THE "Mihalas"

Yes!! Now I have an original copy of the "Stellar Atmospheres" book, by Dimitri Mihalas. The book is like The Bible for everyone who works with Radiative Transfer in Astrophysics. Since I first got my hand in this book, 2 or 3 years ago, this is the number ONE book in my wish list, but, unfortunately for me, the book is out of print since a time immemorial, and no one who I knew have this book would sell it. I could find used versions of the book, but always for more than $200.

Last month, I was browsing through Amazon looking for books to buy, and then I decided to look for it again. Then I saw it, a copy of the book being sold there by less than a hundred dollars. The description was saying the book was in good conditions. Then I thought with myself, or I buy it now, or I will never find such a bargain again in my life. I thought for 2 seconds, before adding it to my shopping cart. And then the waiting started...

Today THE book was delivered at my place, here in Brasil, after a little more than 2 weeks. I was just expecting it by the end of August or maybe even mid-september, but it took only 2 weeks! I was also expecting a somewhat used book, maybe a worn used book, but when I look at it, I was stunned... The book was in an almost perfect condition, and seemed to have barely been used at all. Just some small scratches at the edges of the hardcover, and it is a 30-YEARS OLD book. I am gleeful with my new aquisition!!

NOW I HAVE THE LEGENDARY "MIHALAS"! And I can even dream with my PhD, without remorse of not having "THE Mihalas". I swear that I will put the book to good use, and I will not use its power to strengthen the Evil in this world. It will only be used to bring more Entropy to this dimension! =D

Snow desert and interpolation problems

The winter is as harsh as it can be here in Ann Arbor. The city seems like a snow desert, in a sense that instead of sand being blown by the winds, you can see small particles of snow almost creating moving dunes of snow. Temperature has never ben so low. Sunday the temperature reached the -30oC, and we had winds of 60km/h and sometimes even surpassing the 100km/h. Of course, I just stayed quiet at home. At this moment, it is windy and snowing outside, and I am sure all the transportation system in the city is disrupted. I am still at the University, just gathering my courage to go outside and endure this "warm" weather (-20oC) while I wait the bus. And the adventure continues!! I love this place, and this cold!! :P

I guess I finally understood why the program I was modifying to calculate the line profiles I seek so vehemently is not working. One week ago I finished my modifications, and I was sure that after those modifications the code had to work perfectly, but it did not. So I spent the rest of the week trying to figure out why in the name of the Infinity Layers of the Abyss that god forsaken code was not working!! Just looking at my results I could figure out the problem was in the optical depths of each of the rays (the optical depth is a measure of how deep you can see a ray of light before the medium becomes opaque). The optical depth was becoming too large inside a region where it was not expected to be so large. Large optical depths mean one thing, and it means that the atomic level population densities where not being properly calculated.

I started to track the values of the population densities where the optical depth was becoming too large, and then I found something unusual. To calculate the optical depth between two points I have to calculate an integral between these points, and to calculate this integral I need the population densities in these two points. If I have two points very near, I don't expect the population densities to be very different, and what is happening is that near the edge of my wind the difference between these values for these two nearby points is very large (something like 10000 times from one point to another). And that was the reason why the optical depths are becoming too large in a very low density regions where they should be very, very, very small (instead of being something like 0.001, the values are something like 100, and it means that the ray is not able to cross a region where otherwise should be almost transparent).

Diving deeper in this problem I realize that the problem was in the interpolation function that was called by the program. The problem was that I have not changed that, so if the program was working before, it should be working now, but I decided to verify anyway. And after some debbuging, I could not find anything wrong with that. All the physical quantities being calculated by that function were correctly calculated. The grid file I have calculated to used as an input to this program was also perfect. Then I remember the flux program needs a input that is a little different from the one I give him, and to get this grid file I have to use another interpolation subroutine in IDL. I looked at this other grid file, and there was the cursed error!! The problem with the population densities appear just after I use the IDL program to re-grid the original grid file. There is a strange function it uses to interpolate called "Triangulate" that is causing this problem. I have no idea how this function works, but the problem surely is due to the fact that the problematic region is exactly in the border of the wind, and borders are usually problematic regions.

Now I just need to figure out how to solve this interpolation problem... And I don't think it will be easy... And my time keeps running out... 27 days left...

...of Eyelids, Classes, Blogs and House Invaders...

It is been a little while since I wrote here. I have been working a lot in these last two weeks, and when I got home my mind is so tired that I can barely think about something to write. And I realize today that I am really stressed. My eyelids are twitching non-stop since Tuesday, and the reason is probably related to stress. All my work is done in front of a computer, and sometimes I just focus my eyes at the screen, and I look at that intensely for hours and hours without realizing it. I also have been sleeping very little in these past days. My eyes must be really stressed.

At last, it is weekend and I guess I will rest my eyes a little bit for the next two days, or at least I will try it. Problem is: I have to work during the weekend too... Damn!!

My adviser is teaching "Stellar Astrophysics" in this term. I asked her if I could watch it, and she told me that I was welcome to go to the classes. It is weird, but after two years without having to worry about watching classes, and studying for exams, I was missing it. That was one of the main reasons that made me take this decision, the other reason is that I love this subject and I wanted to remember those things again. The only problem was that the classes were at 9:30AM, and to wake up around 7AM in this winter is an herculean effort. It is very cold, and it is still dark outside, so it is almost impossible to get out of bed. After watching her first class, last week, I was totally amazed. Her class is just PERFECT. After 10 years of Physics and Astrophysics, I am still to see someone teaching better than her. She is able to express everything with such clarity that it is almost impossible to have any lingering questions about it later. (Maybe I am exaggerating a little about it, but I am not writing it just because she is my adviser... So far her classes have been excellent.) The duration of the class is 1h30min, but after that time I am still very interested and eager to watch more and more... I don't even care anymore to wake up at 7AM two days a week to go to that class. Unfortunately for me, I won't be able to watch her class until the end, as I will return to Brazil just in the middle of the winter term here. She gave us some homework to do for next week, but she told me that I don't need to make the homeworks, after all I am not officially enrolled to her class and she also told me that I already have lots of work to do, but I am still thinking about solving some of the problems in the homework just for keep the mind sharp about the subject, and to try to remember things that should be somewhere lost in my head. (It is too nerdy to think like that...)

I had a lot of good teachers in Brazil, and very good ones by the way, but I can remember only one or two teachers that were able to be as clear as she is, but I still think she is the best. Maybe the reason for that is that I really love "Stellar Astrophysics", and now I am just in the class to remember things, and not really to learn any new thing. Maybe that counts to the fact that everything seems so clear to me... But none of the other students have any complain so far, actually they are really loving her class too.

I have already written here about my work blog, called "Stellar Xaos". I was really excited with that when I created it, but I have barely written anything there. There are two problems with that. The first is that I don't want to simply write about the things that I have done in one day, if I had made any progress in that day or not. I want to write when I really have something good to write, when I make some kind of breakthrough in my work, and things like that, and eventually write about the theory behind the work I am doing right now. So far, I am not having the time to write about any theory, and nothing excited happened. The work is progressing, but nothing worth to mention, yet... That is one of the reason I have not written anything new there for almost two weeks. The other thing is that the blog is hosted by Wordpress, and to be sincere, I don't like the limitations of that site. If I want to edit my template, for example, I have to pay a small fee, and that is not cool. They have a lot of interesting templates, but I would love to customize it. There are also other limitations regarding what features you can add to your blog.
So, it is very probable that I will change hosts, and as soon as I have something more excited to report, I will create another blog hosted by blogger.

In this very moment there are a lot of unknown people in my house, friends of my roommates. But I am very tired and lacking the patience for social rituals in this moment, so I am going to remain enclosed in my room. I just want peace and rest for my eyes right now...

Preeliminary H-alpha line profiles

If you ever wondered about what in the Nine Hells of Baator does a theoretical astrophysicist do, wonder no more. Here is a glimpse of my preeliminary results. Two calculated H-alpha line profiles for a T Tauri star, the filled line shows the profile with only magnetospheric contribution (the original code, before my modifications ), and the trace-dotted line shows the profile with magneto-accretion plus diskwind contributions (after I modified the code). Beautiful, isn't it? A little more thinking is necessary to be sure that my code calculations are right, but at this moment I am almost sure they are.Now you are wondering about what is a T Tauri star, or what is magnetospheric accretion (a.k.a. magneto-accretion), and what is diskwind, right? And surely, you also wonder about why the difference in both plots are so important. Ok. I will explain those issues at another day. But at least, now you know about the kind of results that I am seeking, and that hopefully will grant me a PhD. degree in the near future.

Primary Mission Objectives Complete (?)

The code is ready, and running!!! Yeah!!! I have calculated the first H-alpha line profiles with the my new code, and as far as I could notice, the results are fairly good. Tomorrow I will start to compare results from my new code with the results from the old code, to see if there is any kind of inconsistency.

At least, I am not expecting many inconsistencies anymore. I have a feeling, looking at the values I had obtained that they were fairly good. I just hope that my intuition is correct about that...

I had it all working before the end of the week, before my self-instated deadline... \m/,

Something hidden in the deepest recesses of my mind worries me though... something very subtle... hmmm...

Code almost ready, and running...

...and so, at long last, I have solved the problem that was haunting me during this past month. My code is almost ready, and as far as I know, it is working properly. The main coding is ready, and with some other small changes in the last routine, everything will be working soon... I expect to have it ready by the end of this week.

During this past month I have barely touched the code. My adviser decided to give me some other task, and I was working with that for the past few weeks. Last week I have finished the task, and I have showed her my first results yesterday. She was quite excited about them, but they are only preliminary results. I still have to refine them. The task was to use the original program I am working with (prior to applying the changes I have done) to calculate the Lyman alpha line profile for TW Hya, a well known T Tauri star. The Lyman alpha line transition is a transition from the first energetic level to the second energetic level of the hydrogen atom. The photon generated in such a transition is in the ultraviolet part of the spectrum, and most of the contribution to the formation of this line comes from the magneto-accretion funnel, and the accretion shock region in the stellar photosphere. Enough to talk about that... I don't think anyone but me (and the people who work with me) is really interested in knowing more about that anyway... (But if anybody has any question about it, I can try to answer... :P)

So, Monday I gathered all my courage and started to figure out the problem in the code again. My mind was much more calm than when I last tried to work with that, some weeks ago. I decided in my mind that my deadline to finish this was this week, and so I opened the code, took a deep breath, and started to debug it, again... Running the program many times, looking the output files, searching and seeking the errors from one point to the other point of the code, until finding the very routine that was the source of the error or errors as I came to discover moments later.

Looking in a more detailed way at the output files, I have found something that I was not expecting. An error in the density values that I have not seen before. The code was having problems in "remembering" where some points really were. If the point is in the magneto-accretion funnel region, the density is calculated using one law, but if it is in the diskwind region, the density was calculated using another law. The problem was that the ONE code line, that was "remembering" the code where each of the points were, was misplaced and then the code was a little confused about the whereabouts of each point, and as such the densities were not correct everywhere. The error was corrected, the program ran, the densities were all corrected this time, BUT the end results were still wrong...

More work... more debugging... insanity taking over my mind again... The Cube... insomnia...

Then today, after a good night of sleep, and after arriving very late at my office, I started the work again. Seeking the errors through the code, from one variable to the previous erroneous one. After tracing back the error through a lot of variables, I have finally discovered that the source of my nightmares was in an interpolation routine. I have changed that routine a couple of months ago, but I have failed to notice a missing point there, and the thing that I have forgotten to change was the source of all my problems. With the previous line of code the program was looking for something like the "j+1" component of a vector-variable that had only a "j" number of components. And so the "j+1" component that was being read somewhere by the program was a random value coming from some unknown and sinister part of the memory (it is usually the next value in the memory block after where the vector-variable was stored). And that random value was affecting all my calculations, spreading the error throughout the other values like an infectious disease. Something that should be positive, had random negative values. Values that should be as low as zero, were acquiring values than a googol (not kidding here, some values were around the order of 1.e+290). And some other strange behavorial problems...

I changed that line and now everything is working properly. The output values for the source function and the average line intensities at each point in the system are being calculated correctly. Next step is to change the program that calculates the line profiles. No more hautings...

At least some good news concerning my work...

The Malevolent Code of Cubic Insanity...

This program code I am working with is driving me insane. More insane than I already am. Every time I think it is ready to work, I have a new surprise. Yesterday I solved a problem with some velocity gradients that were not being calculated correctly, because the point in which the gradient was being calculated was too near or exactly at the boundaries of the program domains, and so when the program tried to calculate the gradient one of the points used to do that was outside the domain and the gradient went to zero. And as the program uses the gradient to divide another variable, the division result was going to infinty, and everything was out of control. I solved it, it is working, and then I realized today that there was another set of velocity gradients that were zero and that should not be. The velocity gradients at the crossing points. What are the crossing points? It does not matter... I will only say that they are one of the most important things that were calculated, and without the correct gradients at these points, I can not calculate the line profiles that I want to in a proper way.

My mind is totally out of phase at this moment. Something like a magnetic reconnection is almost happening inside my brain, and maybe a great psionic burst will be produced in the next few hours. I guess after that I can focus my mind again. (Have I already told you that I am getting more insane than I already am?)

My advisor came to my office to talk with me today, and after a while she told me to take a walk and clear my mind. Wow... That never happened before, I guess I should be really stressed if she told me that! Hehehehehe... Just fun...

After that I went to the Michigan Union Building to eat some stuff there, and after eating I went to see The Cube, and wonder about its intricacies. Yeah... I will make a special post about The Cube, but first I need to take a picture of The Cube. But I can tell that I can fell a time-space disturbance around It, and a strong one, and there is something Evil about it... A Malign Time-Space Disturbance can only mean one thing...

Vida inorgânica e MHD

Acabei de ler uma notícia deveras interessante. Parece que descobriram alguns indícios de que é possível haver vida inorgânica. Muito bizarro, mas quem disse que a vida tem que ser orgânica, ou seja, tem que ser baseada em átomos de carbono!? Quero só ver onde isso vai levar, afinal foi só uma simulação por computador, onde normalmente são utilizadas vários tipos de aproximações, mas apesar disto, os resultados obtidos por elas costumam refletir bem a realidade. Senão, elas não serviriam para nada, e eu eu não estaria aqui tentando fazer meu modelo funcionar! :P

Vale a pena dar uma olhada. A vida, afinal, é puramente MHD (Magneto-hidrodinâmica). :P

One less problem to solve...

Take heed and bear witness to the truths that lie herein, for they are part of my legacy to the world (Not even a little bit pretentious, huh? It was just a small reference from some PC Game of 11 years ago, that I am sure made a lot of people addicted to it, and I even have written something about it a time ago, using the same sentence). And so it came to pass that the problem that was haunting my dreams during these last days was at last solved. The optical depths is, again, at acceptable levels as also is the density of the excited state that was the cause of the problem. The error was not in the code after all, it was in the input file that was read by the code before, and that was used as a configuration file. The gas temperature in this file was a little too high, and it was the cause to the great value for the density of the second excited state in the hydrogen atom, and the causing the great optical depth for the transition from the 2 excited state to the first excited state!

Time to go on, and now patch some other errors... One less..

Optical depths and the atomic excitation levels densities...

After a while I have discovered what was causing that cyclopean optical depth values in my calculations. The problem was the density of the excited atomic state, it was far higher than it should be, and it is still that high. After discovering the source of the problem I have formulated various possibilities for what was the cause of this erroneous value. The possibilities were: an integration error during the calculations of the solid angle covering the star, or the accretion disk or the disk of my system, but after taking a look at these values, I have concluded that those values were fairly good; another possibility were something wrong during the velocity gradient calculations, but again these values had the correct order of magnitude that I should expect. I have not changed anything in the routine used to calculate the densities of each of the atomic excitation levels needed, so it should be correct, after all the program still works as it should work for what was his prior objectives.

After finishing checking those possibilities, I began to wonder where was this error. All the input the input values are what they should be, but the output value is nowhere near what is acceptable. Then I thought about the many iterations needed for this calculation, and I remember that all these values, for every iteration are saved in a general output data, not only the last iteration values. After that I decided to take a look about how these values evolve through each iteration, and I saw it... The problem is in the first value for density that was calculated, even before any kind of solid angle integration or even after using the routine that calculates the excitation equilibrium states for the system. I was looking for the problem in the wrong place, now I have to start looking in the right place.

And so, here I go again... I expect that this time I can find the problem.

Calculated optical depth...

And so after solving a lot of problems in my program code, I was already happy because it is almost working properly. I just have found out that it was calculating, I think, correctly the source function of each point, it was just having a small output problem (a problem with the correct value not being saved in the output file). And then, I spotted it... An impossible value... Something that made me laugh, almost insanely, due to absurdity of what I was seeing on the screen... The calculated optical depth, something that should have the value of the order of a unit, was with values of an order of magnitude of 10^5 and reaching even 10^9. I don't think any photon could cross that region not even in a googol years... :P (I am just exagerating about the googol, of course. And for people who does not know what in the Nine Hells, also called Baator, is a googol, it is 10^100, or 1 followed by onde hundred zeros)

The only thing I can do for the time being is to laugh... Then I will try to find out where in the program lies this problem!

For people who does not know what does optical depth means, it is related to the escape probability of photon to leave some region of space. The higher the value, the smaller is the chance of it to escape before being scattered or absorved by the medium, meaning that more opaque is the medium. That is the kind of thing that an astrophysicist tries to calculate, and/or uses in their job. Total madness if you want to know my opinion about that, but it is also pure beauty! =D

Another problem, but the good thing is that I could saw it before going further. Now I have to spend some time on it, and I guess it will be quite an amount of some time... Bah! And I am still laughing... HAUhAUhUAHauhuHAuHAUhUAHuHAuhaa....

Novas 7 Maravilhas do Mundo & Gordon Conference

Eis então que o Cristo Redentor foi eleito uma das novas 7 Maravilhas do Mundo. Definitivamente não concordo! Pode até ser o símbolo do Brasil, e como Brasileiro eu deveria estar achando ótimo, mas acho que entre os monumentos votáveis, o Cristo Redentor seria das minhas últimas opções. Talvez eu votasse no Cristo Redentor, caso esta escolha fosse feita daqui há alguns séculos, 500 ou 600 anos pelo menos, e este ainda estivesse de pé. Existem outros monumentos que representam realizações muito mais notáveis que o Cristo Redentor, e que depois de mais de mil anos ainda estão de pé. E historicamente, ou culturalmente falando, a maioria deles são mais importantes que o Cristo Redentor. Talvez se estivessem limitado a época da construção nos últimos 100 ou 200 anos, eu votaria nele com quase certeza, mas não dá pra comparar o Cristo Redentor, com as Pirâmides do Egito, a única das maravilhas do mundo ainda de pé, Angkor-Wat, Stonehenge, Acropolis, e nem mesmo com nenhuma das maravilhas eleitas.

Pra quem não sabe, as novas maravilhas do mundo são: A Grande Muralha da China, Petra (Jordânia), Machu Picchu (Peru), Chichén Itzá (México), O Coliseu (Itália), Taj Mahal (Índia) e o Cristo Redentor.

Voltei de uma conferência em South Hadley, MA, ontem. 12 horas de viagem na ida e na volta. A conferência (Gordon Research Conference: Origins of the Solar System) foi ótima. Encontrei algumas pessoas de outros países, mas a maioria absoluta eram americanos, como o esperado. Foi um encontro de astrofísicos, planetologistas, geólogos e geofísicos. Um grupo bem amplo de cientistas, mas mesmo assim não estava lotada, talvez umas 140 pessoas no total. Com tanta coisa diferente, não dá pra entender tudo, e é fácil ficar perdido nas apresentações fora da sua área, mas mesmo assim dá pra aprender uma coisa ou outra. Mas é interessante ver os vários grupos tentando interagir entre si, tentando ligar as coisas, e engraçado às vezes, os conflitos entre teorias de várias áreas diferentes tentando explicar a mesma coisa. À noite, após o jantar e o término das palestras, havia uma segunda sessão de posters, mas com cerveja de graça. Eu que não sou fã de cerveja, bebia pelo menos umas duas long-necks por noite. Infelizmente não tinha nada do meu gosto. Tive que beber uma cerveja chamada UFO, que não é muito boa, mas eu tive que experimentar só por causa do nome.

Comi lagosta pela primeira vez na vida, e é uma tarefa árdua pra dizer o mínimo, pelo menos pra primeira vez. Tinha até um manual de instruções ensinando como fazer! HAUhUahUAHuHAuHAuhAa... Bom... Comi, e não gostei muito, mas valeu a experiência. Foi divertido aprender o processo. Duas das pessoas na mesa, desistiram de comer na metade, achando muito difícil, mas eu não desisti até o final, e cumpri a missão! Ha! Talvez eu demore um pouco pra querer comer lagosta de novo, mas não é tão ruim que eu não queira comer nunca mais. Só tem um gosto diferente...

O lugar onde foi realizada a conferência, Mount Holyoke College, é muito bonito também. Tirei algumas fotos que depois eu vou disponibilizar na Internet.

The Ann Arbor Adventure - Part I

From today onwards I am going to write about my next big adventure, my life in Ann Arbor. I am going to a totally unknown place, knowing no one, and I still do not know where I am going to live. It will be like start everything from zero. The only thing I know is that I am going to continue my PhD research at the University of Michigan, and the name of my US supervisor.



Just to update everyone, my journey will start in May 24th, and not May 23rd as I have told you before. My ticket to Ann Arbor is reserved for that day. Today, I also sent all the remaining documentation required by the University of Michigan for it to send me the DS-2019 form. This is the form that I need to show at the US consulate or embassy to receive my US VISA. This form has also been sent to me today.



This is just the beginning, and for now on, I am sure a lot of things will change in my life. And I am also sure, that it will be all for the better. ;)





Current Primary Quest: To gain a US VISA.



Secondary Quest: To find a place to stay in the first days at Ann Arbor.







29 days left in Brazil, and counting down...

Countdown to Ann Arbor

"Take heed and bear witness to the truths that lie herein, for they are the last legacy of the Horadrim... And so it came to pass that I decided the exact day to my trip to the United States, and that will be at May 23rd. I am going to spend the next 10 months in Ann Arbor, doing part of my graduation research. And some time around March 2008 I will return to Belo Horizonte. "

Now I will start the countdown to US.

30 days left, and counting...

Fellowship and TOEFL score

My fellowship to finish my PhD at the University of Michigan has been granted. Now I can start to proceed with my preparations to go to Ann Arbor, and run after a Visa to the US.

Today I also got my Toefl score, and I got a very good score. My score is 106/120. I still need to receive it by mail at home, and after that send them to the University to conclude all the procedures to get the above mentioned fellowship.

And I also was succesful in my quest to not use MSN Messenger for one week! Yeah!!

57=3 x 19

Idas e vindas...

Uma amiga minha de São Paulo está indo para os EEUU amanhã, e deve ficar lá até o final de dezembro. Ela está indo para Washington DC. Este fato acabou me lembrando de que neste último ano, vários dos meus amigos têm ido embora.

Dois deles foram fazer o chamado doutorado "sanduíche", assim como essa minha amiga de SP. Um está atualmente no Hawaii, e a outra está na Bélgica. Logo, logo, eles estarão de volta. Voltarão em maio, eu acho. Ambos são do grupo de Astrofísica da UFMG, o mesmo do qual eu faço parte, e aquele laboratório não é o mesmo sem esses dois. Eles fazem muita falta por lá!

Um outro grande amigo meu, também da Astrofísica, resolveu fazer o doutorado todo na Espanha, em Barcelona. Pelo que eu sei, ele anda se divertindo demais por lá, e espero que ele se divirta mesmo. Ele deve voltar ao Brasil eventualmente para visitar a família, mas depois que ele terminar o doutorado, nada impede dele ficar por lá definitivamente. Este é um sujeito que vai fazer falta por aqui. Apesar disso, tenho certeza que vou encontrá-lo muito por aí ainda, e com certeza vou visitá-lo em Barcelona assim que for possível.

Outras pessoas mudaram de BH, e foram para outras cidades, algumas não tão perto, outras não tão longe, mas mesmo assim, foram embora. E aquela coisa de resolver sair do nada pra algum lugar, pelo menos com estes, não vai funcionar mais.

Foi um ano muito estranho. Foi a primeira vez que eu vi esse tipo de coisa acontecer de maneira tão drástica, e com várias pessoas tão próximas. Grandes mudanças. Vou encontrar todos novamente, afinal, amigos serão sempre amigos. E claro, com o tempo a gente acaba fazendo novas amizades, e isso acaba sendo divertido.

Ainda este ano, se tudo ocorrer como planejado, quem vai passar alguns meses fora, vai ser eu. Só espero reencontrar as pessoas que estão voltando, antes de ir. Também devo ir para os EEUU, mais exatamente, para uma cidade chamada Ann Arbor, no estado de Michigan, bem perto de Detroit. Espero conhecer pessoas legais por lá, e também espero que quando eu voltar novamente para o Brasil, reencontrar todos os velhos, e novos amigos.

Bom! Ainda nem sei se vou, o resultado da bolsa do doutorado "sanduíche" deve sair semana que vem. Se eu for realmente, devo ir no final de maio, início de junho. Então ainda tenho um tempo por aqui! E se você ler isso aqui, Srta. Aline, a senhorita está intimada a me visitar lá nos EEUU, e assim que possível, pode saber que eu vou te visitar em Washington também! ;)

My Mistake

And so the mistake was mine. The code was correct, and was working properly. I have failed to see a small detail in a function called by the program. Everyone is happy, everything already published is correct, and now the work goes on, as before.

Back to decipher the code!

Resumo

Gostaria de reiterar sobre o objetivo principal deste blog. Alguma das últimas mensagens podem parecer totalmente sem sentido. E elas realmente não tem sentido nenhum, e este é o ponto. Claro, para a pessoa que escreve, existe realmente um sentido oculto naquilo. Quero dizer que vocês podem ficar à vontade lendo, e se quiserem podem fazer um esforço de tentar entender o sentido oculto da mensagem, ou ainda interpretar da maneira que for mais conveniente para vocês.

O objetivo aqui é o Caos. E em várias das mensagens, eu estou tentando brincar com isso. Algumas são mais sérias do que outras, mas os momentos são assim realmente. Espero que os puristas da linguagem não achem ruim quando eu misturar inglês e português na mesma mensagem. E eu vou continuar escrevendo tanto em inglês quanto em português. Infelizmente meu alemão não é tão bom de modo a poder misturá-lo às mensagens também. E claro, eventualmente, eu ainda vou usar "scramblespeak", aí sim que ninguém vai entender nada. Se alguém leu a "scramblepoetry" a alguns dias atrás, eu digo que "scramblespeak" é algo parecido.

Qualquer dia eu falo sobre o limbo, nunca falei dele, e ele é importante. Apenas tenho que estar mais inspirado.

Eu ainda gosto do número 897, portanto ele ainda fica escondido por aí. Quando eu achar um número primo legal, eu o coloco aqui. Normalmente, eu fatoro números de placas, ou número das comandas de restaurante, em busca de novos números primos, de cabeça, mas não tenho feito isso ultimamente.

Eu já zerei o "Guitar Hero", e já nem estou jogando tanto quanto antes. Cansei de jogar PS2 de novo.

Ainda estou esperando o e-mail da minha co-orientadora, falando sobre o erro no código do programa.

Nunca mais vi a menina "heavy metal" com os braços todos marcados por cortes que eu encontrei no ônibus. E nunca mais sonhei com a menina dos olhos verdes brilhantes, mas encontrei com ela pessoalmente.

Estou lendo um livro chamado "O Despertar dos Mágicos". Um dia eu falo mais sobre ele.

E a Vida continua. O Tempo ainda passa, mas eu ainda descubro uma maneira de vencê-lo. O Mundo continua gigantesco com suas ilhas minúsculas no meio do pacífico. A Dor um dia desaparece, e eventualmente aparece de novo. Medos são difíceis de vencer, mas devem ser vencidos. Os Fantasmas ainda assombram. Mas sempre haverá a Esperança na busca de um novo dia, melhor que o anterior.

O Castelo continua em construção. E o Diamante, ainda bruto, continua sendo lapidado. Os Olhos brilharão novamente, a Força retornará aos músculos. O Propósito primordial voltará a consciência. O jovem Dragão ousará voar alto, muito alto.

Continua...

Possible error

Today I have discovered a possible error in the codes I use in my PhD studies. The error is in a subroutine that calculates the velocity gradients of the system. This program is being in use for almost 15 years, and no one has ever spotted this error. If I am mistaken, and I just have missed something, and in the end there is no mistake, excelent! Then life goes on... But, if I am not mistaken, and the error really exists, then the results already published using this program will have to be reviewed.

It is the second error I found in the codes. The first one, fortunately was in a function that was used only once over the program. After the change, the new results did not have any difference from the previous results. This second error was in a function that was called thousands, maybe millions of times, during the course of the program. The results after the changes were totally different from the previous ones.

I have showed it to my advisor, and she also thought that there was an error there. I have also sent an e-mail to my co-advisor in the US, reporting what I have found. She still did not reply... She was one of the people who wrote the program years ago, and use it ever since... I am just waiting her reply to be sure of the mistake, or to know that the mistake was mine... I just hope the mistake was not mine!

Waiting.

(...)

Return to work

Carnaval ended and now it is time to return to work. Return to my more-than-a-hundred-page program code. Reading and understanding all the physics behind that code is not so easy as I early thought. I guess I have passed already more than half of the code, but now I'm on the worst part, where we have all the physics, all the radiative transfer and line profile calculations.

Radiative transfer is one of the most beautiful physics's subjects, but it is also the most difficult subject that I have seen. For people who doesn't have any idea about what is radiative transfer, it is the study about how light or radiation propagates through a medium, including absorbtions, scattering, emission and re-emission of light due to atoms, molecules and dust throughout the medium.

There are a lot of simplifications in the code, concerning radiative transfer, but even so it is still not a simple thing. The magneto-hydrodynamics calculations, also done by the program, seems really simple compared with the afore mentioned one. And I tell you, magneto-hydrodynamics have nothing simple about it.

Magneto-hydrodynamics is the study of charged fluids in the presence of magnetic fields. It is also a fascinating subject, but also a very difficult one.

I just expect that someday I could understand properly both subjects. They are really fascinating!