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[NOTE: This is a direct translation from Spanish using atla-vista, please excuse the English.]

Juan Manuel Physical Rodriguez • Parrondo

"the turn out to join two negative things can be positive"

MÓNICA SALOMONE, Madrid ( 05-01-00)

Rodríguez Parrondo, en la
Universidad Complutense (U. Martín).

There are times in which two bad followed results can give rise one good one: it says the paradox to it of Parrondo. Juan Manuel Rodriguez Parrondo, of 36 years, physicist, professor of the Complutensian University of Madrid, has created two games of chance that more and more intrigue peculiar engineers, mathematicians, biologists and in general. If one always gambles one of both, anyone, the probability of losing is very high, but, if they are alternated - it gambles the one and following one to the other once -, that before lost becomes winner. Parrondo was inspired by a biological problem in which the protein transport takes part the chance inside - of the cell and now others look for more systems in than the paradox is revealed again. The past December the games in the Nature magazine were explained , in an article nonsigned by Parrondo.

It asks. Everybody does not have a paradox that takes its name, although the articles published on her are not his. How it is that?

Answer. The truth is that it seems to me amused that the games have become so famous without not even publishing them. Although I do not know if they will consider it at the time of evaluating my investigation. When I began with the games, two years ago, I did not want it to publish, because, for which it works in my field, this is a species of translation from a language to another one. The peculiar thing is that, when you change the language, the reach is multiplied and suddenly many persones are interested more. And the one of the games pierces much, because everybody understands it.

But how they became famous without they had been published?

I gave several seminaries. An Australian engineer with who I collaborate, Derek Abbott, attended one of them and it liked much. It is the one who first spoke of the paradox of Parrondo, and since then has given to char them in many sites. He is very active. My agent has become something as well as!

He is the author of the article in Nature. It had not liked to sign those articles you?

If it had signed I, they had not been able to him to put my name to the paradox. In any case there are articles that will leave now in that yes I sign.

How arose the idea from the games?

I take care of estocásticos models: something that varies randomly in the time. In concrete work with mathematical models that they describe the protein transport in the cell, that takes control of a species of very small molecular motors. In the world of the very small everything it is vibrating permanently, and those random fluctuations of movement, call " browniano movement ", are inescapable; what the motor makes molecular is to take advantage of them. One had always thought that they were destructive, that they prevented that the system worked well, and however the motor of the protein indeed uses the random character of the movement. There was a mathematical model that tried to explain it and by him the games are inspired.

But how one goes of proteins to the chance games?

In fact, the models of brownianos motors, that are called ratchets, describe the movement of a submissive particle to different fields from forces. Instead of speaking of position of the particle, I speak of gain in a game. It is a translation. I realized of which in these ratchets the particles oscillate between two states; in each one of them the particle goes, we say, towards the right; but when it oscillates between both states the tendency is reversed and the particle goes towards the left. And you say, man, what peculiar, have two things that when they are combined make the opposite who single! I translated that to a language of chance games.

Are others ratchets in addition to in the molecular motors?

Ratchet forces the particle to do things taking advantage of the chance. The word ratchet is in Spanish " pawl ": an dentated wheel that only can go in a direction, because in the opposite the teeth prevent it. The clocks that work with the movement of the wrist, that is random, are an example. One ratchet at random turns those movements into a systematic displacement in a direction, that is what is giving prudent the clock. This is the same: you have a risky movement and a field of forces that catch it.

Explain a little more how they are the games.

There is a game, the A, that consists of throwing a pocketed a ball currency so that a face leaves less, and game B gambles with two currencies: the 2, that are very bad - tenth of probability of gaining and nine tenth to lose -, and the 3, that is a winning currency, lose with probability a quarter and gain with probability three quarters. The rule of game B is that currency 2 is used if what I take cattle is multiple of 3, and currency 3 if it is not it. As only one of each three numbers is multiple of 3, the B also is a losing game. Then if we played the game To or game B all along, there is somebody always has a very great probability to lose. But if we once played the A and another one to the B, the one that before lost now wins. That one is the paradox. It is a game of simple chance.

Those rules of the multiple of 3 et cetera, can be changed?

Some things can be changed, but not all. There are mathematicians who study the possible alterations now.

What aspects are treating those that work with the games?

They are doing mathematical simulations of the game and studies. Also we analyzed the relation between the games and the information theory, and this yes that I sign. But it has little still, is something that is beginning. I have more ideas to continue.

Can be applied the paradox to any thing? It does not seem very simple.

It is possible to be generalized enough. The essence of the paradox is that in game B there is a good currency and a bad one, and then, when you only play the B, the effect of the bad currency wins to the good one; but, when you combine it with the A, that game causes that it takes part plus the good currency of the B: it changes the frequency with that you play the good one and the bad one. He is something that yes I think that it has more general applications. You have a positive tendency and a refusal, and the refusal wins to the positive one. Joining them to one third refusal, although it is it, of some form it influences in the other two and it causes that the positive one plays a greater role. Yes I believe that it can have more general applications. Also it can be useful for those who make models probabilísticos. It is a peculiar effect, antiintuitive, and agrees that they have in the head that can happen this. You have two negative things and, if the meetings, you think very intuitively that also the result is going to be negative. But it can thus not be. The games say to you " exists this, ten well-taken care of ".


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