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Koji Hashimoto | Osaka univ. | Japan

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Trial and error.

Sunday, January 24th, 2010

I have been concerned with a single problem on my research project, for about a month. Since the end of the last year, this problem stucks in my head for long long time. I have tried various ideas and calculations, but all of them failed so far. Last week, I changed the approach again, but the success is still far away. If you are a theoretical physicist, you know that I am now very much enjoying the moment of struggling. This is the most interesting and joyful part of research. I experience battle of various notions and ideas of D-brane physics, sometimes they conflic each other, sometimes they coorporate with each other to form a new interesting notion of physics. This is the moment for which I live.

I cannot tell the problem in detail here, since it is an on-going research subject. It is on a new description of nuclei, coming from D-branes and superstring theory. If this is successful, this would give a totally new description of nuclei, but… who knows if it will work out or not.

Tomorrow, again, I will experience the excitement, and the life of a scientist is like this every day.



Monday, January 18th, 2010

Currently I translate my own book written in Japanese, to English. This book is on D-branes in string theory, and the Japanese version was published in 2006. The book is for undergraduates, so includes not many equations. I tried to convey a flavor of fronteer researches on string theory and D-branes. Fortunately I got an offer from a publishing company for an English version of the book, so I am translating the book with my wife. I hope we can finish this translation in a month or so, so that the English version is published before the main results of LHC will come out.

As you can easily guess, it is very hard to work on translation. For me, it was much easier to write the book itself. Translation is a kind of tedious work, I need to choose terms which do not spoil the original sentences… So I decided to work on it only in trains. Everyday I commute by trains for almost one hour or so, and I can have a seat in the trains, although I live in the middle of Tokyo city. As you may know, Tokyo is a notorious place for the population, and every train is quite packed with people. However, fortunately, in my trains I can find only few people, as the direction of my commuting is opposite to the direction of most of Tokyo people. So I open my laptop every day in the train and start working on my translation, for at least 30 minutes. I hope you may be interested in the English version of my book in which the notion of D-branes and string theory is given, at the education level of graduate students.


Collaboration discussions.

Saturday, January 9th, 2010

I am enjoying collaboration discussions with my collaborator who came from Europe, this week. He will stay at our group until next week, so we need to at least summarize what we are working on currently. I am fascinated by a certain possibility of the project, and we are now seeing whether this goal can be reach soon or not, by examining various computations coming out of our action. This stage is, for me, the most important and exciting part. Well, I have done 50 pages of calculations so far, and this amount is almost enough for me to have a firm basis for playing around this model. And now, if we can make it to find a breakthrough with this model with the current knowledge and our power, then this work is going to be a good work which may be influential. But if we fail, or if the possibility that the model itself does not have a power to predict what we like to know, then it is the end, it ends up woth one of many many models. So, the current stage of the collaboration/research is quite important, and interesting.

I have been concerned with a particular question, whether the quantity of my concern can be derived from the action which I computed, for about a month. A month is not a long period but it is probably enough to make a judgement of whether I should put more effort on this problem or not. Fortunately my collaborator came to visit me until the end of next week, so I will eventually the judgement next week. This is very good.

Working alone is sometimes good, but in most cases, I think the most essential fun in physics research lies in discussions. I love collaborations. Fun through collaborations is what I like to experience with full effort of my life.

I will report what is my judgement, probably at the end of next week, here. But nobody can predict how any research project will go……  

I wish all of you who read this Quantum Diaries blogs a happy and new year 2010.


At Taipei, and Kyoto.

Sunday, December 27th, 2009

national taiwan normal universityLast week I have visited National Taiwan Normal University to give a talk at Taiwan string theory workshop 2010. This is in fact I guess 6th or 7th time visit to Taiwan, as I ama very frequent visitor to the Taiwan string theory group. Poeple there are always hertful, and this time again I enjoyed the visit very much, although the visit was only for three days.

Tanwan string theory group consists of members from many universities. Though some of the universities are very far away from the central Taipei (for example there are members in Shinchu city which is almot one-hour away from Taipei by a bus), people gather at National Taiwan University for enjoying seminars almost once every week. Discussions in every seminar is quite lively, and I am sure every visitor is surprised to see this kind of seminar series working in Taiwan. Most of post-doctoral fellows in Taiwan string theory group are Japanese, and so there is an intimate relationship to Japanese string theory community. Many Japanese researchers visit Taiwan, and I am one of them.

I visited Taiwan for the first time quite a long ago, probably about ten years ago. At that time the string group was not so big, but the basis of the present heartful group was already there, I enjoyed talking with active people there, all of them are my friends now. Since then, the group gradually expands and grows, with a national fund supported by the government, forming a string focus group. From the Japan side, thanks to prof. Inami’s effort for getting a special fund for visiting Taiwan, there are a lot of researchers, in particular young researchers, have visited Taiwan. Now, I think we can say that there is a strong connection between Taiwanese and Japanese string theory communities.

The workshop this time was joyful again, and I enjoyed talking with participants and other speakers, and also enjoyed drinking beers with my friends at a bar near the National Taiwan university canpus. I am happy to see my friends, in particular Japanese friends in Taiwan are enjoying their lives there.   

Kamo river near the Kyoto university campus.After coming back to Japan, I soon came to Kyoto for speaking about my favorite supergravity solutions and trials to solve some equations of motion for a holographic realization of color-flavor locking phase, at a Yukawa institute workshop on blackholes in higher dimensions. It was really a fun to communicate with people doing research on gravity and relativity, in particular at a drinking place. When I talk to them, I soon became aware of different motivations for computing the same background geometries. Well, that is obvious. and, even worse (or better), we have a confusing terminology. When I (and people doing string theory) say “backreaction”, the meaning is different from the “backreaction” which the gravity people use! — Quite confusing. But at least for me to know this difference is a benefit, for my presentations in the future. My talk was on 25th December, there is no Christmas or something in the field of gravity and relativity, it seems.

I wish you all a happy new year.



Wednesday, December 16th, 2009

It’s cloudy and snowy here at Vancouver, I am visiting TRIUMF for just one day.

We are enjoying RIKEN-TRIUMF collaboration meeting for nuclear theory. Again, I am attending for presenting a talk of course on nuclear physics. People in the theory group of TRIUMF are friendly and I have a good time here for discussions and chatting. I am not sure how much our work on the computation of the nuclear force in string theory may help real nuclear physics — “real” means precision nuclear physics, well, nuclear physics is really a precision physics, while our computations using holography have always 1/N_c corrections and never be precise in that sense. However, I emphasized that to get a global picture of what is going on before getting into the details, our approach may help. And one of those themes is in fact many-body nuclear forces, which are still mysterious for any nuclear physicists, I believe. Thanks to the question I got from the members of TRIUMF and also from RIKEN members, I vaguely get one more direction of my research, though I am not sure how it is going to be realistic.

TRIUMF has a nice accomodation which is called TRIUMF House. It is located in the middle of the UBC (university of British Columbia) campus. The rooms are confortable, and it has a nice large common kitchen, so it is a relaxing place. We rent a car, and for the first time in my life I drove in snow… Probably because the car was a nice one, there was no actual difference in driving in snow and in rainy Japan. Driving in North America is a fun, I like it very much. It actually makes me fell like I am really in a foureign country, somehow. It would be beautiful to drive in Canada in summer seasons, and definitely I would like to come here again in the future. So, I will not exchange my Canadian dollars back to Japanese yens, and keep the Canadian dollars for my future trip to Canada.


On a Shinkansen to Nagoya.

Thursday, December 10th, 2009

At 6 AM in the morning, I am in a Shinkansen bullet train to go to Nagoya university conference “SCGT (Strong coupling gauge theory)09“. On my left I can see a beautiful oscean scenary in the dawn. The train is moving at the speed 270 km/h, and I have never imagined that I would be such a frequent (and fast) traveler, 15 years ago when I was an undergraduate student. At that time, I had my own imaginary view of what is a physicist, probably by extrapolating just views of some professors whom I could see at lecture rooms in Kyoto university. But it was of course very tiny part of professors’ daily life, I could never know it. I thought that any physics professors spend their time mostly for just sitting in front of a desk and “think”: this is what is written in books, as long as I remember. Every physicists in books looked just wondering around his/her desk or having discussions with their colleagues, at universities and sometimes in mountains, like Heisenberg, and then, just sitting at a desk and thinking something about physics , going down to the deep thoughts. This was what I thought. But the reality is so different from that.

However, I am enjoying this life. It is wonderful that I could see many friends and enjoy discussions, at many places in the world. For example today, I will see friends from all over the world (again!), and will definitely have joyful discussions. Waking up at 5 AM is nothing. (But last night, I drank until 10 PM at a farewel party for my friend, at RIKEN…..)


Visiting DAMTP, Cambridge.

Monday, November 30th, 2009

画像-0020It’s been long since I have visited Cambridge before, probably it was already 4 years ago. I lived in Cambridge for half a year, as a visiting researcher then at DAMTP (Department of Applied Math and Theoretical Physics), universtiy of Cambridge. I have good memories on my days at Cambridge.

Last time when I was here at Cambridge, I couldn’t imagine that I would be working on nuclear physics. The talk I gave here 4 years ago was on ADHM construction of instantons and its D-brane realization, and the motivation was purely mathematical physics. But this time, again in my talk I told about ADHM construction, but now applied to nucleon nucleon interaction realized and computed in string theory. It is interesting that, although the mathematical tools are quite similar to each other (and almost the same), the motivations were totally different.

Discussions with my friends at DAMTP were joyful, and are always insightful. And, one more thing — winter in Cambridge, it is beautiful.


Yukawa Workshop on “Branes, Strings and Black Holes.”

Sunday, October 18th, 2009

hokubu200505_2[1]Kyoto is of course one of the most beautiful cities in the world, and this season, autumn, is the best season for Kyoto, as leaves on trees changes their color, with quite confortable temperature/humidity which is suitable for sightseeing. Therefore— I could not find a hotel in Kyoto, although I need to attend at the workshop for a week. I should have booked a hotel long before, but I completely forgot the fact that Kyoto is special like this. So, I was forced to commute everyday from Osaka, taking 1 hour by train and 30minutes by walk, to attend at the workshop. This is the reason why I got so tired after the workshop. In the walk every morning to the Yukawa institute, trees and temples were beautiful, but that actually did not help me refreshed enough, unfortunately.

However, the workshop itself was fruitful for me. I met many friends who work outside Japan, and discussions with my friends were very intriguing and stimulus. In the week, Yukawa institute looks like Santa Barbara KITP: relaxing mood for discussions without caring any time schedules, and lots of specialists of string theory who all have depth and width. I felt that this is a way to a success of Yukawa Institute, as I have heard from several participants from abroad that the visit to Yukawa institute for this workshop was fruitful/joyful. This owes much to the organizers and also to the secretaries at Yukawa institutes, as I have heard that a secretary arranged even a nursery school for participants who have a small child, that is great and even unbelievable for me as in Japan there is a serious national issue of complete lack of nursery schools compared to the number of infants/kids.

Kyoto is one of my home towns as I spent 10 years of my life there. Nothing has changed since then, except for the fact that an old building in physics department, in which I enjoyed prof. Kugo’s lecture on particle theory 15 years ago, has gone for rebuilding.


Superconductors and M-theory.

Saturday, October 10th, 2009

Today I enjoyed a seminar on chiral p-wave superconductors. It sounds completely different from what superstring theory may be relevant with, but indeed it is not the case, that was really a fun. Well, probably people who are already familiar with superconductors know well about it, but it is again surprising to me that this superconductor  exhibits a Chern-Simons gauge theory in 2 + 1 dimensions, and this theory is indeed familiar to superstring theorists: that is an effective theory for multiple M2-branes, proposed very recently. So, there is indeed a connection, at least at the level of effective theory and formality, between ultimate theory of the universe, M-theory, and the effective theory of a particular kind of superconductors. The similarity is not just the effective action, but indeed goes over to the physics of the theory. Of course today’s seminar, brought by a brilliant condensed matter theorist, did not give any relevance to M-theory, but the possibility is obvious to superstring theorists. Relevance to the massive photons really reminds me of the connection of M2-branes to D3-branes which I eventually worked on last year with my collaborators. This is quite fascinating.

The relevance goes over to a recent proposal of a holographic gravity description of superconductors. A gravity dual of p-wave superconductors was proposed by Gubser, and M-theory embedding of those kinds of holographic superconductors were worked out recently. This fascinating field has a lot of potential applicability of string theory techniques. 

Today, I felt strongly that I need more interaction with condensed matter physicists, and a dawn of a new era of  string theory “technology”.



Tuesday, October 6th, 2009

I guess it is rare situation that a superstring theorist visits J-PARC. This new organization for experimental research in elementary particle physics, hadron physics, nuclear physics, and more and more, is completely beyond my imagination. I was invited to an international conference on strangeness and hyper nuclei “Hyp-X” which was held near J-PARC, and the organizers have a very good idea of having an excursion program for visiting experimental sites of J-PARC. Off course I attended at it, as it is obvious that this is a rare opportunity — once the machine starts to operate, anyone cannot see inside the machine, and some parts of J-PARC is still under construction, fortunately for me.

At a glance of the hugeness of the beam line, I was, literally, moved, and stunned.

I vividly remember my feeling when I saw the neutrino beam line at KEK, and the beam line at LHC ATLAS. I was so moved. And the feeling at J-PARC was exactly the same. In my everyday life, as I am a theoretical physicist, I don’t really imagine what kind of experimental monster machine is necessary to probe really the results of my theoretical calculations. Well, that is the theoretical physics. But, every time I see those monsters at collider sites, I feel that it is very important, in particular for theoretical physicists, to actually see, watch, the monstrous machines. These machines are truly one of the “best” machines which human kind has ever built — you never know it, you just feel it when you stand in front of the machines.

I have been working on superstring theory for more than 10 years. And to tell you frankly, it was rather recent that I start thinking about “real” physics. In my graduate days, my sense on energy scales was quite bad. 5 years after I got PhD, for the first time in my life, I wrote a paper which include the real energy scale “MeV”, although I have published many papers before then at “hep-th” archive, “hep” meaning high “energy” physics…. I am very proud of the paper in fact, as I felt that, at last, I could tell my friends that I am a “high energy” physicist. Well, of course, progress in superstring theory needs many many things which are unrelated to real physics, and one can say that most of the progress were born in such situations. However, it is indeed important that superstring theory now comes back to real physics describing QCD, hadron physics, and even nuclear physics.

I hope more superstring theorists may visit J-PARC.