## Thursday, July 28, 2005 ... /////

### Background independence

Lee Smolin has submitted "The case for background independence", hep-th/0507235. Background independence is definitely an interesting topic in philosophy of physics. Some of Lee's points can be agreed with, for example:

• It is desirable to find a background independent formulation of string/M-theory
• Such a formulation would likely to answer the questions whether the landscape approach to string/M-theory is correct; why it's not; what it should be replaced with.

These are the anthropic topics and it has been described many times why I agree with Smolin and others. However, I can't agree with the other points about background independence, especially Lee's opinions that

• We should try to revive Leibniz's relationism or Mach's principle
• Philosophical reasoning about background independence is relevant for derivation of physics of a particular background
• It's better if your theory contains no space (possibly not even an emergent one) rather than if it does
• Quantum mechanics should be replaced by something else that goes "beyond it"

and many others that will be discussed in this text.

OK, let me start with the questions about relationism and Mach's principle. I highly recommend you the second popular book by Brian Greene, "The Fabric of the Cosmos", where the relative vs. absolute debate is covered in the first chapters. And the presentation is very nice.

What do I think about these issues? Unlike others, I have never been impressed by the relationist ideas and Mach's principle.

Leibniz's principles

## Wednesday, July 27, 2005 ... /////

### Rich aliens from strings

Totday, the India Daily Technology Team has informed the large Asian country that

• The superstring theory in contemporary physics proves the existence of parallel universe with many higher dimensions where advanced alien civilizations prosper.

Actually, this sentence is the title.

Rich aliens seem to be one of the first practical application of string theory; they may live in a new kind of landscape. ;-) Their existence has also been shown by "rich spectroscopy at the Large Hadron Collider", our Indian colleagues argue and demonstrate it by a photograph of a fully operational collider. After the article in India Daily, The Reference Frame is the second source that informs you about the great news - and moreover tells you that you should not accept the news uncritically. ;-)

## Sunday, July 24, 2005 ... /////

### Strings as Microsoft

This is my (first) reply to the discussion over at cosmicvariance.com under Sean's article called "Two cheers for string theory", especially the article itself.

There are many points in the text that I agree with and the author seems to have a remarkably sane idea what string theory is all about even though he is not a practitioner. There are other, more technical points, where corrections are necessary. Sean has not really considered the implications of the last 10 or 20 years in string theory but most of the non-professional readers of their blog misunderstand these implications as well, so it does not seem to matter and the readers are satisfied.

No doubt, it would be more encouraging if more than string theory as of 1985 presented by a non-string-theorist was needed for a full satisfaction. But one should not forget that there are many people, often outside the blogosphere, who care about the difference between string theory as of 1985 and 2005.

String theory is Microsoft of quantum gravity. Unlike Robert, I have no serious problems with this comparison. Microsoft is more about success and competition while string theory is about the lasting intellectual value. But the degree to which string theory dominates the research in quantum gravity is analogous to the extent to which Microsoft dominates the world of operating systems. On the other hand, our loop quantum gravity colleagues should definitely feel flattered if someone compared them to the Apple or Linux of quantum gravity.

## Friday, July 22, 2005 ... /////

### Hawking and unitarity

The previous blog article about the very same topic was here.

Stephen Hawking who may currently be the world's most famous applied string theorist among the public has finally submitted a paper that many of us were eagerly expecting for a year or two. The paper is titled "Information Loss in Black Holes" and its preprint number is hep-th/0507171. Because it is less than 5 pages long, I recommend you to read it.

On the first page, he summarizes the history of the information loss puzzle. In 1967 the no-hair theorems started to appear: the black holes are classically more or less unique solutions determined by a few parameters. Because they don't have any hair, they can't wear any haircuts that would distinguish them from other black holes with the same value of conserved quantities; they don't have any features that could give them a large entropy.

This is strange because the black holes seem to be the final outcome of a gravitational collapse, and according to the 2nd law of thermodynamics, the final states should maximize the entropy. The apparently vanishing entropy seems to contradict this law. However, the black holes in the classical theory are eternal and we may envision the information as being stored inside the hole; it is just not accessible to the folks outside.

This argument fails in the quantum theory because of the line of reasoning pioneered by Jacob Bekenstein and Stephen Hawking. Black holes eventually evaporate, via the Hawking process, which eventually uncovers all the details of their interiors. The nonzero temperature may be used to derive their entropy via the equations of thermodynamics; the entropy happens to be proportional to the horizon's area (for large black holes; the extensive progress in determining all the corrections from string theory is discussed elsewhere), as first predicted by Bekenstein.

### Cosmic variance

A new blog named Cosmic variance has been started by five well-known cosmologists.

For example, Sean Carroll contributed a piece that argues that the "other" physicists should like string theory. I agree with his basic points. As you can imagine, the owner of this blog is not among the string theorists who are unaware of the large amount of negative emotions that many scientists outside string theory feel against string theory. In 95 percent of cases, they are plain wrong. Believe me that the remaining 5 percent cases are even more annoying.

## Tuesday, July 19, 2005 ... /////

### Measuring the depth of ideas

In this philosophical text, I would like to open the question what it means for a mathematical or physical idea to be deep. Are there some rules that may be used to quantify the depth? At the very beginning, you should know that no exact and objective definition will be found. And I believe that no such a definition may ever be found, even in principle. But let us try to identify some qualitative features of the deep ideas.

In the commercial world or the world of applied physics, one may measure the depth by the amount of U.S. dollars that the idea will earn in five years, for example. (The Reference Frame considers 1 USD to be an international unit analogous to 1 meter, 1 kilogram, 1 second - and the speculations about 1 euro replacing 1 USD as the main unit in the next 20 years to be unrealistic.)

When this approximate concept of depth is combined with the invisible hand of free markets, a mechanism appears that looks for and helps the deep ideas to be created and to propagate. Capitalism works as many readers will agree. The exceptions may be those who call themselves communists in Europe or who call themselves - because of much better skills in the P.R. - progressives in the U.S.

We may leave this approximate notion of depth to the free markets, but I am sure that most of us will feel unsatisfied. We can't really believe the markets in assessing such complex questions as the depth of ideas in theoretical physics undoubtedly is. After all, the markets are driven by the people. This includes ordinary people. Clearly, the rich people - those who have shown their ability to earn money - have bigger statistical weight in the ensemble that controls the markets. While it is natural to believe that this fact may improve the ability of the markets to measure depth, it is obvious that it does not improve it enough. It is simply not the depth that is valued by the markets. We simply feel that an idea does not have to produce much money for it to be deep, and the more pure research we do, the more we feel so.

## Thursday, July 14, 2005 ... /////

### The next revolution

Most of the talks and discussions at Strings 2005 in Toronto already belong to the history. There have obviously been many talks about interesting calculations of medium importance. And there have been important conceptual discussions about the big questions.

Jacques Distler and Peter Woit have written quite a bit about the talks and especially about the panel discussion called "The Next Superstring Revolution". As expected, I can agree neither with Peter Woit nor with Jacques Distler.

Peter Woit's main profession is to find, extract, and artificially produce poison in string theory and for string theory. If you gave him a bottle of Coke with a label "String Theory", he would extract several atoms of arsen from the bottle and claim that you gave him a bottle of poison.

Jacques Distler argues that the students should not ask where string theory is going because they must think what to work on right now and forget about some "exercises" associated with the medium and long term future of the field. This is what the graduate students - who are deciding whether they should dedicate their lives to a scientific field - are being told. Does this answer describe the actual state of communication we have reached? Should the young physicists join the field with the plan to look around every three months what kind of activity is helpful for their careers because this is the only thing that they should really be interested in? I hope not.

I hope that even among the readers of this blog, there are people with great goals and dreams. Some of these goals and dreams will remain unfulfilled. But the dreams and visions are important nevertheless. One of the primary general goals of string theory is to achieve a deeper and more quantitative understanding of the world of high energy physics and quantum gravity than the Standard Model and General Relativity may offer us. And nothing has changed about the fact that we have very good reasons to think that string theory can do it.

## Wednesday, July 13, 2005 ... /////

### Tachyons and the Big Bang

Let's start with a general description of the tachyons, their history, their meaning, and their role in string theory; we will get to the current questions whether the tachyons are important for cosmology later.

There have been many twists and turns in the history of the tachyons. As soon as Albert Einstein discovered his special relativity 100 years ago, it became clear that no particle, no object, and no carrier of information can travel faster than light. The reason is that an observer in a different reference frame would realize that such an object not only travels faster than light but it in fact travels backwards in time. Lorentz transformations make superluminal propagation equivalent to propagation backwards in time. That would destroy causality; it would allow you to kill your father before he met your mother - and such a possibility would transform our Universe into a pile of logical absurdities and oxymorons.

In other words, the four-momentum of acceptable particles must be a time-like vector. Let's choose the convention in which "p squared" is positive in these good cases. Particles with negative values of "p squared" are banned. They are called "tachyons" - the Greek word "tachos" means speed and the name is apt because the tachyons have to be very fast; they would always move with superluminal velocities.

In quantum field theory it is still useful to think of tachyons as particles with space-like four-momenta but it is not the most realistic description of their behavior. Instead, the typical configuration involves a time-like imaginary four-momentum of a tachyon field - a configuration of the field that exponentially grows with time instead of oscillating. The potential energy "m squared times phi squared (over two)" for a scalar field "phi" has a minimum if "m squared" is positive - the regular massive particles - and it has a maximum for negative values of "m squared".

## Tuesday, July 12, 2005 ... /////

### Anonymous remailers

Some people think that if they use anonymous remailers to send hate mail, no one can ever find them. That's not right.

Well, since the infamous March 15, 2005 - which is not only the anniversary of the Nazi occupation of the Czech lands in 1939 but also the date of a certain problematic FAS faculty meeting at Harvard - there have been several episodes that have temporarily but severely reduced optimism and self-confidence of people like me.

Some of these episodes involve pressure by seemingly nice people - our friends and colleagues, in some cases - who have forced some of us to apologize for our opinions many times, to become silent, and perhaps to create five more women's committees. OK, you could have read these (or similar) stories in the media.

Be sure that the president was not the only person who has been subject to this kind of influence. Those who believe that it's only the president who is not allowed to have certain heretical opinions - because they could be interpreted as the official policy - are very naive people. Obviously, the less powerful a person at a university is, the easier it is to impose the "official" opinions upon her or him.

In my case, there have also been roughly two anonymous senders. One of them was directly inspired by the controversy at Harvard. He has sent two slightly entertaining but very embarassing PDF files that contained a mostly fictitious story about me and a professor of humanities at Harvard (plus the officials at Harvard). The goal was to damage my name and my good relations with the other professor. The recipients were all physics professors at Harvard and probably many others; thankfully, they understood that they should not trust the text. I still don't know who was the anonymous sender although he or she is probably living in San Diego. Maybe I should finally find time to investigate this episode...

After March 15th, I have also received very ugly anonymous e-mail messages about Prof. RW and probably Prof. SP - senior professors who had similar opinions to mine about the whole story. The mail about Prof. RW looked like a message from Al-Qaeda because it was heavily anti-Jewish and the author was apparently a radical Arab. Its goal was to transmute a debate about the role of the sexes (indeed, not genders) to something much more serious. I want to assure Prof. RW and others that this message has not damaged the positive image of them in my eyes, not a single bit.

The other sender related to myself - one whom I dedicate the rest of this text - has informed me through ten or so anonymous remailers and through a web form on a website of mine that she or he was going to kill me; the apparent correlation with the controversies at Harvard was most likely accidental in this case.

Those roughly 100 messages - that were sent more or less every week between April and early July - contained a detailed description how the author was going to strangle me and then masturbate because it was so arousing. In other e-mails, he or she just declared himself or herself to be my personal assistant who would help me to kill myself. Some of these e-mails argued that it was necessary to do the same thing with

• all males - the ultimate source of the evil
• all foreigners - especially the Slavs
• all conservatives

The e-mails contained hundreds of copies of the word "die". They have also informed me that the sender had installed a spycam in my apartment and was going to publish the videos. ;-) After some time, I did not read all of these weird messages.

Because these themes were so stable, I eventually became convinced that the author was probably a liberal female scientist born in the USA who was moreover very likely to be pretty fat. ;-) Well, unfortunately the sender was sending e-mail messages through my website rather carelessly; this website happens to be one of a very few web pages of mine that record the IP addresses of the visitors.

So I learned that the sender was from the University of a state whose name starts either with "Q" or "D" and I asked the network administrators over there to help me to stop these messages. They thought it was sufficiently serious and their police started to study this case - very skillful and pleasant guys, by the way. I admire this kind of policemen who are not only strong but who deal with the "real stuff" and who know how the world really works. Some compliments for the computer administrator are attached at the end of this text.

I always emphasized that my goal has never been to create problems for the person because he or she needed help and compassion rather than punishment. It was a great relief to learn that the sender came from a rather remote university and has probably never seen me. You can imagine that my list of possible suspects used to contain several people I knew which was very unpleasant.

Because the visits to my website that were clearly correlated with the hate mail came from particular IP addresses reserved for modems at their university, the authorities knew the identity of the sender by June 20th; they could not get a confirmation from the remailers but it turned out that the sender was the only person at that university who had connected to these re-mailers from that university at all so that the identification could be re-confirmed by analyzing the log files at the university.

The whole story was a sensitive issue, so they were checking and rechecking and trying to think about alternative explanations; a very professional approach. The person was finally interviewed yesterday (7/11). A very bizarre person, I was told, not really a dangerous one.

Needless to say, my instinct has failed completely. The sender was not a fat female born in the USA but a petite male born in Asia - between 20 and 25 years of age. Yes, the author who wants to eliminate the males was male himself. He spends nights gazing at the skies. His landlord is a very authoritative person. I hope that the one way correspondence he has had with me has helped him psychologically.

Please don't ask me for more details; I won't tell you because I want this story to remain partially anonymous. The only exception are people from the CIA and FBI and the Homeland Security Department; I would give these Gentlemen and Gentlewomen contacts to the skillful computer administrators whose analysis was either nearly perfect or perfect - especially one particular administrator - and who could be very helpful for the security of the U.S. or the whole Western world for that matter. The main message of this story is that all of us should avoid writing anonymous hate mail because this is how things can get out of control. And moreover, they are never quite anonymous.

It may be useful to find the sender of the PDF lies, too - it could help one to focus on creative things as opposed to this kind of stuff.

### Strings 2005

The annual conference on string theory in Toronto is underway. I can't write effectively with this modem, so let me give you basic links:

## Friday, July 08, 2005 ... /////

### Bombings

Let me begin with my personal memories of 9/11. I was visiting New Jersey for two weeks and 9/11 was the day in the very middle of that period. More importantly, 9/11/2001 was the day of my PhD defense at Rutgers. It started at 9:30 am, about 43 kilometers from the World Trade Center.

I woke up at around 8:00 am in what used to be my office (equipped with an airbed) - the housing did not work out and it would be too far from the Physics Department anyway. I took a shower and then opened the e-mail. At 9:00 am, an e-mail message from a Czech friend of mine contained a copy of the report of the Czech Press Agency (CTK) about the first airplane abused in New York.

It sounded very bizarre. Nevertheless, it was completely clear to me that it was true. Another e-mail said that the second tower had been hit. I was conveying the message to the people around and no one believed me, except for a few guys who had already heard it on radio. Well, I grabbed an overhead projector and started to defend.

At the beginning, I said that two airplanes were hijacked and used to attack the Twin Towers by the terrorists. Some members of the committee did not believe it. The thesis continued as expected. 30 seconds before it ended, Edward Witten appeared in the room and told me that he liked the defense.

He was giving a seminar at Rutgers the same day. As far as I remember, it was about the G_2 holonomy manifolds. Before the seminar we had a toast to celebrate my PhD. It was one of the most painful toasts in my life. I made a comment that we may remember that day not only as one of the most disastrous days in the U.S. history, but perhaps also as a day of an interesting seminar by Edward Witten at Rutgers. Witten said that he wished I would have had never used his name in that sentence.

From the highest floor of the math department, we were able to see smoke above Manhattan. The elevators were switched off.

It was only after the defense when we saw the first pictures and videos and the full psychological impact started to affect our minds. People, especially my advisor Tom Banks, were making predictions that our way of life had to change. Although some security measures had to be tightened after 9/11, my feeling today is that these scenarios were exaggerated. Many servers such as CNN.COM were overloaded, and because I (incorrectly) thought that all such servers had to be down, I developed a new website (click) that contained pictures and translations of the basic stories from the Czech internet media that worked fine. The website had thousands of visits within a couple of hours.

I am not sure about you but I was silently frustrated and also upset. My anger was not directed exclusively at the small group of terrorists because they were just a tip of the anti-American and anti-capitalist iceberg. For example, a Czech journalist called Pecina published an article in which he endorsed the attacks against the U.S. Later he argued that it was a way to prove his journalistic independence.

I wrote him an e-mail that argued that the main differences between him and Al Qaeda is that most members of Al Qaeda were born in problematic conditions; and most of them are, unlike Pecina, able to sacrifice their lives for their sick ideas; on the other hand, Pecina has similar goals and emotions and is expressing them in a society where he knows that he can't be punished. This "hate mail" was published and it still appears among the best Google's hits if you search for my name. Needless to say, I would write a similar mail again if the context were similar.

The casualties were often estimated to top 10,000 people. I made a bet that the total number would exceed 10,000. Fortunately, I lost this bet. A week after the attacks, I tried to see Wall Street but the air was still so unpleasant that I did not make it to the Ground Zero.

About three years later, Madrid was also attacked by the terrorists and Al Qaeda helped to elect the Spanish socialists whose relations with Al Qaeda were widely viewed as the more friendly ones. The number of casualties was smaller by an order of magnitude.

The casualties in yesterday's attacks against the city of London seem to be one order of magnitude lower still. While it is still an alarming number of lost lives, the counting suggests that the capabilities of Al Qaeda to end lives are going down the hill. Let's hope that these attacks reflect the typical maximum scale what they can do today. You know, the impact is not so different from a lunetic with an automatic gun who simply starts to shoot as many people as possible in the subway.

London was just chosen to host the 2012 olympics (54 vs 50 for Paris). It's very likely that some votes would have been missing if the vote took place after the attacks and Paris would win instead. Great Britain also succeeded Luxembourg to become the semi-annual leader of the European Union. The Reference Frame officially supports Tony Blair's major policies (with the exception of the climate change agenda). Undoubtedly, Margaret Thatcher is one of the great living examples for the "labourist" Tony Blair and he is doing great steps not exactly to match her greatness but at least to become a comparable leader.

Unfortunately, it is this kind of a leader and his country who is likely to become a target of the acts of human trash such as Osama bin Laden and his disciples.

Some friends of mine are very frustrated by the London attacks. They say that the world is so bad that it is not worth living here. I don't know how to cure these feelings; the best thing I can do with them is to disagree. The world as of 2005 is a pretty good one. Look into the history textbooks and you will see that our world is better than it was at most moments in the past. 65 years ago, it was common sense in most of Europe that people should be killed if they were Jews. 500 years ago, you could have been executed for stating that the Earth orbits around the Sun or for trying to figure out how the guts or the brains work; today it is much better because you will only get a "lack of confidence" vote for the same thing.

The successors of the Inquisition may be obnoxious, but they are not directly threatening your life. (My apologies go to the sexual deviant and killer from the University of Delaware who counts as an exception.) Al Qaeda is a successor of the mass famines, tuberculosis, and other diseases. Except that it is killing many fewer people than the diseases did. And much like in the case of the diseases, we are getting better in fighting with these threats.

A few million years ago, you would be eaten by another mammal if you did one error. 14.3 billion years ago (without 300,000 years), the global warming was so bad that you could not even form the Hydrogen atom. 3 minutes after the Big Bang, all the nuclei would be transmuting into each other all the time. One Planck time after the Big Bang, even the very concept of space and time would be so crippled that even the best string theorists from 2005 could not tell you what to do - even what (and how) you should calculate.

Let me summarize. We should not expect that some threats and annoying things will disappear completely. Moreover, I think that the desire to eliminate an annoying thing completely underlies most totalitarian ideologies. There will always be some risks and some threats. In the case of the terrorists, virtually all of us realize that they are a real problem and we are trying to deal with it. But don't forget that the risks will never disappear totally because it would violate the uncertainty principle. Just like an evil dog can bite you on the street and kill you, you may also be killed by a lunetic (terrorist) in the subway. The probability is small in both cases. And many people are employed to keep the vacuum expectation value of the rate of such deaths low enough.

The terrorists and their ideas and ideals simply cannot be dominating over the world of the 3rd millenium.

## Monday, July 04, 2005 ... /////

### NASA's collider

NASA has constructed a collider with the center-of-mass energy well above 1030 GeV. The collision took place during the Independence Day. Unfortunately, the huge energy was not focused into a single pair of elementary particles. Therefore, NASA only saw a dirty cloudy images instead of new physics. ;-)