All posts by savagephysics

There is no measurement problem…

As there is an obvious lack of pertinent information about this subject and as I am relatively tired to do something else at this late time and because tomorrow I have a trip to a conference I will focus now on a relatively simple but very abused problem… The wanna be “measurement problem”. 

The people can be divided in physicists and non-physicists. This is not the only division but it makes sense at this moment. The non-physicists may be passionate about physics while having little technical knowledge about the subject. They listen to what physicists say and try to understand things assuming physicists know more… Sometimes this might be true, sometimes not and sometimes physicists simply have to profit from keeping anyone they can at a high level of ignorance. 

This might be the case with the so called “measurement problem”. Now, in order to understand what this is about one should go back some time, at the beginning of the past century when experiments of all sort started showing that questions assumed to have been formulated correctly were in fact ill-defined… These were the first years of quantum mechanics. 

One of the observations was that specific questions about a system and its parts were not perfectly definable in an absolute sense and all together, independently. Moreover, one observed that while single measurements were fundamentally unpredictable, there was some sense one could make out of the statistics of many measurements performed in contexts as similar as possible. 

At that moment it became clear that while for some questions a single measurement could in principle give a pretty much ok answer, in most of the cases, additional information was encoded such that it became visible only after performing many experiments and making a statistics. This happens because the questions themselves determine a part of the answer. For example, take a particle of spin 1/2. One knows from general laws that the spin of a particle is determined by some fundamental laws of nature. However, there might be another object that can in fact be observed, namely the projection of that spin on an axis. However, that projection can only take 2 values : +1/2 and -1/2 (of some units that I never care about)… Now, surely, the projection of a spin on an axis is a measurable outcome and it is observable but cannot be defined as a “state of the object” in the absence of a given axis. As the choice of an axis is arbitrary there is no law of nature to tell you what projection you will get, picking this or that axis every time. You can of course prepare the experiment such that your spin 1/2 particle will give always +1/2 when measured with a GIVEN axis but then, you are free to change that axis. The point is, there is no “a-priori” state of a “projection upon an axis” if there is no axis given. 

This principle must be really well understood: for example the question “what is the color of the night?” might sound poetical, even philosophical, but still, it is ill defined unless you specify something else… 

Ok, so, say, you pick an axis and with your experiment that doesn’t care about spin projections you start making measurements. Your statistics will show 50% of the cases with spin up and 50% with spin down (say). 

The experiment is completed and the problem is solved… 

Now come the “measurement problemists” into the debate. They that as long as they measure the spin with respect to their axis as being up the real physical state of the spin projection must have been up beforehand… Of course, stated in this way, their objection is meaningless… again, what axis? There is no axis on which to project unless you use an apparatus with an axis in it… But, they say, no, there was some spin that was like an arrow that was actually oriented the way I choose to put my apparatus… Really? Then let’s take another apparatus, somewhere further on the path of the same particle and rotate it with say, 23.4773 degrees to the left… What will you get? Well, according to the angle you will get either a spin projection up on the new axis or a spin projection down on the spin axis… there are no intermediate situations, that is the law of nature… The two outcomes will have different statistics in a probabilistic experiment but you don’t want to know about statistics… you want to know what the spin projection is in an “absolute sense” and get some idea what the “actual spin orientation of that thing” is… What you get is … well… one of the two situations: up or down… nothing in between… Was there a state before that measurement? well… it was a state defined with respect to the previous axis. The new axis changes the problem for the single electron… 

Ok, say you are a diehard skeptic or you just got a large grant allowing you to do “research” in this field and you want to keep the public opinion focused on the “mystery” because you want further funding for doing nothing… 

Then, the measurement pseudo-problem reveals itself in another “situation”… What these strange people say is that the wavefunction is a physical object that propagates through space etc. That wavefunction however is nothing like that… in fact, it contains all the information about all possible outcomes and all these outcomes are propagated in some perfectly local and deterministic way from one measurement to the next. Fact is, the wavefunction is an “expectation catalogue” as Schrodinger put it… it is the maximal set of knowledge we have about the system and it encodes all possible outcomes. When we measure the property of the system we give it physical meaning. Of course, some states of the system have physical meaning in any situation. For example electrons have spin 1/2 independent of measurement axes etc. So, the wavefunction (expectation catalogue) for that will be only 1/2 and that’s it… However, for the spin projection one has to consider the interference of more than one possible outcome. One locally propagates both and interfere the expectations through the statistics of the outcome. The answer quantum mechanics answered perfectly is “how do our expectations correlate?”… This is a very important question as there was a problem in deriving this via classical probabilities. 

The “measurement problemsists” say that the wavefunction is a “state of the system” and say they want to know what happens to the wavefunction “of an electron” when its spin projection is “measured”… See, there are already a few mistakes… the wavefunction is not of ONE electron… it is the wavefunction describing expectations for a statistics of outcomes involving many electrons… There is no “jump” in any sense in a physical substance when a measurement is performed… The measurement just adds the “little extra” that makes a question well defined… 

However, there were LOTS of experiments trying to measure the actual “physical” wannabe “process” in which the electron hops from a state of being “up and down at the same time” (lol) to a state of being only “up” or only “down”… these experiments were all failures and the laws of nature had a fun time laughing at the stupidity of the funding bodies of those “experimentalists” or “theoreticians”… 

I think that is all for this night… 

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Axiom of Choice

One day I will have to write a long post about the axiom of choice, Zorn’s lemma, uncountable sets etc. What is the prescription of choosing one element from a set of arbitrary sets of real numbers? What are the implications of this in Quantum Field theory? What are the implications of these in string theory? What are the implications of this in standard quantum mechanics?

Computers in science

You may be using a computer… I am using one right now. It is a marvel of engineering, I have to say that. However, I am not a computer fan… I started looking at a Commodore 64 when I was 7 and I was pretty impressed by it at that time… By age of 15 I tried all possible games and now I don’t have a single game on my computer… (although from time to time I may look at an old web game, but “from time to time” 2 minutes every 6 months or so…) I dislike computer games all in all, although I programmed my own game when I was 16 and bored to hell during a summer… it was something very simple, a few rules for the movement of some objects and some deformations and some gravity but more or less that was it… I completely gave up computer languages and programming immediately after high school and I have no intention to return (except if starving or begging)… Why am I saying this? Well, my experience with formal languages is that they are incomplete and ill defined. Say, I believe there may exist a value of truth associated to a fact that cannot be proved in a specific set of axioms… I also believe that in some cases this value is not obtainable in a finite number of trivial computations as done today on those “pseudo-turing-machines”… I really don’t care about the fact that a truth characteristic is not provable in a finite set of operations. This is a very relative concept. First, it is not clear at all that we perform the same “operations” that we code into computers… Ever had an idea? I doubt you can explain operationally how you had it. Of course, if you work in programming most of your ideas are representable with a finite number of operations but that is selection bias. I had lots of ideas that connected different areas of knowledge that I wouldn’t be able to represent in any finite way in the sense of operations etc. However, this is not the main aspect… What I want to say here is that I dislike computers and programming and I am not even remotely interested in having anything to do with that. I also think that we should start focusing more on analytic solutions (whatever analytic may mean in 1000 years from now) instead of performing numerical, finite, perturbative and inexact computer calculations. At least at the level of research of nature…

The Pyramidal effect…

I don’t hate string theorists… I don’t hate string theory either… How could I? I don’t hate aether theories just because they are wrong… String theorists remind me of some presentations made by a funny company working on a pyramidal scheme… The advertisers of that company were honest persons really believing that what they were doing was “honest marketing” and that referring to the “higher hierarchy” was also rather OK when being asked uncomfortable questions… Details were overlooked and well… all the stuff of dishonest marketing was done with the belief that “that’s the way things work” and it is perfectly ok and no problem arises… Of course this was not so and nothing was legal in the way they operated… nor was it moral, honest etc. but the people doing it on the lower ranks believed they were doing a decent and honorable job… String theory is the same… Many people working on it live in the illusion that what they do is honest science… that you can just impose restrictions on reality based on inconsistencies in your theory. That in principle you can send supersymmetric partners to arbitrary high energies and masses without having any problems at all… etc. while having this as the “permanent job”… This is as if you worked for a fraudulent company having a “permanent job”… you might be ignorant and used/abused but still you don’t really do anything relevant except tricking people… Don’t get me wrong: you have to learn multidimensional analysis, algebraic geometry, topology, etc. too in order to do decent QFTs… you need to work with infinite dimensional algebras, etc. So, the basics used in string theory are useful nevertheless… The problem is that string theory “per se” is wrong… while the amount of valid science it incorporates is of course valid and OK… so, if you learn flux compactification you will certainly know how to work with multidimensional calculus in a decent way, which is ok… so, the underlying structures have to be learned… while keeping in mind that string theory is a naive and rather silly generalization to “string” objects that doesn’t solve any problem at all, even worse, it complicates problems and yes, string theory is not correctly quantified nor (as far as I suspect) quantifiable using the current techniques… So, string theory is not a good theory of quantum gravity because 1. It is not good, 2. it is not really quantum and 3. it doesn’t really give any results related to gravity except its existence… which, if I am not wrong, was rather known since ancient times… 

Do I know string theory?

Yes! I worked officially on it 2 years and unofficially another 5 years… I know it inside out and on most of its faces… I even know more about it than some string theorists specialized in, say, flux compactifications, which are in general ignoring other aspects, etc. The thing is, I am also asking some questions when someone tells me something… I generally don’t accept hand-waving arguments so I go home and think carefully about what has been said… sometimes hours, sometimes days, sometimes months… This is how I found out what algebraic topology says about some things related to string theory, this is how I found out how string theory is lacking all forms of unicity proofs… how assumptions are being made on no ground whatsoever… swiss cheese is the thing that resembles most to string theory as it is now… 

Is string theory “the new calculus”?

Well, no… it cannot be… the first calculus I know, defined by Newton and then refined by Leibnitz was rather cumbersome to work with but otherwise well defined… You cannot say the same thing about string theory. Its mathematical foundations are shaky at best and there are consistent imprecisions in the use of terms (to quote a few: flux compactification, compact spaces, string quantization, world sheet integral, perturbative expansion terms, topological series, closing conditions, etc.) In fact I am not sure there is anything well defined in string theory except the idea that there should be strings… While the basic idea of dimensional extension has found some very specific applications (see dimensional regularization, dimensional extension, retraction, etc.) I doubt quite a lot about the “mathematical consistency” of string theory whatsoever… 

The Third Law Of Thermodynamics

I think a good subject for today is the third law of thermodynamics in the context of condensed matter systems and AdS/CFT… 

I think it is widely known that the laws of thermodynamics have their origin in human frustration. That means, after years and years of trying to do something that appeared to be possible people realized it actually cannot be done, either because the scope was mistaken or the mere question being asked had no meaning at all… This is the same for the third law of thermodynamics. In principle it states that via continuous transformations of the state of the system you can get arbitrarily close to absolute 0 in temperature without ever crossing or reaching it. This means that by standard methods of decreasing the temperature you can get close to zero but as you go the difference in entropy becomes so small that you practically get very little decrease in temperature with very much effort… This also can be translated in the fact that at T->0 the difference in entropy goes to 0 or, otherwise stated, all systems condense into a specific state of entropy at absolute zero and that state cannot be reached by any practical means. Whatever the residual entropy is, you cannot reach it in a finite set of steps. For crystal-like objects the end value of the entropy is zero. For glasses it may not be zero but it still remains out of reach due to the difference in entropy being zero on any path going towards T=0

Why am I saying this now? Well, because in string theory the situation is drastically different. String condensates should be considered real and do reach the ground-state which represents a minimum in a set of lots of minima accessible to the system. The minimum of the system is not uniquely defined. In fact it is not defined at all as nobody knows a solution to the “dramatic” string-landscape problem of proliferation.
Now, don’t get me wrong, it’s a very good subject to do research on but the point is to correct the ideas behind string theory and to correct the way string theorists think about nature or about mathematics or both… it simply implies to correct the way string theorists think… but then again, for some unknown reason the situation is a bit the other way around: string theorists don’t really want to learn anything while they want to teach everyone a theory that doesn’t work… that’s a problem… So, stop thinking about string theory as the source of wisdom… it is more likely that non-string people are the source of wisdom for string theorists… it certainly was so in my case…

Holography

I said I am going to discuss today about why the holographic principle is wrong… then I started thinking about it and I observed this could become a rather interesting paper so I decided to keep it for me until it becomes public… ya’ know… being in business it’s not that everything should be public immediately and I do have this VERY bad habit to talk too much serious stuff… I have to train myself in saying nonsense so that a conversation can flow easily without saying anything too relevant… 

Anyways… 

The idea of holography has its origin in the physics of black holes (or at least in what is vaguely understood from the physics of black holes). There are several fundamental paradoxes that appear when putting together Hawking radiation and Einstein-Hilbert Black Holes… I use the name vaguely (you know Hawking and his radiation… maybe you don’t know Einstein and Hilbert but together they form the name for a pretty nice action functional you can write for gravity, although somehow out of fashion nowadays when only wormholes and black holes with alice and bob around are of any measurable sexyness)… However, the idea relates quantum field theories on one side, assumed to describe fields in space-time and to be compatible with special relativity (i.e. local lorentz invariance, LOCAL, ok?) and to derive the interactions between various particles and … no, not gravitation, or at least not directly… in fact it relates this with information, or entropy (lack of information, so to say). What means that? Essentially it means that QFT describes a system made up of some fictional fields that, after applying a specific formalism, can be used to calculate various cross sections and get measurable results… The fields in QFT are NOT observable, or not directly. What you observe in your detector is the result of an interaction of an outgoing particle with your detector… keep this in mind. So, what are the degrees of freedom of QFT? Well, infinity… we have fields… fields are continuous objects in space-time so they have a potentially infinite number of possible excitations… (but the quantum fields in QFT are NOT physical…) 

Now, let’s start exciting these fields and add energy in some region of space (I don’t care if the energy is in form of photons, electrons or whatever, as long as it is energy)… When you do this you may reach an energy in that region of space that ends up collapsing under its own gravity… if you continue exciting the quantum fields you get enough energy there so that a black hole appears… but, if Hawking is right, the entropy of the black hole scales like the area of its horizon. Area of horizon means R^2 and entropy means the logarithm of the number of microstates accessible to the system or the information “lost” or “unaccessible”… So, you get a horizon at the moment when you excite not all the possible states in a volume, but on an area that encompasses the region of space… First conclusion: the information is not encoded in the volume but on an area… 

Ok-ish… now, this is the “state of the art”, vaguely speaking… If you think now as I thought you to think you will see where the difficult spots are in this construction… I won’t say anything else…

 

 

Why is the holographic principle wrong?

Today I am a tiny bit more ambitious but with less time in the morning: Why is AdS/CFT wrong or at least incompatible with any practical situation I already explained… But what about the basics of it? The Holographic principle? Defended by almost all the “great physicists” today? The task of explaining this might look as impossible so I’ll have to take the whole evening today to do it… 🙂