant to call customer service. Just that, without internet, I couldn't find out the number. I had to call my mother to look it up. The winner of the day is the Hipp customer service that actually has human beings taking calls, and a friendly woman answered my question before I had even finished it. (The German A1 milk is the Swedish E2.) The German mobile phone company sends a warning about my roaming fees exceeding EUR 100 this month. A stressed daddy doesn't properly fit the diaper and Lara pees all over her cloths.

Between humoring the babies, changing diapers and noticing we have no diaper pail, unpacking my boxes and trying to fix a leaking tap, I called the social insurance to ask them for the umpteenth time why I still haven't received my parental benefits. A very confused sounding women told me that might be because I'm not registered with them anymore. Didn't I move out of country? (I think the next generation of cellphones should come with a little plastic pad to sink teeth into. Some of our baby toys have them too.) Having convinced her that I actually still live and work in Sweden, she said, well, but my husband doesn't. So they'll have to wait what the Germans do about his benefits. Just that the Germans tell us they're waiting for the Swedes to decide about my benefits. I must have left some impression on the women because she put something in my file that prompted somebody to call me back within 3 hours and assure me they're working on the case. But I estimate chances I'll have any money incoming to my bank account in the near future are slim.

Tried to take the babies for a walk. The twin stroller doesn't fit through the apartment door.

Late May in Sweden the days are very long. Being used to sleeping in the dark, the babies and me were up at 4am, hoping this day won't be quite as messy. Despite the mess, I'm looking forward to going back to work on Monday. Oh, and I wrote a paper. On the foundations of quantum mechanics, no really. I'll upload it sometime next week.

Basically, this is just to explain why I haven't done any substantial blogging for a while. But at least the internet connection is working again. Have to go change diapers now...

Filter bubbles

Our democracies rely on informed decision making. The internet is an asset when it comes to sharing of information, but as with any tool it needs to be used properly for the desired effect. The problem today is that we have too much available information and in order to make any sort of decision - and in order to find time to eat and sleep - we need to filter this information. From an evolutionary perspective, this is not a new problem in that our brains constantly filter information and only process the most relevant parts. That has advantages and disadvantages. What is new about the filtering we need for online information is that the filters are designed by some software engineers rather than by Nature, and they haven't proven their usefulness during thousands of years.

The risks that come with the filtering of information are a returning theme on this blog. In my post The Spirits that We Called I argued that the right filtering of information is crucial because people don't make a lot of effort questioning the order or relevance of information. If it doesn't come "cheaply," in the sense of it not requiring time and effort, it's likely to have low impact, thus the importance of search engines and social networks for democracy. From an evolutionary perspective the limiting of time spent on information gathering is just a careful dealing with resources and not irrational at all. That has always been the case, but the internet vastly centralizes provision of information and amplifies its impact at the same time. The consequence to draw, as I argued in my post Can Technology make us happy?, is that we should be very careful with designing information structure and filters. Do we really get the information that we need? One of the biggest problems, I think, is The Illusion of Knowledge that leads people to believe they have all the relevant information already.

Some days ago I saw the below TED talk by Eli Pariser, who makes this point extremely well. If you have ten minutes of time, they are well spend on the below video.

On the measurement of happiness

You might think it's the individual's pursuit of happiness that is the driving force behind our societies' dynamics, the progress as well as the regress. At least I thought that for a long time. And then, some years back, during a talk by Stuart Kauffman, it occurred to me this doesn't make sense and, worse, it's actually not true.

It doesn't make sense because from an evolutionary perspective the driving force is survival. It just happens to be beneficial for your survival if you're happy about actions that eventually produce healthy offspring. But if you think about happiness as some biochemical reaction it's not an end unto itself: For keeping your body supplied with energy it's actually irrelevant if you like eating. The reward circuit that triggers dopamine release is just a handy neurological tool to memorize the dos and don'ts. And you don't have to look far to figure that people don't make decisions to optimize happiness in the first place. There are, just to pick one example, many studies showing vicinity to nature (forest, parks, beach etc) improves not only people's self-declared happiness but also their health and life-expectancy. Yet, most people live in cities and spend their time indoors. Why?

In the wealthier nations on the planet, word has it that money doesn't make happy and even politicians and economists have come around to seeing that the GDP is far from measuring well-being. British Prime Minister David Cameron has set out to measure the Brits mood by means of a national happiness index, the French too have created a Commission to assess happiness, and residents of Somerville have recently been asked to fill out a questionnaire about their life satisfaction. We will certainly see more efforts into this direction. But this left me wondering. What quantity it that the Brits, the French, the Americans aim to optimize here? And do we really want that?

I'm not an economist, but I know so much as that the question how to optimize collective happiness is not new to economists. If you want to determine the "national well-being" you inevitably have to sum, or aggregate in other ways, different people's happiness. Yours and mine and that of my babies. And do they all count the same? How does your happiness compare to mine? How many ways are there to aggregate, and which one is the right? How do you, objectively, measure it? Can you at all?

People have tried, and are trying, seriously, to determine the amount of happiness as a neurological reaction, a red on an fMRI or a peak in a hormone level with the aim to eventually determine a 'true' value of stuff essentially. Yet 100 years ago most economists abandoned an inter-individually comparable happiness in favor of a measure of preferences that cannot and, interestingly, doesn't have to be compared between you and me. They call it the utility function.

The utility function works well on an individual level, but leaves an ambiguity among different possible optima as to which is the collectively preferable one. The aggregation would necessitate a 'social welfare function' which is basically the weight for everybodies' happiness in order to sum it up and it is ambiguous - call it the measurement problem of economy. Lacking a rationale for one particular choice, for the hard-core neo-conservative it's a capital DONT. And, from a theoretical basis, a justified one. But all these attempts to measure happiness then bring us back to this century-old question: What do we want? And what's the rationale for it?

To illustrate the problem, consider you are redistributing money from the rich to the poor. You do it on the premise that taking $10 away from a billionaire will decrease his happiness less than it will raise the happiness of a starving child in Africa. But how do you know if you can't compare their happiness? And if you would indeed measure their brain activity should the ability to produce high dopamine levels, that is to some extent genetic and age dependent, affect your decision?

In all this discussion, nobody ever questions that it is actually happiness that we want. But beware the self-evident assumptions for I am here to disagree. So I argue what we are really pursuing both individually and collectively is not happiness, it is the maximization of possibilities. Money doesn't make happy. It opens possibilities. You don't move to the city because it makes you happy, but because it opens doors, increases the number of available mates, and enriches your nightlife. The relevant point is that the number of possibilities is not weighted. It's just a number. You can add it and you can compare it. So here's the rationale for giving the tenner to the starving child. The billionaires' options are hardly affected. Yet the money has a large impact on the child's health and education. It opens a large number of future possibilities, more than it closes for the billionaire.

You can find a writeup of my thoughts on the Social Science Research Network (that's the humanists' arXiv):

On the Problem of Measuring Happiness
http://ssrn.com/abstract=1754423

Hello from Perimeter Institute

Sorry for the silence. I seem to have caught a stomach bug on the trip to Canada and spent the better half of the week commuting between bed and bathroom. I'll call it the Air Canada diet. Nothing quite like it to get rid of that excess pregnancy weight.

The construction at Perimeter Institute has been progressing well. The new part of the building is supposed to be finished sometime early fall or so, and I hear they're still on schedule. (See here for the photos from last year.)




The main entrance to the building is well hidden between fences, walls, and various dangerous looking machinery. Its location seems to be changing by the day like some secret code. The reception has been replaced by a study area, the bistro is now in the lobby, and staff features some new, unfamiliar faces. Still, after the last year's many changes in my life, it is comforting to come back and find things are still like they've always been. People are still talking about spin foams and black holes and their favorite interpretation of quantum mechanics. They still drink too much coffee and on your way to Starbucks on a Sunday morning you might run into the director. Waterloo is really a small town and the physicists' universe is expanding while they're orbiting around the center of their own gravity.

Interna

I am flying to Toronto on the weekend and will be visiting Perimeter Institute the coming two weeks. Since Superdaddy will be terribly busy and need all four hands for cleaning baby butts, and I'll be jetlagged and otherwise try to figure out what to write in the visit report, you're facing a slow time on this blog. When I'm back, Stefan, the babies, and I will pack our bags for we are spending 6 weeks in Stockholm so I can go back to work, at least temporarily.

Lara and Gloria are now exactly four months old. They are holding their heads well and grab everything that comes sufficiently close to their nose. They are also both trying to roll over, but haven't really managed yet. Lara is still the talker and Gloria is ceaseless in her daily workout. It seems that whenever I look at her, she's frantically waving her arms and kicking her legs. We've made some first attempts at spoonfeeding and were reminded that beta carotene is not water soluble.


The babies' paperwork is adding up. They're now registered also with the Swedish tax offices and have their own person-numbers. It turns out I'll have to apply for their residency in Sweden, so more forms waiting to be filled out. For the flight to Sweden, the girls got their own passport for which we had to get biometric photos. Even the babies manage to look like criminals on these photos.

So you want to get a PhD?

... then here's some things to consider:

The recent issue of Nature has a News Report "The PhD factory - The world is producing more PhDs than ever before. Is it time to stop?" which summarizes the job prospects of PhDs in Japan, China, Singapore, USA, Poland, Germany, Egypt and India.

“In some countries, including the United States and Japan, people who have trained at great length and expense to be researchers confront a dwindling number of academic jobs, and an industrial sector unable to take up the slack. Supply has outstripped demand [...]”

The below graphic (from mentioned Nature News article), shows the distribution of academic post-doctorate jobs in science and engineering in the USA:
This shows the unfortunate trend towards more and more research done by scientists on temporary contracts that we talked about in my earlier post Short-term Thinking.
Germany by and large seems to be doing well as far as job prospects are concerned, though few PhDs remain in academia:

“[In Germany] just under 6% of PhD graduates in science eventually go into full-time academic positions, and most will find research jobs in industry [...] The relatively low income of german academic staff makes leaving the university after the PhD a good option.”

That agrees with my experience.

But back to the USA. One of the over-produced PhD-students from Illinois, Sergey Popov, has developed a model according to which top US universities have economic incentives to lower their standards, because the better their students' grades the better their students' job prospects and the better the university's reputation (and finances) in return. The Times Higher Education cheerfully titles Elite US students are securing top jobs 'despite being less gifted' and summarize Popov's model:

“Universities "choose [a] grading standard to maximise the total wages of [their] graduates". [Popov] said his theory suggested that grade inflation would be highest in top universities [...] the risk was that the process went so far that there were Harvard graduates in top jobs who would not have got an A at Illinois and who had fewer academic gifts and social skills than every Illinois A-student. This, he said, was not "socially optimal".”

Popov has his data online on a website called gradeinflation.com. His model is interesting but there doesn't seem to be sufficient data to tell how well it actually describes reality. Anyway, I'm sure though it will leave some people chuckling. Did I see you grin? Did I?

Actually, the Scolarly Kitchen reports that the whole higher education thing might just be the next bubble to burst! That's at least according to Peter Thiel, founder of PayPal:

“Thiel’s belie[ves] that higher education is the next economic bubble into which we’ve moved the air expelled from Web 1.0 and housing.”

The cited data shows that College tuition fees have increased 375% since 1982-84 (3 year average).

And Scientific American has an editorial, Dr. No Money about the unpleasant duties of those PhDs who dare to remain in academia:

“Most scientists finance their laboratories (and often even their own salaries) by applying to government agencies and private foundations for grants. The process has become a major time sink. In 2007 a U.S. government study found that university faculty members spend about 40 percent of their research time navigating the bureaucratic labyrinth, and the situation is no better in Europe. An experimental physicist at Columbia University says he once calculated that some grants he was seeking had a net negative value: they would not even pay for the time that applicants and peer reviewers spent on them.”

So you want to get a PhD...

Robert Bosch Foundation: Seven points to improve research

In the aftermath of the plagiarism affair that led to the withdrawal of German defense minister zu Guttenberg's doctor title and, eventually, his resignation, the Robert Bosch Foundation invited a panel of experts to formulate ways to improve the conditions under which research is conducted. The outcome is a seven point paper "to assure integrity and quality in scientific research." You can download the paper (PDF) here. Since it's in German (and I realized Google translate doesn't cope well with academic-style German), here is a rough translation:

(All awkward grammar is entirely my fault.)

"1. Mitigation of publication flood

The number of publications around the world should be reduced (relative to the growing number of scientists) and thus - against the economic interests of publishers - also the number of journals. This is the only way to ensure that this important basis for assessing the quality of research will again consist of reflected and carefully evaluated results. And only then researchers will be able to again take sufficient note of relevant results and findings from their field.

2. Basic insights need permanent funding

Science needs durable and reliable funding, because the search for something new and for an increased understanding of nature follows radically different laws than a commercial enterprise. Of course academic institutions have to deal responsibly with their funds. We have to vehemently object however the expectation that academic institutions have to make direct financial profit or are evaluated by strongly economically oriented criteria. Rather, we should work together, even more than is already done today, to highlight the high intrinsic value of knowledge gain for the general public.

3. More emphasis on the content of scientific achievements

In the allocation of research funds it should be content that is assessed, not mindless promises of success of practical implementation. The qualitative assessment of the scientific work of a scientist or a researcher should at least equal in importance the quantitative bibliometric performance indicators. The sheer number of publications is not a valid criterion.

4. Proscription of strategic authorship

Authorship of a scientific publication requires substantial contribution to the content of to-be-published work. Authorship has become a currency of science, which is rewarded with money. The system for performance-based allocation of funds should therefore carefully investigate the actual contributions of the authors and proscribe a merely strategic authorship without substantial participation.

5. Researchers must write their own research proposals

External funding is an important competitive component of the academic system. Due to the trend to demand very high shares of external funding, the pressure has increased so much that a professional application system has formed, one in which scientists no longer write the research proposals themselves, but, in extreme cases, agencies formulate standardized applications. But scientific concepts need to be written by the researchers themselves. Ghostwriters must not be tolerated, not even in composite applications where parts written by different scientists are often "smoothed" by agencies.

6. Transparency in the presentation of data collection

Science needs transparency, despite the increasing complexity. Rapid technological progress, together with an excessive competition leads to more complex, and difficult to verify experiments. Without transparent and accurate representations of data collection and the scientific approach undertaken, more mistakes and improbities occur which jeopardizes the substance of science.

7. Good research takes time

Development and implementation of sound projects are not compatible with short-term contracts. The pressure generated by short-term contracts leads scientists and researchers to carry out small projects with no substantial knowledge gain and to publish fragments. Only contract terms that offer, through sensible conditions, the possibilities to plan long-term projects (esp. for young researchers) allow the quality of research indispensable for international competition."

This sounds very Germenglish, even to me ;-) Gee, all these many-syllable words and convulated grammatic constructs. I had to look up "improbity," and I'm not even sure I know what the German translation "Unredlichkeit" means (literally it means "something one doesn't speak of"). In any case, I hope it's roughly understandable. I think these are all very good points. However, I wasn't even aware that ghostwriting of proposals is an issue, I've never heard of this.

Do you have anything to add?

You are Ein Stein

Earlier this year, Gideon Rachman asked in the Financial Times "Where have all the thinkers gone?" Contemplating the Foreign Policy list of the Top 100 Global Thinkers 2010 and comparing it to who might have been on that list 150 years ago, he finds today's "crop of thinkers seem[s] unimpressive" and it gives him "the impression that we are living in a trivial age." Rachman proposes several explanations for this impression of his. We may only recognize great thinkers for what they are when enough time has passed. We may not appreciate them as long as they are living, breathing things who burp and dye their graying hair. Today's intellectual giants may live in China and the Financial Times hasn't heard of them. Or, the times of great thinkers are over due to specialized networks:

"In the modern world more people have access to knowledge and the ability to publish. The internet also makes collaboration much easier and modern universities promote specialisation. So it could be that the way that knowledge advances these days is through networks of specialists working together, across the globe – rather than through a single, towering intellect pulling together a great theory in the reading room of the British Museum."

Jonah Lehrer from The Frontal Cortex speculates that the apparent dearth of intellectuals is due to the "lessened importance of the individual" because "the era of the lone genius is coming to an end," for which he cites a study showing that teamwork and collaboration is on the rise in modern research.

There's the obvious thing to say about Lehrer's argument. There has never been something like a lone genius. You don't contribute to a society's knowledge and well-being without being part of that society. Scientific research has never been done in intellectual vacuum. All the great thinkers had their friends, their correspondences, their mentors and colleagues. But maybe more important, that teamwork is on the rise doesn't lessen the importance of the individual. It just integrates it better and, truth be said, makes it less apparent. But either way, it is questionable that the number of peer reviewed articles from large collaborations has anything to do with intellectuals to begin with.

I think the reasons for Rachman's impression are more mundane. He is probably right with the suggestion that it is difficult to recognize a great thinker while they're still thinking. There's 7 billions people on the planet and all of them have something to say. A lot of them say smart things occasionally, some say smart things most of the time, but all that smartness may turn out to be bullshit anyway. Take that guy Kurzweil with his Singularity prediction for 2045. Chances are, in the year 2045 he'll be little more than a curiosity. And some people that today might appear completely nuts will turn out to be right on the spot. Time will tell, so give it time.

The only real possibility there won't be no intellectuals in the future (aside from stupidity spreading and progress stagnating) is that thinking indeed becomes truly collective. However, as I argued in my earlier post on Collective Intelligence, we are far from that. In today's collaborations knowledge is not emergent. It is not something that really happens on the collective level. It is simply an assembly of many small parts. Yes, the parts profit from the other parts' contributions and if you put a group of smart people together they can work with each others contribution faster, but it's still a piece-by-piece work.

The prototypical example for a system that is more than the sum of its pieces is a frog. If assembled correctly, it croaks and jumps and that's emergent features. The prototypical example for a system that is the sum of its pieces is lot of bricks. It gets you a wall, alright, and maybe even a house. But it doesn't actually acquire new abilities. Today's specialist networks are brick walls, not frogs. The thinking still has to be done by the individual. We're all just bricks in the wall.

"Ein Stein" is German for "a stone."

So what do you think? Do you share Rachman's impression that today's intellectuals are disappointing? And if so, what do you think the reason is?

Multiversing around

multiverse [noun]

From L. multus “much, many” and L. versare “to busy oneself,” lit. “to turn to.” Tech: A hypothetical collection of different variants of -> universes. Colloq: A large collection of no apparent purpose. Expl: “She has a whole multiverse of shoes,” “His essay received a multiverse of comments.”

I am considering to consider to read Brian Greene’s new book The Hidden Reality on the multiverse. On the pro side there’s a likely readable synopsis of an interesting topic. On the con side there’s two of Greene’s books in my shelf that I never finished reading. A writing therapy exercise I thought might be useful.

First, let’s get over with the terminology. Yes, multiverse is a disingenuous nomenclature. If the universe is by definition all that exists, then anything to the multiverse more than the universe does by the same definition not exist. But it’s moot to complain about terminology that has already become common use. What exactly the multiverse is depends on the context, but in either case it’s something that exists in addition to what the presently most widely accepted theories let physicists expect to observe. Some theories seem to imply the existence of “more,” of a multiverse of “more,” and that in other ways than “more of the same.”

Multi versus uni

The central question is what does it mean “to exist?” As a particle physicist I’d say something that can’t be observed doesn’t exist. (Observation doesn’t necessarily mean a direct interaction.) Talking about the “existence” of something that can’t be observed opens the door to fairy tales. Though my invisible friend disapproves, from a scientific point of view I am interested in the multiverse only if it’s observable. And even then my interest is very limited since I find the presently discussed possibilities of observation remote and implausible. But yes, there are versions of the multiverse that may have observable consequences. Eg. we recently discussed a paper on signatures of bubble collisions in eternal inflation, one possible multiverse scenario, and there’s Laura Mersisni’s superhorizon entanglement giving rise to the giant void, and related stories.

For the more entertaining part I’ll now take off my physicist’s hat (okay, it’s an Einstein wig really) and put on my hobby philosopher hat (if you really want to know, it’s actually a tea pot lid).

multiversal [adj]

From noun -> multiverse. Colloq: Of confusing variety. Expl: “By the year 2010, social networking had become multiversal,” “The promises during the election campaign were multiversal.”

A lot of effort has been spent on the search for a “Theory of Everything.” Commonly meant to be a theory unifying General Relativity with the Standard Model of particle physics, it is another misnomer in common use: It is unlikely that a reductionist approach will ever be able to actually explain everything, not in practice and maybe not even in theory. I will however refer here to a TOE in the more general sense as a theory that leaves us with no “Why” questions and reduces all of science to a question of “How” and, knocking on the teapot lid, I’ll refrain from pointing out that we can never know if we’ve found it.

What may such a TOE look like? None of the currently pursued approaches to grand unification or quantum gravity comes even close. Even if string theory or something similar would allow us to compute all the parameters in the Standard Model and in the ΛCDM model, and so on, Nobelprizes would be handed out for certain, but it would just move the Why’s elsewhere, for all these theories have other unexplained assumptions: Why are strings/ loops/ E8/ networks fundamental? Why causality? Why these initial conditions? Why quantization? Why a semi-classical or classical limit? Why matter? Why in fact anything instead of nothing?

For this TOE we cannot use an assumption that constrains the theory to reproduce observation. The only guidance eventually left is mathematical consistency. Most occurrences of the multiverse actually still have additional assumptions, but already the problem is the same: too many possibilities. If you don’t want to settle for a “just because,” a question without answer, an unexplained final cause, you have to swallow that all that can exist, according to current theories, does exist. That doesn’t answer the question, but it removes the need for an answer. That is, in a nutshell, the reason for the recurrence of the multiverse in various branches of theoretical physics: Mathematical consistency just isn’t enough.

(A probabilistic approach for the multiverse with the assumption that our universe is one of the common ones, trying to derive some features of our universe at least as probable, is a reentry into the question-room through the backdoor. It just rephrases the question why our universe is special and what theory allows us to derive the details, to the question why our universe is especially unspecial and what measure allows us to derive the details, and it makes additional assumptions about how to compute probabilities rspt. about the logic used etc. I’m not dismissing the attempts to define a probability measure on the multiverse as useless since sometimes looking at an old problem from a new direction is fruitful. But the attempt in itself isn’t actually progress.)

Mathematical consistency is not a strong requirement. The complex plane and holomorphic functions on it for example are mathematically consistent (unless you insist on some wrong theorem), so is linear algebra on n-dimensional vector spaces. What sort of a universe is that, you might ask. But if mathematical consistency is all that you’re left with, that’s what you get: Everything that’s mathematically consistent “exists” in the same sense as the world around us, a notion of “existence” not in agreement with that put forward by the strange person with the funny wig. This thought then brings us straight to Tegmark’s Mathematical Universe: All of mathematics is real, and all that’s real is mathematics. There is no distinction because there’s no other meaning to “existence.”

My problem with the Mathematical Universe is not that I dislike the idea of being made of math (whatever that might mean). In fact, I quite like the idea (up to a face factor). My problem is that for all I can tell it’s not of use for anything (oops, lid slipped off) and it is based on an assumption I don’t find particularly plausible: That humans in the 21st century have already found the language to describe the fundamental nature of reality.

Formal mathematics is a quite recent achievement in mankind’s evolution. Sure, its precision and usefulness in the description of nature is vastly superior to that of, say, the English language. But 50,000 years ago our ancestors have thought of their precise spoken language as the ultimate tool to describe nature, vastly superior to grunting and waving with paws. So how sure really can we be mathematics is so intimately connected to nature that nature is mathematics?

Versus multi

Now let us turn the argument around. Searching for a TOE we were ultimately left with mathematical consistency as only guidance and it’s not enough of a constraint. It offers too many possibilities and eventually doesn’t explain anything. Unless, that is, mathematical consistency is not the only requirement. (There is of course the requirement to reproduce observation, but that’s too pragmatic for my tea pot.) The only way to avoid a multiverse then seems to be that mathematics is not sufficient to describe the fundamental nature of reality.

So the options are: a) Accept a final cause. b) Accept the multiverse. c) Accept that there’s a way to describe nature better than with mathematics.

If you don’t like a) and b) and therefore have to sympathize with c) you are however left wondering what may describe nature even better than mathematics? Well, you can. Tegmark’s Mathematical Universe irks people because they believe there is a distinction between reality and mathematics, between platonic ideas and the world out there. The common point of view is that the math used in theoretical physics is a description of nature, but humans provide the map between reality and the math. It is possible that this mapping is itself a purely mathematical process. I can imagine there to be an algorithm that searches for mathematical definitions whose properties fit to observed data. Yet presently there is no answer to the question whether there is in fact such an algorithm able to do science like a human. Gödel’s incompleteness theorem is happily waving its tail, waiting for a chance to pee on your leg.

In summary this means if there is neither a final cause nor a multiverse, there likely won’t be any Singularity in 2045 either since no computer algorithm will be able to go beyond math. And vice versa, if a computer algorithm, coded in the language of math, is able to map every aspect of reality to a mathematical structure, then you’re likely stuck with the multiverse, Tegmarkian version, subsuming all other versions. It might then just be that the next revolution in physics comes from neuroscience.

multiverse [verb]

From noun -> multiverse. From L. multus “much, many” and versus, pp. of vertere “to turn.” To make many turns. Colloq: To act or talk incoherently. “She spent the afternoon multiversing around,” “His job interview was a disaster; he totally multiversed it.”

I’ll finish with a quotation from a wise physicist, who wants to remain unnamed but reportedly reads this blog: “The multiverse, the simulation hypothesis, modal realism, or the Singularity –it’s all the same nonsense, really.”

Citation Ponzi Sheme discovered

Berlin, April 1st 2011: The Federal Intelligence Service discovered a Ponzi scheme of academic citations lead by an unemployed particle physicist. A house search conducted in Berlin last week revealed material documenting the planning and administration of a profitable business of trading citations for travel reimbursement.

According to the Federal Intelligence Service, the hint came from researchers at Michigan University, Ann Arbor, who were analyzing the structure of citation networks in the academic community. In late 2010, their analysis pointed towards an exponentially growing cluster originating from a previously unconnected researcher based in Germany's capital. A member of the Ann Arbor group, who wants to remain unnamed, inquired about the biography of the young genius, named Al Bert, sparking such amount of activity. The researcher was easily able to find Dr. Bert scheduled for an unusual amount of seminars in locations all over the world, sometimes more than 4 per week. However, upon contacting the respective institutions, nobody could remember the seminars, which according to Prof. Dr. Dr. Hubert at The Advanced Institute is "Not at all unusual." The network researcher from Ann Arbor suspected Dr. Bert to be a fictitious person and notified the university whose email address Dr. Bert was still using.

It turned out Dr. Bert is not a fictitious person. Dr. Bert's graduated in 2006, but his contract at the university run out in 2008. After this, colleagues lost sight of Dr. Bert. He applied for unemployment benefits in October 2008. As the Federal Intelligence Service reported this Wednesday, he later founded an agency called 'High Impact' (the website has since been taken down) that offered to boost a paper's citation count. A user registered with an almost finished, but not yet published, paper and agreed to pay EUR 10 to Dr. Bert's agency for each citation his paper received above the author's average citation count at the time of registration. The user also agreed to cite 5 papers the agency would name. A registered user would earn EUR 10 for each recruitment of a new paper, possibly their own.

This rapidly created a growing network of researchers citing each others papers, and encouraged the authors to produce new papers, certain they would become well cited. Within only a few months, the network had spread from physics to other research fields. With each citation, Dr. Bert made an income. The algorithm he used to assign citations also ensured his own works became top cites. Yet, with many researchers suddenly having papers with several hundred citations above their previously average citation count, their fee went into some thousand dollars. On several instances Dr. Bert would suggest they invite him for a seminar at their institution and locate it in a non-existent room. He would then receive reimbursement for a fraudulent self-printed boarding pass, illegible due to an alleged malfunctioning printer.

Names of researchers subscribed to Dr. Bert's agency were not accessible at the time of writing.

Interna

Lara and Gloria are now almost three months old. They have doubled their birth weight and grown in and out of the newborn cloths. Gloria is smiling generously at all and everybody while Lara's smiles are reserved for special occasions. Stefan and I are glad they now make some sounds other than crying; their "ouee" and "agooh" are music to my tinnitus.

The girls can now almost hold their head, and they have begun to take note of the mobiles above their beds. Gloria spends hours waving around with her arms and kicking into the air, hoping to hit something. Lara happily talks to the wooden bees and butterflies above her head. Interestingly enough, the babies hardly take note of each other. When we put them both in the playpen, they completely ignore their sibling. They pay more attention to about everything else than they pay to their sister.

Responsibility hits you in funny ways. The other day it occurred to me with some months delay I should probably wash the babies behind their ears. If I don't do it, who will? And then there was the day when I misplaced the baby. I went to see if they're all right and found one bed empty. Since it was unlikely the baby had learned to walk while I wasn't looking, I probably took her someplace and then forgot. I checked the big bed and the babyseat and the playpen before I remembered I put her on the couch, where she was still sleeping peacefully. (But don't tell my husband.)

Stefan and I, we have meanwhile organized our lives with the babies pretty well, though we are still short on sleep. It didn't help that Europe switched to summer time yesterday. Today, Lara and Gloria seem a little confused that breakfast is so early. And I have learned to type two-handed while balancing a baby on my forearms.

What is mathematics good for?

Some weeks ago I asked my midwife what made her chose her job. She told me she had actually wanted to study medicine, but didn't meet the numerus clausus. Rspt she ranked place thirtythousandsomething. With an apologetic look at the shelves full with physics and maths books behind me, she added maths was her problem. She couldn't figure out what is was supposed to be good for.

She has a point there, I thought through endless repetitions of my pelvis floor exercises, and though it's hardly the first time I've heard this remark I started to wonder what role mathematics does really play in every day life. (Okay, I admit, what I really thought was it would make a good topic for a blog post.) Arguably, I need a lot of maths in my life because otherwise I'd be unemployed. But how much maths does the average person really need? And what do they need? And does school teach it?

You don't need to learn maths to survive. Otherwise mankind would have gone extinct long ago. Amazingly enough though, your brain performs some basic mathematics all the time, such as extrapolating the motion of moving objects. In an interesting experiment measuring the activity of neurons in rhesus monkeys, researchers from the University of Tübingen have found that different sets of neurons fire in response to the monkey seeing sets with different numbers of elements. Basically, there's neurons that are (primarily) activated by specific numbers. (See Bongard and Nieder, PNAS 107, 2277 (2010)). And it is known that people with certain brain injuries lose the ability to understand, compare, and deal with numbers, a disability known as acalculia. It does seem plausible then that dyscalculia, difficulties in learning and comprehending mathematics, is so some extend due to wiring instead of motivational problems. However, that's estimated to affect only a small percentage of the population. Most people who don't understand maths don't understand it because they've never really made an effort. Which brings us back to the question what's it good for?

Basic arithmetics is so universally useful that it benefits your selective advantage. Whether you want to know if you've enough money to fill up the tank, are worried that the baby didn't drink enough, or need to know how many bottles of sparkling wine to order for your graduation party, it haunts you everywhere. Beyond that, if you want to understand your average magazine or newspaper, you better know how to read a graph. And unless you want to blindly trust your financial adviser, percent calculation should be on your list.

Having come to this point, I Googled for "mathematics in every day life." The first hit was a long deserted blog with a handful of entries that, next to percent calculation, discusses symmetries in car logos and flowers. However, one doesn't need to know the mathematical definition of a group to plant a flower. Google further brought up a document I couldn't open, a file not found, a power point representation on photoshopping, and a Tutorvista question "How is maths used in everyday life?" with the reply "Math is used in time calculation, shopping, traveling, cooking, and all other important activities." All together not an impressive result. What is maths good for if not even Google knows?

School mathematics tends to drown pupils in 'real life' examples that no normal person will ever use in their real life. Yes, I sometimes add up the prices of items in the supermarket just for distraction, but it's arguably a pretty pointless exercise. Yes, it helps to know some trigonometry to figure out if the new furniture will actually fit through the door, but then you can rent furnished. And who really cares what's the volume of that piece of cake.

The real value of mathematics isn't that you can calculate what 500 sq ft is in international units, because Google does that for you. That, incidentally doesn't have much to do with maths anyway. Sadly, school doesn't teach children much about the beauty of maths, the value of logic, and the power of proofs. You don't need mathematics to live, but you need it to understand - for example Google's PageRank. What is mathematics good for? Mathematics is at the basics of science, including physics, computer science, and economics, examples are omnipresent in your every day life. Without mathematics, you're left in the fuzzy realm of storytelling. How can one understand the world without knowing what a differential equation is, without knowing what optimization is?

No, you don't need to know maths to plant a flower, to admire a night sky, or to like a crystal. But as in the arts, getting to know the artist and his techniques add to the appreciation and understanding of her work - may that be the Fermat's principle, data compression, self-organization, Noether's theorems or chaos. Mathematics is the language of Nature and learning it is your connection to the universe. No more and no less.

Since I acknowledge that the selection of maths taught at school is, sadly, suboptimal to this end, I set out to explain to my midwife that statistics is essential to understand the studies she's been telling me about and a doctor should indeed know what a standard deviation is. And being familiar with the exponential function might explain the funny face I made when she recommended some homeopathic remedy in D10. Things went downhill from there.

This and That

• APS's newest journal is Physical Review X (PRX). It's online-only, open access and accepted articles will be published upon payment of an article-processing charge of $1500. The website says the journal is "global." There's countries on this globe where $1500 makes an acceptable annual income. Just saying.


• Two years ago, we discussed Craig Hogan's papers on Holographic noise, and the shortcomings of his model. Hogan successfully postdicted the GEO600 mystery noise. After the noise turned out to be due to a readout error, Hogan found a missing factor in his calculation. According to the new calculation, the noise would not be seen at GEO600. Fermilab now funds a new experiment, called the Holometer, to test Hogan's model. The two papers listed on the website as reference are unpublished. Just saying.


• Am I the only one thinking "Frisch, Fromm, Fröhlich, Frei" when looking at the Fermilab logo?


• Zeitgeist: The US Air Force invites a professor of metaphysics to learn about the philosophy behind the nature of causality. Just saying...

Causes of women's underrepresentation in science

I always feel awkward if somebody brings up the topic of women's underrepresentation in physics. Though I'm one of these underrepresented women, I don't actually have a lot to say about the possible causes that hasn't been said a million times already. I'm not a social scientist and I'm not a neurologist and I don't follow the relevant literature. That leaves me with my own experience to talk about, but I generally dislike talking about myself. Also, exactly by virtue of being one of the aberrations I'm not the right person to ask why there aren't more girls studying physics.

I'm generally supportive of all these women's networks, especially those aiming at providing the all-important much talked about 'role models' for young girls - something that in today's overconnected world can be done without much effort - and groups dedicated to helping with issues that women are more likely to want to discuss (Breastfeeding in my office - do or don't?). I've on occasion participated in on or the other meeting and such, and I think most of these initiatives serve a good purpose in providing encouragement and connections to others in similar situations and can be very helpful indeed.

But thing is I get along well with my male colleagues and I have no reason to suspect any sort of systematic bias has conspired against me at any point. Of course one or the other guy is an asshole, but nothing surprising about that. Just that I know many of my female colleagues have made bad experiences and I don't want to do a disservice to them by saying I think much more important than gender bias is that the typical academic career is simply incompatible with many women's priorities. Do I have to spell it out? If you're lucky enough to get tenure, you'll on the average get there in the late thirties or early forties. If you're a man, you can then go marry a younger woman and start thinking about reproduction. If you're a woman, you better freeze some eggs in time if you want to wait that long.

Interestingly, I yesterday came across a paper examining the question if it's a bias against women causing their underrepresentation in science

Understanding current causes of women's underrepresentation in science
Stephen J. Ceci and Wendy M. Williams
PNAS February 7, 2011

In their paper the authors surveyed studies past the mid 80s on bias against women in manuscript and grant reviews and in hiring. They basically found that while there's the occasional outlying study claiming to have found a bias against women, these outlying results haven't been reproduced, and most studies found very little or no bias in either direction. (That is, one should add, after productivity has been corrected for by available resources since women are more likely to work in positions with limited resources which by itself is correlated with lower productivity.)

Now, as I said, I'm not an expert on these questions so it's hard for me to tell if their survey of available data is complete. But if it is, one should pay attention to their conclusions. They argue that looking at the evidence, or lack thereof, efforts to reduce gender bias are misdirected since there is already little or no bias to find. Instead, one should focus on making career options more friendly towards women's life plans so one doesn't unnecessarily lose them early. Quoting from a report on gender issues by the General Accounting Office and referring to the UC-Berkeley's "Family Friendly Edge" program, they suggest measures such as

"stopping tenure clocks for family formation and tenure-track positions seguing from part-time to full-time [...], adjusting the length of time to work on grants to accommodate child-rearing, no-cost grant extensions, supplements to hire postdocs to maintain momentum during family leave, reduction in teaching responsibilities for women with newborns, grants for retooling after leaves of absence, couples-hiring, and childcare to attend professional meetings [...], [Employer providing] high-quality childcare and emergency backup care, summer camps and school break care, [...] instruct[ions for] committees to ignore family-related gaps in CVs."

They kind of forgot to say that maybe most important is a decent maternity and parental leave to begin with, Sweden tells you how to.

Of course one should add it's not just women affected by this. Men who don't want to wait with having a family till they have job security and/or who have a partner not in the mood moving with them around the globe are in the present system also likely to drop out early. That's got nothing to do with hitting a glass ceiling. It's more like following the arrow that points to the open door.

Evolving Dimensions

That the space-time of Einstein's Special and General Relativity might not be fundamental plays a central rôle in our quest for quantum gravity. There are many possibilities how the fundamental structure of space-time may be different from the four-dimensional continuum; discretization and additional space-like dimensions are among those that have received the bulk of attention. No matter what the modification though, one has to make sure that deviations from the experimentally extremely well confirmed Standard Model of particle physics and General Relativity become important only at scales that we have not yet tested, typically at high energies or short distances.

The idea that space-time might not be higher-dimensional on short distances but instead be lower-dimensional has been around for some while, inspired by results from causal dynamical triangulation. In a paper last year, Anchordoqui et al proposed to examine the possibility of lower dimensionality at small distances for its phenomenology in their paper

Vanishing Dimensions and Planar Events at the LHC
Luis Anchordoqui, De Chang Dai, Malcolm Fairbairn, Greg Landsberg, Dejan Stojkovic
arXiv:1003.5914v2 [hep-ph]

Greg Landsberg gave a talk about this work on our last year's workshop on Experimental Search for Quantum Gravity (recording of the talk here). The basic idea is that the dimensionality of space changes with distance in such a way that it is 3-dimensional on scales we have tested it, lower dimensional on distances shorter than we have probed yet (about 1/1000 of a femtometer) and possibly higher-dimensional on distances larger than we can observe. The picture suggested is that of a (one-dimensional) string being knitted, and the knitted sheet (2-dimensional) being crumpled to a ball (3-dimensional). The authors dubbed this "evolving dimensionality." The merit of having a smaller number of space-like dimensions at small distances or high energies is that it improves the renormalizability of quantum field theories and esp. that of quantum gravity. (In contrast to additional dimensions which actually make the problem worse.)

The above paper as well as two recent follow-up papers, arXiv:1012.1870 [hep-ph] and arXiv:1102.3434 [gr-qc], looked at the phenomenological consequences of the evolving dimensions. Most interesting, they predict that at high energies the outgoing particles in scattering events should have an increased probability of being aligned in a plane. And the latest paper investigates the modification of the gravitational wave background. This modification is due to the early universe having been lower-dimensional if the idea is true, which would prohibit the propagation of gravitational waves. Both predictions are for all I know unique to this particular model.

But the question that springs to mind immediately is: What about Lorentz invariance? If one has a lower number of dimensions at short distances, these dimensions need to be oriented somehow relative to the four-dimensional continuum that must be reproduced at large distances. This orientation necessarily breaks Lorentz invariance. The problem is then that violations of Lorenz invariance are extremely tightly constrained already. I was thus curious to see how the model of evolving dimensions avoids these constraints.

The way this is achieved is that there is no model. Instead, it's in the authors words "not a concrete model, but rather a conceptual new paradigm." The papers offer pictures and analogies instead of a mathematical description of the new fundamental structure of space-time and the dynamics of quantum fields in it. The most recent paper addresses the issue of Lorenz invariance as follows:

"For random orientation of lower-dimensional planes/lines (see e.g. Fig. 2 ), violations of Lorentz invariance induced by the lattice become non-systematic, and thus evade strong limits put on theories with systematic violation of Lorentz invariance."

Unfortunately, this claim is not backed up by any argument and the figure does not represent a Lorentz-invariant random orientation. (The average spacings are approximately of the same size which is not boost invariant). From Causal Sets we know there are Lorentz-invariant 'sprinklings,' but these are sets of points and not distributions of planes. I also don't see from the picture if and how these planes end when they meet and it remains unclear how the length scales on which the dimensionality changes, supposedly a property of the space-time structure, is defined Lorenz-invariantly. Most problematic however is that the previous paper (arXiv:1012.1870) talked about the loss of energy into the background. This necessitates an interaction and that interaction should be described by an operator coupling the fields to the, oriented, background. I would then suspect this interaction falls among the already highly constrained Lorenz-invariance violations. It doesn't matter if these orientations average out on large distances if the effect that one looks for necessitates one is in a regime where one is sensitive to the distance it is not averaged out. This is very difficult to say though without a model.

However, in the recent paper on gravitational waves, one doesn't actually need Lorenz-invariance since one is concerned with cosmology and has a preferred frame - the restframe of the CMB - at hand anyway. So I wrote to one of the authors of the paper, Dejan Stojkovic from the University of Buffalo, who explained that they consider the model to be breaking boost-invariance but not rotational invariance. With that, the length scales on which dimensionality changes can be well defined without much effort. The question of Lorentz invariance violating operators however remains open. Dejan also readily admits that their new paradigm still needs work and explains how the first paper came about:

"I had this idea since 2003 while intensively working on higher dimensional theories. It crossed my mind that instead of making things more complicated at high energy (and hoping that the problems will miraculously disappear) we could instead make things less complicated - thus evolving dimensions (at short distances we have less dimensions, while at large distances we have more). However, I could not come up with a Lagrangian and would not dare to make it public.

Then at the meeting in Heidelberg, after diner and several beers, I told our friends, who intensively worked on extra dimensions, that the LHC is much more likely to find less rather than more dimensions, and after first 10 minutes of disbelief, they liked the idea and convinced me that in order to make a prediction rather than post-diction, the paper must go out NOW."

In summary: The idea of evolving dimensions is very interesting and makes predictions that are, for all I know, unique to this particular setting. At present it however lacks a mathematical model for the new fundamental structure and the dynamics of quantum fields in it.

This and That

• These are hard times for physicists working on supersymmetry. The LHC constrains the parameter space with so far no evidence for what has been the most popular model of physics beyond the standard model for decades. For details, check Peter's post on "Implications of Initial LHC Searches for Supersymmetry", Tommaso on "LHC Excludes SUSY Theories, Theorists Clinch Hands", and Resonaances on "More SUSY limits". Geoff Brumfield in Nature News titles "Beautiful theory collides with smashing particle data." Brumfield quotes Chris Lester, from the ATLAS collaboration: "We're painting supersymmetry into a corner," and Alessandro Strumia, a theorist at the University of Pisa in Italy:
  

  "Privately, a lot of people think that the situation is not good for SUSY. This is a big political issue in our field. For some great physicists, it is the difference between getting a Nobel prize and admitting they spent their lives on the wrong track."

  
  This week's Nature issue also has an editorial titled Dark Rumblings, comparing the LHC SUSY search to Michelson & Morley's search for the ether, arguing that "the negative results now coming out of the LHC should be just as stimulating as any positive findings." So if you've wasted 30 years of your life, don't forget negative results should be stimulating.


• The International Loop Quantum Gravity Seminar (ILQGS), a seminar series by telephone conference, now has a blog. Maintained by Jorge Pullin, it offers summaries of the talks in the seminar series.


• The Max Planck Society has a YouTube channel with short video clips about their research fields. While parts are only available in German, some videos are in English and worth checking out. The topics are as diverse as the Max Planck Society's institutes and of equally diverse quality. Interesting for example: GERDA, The Germanium Detector Array (on the search for neutrinoless double-β-decay), a bat catching a fly, or Honey, I shrunk Brad Pitt (on a video software for changing your waist and bra size.)

Societal Fixed Points

The extend to which one can construct a model for human society is a matter of dispute. Among the most common arguments why it might not be possible to build a testable model of the behavior of large groups of humans is that the elements of this model are conscious and self-aware and in contrast to, say, electrons, able to react to the proposed model. In the social sciences, this feedback into the system is called reflexivity.

There are many examples for this feedback indeed spoiling the predictions of a model. One of the best known is maybe the experiment conducted at Hawthorne Works from 1924 to 1932, where it was studied (among other things) how monetary incentives affect workers' productivity. Surprisingly, the productivity decreased. It has been suspected that this happened because the workers had heard of the study and were afraid an increase in their productivity would later result in lay-offs or a lowering of the base rate. Another example is Nobel-prize winners or other experts and authorities commenting on the economy. It is well known that consumer behavior is influenced by whether the outlook is pessimistic or optimistic, though in this case it's of course more difficult to identify the causes.

In any case, the argument that feedback necessarily spoils any model and thus such efforts are in vain has never made much sense to me. While this may be for some models, there's no reason a model can't remain unmodified under the feedback or that the feedback must be such to necessarily spoil the accuracy of the model. Take the previous example about a prediction affecting consumer behavior. If it's an optimistic outlook it (ideally) causes people to spend more. This doesn't spoil the prediction. On the contrary: it may turn it into a self-fulfilling prophecy. Or take the model of supply and demand. Most people know it, yet they don't go and buy the most expensive crap just to prove economists wrong. And why is that? Because they have no reason to. Instead, they believe everything is working in their favor as long as they continue to do what the model says they'll do anyway.

This of course lead me to wonder if there's fixed points in the set of models. There is arguably a trivial fixed point. That's the one when nobody knows of a model or nobody believes it, thus there's no feedback. But one could say it's not an attractive fixed point in the sense that it's unstable: The more successful a model is the more people will know of it and believe it. So, I'm posing the question to you: is there an attractive fixed-point? Because if there is one, that might be where we're going.