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Προβολή αναρτήσεων από 2013

On the Computing Spacetime

Fotini Markopoulou has published a paper entitled The Computing Spacetime. The first sentence of this paper is: That the Universe can be thought of as a giant computation is a straightforward corollary of the existence of a universal Turing machine. This is a very bold statement, to say the least. We have absolutely no idea what are the (ultimate) laws of the universe and yet we can immediately prove that it is a gigantic computer! Now let's see the proof:
The laws of physics allow for a machine, the universal Turing machine, such that its possible motions correspond to all possible motions of all possible physical objects. That is, a universal quantum computer can simulate every physical entity and its behavior. This means that physics, the study of all possible physical systems, is isomorphic to the study of all programs that could run on a universal quantum computer. We can think of our universe as software running on a universal computer. First let me remark that Markopoulou …

Fairytale Physics

Jim Baggot in his recent book that is entitled Farewell to Reality: How Fairytale Physics Betrays the Search for Scientific Truth  advocates the idea that modern physics is going in the wrong direction. In particular, he critically examines superstring theory and concludes that this theory cannot explain the existence of many things we know they exist! Similar ideas have been presented in Peter Woit's Not Even Wrong: The Failure of String Theory and the Continuing Challenge to Unify the Laws of Physics. Recently, the British newspaper The Guardian has published as debate between Baggot and string theorist Mike Duff. The later replied to Baggot's remark that "the positron was discovered in cosmic ray experiments just a couple of years after Dirac had agreed that this was what his theory predicted" as follows:
Dirac did not assume the positron; he discovered it to be a consequence of an equation that described the well-established electron. Similarly, string theor…

New book on the Theory of Fuzzy Computation

Εικόνα
I am really happy to announce the publication of my book on the theory of fuzzy computation. The book is available as an eBook and as a hardback. Readers can freely read the preface and the book's table of contents.

On Computation

In an old entry of this blog, I had criticised a blog post who was a review of my book. The author of that review posted a new post entitled Deflating Hypercomputation, where he advertizes his paper The Physical Church–Turing Thesis: Modest or Bold? This paper is a defense of a "modest version of the Physical Church-Turing thesis":
Any function that is physically computable is  Turing computable. The next question is, of course, what is meant by physical computable? Gualtiero Piccinini, that is, the author of this paper, proposes that "if a physical process is a computation, it can be used by a finite observer to obtain the desired values of a function". Now, finite observers are "human beings and any other intelligent beings of similarly bounded capacities". In an explanation of this description, he includes among observers beings that are located in spacetimes that are (currently?) inaccessible to humans (so hypercomputation near a black hole is not a …

A quantum computer for everyone!

People who would like to run programs for quantum computers have now the chance to use a real conventional quantum computer! Just point your browser to the Qcloud! This is a service offered by the School of Physics of the University of Bristol, UK.

Infinite computations with random oracles

Merlin Carl and Philipp Schlicht have posted an article to the arXiv entitled infinite computations with random oracles. A basic result of classical computability theory states that if a real x is Turing-computable relative to all oracles in a set of positive measure, then this real number is Turing-computable in the empty oracle. In different words,  the use of random generators does not enrich the set of computable functions. The authors examine whether this is true for models of infinite computation. In particular, for Infinite Time Turing Machine, Infinite Time Register machines, α-Turing machines, and ordinal Turing/register machines, the authors ask whether there are noncomputable reals (in the sense of the machine type) that are reducible to all oracles in a set of positive measure. The authors show that the answer is negative for most models of infinite computation.

Quantum Computing and… Democritus

Yesterday I noticed that there is a new book entitled Quantum Computing since Democritus. I haven't read the book but from what I have seen, it seems that it is a presentation of the field of quantum computing in a colloquial language (Democritus is called a dude!). What is really interesting is one of the reviews posted at amazon's web page. The review is by some one called Guy Wilson but it seems that Guy Wilson is actually Joy Christian. Christian does not really believe that it will possible to build scalable quantum computers.

First of all, it is true that one cannot go to a computer shop and buy a quantum computer today, but this does not mean that there are no quantum computers. For example, Google bought a quantum computer recently. But Christian argues that he has disprovedBell's theorem, which, roughly speaking, implies that it is not possible to build scalable quantum computers.

Unfortunately, in a way the situation looks familiar–just because someone has bui…

Creating a Mind

Recently, I read a review by Colin McGinn of Ray Kurzweil'sHow to Create a Mind: The Secret of Human Thought Revealed. According to McGinn, the book reveals, at last, the secret of human thought which is pattern recognition! Kurzweil argues that one needs to build a machine that recognizes patterns in order to create a mind. Personally, I find this idea extremely naive because pattern recognition is just one of mind's many functions. On the other side, McGinn says that "the brain is causally connected to the mind and the mind contains and processes information", which seems bizarre. I always thought that the brain induces the mind but this statement implies that the brain and the mind are two separate entities. What is even more bizarre are reviews of the book like this:

Ray Kurzweil's understanding of the brain and artificial intelligence will dramatically impact every aspect of our lives, every industry on Earth, and how we think about our future. If you car…

Oracle Machines and the Verification Problem

Florent Franchette presented an interesting problem in his "Oracle Hypermachines Faced with the Verification Problem". Franchette argues that a physical oracle machine cannot be used to prove that physical hypercomputers exist simply because we cannot verify the results computed by the machine. However, an answer to what can be computed by a form of oracle Turing machine is described in "Computational complexity with experiments as oracles" (see also "Computational complexity with experiments as oracles. II. Upper bounds"). Roughly, their oracle machine, which is called an analog-digital Turing machine, is an ordinary Turing machine coupled to an abstract physical experiment. The authors of these papers prove that this machines have computational power that goes beyond the Church-Turing barrier. Now, if one proves that a machine is actually a hypercomputer, then I think there is no need to verify results computed. After all, we trust the results computed…

Can we predict the future?

It seems that some Mathematicians Predict the Future With Data From the Past. Whether this is possible or not is a big question. If we live in a deterministic universe, then it might be possible to predict things. However, I have to do some homework first in order to have a clear view of things...

Design Considerations for Faster-Than-Light (FTL) Communication

On April the 1rst the following request for comments was submitted

Design Considerations for Faster-Than-Light (FTL) Communication 
OK this is a joke but I wonder whether it would really make any sense to think seriously about such a thing?

There is nothing wrong with particles that travel faster than the light!

Judit  Madarász and Gergely Székely, in a paper that was recently posted to the arXiv and which is entitled The Existence of Superluminal Particles is Consistent with Relativistic Dynamics, examine whether particles that are supposed to travel faster than the light violate any physical law. Their conclusion is that the existence of particles that travel faster than the light cannot be ruled out by special relativity.

Non-Universality in Computation

Selim Akl has convincingly argued that there is no universal computer. This may come to a surprise to people since one of the first things we learn when studying computability theory is the notion of the universal Turing machine. But then again, we learn that there is a thesis that dictates what and what cannot be computed!