Sunday, August 19, 2007

Disambiguation

"A string is an ordered sequence of symbols [...] Even variable length strings are limited in length; although, generally, the limit depends only on the amount of memory available [...] String concatenation is an associative, but non-commutative operation. The empty string serves as the identity element [...] Representations of strings depend heavily on the choice of character repertoire and the method of character encoding."
[extract from Wikipedia]

"A loop is a sequence of statements which is specified once but which may be carried out several times in succession [...] In many programming languages, only integers can be reliably used in a count-controlled loop. Floating-point numbers are represented imprecisely due to hardware constraints [...] Sometimes it is desirable for a program to loop forever, or until an exceptional condition such as an error arises. For instance, an event-driven program may be intended to loop forever handling events as they occur, only stopping when the process is killed by the operator."
[extract from Wikipedia]

    DO
    WHILE(wondering what's up with her today)

    IF(IQ > 100) THEN {smile;}
    ELSE {scratch head;}
    IQ = IQ + 1 ;


    END DO

34 comments:

QUASAR9 said...

Hi Bee,
Cosmologists believe that the universe went through a rapid period of expansion known as inflation.

But, says Pedro Ferreira at the University of Oxford, they usually ignore the effects of temperature on inflation - and that's a big mistake. "At the violent temperatures we assume are around at the time, everything would be moving rapidly," he says.

"Space-time itself would be bubbling and boiling."

Ferreira and João Magueijo, currently at the Perimeter Institute in Waterloo, Canada, realised that any such thermal "noise" would have been amplified during inflation. If the noise had been too loud, it would have disrupted the formation of galaxies and left behind huge imprints on the cosmic microwave background today

How the big bang chilled out

Uncle Al said...

http://www.canada.mensa.org/

I cannot believe how incredibly stupid the mob is. I mean rock-hard stupid. Blazing hot mid-day sun on Mercury stupid. Surface of Venus under 80 atmospheres of red hot carbon dioxide and sulfuric acid vapor dehydrated for 300 million years rock-hard stupid. Stupid so stupid that it goes way beyond the stupid we know into a whole different sensorium of stupid. The mob is trans-stupid stupid. Meta-stupid. Stupid so collapsed upon itself that it is within its own Schwarzschild radius. Black hole stupid. Stupid gotten so dense and massive that no intellect can escape. Singularity stupid. The mob emits more stupid/second than our entire galaxy otherwise emits stupid/year. Quasar stupid. Nothing else in the universe can be this stupid. The mob is an oozingly putrescent primordial fragment from the original Big Bang of Stupid, a pure essence of stupid so uncontaminated by anything else as to be beyond the laws of physics that define maximally extrapolated hypergeometric n-dimensional backgroundless stupid as we can imagine it. The mob is Planck stupid, a quantum foam of stupid, a vacuum decay of stupid, a grand unified theory of stupid.

The mob is the epiphany of stupid. The mob is stooopid.

QUASAR9 said...

Because we can get a computer that understands a certain sequence of code, to perform a simulation ...
does not mean the universe follows the same path (math).

We may be living in something like a computer generated universe, but the difference is that whilst one can play/replay a computer game endlessly, one is simply jumping from point to point.

In the Universe - we are in the game. And there is no replay. Well if there is it is not in our hands.

"The best thing about CERN is that it enables us to play & replay the conditions that may have existed at the moment of the big bang ... whereas you only get one go at the original event" - Dr Brian Cox

At least 'only' one pertaining to the spacetime Universe we ARE IN.

Anonymous said...

:-)

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I think by now I qualify for mensa...

Bee said...

Hi Uncle,

I guess you've just discovered the fundamental law that drives the evolution of the universe: maximization of stupidity. I guess I have already contributed more than my share, so I could slow down somewhat for the rest of my life ;-)

Hi Quasar,

Ah, thanks for pointing that out. Why would one expect the universe to start in thermal equilibrium? I don't particularly like the idea that we live in computer. I'm too tempted to ask what the computer is made of. I can live with the universe running on an algorithm though. Floating point? Best,

B.

QUASAR9 said...

Bee,
when we observe the redshift of an object billions of light years away we are neither observing where the object IS now, nor the speed and direction in which it is travelling now, but it would be logical to assume it was travelling away from some point at some time.

However NOW or billions of years later it may have reached its final destination which would and could be well beyond the 'cosmic event horizon' of the observable universe (or even exist no more)...

Bee said...

Hi Quasar:

'now' doesn't make sense without a 'here'. The question what happens 'now' somewhere else rests on a definition of time (or a definition of 'now' if you like). It doesn't even work in special relativity, see e.g. here - not necessarily now ;-). In GR the situation is somewhat more involved. On the one hand one can use the CMB to define something like a restframe, on the other hand evolution backwards and forwards in time rests on the theory's accuracy, i.e. the matter content and how well we understand its equation of state. Best,

B.

Neil' said...

Here's something that I find ambiguous: Symbols for the dimensions of space and time are used in confusing ways. We have to keep track of: large familiar (3), those plus time (4), compact (7 ?), and large but extra(?)! I have seen N for the number of large space dimensions in older works (The Anthropic Cosmological Principle, and typical old Amer. J. Phys. about extrapolation of physics to higher dimensions.) I have seen d and D used almost interchangeably for large space or large space + time, but also for number of extra dimensions, or for total of large space + time + compact etc. I see lower case delta for number of extra dimensions - it really gets confusing.

Is there an accepted nomenclature for space-time dimensionality? Especially, for the plain old large dimensions.

John Wilkins said...

According to that program, my 19 years of marriage have given me an IQ of 4,562. It's as well I divorced, or I'd be up around 10,000 by now. [Which is a way of saying that loop never terminates :-) ]

Arun said...

I think your loop

IQ = IQ + 1

increases the IQ of the rest of the universe only :)

Anonymous said...

"Why would one expect the universe to start in thermal equilibrium? "

The most probable state for any system to be in at any time is equilibrium, right? So the universe should have started in equilibrium if its creation was a random process. But it didn't start in equilibrium...hence....

QUASAR9 said...

lol Bee,
anything man made can only be a very poor (and tiny) imitation of the real thing - even colliders.

I have no problem with cults who religiously engage in ritual mantras and meditation, you know like mathematicians, theoretical physicists, chemists, engineers, bio-engineers or the medical sciences.

Human existence is a sequence of rituals, and particle physics is a sequence of (predetermined?) phases.

Turning theoretical physics into applied physics and engineering is a sort of mantra induced religious ritual.
Glad you are having fun!.

QUASAR9 said...

Hi Bee,
we can estimate something to be x billion light years away from us here now - but we cannot estimate where x is now ...
else we shouldn't be 'looking' at the sky we see, but rather at the sky as it IS (should be) now.

If we are looking at something 4 or 5 billion light years away, we are literally looking at something that was before our Sun and solar system came into being ...
as Joanne Hewett would say: "take a (powerful) telescope look up at the night sky and say hi to your ancestors"

QUASAR9 said...

PS - Bee, the point I was making about the redshift of an object billions of light years away, is that sais object may have 'now' come to rest (or even burn out) therefore one should not assume it to be proof that the universe IS accelerating or expanding ... but rather as proof that the universe was accelerating or expanding (at the time) billions of years ago.

The Cosmic Event Horizon IS relative what we 'here & now' see, measure or observe.

CapitalistImperialistPig said...

I believe there is a sign error in IQ incrementing statement.

Bee said...

Hi Neil:

No, there isn't. What do you expect? We can't even decide what paper format to use!

Hi Arun:

Well, since the average IQ is defined to be 100, by raising the IQ of my visitors somebody else's IQ has to decrease, no? Occasionally I'm afraid it might be mine.

Hi Quasar:

as I said, expectations about time evolution rest on our understanding of the theory used, in this case GR. In principle, yes, it might be that the universe is being destroyed by an alien civilization and collapsing into a black hole but this information hasn't yet reached us. It's the same issue like: if the sun would vanish right 'now' then it would take 8 minutes until we notice. Reg. the question of 'now', see my above comment.

Hi CIP:

I leave that task to other people.

IF(IQ gets too large) THEN (GOTO TRF);

I believe you'll be back rather soon ;-)

(Unless of course you're no longer able to even click a button that is.)

Best,

B.

Bee said...

Hi John:

How nice, I'll have to ask my husband how often he's running through the loop. I believe our relationship has significantly improved since we have my imood in the sidebar.

It's as well I divorced, or I'd be up around 10,000 by now.

I guess that's exit on error. On the other hand it's kind of interesting that an IQ of 4,562 wasn't sufficient to figure out what she's up to :-)

Hi Anonymous:

The most probable state for any system to be in at any time is equilibrium, right?

It's the most probable state for a system to reach, given a sufficient amount of time (equilibration time). Stating the initial configuration was 'random' isn't the same as saying it was in thermal equilibrium. Things can be random in various ways. E.g. you might want to random distribute energy with constant probability over all scales - that would not be thermal.

Best,

B.

Anonymous said...

xdw"It's the most probable state for a system to reach, given a sufficient amount of time (equilibration time)."

You are assuming that the system was not in equilibrium to start with. That is a very unusual situation, which requires explanation. Being in equilibrium does not require explanation. Suppose I said to you, "I just took a bag full of 10000 Canadian $1 coins, and threw them onto the floor; 5116 ended with the Queen's head up, the others down." You would say, "So what?". But you would react differently if I reported that all 10000 had come out heads up. You seek an explanation when a system is in a very small region of phase space, not when it is in a huge region [=equilibrium]. If the universe is created as a result of a quantum process, with *no other principle involved*, then it is most likely to be created in equilibrium.

"Stating the initial configuration was 'random' isn't the same as saying it was in thermal equilibrium. Things can be random in various ways. E.g. you might want to random distribute energy with constant probability over all scales - that would not be thermal."

Right. But that will only happen as a result of some "law of nature". Likewise, our Universe should have been born in equilibrium --- but it wasn't. So there must be some as-yet-unknown law forcing it to be born in a tiny region of phase space.

Bee said...

Hi Anonymous:

You're running in a circle. One way or the other you have to come up with an initial configuration or a random distribution. I don't like to call it a 'law of nature' - this is what I would call the evolution equation, not the initial condition.

Right. But that will only happen as a result of some "law of nature".

As much as thermal equilibrium is only reached as a result of some 'law of nature'?

Suppose I said to you, "I just took a bag full of 10000 Canadian $1 coins, and threw them onto the floor; 5116 ended with the Queen's head up, the others down." You would say, "So what?". But you would react differently if I reported that all 10000 had come out heads up.

That's because you have implicitly assumed the probability for each coin is 50/50 up/down, which gives you a sense of 'randomness'. Thermal equilibrium is a distribution that is favoured if a configuration had time to equilibrate - then it doesn't matter what initial configuration you start with. That doesn't mean though the initial configuration should have been thermal equilibrium. Best,

B.

QUASAR9 said...

Sort of comforting to know we are 'invisible' to anything more than 5 billion light years away - the Sun and our solar system just don't exist yet.

If the Earth were to vanish right now, those more than five billion light years away wouldn't even notice, or know whether terrans had existed. Alas existence is so ephemeral and 'life' so fickle. The best we can do is have some fun

Bee said...

well said, Quasar. Have a nice day - B.

Anonymous said...

So you're saying a loop is a brane?

Arun said...

Branes (as opposed to brains) have no IQ. Therefore B cannot be doing a string theory calculation - which is what her clues might lead you to believe.

Bee said...

my brain is unfortunately full with multiply entangled loops. I find it kind of interesting that the notation for a string in perl starts with $. anyway, if I was to work on one or the other I'd probably just call it differently so I could work in peace. maybe we should do the politically smart move and just rename the whole field. As I've suggested previously, let's follow a well known world leader and call it Theory of Everything related Program Activities ;-)

Arun said...

I find it kind of interesting that the notation for a string in perl starts with $.

The value of any scalar variable in perl is obtained by $ and array by @.

island said...

Thermal equilibrium is a distribution that is favoured if a configuration had time to equilibrate - then it doesn't matter what initial configuration you start with. That doesn't mean though the initial configuration should have been thermal equilibrium.

Nor do we have any actual evidence that would indicate that it ever was, without making a bunch of assumptions and projections that might not even be justified if we'd just pay attention to what the actual evidence is most apparently telling us.

Like... the second law says that the entropy of the univere **always** increases.

Thermal equilibrium isn't the favored distribution over time when the initial conditions include inherent instructions for stucturing that produces far from equilibrium dissipative systems, like, black holes, supernovae and us, that are all capable of isolating enough energy to make matter/antimatter pairs from condensed regions of the rarefied mass-energy that comprises the negative pressure vaccum of the expanding closed system.

The negative second law... ;)

...and/or, Asymmetric transisitons.

stefan said...

Hm...

I'm wondering so often what's up with her that day, but even so my IQ may increase each time by one, I end up often enough just scratching my had ;-)

Cheers, stefan

island said...

Transitions, I mean.

Anonymous said...

"That's because you have implicitly assumed the probability for each coin is 50/50 up/down, which gives you a sense of 'randomness'."

Do you object to that?

Note that the coins did not start with 10000 heads up and then work their way towards some more probable configuration. I just ask you: I have a room in which I [once] dumped 10000 coins, each of which is known to have a 50% chance of coming up heads. Tell me roughly how many came up heads. Surely you will give me some number near to 5000, simply because there are more ways for that to happen; nothing to do with equilibration, right?


"Thermal equilibrium is a distribution that is favoured if a configuration had time to equilibrate - then it doesn't matter what initial configuration you start with."

Yes, that is the right way to think under normal circumstances. But the beginning of the universe is not a "normal" circumstance. As you know, the reason that out-of-equilibrium states move towards equilibrium is simply that the volume of phase space corresponding to equilibrium is so vast -- this is the standard statistical mechanical explanation of the second law. But now suppose you are creating a universe. :-) You can choose to start it in some extremely tiny region of phase space [which is what our universe actually did]. Your choice is made for some reason [ie in accord with some principle]. That amounts to a law of nature, and it is the job of physicists to find out what that law is. Alternatively you might just throw a dart at a picture of phase space. Then it is overwhelmingly likely that your dart will hit equilibrium. That is the most probable initial state in the absence of some law of nature.
In exactly the same way that a room full of 10000 coins is more likely to have 5235 heads than 9999. If you really found 9999 you would demand an explanation, ie a law that somehow enforces this otherwise ridiculously improbable situation. You expect some number like 5235, *Whether or not* there has been time for "equilibration".

In short, equilibrium is the most likely state for a system at *any* time, not just after the passage of time. This is why the arrow of time is so mysterious. Our universe started out far, far from equilibrium, and we have to explain this fact.

Bee said...

Hi Anonymous,

Luckily we are presently far from equilibrium, otherwise I pretty much wouldn't sit here and type these words. I have the impression you're not really trying to understand what I am saying. I don't 'object' on starting with an initial probability distribution, I am just saying you have to assume it. Whether its equally distributed (as with your coins) or thermal, it's an assumption. The statement In short, equilibrium is the most likely state for a system at *any* time, implies you have a sense of 'likely' - that's what I am telling you all the time: it builds up on a probability distribution. Besides this, I think I agree on the last two sentences anyhow. Best,

B.

Dr Who said...

I think that both anonymous and B are right. :-)

In his paper that I recommended to B [and I recommend it to anonymous too] Albrecht classifies approaches to the arrow of time into "dynamical" and "based on principles". If you don't believe that the initial conditions of the universe were selected by some principle, then you are assuming that all points in phase space are equally likely. With that probability distribution, the most likely state for the universe to be born in is indeed equilibrium. Then you have to use dynamics to explain why our universe somehow *looks like* it wasn't born in equilibrium. On the other hand, if you believe in some principle [like for example Penrose's Weyl Curvature Hypothesis] then you are doing what B is hinting at: you are skewing the a priori probabilities --- certain points in phase space are more probable than others. Anonymous is right about the coins --- unless Canada introduces a law forbidding anyone to place the Queen's face in contact with the floor....which suddenly makes 9999 heads up quite probable! Clearly both approaches have serious problems.....and that is the *real* reason the arrow of time is mysterious!

Bee said...

Hi Dr. Who,

Thanks. I didn't say a. is wrong, I tried to clarify the assumptions, i.e. the word 'probable' rests on a probability distribution. Yes, the most 'natural' one seems to be one that is constant, I'm not even objecting on that. Best,

B.

PS: Haven't yet had the time to read the paper, sorry.

Dr Who said...

"Haven't yet had the time to read the paper, sorry."

No need to apologise. Take your *time*, hahaha

Oh boy this subject really generates a surprising amount of what Americans call "lame" humor. I wonder why.....

Neil' said...

Speaking of the likely state for the universe to be born in, etc:
If the underpinnings of our world promote variation in kind (different kinds of laws, etc.), then the use of the Multiverse and application to it of Bayesian type reasoning (about what more to expect given what we already see) seems unavoidable and useful. For example, if there's a "Landscape" of possible ways for the universe to turn out, given "strings" as the fundamental building block, etc., then we have to ask: if we are in a certain subset of what is possible from that matrix, what likelihood for other features? I mean, suppose that 10% of those Landscape-possible universes (total including their chance of existing, not just as portion of description space) sharing our currently known properties, should also have property X. Then "at random" there's a 10% chance our world has property X - do you agree? It can even be tested to some extent: See how many of the predictions come true, of course.